Dissertations / Theses: 'Metal Oxides Nanoparticles'

1

Magnone, Heidi J. "Synthesis and characterization of metal oxide nanoparticles." Morgantown, W. Va. : [West Virginia University Libraries], 2000. http://etd.wvu.edu/templates/showETD.cfm?recnum=1762.

Full text

Abstract:

Thesis (M.S.)--West Virginia University, 2000.
Title from document title page. Document formatted into pages; contains vi, 38 p. : ill. Vita. Includes abstract. Includes bibliographical references (p. 35-37).

APA, Harvard, Vancouver, ISO, and other styles

2

Xu, Chunbao. "Continuous and batch hydrothermal synthesis of metal oxide nanoparticles and metal oxide-activated carbon nanocomposites." Diss., Available online, Georgia Institute of Technology, 2006, 2006. http://etd.gatech.edu/theses/available/etd-07302006-231517/.

Full text

Abstract:

Thesis (Ph. D.)--Chemical and Biomolecular Engineering, Georgia Institute of Technology, 2007.
Teja, Amyn, Committee Chair ; Kohl, Paul, Committee Member ; Liu, Meilin, Committee Member ; Nair,Sankar, Committee Member ; Rousseau, Ronald, Committee Member.

APA, Harvard, Vancouver, ISO, and other styles

3

Buha, Jelena. "Nonaqueous syntheses of metal oxide and metal nitride nanoparticles." Phd thesis, Universität Potsdam, 2008. http://opus.kobv.de/ubp/volltexte/2008/1836/.

Full text

Abstract:

Nanostructured materials are materials consisting of nanoparticulate building blocks on the scale of nanometers (i.e. 10-9 m). Composition, crystallinity and morphology can enhance or even induce new properties of the materials, which are desirable for todays and future technological applications. In this work, we have shown new strategies to synthesise metal oxide and metal nitride nanomaterials. The first part of the work deals with the study of nonaqueous synthesis of metal oxide nanoparticles. We succeeded in the synthesis of In2O3 nanopartcles where we could clearly influence the morphology by varying the type of the precursors and the solvents; of ZnO mesocrystals by using acetonitrile as a solvent; of transition metal oxides (Nb2O5, Ta2O5 and HfO2) that are particularly hard to obtain on the nanoscale and other technologically important materials. Solvothermal synthesis however is not restricted to formation of oxide materials only. In the second part we show examples of nonaqueous, solvothermal reactions of metal nitrides, but the main focus lies on the investigation of the influence of different morphologies of metal oxide precursors on the formation of the metal nitride nanoparticles. In spite of various reports, the number and variety of nanocrystalline metal nitrides is marginally small by comparison to metal oxides; hence preformed metal oxides as precursors for the preparation of metal nitrides are a logical choice. By reacting oxide nanoparticles with cyanamide, urea or melamine, at temperatures of 800 to 900 °C under nitrogen flow metal nitrides could be obtained. We studied in detail the influence of the starting material and realized that size, crystallinity, type of nitrogen source and temperature play the most important role. We have managed to propose and verify a dissolution-recrystallisation model as the formation mechanism. Furthermore we could show that the initial morphology of the oxides could be retained when ammonia flow was used instead.
Nanostrukturierte Materialien sind Materialien, die aus nanopartikulären Baueinheiten in der Größenordnung von Nanonmetern (d.h. 10-9 m) bestehen. Zusammensetzung, Kristallinität und Morphologie können die natürlichen Eigenschaften dieser Materialien verbessern oder zusätzliche Eigenschaften erzeugen, die für heutige und zukünftige Anwendungen und Verfahren wünschenswert sind. In dieser Arbeit präsentieren wir neue Strategien zur Synthese von Nanopartikeln der Metaloxide und Metalnitride. Im einführenden Teil wird die nichtwässrige Synthese von Metaloxidnanopartikeln beschrieben. Uns gelang die Darstellung von In2O3 Nanopartikeln, deren Größe und Form wir durch die Wahl des Prekursors und des Lösemittels deutlich beeinflussen konnten; von ZnO Mesokristallen durch den Einsatz von Acetonitril als Lösemittel; von Übergangsmetalloxiden (Nb2O5, Ta2O5 and HfO2), die besonders schwer im Nanomaßstab zu erhalten sind und von anderen, technisch relevanten Materialien. Die Möglichkeiten der solvothermalen Synthese sind nicht mit der Darstellung von Oxidmaterialen erschöpft. Im zweiten Teil zeigen wir einige Beispiele nichtwässriger, solvothermaler Synthese von Metalnitriden auf; das Hauptaugenmerk liegt aber auf einer Betrachtung der Einflüsse der Morphologie von Metaloxidnanopartikelprekursoren auf die Bildung der Metalnitridnanopartikel. Die Anzahl und Vielfalt bekannter nanokristalliner Metalnitride ist verschwindend klein im Vergleich zu den Metaloxiden, die in der Fachliteratur etabliert sind und demzufolge einen reichen Baukasten an Prekursoren zur Darstellung von Metalnitriden liefern. Durch die Reaktion von Metaloxidnanopartikeln mit Cyanamid, Urea oder Melamine bei Temperaturen von 800 bis 900 °C unter Stickstofffluss konnten Metalnitride erhalten werden. Eine detaillierte Studie der Reaktionsbedingungen und des Reaktionsablaufs zeigte auf, dass Größe und Kristallinität der Metaloxide, die Art der Stickstoffquelle und die Temperatur die entscheidenden Faktoren sind und legte eine Auflösungs-Rekristallisation als Modelmechanismus dieser Art Reaktion nahe. Darüber hinaus konnte gezeigt worden, dass die anfängliche Morphologie des Oxids unter einem Ammoniafluss beibehalten werden konnte.

APA, Harvard, Vancouver, ISO, and other styles

4

Worden, Matthew. "Aqueous syntheses of transition metal oxide nanoparticles for bioapplications." Kent State University / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=kent1440585507.

Full text

APA, Harvard, Vancouver, ISO, and other styles

5

Li, Zhen. "The Transport and Fate of Metal and Metal Oxides Nanoparticles under Different Environmental Conditions." University of Cincinnati / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1427963167.

Full text

APA, Harvard, Vancouver, ISO, and other styles

6

Taujale, Saru. "INTERACTIONS BETWEEN METAL OXIDES AND/OR NATURAL ORGANIC MATTER AND THEIR INFLUENCE ON THE OXIDATIVE REACTIVITY OF MANGANESE DIOXIDE." Diss., Temple University Libraries, 2015. http://cdm16002.contentdm.oclc.org/cdm/ref/collection/p245801coll10/id/347169.

Full text

Abstract:

Civil Engineering
Ph.D.
Mn oxides have high redox potentials and are known to be very reactive, rendering many contaminants susceptible to degradation via oxidation. Although Mn oxides typically occur as mixtures with other metal oxides (e.g., Fe, Al, and Si oxides) and natural organic matter (NOM) in soils and aquatic environments, most studies to date have studied the reactivity of Mn oxides as a single oxide system. This study, for the first time, examined the effect of representative metal oxides (Al2O3, SiO2, TiO2, and Fe oxides) and NOM or NOM-model compounds (Aldrich humic acid (AHA), Leonardite humic acid (LHA), pyromellitic acid (PA) and alginate) on the oxidative reactivity of MnO2, as quantified by the oxidation kinetics of triclosan (a widely used phenolic antibacterial agent) as a probe compound. The study also examined the effect of soluble metal ions released from the oxide surfaces on MnO2 reactivity. In binary oxide mixtures, Al2O3 decreased the reactivity of MnO2 as a result of both heteroaggregation and complexation of soluble Al ions with MnO2. At pH 5, the surface charge of MnO2 is negative while that of Al2O3 is positive resulting in intensive heteroaggregation between the two oxides. Up to 3.15 mM of soluble Al ions were detected in the supernatant of 10 g/L of Al2O3 at pH 5.0 whereas the soluble Al concentration was 0.76 mM in the mixed Al2O3 + MnO2 system at the same pH. The lower amount of soluble Al in the latter system is the result of Al ion adsorption by MnO2. The experiments with the addition of 0.001 to 0.1 mM Al3+ to MnO2 suspension indicated the triclosan oxidation rate constant decreased from 0.24 to 0.03 h-1 due to surface complexation. Fe oxides which are also negatively charged at pH 5 inhibited the reactivity of MnO2 through heteroaggregation. The concentration of soluble Fe(III) ions ( 4 mg-TOC/L or [alginate/PA] > 10 mg/L, a lower extent of heteroaggregation was also observed due to the negatively charged surfaces for all oxides. Similar effects on aggregation and MnO2 reactivity as discussed above were observed for ternary MnO2‒Al2O3‒NOM systems. HAs, particularly at high concentrations (2.0 to 12.5 mg-C/L), alleviated the effect of soluble Al ions on MnO2 reactivity as a result of the formation of soluble Al-HA complexes. Alginate and PA, however, did not form soluble complexes with Al ions so they did not affect the effect of Al ions on MnO2 reactivity. Despite the above observations, the amount of Al ions dissolved in MnO2+Al2O3+NOM mixtures was too low, as a result of NOMs adsorption on the surface to passivate oxide dissolution, to have a major impact on MnO2 reactivity. In conclusion, this study provided, for the first time, a systematical understanding of the redox activity of MnO2 in complex model systems. With this new knowledge, the gap between single oxide systems and complex environmental systems is much narrower so that it is possible to have a more accurate prediction of the fate of contaminants in the environment.
Temple University--Theses

APA, Harvard, Vancouver, ISO, and other styles

7

Haggstrom, Johanna A. "Synthesis, characterization, biocidal and virucidal properties of metal oxide nanoparticles." Diss., Kansas State University, 2007. http://hdl.handle.net/2097/1236.

Full text

Abstract:

Doctor of Philosophy
Department of Chemistry
Kenneth J. Klabunde
Non-polar halogens (Cl2, Br2 and I2) and polar interhalogen molecules (ICl, IBr and ICl3) have been adsorbed on the surface of several high surface area materials, including three different nanosized metal oxides (NanoActive® (NA) Al2O3 Plus, NA-TiO2 and NA-CeO2). The prepared halogen and interhalogen adducts have been characterized in detail by thermogravimetric analysis (TGA), UV-Vis, Raman and X-ray photoelectron spectroscopies (XPS) and the results are discussed herein. The different metal oxides lead to varying strength of adsorption of the halogen/interhalogen in the prepared adducts and adsorption is stronger in the nanosized metal oxides as compared to their macrocrystalline available counterparts. Nanosized metal oxide halogen adducts possess high surface reactivities due to their unique surface morphologies. These adducts have been used as reactive materials against vegetative cells, such as Escherichia coli and Bacillus megaterium, as well as spores, including Bacillus subtilis and Bacillus anthracis (Δ Sterne strain). High biocidal activities against both Gram-positive and Gram-negative bacteria, as well as spores have been obtained. Bactericidal test procedures include a water suspension method and a dry membrane method and the results illustrate that good results are obtained using both procedures. Transmission electron micrographs have been used to illustrate the treated and untreated cells and spores, giving insight into the mechanism. It is proposed that the abrasive character of the particles, along with the oxidative power of the halogens/interhalogens as well as the electrostatic attraction between some of the metal oxides and the biological material are main reasons for the high biocidal activities. Three different bacteriophages (MS2, φX174 and PRD1) have also been studied and initial results indicate that there is big potential for the use of metal oxide halogen and interhalogen adducts for the destruction of viruses. Other potential uses for them also include halogenating agents in organic and inorganic synthesis as well as a safe way to store intact halogens.

APA, Harvard, Vancouver, ISO, and other styles

8

Ba, Jianhua. "Nonaqueous synthesis of metal oxide nanoparticles and their assembly into mesoporous materials." Phd thesis, [S.l.] : [s.n.], 2006. http://deposit.ddb.de/cgi-bin/dokserv?idn=982245963.

Full text

APA, Harvard, Vancouver, ISO, and other styles

9

Karna, Sanjay K. "Enhancement of Light Emission from Metal Nanoparticles Embedded Graphene Oxide." Thesis, University of North Texas, 2016. https://digital.library.unt.edu/ark:/67531/metadc849637/.

Full text

Abstract:

A fully oxidized state of graphene behaves as a pure insulating while a pristine graphene behaves as a pure conducting. The in-between oxide state in graphene which is the controlled state of oxide behaves as a semiconducting. This is the key condition for tuning optical band gap for the better light emitting property. The controlling method of oxide in graphene structure is known as reduction which is the mixed state of sp2 and sp3 hybrid state in graphene structure. sp2 hybridized domains correspond to pure carbon-carbon bond i.e. pristine graphene while sp3 hybridized domains correspond to the oxide bond with carbon i.e. defect in graphene structure. This is the uniqueness of the graphene-base material. Graphene is a gapless material i.e. having no bandgap energy and this property prevents it from switching device applications and also from the optoelectronic devices applications. The main challenge for this material is to tune as a semiconducting which can open the optical characteristics and emit light of desired color. There may be several possibilities for the modification of graphene-base material that can tune a band gap. One way is to find semiconducting property by doping the defects into pristine graphene structure. Other way is oxides functional groups in graphene structure behaves as defects. The physical properties of graphene depend on the amount of oxides present in graphene structure. So if there are more oxides in graphene structure then this material behaves as a insulating. By any means if it can be reduced then oxides amount to achieve specific proportion of sp2 and sp3 that can emit light of desired color. Further, after achieving light emission from graphene base material, there is more possibility for the study of non-linear optical property. In this work, plasmonic effect in graphene oxide has been focused. Mainly there are two kinds of plasmon effects have been studied, one is long range (surface) and short range (localized) plasmon. For long range plasmon gold thin film was deposited on partially reduced graphene oxide and for short range plasmon silver nanoparticles have used. Results show that there are 10-fold enhancement in light emission from partial graphene oxide coated with gold thin film while 4-fold enhancement from reduced graphene oxide solution with silver nanoparticles. Chemical method and photocatalytic method have been employed for the reduction of graphene oxide for the study of surface plasmon and localized plasmon. For the characterization UV-Vis spectrometer for absorption, spectrofluorophotometer for fluorescent emission, Raman spectrometer for material characterization, photoluminescence and time resolved photoluminescence have been utilized. Silver and gold nanoparticles are spherical of average size of 80 nm and 40 nm have been used as plasmons.

