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1
Wan, Chenchen. "Optical Tweezers Using Cylindrical Vector Beams". University of Dayton / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1353515022.
2
Bolsa, Ferruz Marta. "Oxygen effect in medical ion beam radiation combined with nanoparticles". Thesis, Université Paris-Saclay (ComUE), 2017. http://www.theses.fr/2017SACLS476/document.
Abstract (sommario):
Environ 50% des patients recevant un traitement contre le cancer bénéficient de la radiothérapie. La radiothérapie conventionnelle consiste à utiliser des rayons X de haute énergie capables de traverser les tissus et de traiter des tumeurs situées en profondeur de façon non-invasive. Malheureusement, les rayons X ne font pas la distinction entre les tumeurs et les tissus sains, qui peuvent donc être endommagés. Cette non-sélectivité est à l’origine de graves effets secondaires, voire du développement de cancers secondaires. Par conséquent, l’amplification des effets radiatifs au sein de la tumeur par rapport aux tissus environnants représente un défi majeur.L’hadronthérapie (traitement par faisceaux de protons ou d’ions carbone) est considérée comme l’une des techniques les plus prometteuses car, contrairement aux rayons X, la quantité d’énergie déposée atteint son maximum en fin de trajectoire. Lorsque le faisceau est réglé de manière à ce que ce maximum atteigne la tumeur, aucun dommage n’est causé aux tissus situés au-delà. Un autre avantage majeur est que les ions lourds sont plus efficaces pour traiter les tumeurs radiorésistantes. L’utilisation de cette technique est cependant restreinte du fait des dommages – plus faibles mais néanmoins significatifs – causés aux tissus normaux situés sur la trajectoire du faisceau d’ions en amont de la tumeur. Afin d’améliorer les performances de l’hadronthérapie, l’équipe a développé à l’ISMO une nouvelle stratégie combinant l’utilisation de nanoparticules (NPs) métalliques avec l’irradiation par faisceaux d’ions. L’utilisation de NPs a pour but non seulement d’amplifier les effets des rayonnements dans la tumeur mais également d’améliorer l'imagerie médicale à l’aide des mêmes agents (théranostic). Les NPs possèdent une chimie de surface permettant leur fonctionnalisation avec des ligands capable d’améliorer la biocompatibilité, la stabilité ainsi que la circulation sanguine et l’accumulation dans la tumeur. L’équipe a déjà démontré que les petites NPs d’or et de platine (≈ 3 nm) avaient la capacité d’amplifier les effets causés par les faisceaux d’ions carbone médicaux en présence d’oxygène. Cependant, les tumeurs radiorésistantes sont susceptibles de contenir des régions hypoxiques. Il est donc urgent de quantifier et de caractériser l’influence de l’oxygène sur l’effet radio-amplificateur. Le but de ma thèse était d’étudier l’influence de l’oxygène lors d’irradiations par des faisceaux d’ions médicaux en présence de NPs d’or et de platine. Pour cela, deux lignes de cellules cancéreuses humaines radiorésistantes ont été testées: HeLa (col de l’utérus) et BxPC-3 (pancréas). Plusieurs techniques d’irradiation ont été utilisées : des faisceaux d’ions carbone et hélium générés par « passive scattering » et des faisceaux d’ions carbone générés par « pencil beam scanning ». Les principaux résultats de cette étude sont les suivants. En condition oxique (concentration d’O₂ = 20%), une amplification des effets radiatifs a été observée pour les deux types de NPs (à concentration de métal égale). Ce phénomène se réduit à mesure que la concentration d’oxygène diminue mais reste significatif jusqu’à 0.5%. Aucune différence significative n’a été observée entre les deux lignes cellulaires. Il est intéressant de noter que la dépendance à l’oxygène varie en fonction de la technique d’irradiation utilisée. Une tentative d’explication de l’influence de l’oxygène par des processus moléculaires est proposée. Des perspectives de développements ultérieurs sont suggéréesAbout 50% of the cancer patients who are treated benefit from radiation therapy. Conventional radiotherapy consists of high energy X-rays traveling through the tissues, so that deeply sited tumors are treated in a non-invasive way. Unfortunately, X-rays are not tumor selective and healthy tissues may be damaged. This lack of selectivity is responsible for severe side effects and/or secondary cancers. Hence, improving the differential of radiation effects between the tumor and surrounding tissues remains a major challenge. Particle therapy (treatment by protons or carbon ion beams) is considered as one of the most promising technique because, by opposition to X-rays, the energy deposition of ions is maximum at the end of their tracks. When the beam is tuned so that the maximum reaches the tumor, there is no damage induced in tissues siting after the tumor. Another important added value is that heavy ions are more efficient to treat radioresistant tumors. The use of this modality is however restricted by the low but significant damage that is induced to normal tissues located at the entrance of the track prior to reaching the tumor. To improve the performance of particle therapy, a new strategy based on the combination of high-Z nanoparticles with ion beam radiation has been developed by the group at ISMO. This approach aims at using nano-agents not only to increase radiation effects in the tumor but also to improve medical imaging with the same agent (theranostic). Nanoparticles present a remarkable surface chemistry, which allows functionalization with ligands able to improve biocompatibility, stability as well as blood circulation and accumulation in tumors. The group already demonstrated the efficiency of small (≈ 3 nm) gold and platinum nanoparticles to amplify the effects of medical carbon ions in normoxic conditions (in the presence of oxygen). However, radioresistant tumors may host hypoxic regions. It is thus urgent to quantify and characterize the influence of oxygen on the radio-enhancement effect. The goal of my thesis was to study the influence of oxygen on medical ion radiation effects in the presence of gold and platinum nanoparticles. This was performed using two radioresistant human cancer cell lines: HeLa (uterine cervix) and BxPC-3 (pancreas). Different radiation modalities were used: carbon and helium ion beams delivered by a passive scattering delivery system and carbon ion beams delivered by a pencil beam scanning system. The major results of this work are the following. In oxic conditions (O₂ concentration = 20%), an enhancement of ion radiation effects was observed for the two nanoparticles (at the same concentration in metal). This effect decreased with the oxygen concentration but remained significant for a concentration of 0.5%. No significant difference was found between the cell lines. Interestingly, the oxygen-dependence varied with the type of radiation. An attempt to explain the effect of oxygen by molecular processes is proposed. Perspectives of further developments are suggested
3
Tabor, Christopher Eugene. "Some optical and catalytic properties of metal nanoparticles". Diss., Atlanta, Ga. : Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/31794.
Abstract (sommario):
Thesis (Ph.D)--Chemistry and Biochemistry, Georgia Institute of Technology, 2010.Committee Chair: El-Sayed, Mostafa; Committee Member: Perry, Joseph; Committee Member: Wang, Zhong; Committee Member: Whetten, Robert; Committee Member: Zhang, John. Part of the SMARTech Electronic Thesis and Dissertation Collection.
4
Powell, Tremaine Bennett. "The Use of Nanoparticles on Nanometer Patterns for Protein Identification". Diss., The University of Arizona, 2008. http://hdl.handle.net/10150/194368.
Abstract (sommario):
This dissertation describes the development of a new method for increasing the resolution of the current protein microarray technology, down to the single molecule detection level. By using a technique called size-dependent self-assembly, different proteins can be bound to different sized fluorescent nanostructures, and then located on a patterned silicon substrate based on the sized pattern which is closest to the size of the bead diameter.The protein nanoarray was used to detect antibody-antigen binding, specifically anti-mouse IgG binding to mouse IgG. The protein nanoarray is designed with the goal of analyzing rare proteins. However, common proteins, such as IgG, are used in the initial testing of the array functionality. Mouse IgG, representing rare proteins, is conjugated to fluorescent beads and the beads are immobilized on a patterned silicon surface. Then anti-mouse IgG binds to the mouse IgG on the immobilized beads. The binding of the antibody, anti-mouse IgG, to the antigen, mouse IgG is determined by fluorescent signal attenuation.The first objective was to bind charged nanoparticles, conjugated with proteins, to an oppositely charged silicon substrate. Binding of negatively charged gold nanoparticles (AuNP), conjugated with mouse IgG, to a positively charged silicon surface was successful.The second objective was to demonstrate the method of size-dependent self-assembly at the nanometer scale (<100 >nm). Different-sized, carboxylated, fluorescent beads and AuNP, which were conjugated with proteins, were serially added to a patterned polymethyl methacrylate (PMMA) coated silicon surface. Size-dependent self-assembly was successfully demonstrated, down to the nanometer scale.The final objective was to obtain a signal from antibody-antigen binding within the protein array. Conjugated fluorescent beads were bound to e-beam patterns and signal attenuation was measured when the antibodies bound to the conjugated beads. The size-dependent self-assembly is a valuable new method that can be used for the detection and quantification of proteins.
5
Arribard, Yann. "Analyse de matière extraterrestre primitive par imagerie hyperspectrale infrarouge et spectrométrie de masse TOF-SIMS". Electronic Thesis or Diss., université Paris-Saclay, 2023. http://www.theses.fr/2023UPASP005.
Abstract (sommario):
La matière extraterrestre dite primitive se caractérise par sa faible évolution chimique depuis sa formation. Elle se retrouve notamment comme un des constituants des fragments de petits corps du système Solaire, tels que les astéroïdes. L'étude d'échantillons en provenance de ces corps peut ainsi permettre de mieux comprendre son origine et son évolution.Dans cette thèse, mon travail s'est orienté autour de l'analyse de la matière primitive et plus particulièrement sur l'étude des chondrites carbonées ayant subi de l'altération aqueuse. La première partie de ma thèse s'oriente sur l'analyse des phases minérales et organiques au sein de chondrites CM de type pétrologique 2 grâce à des techniques de spectroscopie infrarouge et Raman ainsi que de la spectrométrie de masse à ionisation secondaire par temps de vol (TOF-SIMS). Ces techniques bénéficient d'une bonne complémentarité dans la caractérisation des différentes phases qui nous intéressent. Elles sont également couplées à l'imagerie, ce qui permet d'étudier le lien qu'il peut exister entre les différentes phases minérales et organiques. J'ai utilisé un nouveau processus non supervisé d'analyse des données hyperspectrales infrarouge, ce qui a permis de déterminer des paramètres spectraux caractérisant l'état d'avancement de l'altération aqueuse des échantillons, notamment de leur phase minérale, tout en les reliant à leur évolution chimique. La spectroscopie Raman a permis de mettre en évidence des différences de structure de la matière organique poly-aromatique au sein des différents échantillons. Enfin, le TOF-SIMS a également mis en évidence une différence de structure de la matière organique tout en confirmant et précisant les différences de co-localisation entre matière organique et phase minérale observées par l'imagerie hyperspectrale entre les échantillons.La seconde partie de ma thèse s'est orientée sur l'étude d'efficacité d'un nouvel accélérateur linéaire - Andromede (IJCLab) - comme source primaire pour le TOF-SIMS sur des analogues à la matière primitive des chondrites. J'ai produit ces analogues organiques en laboratoire afin de simuler la matière organique insoluble, la part majoritaire de la matière organique des chondrites. J'ai contrôlé les caractéristiques de ces analogues par des spectroscopies infrarouges, à rayon X et par TOF-SIMS. Ils demeurent différents de la matière organique des CM en termes de structure poly-aromatique, mais similaires en termes de composition élémentaire et caractère insoluble. J'ai produit des analogues minéraux à partir de roches terrestres similaires aux minéraux rencontrés dans les CM. Les mesures que j'ai réalisées sur ces analogues et sur des chondrites montrent à la fois le potentiel et les limites actuelles du TOF-SIMS couplé à Andromède, et suggèrent des pistes d'amélioration en vue d'en augmenter, notamment, la résolution en masseSo-called primitive extraterrestrial matter is characterized by its low chemical evolution since its formation. It is found in particular as one of the constituents of the fragments of small bodies of the Solar system, such as asteroids. The study of samples from these bodies can thus make it possible to better understand its origin and its evolution.In this thesis, my work focused on the analysis of primitive matter and more particularly on the study of carbonaceous chondrites having undergone aqueous alteration. The first part of my thesis focuses on the analysis of mineral and organic phases within petrological type 2 CM chondrites using infrared and Raman spectroscopy techniques as well as time-of-flight secondary ionization mass spectrometry. (TOF-SIMS). These techniques benefit from a good complementarity in the characterization of the different phases that interest us. They are also coupled with imagery, which makes it possible to study the link that may exist between the different mineral and organic phases. I used a new unsupervised process for analyzing infrared hyperspectral data, which made it possible to determine spectral parameters characterizing the state of progress of the aqueous alteration of the samples, in particular of their mineral phase, while relating to their chemical evolution. Raman spectroscopy made it possible to highlight differences in the structure of the polyaromatic organic matter within the different samples. Finally, the TOF-SIMS also highlighted a difference in the structure of the organic matter while confirming and clarifying the differences in co-localization between organic matter and mineral phase observed by hyperspectral imaging between the samples.The second part of my thesis focused on the study of the effectiveness of a new linear accelerator - Andromeda (IJCLab) - as a primary source for TOF-SIMS on analogues of primitive chondrite matter. I produced these organic analogues in the laboratory to simulate insoluble organic matter, the majority of organic matter in chondrites. I checked the characteristics of these analogues by infrared spectroscopy, X-ray spectroscopy and TOF-SIMS. They remain different from CM organic matter in terms of poly-aromatic structure, but similar in terms of elemental composition and insoluble character. I have produced mineral analogues from earth rocks similar to minerals found in CM chondrite. The measurements that I carried out on these analogues and on chondrites show both the potential and the current limits of TOF-SIMS coupled to Andromede, and suggest areas for improvement with a view to increasing, in particular, the masse resolution
6
Do, Jaekwon. "Controlled spatial arrangement of gold nanoparticles using focused laser beams and DNA origami". Diss., Ludwig-Maximilians-Universität München, 2014. http://nbn-resolving.de/urn:nbn:de:bvb:19-171381.
7
Krishnappa, Arjun. "Optical Steering of Microbubbles for Nanoparticle Transport". University of Dayton / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1469461239.
8
Kong, David Sun 1979. "Nanostructure fabrication by electron and ion beam patterning of nanoparticles". Thesis, Massachusetts Institute of Technology, 2004. http://hdl.handle.net/1721.1/28346.
Abstract (sommario):
Thesis (S.M.)--Massachusetts Institute of Technology, School of Architecture and Planning, Program in Media Arts and Sciences, 2004.Includes bibliographical references (leaves 82-83).
Two modes of energetic beam-mediated fabrication have been investigated, namely focused ion beam (FIB) direct-writing of nanoparticles, and a technique for electrostatically patterning ionized inorganic nanoparticles, termed nanoxerography. A FIB has been used to directly pattern thin films of organometallic Ag-precursors down to a resolution of 100 nm. The sensitivity of the resist to 30 keV Ga+ ions was measured to be approximately 5 C/cm2. Using this technique arbitrary structures were fabricated in two and three dimensions with resistivity on the order of 1x10 4 Q-cm and 1x1 0-5 Q-cm for single- and multi-layer structures, respectively. A new unit of merit for characterizing direct-write processes, termed resistivity-dose (Q-jC/cm), has been introduced. A Nanocluster Source capable of generating a beam of charged, inorganic nanoparticles has been characterized. The relationship between power supplied to the magnetron of the source and the size of deposited clusters has been plotted. Techniques for utilizing such clusters to develop latent electrified images patterned by an electron beam (EB) have been proposed. The charge-storing characteristics of a variety of substrates such as mylar and polyimide were studied by developing EB-patterned charge images with toner particles.
David Sun Kong.
S.M.
9
MELONI, MARIA CRISTINA. "Preparazione e caratterizzazione di due sistemi carrier: beads a base di chitosano e chitosano/alginato; nanoparticelle di N-trimetilchitosano". Doctoral thesis, Università degli Studi di Cagliari, 2012. http://hdl.handle.net/11584/266151.
Abstract (sommario):
Chitosan is a very attractive polysaccharide and it is known to be a favorable pharmaceutical material because of its low toxicity, biodegradability, biocompatibility,
mucoadhesivity and natural origin. Therefore it forms an ideal hydrophilic carrier system. In this study we described the preparation and characterization of two carrier systems, chitosan and chitosan – alginate beads, and N-Trimethyl Chitosan (TMC) chloride nanoparticles.
We realized spherical beads using different polymeric dispersions, chitosan, alginate and chitosan - alginate mixture, to investigate their effect on the phytoterapic anti- inflammatory agent delivery. The main purpose of the present in vitro study is to have some information about their stability in the gastrointestinal tract and to formulate a drug delivery system for the oral administration of this phytoterapic agent. Alginate
beads were prepared by ionotropic gelation in presence of CaCl2 and BaCl2 solutions; chitosan beads were prepared by using a TPP (tripolyphosphate) solution as an ionic
cross-linking agent and acetone as a coacervating agent; beads of chitosan - alginate mixture were prepared according to the two combined procedures reported above.
