Дисертації з теми "ZnS nanoparticles"
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Curcio, Ana Laura [UNESP]. "Síntese e caracterização de materiais semicondutores nanoestruturados luminescentes à base de ZnS." Universidade Estadual Paulista (UNESP), 2016. http://hdl.handle.net/11449/138154.
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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)
Nanocristais tem sido extensivamente investigados nos últimos anos devido à sua ampla gama de aplicações em vários dispositivos tais como sensores, células solares, lasers, fotocatalisadores, fotodetectores, detectores de infravermelhos, diodos emissores de luz, materiais eletroluminescentes e outros materiais emissores de luz. Semicondutores nanocristalinos apresentam propriedades eletrônicas intermediárias entre aqueles de estrutura molecular e sólidos macrocristalinos, proporcionando uma ampla gama de aplicações. Entre estes materiais, o sulfeto de zinco (ZnS) puro ou dopado tem recebido notável atenção por causa de suas propriedades estruturais ópticas, versatilidade e potencial para várias aplicações tecnológicas. O ZnS é um típico semicondutor II-VI, com um gap direto de 3,6 eV à temperatura ambiente e aproximadamente 40 meV de energia de gap, sendo um bom material luminescente utilizado em telas, sensores e lasers. Como material de gap largo, o ZnS pode facilmente hospedar diferentes metais de transição como centros luminescentes. Entre estes íons de metais de transição para estruturas dopadas, os íons Cu2+e Mn2+ são atraentes pelas emissões de luz características e por apresentarem propriedades eficientes para aplicações como luminóforos. A inserção desses íons na estrutura do ZnS proporcionam defeitos que resultam em emissão no verde para os íons Cu2+e emissão no laranja para os íons Mn2+. Neste estudo, as amostras de ZnS pura e dopadas com Cu2+ e Mn2+ foram preparados pelo método solvotermal, que demonstra ser um processo eficaz para preparar nanopartículas. Uma vez preparadas, as estruturas das amostras nanoestruturadas foram caracterizadas e correlacionada s com propriedades fotoluminescentes. Os resultados de difração de raios X mostram que as amostras de ZnS foram cristalizadas completamente sem a presença de fases secundárias e os difratogramas correspondem à estrutura blenda cúbica de zinco com grupo espacial F-43m. Os espectros de XANES (X-ray Absorption Near Edge Structure) teóricos e experimentais na borda K do Zn indicam que a incorporação de átomos de Mn na matriz ZnS causam a formação de vacâncias de Zn e S, a qual é confirmada por ajustes de espectros EXAFS (Extended X-ray Absorption Fine Structure). Estas vacâncias estão relacionadas com um desvio para o vermelho observado no pico do espectro de fotoluminescência devido a adição de Mn na estrutura do ZnS. Para o ZnS puro, o pico é centrado em ~ 504 nm, relativo as vacâncias de S na amostra nanoestruturada. À medida que se aumenta a porcentagem de Mn na matriz ZnS, uma emissão no amarelo-laranja centrada em ~ 590 nm pode ser observada, associada com a transição 4T1-6A1 no interior de níveis 3d de Mn2+. A adição de íons Cu2+ ao ZnS resulta em um alargamento no pico do espectro de fotoluminescência decorrente de emissão no azul-verde, que está relacionada a recombinação de elétrons de níveis de defeitos mais profundos dos estados t2 do Cu próximos da banda de valência.
Nanocrystals has been extensively investigated in recent years due to its wide range of applications in various devices light emitting materials such as sensors, solar cells, lasers, photocatalysts, photodetectors, IR detectors, light emitting diodes and others. Nanocrystalline Semiconductors have electronic properties between those intermediate molecular macrocristalinos and solid structure, providing a wide range of applications. Among these materials, zinc sulfide (ZnS) pure or doped has received considerable attention because of its optical structural properties, versatility and potential for several technological applications. The ZnS is a typical II-VI semiconductor with a direct band gap of 3.6 eV at room temperature and about 40 meV in energy gap, and a good luminescent material for constrution of displays, lasers and sensors. As wide band gap material, ZnS can easily host different transition metals as luminescent centers. Among these ions of transition metal doped structures, Cu2+ and Mn2+ ions are attractive for light emission characteristics and for having effective properties for applications such as phosphors. The addition of these ions in ZnS structure provide defects that result in emission in the green for the Cu2+ ions and emission in orange for the Mn2+ ions. In this study, samples of pure ZnS and doped with Cu2+ and Mn2+ ions were prepared by solvotermal method, which demonstrate to be an effective process for preparing nanoparticles. Once prepared, the structures of the nanostructured samples were characterized and correlated with photoluminescent properties. The results of X-ray diffraction showed that the ZnS samples were completely crystallized without the presence of secondary phases and XRD patterns correspond to the structure of zinc blende to cubic space group F-43m. spectra XANES (X-ray Absorption Near Edge Structure) theoretical and experimental in the Zn K edge indicates that the inclusion of Mn atoms in the ZnS matrix cause the formation of Zn and S vacancies, which is confirmed by spectral adjustments EXAFS (Extended X-ray Absorption Fine Structure). These vacancies are associated with a red shift observed in the photoluminescence spectrum peak due to the addition of Mn in ZnS structure. For pure ZnS, the peak is centered at ~ 504 nm concerning the vacancies in the S nanostructured sample. As it increases the percentage of Mn in the ZnS matrix, in yellow-orange emission centered at ~ 590 nm can be observed, associated with the transition 4 T1- 6A1 inside 3d levels of Mn2+. Adding Cu2+ to the ZnS results in a broadening of the peak of the photoluminescence spectrum due to emission in blue-green, which is related to recombination deeper defect levels of electrons of t2 Cu states near the valence band.
Raevskaya, Alexandra, Oksana Rosovik, Andriy Kozytskiy, Oleksandr Stroyuk, Volodymyr Dzhagan, and Dietrich R. T. Zahn. "Non-stoichiometric Cu–In–S@ZnS nanoparticles produced in aqueous solutions as light harvesters for liquid-junction photoelectrochemical solar cells." Universitätsbibliothek Chemnitz, 2017. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-220126.
Повний текст джерелаDieser Beitrag ist aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich
Junior, João Batista Souza. "Síntese de nanoestruturas core/shell de Co/Au magnetoplasmônica e pontos quânticos de CdSe/ZnS." Universidade de São Paulo, 2017. http://www.teses.usp.br/teses/disponiveis/75/75134/tde-28072017-170738/.
Повний текст джерелаNanomaterials properties are size- and shape-controlled, such as the superparamagnetism phenomenon of magnetic nanoparticles or the quantum confinement of charge carriers of quantum dots. Therefore, synthesis of monodisperse spherical nanoparticles became extremely important over the past few deacades, since nanoparticles can be used for plenty of applications in technology and biomedicine. Magnetic nanoparticles and quantum dots are promising materials for diagnosis and therapy of cancer. Spherical nanoparticles of metallic cobalt were synthesized with mean diameter of 5,3 nm and standard deviation of 0,4 nm, lognormal distribution. A modified Langevin equation using the interacting superparamagnetic model was used to fit magnetization curves obtaining the mean magnetic diameter and standard deviation, 4,7 nm and 1,0 nm, respectively. The difference between these two diameters was assigned to the magnetic dead layer (∼3.0 Å), which does not contribute to the sample magnetization, being the saturation magnetization of cobalt nanoparticles around 125 emu g-1. Co/Au core/shell nanostructures were synthesized and the surface plasmon ressonance property was observed, an additional property also desired for biomedical applications, being the Co/Au core/shell system called magnetoplasmonic. CdSe quantum dots were synthesized with high size- and shape-controlled. Using different synthetic routes from the classic TOP-TOPO synthesis, and selenium dioxide as a precursor, the results show that and reducing agent is necessary and 1-octadecene solvent leads to better optical properties. CdSe samples showed a zinc blend (cubic phase) crystal structure, different from TOP-TOPO syntheses that leads to wurtzite structure (hexagonal phase). The growth kinetics of CdSe particles were also evaluated through aliquots from reaction showing exponential growth of particles diameter, as predicted on the theory of nucleation and growth. Fluorescence microscopy studies showed that quantum dots exhibited fluorescence intermittence behavior already reported in the literature as one fo the reasons for the quantum yield decrease. CdSe/ZnS core/shell nanostructures were obtained with high control of the coating layer thickness and the increase of the photoluminescence properties were shown.