APA, Harvard, Vancouver, ISO, and other styles

10

Escorihuela, Martí Laura. "Computational characterisation of metal oxide nanoparticles for hazard screening and risk assessment." Doctoral thesis, Universitat Rovira i Virgili, 2019. http://hdl.handle.net/10803/669615.

Full text

Abstract:

Donades les propietats intrínseques de les nanopartícules els d’òxids metàl·lics ( MeO) NPs són el pilar fonamental de aplicacions avançades tecnològicament en àrees com electrònica, farmàcia o medicina. En canvi, existeix un important buit pel que fa com influencien les seves propietats físico químiques i el risc que suposen per la salut humana. L’avaluació de la toxicitat dels nanomaterials es una dura tasca que involucra múltiples condicions experimentals. Els mètodes computacionals, in-silico, teòrics i estadístics, avaluen, determinen i prediuen processos o fins i tot propietats de les substàncies. Apart, de la urgència que existeix legislativa per avaluar el risc que comporten, existeix un buit en la literatura, donat que els diferents experiments que si expliquen tenen buits en la descripció de la metodologia emprada o detalls experimentals, llavors no es útil per la avaluació del risc. El mètode més popular computacional, és Desnity Functional theory (DFT) , basat en en la mecànica quàntica . En aquesta tesi es desenvolupa un estricte estudi dels millors mètodes que permeten optimitzar des de la energia de l’estat fonamental per superfícies, nanotubs i nanopartícules esfèriques. Per obtenir valors més precisos per la determinació del band gap, s’ha incrementat el nivell de teoria utilitzant el DFT+U, finalment per obtenir valors per sistemes de 3000 àtoms per la simulació de sistemes biològics , s’ha implementat el mètode DFTB de dinámica molecular, també utilitzat per la avaluació de la solubilitat. Els resultats computacionals obtinguts per ZnO han estat prometedors, llavors s’ha provat per al TiO2, demostrant que la metodologia ideada funciona. Finalment, les dades obtingudes s’han utilitzat per crear model de predicció de propietats band gap i solubilitat per NPs més grans i amb aquestes poder generar model nano-QSAR( Quantitat-eStructura-Acivitat-Relació), on es relacionen les propietats estudiades amb el nivell de toxicitat del MeO NP.
Las propiedades intrínsecas de las nanopartículas de óxidos metálicos (MEO) NPs son el pilar fundamental de aplicaciones avanzadas tecnológicamente en áreas como electrónica, farmacia o medicina. En cambio, existe un importante vacío en cuanto cómo influyen sus propiedades físico-químicas y el riesgo que suponen para la salud humana, la evaluación de la toxicidad de los nanomateriales es un dura tarea que involucra múltiples condiciones experimentales. Los métodos computacionales, in-silico, teóricos y estadísticos, evalúan, determinan y predicen procesos o incluso propiedades de las sustancias. Además de la urgencia que existe legislativa para evaluar el riesgo que conllevan, existe un vacío en la literatura, dado que en los diferentes experimentos que se explican en la literatura tienen vacíos en la explicación de la metodología empleada o detalles experimentales, entonces no son útiles para la evaluación del riesgo. El método más popular computacional, es Density Functional theory (DFT), basado en la mecánica cuántica. En esta tesis se desarrolla un estricto estudio de los mejores métodos que permiten optimizar desde la energía del estado fundamental para superficies, nanotubos y nanopartículas esféricas. Para obtener valores más precisos para la determinación del band gap, se ha incrementado el nivel de teoría utilizando el DFT + U, finalmente para obtener valores para sistemas de 3000 átomos para la simulación de sistemas biológicos, se ha implementado el método DFTB de dinámica molecular, también utilizado para la evaluación de la solubilidad. Los resultados computacionales obtenidos por ZnO han sido prometedores, entonces se ha probado para el TiO2, demostrando la validez de la metodología ideada. Finalmente, los datos obtenidos se han utilizado para crear modelos de predicción de propiedades (band gap y solubilidad) para NPs más grandes y con estas poder generar modelo nano-QSAR ( Cantidad-eStructura-Acividad-Relación), donde se relacionan estas propiedades estudiadas con el nivel de toxicidad del MeO NP.
Given the intrinsic properties, metal oxide nanoparticles (MeO) NPs are the cornerstone of a wide range of technologically advanced applications in areas such as electronics, pharmacy or medicine. However, there is still an important knowledge gap regarding how size influences their physicochemical properties and the risk to human health. Toxicity assessment of NMs is a daunting task involving multiple testing conditions. Computed based methods, in silico methods, based on theoretical and statistical domain, evaluate, determine and predict processes or even substance properties. Furthermore, the legislation urgency for risk assessment exits given that the data for the environmental risk assessment found in literature is uncertain and present knowledge gaps, though is not useful for the risk assessment for nanoparticles. The most popular in silico method based on quantum mechanics for chemistry is Density Functional Theory (DFT). In this thesis we performed a strict and deep study of best methods to evaluate the band gap and the solubility of MeO NP. The use of periodical-DFT methods has allowed us to optimise the ground state energy for surfaces, nanotubes and spherical nanoparticles. To get more reliability for band gap determination, the exchange-correlation functional has been improved to DFT+U. After that, to reach to large systems up to 3000 atoms in order to simulate more realistic biological systems, we used DFTB methodology for band gap prediction; we also coupled DFTB with Molecular Dynamics to compute NP solubility. The computational results obtained with the methodology developed in this thesis for the ZnO case have been promising and, in order to make more robust the method employed, it has been tested for TiO2 too, showing an excellent efficiency in the results. Finally, the data obtained from the prediction models of band gap and solubility models have been used to create nano-QSAR (Quantity-Structure-Activity-Relationship) models.

APA, Harvard, Vancouver, ISO, and other styles

11

Sabo, Daniel E. "Novel synthesis of metal oxide nanoparticles via the aminolytic method and the investigation of their magnetic properties." Diss., Georgia Institute of Technology, 2012. http://hdl.handle.net/1853/50122.

Full text

Abstract:

Metal oxide nanoparticles, both magnetic and nonmagnetic, have a multitude of applications in gas sensors, catalysts and catalyst supports, airborne trapping agents, biomedicines and drug delivery systems, fuel cells, laser diodes, and magnetic microwaves. Over the past decade, an inexpensive, simple, recyclable, and environmentally friendly large, scale synthesis method for the synthesis of these metal oxide nanoparticles has been sought. Many of the current techniques in use today, while good on the small, laboratory bench scale, suffer from drawbacks that make them unsuitable for the industrial scale. The aminolytic method, developed by Dr. Man Han while working for Dr. Zhang, fits industrial scale-up requirements. The aminolytic method involves a reaction between metal carboxylate(s) and oleylamine in a non-coordinating solvent. This system was shown to produce a range of spinel ferrites. Dr. Lisa Vaughan showed that this method can be recycled multiple times without degrading the quality of the produced nanoparticles. The purpose of this thesis is to test the versatility of the aminolytic method in the production of a wide range of metal oxides as well as various core/shell systems. Chapter 2 explores the effect of precursor carboxylates chain length on the aminolytic synthesis of cobalt ferrite, and manganese ferrite nanoparticles. In Chapter 3, a series of CuxMn1-xFe₂O₄, (x ranges from 0.0 to 0.2), nanoparticles were synthesized via the aminolytic method. This series allows for the investigation of the effects of orbital Jahn-Teller distortion as well as orbital angular momentum on the magnetic properties of this ferrite. The quantum couplings of magnetic ions in spinel ferrites govern their magnetic properties and responses. An understanding of the couplings between these metal ions allows for tailoring magnetic properties to obtain the desired response needed for various applications. Chapter 4 investigates the synthesis of MnO and Mn₃O₄ nanoparticles in pure single phase with high monodispersity. To the best of our knowledge, the range of sizes produced for MnO and Mn₃O₄ is the most extensive, and therefore a magnetic study of these systems shows some intriguing size dependent properties. The final part of this chapter investigates the applicability of the aminolytic method for building a MnO shell on a CoFe₂O₄ core. Chapter 5 explores the synthesis of another metal oxide, ZrO₂ in both the cubic and monoclinic phases with no impurities. The use of the aminolytic method here removes the need for dangerous/expensive precursors or equipment and eliminates the need for extensive high temperature heat treatments that destroy monodispersity which is required for most techniques. The creation of a core/shell system between CoFe₂O₄ and ZrO₂ using the aminolytic method was also tested. This core/shell system adds magnetic manipulation which is especially useful for the recovery of zirconia based photocatalyst. Chapter 6 studies the application of the aminolytic method in the synthesis of yttrium iron garnet (YIG) and yttrium iron perovskite (YIP) nanoparticles. Current synthesis techniques used to produce YIG and YIP nanoparticles often requires high temperatures, sensitive to contamination, which could be eliminated through the use of our method

APA, Harvard, Vancouver, ISO, and other styles

12

Beck, Michael Peter. "Thermal conductivity of metal oxide nanofluids." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/26488.

Full text

Abstract:

Thesis (Ph.D)--Chemical Engineering, Georgia Institute of Technology, 2009.
Committee Chair: Teja, Amyn S.; Committee Member: Abdel-Khalik, Said I.; Committee Member: Meredith, Carson; Committee Member: Nair, Sankar; Committee Member: Skandan, Ganesh. Part of the SMARTech Electronic Thesis and Dissertation Collection.

APA, Harvard, Vancouver, ISO, and other styles

13

Vargas, Reus Miguel A. "An investigation into the use of metal nanoparticles and their oxides as antimicrobial agents." Thesis, Queen Mary, University of London, 2011. http://qmro.qmul.ac.uk/xmlui/handle/123456789/693.

Full text

Abstract:

Nanotechnology is concerned with the study of processes and applications at the nanoscale (10-9 m), with objects that are generally smaller than 100 nm. Within the biomedical field, the use of metal nanoparticles and their oxides as antimicrobial agents is gaining attention. In this study, the potential antimicrobial activity of thirteen different nanoparticulate metals, oxides, carbides and nitrides was examined. These were generated by thermal plasma technology. Initially, ten different bacterial species/strains of clinical significance were subjected to in-depth antimicrobial screening, which included the determination of minimum inhibitory and minimum bacteriocidal concentrations. The nanoparticles that demonstrated the greatest potential as novel antibacterial agents were, in descending order of activity: Ag > CuO > Cu2O > Cu > ZnO with effective concentrations from 100 to 2500 μg/ml. Ag and CuO nanoparticles, alone and blended, along with the salts of both elements were further examined in time-kill assays. Nanoparticulate Ag (100 μg/ml) was able to reduce microbial populations to zero within 2h. While, nanoparticulate CuO required higher concentrations (> 1000 μg/ml) and longer times (up to 4h) than silver to reduce microbial populations to zero. Blends of Ag and CuO nanoparticles were shown to be superior than when used alone, with reduced concentrations and time required (approx. 50%). Nanoparticles alone were not shown to be superior to that of their corresponding salts. Antimicrobial activity in the presence of serum was not reduced. Nanoparticulate TiO2, which lacked antimicrobial activity in the absence of UV light, was shown to possess significant antimicrobial properties when irradiated with short wave radiation. Environmental Scanning Electron Microscopy (ESEM) and - 3 - Scanning Ion Conductance Microscopy (SICM) were used to examine toxic effects of nanoparticles on bacteria. These revealed CuO nanoparticles to cause a greater physical change to bacteria when compared to Ag. Following nanoparticle incorporation into epoxy resin and polyurethane, the antimicrobial activity of the resulting polymer-nanocomposites were examined. Both polymers were shown to exhibit antimicrobial properties. Ion release was shown to be more marked from materials containing CuO nanoparticles. Nanoparticle biocompatibility using skin, respiratory and gastrointestinal cell lines was also investigated. CuO was shown to be generally more toxic than Ag to eukaryotic cells.

APA, Harvard, Vancouver, ISO, and other styles

14

Einakchi, Raha. "Metal Nanoparticles Over Active Ionic-Conductive Supports for the Reverse Water Gas Shift Reaction." Thesis, Université d'Ottawa / University of Ottawa, 2016. http://hdl.handle.net/10393/34462.

Full text

Abstract:

Increase in carbon dioxide emissions due to economic activity induce global warming. The strong increase in energy demand, mainly based on oil and coal, induces a rapid increase in CO2 in the atmosphere. Within Canada, the amount of human-produced carbon dioxide is considerable because a large portion of energy is supplied by burning of fossil fuels. The Reverse Water Gas Shift (RWGS) reaction is a promising catalytic process for the utilization and subsequent activation of carbon dioxide to carbon monoxide, which can be further converted into fuels such as gasoline. The current thesis studies the development of nano-catalytic systems for the RWGS reaction. Mono- and bi-metallic nanoparticles based on Cu, Fe, Ru and Pt were prepared using a polyol synthesis method. The catalytic performance of three different types of metal oxides (ionically conductive, mixed ionic-electronic conductive and non-conductive) was investigated for the RWGS reaction. Conductive metal oxides including samarium-doped ceria (SDC), ceria (CeO2), yttria-stabilized zirconia (YSZ) and iron III oxide (Fe2O3) were further used as the catalyst supports and the nanoparticles of Cu, Fe, CuxFe1-x (x = 50 and 95 at.%), Ru, Pt, Ru50Pt50 and RuxFe1-x (x = 80 and 90 at.%) were subsequently deposited on them. A stoichiometric mixture of H2 and CO2, i.e. H2/CO2 = 1, was used under atmospheric pressure in the temperature range of 300 - 600°C in order to evaluate the catalyst performance in terms of activity, stability and selectivity. Nanoparticles deposited on ceria-based supports (CeO2 and SDC) showed superior catalytic performance compared to other metal oxides. Among all the catalyst tested, 5 wt.% Ru50Pt50/CeO2 showed the highest CO yield and satisfactory stability for RWGS reaction. The second best catalytic systems were based on Ru90Fe10/CeO2 and Ru80Fe20/CeO2, which are more attractive from the practical point of view.

APA, Harvard, Vancouver, ISO, and other styles

15

Worsley, Myles. "Development of novel nanoengineered materials : chemical synthesis, properties and applications." Thesis, Brunel University, 2015. http://bura.brunel.ac.uk/handle/2438/14019.

Full text

Abstract:

The materials synthesised in this study were designed to have novel morphology coupled with a tightly controlled surface composition that could be varied depending on a application. Preparations with simple single metal oxides (i.e. TiO2, SiO2, Al2O3 and ZrO2) were used as the starting point with the latter stages involving multi-metal oxide coatings and materials. The research was divided into three interconnected areas; i) biotemplating, ii) alternative synthetic morphologies to biotemplating and iii) the synergy between microparticles and insecticides. For the investigation into biotemplating pollen was chosen as the main example due to its ubiquity. Here, good replication of its structure with metal oxides can be achieved by two-dimensional solgel chemistry. Such materials can be further modified to have tunable surface chemistry through dopants and optical properties (i.e. fluorescence) through the use of dyes. Materials were extensively characterised using primarily spectroscopy (UV and IR) and microscopy (i.e. SEM coupled with EDX elemental analysis). These were considered for several applications and examples investigated here included as a taggant technology and photocatalytic removal of methyl orange in an aqueous environment (TiO2-pollen only). For the latter, results have been compared with those of a commercially available alternative (P25) where the preliminary results are very promising. The method of overcoating was also shown to be transferrable to other flora and fauna biotemplates. Synthetic alternatives for the biotemplated pollen were considered in the second investigative area where solution sol-gel processes such as the Stöber method were considered in addition to other suspension based precipitation methods (i.e. refluxes and microemulsions). Processes developed in the biotemplating research were applied here and analysed again using spectroscopy and microscopy as the main techniques. As part of this aspect, a novel fast-drying water-in-oil microemulsion delivery and preparative system was also developed using low boiling point solvents such as isopentane and ethanol and low toxicity sucrose ester surfactants. Hollow oxide shells could be prepared in these using a novel low-temperature route that were comparable in thickness (but significantly smaller in size) to hollow pollen replicas. In this second area attention was shifted to more focus on oxides of Si and Al (as opposed to TiO2 that used extensively in biotemplating) to broaden the scope of the research and investigate other potential applications, such as nanoabrasives (surface roughness and ability to cleave DNA). The third and final area of interest used the materials from the previous two aspects in coatings that were applied to investigating the knockdown (KD) and total mortality (TM) of selected arthropods. Here mosquitoes of the A. Gambiae and S. Aegypti genus were considered with particular focus on synergistic effects with existing commercial insecticides (using mainly CDC bottle tests). Microscopy was used as the primary characterisation technique here to determine particle transfer after each assay. In these tests %TM suggested SiO2 microspheres were particularly effective at in enhancing mortality of the commercial l-cyhalothrin insecticide. Additionally, novel methods of recording mosquito behaviour was investigated through optical and thermographic stills and videos.

APA, Harvard, Vancouver, ISO, and other styles

16

Andio, Mark Anthony. "Sensor Array Devices Utilizing Nano-structured Metal-oxides for Hazardous Gas Detection." The Ohio State University, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=osu1343155831.

Full text

APA, Harvard, Vancouver, ISO, and other styles

17

Popa, Adriana. "Study of the Effect of Nanostructuring on the Magnetic and Electrocatalytic Properties of Metals and Metal Oxides." Case Western Reserve University School of Graduate Studies / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=case1427735465.

Full text

APA, Harvard, Vancouver, ISO, and other styles

18

Weerathunga, Kaluarachchige Don H. "Metal nanoparticle and semiconductor heterogeneous catalysis for synthetic organic oxidation reactions." Thesis, Queensland University of Technology, 2022. https://eprints.qut.edu.au/228677/1/Kaluarachchige%20Don_Weerathunga_Thesis.pdf.

Full text

Abstract:

This thesis investigated new metal nanoparticle and semiconductor catalyst and photocatalyst systems for achieving fine chemical synthesis from both fossil-fuel sourced reactants and biomass carbohydrate-derived reactants. Photocatalysts for industrially important organic oxidation reactions were developed that efficiently worked with the aid of solar light irradiation, at low temperature and pressure, that avoided the use of hazardous chemicals. The effects on the organic reaction mechanisms of different noble metal nanoparticle and metal oxide nanostructures were explored for these chemical transformations. Success in developing the nanomaterial photocatalysts has contributed to the field of sustainable green chemical synthesis.

APA, Harvard, Vancouver, ISO, and other styles

19

Carew, Alexander Jon. "Fundamental studies into the catalytic properties of metal-oxide supported gold and copper nanoparticles." Thesis, University of Liverpool, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.367710.

Full text

APA, Harvard, Vancouver, ISO, and other styles

20

Binti, Wan Ramli Wan Khairunnisa. "Exsolved base metal catalyst systems with anchored nanoparticles for carbon monoxide (CO) and nitric oxides (NOx) oxidation." Thesis, University of Newcastle upon Tyne, 2017. http://hdl.handle.net/10443/3875.

Full text

Abstract:

Noble metals notably platinum (Pt), is a major element of heterogeneous catalysts, excel in catalysing an extensive number of important catalytic reactions in chemical and automotive industries. Since the increased use of these metals is severely limited because of their high cost and scarcity’s, there is therefore an urgent need for the search of alternative base metal catalysts that are cheaper and more widely available. This can only be practical if the main drawbacks of base metals such as the agglomeration of particles under high temperatures operational conditions and irreversible sulphur poisoning can be overcome, and their activity enhanced, such that they can directly replace Pt on a weight-to-weight basis. However, most previous studies have been restricted to low temperature reaction conditions and have not compared their activity directly to that of Pt, whether in terms of active sites or on a weight-to-weight basis. Moreover, most researchers have not investigated extensively the long-term stability of their base metal catalysts, since the longest was at most around 200 hours and at relatively low temperatures, for example at room temperature. It is proposed that long term stability can be achieved by producing uniformly distributed nano-sized socketed and strained base metal particles via the exsolution method. The main objective of this thesis is to produce exsolved base metals catalyst systems rivalling Pt on a weight-to-weight basis in two base reactions; CO and NO oxidation. NO oxidation was also chosen as our model reaction in this research since most Pt in the automotive industry are used in the lean NOx trap (LNT) or a combination of LNT and selective catalytic reduction (SCR), which demand the high conversion of NO to NO2 at low temperatures to work effectively. Initial screening experiments were performed to evaluate the potential CO oxidation activities and long-term stability at 520 °C of two different exsolved metal pellet systems namely lanthanum-doped ceria nickel titanates to exsolve nickel (Ni) metal (La0.8Ce0.1Ni0.4Ti0.6O3) and lanthanum-doped strontium iron nickel titanates to exsolve iron-nickel (FeNi) alloy (La0.5Sr0.4Fe0.1Ni0.1Ti0.6O3). Exsolved FeNi pellet system gives high and stable turnover frequencies (TOFs) of 103 s-1 at 520 °C for almost 170 hours, which confirms the potential of these stable exsolved metal systems for CO oxidation. Sixty exsolved metal powder systems with various metal formulations were produced to enable direct activity comparison to Pt on a weight-to-weight basis. Most exsolved metal systems displayed increasing CO2 production rates with increasing CO partial pressures (PCO) and reversible sulphur poisoning with exsolved CoNi powder system showing remarkable stability at 200 °C for 655 hours (one month). This exsolved CoNi system also showed enhanced activity for CO oxidation upon exposure to CO-rich environment, as a result of the restructuring of particles iv into metal oxide nanocubes anchored onto nanosockets within the support surface. The CO2 production rates of the activated exsolved CoNi powder system at 200 and 520 °C were 0.13 x 10-4 and 1.5 x 10-4 mol s-1 g-1 compared to its initial rate of around 0 (below the detected limit of 0.007 x10-4 mol s-1 g-1) and 0.8 x 10-4 mol s-1 g-1 prior to activation. These active spinel (CoNi)3O4 cubic structures were seen planted at an angle of ~55°, at the edge of an empty socket with mediocre features for CO oxidation, such as rich in Co2+ with exposed (100) planes that had only 44 cubes μm-2 compared to its initial 144 particles μm-2 particle population. Above 450 °C, the main active sites for CO oxidation were thought to be close to or at the metal-support interface of the exsolved CoNi systems. Comparable NO2 production rates to those of commercial Pt catalyst was achieved with only ± 5 % of difference at each measured point within the temperature range used (100-440 °C) over exsolved CoNi system by exploiting the effect of having two particle size ranges (10 and 30 nm). These results confirm the dual functionality of the activated exsolved CoNi system and its huge potential to be commercialised as an alternative catalyst to Pt in two oxidation reactions; CO and NO oxidation. In general, a simple procedure that induces high, long-lasting activity in a base metal catalyst, rivalling platinum for CO and NO oxidation on a weight-to-weight basis was demonstrated. The nature of this activation by tracking individual nanoparticles was successfully elucidated to link their microstructural evolution to their catalytic and kinetic behaviour. This research also illustrates new strategies for enhancing and tailoring the catalytic activity of base metal systems towards replacing platinum.

APA, Harvard, Vancouver, ISO, and other styles

21

Odziomek, Mateusz Janusz. "Colloidal Synthesis and Controlled 2D/3D Assemblies of Oxide Nanoparticles." Thesis, Lyon, 2017. http://www.theses.fr/2017LYSEN092/document.

Full text

Abstract:

La nanotechnologie est devenue un domaine clé de la technologie du XXIe siècle. L’important développement des approches pour la synthèse des nanoparticules (NPs) avec une composition, une taille et une forme désirées rend compte du potentiel de leur utilisation comme « blocs de construction » pour des structures de plus grande échelle. Cela permet d’envisager à la fois la fabrication de matériaux fonctionnels et de dispositifs directement à partir de colloïdes par approche ascendante et la conception de matériaux sur plusieurs échelles de grandeur. Le procédé utilise l'assemblage ou l'auto-assemblage de NPs et conduit à des matériaux avec des architectures différentes notamment 1D (bâtonnets), 2D (films) ou 3D (super-réseaux ou gels). Cependant, la plupart des assemblages 3D sont limités à l'échelle micrométrique et sont difficiles à contrôler. Pratiquement, la seule voie permettant la préparation de structures 3D macroscopiques à partir de NPs est la gélification et la préparation d'aérogels. Une voie alternative consiste à disperser les NPs dans une matrice, conduisant ainsi à un matériau composite massif, avec des NPs non agrégées distribuées de manière homogène.Le présent travail est consacré au développement de matériaux à partir de NPs d'oxydes métalliques (principalement Y3Al5O12: Ce et Li4Ti5O12) de différentes dimensions et pour diverses applications. La première partie de ce travail décrit la synthèse de NPs de YAG: Ce et de LTO par approche glycothermale. Dans le cas du YAG: Ce, les conditions de réaction ont été ajustées de façon appropriée pour obtenir des nanocristaux (NCs) non agrégés de quelques nanomètres. Des solutions colloïdales de différentes concentrations contenant de tels NCs ont été utilisées, pour la fabrication par la technique de « spin-coating », de films minces avec une épaisseur contrôlable. A l’inverse, la synthèse de LTO conduit à des NPs agrégées dans une structure hiérarchique très bénéfique pour les batteries au lithium. La grande surface spécifique et la porosité du matériau obtenu assurent en effet un échange efficace des ions lithium entre l'électrolyte et le matériau d'anode.Par ailleurs, les NCs de YAG: Ce ont été utilisés pour la préparation de matériaux monolithiques de grande taille avec une porosité et une transparence élevées. Pour cela, la solution colloïdale de NCs a été gélifiée par le changement brusque de la constante diélectrique du solvant de dispersion des NCs. Les gels ainsi obtenus ont été par la suite séchés de manière supercritique, donnant ainsi des aérogels à base de NPs de YAG:Ce, avec une porosité et une transparence élevées. La même approche s'est avérée appropriée pour d'autres systèmes à base de NPs de GdF3 ou de mélanges de NPS de YAG: Ce et de GdF3.Alternativement, les NPs de YAG: Ce ont été incorporées dans des aérogels de silice formant ainsi des aérogels macroscopiques robustes et hautement transparents présentant les propriétés des NPs incorporées. Ces aérogels composites ont été utilisés en tant que nouveaux types de capteurs pour les rayonnements ionisants de basse énergie dans les liquides ou les gaz. Leur porosité élevée permet un contact optimal entre l'émetteur radioactif et le scintillateur assurant ainsi une bonne récupération de l'énergie radioactive
Nanotechnology has become a key domain of technology in XXI century. The great development of the synthetic approaches toward nanoparticles (NPs) with desired composition, size and shape expose the potential of their use as building blocks for larger scale structures. It allows fabrication of functional materials and devices directly from colloids by bottom-up approach, thus involving possibility of material design over several length scales. The process is referred to NPs assembly or self-assembly and leads to materials with varying architectures as for instance 1D (rods), 2D (films) or 3D (superlattices or gels). However most of 3D assemblies are limited to the micrometric scale and are difficult to control. Practically the only route allowing preparation of macroscopic 3D structures from NPs is their gelation and preparation of aerogels. As an alternative, NPs can be embedded in some matrix creating bulk composite material, with homogenously distributed non-aggregated NPs.Therefore, this work is devoted to development of materials with different dimensionalities for various applications from metal oxides NPs (mainly Y3Al5O12:Ce and Li4Ti5O12). The first part describes the syntheses of YAG:Ce and LTO NPs by glycothermal approach. In the case of YAG:Ce, the reactions conditions were appropriately adjusted in order to obtain non-aggregated nanocrystals (NCs) of few nanometers. The colloidal solution containing such NCs with different concentration was used for fabrication of thin films with controllable thickness by spin-coating method. Contrary, the synthesis of LTO led to aggregated NPs with hierarchical structuration which was highly beneficial for Li-ion batteries. The large surface area and porosity ensured efficient exchange of Li ions between electrolyte and anode material. Furthermore, the YAG:Ce NCs were used for preparation of macroscopic monoliths with high porosity and transparency. For that reason, colloidal solution of NCs was gelled by the abrupt change of solvent dielectric constant. The gels were further supercritically dried yielding YAG:Ce NPs-based aerogels with high porosity and transparency. The same approach turned o be appropriate for other systems like GdF3 or hybrid aerogels of YAG:Ce and GdF3.Alternatively, YAG:Ce NPs were incorporated into silica aerogels forming robust macroscopic and highly transparent aerogels exhibiting properties of incorporated NPs. They served for novel type of sensors for low-energy ionizing radiation in liquids and gases. Their high porosity assured well-developed contact between radioactive emitter and the scintillator ensuring good harvesting of radioactive energy

APA, Harvard, Vancouver, ISO, and other styles

22

Mutinda, Samuel I. "Hydrothermal Synthesis of Shape/Size-Controlled Cerium-Based Oxides." Youngstown State University / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=ysu1378917332.