The swelling degradation behaviour of the bead samples and drug release were investigated using four different medium solutions (PBS pH 7.4, HCl 0.1N pH 1, buffer pH 5). TMC with different degrees of quaternization were synthesized and characterized by 1 H- NMR spectroscopy, XRD and viscosity. Trimethyl Chitosan chloride nanoparticles (TMC-NPs) were prepared according to the ionotropic gelation process of TMC with TPP. The aim of this study is to characterized TMC-NPs (particle size -Z-average mean-, PDI and zeta potential) and evaluate their potential for brain delivery.
10
Tijiwa, Birk Felipe. "Spin electronics in metallic nanoparticles". Diss., Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/39525.
Abstract (sommario):
The work presented in this thesis shows how tunneling spectroscopy techniques can be applied to metallic nanoparticles to obtain useful information about fundamental physical processes in nanoscopic length scales. At low temperatures, the discrete character of the energy spectrum of these particles, allows the study of spin-polarized current via resolved "electron-in-a-box" energy levels. In samples consisting of two ferromagnetic electrodes tunnel coupled to single aluminum nanoparticles, spin accumulation mechanisms are responsible for the observed spin-polarized current. The observed effect of an applied perpendicular magnetic field, relative to the magnetization orientation of the electrodes, indicates the suppression of spin precession in such small particles. More generally, in the presence of an external non-collinear magnetic field, it is the local field "felt" by the particle that determines the character of the tunnel current. This effect is also observed in the case where only one of the electrodes is ferromagnetic. In contrast to the non-magnetic case, ferromagnetic nanoparticles exhibit a much more complex energy spectrum, which cannot be accounted for, using the simple free-electron picture. It will be shown that interactions between quasi-particle excitations due to sequential electron tunneling and spin excitations in the particle are likely to play an important role in the observed temperature/voltage dependence of magnetic hysteresis loops.
11
Dorn, Marco. "Nachweis und Quantifizierung von Nanopartikeln". Doctoral thesis, Universitätsbibliothek Leipzig, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-162158.
Abstract (sommario):
Die Nanotechnologie spielt eine Schlüsselrolle bei der technologischen Entwicklung. Jedoch stellen Nanopartikel ein potentielles Gesundheitsrisiko dar. Durch ihre große Oberfläche zeigen Nanopartikel eine hohe Reaktivität und die geringe Größe trägt zu einer erhöhten Beweglichkeit und Bioverfügbarkeit bei. Beispielsweise können Nanopartikel Entzündungen auslösen oder die Produktion von freien Radikalen fördern. Insbesondere Lungenepithelzellen stellen die wichtigste Barriere zur Aufnahme von industriell relevanten Nanopartikeln im Alltag dar, denn durch ihre geringe Größe können Nanopartikel bis in einzelne Alveolen vordringen und in die Blutbahn gelangen. Aus diesen Gründen ist es notwendig das Risikopotential, was von Nanopartikeln ausgeht zu bewerten. In dieser Dissertation wurden die Metalloxid-Nanopartikel Al2O3, TiO2, Fe2O3, ZnO und CeO2 in einzelnen Lungenzellen erstmals mit Hilfe der Ionenstrahlmikroskopie quantifiziert. Darüber hinaus erfolgte die Quantifizierung von ausgewählten Metalloxid-Nanopartikeln in gedehnten primären Typ 2 Pneumozyten sowie in den Alveolen des Lungengewebes. Außerdem wurden Gold und Silber als Markierungspartikel eingesetzt, um die Aufnahme der organischen Nanopartikel Graphen zu untersuchen. Die Ionenstrahlmikroskopie ist eine hochempfindliche Methode, welche durch die charakteristische Röntgenstrahlung den zellulären Elementgehalt innerhalb einer Zelle visualisieren kann. Dies ist, je nach Element, bis zu einer unteren Konzentrationsgrenze von 5 – 20 ppm möglich. Die Ionenstrahlmikroskopie erlaubt, im Vergleich zur Elektronenstrahlmikroanalyse, biologische Proben bis zu einer Tiefe von ca. 80 µm zu untersuchen. Durch das zelluläre Rückstreusignal konnte bei Kulturzellen entschieden werden, ob die Nanopartikel internalisiert wurden oder auf der Zelloberfläche assoziiert sind. Da biologische Proben eine relativ geringe Dichte und Dicke aufweisen, ist die Signalausbeute und damit die Messzeit ein limitierender Faktor bei der ionenstrahlanalytischen Quantifizierung des Elementgehalts. Durch das Aufziehen der Probe auf einen Aluminiumrahmen, konnte der Abstand zwischen Röntgendetektor und Probe reduziert werden, was zu einer höheren Signalausbeute führte und damit eine schnellere Analyse der Präparate ermöglichte. Die Art und Weise der Probenpräparation kann einen Einfluss auf den zellulären Elementgehalt haben, indem Ionen aus dem Medium an die Zellaußenseite binden oder durch die Waschlösung ein Verlust von intrazellulär lokalisierten organischen und anorganischen Molekülen entsteht. Durch den Vergleich zwischen einer ionenfreien Polyethylenglycol-Lösung mit dem üblicherweise verwendeten Waschpuffer konnte gezeigt werden, dass sich bei der Verwendung des Waschpuffers der zelluläre Elementgehalt von Kalium, Kalzium und insbesondere Chlor erhöht. Allerdings bleiben Phosphor und Schwefel als wichtige zelluläre Strukturelemente und die biologisch relevanten Spurenelemente Eisen und Zink davon unbeeinflusst. Die ionenstrahlmikroskopische Analyse von Lungengewebe erfordert eine Einbettung der Präparate. Dabei erwies sich DePeX, was als Material routinemäßig zur Einbettung verwendet wird, als ungeeignet, da eine inhomogene Zink-Kontamination vorhanden war, welche eine intrazelluläre Zink-Messung verhinderte. Durch die Entwicklung eines neuen zinkfreien Einbettmaterials auf Limonen-Basis, konnte jetzt auch die Zinkkonzentration in Alveolen gemessen werden. Im biologischen Millieu können Proteine und Ionen auf der Oberfläche der Nanopartikel adsorbieren und dadurch deren Aufnahme in die Zelle beeinflussen. Deshalb wurde die zelluläre Aufnahme in Abhängigkeit der Proteinhülle (Korona) bei in vitro Bedingungen untersucht. Tragen die Partikel eine Korona, ist bei allen untersuchten Metalloxid-Nanopartikeln eine geringere zelluläre Konzentration zu beobachten und gleichzeitig sind weniger Nanopartikel auf der Zelloberfläche adsorbiert. Die Aufnahme von CeO2 und ZnO wurde näher untersucht, da ZnO als einziger untersuchter Nanopartikel einen deutlichen toxischen Effekt hervorruft und CeO2 durch die hohe Ausbeute des Rückstreusignals und die starke zelluläre Aufnahme zum näheren Studium der Aufnahme besonders geeignet ist. Es wurde beobachtet, dass CeO2 und ZnO im extrazellulären Raum mit Phosphat und Kalzium aus dem Kulturmedium kolokalisiert sind. Da Kalziumphosphat als Transfektionsagenz bekannt ist, kann diese Modifikation der Partikeloberfläche die Aufnahme der Partikel begünstigen. Im Vergleich zu CeO2, ist bei ZnO auf Grund der erhöhten Toxizität keine Sättigung der zellulären Konzentration zu erkennen. Daneben lässt die die Halbierung der zellulären CeO2-Konzentration nach 72 Stunden Applikationszeit darauf schließen, dass die Zellen in der Lage sind die Nanopartikel durch Exozytose wieder abzugeben. Mit Hilfe von Inhibitoren wurde der Aufnahmemechanismus von CeO2-NP untersucht. Dabei zeigte sich, dass CeO2 Nanopartikel durch Caveolae- bzw. Clathrin-vermittelte Endozytose und Makropinozytose aufgenommen werden. Die Internalisierung von CeO2 und ZnO Nanopartikeln wurde mit Hilfe des zellulären Protonen-Rückstreusignals untersucht. Internalisierte Nanopartikel liefern im Vergleich zu extrazellulär assoziierten Nanopartikeln ein Rückstreusignal bei niedrigeren Energien, da die zurückgestreuten Protonen durch die Passage des Zellmaterials zusätzlich Energie verlieren. Bei diesen Untersuchungen wurde festgestellt dass, ZnO und CeO2-Nanopartikel ohne Proteinhülle häufiger an der Zelloberfläche lokalisiert sind und zu einer höheren zellulären Konzentration führen. Sowohl im Lungengewebe als auch bei gedehnten primären Typ 2 Pneumozyten und kultivierten Lungenepithelzellen zeigte sich eine sehr inhomogene zelluläre Konzentrationsverteilung der Nanopartikel. Hier liegt die Stärke der Ionenstrahlmikroskopie darin, die Konzentration in einzelnen Zellen bzw. Alveolen erfassen zu können. Dadurch erlaubt es diese Methode, das Risiko abzuschätzen, was durch die Extrembelastung in einzelnen Zellen entstehen könnte. Da Lungengewebe aus Typ I und Typ II Pneumozyten besteht und Makrophagen in das Gewebe einwandern können, ist es in zukünftigen Experimenten notwendig die einzelnen Zelltypen zu markieren, um die Nanopartikel-Aufnahme im Lungengewebe mit den Ergebnissen der Zellkultur besser vergleichen zu können. Durch eine Markierung mit Gold-konjugierten Antikörpern, kann erreicht werden, die einzelnen Zelltypen mittels Ionenstrahlmikroskopie zu identifizieren. Durch verschiedene Applikationsformen bei in vitro und in vivo Untersuchungen ist die Wirkung der Nanopartikel nur schwer vergleichbar. Aus diesem Grund wurde in dieser Arbeit das Konzept der effektiv wirksamen zellulären Dosis eingeführt. Dieses erlaubt es, der Dosis, welche tatsächlich zellulär oder im Gewebe vorhanden ist, einen toxischen Effekt der Nanopartikel zuzuordnen. Dadurch kann die effektive Dosis als wichtige Größe zum systematischen Vergleich von toxikologischen Studien auf in vitro und in vivo Basis eingesetzt werden. Die Ionenstrahlmikroskopie ist zur Zeit die einzige Methode, welche für die intrazelluläre Quantifizierung von unmarkierten Nanopartikeln auf Einzelzellebene in Frage kommt. Deshalb ist sie als zukünftige Referenzmethode für die Dosimetrie von Nanopartikeln sehr gut geeignet.
12
Guler, Urcan. "Localized Surface Plasmons In Metal Nanoparticles Engineered By Electron Beam Lithography". Master's thesis, METU, 2009. http://etd.lib.metu.edu.tr/upload/3/12610934/index.pdf.
Abstract (sommario):
In this study, optical behavior of metal nanoparticles having dimensions smaller
than the wavelength of visible light is studied experimentally and numerically.
Gold (Au) and silver (Ag) nanoparticles are studied due to their superior optical
properties when compared to other metals. A compact code based on Discrete
Dipole Approximation (DDA) is developed to compute extinction efficiencies of
nanoparticles with various different properties such as material, dimension and
geometry. To obtain self consistent nanoparticle arrays with well defined
geometries and dimensions, Electron Beam Lithography (EBL) technique is
mainly used as the manufacturing method. Dose parameters required to produce
nanoparticles with dimensions down to 50 nm over substrates with different
electrical conductivities are determined. Beam current is found to affect the doseV
size relation. The use of thin Au films as antistatic layer for e-beam patterning
over insulating substrates is considered and production steps, involving
instabilities due to contaminants introduced to the system during additional
removal steps, are clarified. 4 nm thick Au layer is found to provide sufficient
conductivity for e-beam patterning over insulating substrates. An optical setup
capable of performing transmittance and reflectance measurements of samples
having small areas patterned with EBL is designed. Sizes of the metal
nanoparticles are determined by scanning electron microscope (SEM) and spectral
data obtained using the optical setup is analyzed to find out the parameters
affecting the localized surface plasmon resonances (LSPR). Arrays of particles
with diameters between 50 &ndash200 nm are produced and optically analyzed. Size and shape of the nanoparticles are found to affect the resonance behavior. Furthermore, lattice constants of the particle arrays and surrounding medium are also shown to influence the reflectance spectra. Axes with different lengths in ellipsoidal nanoparticles are observed to cause distinguishable resonance peaks when illuminated with polarized light. Peak intensities obtained from both polarizations are observed to decrease under unpolarized illumination. Binary systems consisting of nanosized particles and holes provided better contrast for transmitted light.
13
Meader, Victoria K. "Metal Nanoparticle Synthesis by Photochemical Reduction with a High-Intensity Focused Laser Beam". VCU Scholars Compass, 2019. https://scholarscompass.vcu.edu/etd/6001.
Abstract (sommario):
Colloidal, metallic nanoparticles have myriad applications, but they are most ideal when they are monodisperse, and demonstrate maximum catalytic utility when they are small (< 5 nm) and uncoated; because their surface area is accessible and maximized. Laser- assisted metal nanoparticle synthesis is a ‘green’ method that has become a topic of active research because it is able to produce uncoated or ‘naked’ products. The nanoparticles synthesized in this work were formed through the reduction of metal salts in aqueous solutions; but the reducing agent is an electron-dense microplasma generated by the laser pulse interacting with the media. Because no chemical reducing agents or stabilizers are needed, the products have no surfactants.
The underlying reaction mechanisms that drive this type of synthesis are generally understood, however, there is insufficient detail that would allow control over the formation of ultimate product morphologies and size distributions. The metals examined in this thesis are: gold, whose formation follows an autocatalytic rate law; and silver, whose formation follows a first-order rate law. Through my research, I was able to explore the effects that physical parameters (such as laser pulse settings) and chemical parameters (such as radical scavenger addition) have on laser-assisted gold or silver nanoparticle synthesis. My research, outlined in this thesis, is therefore focused on elucidating such details and distilling them into methods of control in order to better predict and tune nanoparticle products.
14
Near, Rachel Deanne. "Theoretical and experimental investigation of the plasmonic properties of noble metal nanoparticles". Diss., Georgia Institute of Technology, 2013. http://hdl.handle.net/1853/52181.
Abstract (sommario):
Noble metal nanoparticles are of great interest due to their tunable optical and radiative properties. The specific wavelength of light at which the localized surface plasmon resonance occurs is dependent upon the shape, size and composition of the particle as well as the dielectric constant of the host medium. Thus, the optical properties of noble metal nanoparticles can be systematically tuned by altering these specific parameters. The purpose of this thesis is to investigate some of these properties related to metallic nanoparticles. The first several chapters focus on theoretical modeling to predict and explain various plasmonic properties of gold and silver nanoparticles while the later chapters focus on more accurately combining experimental and theoretical methods to explain the plasmonic properties of hollow gold nanoparticles of various shapes. The appendix contains a detailed description of the theoretical methods used throughout the thesis. It is intended to serve as a guide such that a user could carry out the various types of calculations discussed in this thesis simply by reading this appendix.
15
Malmström, David. "Interfacing Complementary Separation Techniques with Mass Spectrometry Utilizing Electrophoresis, Nanoparticles, and Functionalized Magnetic Beads". Doctoral thesis, Uppsala universitet, Analytisk kemi, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-183666.
Abstract (sommario):
Capillary electrophoresis (CE) has during the last two decades become more robust and been able to separate neutral analytes without compromising the downstream detection. An interesting aspect in CE compared to more commonly used high-performance liquid chromatography is the orthogonal separation mechanism provided by CE. Compounds are separated based on charge and size with extremely high separation efficiencies. However, since mass spectrometry (MS) has become one of the most important analytical detectors and play a key role for pharmaceutical- and in clinical applications it is of major importance that the two techniques successfully can be combined without any compromises. Improvements in existing ion sources must be made in order to fully take advantage of the potential in capillary electrophoresis and mass spectrometry. One way is to miniaturize the ion source (paper I) in order to make it more compatible with the smaller liquid volumes and lower flow rates in CE. Despite these improvements challenges such as low sample concentrations, non-separated peaks, unspecific losses, and poor ionization still remain, and are addressed in this doctoral thesis. Separation of neutral analytes has previously been achieved with packed columns but with several disadvantages. Therefore, MS-compatible pseudostationary phases in the form of nanoparticles (paper II) are an interesting alternative with its minimized risk of clogging, reduced memory effects and better separation efficiencies. Particles or beads have also shown to be of importance when reducing the dynamic range in complex samples. By creating functionalized magnetic beads (paper III), complex samples such as human plasma can be fractionated in the manner that low molecular weight proteins are selectively enriched. Despite fractionation and enrichment of analytes of interest (paper IV) the ionization suppression could lead to biased sensitivity, increased baseline, retention variations and chromatographic distortion. Therefore the separation, as well as the ionization, is of major importance. For instance, in order to separate and detect monoclonal antibodies, which are an upcoming class of biotherapeutic drugs, the choice of capillary temperature and sheath liquid composition must be considered due to its major influence on charge state, peak intensity and memory effects (paper V).