Stroh, Albrecht. "Bildgebung von magnetisch markierten Stammzellen in experimentellen Krankheitsmodellen des ZNS mittels zellulärer Magnetresonanztomographie." Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät I, 2006. http://dx.doi.org/10.18452/15534.
Повний текст джерелаThis thesis is dealing with the imaging of magnetically labeled stem cells in the CNS using magnetic resonance imaging (MRI). Stem cells were efficiently magnetically labeled with very small superparamagnetic iron-oxide particles (VSOP), without any lipofection agents. No significant impact on vitality, proliferation and ability to differentiate could be observed after the magnetic labeling of all cell populations investigated. Magnetically labeled embryonic stem cells were injected into the striatum of rats to evaluate their detection limit by MRI. At field strengths of 17.6 T, less than 100 cells could be discriminated from the brain parenchyma as T2*-weighted hypointensities. Histology proved the cellular origin of MRI-signal changes. In a rat model of Parkinsons’s Disease, magnetically labeled embryonic stem cells could be detected by MRI after intrastriatal injection for a time period of more than 6 months. No significant migration of transplanted cells could be observed, however significant inter-individual differences concerning the spatial distribution of cells could be found. Histologically, transplanted iron-oxide-labeled cells could still be detected in the vicinity of the injection tract six months after transplantation. In a mouse model of cerebral ischemia, the enrichment of systemically injected magnetically labeled mononuclear cells was detected non-invasively by MRI. 24 to 48 hours after injection of magnetically labeled cells, T2*-weighted hypointense signal changes could be observed in the border zone of the ischemia. Over all, this study showed that cellular MRI is capable of the sensitive non-invasive detection of small numbers of magnetically labeled cells over a long period of time.
Dengo, Nicola. "Ligand-free water-based approaches for the synthesis of metal sulfides nanostructures." Doctoral thesis, Università degli studi di Padova, 2019. http://hdl.handle.net/11577/3424863.
Повний текст джерелаIn questa tesi sono stati sintetizzati solfuri metallici utilizzando metodi in soluzione acquosa che non prevedono l’uso di leganti. In particolare, ZnS, CuS, PbS, MnS e Ag2S sono stati ottenuti in forma cristallina ad una temperatura prossima a 0 °C e senza l’uso di leganti mediante un semplice metodo batch. Sono stati studiati la dimensione, la struttura cristallina, la composizione e i fenomeni di ossidazione delle particelle ottenute. È inoltre stato eseguito uno studio SAXS (Small Angle X-Ray Scattering) in-situ risolto nel tempo relativo alla sintesi di ZnS per valutarne la crescita nella miscela di reazione durante la sintesi batch. Sono inoltre stati studiati il comportamento in sospensione acquosa di particelle di ZnS e la loro interazione con sonde molecolari all’interfaccia liquido/solido. La sintesi di nanoparticelle di ZnS pure e drogate è stata eseguita mediante un metodo microfluidico ed uno CHFS (Continuous Flow Hydrothermal Synthesis). Nel caso di ZnS puro, le condizioni di sintesi sono state variate per ottenere informazioni sul meccanismo di formazione del materiale e valutare le potenzialità dei metodi utilizzati per controllare le proprietà dimensionali e strutturali delle nanoparticelle. Nel caso di ZnS drogato, l’incorporazione dei droganti nel materiale è stata quantificata e discussa. Le proprietà funzionali di alcuni campioni selezionati sono state studiate. Nel caso di ZnS puro è stata quantificata l’attività fotocatalitica per la HER (Hydrogen Evolution Reaction), mentre per il materiale drogato sono state misurate le proprietà di fotoluminescenza. È inoltre stata determinata la citotossicità di alcuni campioni ottenuti per via microfluidica in vista di potenziali applicazioni nella diagnostica per immagini. È stato eseguito uno studio approfondito sull’effetto di trattamenti termici e fenomeni di ossidazione sulle proprietà dimensionali, morfologiche, strutturali e composizionali delle nanostrutture e sui loro effetti sulla di attività fotocatalitica di nanoparticelle di ZnS di diversa dimensione. La strategia di caratterizzazione si è basata sull’uso complementare di tecniche diverse, quali l’XRD (X-Ray Diffraction) e la microscopia TEM (Transmission Electron Microscopy) per lo studio di proprietà dimensionali e strutturali, mentre XPS (X-ray Photoelectron Spectroscopy) e FTIR (Fourier Transform Infrared Spectroscopy) sono state usate per la determinazione della composizione superficiale. La caratterizzazione dei campioni è stata completata dalla spettroscopia Raman. I risultati ottenuti hanno mostrato la potenzialità dei metodi di sintesi proposti nell’ottenere il controllo di importanti proprietà dei materiali senza sfruttare l’uso di leganti superficiali, e hanno consentito lo studio della chimica della superficie esposta delle nanoparticelle sintetizzate.
Brayek, Amine. "Etude des propriétés photo-électrochimiques des structures cœur-coquille ZnO/ZnS électrodéposées sur verre-ITO." Sorbonne Paris Cité, 2016. http://www.theses.fr/2016USPCC075.
Повний текст джерелаHeterojunction structures are attracting lots of attention for enhancing the electron injection across the interface. ZnO@ZnS one-dimensional heterojunction films are synthesized on conducting glass substrates in a controlled way, using a simple two-step electrochemical deposition and a chemical sulfurization of ZnO nanowire array as reactive template. The photoelectrochemical (PEC) properties of the resulting hétérostructures were measured, using a homemade electrochemical tell illuminated with a standard Xenon lamp. The as-prepared ZnO@ZnS core—shell nanowire arrays are found to exhibit significantly enhanced photocurrent density for water splitting as compared to ZnO nanowire arrays. This is mainly due to the lower density of oxygen vacancies and other defects states. The special electron structure in the heterojunction helped to reduce the energy barrier height at the interface and enhanced the separation of photo-generated carriers. Thus, the photoelectrochemical performance was highly improved, and a photocurrent density of 0. 6 mAcm-2 at 0. 6 V (vs. Ag/AgC1) was obtained. Hence, our proposed structure is a promising candidate as a photoanode for solar energy-to-hydrogen conversion devices
Zobel, Mirijam [Verfasser], and Reinhard [Akademischer Betreuer] Neder. "Nanoparticle crystallization and solvent interface restructuring especially for ZnO nanoparticles in organic solvents / Mirijam Zobel. Gutachter: Reinhard Neder." Erlangen : Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), 2016. http://d-nb.info/1081544090/34.
Повний текст джерелаSandner, Julian Christoph. "Die toxikologische Relevanz der Zn2+-Freisetzung bei der Degradation von ZnO-Nanopartikeln." Doctoral thesis, Universitätsbibliothek Leipzig, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-211704.