Full text

APA, Harvard, Vancouver, ISO, and other styles

23

Al, Ammar Tarek Ahmed [Verfasser], Anja-Verena [Gutachter] Mudring, and Anjana [Gutachter] Devi. "Sonochemical synthesis and characterization of metal oxides nanoparticles in ionic liquids / Tarek Ahmed Al Ammar ; Gutachter: Anja-Verena Mudring, Anjana Devi." Bochum : Ruhr-Universität Bochum, 2012. http://d-nb.info/1131354524/34.

Full text

APA, Harvard, Vancouver, ISO, and other styles

24

Kukkola, J. (Jarmo). "Gas sensors based on nanostructured tungsten oxides." Doctoral thesis, Oulun yliopisto, 2013. http://urn.fi/urn:isbn:9789526202082.

Full text

Abstract:

Abstract The aim of this thesis is to study whether nanostructured particles of WO3 could be competitive counterparts of traditional, more bulky materials in resistive gas sensor applications. Pristine and various surface decorated derivatives of three different types of WO3 nanoparticles applied on the surface of lithographically defined Si chips were used in the work to analyse the electrical behaviour of thin films when exposed to different gas atmospheres. Nanosized particles of WO3, obtained by capillary force-induced collapse of porous anodic tungsten oxide in water, were demonstrated as a sensing medium for the detection of H2 and NO analytes. Commercially available nanoparticles of WO3 were also studied. After decorating their surface with metal/metal oxide nanoparticles (Ag, PdOx and PtOx), stable aqueous dispersions were made and used for the inkjet printing of conductive patterns on test chips. Surface decoration was found to affect substantially the gas response behaviour of the materials with the largest differences in response to H2 and NO. The third type of tungsten oxide applied consisted of hydrothermally synthesized nanowires that were also surface decorated with PdO as well as with PtOx. The nanowires were suspended in water and drop cast on test chips for gas sensing measurements. The nanowire based devices allowed ultrasensitive detection of H2 even at room temperature. The results summarized in this thesis indicate that resistive gas sensors based on nanostructured tungsten oxides are excellent alternatives to existing devices utilizing porous thick films or bulky thin films. Their high sensitivity, low operating temperature and low electrical power consumption may enable the construction of portable sensors, for example by inkjet printing, thus having great potential for fast prototyping but also for large scale production at low cost
Tiivistelmä Väitöstyön tavoitteena on tutkia nanorakenteisten WO3 hiukkasten kilpailukykyä suhteessa perinteisiin suuremman kidekoon materiaaleihin resistiivisissä kaasusensorisovelluksissa. Työssä tutkittiin kolmella eri tekniikalla valmistettujen WO3 nanopartikkeleiden alkuperäisistä ja pintakäsitellyistä versioista muodostettujen ohutkalvojen sähköisiä ominaisuuksia erilaisten kaasukehien funktiona. Veden kapillaarivoimien aikaan saaman huokoisen anodisen volframioksidirakenteen romahduksen kautta saatujen WO3 nanopartikkeleiden osoitettiin toimivan havaintoväliaineena H2 ja NO kaasuille. Myös kaupallisia WO3 nanopartikkeleita tutkittiin. Partikkelien pinta päällystettiin metalli- ja metallioksidinanopartikkeleilla (Ag, PdOx and PtOx), jonka jälkeen niistä muodostettiin vakaita vesipohjaisia seoksia johtavien kuvioiden mustesuihkutulostukseen testisubstraateille. Pintakäsittelyn havaittiin vaikuttavan merkittävästi materiaalien kaasuvasteisiin erityisesti H2:n ja NO:n tapauksessa. Kolmannen tyyppinen väitöskirjassa tutkittu volframioksidimateriaali koostuu hydrotermisesti syntetisoiduista nanojohdoista, jotka ovat pintakäsitelty PdO tai PtOx nanopartikkeleilla. Nanojohdot sekoitettiin veteen ja pipetoitiin testisubstraateille kaasumittauksia varten. Tämän tyyppiset kaasusensorit olivat erityisen herkkiä H2 kaasulle jopa huoneenlämmössä. Väistökirjan tulosten mukaan nanorakenteiset volframioksidimateriaalit ovat erinomainen vaihtoehto perinteisille huokoisille paksukalvoille ja suhteellisen paksuille ohutkalvoille kaasusensorisovelluksissa. Niiden suuri herkkyys, alhainen toimintalämpötila ja matala sähkönkulutus voivat mahdollistaa kannettavien kaasusensorien valmistuksen, esimerkiksi mustesuihkuteknologilla, nopeaan testaukseen ja suuren mittakaavan tuotantoon alhaisin kustannuksin

APA, Harvard, Vancouver, ISO, and other styles

25

Colombo, A. "PREPARATION AND PERFORMANCE EVALUATION OF MATERIALS FOR ELECTROCATALYTIC APPLICATIONS." Doctoral thesis, Università degli Studi di Milano, 2010. http://hdl.handle.net/2434/150125.

Full text

Abstract:

This PhD thesis is devoted to the preparation and characterization of materials for electrocatalytic applications. The focus has been on the surface of electrodes. The physical and chemical structure of surfaces is one of the main variables of electrocatalytic properties. In particular, the physical structure of a surface (amorphous vs. crystalline) is often claimed to affect the surface activity of electrocatalysts. Also, the chemical structure (active sites on flat vs. stepped facets) has been claimed to be an essential variable influencing catalysis as well as electrocatalysis. Scrutiny of both situations was performed in our laboratory by preparing a series of transition metals oxides (e.g. Ir, Ru, Ni, Co) used in electrochemically activate electrodes, for the reactions of hydrogen and oxygen evolution. A number of techniques have been used: i) electrochemical (CV, polarization); ii) non electrochemical (XRD, TGA, SEM, EDX). Two novel synthetic methods for the production of metal oxides nanoparticles have been implemented.

APA, Harvard, Vancouver, ISO, and other styles

26

Adireddy, Shivaprasad Reddy. "High Yield Solvothermal Synthesis of Hexaniobate Based Nanocomposites via the Capture of Preformed Nanoparticles in Scrolled Nanosheets." ScholarWorks@UNO, 2013. http://scholarworks.uno.edu/td/1726.

Full text

Abstract:

The ability to encapsulate linear nanoparticle (NP) chains in scrolled nanosheets is an important advance in the formation of nanocomposites.These nanopeapods (NPPs) exhibit interesting properties that may not be achieved by individual entities. Consequently, to fully exploit the potential of NPPs, the fabrication of NPPs must focus on producing composites with unique combinations of morphologically uniform nanomaterials. Various methods can produce NPPs, but expanding these methods to a wide variety of material combinations can be difficult. Recent work in our group has resulted in the in situ formation of peapod-like structures based on chains of cobalt NPs. Building on this initial success, a more versatile approach has been developed that allows for the capture of a series of preformed NPs in NPP composites. In the following chapters, various synthetic approaches for NPPs of various material combinations will be presented and the key roles of various reaction parameters will be discussed. Also, uniform hexaniobate nanoscrolls were fabricated via a solvothermal method induced by heating up a mixture of TBAOH, hexaniobate crystallites, and oleylamine in toluene. The interlayer spacing of the nanoscrolls was easily tuned by varying the relative amount and chain lengths of the primary alkylamines. To fabricate NPPs, as-synthesized NPs were treated with hexaniobate crystallite in organic mixtures via solvothermal method. During solvothermal treatment, exfoliated hexaniobate nanosheets scroll around highly ordered chains of NPs to produce the target NPP structures in high yield. Reaction mixtures were held at an aging temperature for a few hours to fabricate various new NPPs (Fe3O4@hexaniobate, Ag@hexaniobate, Au@hexaniobate, Au-Fe3O4@hexaniobate, TiO2@hexaniobate, CdS@hexaniobate, CdSe@hexaniobate, and ZnS@hexaniobate). This versatile method was first developed for the fabrication of magnetic peapod nanocomposites with preformed nanoparticles (NPs). This approach is effectively demonstrated on a series of ferrite NPs (≤ 14 nm) where Fe3O4@hexaniobate NPPs are rapidly (~ 6 h) generated in high yield. When NP samples with different sizes are reacted, clear evidence for size selectivity is seen. Magnetic dipolar interactions between ferrite NPs within the Fe3O4@hexaniobate samples leads to a significant rise in coercivity, increasing almost four-fold relative to free particles. Other magnetic ferrites NPPs, MFe2O4@hexaniobate (M = Mn, Co, Ni), can also be prepared. This synthetic approach to nanopeapods is quite versatile and should be readily extendable to other, non-ferrite NPs or NP combinations so that cooperative properties can be exploited while the integrity of the NP assemblies is maintained. Further, this approach demonstrated selectivity by encapsulating NPs according to their size. The use of polydispersed NP systems is also possible and in this case, evidence for size and shape selectivity was observed. This behavior is significant in that it could be exploited in the purification of inhomogeneous NP samples. Other composite materials containing silver and gold NPs are accessible. Partially filled Fe3O4@hexaniobate NPPs were used as templates for the in situ growth of gold to produce the bi-functional Au- Fe3O4@hexaniobate NPPs. Encapsulation of Ag and Au NP chains with a hexaniobate nanoscroll was shifted the surface plasmon resonance to higher wavelengths. In these composites NPs can be incorporated to form NPP structures, decorated on nanosheets before scrolling, or attached to the surfaces of the nanoscrolls. The importance of this advancement is the promise it holds for the design and assembly of active nanocomposites. One can create important combinations of nanomaterials for potential applications in a variety of areas including catalysis, solar conversion, thermoelectrics, and multiferroics.

APA, Harvard, Vancouver, ISO, and other styles

27

ANTONIASSI, RODOLFO M. "Preparação de nanopartículas de platina com diferentes morfologias nos materiais Pt/C e PtSnO2/C para aplicação como ânodo em células a combústível de etanol direto." reponame:Repositório Institucional do IPEN, 2017. http://repositorio.ipen.br:8080/xmlui/handle/123456789/28036.

Full text

Abstract:

Submitted by Pedro Silva Filho (pfsilva@ipen.br) on 2017-11-22T16:42:40Z No. of bitstreams: 0
Made available in DSpace on 2017-11-22T16:42:40Z (GMT). No. of bitstreams: 0
Neste trabalho foi estudado o efeito da adição de íons haletos (Cl-, Br- e I-) sobre a morfologia das nanopartículas de Pt na produção de catalisadores de Pt/C e PtSnO2/C. Foi desenvolvida uma metodologia de síntese simples capaz de produzir nanopartículas de Pt predominantemente cúbicas com orientação preferencial Pt(100), diretamente suportadas em carbono sem o uso de agentes estabilizantes. Brometo de potássio foi utilizado como agente direcionador de superfície para obtenção do material preferencialmente orientado. O controle de adição do precursor de Pt e de KBr foi crucial para obter nanocubos de Pt de 8 nm bem dispersos sobre o suporte. Na preparação dos catalisadores de PtSnO2/C, o processo de adição do SnCl2 também foi decisivo na obtenção das nanopartículas de Pt com tamanho e morfologia de interesse. Nanocubos de Pt coexistindo com SnO2 disperso foram exclusivamente obtidos ao adicionar o SnCl2 na etapa final da síntese, quando as nanopartículas cúbicas de Pt já estavam formadas. Enriquecidos de domínios Pt(100), os materiais em forma cúbica de Pt/C e PtSnO2/C se mostraram menos afetados pelo acúmulo dos intermediários indesejados provenientes da reação de eletro-oxidação de etanol e foram mais tolerantes ao envenenamento por monóxido de carbono. Resultados similares foram observados para a oxidação de CO e metanol, utilizados como apoio para compreensão da eletro-oxidação de etanol. O efeito morfológico destes materiais no desempenho elétrico em célula a combustível de etanol direto foi avaliado. Pt/C e PtSnO2/C contendo nanopartículas de Pt com orientação preferencial Pt(100) forneceram maiores valores de densidade de potência e de seletividade para CO2 comparados aos catalisadores de Pt/C e PtSnO2/C com nanopartículas de Pt sem orientação preferencial.
Tese (Doutorado em Tecnologia Nuclear)
IPEN/T
Instituto de Pesquisas Energéticas e Nucleares - IPEN-CNEN/SP

APA, Harvard, Vancouver, ISO, and other styles

28

Queiroz, Adriana Coêlho. "Síntese e estudo da atividade eletrocatalítica de óxidos de metais de transição e de nanopartículas de prata e ouro para a reação de redução de oxigênio." Universidade de São Paulo, 2011. http://www.teses.usp.br/teses/disponiveis/75/75131/tde-25102011-170304/.