16
Do, Jaekwon [Verfasser], e Jochen [Akademischer Betreuer] Feldmann. "Controlled spatial arrangement of gold nanoparticles using focused laser beams and DNA origami / Jaekwon Do. Betreuer: Jochen Feldmann". München : Universitätsbibliothek der Ludwig-Maximilians-Universität, 2014. http://d-nb.info/1053913850/34.
17
F, SARRI. "Optical microstructuring of alkali metal nanoparticle coatings on porous silica substrates induced by Bessel beam". Doctoral thesis, Università di Siena, 2019. http://hdl.handle.net/11365/1075534.
Abstract (sommario):
The ability to control atomic adsorption/desorption processes by light as well as nanoparticle growth
on proper substrates is nowadays recognized as a promising technique in nanotechnology. This
subject is a part of a rising area of research devoted to the development of micro and nanophotonic
devices, sensors, metamaterials. The experimental work in this thesis aims at obtaining ordered
microstructures exploiting atomic desorption phenomena such as LIAD (Light Induced Atomic
Desorption). The suitable substrates consist in nanoporous silica matrices sealed inside cells and
exposed to alkaline atom vapor. A Gaussian beam generated by a laser, transformed in Bessel beam
by a conical shape lens, has been used as desorption light: in such way, the nanoparticles are created
on the pores and they are arranged following the Bessel beam profile, obtaining then the order
microscopic structure. More efficiently a coating of alkali metal nanoparticles has been grown on the
porous substrate due to LIAD induced by a Hg lamp and then the atomic desorption induced by a
Bessel beam has been responsible for the redistribution of the generated nanoparticles in the
micrometric concentric ring structure following the beam profile. The experiments have been
performed using different alkaline atom vapors, moreover porous silica samples with different pore
size and lasers with different wavelengths have been used.
During the work, the experimental setup and procedure have been optimized, evaluating the best
conditions for obtaining a well defined structure, in particular as regards the power emitted by the
desorbing lasers and the lighting time intervals for the porous silica samples. Through adjustments to
these parameters multiple, overlapping or side-by-side, illuminations, without incurring erasing
phenomena, have been possible thus creating complex structures.
The structures thus obtained, whether simple or complex, act as micrometric masks made out of
nanoparticles, and they are persistent and reversible. These masks can be detected by illuminating
them with laser light and observing the ring-shaped pattern produced by diffraction.
The generated structures have been systematically analyzed verifying the effective formation of the
nanoparticles by detection of their absorption spectra, observing the microstructures under a
microscope and recording them with a CCD camera. By an image analysis software, the concentric ring
pattern, corresponding to a 2D quasi-Bessel function, has been studied, evaluating the spacing ring
distance from its Fourier transform using the FFT algorithm; in this way, the relationship between the
characteristics of the Bessel beam, the wavelength of the radiation and the physical characteristics of
the conical lens have been verified. Also, images of the ring-shaped pattern obtained by diffraction
have also been registered, in order to estimate the contrast with the background and its persistence
on the sample.
The experimental results on this thesis suggest a new technique for the laser structuring of alkali metal
nanoparticles in ordered patterns on micrometric scale resolution promising for many applications in
all-optical photonic devices.
18
Antonsson, Egill [Verfasser]. "Photoexcitation, photoionization, and X-Ray scattering of free nanoparticles prepared in a beam / Egill Antonsson". Berlin : Freie Universität Berlin, 2011. http://d-nb.info/102626619X/34.
19
Rivera, Felipe. "Electron Microscopy Characterization of Vanadium Dioxide Thin Films and Nanoparticles". BYU ScholarsArchive, 2012. https://scholarsarchive.byu.edu/etd/2975.
Abstract (sommario):
Vanadium dioxide (VO_2) is a material of particular interest due to its exhibited metal to insulator phase transition at 68°C that is accompanied by an abrupt and significant change in its electronic and optical properties. Since this material can exhibit a reversible drop in resistivity of up to five orders of magnitude and a reversible drop in infrared optical transmission of up to 80%, this material holds promise in several technological applications. Solid phase crystallization of VO_2 thin films was obtained by a post-deposition annealing process of a VO_{x,x approx 2} amorphous film sputtered on an amorphous silicon dioxide (SiO_2) layer. Scanning electron microscopy (SEM) and electron-backscattered diffraction (EBSD) were utilized to study the morphology of the solid phase crystallization that resulted from this post-deposition annealing process. The annealing parameters ranged in temperature from 300°C up to 1000°C and in time from 5 minutes up to 12 hours. Depending on the annealing parameters, EBSD showed that this process yielded polycrystalline vanadium dioxide thin films, semi-continuous thin films, and films of isolated single-crystal particles. In addition to these films on SiO_2, other VO_2 thin films were deposited onto a-, c-, and r-cuts of sapphire and on TiO_2(001) heated single-crystal substrates by pulsed-laser deposition (PLD). The temperature of the substrates was kept at ~500°C during deposition. EBSD maps and orientation imaging microscopy were used to study the epitaxy and orientation of the VO_2 grains deposited on the single crystal substrates, as well as on the amorphous SiO_2 layer. The EBSD/OIM results showed that: 1) For all the sapphire substrates analyzed, there is a predominant family of crystallographic relationships wherein the rutile VO_2{001} planes tend to lie parallel to the sapphire's {10-10} and the rutile VO_2{100} planes lie parallel to the sapphire's {1-210} and {0001}. Furthermore, while this family of relationships accounts for the majority of the VO_2 grains observed, due to the sapphire substrate's geometry there were variations within these rules that changed the orientation of VO_2 grains with respect to the substrate's normal direction. 2) For the TiO_2, a substrate with a lower lattice mismatch, we observe the expected relationship where the rutile VO_2 [100], [110], and [001] crystal directions lie parallel to the TiO_2 substrate's [100], [110], and [001] crystal directions respectively. 3) For the amorphous SiO_2 layer, all VO_2 crystals that were measurable (those that grew to the thickness of the deposited film) had a preferred orientation with the the rutile VO_2[001] crystal direction tending to lie parallel to the plane of the specimen. The use of transmission electron microscopy (TEM) is presented as a tool for further characterization studies of this material and its applications. In this work TEM diffraction patterns taken from cross-sections of particles of the a- and r-cut sapphire substrates not only solidified the predominant family mentioned, but also helped lift the ambiguity present in the rutile VO_2{100} axes. Finally, a focused-ion beam technique for preparation of cross-sectional TEM samples of metallic thin films deposited on polymer substrates is demonstrated.
20
Costa, Jessica. "Use and characterisation of free or immobilised enzymatic systems for the synthesis and functionalisation of novel materials". Doctoral thesis, Università di Siena, 2021. http://hdl.handle.net/11365/1127196.
Abstract (sommario):
The work reported in this Ph.D. thesis is focused on the use and immobilisation of enzymes to produce new materials, which are important for biotechnological applications.
The use of enzymes in industrial sectors is continuously increasing. Enzymes offer many advantages over traditional chemical processes. The research work of this thesis can be divided into two parts. The first part is focused on the immobilisation of laccase and chitinase. The main object of enzymatic immobilisation is to enhance the economics of biocatalytic processes. Enzymatic immobilisation allows the reuse of enzymes for an extended period of time and enables easier separation of the catalyst from the product. Furthermore, immobilisation improves many properties of enzymes: performance in the organic solvents, pH tolerance and heat stability. The most widely used immobilisation method is the covalent binding of the enzyme to support. Different type of support can be chosen for enzymatic immobilisation. As the material can plays a crucial role in the immobilisation process and the properties of the produced catalytic system. In this thesis we have chosen two different supports: super paramagnetic nanoparticles for both the enzymes used and the chitosan beads as an alternative support for chitinase. Magnetic nanoparticles show interesting properties for enzymatic immobilisation, they can be obtained with small size, increasing the yield of enzymatic immobilisation and above all, the reaction products can be easily recovered applying an external magnetic field. Magnetic nanoparticles were prepared following the traditional method of co-precipitation of Fe2+ and Fe3+ ions. This immobilisation process was successfully used for chitinase, obtaining a high immobilisation yield and increasing enzymatic stability. Different was for laccase, which having a different catalytic mechanism a revision of the synthesis has been attempt. The use of the magnetic nanoparticles obtained with the traditional method hampered the detection of stable radical species formed during the catalytic mechanism as it happens for the oxidation product of 2,2'-azino-bis (3-ethylbenzothiazolin-6-sulfonic acid) (ABTS), the standard compound used to test the enzyme activity. Changing some synthetic parameters, the new magnetic nanoparticles were produced and characterized. In fact nanoparticles with a lower aggregation state and a smaller hydrodynamic diameter were obtained and tested without any interference with the ABTS substrate. Chitinase was also immobilised on chitosan beads/Macro-Spheres (CMS), as this support is completely atoxic and so most suitable for application in food industries.The presence of active amino groups in deacetylated GlcNAc units of chitosan also enables the binding of the linker (glutaraldehyde and genipin) and then of the enzyme. The goal of this part of the thesis was to attempt the immobilisation of Chitinase on different supports, MNPs and CMS, for the efficient production of COS.
The second part of this thesis is focused on the use of enzymes to produce melanin pigments. Melanins have a variety of biological functions, including protection against UV radiation, free radical scavengers and metal ions chelators. Thanks to their properties, melanins found applications in several fields such as cosmetics, optoelectronics, food, and pharmacology. Eumelanin and Pheomelanin have been produced by oxidative enzymatic synthesis using laccase from Trametes versicolor and then characterized by the use of Multifrequency Continuos Wave (CW) and pulse Q-band EPR. Then, as soluble melanin pigments have important technological applications in different fields, like in optoelectonics, soluble pigments mimicking pyomelanin structure have been synthesized starting from Homogentisic Acid and Gentisic Acid monomers and spectroscopically characterized with their antioxidant activities determination.
21
MALAQUIN, Laurent. "Dispositifs ultra-sensibles pour le nano-adressage electrique. Application a la detection de biomolecules". Phd thesis, Université Paul Sabatier - Toulouse III, 2004. http://tel.archives-ouvertes.fr/tel-00009243.
Abstract (sommario):
" Because technology provides the tools and biology the problems, the two should enjoy a happy marriage ! "1 . Cette phrase resume parfaitement l'esprit du projet qui a motive ces travaux de these. En effet, le couplage des biotechnologies et des micro et nano technologies, resume sous le vocable < Nanobiotechnologies > est une activite en plein essor qui laisse presager de nombreuses applications en particulier dans le domaine de la biodetection. Lobjectif principal de ces travaux est dedie au developpement de strategies d'adressage de biomolecules a l'echelle nanometrique pour des applications de biodetection. Le premier aspect de ce travail est d'ordre technologique. Il concerne la fabrication de dispositifs d'adressage bases sur des reseaux de nanoelectrodes planaires. En utilisant un procede reposant sur lutilisation de la lithographie electronique haute resolution sur un microscope TEM/STEM, nous avons pu demontrer la fabrication de dispositifs a base de nanoelectrodes presentant des espaces inter-electrodes controlables entre 100 et 15nm. Une technique de lithographie alternative, la Nano-Impression est egalement presentee comme une solution possible a la replication de nanodispositifs fabriques par lithographie electronique. La deuxieme partie des travaux est dediee a la mise en place dun schema de detection de nanoparticules que nous avons developpe autour de dispositifs bases sur des reseaux delectrodes inter-digitees. Avant de nous interesser a l'utilisation de ces dispositifs pour une application biologique, nous avons etudie leur reponse electrique vis-a-vis de l'absorption de nanoparticules d'Or par interaction electrostatique. Les premiers resultats obtenus montrent que le schema de detection permet d'atteindre un niveau de sensibilite ultime au travers d'une mesure directe de la conductance des dispositifs. Certaines experiences montrent en effet la possibilite de mesurer electriquement l'adsorption d'une seule nanoparticule. Enfin, la derniere partie de ces travaux est dediee a l'adaptation de ce protocole pour la detection de biomolecules fonctionnalisees par des nanoparticules d'Or. Pour cela, nous avons employe une approche simple basee sur un systeme de reconnaissance entre une molecule cible et une molecule sonde. Ce schema a ete applique a la detection d'interaction antigene/anticorps et nous a permis de transcrire la selectivite de la reconnaissance entre les anticorps dans le depot des nanoparticules qui se traduit par une modification importante de la conductance du dispositif. Les possibilites d'integration ainsi que la compatibilite des dispositifs avec des systemes de microfluidique rendent ce schema de detection particulierement adapte pour le developpement d'un systeme integre de biodetection a tres haute sensibilite. 1 S. Fields, Proc. Natl. Acad. Sci. USA, vol 98, pp 10051-10054 (2001)
22
Larsson, Mina. "Application of Raman and Fluorescence Spectroscopy to Single Chromatographic Beads". Doctoral thesis, Uppsala : Acta Universitatis Upsaliensis : Univ.-bibl. [distributör], 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-5741.
23
Johansson, Anders. "Template-Based fabrication of Nanostructured Materials". Doctoral thesis, Uppsala : Acta Universitatis Upsaliensis, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-7364.
24
Khaywah, Mohammad Yehia. "New ultrasensitive bimetallic substrates for surface enhanced Raman scattering". Thesis, Troyes, 2014. http://www.theses.fr/2014TROY0041/document.
Abstract (sommario):
Afin de développer des capteurs ultrasensibles des substrats fiables pour la diffusion Raman exaltée de surface (SERS) ont été fabriqués. Les deux meilleurs candidats de matériaux constituant les nanoparticules pour des substrats SERS sont l’argent et l’or. L’argent présente un meilleur facteur d’exaltation de l'intensité Raman et l’or est stable dans les milieux biologiques. C’est pourquoi la combinaison de ces deux métaux dans des nanostructures bimétalliques semble être une approche prometteuse qui combine les propriétés de surface de l’or et d’exaltation de l’argent. Le recuit thermique des couches métalliques minces est utilisé comme une technique simple et peu coûteuse. Cette dernière permet d’élaborer des substrats homogènes et reproductibles de nanoparticules bimétalliques or-argent ayant un facteur d’exaltation importante. Ces nanoparticules gardent leurs propriétés d’exaltation même après une année de fabrication. En jouant sur la composition de nanoparticules bimétalliques il est possible d’avoir une résonance de plasmons de surface localisés (LSPR) sur tout le spectre visible. Ces substrats sont caractérisés par une exaltation SERS supérieure lorsque la résonance plasmon est plus proche de la longueur d'onde d'excitation Raman. En outre, les nanoparticules bimétalliques de différentes tailles, compositions ont été réalisés par lithographie électronique. L’étude systématique de leurs propriétés plasmoniques et de leur exaltation SERS a révélé une conservation du lien entre résonance plasmon et signal SERSDriven by the interest in finding ultrasensitive sensors devices, reliable surface enhanced Raman scattering (SERS) based substrates are fabricated. Silver and gold nanoparticles are two of the best candidates for SERS substrates where Ag nanoparticles exhibit large enhancing ability in Raman intensity while Au nanostructures are stable in biological systems. Hence, combining the two metals in bimetallic nanostructures appeared to be a promising approach in order to sum the merits of Au surface properties and Ag enhancing ability. Thermal annealing of thin metallic films is used as a simple and relatively inexpensive technique to elaborate homogenous and reproducible Ag/Au bimetallic nanoparticles SERS substrates with high enhancing ability. The fabricated nanoparticles proved their enhancing stability even after one year of fabrication. Manipulating the composition of Ag/Au bimetallic NPs resulted in tuning the Localized Surface Plasmon Resonance (LSPR) over the whole visible spectrum, where the substrates are characterized with higher SERS enhancement when they exhibit LSPR closer to the Raman excitation wavelength. Additionally, bimetallic nanoparticles patterns with different size, composition and lattice constants have been conducted by electron beam lithography. The systematic study of their interesting plasmonic and SERS enhancing properties revealed maintenance in the LSPR-SERS relation by changing the nanoparticle size
25
Muhsin, Mohammad Didare Alam. "Preparation and in vitro evaluation of a polymer based controlled release dry powder inhaler formulation for pulmonary delivery". Thesis, Queensland University of Technology, 2014. https://eprints.qut.edu.au/71806/1/Mohammad%20Didare%20Alam_Muhsin_Thesis.pdf.
Abstract (sommario):
This thesis described the synthesis of an L-leucine conjugate of the biodegradable polymer, chitosan and its potential application for the development of controlled release nanoparticulate dry powder inhaler (DPI) formulations. The study demonstrated that the physicochemical properties of conjugated chitosan nanoparticles had favourable effects on the dispersibility and controlled release profile of a model drug. The toxicity profile of the nanoparticulate formulation revealed promising outcome for its use in pulmonary delivery. The chitosan conjugate produced in this project would be useful for the application of polymer nanoparticulate systems for efficient lung delivery of drugs.
26
Shuwaikan, Mohammed Salem. "Investigation of the uptake, co-localisation, biological effects, and toxicity mechanism(s) of carboxyl-modified polystyrene nanoparticles (COO-PS-NPs) onto human bronchial epithelial (BEAS-2B) cells". Thesis, University of Birmingham, 2015. http://etheses.bham.ac.uk//id/eprint/6155/.