Повний текст джерелаPujalte, Igor. "Étude in vitro de la toxicité de nanoparticules métalliques (TiO2, ZnO, CdS) sur la cible rénale." Thesis, Bordeaux 2, 2011. http://www.theses.fr/2011BOR21849/document.
Повний текст джерелаMany uncertainties remain about the potential toxic effect of nanoparticles (NPs), and their becoming in human organism. The aim of this study was to understand the cytotoxic mechanisms induced by metallic NPs, on a secondary target organ, the kidney. NPs were able to cross biological barriers, be carried in blood to kidney cells, on glomerular or tubular cells. This study was performed in vitro, with NPs of titanium (TiO2: 12 nm), zinc (ZnO: 75 nm) and cadmium (CdS: 8 nm), on mesangial IP-15 cells and epithelial HK-2 cells. Results showed effects depending on cell type, chemical nature of NPs and their solubility. TiO2 NPs have no cytotoxic effect (IC50>100µg/cm²), probably due to their insolubility. Exposure to CdS and ZnO NPs lead to cell death (IC50< 7 µg/ cm²). Release of metallic cations Cd2+ and Zn2+ are the main causes of toxicity. ROS production and disruption of oxidative cellular balance (GSH/ GSSG) were correlated to the cytotoxic effects of ZnO and CdS NPs. A molecular approach was used to identify signaling pathways involved in oxidative stress response (nuclear translocation of NF-kappaB and Nrf2).Internalization and accumulation of TiO2 and CdS NPs were responsible of oxidative stress induction and cytotoxic effect on long term exposure
Norman, Thaddeus Jude. "Optical and structural properties of gold nanoparticle aggregates and Mn 2+, CU 2+, and Ag 1+ doped ZnSe nanoparticles /." Diss., Digital Dissertations Database. Restricted to UC campuses, 2004. http://uclibs.org/PID/11984.
Повний текст джерелаZhao, Zhihua. "Systèmes hybrides : de la nanoparticule aux gels." Thesis, Toulouse 3, 2017. http://www.theses.fr/2017TOU30118/document.
Повний текст джерелаThis work is focused on the better understanding of the formation of zinc oxide anisotropic nanoparticle through an organometallic synthesis. To start on this project, the development of a statistical tool to analyze nanoparticle sizes and shapes was mandatory. A simple 2D plot with a multivariate statistical analysis is proposed in order to extract, in particular, the correlation between length and width in a collection or a mixture of anisotropic particles. Compared to the usual statistics on the length associated to a second and independent statistical analysis of the width, this simple plot easily points out the various types of nanoparticles and their (an)isotropy. For each class of nano-objects, the relationship between width and length (i.e. the strong or weak correlations between these two parameters) may suggest information concerning the nucleation-growth processes. It allows one to follow the effect on the shape and size distribution of physical or chemical processes such as simple ripening. Various electronic microscopy pictures from the literature or from our own syntheses are used as examples to demonstrate the efficiency and simplicity of such an analysis. Furthermore, following the organometallic approach, well defined crystalline zinc oxide nanorods are obtained through the hydrolysis reaction of dicyclohexyl zinc precursor without solvent in presence of primary fatty amine only. Their mechanism of formation is studied through a multivariate analysis of TEM results and an oriented attachment process is demonstrated. Taking advantage of this mechanism, the size of the ZnO nanorods can be easily adjusted tuned by controlling adjusting the hydrolysis rate, the aging time before hydrolysis, the nature of ligand, and/or the amount of water. During such experiments, a gelification of the chemical media are for the first time observed. This is the origin of the last part of our work, which put forward an original approach for outstanding processable and reshapable hybrid materials. Indeed, we unequivocally demonstrate through various complementary experiments (rheology, NMR, TEM, theoretical calculation, WAXS...) the formation of oligomeric structures in a mixture of fatty amine with organometallic compounds. This oligomerization reaction between the metallic centers induces the formation of a gel which can be processed into fibers, stamped patterns or molded pieces. Metal oxide hybrid materials are obtained merely by hydrolysis of the organometallic gel, which are furthermore liquid crystal. This unprecedented route towards easily processable hydrid and metal oxide materials is demonstrated for zinc oxide and extended to other metal oxides such as tin oxide and iron oxide, proving the universality of the method and paving the way, for example, to new sensitive gas sensors layers
Chassaing, Pierre-Marie. "Quelques illustrations du rôle de la surface dans des nanoparticules de ZnO." Phd thesis, Université Paul Sabatier - Toulouse III, 2009. http://tel.archives-ouvertes.fr/tel-00406581.
Повний текст джерелаNous montrons que les modes de vibration permettent d'illustrer des effets de surface, lesquels sont de deux types. Premièrement vient la réduction de la taille. L'élasticité linéaire ne décrit plus correctement les modes propres acoustiques pour des tailles inférieures à 2.5 nm. Les expériences que nous avons menées sont en accord avec ce point. Deuxièmement, nous montrons que les ligands qui habillent les nanoparticules sont préférentiellement localisés sur la surface latérale de ces dernières; et qu'ils étirent légèrement la maille cristalline de ZnO.
Concernant les propriétés excitoniques, l'exciton est piégé à la surface des nanoparticules. En outre, de part la dynamique de recombinaison très rapide, le processus de recombinaison de l'exciton est dominé par des mécanismes non-radiatifs.
Perraud, Igor. "Combustion auto-propagée et mécanosynthèse de ZnS : étude des conversions ZnS <->ZnO et application à la désulfuration des gaz." Thesis, Montpellier 2, 2012. http://www.theses.fr/2012MON20097/document.
Повний текст джерелаToday, we have to take care of every technology's environmental effects. The removal of H2S and other sulfur compounds in hot gas enters this ecological aspect in several industrial processes. Zinc oxide is used here as a regenerable sorbent for gas desulfurization. The goal of this work is, the preparation of macroporous ZnO monolithic filters and nanopowders with high sulfur capacity and easily regenerable, and their optimization with the control of their properties. ZnS/NaCl composite materials are first obtained by Self-propagating High temperature Synthesis from mixtures of zinc, sulfur and sodium chloride powders. NaCl is then removed by lixiviation with water. ZnS nanopowders are prepared by mechanical alloying from mixtures of zinc and sulfur. The two materials have different crystalline structure, würtzite type for ZnS filters and sphalerite type for powders, because of the way of synthesis. Then, they are converted into ZnO by thermal treatment under air at 700 °C. Next, the macro- and microstructure transformations of both filter and powders during sulfidation-oxidation cycles are thus considered. Results of all characterizations like X-ray diffraction, scanning electron microscopy and Hg porosimetry show that materials properties are very stable against conversions. Afterwards, ZnO filters and nanopowders are used as adsorbent in desulfurization trials. The sulfur capacity of filters is not so high, 6,4 mg S/g ads and shows that porosity has to be improved. Regarding nanopowders, the sulfur capacity is very high, 272 mg S/g ads, proving that surface area is very important in this application
Rubio-Garcia, Javier. "Strategies to yield water dispersible ZnO NPs synthesized by an organometallic approach." Toulouse 3, 2010. http://thesesups.ups-tlse.fr/891/.