Full text

Abstract:

A reação de redução de oxigênio (RRO) foi estudada em eletrocatalisadores formados por nanopartículas de óxidos puros e mistos de metais de transição de Mn, Co e Ni, além de estrutura tipo espinel, e por nanopartículas de Ag, Au e Ag3M (M= Au, Pt, Pd e Cu) suportadas em carbono Vulcan, em eletrólito alcalino. Os óxidos de metais de transição foram sintetizados por decomposição térmica de seus respectivos nitratos e as nanopartículas a base de prata e ouro foram sintetizadas por redução química com borohidreto. Os eletrocatalisadores foram caracterizados por Difratometria e Espectroscopia de Absorção de Raios X (somente para os óxidos de transição). Os materiais a base de óxidos de manganês, mostraram-se com alta atividade para a RRO, para os quais os resultados espectroscópicos in situ evidenciaram a ocorrência da redução do Mn(IV) para Mn(III), na região de início da RRO. Assim, as atividades eletrocatalíticas foram associadas à ocorrência da transferência de elétrons do Mn(III) para o O2. Entretanto, apresentaram forte desativação após ciclagem potenciodinâmica, o que foi associado à formação da fase Mn3O4, conforme indicado por difratometria de Raios X, após os experimentos eletroquímicos, que é eletroquimicamente inativa. Já o material formado pela estrutura do tipo espinel de MnCo2O4 apresentou alta atividade e estabilidade frente à ciclagem e à RRO. A alta atividade eletrocatalítica foi relacionada a ocorrência do par redox CoII/CoIII em maiores valores de potencial em relação ao CoOx e MnOx, devido a interações entre os átomos de Co e Mn no reticulo espinélico. Contrariamente ao observado nos óxidos com maior quantidade de manganês, o espinel mostrou-se altamente estável, o que foi associada à não alteração de sua estrutura no intervalo de potenciais que a RRO ocorre. Para os materiais bimetálicos a base de prata e ouro, os experimentos eletroquímicos indicaram maior atividade eletrocatalítica para o material de Ag3Au/C. Neste caso, a alta atividade foi associada a dois efeitos principais: (i) a um efeito sinergético, no qual os átomos de ouro atuam na região de ativação, favorecendo a adição de hidrogênio e os átomos vizinhos de prata proporcionam a quebra da ligação O-O, conduzindo a RRO pelo caminho de quatro elétrons por molécula de O2; (ii) ao aumento força da ligação Ag-O, devido à interação da Ag com o Au, resultando em maior atividade para a quebra da ligação O-O, aumentando a atividade da Ag para a RRO, em relação à atividade da Ag pura. Assim, a RRO apresentou menor sobrepotencial e maior número de elétrons em Ag3Au/C, quando comparado com as demais nanopartículas bimetálicas.
The oxygen reduction reaction (ORR) was studied on electrocatalysts composed by pure and mixed transition metal oxides of Mn, Co, and Ni, including spinel-like structures, and by Ag, Au, and Ag3M/C (M= Au, Pt, Pd e Cu) bimetallic nanoparticles, in alkaline electrolyte. The transition metal oxides were synthesized by thermal decomposition of their nitrates, and the silver and gold-based nanoparticles by chemical reduction using borohydride. The electrocatalysts were characterized by X-Ray Diffraction and X-Ray Absorption Spectroscopy (in the case of the metal oxides). The manganese-based oxide materials showed high activity for the ORR, in which the in situ spectroscopic results evidenced the Mn(IV) to Mn(III) reduction, in the range of the ORR onset. In this case, the electrocatalytic activities were correlated to the transfer of electron from Mn(III) to O2. However, they presented strong deactivation after several potentiodynamic cycles, which was ascribed to the formation of the electrochemically inactive phase of Mn3O4, as indicated by the XRD results, after the electrochemical experiments. On the other hand, the MnCo2O4 spinel-like material showed high activity and stability for the ORR. Its high electocatalytic activity was attributed to the CoII/CoIII redox pair, taking place at higher potentials, in relation to that of the CoOx e MnOx pure phases, due to the Co and Mn interactions in the spinel lattice. Contrarily to the behavior observed for the manganese-based materials, the spinel oxide presented high stability, which was ascribed to the non alteration of its crystallographic structure in the range of potentials tha the ORR takes place. For the Au and Ag-based materials, the electrochemical experiments indicated higher electrocatalytic activities for Ag3Au/C. In this case, its higher activity as associated to two main aspects: (i) to a synergetic effect, in which the gold atoms act in the activation region, facilitating the hydrogen addition, and the neighboring Ag atoms promoting the O-O bond breaking, leading the ORR to the 4-electrons pathway; (ii) to the increased Ag-O bond strength, due to the electronic interaction between Ag and the Au atoms, resulting in a faster O-O bond breaking, enhancing the electrocatalytic activity of the Ag atoms in the Ag3Au/C nanoparticle, in relation to that on the pure Ag. Therefore, the ORR presented lower overpotential and higher number of electrons in the Ag3Au/C electrocatalyst, when compared to the other investigated bimetallic nanoparticles.

APA, Harvard, Vancouver, ISO, and other styles

29

Barton, Lauren Elizabeth. "Fate and Transformation of Metal-(Oxide) Nanoparticles in Wastewater Treatment." Diss., Aix-Marseille, 2014. http://hdl.handle.net/10161/8661.

Full text

Abstract:

The study and application of materials possessing size dimensions in the nano scale range and, as a result, unique properties have led to the birth of a new field; nanotechnology. Scientists and engineers have discovered and are exploiting the novel physicochemical characteristics of nanoparticles (NPs) to enhance consumer products and technologies in ways superior to their bulk counterparts. Escalating production and use of NPs will unavoidably lead to release and exposure to environmental systems. This introduction of emerging potential contaminant NPs will provide new and interesting challenges for exposure and risk forecasting as well as environmental endurance.

The ultimate goal of this research is to develop a framework that incorporates experimental and computational efforts to assess and better understand the exposure of metal and metal-oxide NPs released to wastewater treatment plants (WWTPs) and further implications on land application units (LAUs) where biosolids can be applied. The foundation of the computational effort is comprised of Monte Carlo mass balance models that account for the unique processes affecting NP fate and transport through the different technical compartments of a WWTP and LAU. Functional assay and bioreactor experiments in environmental media were used to determine parameters capable of describing the critical processes that impact the fate of NPs in wastewater.

The results of this research indicate that a simplified, but still environmentally relevant nano-specific exposure assessment is possible through experimentation to parameterize adapted models. Black box modeling efforts, which have been shown in previous studies, show no disadvantage relative to discretization of technical compartments as long as all key transport and fate mechanisms are considered. The distribution coefficient (_), an experimentally determined, time-dependent parameter, can be used to predict the distribution of NPs between the liquid and solid phase in WWTPs. In addition, this parameter can be utilized a step further for the estimation of the more fundamental, time independent attachment efficiency between the NPs and the solids in wastewater. The NP core, size, and surface coating will influence the value of these parameters in addition to the background particle characteristics as the parameters are specific to the environmental system of study. For the metal and metal-oxide NPs studied, preferential overall association of approximately 90% or greater with the solid phase of wastewater was observed and predicted.

Furthermore, NP transformations including dissolution, redox reactions, and adsorption can potentially impact exposure. For example, experimental results showed that nano-CeO2 is reduced from Ce(IV) to Ce(III) when in contact with wastewater bacteria where Ce2S3 will likely govern the Ce(III) phase in biosolids. From the literature, similar transformations have been observed with Ag and ZnO NPs to Ag2S and ZnS. With respect to TiO2 NPs, studies indicated that due to high insolubility, these NPs would not undergo transformation in WWTPs. The distribution and transformation rate coefficients can then be used in fate models to predict the NP species exposed to aquatic and terrestrial systems and environmentally relevant concentrations released from WWTPs.

Upon completion of the WWTP model, the predicted concentrations of NPs and NP transformation byproducts released in effluent and biosolids were attainable. A simple mass balance model for NP fate in LAUs was then developed to use this output. Results indicate that NP loading on LAUs would be very low but that build up over time to steady state could result in mass concentrations on the order of the typical level for the background metal in soil. Transport processes of plant uptake and leaching were expected to greatly impact the solid phase concentration of the NPs remaining in the LAU, while rainfall did not impart a significant influence upon variation between low and high annual amounts. The significance of this research is the introduction of a method for NP exposure assessment in WWTPs and subsequently in LAUs. This work describes and quantifies the key processes that will impact Ag, TiO2, CeO2 and ZnO NP fate and transport, which can inform future studies, the modeling community and regulatory agencies.

Dissertation

APA, Harvard, Vancouver, ISO, and other styles

30

Mohammad, Hasan Abid Urf Turabe Ali. "Ammonia gas adsorption on metal oxide nanoparticles." Thesis, Kansas State University, 2011. http://hdl.handle.net/2097/13094.

Full text

Abstract:

Master of Science
Department of Mechanical and Nuclear Engineering
Steven J. Eckels
NanoActiveTM metal oxide particles have the ability to destructively adsorb organophosphorus compounds and chlorocarbons. These nanomaterials with unique surface morphologies are subjected to separate, low concentrations of gaseous ammonia in air. NanoActiveTM materials based on magnesium oxide have large specific surface areas and defective sites that enhance surface reactivity and consequently improved adsorptivity. In gas contaminant removal by adsorption, presence of vast specific surface area is essential for effective gas-solid interaction to take place. This is also the case in many industrial and chemical applications such as purification of gases, separation and recovery of gases, catalysis etc,. Typically carbonaceous compounds are utilized and engineered in toxic gas control systems. The purpose of this study was to compare NanoActiveTM materials with carbon based compounds in the effectivity of toxic gas adsorption at low concentrations. A test facility was designed to investigate the adsorption properties of novel materials such as adorption capacity and adsorption rate. Adsorption capacity along with adsorption kinetics is a function of properties of the adsorbent and the adsorbate as well as experimental conditions. Nanomaterials were placed on a silica matrix and tested with increasing flow rates. Electrochemical sensing devices were placed at inlet and outlet of the facility to monitor real time continuous concentration profiles. Breakthrough curves were obtained from the packed bed column experiments and saturation limits of adsorbents were measured. Adsorption rates were obtained from the breakthrough curves using modified Wheeler-Jonas equation. The NanoActiveTM materials adsorbed ammonia though to a lesser extent than the Norit® compounds. This study also included measurement of pressure drop in packed beds. This information is useful in estimating energy losses in packed bed reactors. Brauner Emmet Teller tests were carried out for the calculation of surface area, pore volume and pore size of materials. These calculations suggest surface area alone had no notable influence on adsorption capacity and adsorption rates. This lead to the conclusion that adsorption was insignificant cause of absence of functional groups with affinity towards ammonia. In brief, adsorption of ammonia is possible on NanoActiveTM materials. However functional groups such as oxy-flouro compounds should be doped with novel materials to enhance the surface interactions.

APA, Harvard, Vancouver, ISO, and other styles

31

Santos, Neto Manoel Domingos dos. "Avaliação da atividade antitumoral e capacidade de reversão do fenótipo MDR de nanopartículas de óxido de zinco funcionalizadas com L-glutamina." reponame:Repositório Institucional da UFABC, 2015.

Find full text

Abstract:

Orientadora: Profa. Dra. Ana Carolina Santos de Souza Galvão
Nanoparticulas derivadas de oxidos metalicos, em suas formas livres ou associadas a moleculas organicas ou drogas antineoplasicas, tem sido empregadas no diagnostico e tratamento do cancer. Neste cenario, destaca-se o uso de oxidos nanoestruturados derivados de zinco. Recentes estudos demonstraram a capacidade de nanoparticulas de ZnO, individualmente ou em associacao a agentes quimioterapicos, de sensibilizacao de celulas tumorais resistentes a multiplas drogas (fenotipo MDR), que possuem em sua membrana proteinas de efluxo que impedem o acumulo destas drogas no interior das celulas. A falta de seletividade e dificuldade de internalizacao pelas celulas de alguns compostos utilizados no tratamento de cancer, sao considerados os maiores empecilhos para o tratamento quimioterapico, tornando a modificacao da superficie de materiais nanoestruturados com atividade antitumoral, atraves da funcionalizacao, forma de aumentar a incorporacao e consequente atividade citotoxica destes compostos em celulas tumorais. Neste trabalho, as nanoparticulas foram funcionalizadas com L-glutamina, devido a grande importancia deste aminoacido no metabolismo de celulas cancerigenas e ao fato destas apresentarem maior captacao desse aminoacido que celulas nao tumorais. A citotoxicidade de nanoparticulas funcionalizadas com L-glutamina ou nao funcionalizadas foi avaliada em celulas de leucemia mieloide cronica K562 e sua versao com fenotipo MDR Lucena-1. A atividade citotoxica de ZnO foi comprovada pelos ensaios de exclusao de Trypan Blue e reducao de MTT, com IC50 de 20 evalencia de dupla marcacao nas celulas K562 tratadas com as nanoparticulas ZnO e ZnO_Gln, enquanto que para Lucena-1 observou-se porcentagens semelhantes de celulas duplamente marcadas e marcadas apenas com Anexina V. Para avaliar se ha influencia de especies reativas de oxigenio (EROs), geradas peLucena-1. Atraves das analises das possiveis vias de morte celular via analise de Western Blotting, estudando principalmente as proteinas e os eventos envolvidos no processo de morte celular programada (Bcl2, Bad, Bid, Caspase-3 e PARP) e autofagia (Beclin-1 e P62), observou-se que mais de uma via de morte foi ativada nas celulas tratadas com as nanoparticulas, o que corrobora com o descrito em literatura, considerando autofagia e apoptose sao as principais vias de morte ativadas pela acao citotoxica das nanoparticulas de ZnO. Outro evento observado foi a alteracao da atividade da proteina PgPieloide cronica K562 e a linhagem com fenotipo MDR Lucena-1 e a utilizacao deste aminoacido na funcionalizacao de nanomateriais pode ser uma importante ferramenta a ser explorada.
Tese (doutorado) - Universidade Federal do ABC, Programa de Pós-Graduação em Biossistemas, 2015.
Nanoparticles derived from metal oxides, in their free forms or associated with organic molecules or antineoplastic drugs, have been employed in the diagnosis and treatment of cancer. In this scenario, we highlight the use of zinc-based nanostructured oxides. Recent studies demonstrated the ability of ZnO nanoparticles, alone or in combination with chemotherapeutic agents, sensitization of tumor cells multidrug resistant (MDR phenotype), which have on their membrane efflux proteins that prevent the accumulation of these drugs within cells. The lack of selectivity, and difficulty internalization by cells of some compounds used in the treatment of cancer, are considered the major obstacles to chemotherapy, making the nanostructured surface modification of materials having anti-tumor activity through the functionalization way to increase the cytotoxic activity and subsequent incorporation of these compounds in tumor cells. In this work, the nanoparticles were functionalized with L-glutamine, due to the great importance of this amino acid in cancer cell metabolism and the fact that these have higher uptake of this amino acid to non-tumor cells. The cytotoxicity of nanoparticles functionalized with L-glutamine functionalized or not was evaluated in chronic myelogenous leukemia cells K562 and its version with MDR phenotype-Lucena 1. The cytotoxic activity of ZnO was confirmed by Trypan Blue exclusion and MTT reduction assays, with IC50 of 20 d K562 with ZnO nanoparticles and ZnO_Gln, while for Lucena-1 was observed similar percentages of doubly labeled cells and marked only with Annexin V. To assess whether there is influence of reactive oxygen species (ROS) generated by nanoparticles of ZnO and ZnO_Gln in their cytotoxic activity in ceC promoted protection against the cytotoxicity of nanoparticles even in higher concentrations of nanoparticles (30 ug / ml) in both the lines cell. In the potentiation of cell death caused by ZnO nanoparticles in cell lines studied, functionalization with L-glutamine promoted greater incorporation o562 cells treated with pure functionalized nanoparticles and in relation to the control compared to cells of Lucena-1 strain. Through analysis of the possible ways of cell death via Western blot analysis, the proteins and particularly studying the events involved in programmed cell death (Bcl2, Bad, Bid, caspase-3 and PARP) and autophagy (beclin-1 and P62), there was more than one death pathway was activated in cells treated with nanoparticles, which corroborates with what is described in literature, considering autophagy and apoptosis are the main routes of death activated cytotoxic action ofytotoxic effect of ZnO in the chronic myelogenous leukemia line K562 and the line Lucena MDR-1 phenotype and use this amino acid in the functionalization of nanomaterials can be an important tool to be exploited.