Abstract (sommario):
Carboxyl-modified polystyrene nanoparticles (COO-PS-NPs) have many potential applications, for example drug-delivery systems, but their toxicity remains poorly assessed. In the current study, characterisation, uptake and toxicity of two sized COO-PS-NPs in cultured BEAS-2B lung epithelial cells were investigated. The 20nm sized COO-PS-NPs tended to aggregate heavily in the cell culture media yielding larger aggregates, in contrast the 100nm COO-PS-NPs were stable. Electron and confocal microscopy demonstrated that COO-PS-NPs rapidly accumulate in vesicle-like structures within cells and fluorescent organelle co-staining showed the presence of 20nm COO-PS-NPs in mitochondria and the 100nm COO-PS-NPs in Golgi apparatus. Cellular studies revealed that COO-PS-NPs cause GSH depletion and induce ROS generation resulting in oxidative stress. Studies in a cell-free system showed that COO-PS-NPs directly deplete levels of GSH in solution. Size- and concentration-dependent DNA strand breaks (by comet assay) were also observed and both 20nm and 100nm COO-PS-NPs induced caspases-3/7 activation in a Ca2+ independent manner, however a significant decrease in cell viability was observed only at high concentrations of 20nm COO-PS-NPs. In summary, this in vitro study demonstrated that toxicity of the 20nm COO-PS-NPs is mediated by oxidative stress after co-localisation to the mitochondria and that further studies are needed to assess the safety of COO-PS-NPs.
27
Jafri, Syed Hassan Mujtaba. "Building Systems for Electronic Probing of Single Low Dimensional Nano-objects : Application to Molecular Electronics and Defect Induced Graphene". Doctoral thesis, Uppsala universitet, Tillämpad materialvetenskap, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-160630.
Abstract (sommario):
Nano-objects have unique properties due to their sizes, shapes and structure. When electronic properties of such nano-objects are used to build devices, the control of interfaces at atomic level is required. In this thesis, systems were built that can not only electrically characterize nano-objects, but also allow to analyze a large number of individual nano-objects statistically at the example of graphene and nanoparticle-molecule-nanoelectrode junctions. An in-situ electrical characterization system was developed for the analysis of free standing graphene sheets containing defects created by an acid treatment. The electrical characterization of several hundred sheets revealed that the resistance in acid treated graphene sheets decreased by 50 times as compared to pristine graphene and is explained by the presence of di-vacancy defects. However, the mechanism of defect insertion into graphene is different when graphene is bombarded with a focused ion beam and in this case, the resistance of graphene increases upon defect insertion. The defect insertion becomes even stronger at liquid N2 temperature. A molecular electronics platform with excellent junction properties was fabricated where nanoparticle-molecule chains bridge 15-30nm nanoelectrodes. This approach enabled a systematic evaluation of junctions that were assembled by functionalizing electrode surfaces with alkanethiols and biphenyldithiol. The variations in the molecular device resistance were several orders of magnitude and explained by variations in attachment geometries of molecules. The spread of resistance values of different devices was drastically reduced by using a new functionalization technique that relies on coating of gold nanoparticles with trityl protected alkanedithiols, where the trityl group was removed after trapping of nanoparticles in the electrode gap. This establishment of a reproducible molecular electronics platform enabled the observation of vibrations of a few molecules by inelastic tunneling spectroscopy. Thus this system can be used extensively to characterize molecules as well as build devices based on molecules and nanoparticles.
28
Vandenhecke, Ellick. "Nanostructuration de surfaces diélectriques par pulvérisation ionique pour guider la croissance de nanoparticules métalliques". Thesis, Poitiers, 2014. http://www.theses.fr/2014POIT2272/document.
Abstract (sommario):
L'objectif de ce travail est d'une part de comprendre et contrôler la formation de rides périodiques nanométriques produites par pulvérisation ionique de films minces diélectriques. D'autre part, ces surfaces nanostructurées sont utilisées pour guider la croissance et l'organisation de nanoparticules d'argent. Ces systèmes anisotropes sont caractérisés par une position spectrale de la résonance plasmon de surface dépendant de la polarisation de la lumière incidente. Nous étudions d'abord par AFM et GISAXS l'influence des conditions de pulvérisation (angle d'incidence et énergie des ions, température, flux, fluence) sur la morphologie des rides (période, amplitude, ordre, ...). Les paramètres pertinents pour le contrôle de la morphologie sont identifiés ainsi qu'une partie des mécanismes physiques mis en jeu. Ensuite, nous étudions par HAADF-STEM l'influence des conditions de croissance (angle d'incidence du flux métallique, degré d'organisation des rides) sur les propriétés structurales des nanoparticules d'argent. Nous montrons que la croissance préférentielle des nanoparticules le long des rides est favorisée par des effets d'ombrage, ce qui conduit à la formation de chaînes linéaires de même période que les rides sous-jacentes et au sein desquelles les nanoparticules sont plus ou moins alignées et allongées. Cela se traduit par une anisotropie optique en champ lointain variable due à la polydispersité des distances interparticules (inférieures à quelques nanomètres) ainsi que des phénomènes de couplage en champ proche plus ou moins importants. Ces structures peuvent trouver des applications en spectroscopie Raman exaltée de surface (SERS)On the one hand, the aim of this work is to understand and control the formation of periodic nanometric ripples produced by ion sputtering of dielectric thin films. On the other hand, these nanostructured surfaces are used to guide the growth and organization of silver nanoparticles. These anisotropic systems are characterized by a surface plasmon resonance whose spectral postion is dependent on the polarization of the incident light. We first study the influence of different ion beam sputtering parameters (the ions incidence angle and energy, temperature, energy, flux, fluence) on the ripple morphology (period, amplitude, order, ...) by AFM and GISAXS. The relevant parameters for the control of the ripple morphology are identified as well as some of the physical mechanisms involved. Then, we study the influence of the growth conditions on the structural properties of the nanoparticles (metal deposition angle, ripples pattern quality) by HAADF-STEM. We show that the preferential growth along the ripples is promoted by shadowing effects, thus leading to the formation of linear chains with period similar to the underlying ripples and with more or less elongated and aligned nanoparticles. This results in a far-field tunable optical anisotropy arising from polydisperse interparticle gaps (less than a few nanometers) as well as from more or less strong near-field coupling phenomena. These structures could offer potential for surface enhanced Raman spectroscopy (SERS) applications
29
Kulaga, Emilia. "Antimicrobial coatings for soft materials". Thesis, Mulhouse, 2014. http://www.theses.fr/2014MULH5312/document.
Abstract (sommario):
Les infections bactériennes lorsqu’elles se développent à partir d’implants sont très difficiles à traiter, l’issue courante étant un retrait pur et simple de l’implant incriminé. Dans ce cadre, les revêtements des biomatériaux ont un rôle important à jouer pour, d’une part, prévenir l’adhésion bactérienne et d’autre part, éliminer les bactéries présentes. Ces revêtements antibactériens doivent par ailleurs permettre une intégration tissulaire des biomatériaux aux cellules rencontrées sur le site de l’implantation. Dans ce travail une nouvelle famille de revêtements antibactériens a été développée. Ils contiennent et libèrent de manière contrôlée un agent bioactif. Ils sont constitués de multicouches de polymère plasma d'anhydride maléique déposées à la surface de fibres de polypropylène tressées et constituant le matériau à implanter. Entre chaque dépôt de polymère plasma (agissant comme couche barrière), des nanoparticules d'argent sont piégées formant ainsi des réservoirs d’agent antibactérien. En raison des différences de propriétés mécaniques entre les films minces plasma et le substrat massique élastique (i.e. tissu de fibre de polypropylène), la résistance à la traction génère des fissures dans les couches polymère plasma, qui sont utilisées comme canaux de diffusion pour les substances bioactives (dans notre cas les ions argent). Avant étirement, la libération spontanée des ions argent par simple diffusion aux travers des couches barrières peut être contrôlée en jouant sur le taux de réticulation des couches plasma. Au cours de l'étirement, le contrôle réversible de l'ouverture des fissures permet une libération maîtrisée des ions argent. Dans le domaine des textiles et d'autres biomatériaux souples, cette stratégie est prometteuse en raison des contraintes mécaniques qui se produisent naturellement sur le site de l'implantation.L'impact de différents types de procédures de stérilisation couramment utilisés (autoclave et irradiation par faisceau d’électrons) sur les propriétés du matériau développé a également été étudié. En particulier, l’incidence sur la chimie de surface, la dispersion des nanoparticules d'argent et la formation de fissures sous étirement a été regardée. La méthode de stérilisation par faisceau d’électrons permet de conserver les propriétés finales recherchées. Enfin, les propriétés antibactériennes du nouveau matériau ont été étudiées. L'effet du relargage des ions argent sur des bactéries Escherichia coli planctoniques, l'adhésion bactérienne et la formation de biofilm sur le système étiré et non-étiré a été évalué. L’intégrité membranaire des bactéries adhérées et des bactéries dans les biofilms a été suivie au cours de l'étude comme indicateur de l’état physiologique des bactéries. Les résultats ont suggéré que la sensibilité des bactéries aux concentrations faibles d'ions d'argent libérés aboutit à la formation de différents types de structures de biofilms sur les matériaux étudiés. L’ensemble des résultats obtenus donne une base solide pour le développement de matériaux intelligents capables de contrôler la libération du principe actif sur le site de l'infection. Nos résultats montrent qu’une faible dose d’argent peut suffire à contrôler l’infection en agissant sur la structure des biofilms formésDespite strict operative procedures to minimize microbial contaminations, bacterial infection of implants significantly raises postoperative complications of surgical procedures. One of the promising approaches is to adjust and control antimicrobial properties of the implant surface. New types of antibacterial coatings prepared via plasma polymer functionalization step have been developed. These coatings contain and release in a control way a bioactive agent. Controlled release was achieved by the fabrication of plasma polymer multilayer systems, which consist of two layers of Maleic Anhydride Plasma Polymer deposited on the surface of Polypropylene made surgical mesh. In between plasma polymer layers, silver nanoparticles are trapped as an antibacterial agent reservoir. Owing to differences between mechanical properties of the plasma-polymer thin films and the elastic bulk substrates, tensile strengths generate cracks within the plasma polymer, which might be used as diffusive channels for bioactive substances, here silver ions. The cracks can be controlled mechanically in a reversible way. The tailoring of the spontaneous release of bioactive agent is achieved by the modification of the second plasma polymer deposition conditions. In addition, during mechanical stimulation of the designed material, control over silver ion release is achieved through an elongation-dependent releasing process allowed by the reversible control of the cracks. In the field of textiles and other soft biomaterials, this strategy is promising due to the mechanical stresses that naturally occur at the implant location. In regard of possible application of the developed system as a future biomaterial, the impact of different types of commonly used sterilization procedures on the properties of developed material was studied. The effects of autoclaving and electron beam sterilization methods on the surface chemistry, the dispersion of embedded silver nanoparticles in the plasma polymer and the cracks formation of the developed material was verified. Results showed the compatibility of the developed system with electron beam sterilization method. The antibacterial properties of the new material have been evaluated. The effect of developed system on planktonic bacteria, bacterial adhesion and biofilm formation on stretched and unstretched system was studied. The membrane integrity of the adhered bacteria and bacteria in biofilms was followed during the study as an indicator of the physiologic state of bacteria. Results suggested that the sensitivity of bacteria to low concentrations of released silver ions resulted in the formation of different types of structures of the biofilms on the studied materials. The results give a strong base on the future of intelligent, silver containing materials that control the release at the site of infection. Our results show that low doses of silver may be sufficient to control infection by acting on the structure of bacterial biofilms
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MIGLIORINI, LORENZO. "DEVELOPMENT OF FUNCTIONAL NANOCOMPOSITE MATERIALS TOWARDS BIODEGRADABLE SOFT ROBOTICS AND FLEXIBLE ELECTRONICS". Doctoral thesis, Università degli Studi di Milano, 2020. http://hdl.handle.net/2434/704286.
Abstract (sommario):
World population is continuously growing, as well as the influence we have on the ecosystem’s natural equilibrium. Moreover, such growth is not homogeneous and it results in an overall increase of older people. Humanity’s activity, growth and aging leads to many challenging issues to address: among them, there are the spread of suddenly and/or chronic diseases, malnutrition, resource pressure and environmental pollution. Research in the novel field of biodegradable soft robotics and electronics can help dealing with these issues. In fact, to face the aging of the population, it is necessary an improvement in rehabilitation technologies, physiological and continuous monitoring, as well as personalized care and therapy. Also in the agricultural sector, an accurate and efficient direct measure of the plants health conditions would be of help especially in the less-developed countries. But since living beings, such as humans and plants, are constituted by soft tissues that continuously change their size and shapes, today’s traditional technologies, based on rigid materials, may not be able to provide an efficient interaction necessary to satisfy these needs: the mechanical mismatch is too prohibitive. Instead, soft robotic systems and devices can be designed to combine active functionalities with soft mechanical properties that can allow them to efficiently and safely interact with soft living tissues. Soft implantable biomedical devices, smart rehabilitation devices and compliant sensors for plants are all applications that can be achieved with soft technologies. The development of sophisticated autonomous soft systems needs the integration on a unique soft body or platform of many functionalities (such as mechanical actuation, energy harvesting, storage and delivery, sensing capabilities). A great research interest is recently arising on this topic, but yet not so many groups are focusing their efforts in the use of natural-derived and biodegradable raw materials. In fact, resource pressure and environmental pollution are becoming more and more critical problems. It should be completely avoided the use of in exhaustion, pollutant, toxic and non-degradable resources, such as lithium, petroleum derivatives, halogenated compounds and organic solvents. So-obtained biodegradable soft systems and devices could then be manufactured in high number and deployed in the environment to fulfil their duties without the need to recover them, since they can safely degrade in the environment. The aim of the current Ph.D. project is the use of natural-derived and biodegradable polymers and substances as building blocks for the development of smart composite materials that could operate as functional elements in a soft robotic system or device. Soft mechanical properties and electronic/ionic conductive properties are here combined together within smart nanocomposite materials. The use of supersonic cluster beam deposition (SCBD) technique enabled the fabrication of cluster-assembled Au electrodes that can partially penetrate into the surface of soft materials, providing an efficient solution to the challenge of coupling conductive metallic layers and soft deformable polymeric substrates. In this work, cellulose derivatives and poly(3-hydroxybutyrate) bioplastic are used as building blocks for the development of both underwater and in-air soft electromechanical actuators that are characterized and tested. A cellulosic matrix is blended with natural-derived ionic liquids to design and manufacture completely biodegradable supercapacitors, extremely interesting energy storage devices. Lastly, ultrathin Au electrodes are here deposited on biodegradable cellulose acetate sheets, in order to develop transparent flexible electronics as well as bidirectional resistive-type strain sensors. The results obtained in this work can be regarded as a preliminary study towards the realization of full natural-derived and biodegradable soft robotic and electronic systems and devices.
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Čangelová, Katarína. "Studium možných aplikací polymeru kyseliny glutamové". Master's thesis, Vysoké učení technické v Brně. Fakulta chemická, 2019. http://www.nusl.cz/ntk/nusl-401873.
Abstract (sommario):
The subject of the thesis is study of possible applications of isoform of glutamic acid polymer (-PGA). The theoretical part is focused on the properties of this biopolymer and potential applications in various areas. Producers and mechanisms of biosynthesis are also mentioned. In the experimental part, the polymer was firstly characterised by following methods: FT-IR spectroscopy, TGA, DSC and SEC-MALS. Its isoelectric point, antimicrobial activity and solubility in various solvents were also determined. The biopolymer was also precipitated by divalent cations and its interaction with oppositely charged CTAB surfactant was studied. The main experimental study was researching the effect of -PGA on viability of Saccharomyces cerevisiae and Lactobacillus rhamnosus under stress conditions by flow cytometry. The performed stresses included ethanol exposure, high temperature and freezing stress, in which its effects were compared to conventional cryoprotectants. The cells of the mentioned microorganisms were also stressed osmotically and exposed to model gastrointestinal juices - gastric, pancreatic and bile. The protective effects of -PGA on the cells were recorded in ethanol stress on Lactobacillus rhamnosus. Its excellent cryoprotection properties were confirmed and its protective effect of gastric juice exposure on Saccharomyces cerevisiae cells was also observed. At the end of the experimental part, -PGA/alginate beads suitable for encapsulation of probiotic bacteria and -PGA/chitosan nanoparticles for encapsulation of biologically active substances.
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She, Zhe. "Generation of micro/nano metallic nanostructures using self-assembled monolayers as template and electrochemistry". Thesis, University of St Andrews, 2012. http://hdl.handle.net/10023/3089.