Повний текст джерелаThere is an ever increasing interest in the synthesis and application of semiconducting materials due to their size-dependent physical and chemical properties (nanometric range). Multiple applications have radically emerged over the last few years including in the areas of biomedicine, solar cells or electronics. Among the semiconducting materials, nanosized ZnO is a good candidate for these applications as it is a relatively inexpensive and environmentally friendly material. Physical and chemical methods allow for the production of ZnO nanostructures. For some applications ZnO nanoparticles (NPs) are required as colloidal solutions and chemical methods are advantageous. In our research group, a chemical method based on the decomposition of organometallic precursors in the presence of a stabilizing agent has been developed. Good control with respect to the average size and the size distribution is achieved. However, this strategy presents as a main drawback the production of ZnO NPs that are only dispersible in non polar solvents. Application for cosmetics or in the field of biomedicine is impeded as a result. The motivation for this Thesis has been to bring about synthetic modification of the organometallic strategy in order to achieve ZnO NPs dispersible in water: either modification of the as-synthesized particles or changes to the synthetic procedure are mandatory
Balti, Imen. "Nanohybrides inorganique-organiques à base de ZnO, Zn0,95Ni0,05O,coeur-coquille ZnO@γ-Fe2O3 et de polymères bioactifs : Elaboration,propriétés optiques et magnétiques, cytotoxicité". Paris 13, 2012. http://scbd-sto.univ-paris13.fr/intranet/edgalilee_th_2012_balti.pdf.
Повний текст джерелаZnO, Zn0. 95Ni0. 05O and core@shell ZnO@γ-Fe2O3 nanoparticles have been prepared using forced hydrolysis of acetate metallic salts in a polyol medium and coated with poly(sodium-4- styrenesulfonate) and poly(sodium-4-styrenesulfonate–co–sodium methacrylate) via surfaceinitiated atom transfer radical polymerization. The bare nanoparticles display sphericalmorphology with a diameter size laying in the range 20 - 30 nm. The polymer chains weregrown from the surface to yield hybrid nanoparticles with an organic shell of 1 to 3 nm width. The surface modification with polymer did not alter the magnetic and optical properties of bare particles allowing their potential use for biomedical applications. The viability of human endothelial cells was not affected by coated nanoparticles after 48 h of exposition and normal proliferation occurred up to 8 days without alteration of the cell structure. Keywords: nanoparticles, magnetic and optical properties, bioactive Polymer, nonohybrids,cytotoxicity
Ngo, Van Giang. "Nanoparticules hybrides oxydes métalliques/polymères : synthèse et caractérisation." Phd thesis, Toulon, 2011. http://tel.archives-ouvertes.fr/tel-00768240.
Повний текст джерелаPiolet, Romain. "Synthèse hydrothermale de nanoparticules de ZnO au-delà du point critique : compréhension des étapes de germination et de croissance." Thesis, Dijon, 2014. http://www.theses.fr/2014DIJOS004/document.
Повний текст джерелаThe supercritical hydrothermal synthesis of nanopowders (especially metal oxide) has been widely studied. To the best of our knowledge, no nanoparticle formation mechanism has been published yet. In this prospect, this study is dedicated to the understanding of metal oxide nanoparticle nucleation and growth mechanisms. For this purpose, zinc oxide is used as a model material. First, the influence of synthesis operating conditions such as pressure, temperature, pH, precursor concentrations and solution flow rates on particle morphological properties (size, particle size distribution or morphologies) has been investigated. Hence, two approaches have simultaneously been carried out. The first approach involves powder characterizations by mean of X-ray diffraction or transmission electron microscopy techniques. The second one consists in the development of a numerical model considering the thermal exchanges, the fluid hydrodynamic behavior and chemical reaction inside the patented reactor by computational fluid dynamics. Results show good agreement between those two approaches. Several ZnO particle formation mechanisms based on powder experimental characterizations are presented in this work depending on operating conditions. In order to enhance the numerical model, a methodology has been set up to evaluate ZnO nanoparticle nucleation and growth rates in supercritical conditions (SCW) by the determination of particle solubility as function of temperature and the pressure
Jafarov, M. A., and E. F. Nasirov. "Zn1-xCdxS Nanoparticles, Nanofilms, Nanoscale Junction for SolarCells." Thesis, Sumy State University, 2012. http://essuir.sumdu.edu.ua/handle/123456789/34894.
Повний текст джерелаSuryajaya. "Study of electrostatically self-assembled thin films of CdS and ZnS nanoparticle semiconductors." Thesis, Sheffield Hallam University, 2007. http://shura.shu.ac.uk/20410/.
Повний текст джерелаRosset, Aurelie. "Synthèse et caractérisation de nanoparticules catalytiques pour une application en photocatalyse solaire." Thesis, Perpignan, 2017. http://www.theses.fr/2017PERP0014/document.
Повний текст джерелаThis thesis is part of the development and optimization of a doped and undoped panel of catalysts for the treatment of waste water based on an Advanced Oxidation Process (AOP), solar heterogeneous photocatalysis. This tertiary process for bio-recalcitrant organic molecules clean up is limited by the catalysts absorption in the UV range which represent only 5 % of the solar spectrum received on the earth surface. The aim is to compare photocatalytic efficiency under UV, visible and solar irradiation in order to improve efficiency in the UV range, to develop a catalyst which operates effectively under visible irradiation and to define key parameters governing the photocatalytic activities. In this context, a study is performed on doped or undoped ZnO based catalysts. All of ZnO based catalysts are synthesized by the same process, the sol-gel process under supercritical drying conditions. Structural, morphological, chemical, optical and optoelectronical characterizations is carried out to define their physico-chemical parameters in order to control the synthesis conditions of these catalysts. Doped ZnO also showed an absorption edge shift toward the visible range. Photocatalytic experiments are carried out with a photocatalysis optical bench in the UV, visible and solar range. Particular attention is paid on a model pollutant, pyrimethanil. In parallel, these experiments are coupled to a kinetic model. Nanoparticles of Zn1-xMxO (M : Ca, Al, Li, V, In, Co, P…) showed encouraging photocatalytic activities in the visible range. A correlation is showed between the physico-chemical properties of the catalysts and the radicals production efficiency. Furthermore, an extensive study is done on Zn0,90Ca0,10O. This study reveals the presence of structural defects playing a main role on the photocatalytic activities
Lee, Kwang Jik. "Study of stability of ZnO nanoparticles and growth mechanisms of colloidal ZnO nanorods." Texas A&M University, 2005. http://hdl.handle.net/1969.1/4303.
Повний текст джерелаMoussaoui, Myriam. "Elaboration et caractérisations de nouveaux matériaux diélectriques structurés par des nanoparticules de sulfure de zinc : applications prospectives." Thesis, Saint-Etienne, 2011. http://www.theses.fr/2011STET4001.
Повний текст джерелаOur efforts have been devoted to the development of simple approach to synthesize ZnS nanoparticules (NPs) by melting process in a glassy matrix with the aim to create a controlled optical index variation. In this thesis, we present the formation of ZnS NPs in the glassy matrix and study of their optical properties. The nanocomposite incorporating ZnS in the host medium was prepared using the melting process from a mixture of the raw materials. We have prepared various glass samples with ZnS NPs size ranging from 1.8 à 7 nm. These samples were treated (heat treatment ± UV insulation with 244 nm laser) and characterized by UV-Vis absorption, FTIR, photoluminescence spectroscopy, Raman measurements and XPS. The refractive index measurements of these nanostructured composite glasses have been carried out and show an important increase with ZnS concentrations and treatments. We also present the elaboration of small and monodisperse ZnS nanopowder with size ranging from 3 to 100 nm by a simple, low-cost and mass production chemical method. The NPs were characterised by X-ray powder diffraction (XRD), UV-vis absorption and photoluminescence spectroscopy. The photocatalytic activity of ZnS nanopowders was investigated by using different colorant water dispersed. ZnS NPs appear to be a good candidate for potential environmental applications such as water purification. We also present application of fluorescent ZnS nanoparticles as cellular biomarkers. Fluorescent microscopy images of osteoblastic MC3T3-E1 cells revealed that the ZnS nanoparticles were biocompatible and were penetrated cells and nucleus regardless of their size. Hence, the ZnS NPs can be good candidates for drug delivery and bio-imaging applications
Spisni, Eleonora. "Toxicity assessment of industrial- and sunscreen-derived ZnO nanoparticles." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2016. http://amslaurea.unibo.it/11272/.
Повний текст джерелаZhang, Miao. "Defects in ZnO nanoparticles obtained by gas-phase syntheses." Thesis, Paris 6, 2017. http://www.theses.fr/2017PA066259.
Повний текст джерелаBy far, the assignment of defects-related spectroscopic features of zinc oxide is still a matter of great controversy. This is probably due to the variety of possible defects in ZnO as well as to their still uncertain formation energies and positions within the band gap. Uncontrolled measurement conditions and impurities related to some synthesis methods can additionally mislead interpretations. The aim of this work is to identify the intrinsic native defects in pure ZnO or formed upon different kind of post-synthesis treatments. To fulfill this goal our strategy was to: i) prepare model zinc oxide nanoparticles using two different vapor-phase synthesis techniques (Combustion and CVS) ii) identify, assign and discuss the occurrence of the defects in line with the synthesis and post treatments conditions by combining in situ PL and EPR measurements together with other complementary spectroscopies (Raman, UV vis, FTIR) and iii) reveal the surface reactivity of defective ZnO samples by studying the interaction with water or 2-methyl-3-butyn-2-ol (MBOH). We observed that in all as-synthesized ZnO samples VO2+ and Zni+ are the predominant native defects with relative amounts depending on the partial pressure of oxygen used during the synthesis. Neutral oxygen vacancies (VO0) are additionally detected in samples prepared in conditions particularly rich in zinc. The formation of Vo+ is demonstrated in ZnO smoke upon post treatment (annealing in high vacuum or zinc vapor) while the associated electron release is shown to participate to the reduction of Zni+ into Zn0. On the contrary, annealing in oxygen leads to reverse processes while if used in an excess, to creation of Oi-related defects. Dissociation of water on vacuum annealed surface leads to the filling up of VO+, and reduction of Zn2+ into Zn+. Such redox processes controlled by the pretreatment conditions affect the surface reactivity through the change of the acid base balance, as revealed by MBOH conversion catalytic tests
Van, Zandt Nicholas L. "Aqueous Fabrication of Pristine and Oxide Coated ZnSe Nanoparticles." Wright State University / OhioLINK, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=wright1623356039586297.
Повний текст джерелаHagelin, Alexander. "ZnO nanoparticles : synthesis of Ga-doped ZnO, oxygen gas sensing and quantum chemical investigation." Thesis, Linköpings universitet, Institutionen för fysik, kemi och biologi, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-64730.
Повний текст джерелаTaïnoff, Dimitri. "Influence des défauts sur les propriétés optiques et électroniques des nanoparticules de ZnO." Phd thesis, Université Claude Bernard - Lyon I, 2009. http://tel.archives-ouvertes.fr/tel-00507281.
Повний текст джерелаFernando, Joseph F. S. "Crystal seeding and photochemistry of gold-zinc oxide hybrid nanoparticles." Thesis, Queensland University of Technology, 2016. https://eprints.qut.edu.au/101206/1/Joseph_Fernando_Thesis.pdf.
Повний текст джерелаCruz, González Sara. "Availability of metal ions and ZnO nanoparticles in aqueous media." Doctoral thesis, Universitat de Lleida, 2015. http://hdl.handle.net/10803/314762.
Повний текст джерелаLa presencia de determinados metales, ya sea en forma del metal libre, formando complejos con ligandos o en forma de nanopartículas metálicas tiene efectos negativos en el medio ambiente. Por este motivo, el estudio de la disponibilidad de metales es importante para determinar su impacto medioambiental. En este trabajo se ha estudiado un sistema y una técnica para la medida de la disponibilidad. El sistema tiene la particularidad de contener, en dispersión, nanopartículas de óxidos metálicos. Una primera parte del estudio se enfoca a la caracterización físico-química de dispersiones sintéticas de nanopartículas. Esta parte estudia el efecto que tienen las condiciones del medio (pH, salinidad, contenido de materia orgánica, etc) en el comportamiento de las nanopartículas. Se han determinado procesos como son la agregación, solubilidad y sedimentación, en función de las condiciones del medio. Todos estos procesos juegan un papel muy importante en el destino de las nanopartículas en el medio ambiente y en su toxicidad. La segunda parte de esta tesis se centra en la aplicación de la técnica analítica DGT (Diffusive Gradiente in Thin films) para la medida de flujos de metal disponibles en soluciones acuosas. En el presente trabajo, se ha determinado la solubilidad de nanopartículas en dispersiones acuosas. Por otra parte se ha estudiado la técnica DGT desde un punto de vista físico-químico. Las contribuciones de los flujos de complejos se evalúan con un parámetro que tiene en cuenta las constantes de disociación de los complejos así como su difusión. Se han estudiado las acumulaciones de metales que en solución tienen como especies dominantes complejos cargados eléctricamente. Si esta carga es negativa, la acumulación disminuye al bajar la fuerza iónica y viceversa en el caso contrario. Este fenómeno se explica por la repulsión electrostática entre la carga negativa del disco de resina y el complejo cuando éste es parcialmente lábil. En conclusión, la resina parece jugar un papel más activo de lo que se pensaba en la acumulación de metales en DGT.
The presence of certain metals, either in the form of free metal, forming complexes with ligands or as metal nanoparticles has negative effects on the environment. For this reason, the study of the availability of metals is important in determining its environmental impact. In this work a system and a technique for measuring availability have been studied. The system contains, in dispersion, metal oxide nanoparticles. A first part of the study focuses on the physical and chemical characterization of synthetic dispersions of nanoparticles. This part examines the effect of environmental conditions (pH, salinity, organic matter content, etc.) in the behavior of nanoparticles. Processes such as aggregation, solubilisation and sedimentation, are determined depending on environmental conditions. All these processes play an important role in the fate of nanoparticles in the environment and their toxicity. The second part of this thesis focuses on the application of the analytical technique DGT (Diffusive Gradient in Thin films) for measuring the flow of available metals in aqueous solutions. In the present study, the solubility of nanoparticles in aqueous dispersions has been determined. Moreover the DGT technique has been studied from a physical-chemical point of view. The contribution of the flux of complexes has been evaluated with a parameter, the lability degree, which takes into account the dissociation constants of the complexes and their diffusion. The accumulations of metals which in solution are present as dominant metal complexes electrically charged have been studied. If the charge is negative, the accumulation decreases with the decrease of the ionic strength and vice versa in the opposite case. This phenomenon is explained by the electrostatic repulsion between the negatively charged resin disk and the complex when it is partially labile. In conclusion, the resin seems to play a more active role than previously thought in the accumulation of metals in DGT.
Zhang, Lingling. "Antimicrobial behaviour of suspensions of ZnO nanoparticles towards Escherichia Coli." Thesis, University of Leeds, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.487794.
Повний текст джерелаSouici, Abdelhafid. "Etude des propriétés optiques et structurales de nanoparticules de ZnS et PbS induites par radiolyse." Paris 11, 2009. http://www.theses.fr/2009PA112066.
Повний текст джерелаThe present study examines the ZnS and PbS semiconductor nanoparticles synthesized by radiolysis of solution containing the thiol (RSH) and the ions of zinc (Zn²⁺) or of lead (Pb²⁺). The optical and structural properties of these nanoparticles have been analysed according to different parameters such as: dose, dose rate, concentrations of the precursors and pH solution. The ZnS nanoparticles with size ranged between 0,9 and 2,2 nm have been generated after irradiation. The control of the nanoparticles size allows not only the observation of the quantum size effect but also the command of their optical properties (350 – 450 nm). However, the PbS nanoparticles formed under irradiation of solution pH ≈ 4 characterized by excitonics bands in the near infrared have a size between 9 and 45 nm. The absorption and fluorescence bands observed in the ultraviolet and the visible ranges are due to the formation of nanoparticles of (PbS)n in the presence of the complex (Pb²⁺ - RSH). The radiolytic formation yield of (ZnS)n and of (PbS)n nanoparticles shows the effect of the alcohol function(-OH) of the thiol on the mechanism of formation. The nanoparticles of (ZnS)n are formed with radiolytic yield of G ≈ 3 x 10⁻⁷ mol J⁻¹ close to the one solvated electron
Raevskaya, A. E., Ya V. Panasiuk, O. L. Stroyuk, S. Ya Kuchmiy, V. M. Dzhagan, A. G. Milekhin, N. A. Yeryukov, et al. "Spectral and luminescent properties of ZnO–SiO2 core–shell nanoparticles with size-selected ZnO cores." Universitätsbibliothek Chemnitz, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-161737.
Повний текст джерелаDieser Beitrag ist aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich
Byl, Céline. "Synthèse et caractérisation de nanocomposites à base de ZnO pour des applications thermoélectriques." Thesis, Paris 11, 2015. http://www.theses.fr/2015PA112045/document.
Повний текст джерелаThis study is focusing on the synthesis of nanocomposites of Al doped ZnO/SiO2 with high density in order to increase the thermoelectric properties of ZnO. This work describes the optimization of the synthesis by investigating the effect of different experimental parameters (temperature, type of surfactant, degree of hydrolysis, nature of the solvent, pH) to obtain large amount of nanoparticles with size below 10 nm and good crystallinity. We have identified that using benzoic acid as surfactant could avoid the formation of particle aggregates. The modification of nanoparticles surfaces with SiO2 was investigated by using two methods the Stöber process and ALD. The possibility of ZnO and nanocomposite powder densification by spark plasma sintering was also tackled as well as the role played by the main parameters of the method (applied pressure and the best moment of its application, heating rate). The influence of the amorphous shell on the limiting grain growth during the sintering was demonstrated. Furthermore, a carbon accumulation which modifies the thermoelectric properties in the densified pellet was demonstrated. The source of it was assigned in part to the densification process. The most significant result of this study was the finding of the presence of ZnO clusters strongly doped wich could have fundamental implications as it may reopen the discussion on the transport mechanism in ZnO
Acuautla, Meneses Monica Isela. "Development of ozone and ammonia gas sensors on flexible substrate." Thesis, Aix-Marseille, 2014. http://www.theses.fr/2014AIXM4337/document.
Повний текст джерелаNowadays the emerging of new applications in the micro and nanotechnology field required to reduce fabrication costand to improve electronic devices with properties such as flexibility, portability, lightweight, and low cost. Traditional methods involve expensive and long production steps, and chemical vapor deposition. The purpose of this work is to present the conception and characterization of flexible ammonia and ozone sensors fabricated by photolithography and laser ablation processes. The flexible platform is composed of Kapton substrate with interdigitated Ti/Pt electrodes for gas detection and a micro-heater device. The circuit patterns were realized by photolithography and laser ablation. Photolithography is a well-known and reliable patterning process used on rigid substrate. The application of laser ablation process not only reduces fabrication time, but also represents an excellent viable alternative instead of chemical processes. ZnO thin films deposited by drop coating have been used as sensitive materials due to their excellent properties in the gas detection. The gas sensing condition and the performances of the devices are investigated for ozone and ammonia at different gas concentrations and different thin film thicknesses. In order to test a deposit methodology used in large scale industrial production, an ultrasonic spray deposition was done. The sensor provides a wide range of detection from 5 ppb to 500 ppb for ozone and from 5 ppm to 100 ppm for ammonia. Their best sensibilities were obtained at 200°C for ozone and 300 °C for ammoniac with good repeatability, stability and fast response/recovery time
Hancock, Jared M. "Formation and Analysis of Zinc Oxide Nanoparticles and Zinc Oxide Hexagonal Prisms and Optical Analysis of Cadmium Selenide Nanoparticles." BYU ScholarsArchive, 2013. https://scholarsarchive.byu.edu/etd/3867.
Повний текст джерелаJiang, Yunhong. "Antimicrobial behaviour of Polyvinyl Chloride(PVC) films coated with ZnO nanoparticles." Thesis, University of Leeds, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.545697.
Повний текст джерелаIbrahem, Mohammed A. "Multiwavelength photoconductivity of ZnO nanoparticles based on surface defects and plasmonics." Thesis, University of Hull, 2017. http://hydra.hull.ac.uk/resources/hull:16599.
Повний текст джерелаShahmoradi, B., and A. Mateki. "Surface modification of ZnO and Ti02 nanoparticles under mild hydrothermal conditions." Thesis, Sumy State University, 2011. http://essuir.sumdu.edu.ua/handle/123456789/20866.
Повний текст джерелаLondono, Zuluaga Nathalia. "Impacts of engineered nanoparticles (TiO2, ZnO, Ag) on aquatic microbial communities." OpenSIUC, 2016. https://opensiuc.lib.siu.edu/theses/1858.
Повний текст джерелаZhu, Yao. "ZnO nanoparticles as a luminescent down-shifting layer for solar cells." Thesis, Lyon, INSA, 2015. http://www.theses.fr/2015ISAL0090/document.
Повний текст джерелаIn this thesis, we aim at designing mechanically stable ZnO nanoparticle based materials as a luminescent down-shifting layer that can be processed on a scalable amount and deposited on standard solar cells at a reduced cost. The main challenge was thus to get ZnO nanoparticles with as high photoluminescence quantum yield (PL QY) as possible. Different methods have been used and compared to synthesize ZnO nanoparticles. We have first studied particles synthesized by a physical route (the Low Energy Cluster Beam Deposition relying on the adiabatic expansion of a plasma). The resulting particles did not exhibit a PL QY high enough to be interesting for down-shifting. We next investigated commercial particles which behaved as the LECBD ones. We consequently discarded them. Eventually, we concentrated on nanoparticles produced by wet chemistry. Two routes were explored: the conventional co-precipitation method of Zn acetate or sulfate in presence of an alkaline hydroxide and the hydrolysis of ZnEt2. For both cases the synthesis parameters have been tuned to optimize the optical properties for down-shifting process. When appropriately choosing the alkaline ion (Li+ instead of K+) nature and amount, the PL QY has been increased to 13 % in the co-precipitation method. Our results reproduce the state-of-the-art knowledge concerning this technique. The hydrolysis route proved to be even more interesting. The sole hydrolysis reaction did not lead to very bright particles. We have thus proposed an original strategy: the addition of a weak acid, the polyacrylic acid (PAAH) during the synthesis. If PAAH has been used previously as a passivating capping agent of ZnO, its use during the synthesis has never been tempted. Our work shows that by tuning the amount and molecular weight (chain length) of PAAH introduced during the synthesis, a very efficient hybrid nanocomposite consisting of ZnO nanopaerticles in a PAAH matrix can be obtained with PL QY as high as 20 %. When mixing PAAH to its sodium salt PAANa, the nanocomposite exhibits record values of PL QY of 50 %, increasing to 70 % over a month. The physico-chemical reasons for this enhancement are discussed in the manuscript. Our explanations point to a combined effect of the size, morphology and composition. In the subsequent part, ZnO NPs dispersible in water have been successfully achieved while maintaining their PL QY high, between 20 % - 34 %, using a PAAH/PAANa mixture at the optimal volume ratio, concentration, lengths and volume. We highlight the need to get a compromise between a good dispersibility and a high PL QY. This part of the thesis paves the way for the further industrial applications. Finally, the down-shifting effect of luminescent ZnO nanoparticles on solar cells has been simulated to obtain a potential enhancement of solar cell efficiency by the ZnO NPs down-shifting layer
Tan, Soon-Seng, and 陳順成. "The synthesis and characteristics of ZnS and ZnO nanoparticles." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/26626104846406917985.
Повний текст джерела國立成功大學
電機工程學系碩博士班
92
Zinc sulfide (ZnS) and Zinc oxide (ZnO), as II-VI semiconductors with a wide band gap energy of 3.68 eV and 3.35 eV respectively, have received much attention due to their excellent luminescence properties and commercially used as phosphors applicated in electroluminescence devices. They are candidate materials for phosphors that emit visible light. The major and important applications of phosphors are used as light sources, display devices, radiation detectors and so on. In this report, we use low temperature solid-state synthesis and chemical precipitation method to prepare ZnS, ZnO and ZnS doped Mn2+ nanoparticles. The nanoparticles were characterized by X-ray diffraction (XRD), photoluminescence (PL) spectroscopy, differential thermal analysis (DTA), high-resolution analytical electron microscopy (HR-AEM), energy dispersive spectrometer (EDS), CIE chromaticity diagram, impedance analyzer (HP-4294A) and Raman spectrum. By means of various experiment parameters to find out the preferred synthesis conditions. From the experiment results, the PLE spectrum exhibits a blue shift due to quantum confinement effect. The dimension of particles and the ratio of Zinc and Sulfur in the ZnS matrix affect the PL intensity. By adding 1 mol% Mn2+ ion, it shows the maximum emission intensity. A green emission peak at 501 nm was observed in PL spectrum of ZnO nanoparticles. In our experiment, we have successfully obtained the phosphor fabricated at low tempereture emits near-white color.
Chen, Hui-Wei, and 陳慧薇. "Synthesis of ZnS and Mn-doped ZnS nanoparticles and its photoluminescence." Thesis, 2003. http://ndltd.ncl.edu.tw/handle/87899132794837961550.
Повний текст джерелаMnqiwu, Khumblani. "ZnS and CuxSy nanoparticles from dithiocarbamate ligands." Thesis, 2017. http://hdl.handle.net/10352/428.
Повний текст джерелаDithiocarbamate ligands and their complexes has been a subject of interest in various fields but they found much interest in medical applications as potential anti-microbial agents. The dithiocarbamate ligands were used to prepare complexes of copper and zinc. All the prepared ligands and complexes were characterized using techniques such as IR and 13CNMR spectroscopy and thermogravimetric analysis (complexes). The data obtained from the spectroscopies was consistent with the coordination of the ligand to the metal ion through the sulfur atoms of the dithiocarbamate or thioureide moiety. The thermal analysis of the prepared complexes gave a final residue of metal sulfide, thus indicating the potential of the prepared complexes as single molecular precursor for the synthesis of metal sulfide nanoparticles. The prepared complexes were then used to synthesize metal sulfide nanoparticles. The nanoparticles were successfully prepared by thermal decomposition of a single-source precursor (dithiocarbamate complexes) in a solution of hexadecylamine (HDA) or tri-n-octylphosphine oxide (TOPO). The investigated parameters were the capping molecule (HDA and TOPO), and capping molecule concentration (3 g and 6 g) to see their effect on the shape and size of the synthesized nanomaterials. The synthesized metal sulfide nanoparticles were characterized using techniques such as UV-vis spectroscopy, photoluminescence spectroscopy, X-ray diffraction analysis and transmission electron microscopy. The absorption study showed some interesting features in the prepared nanomaterials. The first was the red-shifted spectra of the ZnS nanoparticles which was attributed to the impurities and that assumption was further confirmed by the XRD analysis that showed a sulfur impurity and other amorphous peaks. The second was the localized surface plasmon resonances on the copper sulfide nanoparticles that suggested the formation of electron deficient copper sulfide stoichiometry that was further confirmed by XRD analysis that gave hexagonal phase copper sulfide covellite. The TEM images of the prepared nanoparticles showed that the concentration and the capping molecule has an effect on the size and shape of the synthesized nanoparticles. The increase in capping concentration gave a decrease in particle size in most of the prepared nanoparticles, while they were few exceptions. The capping molecule effect showed that most of the nanoparticles prepared from TOPO were spherical in shape and were well dispersed compared to the mixed morphological nanoparticles prepared from HDA. There were also exceptions of the well dispersed HDA-capped nanoparticles.
Ignawati, Sifera, and 葉美慧. "Optical and Structure Characterization and Synthesis of CdS/ZnS and ZnS/CdS core shell nanoparticles." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/80966331346304532178.
Повний текст джерела國立成功大學
化學工程學系碩博士班
97
CdS and ZnS core nanoparticles were synthesized by microwave method and then coated with shell material by traditional method, using simple and safe reagents such as cadmium acetate, zinc acetate, and thiourea to synthesis the core shell nanopartices. After coating CdS core by ZnS shell the photoluminescence intensity greatly increase from 18 a.u to a maximum photoluminescence intensity of 225 a.u. For ZnS/CdS core shell nanoparticles, after CdS coated on ZnS core, the photoluminescence intensity increases significantly too, the bare ZnS cores have a photoluminescence intensity of 353 a.u and the ZnS/CdS core shell nanoparticles can reach a maximum photoluminescence intensity of 1460 a.u. Shell formation was confirmed by observation of a red shifting in the photoluminescence spectra. As the precursor feeding rate decreases, it leads the formation of bigger core shell nanoparticles, and so does the increases of precursor concentration. The advantage of the process is that it can be carried out in the open air using simple equipment and is simpler, cheaper, and safer as compared with another method.
Gao, Yu-Jia, and 高于迦. "Preparation and Luminescence Properties of Manganese Doped ZnS Nanoparticles." Thesis, 2001. http://ndltd.ncl.edu.tw/handle/35804545404981806649.