APA, Harvard, Vancouver, ISO, and other styles

32

Aksomaityte, Gabriele. "Synthesis of metal and metal oxide nanoparticles in supercritical fluids." Thesis, University of Nottingham, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.523001.

Full text

APA, Harvard, Vancouver, ISO, and other styles

33

Tejpal, Jyoti. "The use of metal and metal oxide nanoparticles against biofilms." Thesis, De Montfort University, 2016. http://hdl.handle.net/2086/13114.

Full text

Abstract:

The persistence of biofilms in hospital settings are associated with Healthcare Associated Infections (HCAI), causing increased morbidity, mortality and healthcare costs. The resistance of biofilms against commonly used hospital disinfectants has been well reported. Metal and metal oxide nanoparticles (NP) such as silver (Ag), copper (Cu), zinc oxide (ZnO) and copper oxide (CuO) exhibit antimicrobial properties against various pathogens. Methods: Biofilm formation of Pseudomonas aeruginosa and Staphylococcus aureus in a Centre for Disease Control (CDC) biofilm reactor and a 96 well plate was compared. A three stage approach including Minimum Biofilm Reduction Concentration (MBRC), R2 values and log(10) reductions was used to assess the efficacy of Ag and ZnO NPs both alone and in combination against P. aeruginosa and S. aureus biofilms. Atomic Absorption Spectroscopy (AAS), Scanning Electron Microscopy (SEM) and Confocal Laser Scanning Microscopy (CLSM) was used to further assess the antimicrobial ability of the metal and metal oxide NPs. The prevention of P. aeruginosa and S. aureus adherence on Ag and ZnO thin film coating on silicon (Si) surfaces was also investigated, as well as icaC, ebpS and fnbB gene expression in S. aureus biofilms. Results: The CDC biofilm reactor demonstrated to be the most effective method for P. aeruginosa and S. aureus biofilm production in comparison to 96 well plates, with lower standard errors of the mean (SE) and higher replicability. Individual MBRC of ZnO and Ag NPs in suspension were 256 and 50 µg/ml for P. aeruginosa and 16 and 50 µg/ml for S. aureus respectively. The concentrations in combination were reduced by at least a half, with concentrations of 32/25 µg/ml of ZnO/Ag NPs in suspension resulting in a significant (p ≤0.05) reduction of 3.77 log(10) against P. aeruginosa biofilms and 8/12 µg/ml of ZnO/Ag NPs in suspension resulted in a 3.91 log(10) (p ≤0.05) against S. aureus biofilms. Both combinations showed an additive effect. Time point analysis confirmed that a 24 hour treatment is vital for any significant (p ≤0.05) antimicrobial activity. AAS data suggested that the Ag+ ions quenched Zn2+ ions, therefore the antimicrobial efficacy of the combination is mainly due to Ag+ ions. Damage of the biofilms from Ag and ZnO NPs was observed in the SEM imaging and energy dispersive X-ray (EDX) analysis confirmed the adherence of Zn and Ag within the biofilms. CLSM imaging showed dead (red) cells of P. aeruginosa and S. aureus biofilms throughout the depth of the biofilm. P. aeruginosa formation was reduced by 1.41 log(10) and 1.43 log(10) on Ag and ZnO thin film coatings respectively. For S. aureus, a reduction of 1.82 log(10) and 1.65 log(10) was obtained for Ag and ZnO coating respectively. Only low levels of ribonucleic acid (RNA) were achieved so no further gene analysis could occur. Conclusion: Reductions of ≥3 log(10) were observed for P. aeruginosa and S. aureus biofilm treatment with ZnO/Ag NP suspensions. It can be concluded that the ZnO/Ag NP suspensions had greater antimicrobial activity than Ag and ZnO coated surfaces owing to large concentrations of Ag+ and Zn2+ ions acting upon the biofilms. The slower release of ions from coated surfaces suggest an inadequate concentration of ions in the media, which are therefore unable to prevent biofilm formation as rapidly as NP suspensions, however provide a sustained release of ions over time. The results from this investigation propose that Ag and ZnO NPs in suspension could be a potential alternative to disinfectants for use in nosocomial environments against P. aeruginosa and S. aureus biofilms.

APA, Harvard, Vancouver, ISO, and other styles

34

Gu, Yanjuan, and 谷艳娟. "Nanostructure of transition metal and metal oxide forelectrocatalysis." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2006. http://hub.hku.hk/bib/B37774396.

Full text

APA, Harvard, Vancouver, ISO, and other styles

35

Bonasera, Aurelio. "Design and Synthesis of Perylene-Based Supramolecular Hybrids for Novel Technological Applications." Doctoral thesis, Università degli studi di Trieste, 2015. http://hdl.handle.net/10077/11109.

Full text

Abstract:

2013/2014
Negli ultimi 50 anni, l’uomo ha attribuito un valore crescente alla ricerca scientifica in quanto strumento di innovazione e di evoluzione tecnologica. La Scienza è diventata uno strumento in grado di migliorare la qualità di vita dell’uomo portando svariate migliorie, ma anche di cambiare radicalmente il suo stile di vita a seguito di scoperte e di strumenti sconosciuti prima di allora. Il progresso tecnologico, la crescita della popolazione mondiale e delle sue esigenze ha causato degli squilibri nel nostro pianeta, dovuti soprattutto and una non omogenea distribuzione delle risorse, in primis quelle energetiche. Dunque, il ruolo della ricerca scientifica contemporanea ha assunto un’ulteriore valenza, quello di appianare gli squilibri sociali ed economici del pianeta. La ricerca di nuove risorse energetiche, o di vettori nei quali conservare l’energia, è uno dei campi scientifici più fertili; in accordo con le ultime tendenze, massima importanza è riposta nelle tecnologie in grado di convertire l’energia solare e renderla disponibile sotto altre forme più pratiche (procedure di storage più semplici) o più facilmente manipolabili. La scelta di sfruttare l’energia solare si basa su alcuni presupposti logici: (i) abbondanza, (ii) distribuzione pressoché uniforme dell’energia solare sulla superficie del pianeta, (iii) esempi disponibili nel mondo naturale che possono essere studiati, compresi, migliorati. La fotosintesi clorofilliana è sicuramente il processo naturale maggiormente conosciuto; perpetrato da una fetta consistente di forme di vita (in particolare del mondo vegetale), permette a queste di sfruttare l’energia contenuta nella radiazione solare e trasformare acqua ed anidride carbonica in carboidrati (la loro riserva di energia) ed ossigeno. Ispirandosi a questo modello, la scienza dei materiali è alla continua ricerca di substrati in grado di trasformare la luce solare in altri vettori energetici a partire da sostanze semplici ed ampliamente disponibili. La scissione dell’acqua in idrogeno ed ossigeno molecolari è uno di questi possibili traguardi; l’acqua è estremamente abbondante sul nostro pianeta (ricoprendone ben il 69% della sua superficie), l’idrogeno è un combustibile che promette di sostituire i derivati del petrolio nel prossimo futuro, e l’ossigeno è di estremo interesse in quanto fonte stessa della vita sul nostro pianeta, almeno nella forma da noi conosciuta. Il progetto di ricerca descritto in questa tesi pone le basi su queste premesse. L’obiettivo prefissato è stato quello di progettare, realizzare, caratterizzare e testare materiali in grado di attuare processi fotosintetici. Durante la fase di progettazione, si è stati costretti a ragionare su quale potesse essere la classe di materiali appropriata a tale scopo, e ci si è orientati verso nano-ibridi organici/inorganici per una serie di motivi: (i) le (nano)-dimensioni avrebbero permesso di lavorare con precursori molecolari e pilotare con maggiore facilità la fase sintetica; (ii) questa classe di materiali possiede generalmente elevate aree superficiali; (iii) l’uso di materiali organici ed inorganici avrebbe permesso di scegliere building blocks che potessero offrire ciascuno le caratteristiche migliori della loro classe di appartenenza. Il lavoro di tesi si è dunque articolato in due sezioni fondamentali: • determinazione di una classe appropriata di cromofori capaci di catturare efficientemente la luce solare ed attivare una specie catalitica ad essi accoppiati. Relativamente a questo punto, scopo non secondario è stato quello di sviluppare nuovi cromofori rispetto a quelli attualmente riportati nella letteratura scientifica e/o sviluppare nuovi protocolli di sintesi capaci di migliorare rese ed efficienza dei processi attualmente noti • scelta di una appropriata specie catalitica e sviluppo dei materiali ibridi contenenti il/i fotosensibilizzanti e il/i catalizzatori; una volta isolata la potenziale diade, si sarebbe proceduto con la fase di monitoraggio dell’attività fotocatalitica del nuovo materiale. Nello sviluppo di questo progetto, i derivati peilenici sono stati scelti quali potenziali fotosensibilizzanti in virtù di una interessante combinazione di caratteristiche elettroniche e chimico-fisiche (approfonditi nel Capitolo 2), ed in particolare ci si è concentrati su composti solubili in acqua. Quest’ultimo dettaglio non è da sottovalutare in quanto, nell’ottica di effettuare i test finali di scissione ossidativa dell’acqua, l’uso di composti idrofilici avrebbe permesso di utilizzare al contempo l’acqua quale reagente e mezzo di reazione. Prima giungere a questa fase, la chimica dei perileni è stata scandagliata a fondo, e vari derivati sono stati isolati e caratterizzati utilizzando protocolli di sintesi sia classici che innovativi (Capitolo 4). La parte centrale del lavoro di tesi ha riguardato lo studio delle diadi costituite da uno dei perileni isolati (PBI2+) e due diversi catalizzatori: (i) Ru4POM, catalizzatore molecolare a base di rutenio, testato per esperimenti sia in fase omogenea che per la realizzazione di un ibrido tri-componente per futuri studi di elettrocatalisi (Capitoli 5-6); (ii) nanoparticelle di ossido di iridio per la preparazione di fotoanodi da applicare in celle fotoelettrochimiche (Capitolo 7). La confidenza acquisita coi derivati perilenici ha permesso di sviluppare anche progetti paralleli che non riguardassero applicazioni in ambito energetico; un dettagliato studio di perileni bisimmidi quali SERS markers è trattato nella parte finale di questa tesi (Capitolo 8).
In the last half-century, scientific evolution allowed humanity to reach important goals; probably the highest impact factor is related to bio-medical conquests, but the acquired knowledge in physics, chemistry and in material science for sure produced several devices which radically changed humanity life-style. Among all, electronics and electronic devices are deeply present in humanity ordinary life and in its new habits. However, an increased interest in scientific research recently rose due to some global problems and challenges that humanity has to face. The high energy demand characterizes Modern Age, and the rapid economic evolution of some areas of the World have caused (and continue to cause) social instability and tension at global level. For this reason, scientific research is focusing more and more on the development of solar devices able to store or eventually manipulate solar energy in other energetic vectors. Interest around solar energy is related to three considerations: basically, it is (i) abundant all over Earth’s surface, (ii) it is uniformly distributed, and (iii) Nature already offers some examples from which it is possible to take inspirations. Natural Photosynthesis is a process (or better a sequence of processes) which has been deeply understood after decades of basic research; this is also the most well-known example of solar light conversion operated from living beings (mainly vegetables) into a new energetic vector (carbohydrates) starting from simple and abundant raw materials (water and carbon dioxide). Material Science is particularly involved in the design of novel materials able to emulate natural photosynthesis and/or perform similar processes; water splitting has a prominent role because its decomposition in molecular hydrogen and oxygen offers the possibility to produce two precious chemical species. Hydrogen is currently the most credited candidate for the substitution of petrol and its derivatives as energetic vectors, while oxygen has basilar importance for life in our planet; moreover, water is extremely abundant on the Earth’s surface (almost 69% of the surface is covered from water), thus it is an easy-accessible raw material. The present thesis work roots in the points discussed in this preface; the primary target is the design, realization, characterization and test of novel materials able to act as artificial photosynthetic units. During the design of the materials, it was chosen to privilege the realization of organic/inorganic nanohybrids in order to have materials possessing huge surface area; moreover, the design of hybrid materials would imply the use of molecular building blocks, which could be easily realized with well-established chemical procedures. Preliminary work was necessary for: • the determination of an appropriate class of chromophores able to trap solar light and induce the activation of another unit able to perform the catalytic process. Starting from chromophore molecules already known in the literature, new molecules would be designed and synthesized in order to possess the necessary characteristics emerging from the hybrids design process • the choice of an appropriate catalytic unit, so to be combined with the chromophore units and realize the final dyad to be used in the catalytic tests. During the development of the thesis, perylene derivatives were chosen as potential photosensitizers, on the base of an interesting combination of physical and photochemical features (deeply discussed in Chapter 2). Particular attention was given to water-soluble molecules because, if the final target would be water splitting process, it would be worthy to have the possibility to use water both as reagent and reaction medium. Perylene chemistry was deeply scanned, and several derivatives were isolated in order to gain experience on this family of photosensitizers; classical reported procedures were employed, but also novel strategies were tested (Chapter 4). The main part of the laboratory work concerned the characterization of novel dyads based on the combination of PBI2+, one of the isolated chromophores, and two different catalytic species: (i) Ru4POM, tetra-ruthenate molecular polyoxometalate for performing water splitting in homogeneous conditions and later for the formation of a three-component hybrid system for electrocatalytic studies (Chapters 5-6); (ii) iridium oxide nanoparticles for the preparation of photoelectrochemical cells (Chapter 7). The expertise gained with perylene derivatives allowed to develop other parallel projects not directly related to energetic applications; a detailed study over perylene diimides as SERS reporters is described in the final part of this thesis (Chapter 8).
XXVII Ciclo
1987

APA, Harvard, Vancouver, ISO, and other styles

36

Gu, Yanjuan. "Nanostructure of transition metal and metal oxide for electrocatalysis." Click to view the E-thesis via HKUTO, 2006. http://sunzi.lib.hku.hk/hkuto/record/B37774396.

Full text

APA, Harvard, Vancouver, ISO, and other styles

37

杨纯臻 and Chunzhen Yang. "Metal/metal oxide nanoparticles supported on nanostructured carbons for electrochemical applications." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2013. http://hdl.handle.net/10722/193414.