Abstract (sommario):
This thesis studies a scheme to fabricate small-scaled metal structures by electrochemical metal deposition and lift off. The key point is the use of self-assembled monolayers (SAMs) to control both interfacial charge transfer in electrodeposition and adhesion of the deposit to the substrate. Patterned SAMs exhibiting blocking and non-blocking areas are applied as templates in electrochemical deposition of Cu or Au. Thiol SAMs on Au substrates are used, namely alkane thiols and thiols combining an aliphatic chain with a biphenyl or biphenyl analogous pyridine-phenyl moieties. The patterning of SAMs is realised with microcontact printing (μCP) and electron beam lithography. Electrochemical deposition based on defects in the SAMs is optimised towards generating small nanostructures and depending on the system single or stepped potential procedures are applied. Generated metal structures are transferred to an insulator by lift off. Au microstructures (~10 μm) have been made with microcontact printing and transferred onto epoxy glue, which can potentially be used as microelectrodes in electroanalytical chemistry. Sub-100 nm Cu features and sub-40 nm Au features have been created with electron beam lithography respectively. Lift off process has successfully transferred Cu nanostructures onto epoxy glue with high precision. In contrast to the deposition mediated by defects, Cu deposition mediated by discharging Pd²⁺ coordinated to a pyridine terminated SAM directly through the SAM molecules has been explored as a new approach. This new approach has potential to decrease the size of the metal structure further and the preliminary results show possibility of sub-10 nm features. SAMs prepared with a newly synthesised molecule, 3-(4'-(methylthio)-[1,1'-biphenyl]-4-yl)propane-1-thiol, are characterised by STM, XPS and NEXAFS. The metal structures are investigated by SEM, AFM and STM.
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Dethlefsen, Mark Georg Bernhard. "Charge transfer processes of atomic hydrogen Rydberg states near surfaces". Thesis, University of Oxford, 2013. http://ora.ox.ac.uk/objects/uuid:1ef5ece3-43cf-40fc-a1fd-bf7c637e2d23.
Abstract (sommario):
When approaching a metal surface, the electronic structure of Rydberg atoms or molecules is perturbed by the surface potential and at close enough distances resonant ionisation of the Rydberg electron into the conduction band of the surface can occur. It is possible to interfere in this process and steer the ionisation distance by making use of the polarisability of the Rydberg orbital in the presence of electric fields. The resulting ions from the surface can extracted via electric fields and subsequently detected via well established ion detection schemes. The question of how this charge-transfer process is affected by different properties of the surface (both electronic and structural) represents the main aspect of the work presented in this thesis. At first, the charge transfer of atomic hydrogen Rydberg atoms with a flat gold metal surface is investigated. While such a surface might appear homogeneous, stray fields are present in its vicinity due to local variations in the surface work function. The surface ionisation process as a function of applied electric field is therefore measured experimentally and the results are compared with classical Monte-Carlo simulations (which include stray field effects). This way the possibility to utilize Rydberg states as a probe of the magnitude of such stray fields is demonstrated. To investigate the effect the surface structure can have on the ionisation process, the interaction of Rydberg atoms with surfaces covered by nanoparticles is investigated. Surface ionisation is measured at a 5 nm nanoparticle monolayer surface and it is shown that population transfer between surface- and vacuum-oriented Rydberg states occurs. In addition, results are presented, which suggest a dependence of the ionisation process on the relative size of Rydberg orbital and nanoparticle. Furthermore, charge transfer between a Rydberg state and discrete electronic states at the surface vacuum interface are investigated by performing experiments with a Cu(100) band-gap semiconductor surface. By analysing surface ionisation as a function of collisional velocity ionisation rates can be determined and are subsequently compared with theoretical predictions. The potential of identifying resonant ionisation is thereby demonstrated. Last, a new method to produce 2s atomic hydrogen via mixing of the 2s and 2p state in an electric field is proposed and first experimental results are presented, thus demonstrating viability of the idea. The experiments presented in this thesis represent the most in depth analysis of the charge-transfer process between atomic hydrogen Rydberg states and a range of different surfaces to date. As such, they demonstrate the potential of utilizing the unique properties of Rydberg states and their applicability as surface probes. In addition, these results pave the way for further experiments involving thin films or the phenomenon of quantum reflectivity.
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Koneti, Siddardha. "In situ and 3D environmental transmission electron microscopy of Pd-Al2O3 nano catalysts : Fast tomography with applications to other catalytic systems in operando conditions and to electron beam sensitive nanomaterials". Thesis, Lyon, 2017. http://www.theses.fr/2017LYSEI123/document.
Abstract (sommario):
Au début du XXIème siècle, la Microscopie Electronique à Transmission en mode Environnemental (ETEM) est devenue l’une des techniques les plus fiables de caractérisation de nanomatériaux dans des conditions simulant leur vie réelle. L’ETEM est maintenant en mesure de suivre l’évolution dynamique des nanomatériaux dans des conditions variables comme l’exposition à des températures élevées, l’observation en milieux liquide ou gazeux à diverses pressions. Parmi différents domaines de recherche et développement concernés, la catalyse peut bénéficier de manière significative des avancées permises par la microscopie électronique environnementale. Cette thèse, dédiée au développement de l’ETEM au laboratoire MATEIS, a commencé avec l’étude du système catalytique Pd-alumine. Les nanoparticules de Pd déposées sur alpha -Al2O3 et delta-Al2O3 sont très utilisées en physicochimie avec un impact environnemental important : en particulier dans le domaine de l’hydrogénation sélective, pour la synthèse de polymères ou l’hydrogénation de CO2 pour la production de méthane. Nous avons tout d’abord effectué des analyses 2D aux différentes étapes du processus de synthèse du catalyseur : imprégnation du précurseur, séchage et chauffage pour la calcination dans l’air à la pression atmosphérique. La motivation de cette approche a été de comparer des analyses post mortem avec des traitements en ETEM où l’évolution des nanoparticules peut être mesurée in situ et pas seulement « avant » et « après ». De manière générale, les études faites en ETEM en 2D donnent un aperçu limité sur la morphologie des objets et la distribution spatiale des nanoparticules supportées. Nous avons développé une nouvelle approche d’acquisition rapide pour collecter dans des temps très courts des séries d’images sous différents angles de vue pour la tomographie électronique, la rapidité de cette acquisition étant un prérequis pour appréhender correctement la morphologie d’un nano-système au cours de son évolution dynamique in situ. La technique a ensuite été utilisée pour l’étude de plusieurs systèmes où une acquisition tridimensionnelle rapide est indispensable, notamment sur un sujet concernant un enjeu sociétal important, la dépollution des moteurs diesel : l’oxydation de la suie a été étudiée in situ sur des supports à base de zircone entre 400 et 600°C et une pression de 2 mbar d’oxygène à différents degrés de combustion, ce qui a permis d’extraire des données cinétiques telle que l’énergie d’activation du processus. La tomographie électronique rapide a été également appliquée à des matériaux sensibles au faisceau électronique, comme des nanocomposites polymères et des objets biologiques, montrant le large spectre d’applications possibles pour cette technique, qui constitue un pas important vers la caractérisation operando 3D de nanomatériaux en temps réelIn the beginning of the XXIst century, Environmental Transmission Electron Microscopy has become one of the reliable characterization techniques of nanomaterials in conditions mimicking their real life. ETEM is now able to follow the dynamic evolution of nanomaterials under various conditions like high temperature, liquid or various gas pressures. Among various fields of research, catalysis can benefit significantly from Environmental Microscopy. This contribution starts with the study of the Palladium-Alumina catalytic system. Pd nanoparticles supported by α-Al2O3 and δ-Al2O3 are of an important physicochemical and environmental interest, particularly in the field of selective hydrogenation in petrochemistry, for the synthesis of polymers or CO2 hydrogenation for methane production. We first performed 2D analyses at different steps of the synthesis process, then the same synthesis steps were performed under in situ conditions. The motivation of this approach was to compare post mortem treatments with ETEM observations. In general, 2D data provide limited insights on, for example, the morphology and position of supported nanoparticles. We have then developed a new fast acquisition approach to collect tomographic tilt series in very short times, enabling to reconstruct nano-systems in 3D during their dynamical evolution. Taking advantage of this approach, we have determined the activation energy for soot combustion on YSZ oxidation catalysts for diesel motors from volumetric data extracted from in situ experiments. Fast electron tomography was also applied to electron beam sensitive materials, like polymer nanocomposites and biological materials, showing the wide spectrum of possible applications for rapid 3D characterization of nanomaterials
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Stanislav, Silvestr. "Příprava nízkodimenzionálních III-V polovodičů". Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2021. http://www.nusl.cz/ntk/nusl-443735.
Abstract (sommario):
Tato diplomová práce se zabývá přípravou nanostruktur z indium arsenidu (InAs) pomocí metody molekulární svazkové epitaxe (MBE). Důraz je kladen na výrobu struktur ve formě nanodrátů na křemíkovém substrátu. V úvodní části práce je popsána motivace pro studium III-V polovodičů a konkrétně InAs. Následující kapitoly vysvětlují dva základní princpy tvorby nanodrátů. Experimentální část práce diskutuje možnost přípravy indiového katalyzátoru pro samokatalyzovaný růst InAs nanodrátů v konkrétní aparatuře MBE. Následuje prezentace výsledků růstu InAs nanodrátů mechanismem selektivní epitaxe (SAE). Nanodráty byly vyrobeny na substrátu s termálně dekomponovaným oxidem a rovněž na substrátech s litograficky připravenou oxidovou maskou.
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Liu, Yang. "‘Tri-3D’ electron microscopy tomography by FIB, SEM and TEM : Application to polymer nanocomposites". Thesis, Lyon, INSA, 2013. http://www.theses.fr/2013ISAL0076/document.
Abstract (sommario):
Ce travail a porté sur la caractérisation et la quantification en 3D de la répartition de charges de différents types (nanoparticules, nanotubes, etc.) dans des matrices polymères. Nous nous focalisons sur les techniques de tomographie en microscopie électronique. Une approche multiple en tomographie électronique a été réalisée : la tomographie en FIB/MEB (faisceau d’ions focalisé/microscope électronique à balayage), la tomographie en MEB et la tomographie en MET (microscope électronique en transmission). Les nanocomposites polymère sont généralement élaborés aux fins d’améliorer les propriétés physiques (mécanique, électrique, etc.) du matériau polymère constituant la matrice, grâce à une addition contrôlée de charges nanométriques. La caractérisation de tels matériaux, et l’établissement de corrélations précises entre la microstructure et les propriétés d’usage, requièrent une approche tri-dimensionnelle. En raison de la taille nanométrique des charges, la microscopie électronique est incontournable. Deux systèmes de nanocomposite polymère ont été étudiés par une approche multiple de tomographie électronique : P(BuA-stat-S)/MWNTs (copolymère statistique poly (styrène-co-acrylate de butyl) renforcé par des nanotubes de carbone multi-parois), et P(BuA-stat-MMA)/SiO2 (copolymère statistique poly(butyl acrylate-co-methyl methacrylate) renforcé par des nanoparticules de silice). Par combinaison de divers techniques, la caractérisation et la quantification des nanocharges ont été possibles. En particulier, la taille, la fraction volumique et la distribution des charges ont été mesurées. Cette étude a ainsi fourni des informations en 3D qui contribuent à mieux comprendre les propriétés des nanocomposites. Une attention particulière a été portée aux artefacts et causes d’erreur possibles durant l’étape de traitement 3D. Nous avons également essayé de comparer les différentes techniques utilisées du point de vue de leurs avantages et inconvénients respectifs, en dégageant des possibilités d’amélioration futureThis work is focused on the characterization and quantification of the 3D distribution of different types of fillers (nanoparticles, nanotubes, etc.) in polymer matrices. We have essentially used tomography techniques in electron microscopy. Multiple approaches to electron tomography were performed: FIB-SEM (focused ion beam/scanning electron microscope) tomography, SEM tomography and TEM (transmission electron microscope) tomography. Polymer nanocomposites are basically synthesized in order to improve the physical properties (mechanical, electric, etc.) of the pure polymer constituting the matrix, by a controlled addition of fillers at the nanoscale. The characterization of such materials and the establishment of accurate correlations between the microstructure and the modified properties require a three-dimensional approach. According to the nanometric size of the fillers, electron microscopy techniques are needed. Two systems of polymer nanocomposites have been studied by multiple electron tomography approaches: P(BuA-stat-S)/MWNTs (statistical copolymer poly(styrene-co-butyl acrylate) reinforced by multi-walled carbon nanotubes) and P(BuA-stat-MMA)/SiO2 (statistical copolymer poly(butyl acrylate-co-methyl methacrylate) reinforced by silica nanoparticles). By combining various techniques, the characterization and the quantification of nanofillers were possible. In particular, statistics about size, distribution and volume fraction of the fillers were measured. This study has then provided 3D information, which contributes to a better understanding of properties of the nanocomposites. Attention has been paid to analyze carefully original data, and artifacts and causes of errors or inaccuracy were considered in the 3D treatments. We also attempted to compare benefits and drawbacks of all techniques employed in this study, and perspectives for future improvements have been proposed
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Owusu-Mensah, Martin. "Understanding the first formation stages of (Y,Ti) nano-oxides in Oxide Dispersion Strengthened (ODS) steels". Thesis, Université Paris-Saclay (ComUE), 2019. http://www.theses.fr/2019SACLS310.
Abstract (sommario):
Les aciers appelés ODS (pour Oxide Dispersion Strengthened), renforcés par une dispersion homogène de nano-oxydes, sont des matériaux de structure avancés pour les futurs réacteurs nucléaires de fusion et de fission. En effet ces nano-oxydes, à base d’Y et Ti, servent comme centres de recombinaison de défauts ponctuels et d'obstacles aux mouvements des dislocations, améliorant de ce fait leur résistance aux radiations et aux températures élevées. La fabrication conventionnelle des aciers ODS est réalisée par broyage mécanique suivi de traitements thermo-mécaniques, et ne permet pas facilement de comprendre les mécanismes physiques conduisant à la précipitation des nano-oxydes, ce qui serait potentiellement utile pour optimiser leur production. La cinétique de formation de ces nano-oxydes peut être étudiée en utilisant une technique alternative, à savoir la synthèse par faisceaux d’ions, qui présente de nombreux avantages, notamment le contrôle précis des paramètres expérimentaux et la possibilité de décorréler divers facteurs contribuant à la cinétique de précipitation. Au cours de cette thèse, cette technique a été utilisée pour étudier la coprécipitation d'ions métalliques (Y et/ou Ti) et d'oxygène implantés dans un alliage modèle Fe-Cr de composition proche de celle typique des aciers ODS commerciaux. Des ions de Y, Ti et O à basse énergie ont été implantés dans des échantillons d'alliage Fe10wt%Cr de haute pureté à température ambiante. Les échantillons implantés ont ensuite été recuits à diverses températures entre 600 à 1100°C pour favoriser la précipitation de nano-oxydes, conformément au principe de cette technique. La microscopie électronique à transmission a été utilisée pour caractériser la structure cristallographique et la composition chimique des nano-oxydes formés lors de trois séries d'expériences. Tout d'abord, l'implantation séquentielle d'ions Ti et O a été mise en œuvre. Un recuit ultérieur a révélé qu’il n’y avait pas de précipitation d'oxyde de titane jusqu’à des températures inférieures à 1000°C, mais la présence de nano-oxydes riches en chrome avec une structure hexagonale de type corundum, qui contiennent une certaine quantité de Ti à des températures suffisamment élevées. Ce n’est qu’après le recuit à 1100°C que des nano-oxydes d’un autre type à cœur enrichi en Ti et coquille enrichie en Cr ont également été observés. Deuxièmement, l'implantation séquentielle d’ions Y et O a entraîné la formation à 800°C de nano-oxydes probablement riches en yttrium. Le recuit à 1100°C a favorisé la croissance des particules identifiées comme étant des nano-oxydes d’yttrium avec une coquille enrichie en Cr. Enfin, une implantation ionique séquentielle de deux ions métalliques (Y et Ti) a été réalisée, suivie d'une implantation d’O. L'ordre d'implantation des ions métalliques s'est révélé crucial pour la précipitation de nano-oxydes lors du recuit ultérieur. Lors de la séquence avec une implantation de Ti en premier, une précipitation d'oxyde riche en chrome de structure corundum hexagonale a été observée, très similaire au cas de l'implantation d’ions Ti et O. En revanche, la séquence avec une implantation d’ions Y en premier a produit des nano-oxydes d'yttrium-titane qui possèdent une structure non identifiable. En résumé, l’étude a démontré la faisabilité de la formation de nano-oxydes de Y, Ti et (Y, Ti) par implantation ionique. La thèse présente la caractérisation détaillée de ces nano-oxydes, ainsi que certaines de leurs caractéristiques spécifiques, telles que la présence de relations d'orientation entre les nano-oxydes et la matrice FeCr, qui ont été observées même dans le cas de nano-oxydes de type corundum riches en Cr. Enfin, les résultats obtenus, combinées avec les données de la littérature, sont discutées pour une meilleure compréhension des mécanismes impliqués dans la formation des nano-oxydes dans les aciers ODSOxide Dispersion Strengthened (ODS) steels, that is steels reinforced with a homogeneous distribution of (Y,Ti) oxide nano-particles, are advanced structural materials for nuclear applications. The oxide particles serve as point defect recombination centres and obstacles to dislocation motion thereby improving radiation resistance and high-temperature strength of these steels making them perfect candidate materials for future fusion and fission nuclear reactors. The conventional fabrication of ODS steels is achieved by mechanical alloying followed by thermomechanical heat treatments. This way of ODS steel production seems complicated to understand the physical mechanisms leading to the precipitation of nano-oxide particles. The kinetics of nanoparticle formation can be much better studied using an alternative technique of nanoparticle growth, namely Ion Beam Synthesis (IBS). This approach has many advantages including the precise control of experimental parameters and the ability to de-correlate various factors contributing to precipitation kinetics. A better knowledge gained in this way would be potentially helpful for optimization of ODS steel production routines. In the course of this PhD study, the IBS approach was applied to investigate the co-precipitation of metal (Y and/or Ti) and oxygen ions implanted into a model Fe-Cr alloy with the composition close to those typical for commercial ODS steels. Following the standard IBS schedule, consisting of ion implantation followed by high-temperature heat treatment, ions of Y, Ti and O at low energies were implanted into high-purity Fe10wt%Cr alloy samples at room temperature. The implanted samples were then annealed at various temperatures ranging from 600 to 1100°C to promote the precipitation of nano-oxide particles. A range of Transmission Electron Microscopy techniques were used to characterize the crystallographic structure and chemical composition of the nanoparticles. The study has been performed following three sets of experiments. First of all, the sequential implantation of Ti and O ions was implemented. Subsequent annealing at temperatures below 1000°C revealed that precipitation of titanium oxide was suppressed. Instead, chromium-rich nano-oxide particles with corundum hexagonal structure were found to precipitate. At sufficiently high temperatures these corundum particles were found to contain certain amount of Ti. Only after annealing at the highest temperature of 1100°C, particles of another type with Ti enriched core and Cr enriched shell were additionally fixed. Secondly, sequential Y and O ion implantation resulted in the formation of probable yttrium-rich oxides at 800°C. Annealing at 1100°C promoted their growth to larger sized yttria (Y₂O₃) particles with a Cr enriched shell. Finally, sequential ion implantation of both metal ions (Y and Ti) was performed, followed by O implantation. The order of metal ion implantation has been found to be crucial for subsequent oxide precipitation at the annealing stage. With the Ti implantation first in the sequence, the precipitation of corundum hexagonal chromium-rich oxide was observed, very similar to the case of Ti and O implantation. In contrast, implantation starting with Y produced yttrium-titanium oxide particles with unidentifiable structure. Summing up, the study has demonstrated the feasibility of the formation of Y, Ti and (Y,Ti) oxides by ion implantation. The thesis presents the detailed characterization of the nanoparticles, as well as the discovered specific features of precipitated particles, such as the presence of orientation relationships between the particles and the FeCr matrix, which was observed even for the case of Cr-rich corundum particles. Finally, the implications of the obtained results, in conjunction with the already known data from the existing literature, for the better understanding of the mechanisms involved in the formation of nano-oxide particles in ODS steels are discussed
38
Badran, Ghidaa. "Pollution atmosphérique particulaire : caractérisation physico-chimique et comparaison des effets toxiques des fractions extractible et non-extractible des PM₂.₅ In-vitro evaluation of organic extractable matter from ambient PM₂.₅ using human bronchial epithelial BEAS-2B cells : Cytotoxicity, oxidative stress, pro-inflammatory response, genotoxicity, and cell cycle deregulation. Toxicity of fine and quasi-ultrafine particles : focus on the effects of organic extractable and non-extractable matter fractions. Toxicological appraisal of the chemical fractions of ambient fine (PM₂.₅-₀.₃) and quasi-ultrafine (PM₀.₃) particles in human bronchial epithelial BEAS-2B cells". Thesis, Littoral, 2019. http://www.theses.fr/2019DUNK0547.
Abstract (sommario):
La pollution de l'air et les particules fines (PM₂.₅) ont été classées cancérigènes (groupe 1) par le Centre International de la Recherche sur le Cancer en 2013. Cette fraction particulaire représente un mélange complexe dont la composition, très variable, influe sur la toxicité. Cependant, peu d'études ont déterminé l'implication respective des différentes fractions chimiques constitutives des PM dans leurs effets toxiques. Dans ce travail de thèse, des particules fines (PM₂.₅₋₀.₃) et quasi-ultrafines (PM₀.₃) ont été échantillonnées au niveau d'un site urbain à Beyrouth (Liban). Après avoir réalisé la caractérisation physico-chimique de ces deux types de particules, leurs effets toxiques (cytotoxicité globale, activation métabolique, génotoxicité, inflammation, stress oxydant, autophagie et apoptose) ont été étudiés sur une lignée de cellules épithéliales bronchiques humaines (BEAS-2B). L'analyse des fractions organiques a révélé des différences entre les teneurs en hydrocarbures aromatiques polycycliques (HAP), de même qu'en congénères oxygénés (O-HAP) et nitrés (N-HAP), respectivement 43, 17 et 4 fois plus élevées dans les PM₀.₃ que dans les PM₂.₅₋₀.₃. L'étude toxicologique a porté sur les particules fines considérées dans leur entièreté (PM₂.₅₋₀.₃), la fraction organique extractible (EOM₂.₅₋₀.₃) et la fraction non-extractible par le dichlorométhane (NEM₂.₅₋₀.₃). De plus, les effets spécifiques de la fraction organique extraite des particules quasi-ultrafines (EOM₀.₃) ont été comparés à ceux de la fraction organique extraite des particules fines (EOM₂.₅₋₀.₃). Nos résultats montrent que chacune des fractions considérées a été capable d'activer au moins un des mécanismes étudiés. Les PM₂.₅₋₀.₃ ont induit des effets toxiques généralement plus marqués que les EOM₂.₅₋₀.₃ et NEM₂.₅₋₀.₃. La fraction organique des particules quasi-ultrafines (EOM₀.₃), plus riche en composés organiques et notamment en HAP et autres congénères, est apparue responsable d'effets délétères globalement plus importants que celle extraite des particules fines (EOM₂.₅₋₀.₃). Les résultats de ce travail ont apporté des éléments nouveaux sur la toxicité relative des différentes fractions extractibles et non extractibles des particules fines et soulignent le rôle crucial joué par les particules ultrafines, encore trop peu étudiéesAir pollution and particulate matter (PM₂.₅) were classified as carcinigens (group 1) by the International Agency for Research on Cancer in 2013. This particulate fraction represents a complex mixture with a highly variable composition influencing the toxicity. However, few studies have determined the respective involvement of the different chemical fractions of PM in their toxic effects. In this work, fine particles (PM₂.₅₋₀.₃) and quasi-ultrafine particles (PM₀.₃) were sampled in an urban site located in Beirut (Lebanon). After performing the physicochemical characterization of these two types of particles, their toxic effects (global cytotoxicity, metabolic activation, genotoxicity, inflammation, oxidative stress, autophagy and apoptosis) were investigated on a human bronchial epithelial cell line (BEAS-2B). The analysis of the organic content revealed differences between the concentrations of polycyclic aromatic hydrocarbons (PAHs), as welle as oxygenated (O-PAH) and nitrated (N-PAH) congeners, respectively 43, 17 and 4 times higher in PM₀.₃ than in PM₂.₅₋₀.₃.The toxicological study was based on the comparison of the toxicity of the fine particles considered in their entirety (PM₂.₅₋₀.₃), the extracted organic fraction (OEM₂.₅₋₀.₃) and the fraction not extracted by the dichloromethane (NEM₂.₅₋₀.₃). In addition, the specific effects of the organic fraction extrated from the quasi-ultrafine particles (OEM₀.₃) were compared with those of the organic fraction extracted from the fine particles (OEM₂.₅₋₀.₃). Our results showed that all the studied fractions were able to induce at least one of the studied mechanisms. PM₂.₅₋₀.₃ was able to induce toxic effects greater than those induced by OEM₂.₅₋₀.₃ and NEM₂.₅₋₀.₃. The organic fraction extracted from the quasi-ultrafine particles (OEM₀.₃), richer in organic compounds and in particular in PAHs and other congeners, appeared to be responsible for deleterious effects globally greater than that extracted from the fine particles (OEM₂.₅₋₀.₃). The results of this work have brought new elements on the relative toxicity of the different fractions of the fine particles and underline the crucial role played by ultrafine particles, still too little studied
39
Teixeira, Fernanda de Sá. "Implantação iônica de baixa energia em polímero para desenvolvimento de camadas compósitas nanoestruturadas condutoras litografáveis". Universidade de São Paulo, 2010. http://www.teses.usp.br/teses/disponiveis/3/3140/tde-23082010-103839/.
Abstract (sommario):
Eletrônica utilizando polímero em substituição ao silício é uma área de pesquisa recente com perspectivas econômicas promissoras. Compósitos de polímeros com partículas metálicas apresentam interessantes propriedades elétricas, magnéticas e ópticas e têm sido produzidos por uma grande variedade de técnicas. Implantação iônica de metais utilizando plasma é um dos métodos utilizados para obtenção desses compósitos condutores. Neste trabalho é realizada implantação de íons de ouro de baixa energia em PMMA utilizando plasma. O PMMA tem grande importância tecnológica sendo largamente utilizado como resiste em litografias por feixe de elétrons, raios-X, íons e deep-UV. Como resultado da implantação iônica de baixa energia em PMMA há formação de uma camada nanométrica de material condutor. Esse novo material, denominado compósito isolante-condutor, permite criar micro e nanodispositivos através de técnicas largamente utilizadas em microeletrônica. Medidas elétricas são realizadas in situ em função da dose de íons metálicos implantada, o que permite um estudo das propriedades de transporte desses novos materiais, que podem ser modeladas pela teoria da percolação. Simulações utilizando o programa TRIDYN permitem obter a profundidade e o perfil da implantação dos íons. São mostradas caracterizações importantes tais como Microscopia Eletrônica de Transmissão, Microscopia de Varredura por Tunelamento, Espalhamento de Raios-X a Baixos Ângulos, Difração de Raios-X e Espectroscopia UV-vis. Essas técnicas permitem visualizar e investigar o caráter nanoestruturado do compósito metal-polímero. Ainda como parte deste projeto, as camadas condutoras formadas no polímero são caracterizadas quanto à manutenção das suas características de elétron resiste.Electronics using polymers instead of silicon is a recent research area with promising economic perspectives. Polymer with metallic particles composites presents interesting electrical, magnetic and optical properties and they have been produced by a broad variety of techniques. Metal ion implantation using plasma is one of the used methods to obtain conductor composites. In this work it is performed low energy gold ion implantation in PMMA by using plasma. PMMA has great technological importance once it is broadly used as resist in electron-beam, X-ray, ion and deep UV lithography. As a result of low energy ion implantation in PMMA, a nanometric conducting layer is formed. This new material, named insulator-conductor composite, can allow the creation of micro and nanodevices through well known microelectronics techniques. Electrical measurements are performed in situ as a function of metal ions implanted dose, which allows the investigation of electrical transport of these new materials, which can be modeled by the percolation theory. Simulations using TRIDYN computer code provide the prediction of depth profile of implanted ions. Important characterizations are showed such as Transmission Electron Microscopy, Scanning Tunneling Microscopy, Small Angle X-Ray Scattering, X-Ray Diffraction and UV-vis Spectroscopy. These techniques allow to visualize and to investigate the nanostructured character of the metal-polymer composite. Still as a part of this project, the conducting layers formed are characterized in relation to the maintenance of their characteristics as electron-beam resist.
40
Casimirius, Stéphane. "Croissance localisée de nanotubes de carbone aux échelles micrométrique et nanométrique". Phd thesis, Université Paul Sabatier - Toulouse III, 2006. http://tel.archives-ouvertes.fr/tel-00136052.
Abstract (sommario):
La réalisation de dispositifs nanotechnologiques comportant des nanotubes de carbone (NTC) repose essentiellement sur l'intégration contrôlée des NTC sur substrat. Nous avons développé cette thématique en choisissant, plutôt que la manipulation de NTC synthétisés, l'approche de la croissance localisée de NTC par dépôt chimique catalytique en phase vapeur (CCVD) sous mélange de gaz H2-CH4. Nos travaux nous ont permis de synthétiser sélectivement des NTC à partir de sites catalytiques définis, sur des substrats de silicium. Notre étude a porté sur la synthèse de NTC à partir de dépôts de nanoparticules (NP) catalytiques de cobalt préparées selon trois voies distinctes : formation in situ de NP sur support oxyde par réduction sélective de la solution solide Mg0,95Co0,05O préparée par voie sol-gel ; NP de Co préformées par voie chimique, déposées directement sur un substrat SiO2/Si ; NP formées par le recuit de couche mince métallique Co également déposée sur substrat SiO2/Si. Nous avons démontré que la CCVD sous CH4 pur ou sous mélange H2-CH4, avec montée en température sous gaz inerte, aboutit à la formation de NTC dès 850°C, à partir de dépôts catalytiques non structurés. En particulier, le choix du système catalytique adéquat permet (1) de produire des films denses de NTC (environ 1 NTC/µm²) ; (2) de favoriser la formation de NTC mono- ou biparois, dont le diamètre est généralement compris entre 0,8 et 4 nm, et la longueur de l'ordre de quelques dizaines de µm. Des techniques de structuration ont été développées dans le but de localiser les dépôts de NP catalytiques. Le tamponnage (technique de lithographie molle) d'un précurseur catalytique liquide (sol ou suspension de NP Co) à l'aide d'un timbre apparaît comme une technique adéquate pour la production de motifs catalytiques micrométriques (1 - 100 µm). En revanche, la lithographie électronique associée au dépôt en couche mince (lift-off) demeure l'outil privilégié pour localiser des motifs catalytiques de dimensi ons nanométriques (jusqu'à 50 nm) par rapport aux structures prédéfinies du substrat de silicium. Nos travaux démontrent l'adéquation de la croissance localisée pour la production de motifs de NTC avec un certain contrôle de la densité surfacique des NTC, compatible avec la formation d'interconnexions entre motifs voisins. La dimension ultime des motifs produits varie entre 50 nm et 100 µm, selon la nature du catalyseur et de la technique de structuration employée. Notre étude ne met pas en évidence l'influence nette de l'organisation des motifs catalytiques sur l'orientation des NTC, qui reste majoritairement aléatoire à la surface des substrats SiO2/Si, et ce quelle que soit la nature du catalyseur mis en Suvre.
41
Cao, Shuiyan. "Using plasmonic nanostructures to control electrically excited light emission". Thesis, Université Paris-Saclay (ComUE), 2018. http://www.theses.fr/2018SACLS042/document.
Abstract (sommario):
Dans cette thèse, nous utilisons différentes nanostructures plasmoniques pour contrôler l'émission de lumière excitée électriquement. Notre émission électrique provient d'une "nanosource STM" qui utilise le courant tunnel inélastique entre la pointe d'un microscope à effet tunnel (STM) et un échantillon métallique, pour exciter localement les plasmons polaritons de surface localisés et propagatifs. L’interaction de notre nanosource STM et d'une lentille plasmonique circulaire (une série de fentes concentriques gravées dans un film d'or épais) produit une microsource radialement polarisée de faible dispersion angulaire (≈ ± 4 °). L'influence des paramètres structuraux sur la propagation angulaire de la microsource résultante est également étudiée. En outre, une faible dispersion angulaire (<± 7 °) pour une grande plage de longueurs d'onde (650-850 nm) est obtenue. Ainsi, cette microsource électrique de lumière presque collimatée a une réponse spectrale large et est optimale sur une large plage d'énergie, en particulier en comparaison avec d'autres structures plasmoniques résonantes telles que les nanoantennes Yagi-Uda. L'interaction de notre nanosource STM et d'une lentille plasmonique elliptique (une seule fente elliptique gravée dans un film d'or épais) est également étudiée. Lorsque l'excitation STM est située au point focal de la lentille plasmonique elliptique, un faisceau lumineux directionnel à faible divergence est acquis. De plus, expérimentalement, nous trouvons qu'en changeant l'excentricité de la lentille plasmique elliptique, l'angle d'émission varie. On constate que plus l'excentricité de la lentille elliptique est grande, plus l'angle d'émission est élevé. Cette étude permet de mieux comprendre comment les nanostructures plasmoniques façonnent l'émission de lumière. L'interaction de SPP excités par STM et d'une structure de pile multicouche planaire plasmonique est également étudiée. Il est démontré qu'en utilisant l'excitation STM, nous pouvons sonder la structure de bande optique de la pile Au-SiO₂-Au. Nous trouvons que l'épaisseur du diélectrique joue un rôle important dans la modification du couplage entre les modes. Nous comparons également les résultats obtenus par excitation laser et STM de la même structure de pile. Les résultats indiquent que la technique STM est supérieure en sensibilité. Ces résultats mettent en évidence le potentiel de la STM en tant que technique de nanoscopie optique sensible pour sonder les bandes optiques des nanostructures plasmoniques. Enfin, l'interaction d'une nanosource STM et d'une plaque triangulaire individuelle est également étudiée. Nous trouvons que lorsque l'excitation STM est centrée sur la plaque triangulaire, il n'y a pas d'émission de lumière directionnelle. Cependant, lorsque la nanosource STM est située sur le bord du triangle, on obtient une émission de lumière directionnelle. Cette étude nous fournit une nouvelle voie pour atteindre l'émission de lumière directionnelle. Nous étudions également l'exploration du LDOS optique du triangle avec la nanosource STM. Ainsi, nos résultats montrent que la manipulation de la lumière est réalisée par des interactions SPP-matière. En utilisant des nanostructures plasmoniques, nous contrôlons la collimation, la polarisation et la direction de la lumière provenant de la nanosource STMIn this thesis, we use different plasmonic nanostructures to control the emission of electrically-excited light. Our electrical emission is from an “STM-nanosource” which uses the inelastic tunnel current between the tip of a scanning tunneling microscope (STM) and a metallic sample, to locally excite both localized and propagating surface plasmon polaritons. The interaction of our STM-nanosource and a circular plasmonic lens (a series of concentric slits etched in a thick gold film) produces a radially polarized microsource of low angular spread (≈±4°). The influence of the structural parameters on the angular spread of the resulting microsource is also investigated. In addition, a low angular spread (<±7°) for a large wavelength range (650-850 nm) is achieved. Thus this electrically-driven microsource of nearly collimated light has a broad spectral response and is optimal over a wide energy range, especially in comparison with other resonant plasmonic structures such as Yagi-Uda nanoantennas. The interaction of our STM-nanosource and an elliptical plasmonic lens (a single elliptical slit etched in a thick gold film) is also studied. When the STM excitation is located at the focal point position of the elliptical plasmonic lens, a directional light beam of low angular spread is acquired. Moreover, in the experiment we find that by changing the eccentricity of the elliptical plasmonic lens, the emission angle is varied. It is found that the larger the eccentricity of the elliptical lens, the higher the emission angle. This study provides a better understanding of how plasmonic nanostructures shape the emission of light. The interaction of STM-excited SPPs and a planar plasmonic multi-layer stack structure is also investigated. It is demonstrated that using STM excitation we can probe the optical band structure of the Au-SiO₂-Au stack. We find that the thickness of the dielectric plays an important role in changing the coupling between the modes. We also compare the results obtained by both laser and STM excitation of the same stack structure. The results indicate that the STM technique is superior in sensitivity. These findings highlight the potential of the STM as a sensitive optical nanoscopic technique to probe the optical bands of plasmonic nanostructures. Finally, the interaction of an STM-nanosource and an individual triangular plate is also studied. We find that when the STM excitation is centered on the triangular plate, there is no directional light emission. However, when the STM-nanosource is located on the edge of the triangle, directional light emission is obtained. This study provides us a novel avenue to achieve directional light emission. We also study probing the optical LDOS of the triangle with the STM-nanosource. Thus, our results show that the manipulation of light is achieved through SPP-matter interactions. Using plasmonic nanostructures, we control the collimation, polarization, and direction of the light originating from the STM-nanosource
42
Johannessen, Bernt. "Ion beam formation and modification of metallic nanoparticles". Phd thesis, 2007. http://hdl.handle.net/1885/150441.
43
Sprouster, David John. "Ion beam formation and modification of Cobalt nanoparticles". Phd thesis, 2010. http://hdl.handle.net/1885/150492.
Abstract (sommario):
This thesis has investigated the structural and vibrational properties of ion beam synthesized Co nanoparticles (NPs) and the influence of ion irradiation on the size, shape, crystallographic phase and structure. The evolution of the aforementioned properties were determined using a combination of laboratory and synchrotron based techniques, including cross-sectional transmission electron microscopy (TEM), small-angle X-ray scattering (SAXS) and X-ray absorption spectroscopy (XAS). The results of this thesis have revealed a rich array of shape and structural transformations in Co NPs and highlights the effectiveness of a combined ion implantation/ion irradiation procedures in controlling and tuning the NP size, shape, crystallographic phase and structure. The structural and vibrational properties of Co NPs embedded in Si0{u2082}, formed by ion implantation were investigated as a function of the implantation concentration and post implantation annealing conditions. The implantation concentration and annealing temperature governed the spherical NP size and phase. X-ray absorption near-edge spectroscopy (XANES) was used to quantify the RCP, FCC and oxide fractions. The structural properties were characterized by extended X-ray absorption fine structure spectroscopy (EXAFS) and finite-size effects were readily apparent. With a decrease in NP size, an increase in structural disorder and a decrease in both the coordination number and bondlength were observed. The surface tension of Co NPs calculated using a liquid drop model was more than twice that of bulk material. The size-dependent vibrational properties were probed with temperature-dependent XAS measurements. Using a correlated anharmonic Einstein model and thermodynamic perturbation theory, Einstein temperatures for both NPs and bulk material were determined. Compared to bulk Co, the mean vibrational frequency of the smallest NPs was reduced as attributed to a greater influence of loosely-bonded, under-coordinated surface atoms relative to the effect of capillary pressure generated by surface curvature. Elemental Co NPs embedded in Si0{u2082} were irradiated with low energy Au ions and the evolution of the NP size and structure were then studied as a function of ion fluence. Upon irradiation, SAXS and TEM show that there was no change in the average NP size, in contrast to the short and long-range order where significant changes were observed. The coordination number decreased further while the mean value (bondlength), variance (Debye-Waller factor) and asymmetry (third cumulant) of the interatomic distance distribution all increased, as consistent with theoretical predictions for an amorphous elemental metal. Furthermore, the experimentally determined interatomic distance distribution for the irradiated Co NPs were in excellent agreement with molecular dynamics simulations for bulk amorphous Co and the observed structural changes were thus attributed to the formation of an amorphous phase. Such a crystalline-to-amorphous phase transformation is not readily achievable in bulk material (or large Co NPs) and the perturbed structural state prior to irradiation and the amorphous host matrix both contribute to nucleating and stabilising the amorphous phase in irradiated Co NPs. The Einstein temperature calculated from temperature-dependent XAS measurements for the unirradiated NPs showed a decrease in Einstein temperature. In contrast, that of the irradiated amorphous NPs was substantially higher than the bulk value. this apparent bond stiffening is attributed to the influence of the rigid surrounding matrix. When subjected to swift heavy ion irradiation, embedded FCC Co NPs were found to rapidly transform at low fluence to the HCP phase prior to any changes in size or shape. The crystallographic phase was identified with XAS and electron diffraction and quantified, as functions of the irradiation energy and fluence, with the former. The transformation was complete at low fluence and was governed by the electronic-energy-loss of the incident ions. A direct-impact mechanism was identified with the transformation interaction cross-section correlated with that of a molten ion track in amorphous Si0{u2082}. The swift heavy-ion irradiation-induced phase transformation was attributed to the large shear stress resulting from the rapid thermal expansion about an ion track in the Si0{u2082}. The size, shape and structural evolution of embedded Co NPs subject to high fluence swift heavy ion irradiation were also investigated over a wide energy region. Various electronic-energy-loss-dependent shape and structural changes in the Co NPs were observed. Depending on the irradiation energy, NPs below 4-7 nm remained spherical in shape and progressively decreased in size with fluence due to dissolution. NPs with sizes above a threshold diameter readily transformed into ellipsoids with their major dimension parallel to the incident ion beam direction. Modifications of the atomic-scale structure were characterised with XAS. Prior to irradiation, all Co atoms were in a metallic state. After SHIl, however, Co atoms were found in different atomic environments including: large elongated NPs, small spherical NPs and a large fraction of isolated Co atoms bonded to O in the matrix. The work presented in this thesis has resulted in the identification and understanding of a number of fundamental and technologically important effects in the formation and irradiation of Co NPs embedded in a Si0{u2082} matrix. Results demonstrate that the the size, shape and structure of Co NPs formed by ion implantation and thermal annealing in Si0{u2082} can be readily controlled by ion irradiation. This methodology represents an effective means of controlling the NP properties to best suit specific technological applications.
44
"Synthesis and laser light scattering studies of linear polymer chains and polymeric nanoparticles". 2001. http://library.cuhk.edu.hk/record=b5890650.
Abstract (sommario):
Lau Chin Wa.Thesis (M.Phil.)--Chinese University of Hong Kong, 2001.
Includes bibliographical references (leaves 77-78).
Abstracts in English and Chinese.
Abstract --- p.i
Chinese Abstract --- p.ii
Acknowledgement --- p.iv
Contents --- p.v
Abbreviations --- p.viii
List of Figures --- p.xiv
List of Tables --- p.xviii
Chapter Chapter 1 --- Introduction --- p.1
Chapter Chapter 2 --- Basic Principle of Laser Light Scattering and Instrumentation --- p.7
Chapter 2.1 --- Static laser light scattering (Static LLS) --- p.8
Chapter 2.2 --- Dynamic laser light scattering (Dynamic LLS) --- p.9
Chapter 2.3 --- Calibration between translational diffusion coefficient D and molar mass M --- p.10
Chapter 2.3.1 --- Tranform G(D) to Molar Mass Distributionfw(M) --- p.10
Chapter 2.3.2 --- Calibration between D and M- Using a set of narrowly distributed standards --- p.12
Chapter 2.3.3 --- Calibration between D and M- Using two or more broadly distributed samples --- p.12
Chapter 2.4 --- Data Analysis --- p.14
Chapter 2.5 --- References --- p.16
Chapter Chapter 3 --- Experimental --- p.17
Chapter 3.1 --- Laser Light Scattering Instrumentation --- p.17
Chapter 3.1.1 --- Overview of laser light scattering spectrometer --- p.17
Chapter 3.1.2 --- Differential Refractometer --- p.18
Chapter 3.2 --- References --- p.21
Chapter Chapter 4 --- Thermally Sensitive and Biocompatible Poly(N-vinylcaprolactam): Synthesis and Characterization of High Molar Mass Linear Chains
Chapter 4.1 --- Introduction --- p.22
Chapter 4.2 --- Sample Preparation --- p.23
Chapter 4.3 --- Results and discussion --- p.24
Chapter 4.4 --- Conclusion --- p.27
Chapter 4.5 --- References --- p.29
Chapter Chapter 5 --- Stabilization and destabilization of potassium persulfate (as an initiator) in an surfactant-free water/acetone mixture emulsion polymerization of styrene under microwave irradiation
Chapter 5.1 --- Introduction --- p.41
Chapter 5.2 --- Experimental --- p.43
Chapter 5.3 --- Results and discussion --- p.44
Chapter 5.4 --- Conclusion --- p.51
Chapter 5.5 --- References --- p.53
Appendix
Chapter A.l --- Static Laser Light Scattering --- p.66
Chapter A.1.1 --- Scattering from a small particles --- p.66
Chapter A.1.2 --- Scattering from a large particles --- p.67
Chapter A.1.3 --- Scattering by solutions of small molecules --- p.69
Chapter A.1.3.1 --- Scattering from polymer solutions --- p.70
Chapter A.2 --- Dynamic laser light scattering --- p.71
Chapter A.2.1 --- Line-width measurement --- p.73
Chapter A.2.2 --- Data analysis --- p.75
45
"Studies on nanobubbles in aqueous solutions". Thesis, 2007. http://library.cuhk.edu.hk/record=b6074438.
Abstract (sommario):
Chapter 1 briefly introduces the background, problems, applications as well as recent progress of the nanobubbles research. The relationship between the formation/stabilization of nanobubbles and the long-rang structures of water molecules, particularly the restructuring of water molecules at the water/gas interface, are emphasized.Chapter 2 introduces the theories of static and dynamic light scattering and Zeta-potential measurements as well as the details of the instrument set-up. In this chapter, the fundamental equations of the scattering theory are figured out basis on the quasi-classical electrodynamics and combination of the statistical mechanics as well as molecular dynamic theory. Finally, the statistical properties of photon counting are discussed.
In chapter 3, aqueous solutions of tetrahydrofuran, ethanol, urea and alpha-cyclodextrin were studied by a combination of static and dynamic laser light scattering (LLS). In textbooks, these small organic molecules are soluble in water so that there should be no observable large structures or density fluctuation in either static or dynamic LLS. However, a slow mode has been consistently observed in these aqueous solutions in dynamic LLS. Such a slow mode was previously attributed to some large complexes or supramolecular structures formed between water and these small organic molecules, Our current study reveals that it is actually due to the existence of small bubbles (∼100 nm in diameter) formed inside these solutions. Our direct evidence comes from the fact that it can be removed by repeated filtration and regenerated by air purging. Our results also indicate that the formation of such nanobubbles in small organic molecules aqueous solutions is a universal phenomenon. Such formed nanobubbles are rather stable. The measurement of isothermal compressibility confirms the existence of a low density micro-phase, presumably nanobubbles, in these aqueous solutions. Using a proposed structural model, i.e., each bubble is stabilized by small organic molecules adsorbed at the gas/water interface, we have, for the first time, estimated the pressure inside these nanobubbles.
In chapter 4, by using a combination of laser light scattering (LLS) and zeta-potential measurements, we investigated effects of salt concentration and pH on stability of the nanobubbles in alpha-cyclodextrin (alpha-CD) aqueous solutions. Our LLS results reveal that the nanobubbles are unstable in solutions with a higher ionic strength, just like colloidal particles in an aqueous dispersion, but become more stable in alkaline solutions. The zeta-potential measurement shows that the nanobubbles are negatively charged with an electric double layer, presumably due to the adsorption of negative OTT ions at the gas/water interface. It is this double layer that plays dual roles in the formation of stable nanobubbles in aqueous solutions of water-soluble organic molecules; namely, it not only provides a repulsive force to prevent the inter-bubble aggregation and coalescence, but also reduces the surface tension at the gas/water interface to decreases the internal pressure inside each bubble.
In chapter 5, the addition of salt can induce slow coalescence of nanobubbles (∼100 nm) in an aqueous solution of alpha-cyclodextrin (alpha-CD). A combination of static and dynamic laser light scattering was used to follow the coalescence. Our results reveal that its kinetic and structural properties follow some scaling laws; namely, the average size (<zeta>) of nanobubbles is related to their average mass (<M>) and the coalescence time (t) as <M> <zeta>dr and <zeta> ∼ tgamma with two salt-concentration dependent scaling exponents (df and gamma) For a lower sodium chloride concentration (C NaCl = 40 mM), gamma = 0.13 +/- 0.01 and df = 1.71 +/- 0.02. The increase of CNaCl to 80 mM results in gamma = 0.32 +/- 0.01 and df = 1.99 +/- 0.01. The whole process has two main stages: the aggregation and the coalescence. At the lower C NaCl, the process essentially stops in the aggregation stage with some limited coalescence. At higher CNaCl leads the coalescence after the aggregation and results in large bubbles.
In this thesis, the nanobubbles in the aqueous solutions have been studied by using combination of static and dynamic laser light scattering (LLS), isothermal compressibility measurements and Zeta-potential measurements. We found that the nanobubbles extensively exist in aqueous solutions and the interface of each nanobubble is negatively charged. The addition of electrolytes can destabilize such interface to induce the coalescence of nanobubbles.
Jin, Fan.
"Aug 2007."
Adviser: Chi Wu.
Source: Dissertation Abstracts International, Volume: 69-02, Section: B, page: 1030.
Thesis (Ph.D.)--Chinese University of Hong Kong, 2007.
Includes bibliographical references (p. 108).
Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web.
Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web.
Abstract in English and Chinese.
School code: 1307.
46
LIN, YONG-FENG, e 林湧峰. "Green Synthesis of Silver Nanoparticles Using Mung Beans Soaking Medium". Thesis, 2016. http://ndltd.ncl.edu.tw/handle/n528ns.
Abstract (sommario):
碩士國立高雄應用科技大學
化學工程與材料工程系碩士在職專班
104
The preparation of silver nanoparticles using mungbean soaking solution as the reducing agent was reported in this study. First, the effect of mungbean soaking condition on the formation of silver nanoparticles was examined. As compared to the germination mungbean, the soaking solution from non-germination mungbeam showed a higher reducing ability. The formation rate of silver nanoparticles was affected by the soaking time of mungbean. It was found that the formation rate of silver nanoparticles in mungbean soaking solution could be attributed to a higher concentration phytic acid releasing from mungbean. Since phytic acid could be degraded by the phytase from soaking mungbean, the mungbean soaking solution was boiled from 30 min for inactivating phytase. The results indicated that the formation rate of silver nanoparticles was further improved in boiled mungbean soaking solution. Phytic acid could be used as a natural reducing agent for synthesizing metal nanoparticles. The process of increasing the phytic acid concentration from plants would improving the formation of metal nanoparticles.
47
Sanyal, Udishnu. "Modulation of Nanostructures in the Solid and Solution States and under an Electron Beam". Thesis, 2013. http://etd.iisc.ernet.in/2005/3303.
Abstract (sommario):
Among various nanomaterials, metal nanoparticles are the widely studied ones because of their pronounced distinct properties arising in the nanometer size regime, which can be tailored easily by tuning predominantly their size and shape. During the past few decades, scientists are engaged in developing new synthetic methodologies for the synthesis of metal nanoparticles which can be divided into two broad categories: i) top-down approach, utilizing physical methods and ii) bottom-up approach, employing chemical methods. As the chemical methods offer better control over particle size, numerous chemical methods have been developed to obtain metal nanoparticles with narrow size distribution. However, these two approaches have their own merits and demerits; they are not complementary to each other and also not sustainable for real time applications. Recent focus on the synthesis of metal nanoparticles is towards the development of green and sustainable synthetic methodologies. A solid state route is an exciting prospect in this direction because it eliminates usage of organic solvents thus, makes the overall process green and at the same time leads to the realization of large quantity of the materials, which is required for many applications. However, the major obstacle associated with the development of a solid state synthetic route is the lack of fundamental understanding regarding the formation mechanism of the nanoparticles in the solid state. Additionally, due to the heterogeneity present in the solid mixture, it is very difficult to ensure the proximity between the capping agent and nuclei which plays the most decisive role in the growth process. Recently, employment of amine–borane compounds as reducing agents emerged as a better prospect towards the development of sustainable synthetic routes for metal nanoparticles because they offer a variety of advantages over the traditional borohydrides. Being soluble in organic medium, amine– borane allows the reaction to be carried out in a single phase and due to its mild reducing ability a much better control over the nucleation and growth processes is realized. However, the most exciting feature of these compounds is that their reducing ability is not only limited to the solution state, they can also bring out the reduction of metal ions in the solid state.
With the availability of a variety of amine–boranes of varying reducing ability, it opens up a possibility to modulate the nanostructure in both solid and solution states by a judicious choice of reducing agent. Although our current understanding regarding the growth behavior of nanoparticles has advanced remarkably, however, most often it is some classical model which is invoked to understand these processes. With the recent developments in in situ transmission electron microscopy techniques, it is now possible to unravel more complex growth trajectories of nanoparticles. These studies not only expand the scope of the present knowledge but also opens up possibilities for many future developments. Objectives
• To develop an atom economy solid state synthetic methodology for the synthesis of metal nanoparticles employing amine–boranes as reducing agents.
• To gain a mechanistic insight into the formation mechanisms of nanoparticles in the solid state by using amine–boranes with differing reducing ability.
• Synthesis of bimetallic nanoparticles as well as supported metal nanoparticles in the solid state using ammonia borane as the reducing agent.
• To develop a new in situ seeding growth methodology for the synthesis of core@shell nanoparticles composed of noble metals by employing a very weak reducing agent, trimethylamine borane and their transformation to their thermodynamically stable alloy counterparts.
• Synthesis of highly monodisperse ultra-small colloidal calcium nanoparticles with different capping agents such as hexadecylamine, octadecylamine, poly(vinylpyrrolidone) and a combination of hexadecylamine/poly(vinylpyrrolidone) using the solvated metal atom dispersion (SMAD) method. To study the coalescence behavior of a pair of calcium nanoparticles under an electron beam by employing in situ TEM technique.
Significant results
An atom economy solid state synthetic route has been developed for the synthesis of metal nanoparticles from simple metal salts using amine–boranes as reducing agents. Amine–borane plays a dual role here: acts as a reducing agent thus brings out the reduction of metal ions and decomposes simultaneously to generate B-N based compounds which acts as a capping agent to stabilize the particles in the nanosize regime. This essentially minimizes the
number of reagents used and hence simplifying and eliminating the purification procedures and thus, brings out an atom economy to the overall process. Additionally, as the reactions were carried out in the solid state, it eliminates use of organic solvents which have many adverse effects on the environment, thus makes the synthetic route, green. The particle size and the size distribution were tuned by employing amine–boranes with differing reducing abilities. Three different amine–boranes have been employed: ammonia borane (AB), dimethylamine borane (DMAB), and trimethylamine borane (TMAB) whose reducing ability varies as AB > DMAB >> TMAB. It was found that in case of AB, it is the polyborazylene or BNHx polymer whereas, in case of DMAB and TMAB, the complexing amines act as the stabilizing agents. Several controlled studies also showed that the rate of addition of metal salt to AB is the crucial step and has a profound effect on the particle size as well as the size distribution. It was also found that an optimum ratio of amine–borane to metal salt is important to realize the smallest possible size with narrowest size distribution. Whereas, use of AB and TMAB resulted in the smallest sized particles with best size distribution, usage of DMAB provided larger particles that are also polydisperse in nature. Based on several experiments along with available data, the formation mechanism of metal nanoparticles in the solid state has been proposed. Highly monodisperse Cu, Ag, Au, Pd, and Ir nanoparticles were realized using the solid state route described herein. The solid state route was extended to the synthesis of bimetallic nanoparticles as well as supported metal nanoparticles. Employment of metal nitrate as the metal precursor and ammonia borane as the reducing agent resulted in highly exothermic reaction. The heat evolved in this reaction was exploited successfully towards mixing of the constituent elements thus allowing the alloy formation to occur at much lower temperature (60 oC) compared to the traditional solid state metallurgical methods (temperature used in these cases are > 1000 oC). Synthesis of highly monodisperse 2-3 nm Cu/Au and 5-8 nm Cu/Ag nanoparticles were demonstrated herein. Alumina and silica supported Pt and Pd nanoparticles have also been prepared. Use of ammonia borane as the reducing agent in the solid state brought out the reduction of metal ions to metal nanoparticles and the simultaneous generation of BNHx polymer which encapsulates the metal (Pt and Pd) nanoparticles supported on support materials. Treatment of these materials with methanol resulted in the solvolysis of BNHx polymer and its complete removal to finally provide metal nanoparticles on the support materials.
An in situ seeding growth methodology for the synthesis of bimetallic nanoparticles with core@shell architecture composed of noble metals has been developed using trimethylamine borane (TMAB) as the reducing agent. The key idea of this synthetic procedure is that, TMAB being a weak reducing agent is able to differentiate the smallest possible window of reduction potential and hence reduces the metal ions sequentially. A dramatic solvent effect was noted in the preparation of Ag nanoparticles: Ag nanoparticles were obtained at room temperature when dry THF was used as the solvent whereas, reflux condition was required to realize the same using wet THF as the solvent. However, no such behavior was noted in the preparation of Au and Pd nanoparticles wherein Au and Pd nanoparticles were obtained at room temperature and reflux conditions, respectively. This difference in reduction behavior was successfully exploited to synthesize Au@Ag, Ag@Au, and Ag@Pd nanoparticles. All these core@shell nanoparticles were further transformed to their alloy counterparts under very mild conditions reported to date. Highly monodisperse, ultrasmall, colloidal Ca nanoparticles with a size regime of 2-4 nm were synthesized using solvated metal atom dispersion (SMAD) method and digestive ripening technique. Hexadecylamine (HDA) was used as the stabilizing agent in this case. Employment of capping agent with a longer chain length, octadecylamine afforded even smaller sized particles. However, when poly(vinylpyrrolidone) (PVP), a branched chain polymer was used as the capping agent, agglomerated particles were realized together with small particles of 3-6 nm. Use of a combination of PVP and HDA resulted in spherical particles of 2-3 nm size with narrow size distribution. Growth of Ca nanoparticles via colaesence mechanism was observed under an electron beam. Employing in situ transmission electron microscopy technique, real time coalescence between a pair of Ca nanoparticles were detected and details of coalescence steps were analyzed.
48
Sanyal, Udishnu. "Modulation of Nanostructures in the Solid and Solution States and under an Electron Beam". Thesis, 2013. http://etd.iisc.ac.in/handle/2005/3303.
Abstract (sommario):
Among various nanomaterials, metal nanoparticles are the widely studied ones because of their pronounced distinct properties arising in the nanometer size regime, which can be tailored easily by tuning predominantly their size and shape. During the past few decades, scientists are engaged in developing new synthetic methodologies for the synthesis of metal nanoparticles which can be divided into two broad categories: i) top-down approach, utilizing physical methods and ii) bottom-up approach, employing chemical methods. As the chemical methods offer better control over particle size, numerous chemical methods have been developed to obtain metal nanoparticles with narrow size distribution. However, these two approaches have their own merits and demerits; they are not complementary to each other and also not sustainable for real time applications. Recent focus on the synthesis of metal nanoparticles is towards the development of green and sustainable synthetic methodologies. A solid state route is an exciting prospect in this direction because it eliminates usage of organic solvents thus, makes the overall process green and at the same time leads to the realization of large quantity of the materials, which is required for many applications. However, the major obstacle associated with the development of a solid state synthetic route is the lack of fundamental understanding regarding the formation mechanism of the nanoparticles in the solid state. Additionally, due to the heterogeneity present in the solid mixture, it is very difficult to ensure the proximity between the capping agent and nuclei which plays the most decisive role in the growth process. Recently, employment of amine–borane compounds as reducing agents emerged as a better prospect towards the development of sustainable synthetic routes for metal nanoparticles because they offer a variety of advantages over the traditional borohydrides. Being soluble in organic medium, amine– borane allows the reaction to be carried out in a single phase and due to its mild reducing ability a much better control over the nucleation and growth processes is realized. However, the most exciting feature of these compounds is that their reducing ability is not only limited to the solution state, they can also bring out the reduction of metal ions in the solid state.
With the availability of a variety of amine–boranes of varying reducing ability, it opens up a possibility to modulate the nanostructure in both solid and solution states by a judicious choice of reducing agent. Although our current understanding regarding the growth behavior of nanoparticles has advanced remarkably, however, most often it is some classical model which is invoked to understand these processes. With the recent developments in in situ transmission electron microscopy techniques, it is now possible to unravel more complex growth trajectories of nanoparticles. These studies not only expand the scope of the present knowledge but also opens up possibilities for many future developments. Objectives
• To develop an atom economy solid state synthetic methodology for the synthesis of metal nanoparticles employing amine–boranes as reducing agents.
• To gain a mechanistic insight into the formation mechanisms of nanoparticles in the solid state by using amine–boranes with differing reducing ability.
• Synthesis of bimetallic nanoparticles as well as supported metal nanoparticles in the solid state using ammonia borane as the reducing agent.
• To develop a new in situ seeding growth methodology for the synthesis of core@shell nanoparticles composed of noble metals by employing a very weak reducing agent, trimethylamine borane and their transformation to their thermodynamically stable alloy counterparts.
• Synthesis of highly monodisperse ultra-small colloidal calcium nanoparticles with different capping agents such as hexadecylamine, octadecylamine, poly(vinylpyrrolidone) and a combination of hexadecylamine/poly(vinylpyrrolidone) using the solvated metal atom dispersion (SMAD) method. To study the coalescence behavior of a pair of calcium nanoparticles under an electron beam by employing in situ TEM technique.
Significant results
An atom economy solid state synthetic route has been developed for the synthesis of metal nanoparticles from simple metal salts using amine–boranes as reducing agents. Amine–borane plays a dual role here: acts as a reducing agent thus brings out the reduction of metal ions and decomposes simultaneously to generate B-N based compounds which acts as a capping agent to stabilize the particles in the nanosize regime. This essentially minimizes the
number of reagents used and hence simplifying and eliminating the purification procedures and thus, brings out an atom economy to the overall process. Additionally, as the reactions were carried out in the solid state, it eliminates use of organic solvents which have many adverse effects on the environment, thus makes the synthetic route, green. The particle size and the size distribution were tuned by employing amine–boranes with differing reducing abilities. Three different amine–boranes have been employed: ammonia borane (AB), dimethylamine borane (DMAB), and trimethylamine borane (TMAB) whose reducing ability varies as AB > DMAB >> TMAB. It was found that in case of AB, it is the polyborazylene or BNHx polymer whereas, in case of DMAB and TMAB, the complexing amines act as the stabilizing agents. Several controlled studies also showed that the rate of addition of metal salt to AB is the crucial step and has a profound effect on the particle size as well as the size distribution. It was also found that an optimum ratio of amine–borane to metal salt is important to realize the smallest possible size with narrowest size distribution. Whereas, use of AB and TMAB resulted in the smallest sized particles with best size distribution, usage of DMAB provided larger particles that are also polydisperse in nature. Based on several experiments along with available data, the formation mechanism of metal nanoparticles in the solid state has been proposed. Highly monodisperse Cu, Ag, Au, Pd, and Ir nanoparticles were realized using the solid state route described herein. The solid state route was extended to the synthesis of bimetallic nanoparticles as well as supported metal nanoparticles. Employment of metal nitrate as the metal precursor and ammonia borane as the reducing agent resulted in highly exothermic reaction. The heat evolved in this reaction was exploited successfully towards mixing of the constituent elements thus allowing the alloy formation to occur at much lower temperature (60 oC) compared to the traditional solid state metallurgical methods (temperature used in these cases are > 1000 oC). Synthesis of highly monodisperse 2-3 nm Cu/Au and 5-8 nm Cu/Ag nanoparticles were demonstrated herein. Alumina and silica supported Pt and Pd nanoparticles have also been prepared. Use of ammonia borane as the reducing agent in the solid state brought out the reduction of metal ions to metal nanoparticles and the simultaneous generation of BNHx polymer which encapsulates the metal (Pt and Pd) nanoparticles supported on support materials. Treatment of these materials with methanol resulted in the solvolysis of BNHx polymer and its complete removal to finally provide metal nanoparticles on the support materials.
An in situ seeding growth methodology for the synthesis of bimetallic nanoparticles with core@shell architecture composed of noble metals has been developed using trimethylamine borane (TMAB) as the reducing agent. The key idea of this synthetic procedure is that, TMAB being a weak reducing agent is able to differentiate the smallest possible window of reduction potential and hence reduces the metal ions sequentially. A dramatic solvent effect was noted in the preparation of Ag nanoparticles: Ag nanoparticles were obtained at room temperature when dry THF was used as the solvent whereas, reflux condition was required to realize the same using wet THF as the solvent. However, no such behavior was noted in the preparation of Au and Pd nanoparticles wherein Au and Pd nanoparticles were obtained at room temperature and reflux conditions, respectively. This difference in reduction behavior was successfully exploited to synthesize Au@Ag, Ag@Au, and Ag@Pd nanoparticles. All these core@shell nanoparticles were further transformed to their alloy counterparts under very mild conditions reported to date. Highly monodisperse, ultrasmall, colloidal Ca nanoparticles with a size regime of 2-4 nm were synthesized using solvated metal atom dispersion (SMAD) method and digestive ripening technique. Hexadecylamine (HDA) was used as the stabilizing agent in this case. Employment of capping agent with a longer chain length, octadecylamine afforded even smaller sized particles. However, when poly(vinylpyrrolidone) (PVP), a branched chain polymer was used as the capping agent, agglomerated particles were realized together with small particles of 3-6 nm. Use of a combination of PVP and HDA resulted in spherical particles of 2-3 nm size with narrow size distribution. Growth of Ca nanoparticles via colaesence mechanism was observed under an electron beam. Employing in situ transmission electron microscopy technique, real time coalescence between a pair of Ca nanoparticles were detected and details of coalescence steps were analyzed.
49
Amolo, George Odhiambo. "Optical and electrical properties of ion beam modified materials". Thesis, 2008. http://hdl.handle.net/10539/5409.
50
Hsieh, Chang Lin, e 謝長霖. "Optical properties of ion-beam-synthesized Au nanoparticles in SiO2 matrix". Thesis, 2016. http://ndltd.ncl.edu.tw/handle/5e9esx.
Abstract (sommario):
碩士國立清華大學
核子工程與科學研究所
104
In recent years, gold (Au) nanoparticles have been synthesized by means of various methods and have received promising potential in optical and biomedical detection. Au nanoparticles contain some remarkable dimension-dependent optical properties due to surface plasmon resonance (SPR) in Au nanoparticles which causes strong absorption of the incident light in visible light regions. Since SPR in well-crystallized Au nanoparticles can enhance the local electromagnetic field, it is thus expected that a greater efficiency in the photoluminescence (PL), originating from oxygen deficiency centers (ODC), can be achieved in Au-implanted SiO2 matrix. In order to demonstrate the enhancement of PL, in this story, Au nanoparticles were formed in SiO2 film using ion beam synthesis and their optical and microstructural properties were also investigated as well. The results revealed that a clear absorption peak at approximately 520 nm was identified in the UV-Vis spectra and was attributed to SPR induced by Au nanoparticles in SiO2 film. The SPR of Au nanoparticles is also dependent on thermal treatment conditions, such as annealing gas, annealing temperature and annealing time. The Au nanoparticle-containing SiO2 film also displayed several distinctive peaks at approximately 310, 380, 450, and 600 nm in the PL spectra and were found to be associated with ODC-related defects and non-bridging oxygen hole centers (NBOHC) in SiO2 film. In addition, the PL peak intensities increase as annealing temperature increase, a finding contradictory to the defect recovery. The greatest PL emission was achieved when the Au-implanted SiO2 film was annealed at 1100 oC for 1 h under the nitrogen ambient. Therefore, the existence of Au nanoparticles in SiO2 film can induce SPR effects and enhance PL emission which was mainly due to defect dependent luminescence centers.