Повний текст джерела大同大學
材料工程研究所
89
We choose ZnS as host material in this study because of its excellent photoelectric property, and adding Manganese element of different concentration as activator. Co-precipitation method is used to prepare manganese doped zinc sulfide nanocrystal, and PL analysis is performed to realize the change of PL property made by different manganese concentration and heat treatment. Also, the effect of nanosize to sample is discussed. The recombination energy of electron-hole pairs in ZnS crystal transfer to Mn2+ ion, causing it to emit characteristic spectra. This yellow spectra of bulk ZnS:Mn observed in photoluminescence has peak at 585nm (2.12 eV), and this is associated with the 4T1→6A1 transition of Mn2+ ion in 3d orbit. The sample that 1% Mn doped has a λem of 592nm, and theλem shifts to 600nm when the concentration of Mn doped increases to 5%. Comparing to common bulk ZnS:Mn, the λem of ZnS:Mn nanocrystal we made shifts to longer wavelength. When the particle size decreases to nanosize, the effect of crystal field to each ion will decrease. Also, as a result of quantum confinement, the electron transition orbit changes so that the emitting wavelength shifts. Nanosize not only makes emission wavelength shift to longer wavelength area but also causing the excitation wavelength λex changes with particle size; if the size of particle become smaller, the λex shifts to higher energy area. We can know from FTIR and PL spectra that heat treatment temperature of 200℃ doesn’t almost do no changes to our sample, but 300℃ and 400℃ make sample having higher luminous strength. This result is due to the organic substance like C=O and COO- in sample powder before heat treatment, and the organic substance affects absorption and transfer process of energy so that 300℃ and 400℃ heat treatment make sample having higher luminous strength by decreasing organic substance. But sample with 5% Mn heat treated to 400℃ has lower luminous strength than 300℃; this is due to the result of concentration quenching.
Huang, Chia-Ching. "Studies of magneto-optical properties of CdTe/CdSe/ZnS multilayer nanoparticles." 2008. http://www.cetd.com.tw/ec/thesisdetail.aspx?etdun=U0001-0502200817375000.
Повний текст джерелаHuang, Chia-Ching, and 黃家慶. "Studies of magneto-optical properties of CdTe/CdSe/ZnS multilayer nanoparticles." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/13504253023348323757.
Повний текст джерела臺灣大學
物理研究所
96
Although the absolute phase of a quantum state is not measurable, the relative phase of a coherent charged particle wave could be manipulated. In the famous Aharonov-Bohm effect for an electron traveling in a ring, interference pattern was observed with changing magnetic flux. Recently, optical Aharonov-Bohm has received much attention. The effect of the relative phase of the electron and hole in a magnetic field on the excitonic properties in semiconductors was studied theoretically and oscillation of the excionic energy and quenching (or oscillation) of the integrated photoluminescence intensity with magnetic field were predicted. Experimentally, evidence of the optical Aharonov-Bohm effect was observed with negatively charged exciton in InGaAs/GaAs quantum ring and polarized exciton in type-II GaAs-GaSb system. In this thesis we’ll present our studies on the optical Aharonov-Bohm in CdTe/CdSe/ZnS system. The nanoparticles were grown by chemical method and have size of about 6 nm and the band alignment between the core (CdTe) and the shell (CdSe) is a type–II band alignment. The addition of ZnS layer is to passivate the surface of CdSe and to enhance the light emitting efficiency. Magneto-photoluminescence experiment was performed at T=1.4 K with a 14 T superconducting magnet in conjunction with a green diode laser and a monochromator. Oscillation on the peak energy of the photoluminescence spectra as well as oscillation in the integrated intensity as a function of magnetic field were observed and are attributed to the optical Aharonov-Bohm-like effect.
Chuang, Ya-Ting, and 莊雅婷. "Photochemical Assisted Method in Decoration of Au Nanoparticles on ZnS and ZnSe Crystal for Surface-enhanced Raman Scattering Measurement." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/28t33j.
Повний текст джерела國立中興大學
化學系所
106
Surface-enhanced Raman scattering (SERS) is a powerful means for chemical analysis. This SERS effect can be observed when target molecules adsorbed or nearby metal nanoparitcles with a proper size and shape. To prepare active substrates for SERS measurements, ZnS and ZnSe crystals were selected as solid support in this work as they are commonly used optical windows, which exhibit photocatalytic ability with unique chemical properties. Methods based on electroless displacement and the assistance of photoreduction were developed to decorate SERS active gold nanoparticles (AuNPs) on the selected ZnS and ZnSe crystals. Several parameters, such as the concentration of reaction solution, the temperature of reaction, photo irradiation time, and the additive, were examined their contributions to the production of suitable AuNPs for SERS measurements. pHydroxythiophenol (pHTP) was used to probe the SERS performances for the prepared SERS substrates. After correlation of the observed Raman signals, the morphology of produced AuNPs by SEM with reaction parameters, mechanisms in production of AuNPs on ZnS and ZnSe were found significantly different. For produced AuNPs on ZnS crystal, AuxSy particles were formed rather than AuNPs, which degraded their SERS performances. On the other hand, when ZnSe crystals were used, Se atoms in the ZnSe crystals are capable to reduce the gold ions through formation of higher oxidation state of Se and hence, AuxSe particles formed on the surface of ZnSe is limited. On the other hand, SERS substrates based on ZnSe showed much better performances than that of ZnS. By tuning the reaction conditions, SERS substrates based on ZnS and ZnSe could be successfully prepared. Based on the optimized condition in preparation of SERS substrates, SERS intensity of pHTP on ZnS substrate was found an order weaker than that of ZnSe. In conclusion, a new method to prepare AuNPs on ZnS and ZnSe was successfully developed in this work and both the mechanism in formation and the impact of each parameter to the formation of AuNPs were well explored.
Chang, Chih-Yuan, and 張志遠. "Advanced Nanodevice Structures with CdSe/ZnS and/or Au Nanoparticles for Photo-Sensing Applications." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/00272243905175103222.
Повний текст джерела國立交通大學
電子工程系所
94
In this work, we used CdSe/ZnS (core/shell) and/or Au NPs to construct the multi-layered photo-sensing nanodevice structures on a silicon substrate through ionic interaction. ZnS with larger energy bandgap served as a passivation layer on CdSe NPs to enhance the stability and quantum yield. From the results of UV-visible absorbance and photoluminescence spectra, CdSe/ZnS NPs exhibit better optical properties than CdSe NPs in the previous work. For the four-layered nanostructure composed of CdSe/ZnS and Au NPs, there was constantly about 28 nA (30μm / 5μm) and 70 nA (30μm / 15μm) increment to the current measured in the dark for each voltage bias after illumination with 375 nm laser. In addition to 375 nm, 400 nm and 435 nm lasers were also used as light sources for photo-excitation. We found that more photocurrent was generated under shorter wavelength illumination, which was also verified in the absorption / emission spectra. Besides, more photocurrent was generated in the nanostructure with a longer length or a larger number of layers, which can be successfully explained by using the model of “nano-Schottky-diodes and resistor array”. We can obtain the same phenomenon as using HSPICE to simulate the two dimensional model. Finally, we found that the“photocurrent volume density (PVD)”of the 4-layered Au / AET-CdSe/ZnS nanostructure is at least 1183 times better than that of CdSe thin film structure. The power conversion efficiency can achieve 40% based on ourideal inference. In addition to nanodevice composed Au and CdSe/ZnS NPs, we constructed multi-layered structure on the silicon oxide substrate by using only CdSe/ZnS NPs. MSA-CdSe/ZnS and AET-CdSe/ZnS NPs, which were chemically modified prior to ionic assembly process, have negative-charged and positive-charged functional groups on the surface of the NPs respectively. We found that the PVD of the 12-layered structure is at least 34 times better than that of conventional CdSe thin film structure. Finally, we conclude that the Au / AET-CdSe/ZnS nanodevice acts like a photodiode while the MSA-CdSe/ZnS / AET-CdSe/ZnS nanodevice acts like a typical traditional photoresistor. Besides, the Au / AET-CdSe/ZnS nanodevice has enormous potential to turn into solarcells applications.
Chia-ChingChu and 朱家慶. "The Excitation Spectroscopy of the NaD X-A Transitions and the Synthesis of ZnS Nanoparticles." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/80641357272505053670.
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