Full text

Abstract:

Among various electrochemical devices that have been developed for energy storage and conversion, electric double layer capacitors (EDLCs) and direct methanol fuel cells (DMFC) have received much research attention. Nanostructured carbon materials have been playing an important role in the development of these devices, due to such characteristics as good electrical conductivity, high chemical stability, high surface area and large pore volumes and etc. In an EDLC, nanostructured carbon electrodes, possessing pores of varied length scales, can deliver electric energy at high current loadings. This kind of pore structure also benefits the deposition of metal catalysts and the transport of reactants and products in the methanol oxidation reaction. In order to systematically study the structural effects on the electrochemical capacitance and ionic transport, a series of three-dimensional hierarchical carbons with hollow core-mesoporous shell (HCMS) structure were template-synthesized. Periodically ordered macroscopic hollow cores of 330 nm in diameter were surrounded by a mesoporous shell containing uniform pores of 3.9 nm. The shell thickness was stepwise increased from 0, 25, 50 to 100 nm. The HCMS structure was modeled by a 5-level transmission line model to study the capacitance contribution from the pores at different length scale. Results revealed that the HCMS carbon with thicker mesoporous shells can provide high capacitance, while thinner shells could deliver high power output. A series of HCMS carbon sphere supported Pt nanoparticles were synthesized via the “Carbonization over Protected and Dispersed Metal” (CPDM) method. Contrary to the conventional “polyol” synthetic method, whereas most of Pt nanoparticles were deposited on the external surface of carbon spheres; the Pt nanoparticles synthesized via the CPDM method were found encapsulated in the mesoporous carbon shells and highly dispersed throughout the carbon texture. „Accelerated stress tests‟ (ASTs) were conducted to investigate the nanopores confinement effect toward the electrochemical stability of these Pt catalysts. Results revealed that (1) the nanopores confined Pt nanoparticles on HCMS carbon spheres exhibited a stable electrochemical active surface area (ECSA) and catalytic activity; and (2) thick mesoporous carbon shells could provide better protection over the Pt nanoparticles. This “CPDM” method was further extended to synthesize highly alloyed PtRu nanoparticles supported electrocatalysts. It is expected that this CPDM method can also be applied to synthesize other metal/metal oxide supported catalysts with stable electrochemical performance. WO3 has been demonstrated as a promsing co-catalyst for Pt in the methanol oxidation reaction (MOR). The synthesis of Pt-WO3/C catalyst with well-controlled nanoparticle size (2.5 nm) and composition was achieved via a microwave-assisted water-oil microemulsion reaction. Hydrogen adsorption, CO-stripping and Cu- stripping methods were used to estimate the ECSA of Pt in the Pt-WO3/C catalysts. Among these, Cu-stripping method was relatively more reliable due to the overlapping involvement of the WO3 component in the other methods. The methanol oxidation measurement shows that a 1:1 Pt:W ratio catalyst exhibits the highest Pt-mass current density of 271 mA mg-1-Pt, 1.4 times higher than that of commercial E-TEK catalyst.
published_or_final_version
Chemistry
Doctoral
Doctor of Philosophy

APA, Harvard, Vancouver, ISO, and other styles

38

Mundell, V. J. "Synthesis and functionalisation of metal and metal oxide nanoparticles for theranostics." Thesis, Nottingham Trent University, 2013. http://irep.ntu.ac.uk/id/eprint/315/.

Full text

Abstract:

Metal and metal oxide nanoparticles including calcium oxide, gold, and superparamagnetic iron oxide nanoparticles (SPIOs) were synthesised using a range of techniques including reduction, co-precipitation and spinning disc technology. SPIOs were primarily synthesised via a co-precipitation method using iron (II) chloride, iron (III) chloride and ammonia; a spinning disc reactor and gaseous ammonia were trialled successfully for scale up, producing spherical particles of 10-40 nm in diameter as analysed by TEM. Nanoparticles were coated via a novel solvent-free grinding process which was successful for drug molecules, immunogenic peptides and amino acids; the mode of binding theorised to be taking place via an electrostatic interaction between the SPIO and the carboxyl, amine or hydroxyl groups on the coating materials. Recrystallisation of the coating materials to form HCl salts, was found to increase the binding efficiency with no detrimental effects to the particles. These coated SPIOs were found to be stable in a range of buffered solutions as well as blood and cell culture media. Separation of particles by size exclusion chromatography (SEC), dialysis and magnetic separation was only effective for a small range of coatings, with high speed centrifugation at a speed of 60 000 rpm being confirmed as the only universally successful method. Imaging of citrate capped gold nanoparticles using a CT phantom revealed that gold concentrations of 3700 mg.l-1 were required for in vivo use and so this was not continued. Coated SPIOs however produced relaxation times comparable with Endorem®, as well as being non-toxic. SPIOs coated in this way were more stable than Endorem® and stayed in solution retaining their superparamagnetic properties for periods in excess of 72 days with only a negligible degree of degradation. Various peptides were synthesised using an optimised microwave assisted solid-phase peptide synthesis (SPPS) method using double the suggested coupling times, all of which were analysed for purity and structure using MALDI-TOF MS and HPLC. A cell-penetrating peptide (CPP) synthesised via this method was coated onto SPIOs and mixed into a gel for transdermal delivery using porcine skin. An NMR profile of the skin using a 0.25T NMR MOUSE® before and after application of the gel showed that after an incubation period of 2 hrs the CPP-SPIOs had penetrated the skin leading to a reduction in signal. This has potential applications for subcutaneous drug delivery and hyperthermia. Cell studies using U937 and BMDCs indicated by both ICP and fluorescence microscopy that SPIOs coated with fluorescently labelled peptides were successfully taken up into cells. SPIOs were further investigated as vectors for delivery of immunogenic peptides, namely p53(105) using female C57BL/6 mice. Results indicated that mice immunised with SPIO as a vector showed similar levels of immune response to the p53(105) following immunisation as when incomplete Freund’s adjuvant (IFA) was used. However, SPIO immunisations produced a significantly increased specific response compared to the condition using IFA. Results indicate that SPIO could be successful as a vector for cancer vaccines.

APA, Harvard, Vancouver, ISO, and other styles

39

Zapiter, Joan Marie Diangson. "Transition Metal Complexes Anchored on Europium Oxide Nanoparticles." Thesis, Virginia Tech, 2014. http://hdl.handle.net/10919/24786.

Full text

Abstract:

Polypyridyl transition metal complexes containing ruthenium, rhodium and iridium centers are mainly studied due to their light absorbing and emitting properties. Lanthanide oxides such as europium oxide absorb light as well and exhibit strong luminescence and long lifetimes. The optical properties of these materials were significant especially in solar energy utilization schemes and optical applications. Energy transfer across a surface is important in several applications including phosphors and biomedical applications. Excited states of metal complexes with a carboxylate-containing ligand such as deeb = diethyl-2,2'-bipyridine-4,4'-dicarboxylate were studied on nanoparticle surfaces. In this work, [Rh(deeb)2Cl2](PF6), [Ir(deeb)2Cl2](PF6) and [Ir(deeb)2(dpp)](PF6)3 were synthesized using the building block approach. The metal complexes were characterized using 1H NMR spectroscopy, mass spectrometry, electronic absorption spectroscopy and electrochemistry. The 1H NMR spectra of the complexes were consistent with those of their ruthenium analogs. Mass spectra contain fragmentation patterns of the (M-PF6)+ molecular ion for [Rh(deeb)2Cl2](PF6) and [Ir(deeb)2Cl2](PF6), and (M-3PF6)3+ molecular ions for [Ir(deeb)2(dpp)](PF6)3. The electronic absorption spectrum of [Rh(deeb)2Cl2](PF6) shows a maximum at 328 nm, which is assigned as 1π→π*transition. The electronic absorption spectrum of [Ir(deeb)2Cl2](PF6) shows maxima at 308 nm and 402 nm, which are assigned as 1π→π* and metal-to-ligand charge transfer transitions, respectively. The [Ir(deeb)2(dpp)](PF6)3 complex exhibits peaks due to 1π→π* transitions at 322 nm and 334 nm. [Rh(deeb)2Cl2](PF6) has emission maxima from the 3LF state at 680 nm and 704 nm for the solid and glassy solutions at 77 K, respectively. [Ir(deeb)2Cl2](PF6) has emission maxima from the 3MLCT state at 538 nm in acetonitrile and 567 nm in the solid state at room temperature, with lifetimes of 1.71 μs and 0.35 μs, respectively. [Ir(deeb)2Cl2](PF6) has an unusually higher quantum yield than analogous compounds. [Ir(deeb)2(dpp)](PF6)3 has emission maxima from the 3IL state at 540 nm in acetonitrile and 599 nm in the solid state at room temperature, with lifetimes of 1.23 μs and 0.14 μs, respectively. Cyclic voltammetry of [Ir(deeb)2Cl2](PF6) and [Ir(deeb)2(dpp)](PF6)3 yield reversible and quasi-reversible couples corresponding to deeb ligand and Ir3+/+reductions, respectively. Attachment of the complexes were conducted by equilibration of complex solutions in acetonitrile with europium oxide nanoparticles. Europium oxide nanoparticles, which were synthesized by gas-phase condensation, have 11-nm diameters and exhibit sharp f-based luminescence in the visible and near IR regions. EDX, TEM, IR and reflectance spectroscopy measurements indicate substantial coating through various modes of attachment of the nanoparticle surface by the metal complexes while retaining the excited state properties of the metal complexes. Surface adsorption studies indicate monolayer coverage of the nanoparticle surface by the metal complexes, consistent with limiting surface coverages of previously reported analogous systems. Eu2O3 nanoparticles modified with [Rh(deeb)2Cl2]+ exhibit minimal to no energy transfer from emission spectra, and a reduction in the lifetime at 77K could be due to the rhodium complex preventing the excitation of Eu3+. Upon attachment of the Ir complexes [Ir(deeb)2Cl2]+ and [Ir(deeb)2(dpp)]3+ on as-prepared nanoparticles, Eu3+ luminescence was observed for nanoparticles modified with iridium complexes at room temperature, which could be due to energy transfer among other possibilities. Efficiencies of 68% and 50%, and energy transfer rate constants of 1.1 x 10-5 and 1.0 x 10-5 were calculated from lifetime data for [Ir(deeb)2Cl2]+ and [Ir(deeb)2(dpp)]3+ on Eu2O3 nanoparticles, respectively. Since iridium complexes are used as components of light-emitting diodes, europium oxide nanoparticles modified with iridium complexes have potential in optical applications which make studies of these compounds interesting.
Master of Science

APA, Harvard, Vancouver, ISO, and other styles

40

Watson, Venroy George. "Decoration of Graphene Oxide with Silver Nanoparticles and Controlling the Silver Nanoparticle Loading on Graphene Oxide." University of Dayton / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1396879714.

Full text

APA, Harvard, Vancouver, ISO, and other styles

41

Zhang, Ming. "Nonaqueous Synthesis of Metal Oxide Nanoparticles and Their Surface Coating." ScholarWorks@UNO, 2008. http://scholarworks.uno.edu/td/861.

Full text

Abstract:

This thesis mainly consists of two parts, the synthesis of several kinds of technologically interesting crystalline metal oxide nanoparticles via high temperature nonaqueous solution processes and the formation of core-shell structure metal oxide composites using some of these nanoparticles as the core with silica, titania or polymer as shell via a modified microemulsion approach. In the first part, the experimental procedures and characterization results of successful synthesis of crystalline iron oxide (Fe3O4) and indium oxide (In2O3) nanoparticles are reported. Those nanoparticles exhibit monodispersed particle size, high crystallinity and high dispersibility in non-polar solvents. The particle size can be tuned by the seed mediated growth and the particle shape can also be controlled by altering the capping ligand type and amount. The mixed bi-metal oxides such as cobalt iron oxide and lithium cobalt oxide will be discussed as well. In the second part, the synthesis and characterization of various surface coated metal oxides, including silica, titania and polymer coated nanocomposites are reported. The silica coating process is presented as a highlight of this part. By using a microemulsion system, core-shell structure silica coated iron oxide and indium oxide nanocomposites are successfully prepared. Furthermore, the thickness of the silica coating can be controlled from 2 nm to about 100 nm by adjusting the reaction agents of the micelle system. By extending the procedure, we will also discuss the titania and polymer coating preparation and characterization.

APA, Harvard, Vancouver, ISO, and other styles

42

D'Souza, Lawrence [Verfasser]. "Synthesis, characterization and applications of metal and metal oxide nanoparticles / Lawrence D'Souza." Bremen : IRC-Library, Information Resource Center der Jacobs University Bremen, 2008. http://d-nb.info/1034768174/34.

Full text

APA, Harvard, Vancouver, ISO, and other styles

43

McShane, Heather. "Metal oxide nanoparticle chemistry and toxicity in soils." Thesis, McGill University, 2013. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=117105.

Full text

Abstract:

Metal oxide nanoparticles (MONPs) are increasingly being incorporated in domestic and industrial products. They are expected to pass into waste water treatment facilities, and may inadvertently be applied in biosolids to agricultural soils. Very few nanotoxicity studies have been conducted in soils and the risk that MONPs pose to soil organisms are poorly understood. The aim of this study was to investigate the behaviour and effects of two MONPs with different solubilities on terrestrial organisms in soils. Exposure of earthworms to soils amended with up to 10,000 mg/kg nano-sized TiO2, a virtually insoluble nanomaterial, resulted in no adverse effects on earthworm population parameters such as survival or reproduction. Earthworms avoided nano-TiO2 amended soils, but only at nanoparticle concentrations higher than those expected for agricultural soils. The mechanisms resulting in the avoidance response, and nano-TiO2 transformations in soils, could not be further investigated because techniques to track nanoparticles in complex media are lacking. Subsequent studies focused on a sparingly soluble nanomaterial, nano-CuO, which releases Cu2+ ions as it dissolves. To identify nanoparticle-specific effects on organisms, the effects of the Cu2+ ions must be determined but little is known about the effect of nano-CuO on Cu2+ activity in soils. Tests revealed that Cu2+ activity in nano-CuO amended soils increased over a 56 d period, but were not comparable to those in soils amended with similar concentrations of micrometer-sized CuO or Cu(NO3)2, which are commonly used as treatments to control for the effects non-nanosized Cu in nanotoxicity tests. These results have implications for the design of experiments that test effects of dissolving particulates. A subsequent barley growth test demonstrated that there was no significant difference in plant growth or shoot Cu concentrations between soils amended with nano-CuO, micrometer-sized CuO or Cu(NO3)2 once growth was normalised to Cu2+ activity. These results demonstrate that release of metal ions can play an important role in toxicity of soluble metal-based nanoparticles and highlight the importance of direct measurement of potentially toxic products of nanoparticle dissolution. There was no evidence of nanoparticle-specific toxicity under the conditions studied either for earthworms exposed to nano-TiO2 or barley exposed to nano-CuO. The study highlighted some of the challenges of understanding the fate and effects of nanomaterials in soils, including the lack of techniques to track nanomaterials in complex media and the difficulty in designing toxicity tests that control for temporal changes to both nanoparticles and soils.
Les nanoparticules des oxydes de métaux (MONP) sont davantage incorporés dans les produits domestiques et industriels. Une importante proportion de ces nanoparticules est susceptible de se retrouver dans les usines de traitement d'eaux usées et d'être épandue sur les terres agricoles sous forme de biosolides. Dû au fait que peu de recherches sur la nanotoxicité ont été faites dans les sols, le risque que pose ces MONP aux organismes du sols est peu connu. Le but de cette étude est donc d'observer la réaction et les effets de deux MONP de solubilité différente dans des sols agricoles et artificiels. L'exposition des vers de terre dans des sols amendés avec jusqu'à 10,000 mg par kg de sol de nano-TiO2, un nanomatériel pratiquement insoluble, n'a causé aucun effet sur leur survie ou leur reproduction. Les vers de terre n'ont évité les sols modifiés de nano-TiO2, qu'à des concentrations de nanoparticules beaucoup plus élevées que celles attendues dans les sols agricoles. Les mécanismes impliqués dans la réponse d'évitement et les transformations de nanoTiO2 dans les sols n'ont pu être étudiés plus à fond par manque de techniques développées pour suivre les nanoparticules dans les médias complexes. Dans les recherches subséquentes, un nanomatériel de très faible solubilité, le nano-CuO, qui relâche des ions Cu2+ au fur et à mesure qu'il se dissout, a été choisi comme matériel d'intérêt. Afin d'identifier les effets spécifiques des nanoparticules sur des organismes, les effets du Cu2+ doivent être déterminés. Cependant, peu est connu sur l'activité du Cu2+ dans les sols traités avec des nano-CuO. Les recherches ont démontré que l'activité de Cu2+ a augmenté durant une période de 56 jours pour les sols amendés de nanoparticules de CuO mais cette augmentation ne s'est pas produite, à des concentrations égales, pour des sols enrichis de CuO de diamètre micrométrique ou même de sels de Cu(NO3)2 ; ces deux derniers traitements sont souvent utilisés comme tests contrôles lors d'études de nanotoxicité. Ces résultats ont des implications pour la conception des expériences pour évaluer les effets sur la dissolution des particules. Une étude ultérieure sur la croissance d'orge a démontré qu'il n'y avait aucune différence significative dans la croissance des plantes ou des concentrations de Cu dans les feuilles entre les sols modifiés avec du nano-CuO, CuO de taille micrométrique ou le Cu(NO3)2 une fois que les données furent normalisées en activité de Cu2+. Ces résultats ont démontré que la dissolution d'ions de métaux peut jouer un rôle important sur la toxicité des nanoparticules. Ils soulignent aussi l'importance de mesurer directement la concentration de produits de la dissolution de nanoparticules. Il n'y avait aucune évidence de toxicité spécifique aux nanoparticules sous les conditions étudiées pour les vers de terre soumis au nano-TiO2 ou pour l'orge soumis au nano-CuO. Cette étude a révélé certaines lacunes de compréhension dans le comportement du nanomatériel ajouté aux sols, des difficultés de tenir compte des changements temporels des nanoparticules et des sols ainsi que le manque de techniques disponibles pour suivre les nanoparticules dans les médias complexes.

APA, Harvard, Vancouver, ISO, and other styles

44

McKenzie, Katy J. "Electrochemical characterisation of metal oxide nanoparticles, nanofilms and membranes." Thesis, Loughborough University, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.417015.

Full text

APA, Harvard, Vancouver, ISO, and other styles

45

Davies, Karen E. "Biofortification of potato (Solanum tuberosum) using metal oxide nanoparticles." Thesis, Nottingham Trent University, 2018. http://irep.ntu.ac.uk/id/eprint/35494/.

Full text

Abstract:

The project aimed to increase the phytoavaiablilty of calcium (Ca), iron (Fe) and zinc (Zn) in order to fortify tubers for human consumption to aid the reduced global micronutrient malnutrition (MNM). Simultaneously improve quality of tubers (dry mass), reduction of disease occurrence (soft rot), and uniformity of tuber size. There are three strategies commonly adopted to improve plant fortification: enhanced fertilisers, breeding and nutritional genetic modification. While genetic modification has produced some interesting results, the commercialisation is hindered by public perception and legislation, therefore selective breeding programmes are now being developed to circumvent these issues and help address the global issue of micronutrient malnutrition. This programme of work adopts a more holistic approach, whereby a plant food additive has been developed that can be fed to all varieties of crop without the need to develop new strains through breeding or genetic modification. The work here in produced a number of key findings: • Increase in mineral content of tubers from skin to pith in all applications • Increased foliar growth rate and tubers >30mmm • Iron increased the consistency of tuber size • Retention on minerals in growth media, decreasing leaching and increasing phytoavailability. Also beneficial to decreasing the minerals realised in the environment. Using patented technology, the reactor allows accurate and consistent size production of nanoparticles metal oxide nanoparticles with a production rate of 1 kg per hour whereas previous this rate was approximately 5 grams a day. The bulk production allows nanoparticles to be applied in numerous ways that were previously unfeasible. Sustainable application of iron fortification that retains in the soil strata for a longer period of time than conventional applications Coating of amino acid to the nanoparticle increases the efficiency of nitrogen assimilation, in turn increasing the metabolism of the plant and accumulation of other minerals present in the soil or fertiliser. Costing less than current Fe-chelated with less requirement for application. Significant increases in the mineral content of the tubers means a more nutritional food for human consumption. Increases in weight, yield and faster maturity can mean a solution to sustaining agriculture for a fast growing population. The fortification method can be added to current fertiliser applications, requiring no drastic changes to current methods. The implications of the project are summarised in the below figure.

APA, Harvard, Vancouver, ISO, and other styles

46

Stoimenov, Peter Kirchev. "Synthesis, biocidal, and antitoxin properties of metal oxide nanoparticles /." Search for this dissertation online, 2003. http://wwwlib.umi.com/cr/ksu/main.

Full text

APA, Harvard, Vancouver, ISO, and other styles

47

Komulainen, M. (Miika). "Microstructure characterization of pulsed laser deposited metal oxide nanoparticles." Master's thesis, University of Oulu, 2016. http://jultika.oulu.fi/Record/nbnfioulu-201602111172.

Full text

Abstract:

Abstract. In this thesis, the effects of pulsed laser deposition processing parameters on microstructure of tungsten trioxide thin films was studied. Samples were deposited at room temperature under three different background oxygen pressure levels using three different laser beam fluence. Some samples were post-annealed at temperatures between 400 and 600 °C, and the rest were left as deposited. Micro- and crystal structure of the samples were examined with X-ray diffraction, Raman spectroscope, atomic force microscope, and field emission scanning electron microscope. Results showed that the films were porous, constructed of nanoparticles and had a rough surface. In crystal structure studies, amorphous phase as well as crystalline monoclinic γ- ja ε-phases were found. Value of background pressure and laser beam fluence were found to have significant effect on crystal structure, morphology, porosity, and thickness of the films. Effect of post-annealing temperature was non-linear and dependent on the as-deposited structure of the films. Before the post-annealing, the films were mostly amorphous and during the heating some of them remained amorphous, some crystallized into γ-phase, and some formed different mixtures of γ- and ε-phases. Grain sizes of the samples were studied with different methods, which gave somewhat different results, but it could be concluded that fluence of the laser was largely insignificant, and pressure and post-annealing temperature had more dominant effects.Pulssilaserkasvatettujen metallioksidinanopartikkeleiden mikrorakenteen karakterisointi. Tiivistelmä. Tässä työssä tutkittiin pulssilaserkasvatuksen parametrien vaikutusta volframitrioksidistaohutkalvojen mikrorakenteeseen. Näytteet kasvatettiin huonelämpötilassa kolmessa eri happipaineessa ja kolmella eri laserin intensiteetillä. Osa näytteistä jälkihehkutettiin 400–600 °C asteen lämpötilassa. Näytteiden mikro- ja kiderakennetta tutkittiin röntgendiffraktiolla, Raman spektroskopialla sekä atomivoima- ja elektronimikroskopian menetelmillä. Tuloksista kävi ilmi kalvojen huokoinen, nanopartikkeleista koostuva rakenne, pinnan karheus sekä eri faasien määräsuhteet. Amorfisen faasin lisäksi näytteistä löytyi kiteiset monokliiniset γ- ja ε-faasit. Taustapaineen ja laserin intensiteetin muutosten havaittiin vaikuttavan voimakkaasti kalvojen huokoisuuteen, pinnan rakenteeseen ja kalvon paksuuteen. Paineen ja intensiteetin vaikutukset olivat vastakkaisia, mutta aina samanlaisia. Jälkihehkutuksen vaikutus oli epälineaarinen sekä riippuvainen hehkutuslämpötilasta, mutta myös hehkuttamattomasta kalvon rakenteesta. Ennen jälkihehkutusta kalvot olivat pääsääntöisesti amorfista faasia, mutta hehkutettaessa osa jäi pääosin amorfiseksi ja loput kiteytyivät melko puhtaaksi monokliiniseksi γ-faasiksi tai erilaiseksi yhdistelmäksi ε- ja γ-faaseja. Jälkihehkutettujen kalvojen raekokoja laskettiin röntgendiffraktion mittaustuloksista eri menetelmillä, joilla saatiin hieman eriäviä tuloksia, mutta kaikista kävi ilmi, että laserin intensiteetillä ei ollut merkittävää vaikutusta keskimääräiseen raekokoon toisin kuin lämpötilalla ja taustapaineella.

APA, Harvard, Vancouver, ISO, and other styles

48

Mazza, T. "Synchrotron light characterization of free metal and oxide nanoparticles." Doctoral thesis, Università degli Studi di Milano, 2007. http://hdl.handle.net/2434/62645.

Full text

Abstract:

This work presents a pioneering experimental approach to the study of the interaction of free transition metal nano-sized systems with synchrotron radiation. The results of experiments performed on titanium and titanium oxide nanoparticles (clusters) are presented. The choice for these systems was mainly motivated by their strategic character from the point of view of nanostructured materials assembling, as Ti-based nanostructured materials are widely used in several application fields. The details of the developed experimental set-up and conceptual tools are described. The designed experimental set-up enables independent probing of morphology, reactivity and decay dynamics of excited states of the free nanoparticles, and this results to be mandatory for the emerging complexity of the system under study. Characterization of the nanoparticles is presented in the central part of the work. The chemical reactivity to molecular species of free Ti and TiOx nanoparticles is discussed. The reported morphology, structure and decay dynamics of nanoparticles demonstrate the need for a new picture for their description, alternative to the compact spherical shape model usually adopted for cluster spectroscopy experimental results, and nearer to concepts which are more familiar to the aerosol community. The presented results open interesting perspectives in the view of filling the gap between applications of nanostructured materials and their fundamental understanding.

APA, Harvard, Vancouver, ISO, and other styles

49

Daschner, de Tercero Maren [Verfasser]. "Near-critical and supercritical hydrothermal flow synthesis of metal oxide nanoparticles and hybrid metal oxide nanoparticles presenting clickable anchors / Maren Daschner de Tercero." Karlsruhe : KIT Scientific Publishing, 2014. http://www.ksp.kit.edu.

Full text

APA, Harvard, Vancouver, ISO, and other styles

50

Pérez, Mirabet Leonardo. "Synthesis, characterization and functionalization of metal and metal oxide nanoparticles. TEM Microscopy study." Doctoral thesis, Universitat Autònoma de Barcelona, 2013. http://hdl.handle.net/10803/129498.

Full text

Abstract:

Aquesta tesis doctoral està centrada en desenvolupar noves rutes sintètiques per tal d’obtenir i funcionalitzar els següents tipus de nanoestructures: - Nanopartícules d’or i plata dispersables en aigua, funcionalitzades amb àcid 3-mercaptopropiònic i coordinades amb carbonils de reni. - Magnetita i ferrites del tipus MFe2O4 (M= Co, Mn, Cu, Zn) recobertes amb oleilamina, la qual les fa dispersables en medis orgànics tals com hexà, toluè i diclorometà. - Nanovaretes de goethita (i de maghemita) recobertes amb etilendiamina, sintetiztades en un reactor d’autoclau. - Nanoestructures “core-shell” del tipus Fe3O4@Au, sintetitzades mitjançant diferents mètodes. Apart de sintetitzar aquests tipus de nanopartícules, aquesta tesis també està centrada en dur a terme una caracterització completa de les nanopartícules obtingudes. Per a aquest propòsit, tècniques analítiques tant microscòpiques com no microscòpiques han estat utilitzades. El procés de caracterització, especialment la part basada en fer servir Microscopis de Transmissió d’electrons (MET) ha tingut lloc no sols a la Universitat Autònoma de Barcelona (UAB) sinó també al “Center for Electron Nanoscopy” (CEN) durant una estada de quatre mesos a Dinamarca.
This PhD thesis is focused on developing new synthetic routes to obtain and functionalize the following kinds of nanostructures: - Water-dispersible gold and silver nanoparticles functionalized with 3-mercaptopropionic acid and coordinated to rhenium carbonyl species. - Magnetite and MFe2O4 (M= Co, Mn, Cu, Zn) ferrite nanoparticles capped with oleylamine, which makes them dispersible in organic solvents such as hexane, toluene and dichlorometane. - Water-dispersible goethite (and maghemite) nanorods capped with ethylenediamine, synthesized in an autoclave reactor. - Water-dispersible Fe3O4@Au core-shell nanostructures, synthesized via some different methods. Apart from synthesizing those kinds of nanoparticles, this thesis is also focused on carrying out a complete characterization of the obtained structures. To this purpose, both microscopic and no microscopic characterization techniques have been used. The characterization process, specially the part based on using Transmission Electron Microscopes (TEM), has taken place not only at the “Universitat Autònoma de Barcelona” (UAB) but also at the “Center for Electron Nanoscopy” (CEN) during a four months stay in Denmark.

APA, Harvard, Vancouver, ISO, and other styles

Dissertations / Theses on the topic 'Metal Oxides Nanoparticles'

Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles