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Lennox, Martin. "Synthesis of zinc / zinc oxide nanoparticle-carbon nanotube composites." Thesis, McGill University, 2014. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=121192.
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This thesis presents a novel process for the synthesis of zinc/zinc oxide nanoparticle-carbon nanotube composites. The process combines aerosol flow condensation for the synthesis of nanoparticles with a radio-frequency glow discharge in order to facilitate the deposition of these nanoparticles on nanostructured surfaces consisting of carbon nanotubes grown directly on stainless steel substrates. The design, construction and optimization of the process is described. A maximum observed nanoparticle deposition rate of 500 nm/min was observed when layers of nanoparticles were deposited on silicon wafers. Significant variation in the nanoparticle deposition rate was also observed; 95% confidence intervals on the prediction of nanoparticle layer thicknesses were approximately ±225nm and ±550nm for the evaporative source temperature range of 575 to 625 °C and measured average evaporation rate range of 0.009 to 0.048 g/min, respectively. A core/shell structure of zinc/zinc oxide nanoparticles is inferred from electron diffraction, X-ray diffraction, and X-ray photoelectron spectroscopy data. The utility of the synthesized nanocomposites as cathode materials is evaluated in a model direct-current glow discharge system. No significant reduction in the voltages required to sustain the glow discharge were observed when the synthesized nanocomposites were tested, as compared to cathodes of nanostructured carbon nanotube surfaces or bare stainless steel cathodes.Cette thèse présente un nouveau procédé de synthèse de nanotubes de carbone décorés de nanoparticules de zinc et oxyde de zinc. Le procédé combine la condensation d'un aérosol pour la synthèse de nanoparticules avec le traitement des particules en vol dans une décharge luminescente par radiofréquence. Cette méthode facilite le dépôt de nanoparticules sur ces surfaces nanostructurées telles que des nanotubes de carbone formés directement sur des substrats en acier inoxydable dans le cas présent. La conception, la construction et l'optimisation des processus sont décrits. Une vitesse de dépôt maximale de 500 nm/min a été observée lorsque les couches de nanoparticules ont été déposées sur des plaquettes de silicium. On a également observé une variation significative dans le taux de dépôt de nanoparticules; les intervalles de confiance à 95% pour le prédictions de l'épaisseur de la couche de nanoparticules étaient approximativement ±225 nm et ±550 nm pour la plage de température de la source d'évaporation de 575 à 625 °C tandis que le taux d'évaporation moyen mesuré variait de 0,009 à 0,048 g/min, respectivement. À partir des données de diffraction des électrons, de diffraction des rayons X ainsi que de spectroscopie photoélectronique aux rayons X, il a été possible de déduire que les nanoparticules ont une structure coeur-écorce composée de zinc et d'oxyde de zinc. L'utilité des nanocomposites synthétisés comme matériaux pour une cathode est évaluée dans un système de décharge luminescente en courant continu. Aucune réduction significative des tensions nécessaires au maintien de la décharge luminescente a été observée lorsque les nanocomposites synthétisés ont été testés, par rapport aux cathodes formées de surfaces nanostructurées de nanotube de carbone ou aux cathodes en acier inoxydable non-traité.
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McQuillan, Jonathan. "Bacterial-nanoparticle interactions." Thesis, University of Exeter, 2010. http://hdl.handle.net/10036/3101.
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Bionanotechnology is an intersection between biology and nanotechnology, a field in which novel applications for very small materials are being realised at an alarming rate. Nanoparticles have 3 dimensions that can be measured in nanometers, their small size conferring upon them different properties from individual atoms or the bulk material. The interactions between these unique materials and microorganisms are often toxic, thus have been exploited for antimicrobial applications. However, there is a considerable paucity of data for the underlying molecular mechanisms. This study has been carried out to investigate the interactions that occur between nanoparticles and bacteria with the objective of identifying these toxicological mechanisms and novel nanoparticle effects, using the model Gram negative organism Escherichia coli K12. This study has identified metal nanoparticles that are a superior vehicle for the delivery of toxic metal ions to E. coli. The nanoparticles associate with the bacterial surface, but do not cross the cell wall. They then dissolve, releasing a concentration of metal ions that accumulate at the bacterial-nanoparticle interface, enhancing the antibacterial efficacy compared to the concentration of metal ions in the bulk solution phase. Measurement of the whole transcriptome response to silver nanoparticles in comparison to the silver ion indicates that the different modes of ion delivery may induce a differential stress response. Moreover, this data identifies molecular mechanisms that are involved in the toxicity of this metal that is now becoming increasingly prevalent in society. The dissolution based toxic effects of zinc oxide nanoparticles are augmented by an interaction with ultra-violet light, offering an alternative mode for nanoparticle toxicity.
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Walker, Nicholas David Leyland. "The role of the nano-environmental interface in ZnO and CeO2 nanoparticle ecotoxicology." Thesis, University of Exeter, 2012. http://hdl.handle.net/10036/3734.
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An increase in nanotechnology has seen an associated rise in nanoparticles released into the environment. Their potential toxicity and exposure to humans and the environment, the field of nanoecotoxicology, is not yet well understood. The interactions at the nanoparticle surface will play a fundamental role in the nanoparticle behaviour once released into the environment. This study aims to characterise the particle surface interaction, determining key parameters influential in the nanoparticle fate. Evanescent Wave Cavity Ring Down Spectroscopy techniques have been applied to study molecular interactions at the silica-water charged interface. The adsorption of the electronic spectrum of Crystal Violet has demonstrated the formation of a monolayer with different binding site orientation at the interface. The binding affinity for the chromophore was calculated as 29.15 ± 0.02 kJmol-1 at pH 9 and this was compared with other interface structures involving both inorganic and organic components. The study of the model interface was extended to the properties of CeO2 nanoparticles, where the surface charge density was determined to be 1.6 ± 0.3 e- nm-2.The nanoparticle surface charge controls the suspension stability which was measured for CeO2 nanoparticles giving a stability half-life of 330 ± 60 hours in pure water, and 3.6 ± 0.6 hours in ISOFish water. Studies were extended to the toxicity of ZnO nanoparticles. An assay was developed to quantify the photo-electron production for nanoparticles exposed to UV light both in deionised water and soil suspensions with a photo-radical production yield of 19 ± 2 % and an electron production of 709 e-s-1np-1 for a 100 mgL-1 suspension. The species-specific photo-radical assay was subsequently used to determine the rate of ZnO nanoparticle dissolution in water and soil suspensions. Comparable dissolution rates in complex cell growth media were also measured, detecting total zinc by Inductively Coupled Plasma Atomic Emission Spectroscopy, with comparable dissolution rates derived.
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Khoza, Phindile Brenda. "Phthalocyanine-nanoparticle conjugates for photodynamic therapy of cancer and phototransformation of organic pollutants." Thesis, Rhodes University, 2015. http://hdl.handle.net/10962/d1017918.
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The synthesis and extensive spectroscopical characterization of novel phthalocyanines are reported. The new compounds were characterized by elemental analysis, FT-IR, ¹HNMR, mass spectrometry and UV–Vis spectroscopy. The new phthalocyanines showed remarkable photophysicochemical behaviour. The novel phthalocyanines were then conjugated to nanoparticles, silver and ZnO. The coupling of the novel Pcs to nanoparticles was through covalent bonding and ligand exchange. These conjugates were supported onto electrospun polystyrene fibers and chitosan microbeads for use as photocatalysts. The efficiency of the immobilized Pcs and Pc-nanoparticles was assessed by the phototrasfromation of organic pollutants, methyl orange and Rhodamine 6G as model dyes. Upon conjugating phthalocyanines to nanoparticles, there was a great increase in the rate of photodegradation of the model dyes. The photodynamic activity of the novel phthalocyanines upon conjugating to nanoparticles and selected targeting agents is also reported. The targeting agents employed in this study are folic acid and polylysine. Conjugating the phthalocyanines to folic acid or polylysine improved the solubility of the phthalocyanines in aqueous media. The potency of the conjugates was investigated on breast (MCF-7), prostate and melanoma cancer cell lines. The phthalocyanines showed no toxicity in the absence of light. However, upon illumination, a concentration dependent cellular decrease was observed.
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Gunti, Srikanth. "Enhanced Visible Light Photocatalytic Remediation of Organics in Water Using Zinc Oxide and Titanium Oxide Nanostructures." Scholar Commons, 2017. http://scholarcommons.usf.edu/etd/6852.
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The techniques mostly used to decontaminate air as well as water pollutants have drawbacks in terms of higher costs, require secondary treatment, and some methods are very slow. So, emphasis has been given to water though the use of photocatalysts, which break organic pollutants to water and carbon dioxide and leave no trace of by-products at the end. Photocatalytic remediation aligns with the waste and wastewater industries’ zero waste schemes with lower cost, eco-friendly and sustainable treatment technology. The commonly used photocatalysts such as titanium oxide (TiO2), zinc oxide (ZnO), tungsten oxide (WO3) have band gap of nearly 3.2 eV. The lower energy band-gap of a semiconductor makes it a better photocatalyst. The major drawbacks of photocatalysts are its inefficiency to work under visible light and high photocorrosion which limits its uses. These limitations can be mitigated through dopants and the formation of varying morphologies like nanowires, nanoparticles, nanotubes etc. Several organic pollutants are insoluble in water, which inhibits the pollutant (insoluble) to come in contact with photocatalytic material thus hindering remediation characteristic of a photocatalyst. Binder material used to immobilize the photocatalytic material tends to decompose due to oxidative and reduction reactions around the photocatalyst which causes the loss of photocatalytic material.
This investigation displays the advantage of organic remediation in visible radiation using graphene (G) doped TiO2 nanoparticles and nanowires. The nanostructured G-TiO2 nanoparticles and G-TiO2 nanowires were synthesized using sol-gel and hydrothermal methods. The nanostructured materials were characterized using scanning electron microscopy (SEM), Transmission electron microscopy (TEM), X-ray diffraction (XRD), UV-visible spectroscopy (UV-vis), Fourier transform infrared spectroscopy (FTIR) and particle analyser procedures. The remediation of organic compounds (methyl orange) in water was achieved under visible radiation using graphene doped nanostructured photocatalytic materials. The sol-gel synthesized G-TiO2 nanoparticles has shown complete remediation of methyl orange (MO) in less than four hours, thus displaying enhanced photocatalytic activity achieved through graphene doping on TiO2 nanostructures
The dopant and structure introduced in zinc oxide (ZnO) nanomaterials bring foundation for enhanced photocatalytic activity due to lowering of the band gap, and decreasing of photocorrosion through delaying of electron-hole recombination. The challenge to synthesize both nanowire and nanoparticle structures of ZnO doped with graphene (G) are carried out by simple and cost effective hydrothermal as well as super saturation precipitation techniques, respectively. Various nanostructures of ZnO have been synthesized using precipitation and hydrothermal methods are ZnO nanoparticles, G doped ZnO nanoparticles, ZnO nanowires, G doped ZnO nanowires, TiO2 seeded ZnO nanowires and G doped TiO2 seeded ZnO nanowires The synthesized ZnO based nanostructures were characterized using SEM, TEM, XRD, UV-vis, FTIR and particle analyser methods respectively. The standard organic pollutant methyl orange (MO) dye was employed in the water to understand the effective remediation using ZnO nanostructured materials under visible light radiation. The G-ZnO NW structure has shown effective remediation of MO in water in three hours compared to other synthesized nanostructured ZnO materials.
The petroleum compounds were photocatalytically remediated from water using G- TiO2 nanoparticles material in visible light radiation. The G-TiO2 nanoparticle was synthesized using sol-gel technique and used on various petroleum-based chemicals (toluene, naphthalene and diesel) were remediated, and samples were analysed using optical and gas chromatography (GC) techniques. The importance of pollutant to come in contact with photocatalyst have been demonstrated by employing surfactant along with G-TiO2 nanoparticles to remediate naphthalene.
Earlier studies in this investigation have shown that graphene (G) doping in both titanium oxide (TiO2) and zinc oxide (ZnO), has brought about a reduction in photocorrosion, and an increase in the photocatalytic efficiency for remediation of organics under visible light (λ > 400nm). However, the graphene doped photocatalysts have proven to be hard to coat on a surface, due to the strong hydrophobic nature of graphene. So, attempts have been made to use polyaniline (PANI), a conducting polymer, as a binder material by insitu polymerization of aniline over G-TiO2 nanoparticles (G-TiO2 NP) and G-ZnO nanowires (G-ZnO NW) & characterized using SEM, XRD, UV-vis and FTIR techniques. The photocatalytic, as well as photoelectrochemical catalytic performance of PANI:G-TiO2 NP and PANI:G-ZnO NW, were investigated. The standard MO in water was used for both PANI:G-TiO2 NP and PANI:G-ZnO NW electrodes on conducting substrates. 1:1 PANI:G-TiO2 NP shows an increase of 31% in the remediation of MO in water at potential of +1000 mV, and with the ease in coating PANI:G-TiO2 NP and PANI:G-ZnO NW on various substrates, on top of the visible light remediation allows for the use of these materials and process to be used for practical applications of remediation of organics from water.
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Louka, Chrysovalanto. "Controlling the toxicity of zinc oxide nanowires in vitro skin models." Thesis, Université Grenoble Alpes, 2020. https://thares.univ-grenoble-alpes.fr/2020GRALU004.pdf.
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Les nanofils d'oxyde de zinc (ZnONW) attirent beaucoup d'attention scientifique en raison de leurs propriétés optoélectriques, piézoélectriques et semi-conductrices, qui en font un bon candidat pour les capteurs et l'électronique intégrées dans les textiles. Ces applications augmentent les risques d'exposition cutanée, de qui rend l’étude de leur toxicité cruciale, d'autant plus que les études récentes démontrent une toxicité liée aux ions de zinc due à la dissolution. Malheureusement, la compréhension de l'impact des ZnONWs sur la peau est limitée. Par conséquent, l'objectif de ce projet est d'acquérir une compréhension approfondie du danger potentiel des ZnONWs sur la peau (humaine) in vitro et de la façon dont leurs propriétés physicochimiques sont liées à cela.Ici, une caractérisation physico-chimique étendue des ZnONWs a été effectuée dans des milieux de cultures de cellules (GlutaMAX) avec et sans sérum, et dans des suspensions milli Q eau (mQ H2O). Les résultats ont montré que la dissolution de la suspension stock, où les deux nanomatériaux ZnO (ZnONM) sont dans mQ H2O, a atteint une concentration en ions zinc à l'équilibre de 15 µg / mL immédiatement, tandis que les études de dimensions ont montré une forte agrégation dans GlutaMAX sans sérum et une agrégation réduite dans les milieux GlutaMAX avec du sérum . Il a été démontré que les conditions de stockage de l'incubateur à 5% de CO2 et à 37 ° C ont un impact sur la dissolution en abaissant le pH de la suspension aqueuse milli Q et en formant éventuellement des complexes de carbonate de zinc dans les milieux.L'examen de la cytotoxicité des ZnONW dans la monoculture cutanée et la comparaison avec les nanoparticules de ZnO (ZnONP) et le chlorure de zinc (ZnCl2) a montré que les ZnONM induisaient une cytotoxicité et une baisse de viabilité cellulaire significatives à partir de 40,2 µg / mL d'équivalent zinc, avec moins de 40% de cellules viables. La comparaison avec le ZnCl2 a montré une association claire entre la dissolution et la cytotoxicité cellulaire.Pour évaluer davantage l'impact réel des ZnONW dans la peau, un système de co-culture dans l'interface air-liquide (ALI) composé d'épiderme et de cellules cutanées du derme a été développé après uneoptimisation en monoculture de chaque type de cellule. Le système de modèle de peau 3D a été exposé aux ZnONPs, ZnONWs et ZnCl2. Pour empêcher la dissolution des ZnONW, une couche de dioxyde de titane (TiO2) de 5,75 ± SD 1,06 nm a été déposée par dépôt de couche atomique (ALD) sur les ZnONWs. Les ZnONWs recouverts de TiO2 ont également été testés pour leur toxicité sur le système de co-culture.Les résultats des expositions ont montré une mort cellulaire significative avec seulement 20% de cellules vivantes, après traitement aux ZnONMs et au ZnCl2 à 80,4 µg tandis que le traitement aux ZnONW revêtus de TiO2 maintenait au moins 75% de viabilité cellulaire même à 80,4 µg. Cependant, un examen plus approfondi des médiateurs (pro-) inflammatoires après le traitement a montré que les ZnONW revêtus de TiO2 augmentaient les niveaux d'interleukine (IL) 8 et 6 (pro-) inflammatoires par rapport aux ZnONW sans couche de TiO2. Cela pourrait soulever d'autres problèmes de toxicitéZinc oxide nanowires (ZnONWs) are attracting a lot of scientific attention due to their optoelectrical, piezoelectrical and semiconducting properties, which make them a good candidate for sensors and wearable electronics. These applications increase the chance of skin exposure, hence the investigation of their safety is crucial, especially since studies on ZnONWs show a zinc ion related toxicity due to their dissolution. Unfortunately, understanding of ZnONWs impact on skin is limited. Therefore, it is the objective of this project to gain an insightful understanding of the potential hazard of ZnONWs upon (human) skin in vitro and how their physicochemical properties are related to this.Herein, an extensive ZnONWs physicochemical characterisation was performed in media with and without serum, and in milli Q water (mQ H2O) suspensions. Results showed the stock dissolution, where both ZnO nanomaterials (ZnONMs) are in mQ H2O, reached a zinc ion concentration at equilibrium of 15 µg/mL immediately, while size studies showed high aggregation in GlutaMAX without serum and reduced aggregation in GlutaMAX media with serum. Incubator storing conditions of 5% CO2 and 37oC were shown to have an impact on the dissolution by lowering the pH of the milli Q water suspension and possibly forming zinc carbonate complexes in media.Examining the cytotoxicity of ZnONWs in skin monoculture and comparing it to ZnO nanoparticles (ZnONPs) and zinc chloride (ZnCl2), showed that ZnONMs induced a significant cytotoxicity and cell death from 40.2 µg/mL zinc equivalent, with less than 40% viable cells. Comparison with the ZnCl2 showed a clear association between dissolution and cell cytotoxicity.To assess further the actual impact of ZnONWs in the skin, a co-culture system in Air-Liquid-Interface (ALI) consisting of epidermis and dermis skin cells was developed after monoculture optimisation of each cell type. The 3D skin model system was exposed to ZnONPs, ZnONWs and ZnCl2. To prevent the dissolution of ZnONWs, a 5.75±SD 1.06 nm Titanium dioxide (TiO2) shell was deposited via Atomic layer deposition (ALD) on the ZnONWs. The TiO2 coated ZnONWs were also tested for their toxicity on the co-culture system.Results of the exposures showed a significant cell death with only 20% alive cells, after ZnONMs and ZnCl2 treatment at 80.4 µg whilst the TiO2 coated ZnONWs treatment maintained at least 75% cell viability even at 80.4 µg. However, further examination of (pro-) inflammatory mediators after treatment showed that TiO2 coated ZnONWs increased levels of (pro-)inflammatory Interleukin (IL) 8 and 6 compared to bare ZnONWs. This could raise further safety issues
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Wong, Ka-kan, and 黃嘉勤. "Investigation on the effect of ZnO nanoparticle properties on dye sensitized solar cell performance." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2012. http://hub.hku.hk/bib/B49618246.
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Zinc oxide (ZnO) is a wide band-gap semiconductor that is of interest for application in dye sensitized solar cells (DSSCs) because of similarity of its properties to TiO2. Unlike TiO2, ZnO can readily be grown in a wide variety of morphologies, using inexpensive, simple, and low temperature methods. Recent research on ZnO-based DSSCs focuses on modifying the ZnO layer morphology in order to maximize surface area, and enhance the electron collection by providing fast electron transport. It is expected that the improvement in cell performance by morphology modification is due to higher dye loading, increased electron lifetime and fast electron transport. However, ZnO properties may be affected by various synthesis methods. It is difficult to make a conclusion whether the change of performance are attributed to change of morphology or a change in the defect types and/ or defect concentrations.
In this study, the influence of ZnO nanoparticle properties on cell performance has been investigated. Commercial ZnO nanoparticles with different sizes and optical properties were utilized. It was found that there is a complex relationship between native defects, dye loading, charge transport and photovoltaic performance. In particular, the presence of non-radiative defects was found to be detrimental to photovoltaic performance. In addition, with the similar defect emission intensities, sample exhibiting orange-red defect emission showed better performance than the samples emitting green defect emission. Nanoparticle properties and their relationship between dye adsorption, electron injection, electron lifetime and electron transport, and photovoltaic performance will be discussed.published_or_final_version
Physics
Master
Master of Philosophy
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Ruankham, Pipat. "Studies on Morphological Effects and Surface Modification of Nanostructured Zinc Oxide for Hybrid Organic/Inorganic Photovoltaics." Kyoto University, 2014. http://hdl.handle.net/2433/188820.
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CRAPANZANO, ROBERTA. "Insight into ZnO luminescence to engineer nanoparticles for X-Ray based cancer treatment." Doctoral thesis, Università degli Studi di Milano-Bicocca, 2022. http://hdl.handle.net/10281/366193.
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Nanoparticles disclose unique properties that enable their applications in different fields, such as energy, catalysis, opto-electronics, and medicine. At the nanosize, the surface-to-volume ratio is increased, leading to the formation of defects that influence the resultant features, e.g. the catalytic and optical behaviours of the systems. Moreover, the high surface area and reactivity of nanoparticles allow their functionalization with several ligands, enhancing their versatility, especially in the biomedical field. Indeed, the accuracy and efficiency of several diagnoses and treatments may improve by implementing traditional strategies with targeted nano-agents. Among the nanomedicine researches, heavy nanoparticles are promising for the innovation of radiotherapy and for the development of novel oncological procedure, such as X-Ray induced photodynamic therapy, that exploits the combination of nanoscintillators and photosensitizers.
In this context, ZnO is of particular interest. Indeed, ZnO is a wide band gap semiconductor that displays emissions in the visible region of the spectrum, surface reactivity, and biocompatibility. Moreover, upon X-Ray exposure, ZnO can generate cytotoxic species both directly, due to its catalytic activity, and indirectly, by activating the close photosensitizers, due to its ability to down-convert X-Ray photons into visible ones.
This thesis focuses on the study of ZnO NPs for the innovation of X-Ray based cancer therapies. In detail, a fundamental investigation of the optical and catalytic properties of several ZnO samples is performed and used as background to design and develop ZnO based multicomponent nanosystems.
Namely, the optical features of ZnO samples with different sizes (nanometric, micrometric, and bulk) and growth conditions are investigated by photoluminescence and radioluminescence techniques aiming at deepening the comprehension of the impact of morphology on the material defectiveness. A Gaussian reconstruction of all the spectra identifies in ZnO luminescence as many as five emission bands (one related to excitons and four to defects), whose spectral shapes and time decays vary with the dimensionality and the synthesis procedure. Moreover, the test of the ability of various nanosized ZnO sample to promote the production of different cytotoxic species unveils that their radio-catalytic activity is affected by the type and concentration of occurring point defects. Thus, by controlling the synthesis parameters and the morphology (size, shape, interfaces) of ZnO nanostructures, its defectiveness can be engineered to tune its optical and catalytic properties.
Then, to realize a nano-agent for X-Ray induced photodynamic therapy, ZnO nanoparticles supported onto nanosized silica substrates with different porosity, are functionalized with various concentrations of porphyrins. The study of their optical properties reveals that, under light excitation, the dye luminescence is activated only by a rather poor re-absorption mechanism. Differently, upon X-Ray exposure, the porphyrin emission sensitization is enhanced, especially at low concentrations and high energy of the ionizing beams, by the locally augmented energy deposition favoured by ZnO, as also confirmed by Monte Carlo simulations. These findings highlight the synergic role of X-Ray and functionalization, paving the way for further studies on the impact of nano-agent design on its performances.
This PhD project has been performed at the Department of Materials Science of the University of Milano-Bicocca, in collaboration with the NanoMat@Lab for the samples preparation and with Dr Anne-Laure Bulin of the Synchrotron Radiation for Biomedicine Group at the University of Grenoble-Alpes, INSERM, for the computational analysis.Le nanoparticelle possiedono proprietà uniche che permettono il loro utilizzo in diversi settori, come la catalisi, l’opto-elettronica e la medicina. A livello nanometrico, il rapporto superficie-volume è alto, portando alla formazione di difetti che influenzano le proprietà del sistema, ad esempio le risposte catalitiche e ottiche. Inoltre, le elevate aree e reattività superficiali delle nanoparticelle consentono la loro funzionalizzazione con diversi leganti, incrementando la loro versatilità, soprattutto nell’ambito medico. L'accuratezza e l’efficacia di diagnosi e terapie può migliorare implementando le strategie tradizionali con nano-agenti. Tra i campi di ricerca in nanomedicina, nanoparticelle con alto numero atomico sono promettenti per innovare la radioterapia e per sviluppare nuove procedure oncologiche, come la terapia fotodinamica indotta dai raggi X, che sfrutta nanoscintillatori combinati a fotosensibilizzatori. In questo ambito, ZnO è di grande interesse. ZnO è un semiconduttore che mostra emissioni nello spettro del visibile, reattività superficiale e biocompatibilità. Inoltre, esposto ai raggi X, ZnO può generare specie citotossiche sia direttamente, grazie alla sua attività catalitica, sia indirettamente, attivando i vicini fotosensibilizzatori, grazie alla sua abilità di convertire i fotoni X in visibili. Questa tesi concerne lo studio di NPs di ZnO per l’innovazione di terapie oncologiche attivate dai raggi X. In dettaglio, un’analisi fondamentale delle proprietà ottiche e catalitiche di diversi campioni di ZnO è condotta e usata come base per progettare nanosistemi multicomponente a base di ZnO. In particolare, le proprietà ottiche di campioni di ZnO con diverse dimensioni (nanometriche, micrometriche e massive) e condizioni di crescita sono studiate con tecniche di fotoluminescenza e radioluminescenza con l’obiettivo di approfondire la comprensione del ruolo della morfologia sulla difettualità. L’analisi numerica di tutti gli spettri identifica nella luminescenza di ZnO un massimo di cinque bande di emissione (una attribuita agli eccitoni e quattro ai difetti), le cui forme spettrali e tempi di vita variano con la dimensione e la procedura di sintesi. Inoltre, lo studio dell’abilità di diversi campioni nanometrici di ZnO di produrre specie citotossiche rivela che la sua attività radio-catalitica dipende dal tipo e dalla concentrazione dei difetti di punto. Quindi, il controllo dei parametri di sintesi e della morfologia (dimensione, forma, interfacce) potrebbe permette l’ingegnerizzazione dei difetti e quindi delle proprietà ottiche e catalitiche. Per realizzare un nano-agente per la terapia fotodinamica indotta dai raggi X, nanoparticelle di ZnO, supportate su substrati nanometrici di silice con diversa porosità, sono funzionalizzate con varie concentrazioni di porfirine. Lo studio delle loro proprietà ottiche rivela che, sotto eccitazione ottica, la luminescenza della porfirina è attivata solo da un meccanismo di riassorbimento con efficienza limitata. Invece, sotto radiazione ionizzante, l’emissione della porfirina è ben sensibilizzata, specialmente a basse concentrazioni e alte energie del fascio di raggi X, grazie al locale aumento del deposito di energia favorito dalle nanoparticelle di ZnO, come confermato dalle simulazioni. Questi risultati evidenziano il ruolo sinergico dei raggi X e della funzionalizzazione, aprendo a ulteriori studi sull’impatto della progettazione del nano-agente sulle sue prestazioni. Questo progetto è stato condotto nel Dipartimento di Scienza dei Materiali dell’università di Milano-Bicocca e in collaborazione con il NanoMat@Lab per la preparazione dei campioni e con la Dottoressa Anne-Laure Bulin dell’università di Grenoble-Alpes per l’analisi computazionale.
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Mileyeva-Biebesheimer, Olga. "An Investigation into Metal Oxide Nanoparticle Toxicity to Bacteria in Environmental Systems Using Fluorescence Based Assays." University of Toledo / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1302125170.
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Wangensteen, Ted. "Growth And Characterization Of Functional Nanoparticulate Films By A Microwave Plasma-Assisted Spray Deposition Process." Scholar Commons, 2012. http://scholarcommons.usf.edu/etd/4417.
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Nanoparticle and nanoparticulate films have been grown by a unique approach combining a microwave and nebulized droplets where the concentration and thus the resulting particle size can be controlled. The goal of such a scalable approach was to achieve it with the least number of steps, and without using expensive high purity chemicals or the precautions necessary to work with such chemicals. This approach was developed as a result of first using a laser unsuccessfully to achieve the desired films and particles. Some problems with the laser approach for growing desired films were solved by substituting the higher energy microwave for the laser. Additionally, several materials were first attempted to be grown with the laser and the microwave, and what was learned as result of failures was implemented to successfully demonstrate the technique.
The microwave system was characterized by using direct temperature measurements and models. Where possible, the temperature of deposition was determined using thermocouples. In the region of the waveguide, the elemental spectral lines were measured, and the temperature was calculated from measured spectral peaks. From the determined temperature, a diffusion calculation modeled the rate of heat transfer to the nebulized droplets. The result of the diffusion calculations explained the reason for the failure of the laser technique, and success for the microwave technique for simple chemistries.
The microwave assisted spray pyrolysis (MPAS) technique was used to grow ZnO nanoparticles of varying size. The properties of the different size particles was measured by optical spectroscopy and magnetic measurements and was correlated to the defects created.
The MPAS technique was used to grow films of Ca3Co4O9 containing varying sizes of nanoparticulates. The resistivity, Seebeck coefficient, and the power factor (PF) measured in the temperature range of 300-700 K for films grown by MPAS process with varying concentrations of calcium and cobalt chlorides are presented. Films with larger nanoparticles showed a trend toward higher PFs than those with smaller nanoparticles. Films with PFs as high as 220 μW/mK 2 were observed in films containing larger nanoparticles.
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Rhodes, Rhys William. "Controlling the morphology of nanoparticle-polymer composite films for potential use in solar cells." Thesis, University of Manchester, 2011. https://www.research.manchester.ac.uk/portal/en/theses/controlling-the-morphology-of-nanoparticlepolymer-composite-films-for-potential-use-in-solar-cells(6bc2a3cc-7c11-4615-a202-bead6360af99).html.
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This thesis presents an investigation into the factors affecting the morphology of hybrid inorganic/organic photoactive layers used in photovoltaic cells. Although optimisation of the organic (polymer) phase has received substantial attention, research into the morphology of the inorganic phase (semiconducting nanocrystals) remains limited. It is believed that there is a strong link between the morphology of the final photoactive film and the quality of the initial nanocrystal dispersion. To this end, two nanocrystal systems were investigated; zinc oxide (ZnO) and lead sulphide (PbS). ZnO nanocrystals were synthesised and found to possess reproducible characteristics. It was determined that colloid stability was initially dependent upon the presence of acetate groups bound to the surface, which in turn required a small quantity of methanol to be present in the organic dispersant. It was also discovered that while methanol evaporated readily from the surface of the nanocrystals, another molecule, 1-propylamine (1-PA), did not. Further investigations showed that while methanol only weakly physisorbed to the surface of ZnO nanocrystals, 1-PA formed strong, dative covalent bonds with Zn2+, preventing evaporation despite a low boiling point. Subsequent investigations into the effects of different ligands upon colloid stability found that amine-based groups typically possessed superior stabilising capabilities compared to alcohol-based analogues. The characteristics of nanocrystal / polymer blends were also investigated. It was determined that the nanocrystal dispersion became unstable at higher concentrations of polymer due to depletion aggregation. Films of nanocrystal / polymer blends were cast from dispersions containing either alcohol or amine-based ligands, and it was observed that dispersions stabilised with 1-PA possessed smooth morphologies on the micrometer scale. Investigations at the nanometer scale, however, revealed aggregates large enough to favour recombination.The latter half of this thesis regards the characterisation of PbS nanocrystals and investigations into triggered aggregation. It was determined that while PbS nanocrystals possessed reproducible characteristics, the stabilising molecule, oleic acid (OA) was insulating. The effects of exchanging the OA groups for a shorter ligand, butylamine (BA) were investigated.Finally, PbS nanocrystals were treated with a bidentate ligand, 1,2-ethanedithiol (EDT) to induce triggered aggregation. It was observed that the system was highly sensitive to the concentration of EDT in dispersion, forming small, relatively dispersed aggregates at low [EDT], and micrometer-sized crystalline structures at high [EDT]. The characterisation and entrapment of these nanocrystal structures within semi-conducting polymer films is also discussed.
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McCracken, Christie Joy. "Toxicity of Food-Relevant Nanoparticles in Intestinal Epithelial Models." The Ohio State University, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=osu1437688702.
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Raevskaya, A. E., Ya V. Panasiuk, O. L. Stroyuk, S. Ya Kuchmiy, V. M. Dzhagan, A. G. Milekhin, N. A. Yeryukov, et al. "Spectral and luminescent properties of ZnO–SiO2 core–shell nanoparticles with size-selected ZnO cores." Universitätsbibliothek Chemnitz, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-161737.
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Deposition of silica shells onto ZnO nanoparticles (NPs) in dimethyl sulfoxide was found to be an efficient tool for terminating the growth of ZnO NPs during thermal treatment and producing stable core–shell ZnO NPs with core sizes of 3.5–5.8 nm. The core–shell ZnO–SiO2 NPs emit two photoluminescence (PL) bands centred at [similar]370 and [similar]550 nm originating from the direct radiative electron–hole recombination and defect-mediated electron–hole recombination, respectively. An increase of the ZnO NP size from 3.5 to 5.8 nm is accompanied by a decrease of the intensity of the defect PL band and growth of its radiative life-time from 0.78 to 1.49 μs. FTIR spectroscopy reveals no size dependence of the FTIR-active spectral features of ZnO–SiO2 NPs in the ZnO core size range of 3.5–5.8 nm, while in the Raman spectra a shift of the LO frequency from 577 cm−1 for the 3.5 nm ZnO core to 573 cm−1 for the 5.8 nm core is observed, which can indicate a larger compressive stress in smaller ZnO cores induced by the SiO2 shell. Simultaneous hydrolysis of zinc(II) acetate and tetraethyl orthosilicate also results in the formation of ZnO–SiO2 NPs with the ZnO core size varying from 3.1 to 3.8 nm. However, unlike the case of the SiO2 shell deposition onto the pre-formed ZnO NPs, individual core–shell NPs are not formed but loosely aggregated constellations of ZnO–SiO2 NPs with a size of 20–30 nm are. The variation of the synthetic procedures in the latter method proposed here allows the size of both the ZnO core and SiO2 host particles to be tunedDieser Beitrag ist aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich
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Taylor, Cameron S. "Characterisation of engineered nanoparticles and their interaction with natural biological and non-biological material." Thesis, University of Oxford, 2014. http://ora.ox.ac.uk/objects/uuid:03810528-de65-4094-907c-8c0d4e0386c8.
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Form, mobility, toxicity and the eventual fate of engineered nanomaterials in environmental ecosystems are currently not well defined and are needed to improve risk assessment and legislation. The present study subjected uncoated zinc oxide (ZnO) nanoparticles (30nm and 200nm) and coated silver (Ag) nanoparticles (Paraffin: 3-8nm and citrate/PVP: 50nm) to different ionic strength media and different types of algal/bacterial extracellular-polymeric species (EPS) at long (6 months) and short (2 weeks) timescales. Changes in particle size distribution and stability were examined using a multi-method approach. Sample concentration and sample polydispersity are important factors when selecting techniques. Uncoated ZnO nanoparticles aggregated heavily in water at high concentrations (1000mg/L). However silver nanoparticles (1-10mg/L) remained stable at all ionic strengths and EPS in this study due to the steric component of their coatings. Nano-toxicological experiments involving cyanobacteria S.leopoliensis and green algae C.reinhardtii showed size-dependent toxicity from coated nanosilver particles. Smaller nanoparticles (3-8nm) showed greater dissolution over 72h and greater toxicity to both species than 50nm particles indicating silver ions are an important toxicity mechanism. Nanoparticle coatings were likely important in controlling dissolution levels. Cell viability and production of reactive oxygen species (ROS) were shown to be important mechanisms of toxicity to phycological species. Species specific effects were noted for both silver nanoparticles. EPS from S.leopoliensis were noted to remove ionic silver from suspension and different types of C.reinhardtii EPS were produced when particles underwent different levels of toxic stress indicating that EPS could both affect particle toxicity and be affected by it. This work has demonstrated that coated nanoparticles could remain stable under various ionic strengths and with exposure to algal organic matter for timescales up to 6 months. This could result in adverse effects to aquatic organisms were they to reach environmental systems and is of concern to nanomaterial risk assessors.
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Pokhrel, Lok R., and Phillip R. Scheuerman. "Ecological Risk Assessment of Zinc Oxide Nanoparticles." Digital Commons @ East Tennessee State University, 2012. https://dc.etsu.edu/etsu-works/2962.
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Pokhrel, Lok R., Brajesh Dubey, and Phillip R. Scheuerman. "Ecological Risk Assessment of Zinc Oxide Nanoparticles." Digital Commons @ East Tennessee State University, 2012. https://dc.etsu.edu/etsu-works/2951.
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Hancock, Jared M. "Formation and Analysis of Zinc Oxide Nanoparticles and Zinc Oxide Hexagonal Prisms and Optical Analysis of Cadmium Selenide Nanoparticles." BYU ScholarsArchive, 2013. https://scholarsarchive.byu.edu/etd/3867.
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In this dissertation, methods to synthesize ZnO are reported. First, zinc oxide nanoparticles were synthesized with small amounts of transition metal ions to create materials called dilute magnetic semiconductors (DMS). We employed a low temperature sol-gel method that produces ZnO nanoparticles of reproducible size and incorporates cobalt, nickel, and manganese ions into the nanoparticles. Conditions were controlled such that a range of amounts of Co, Ni, and Mn were incorporated. The incorporation was tracked by color changes in the white ZnO powder to blue for Co, green for Ni and yellow for Mn. XRD measurements showed the nanoparticles were on the order of 10 nm in diameter and had a wurtzite structure. Magnetic measurements showed a change from diamagnetic to paramagnetic behavior with increasing concentration of metal dopants. Second, formation of ZnO single crystal hexagonal prisms from a sol-gel method is presented. The method required water, zinc acetate, and ethanolamine to create a gel of zinc hydroxide and zinc hydroxide acetate, which upon heating formed single crystal hexagonal prisms. Characterization of the gel was done by XRD as well as XRD high temperature chamber (HTK) to determine the role of temperature in prism formation. SEM images showed hexagonal prisms were of uniform size (0.5 × 2 µm.) TEM and electron diffraction images showed a change from randomly oriented particles to an ordered single crystal after heating. Water and the acetate salt of zinc proved to be critical to prism formation. Lastly, we report absorption and fluorescence properties of synthesized oligothiophenes and oligothiophene-ruthenium complexes that are bound to CdSe nanoparticles. Their ability to act as sensitizers and charge transfer junctions was tested. It was found that fluorescence of CdSe nanoparticles was quenched when they were bound to the oligothiophenes, and that the fluorescence of the oligothiophenes was also quenched. The fluorescence lifetimes of the quenched species were shortened.
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Hernández, Viezcas José Angel. "Toxicity of zinc oxide and cerium oxide nanoparticles to mesquite (Prosopis juliflora-velutina)." To access this resource online via ProQuest Dissertations and Theses @ UTEP, 2009. http://0-proquest.umi.com.lib.utep.edu/login?COPT=REJTPTU0YmImSU5UPTAmVkVSPTI=&clientId=2515.
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Lopes, Sílvia Ferreira. "Effect of zinc oxide nanoparticles in Daphnia magna." Master's thesis, Universidade de Aveiro, 2012. http://hdl.handle.net/10773/10258.
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Mestrado em Biologia Aplicada - Toxicologia e EcotoxicologiaO rápido desenvolvimento da nanotecnologia com o consequente aumento na produção de nanopartículas e nanoprodutos oferece muitas oportunidades mas também muitos desafios. A nanotecnologia tem vindo a ser descrita como uma área multidisciplinar que visa desenvolver uma variedade de nanoparticulas para aplicações medicinais e industriais. As propriedades que trazem às nanoparticulas especial atenção – pequeno tamanho, elevada área de superfície e consequente elevado grau de reatividade – podem também torná-las potencialmente perigosas para a saúde humana e para o ecossistema. A avaliação dos potenciais riscos inerentes à exposição das nanoparticulas torna-se portanto uma investigação de prioridade antes que estas sejam aplicadas em produtos comerciais e libertadas para o ambiente. Os ambientes aquáticos (de água doce e marinho) são considerados como potenciais destinos das nanoparticulas libertadas para o ambiente através de fontes diretas e/ou indiretas, expondo assim os organismos aquáticos a elevados níveis de contaminação. As nanoparticulas de óxido de zinco (ZnO-NPs) são uma das nanoparticulas mais utilizadas numa vasta gama de produtos comerciais (ex: protetores solares, cosméticos e tintas) e a sua produção estima-se que irá continuar a aumentar nos próximos anos. Em consequência, o risco de contaminação aquática por parte destas nanoparticulas irá forçosamente aumentar. Estudos toxicológicos já demonstraram que as ZnO-NPs exercem efeitos tóxicos em vários organismos, como por exemplo, em crustáceos, algas e bactérias. Os efeitos tóxicos das nanoparticulas são complexos e podem estar dependentes de vários fatores, tais como, o organismo-teste, fatores abióticos (pH, salinidade, dureza da água e presença de matéria orgânica), propriedades físico-quimicas das nanoparticulas, processos de adsorção, presença de outros contaminantes, entre outros. Os objetivos principais deste trabalho consistiram em avaliar a toxicidade das ZnO-NPs com diferentes tamanhos (30 e 80-100 nm) no cladócero Daphnia magna e comparar estes efeitos com os homólogos de tamanho micrómetro (ZnO > 200 nm) e a forma iónica (ZnCl2). Os efeitos foram avaliados nos parâmetros de imobilização, inibição alimentar e reprodução. Os resultados mostraram uma relação dose-resposta entre o decréscimo dos parâmetros avaliados e a concentração das ZnONPs, ZnO de tamanho micrómetro e ZnCl2 testadas. De acordo com os resultados obtidos foi possível concluir que o ZnCl2 induziu maior toxicidade aguda para a D. magna. Contudo, para a reprodução e inibição alimentar, as nanoparticulas de ZnO mostraram ter um efeito mais tóxico. Foi observado igualmente que o tamanho das nanopartículas não influenciou a toxicidade do ZnO. Este estudo realça a importância de se estudarem os efeitos de nanoparticulas de diferentes tamanhos uma vez que este é um parâmetro-chave que deve ser considerado quando se pretende estudar a toxicidade de nanoparticulas para o ambiente.
The rapid development of nanotechnology with the consequent increase in the production of nanoparticles and nanoproducts presents many opportunities but also many challenges. Nanotechnology has been described as a multidisciplinary field that develops a variety of engineered nanoparticles (ENPs) for medical and industrial applications. The properties that bring to ENPs special attention for commercial products – small size, large surface area and consequently high degree of reactivity – can also make them potentially harmful for human and ecosystem health. Therefore, assessing the potential risks associated with exposure of ENPs should be considered a major research priority before they are applied in commercial products and released to the environment. Aquatic (freshwater and marine) environment act as potential destinations for the ENPs released to the environment through direct and/or indirect sources, thus exposing aquatic organisms to high levels of pollutants. Zinc oxide nanoparticles (ZnO-NPs) are one of the ENPs most applied in a wide range of commercial products (e.g., sunscreens, cosmetics and paints) and its production is estimated to continue to rise in the upcoming years. As a consequence, the risk of aquatic environment contamination by these ENPs will increase. Toxicological studies have already demonstrated that nanoscale ZnO exert toxic effects in several organisms, such as crustaceans, algae and bacteria. The toxic effects of ZnO-NPs can be complex and may be dependent of several factors such as organism tested, abiotic factors (pH, salinity, water hardness, presence of natural organic matter), physico-chemical properties of NPs, adsorption phenomena, presence of other pollutants in the same environment, among others.
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Doumandji, Zahra. "Identification de marqueurs d’exposition et d’effets de nanoparticules métalliques sur modèle in vitro." Thesis, Université de Lorraine, 2019. http://www.theses.fr/2019LORR0067.
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En conséquence de l'extension de l’utilisation des nanoparticules dans différents secteurs industriels, le nombre de travailleurs potentiellement exposés ne cesse de croître, sans parfaitement connaître les propriétés toxicologiques de ces matériaux. Étant donné que les nanoparticules peuvent se trouver en suspension dans l’atmosphère professionnelle, l'inhalation représente une voie d'exposition professionnelle majeure. De ce fait, l’évaluation des risques liés à l’exposition aux nanomatériaux requiert d’entreprendre des études de toxicologie sur des modèles cellulaires des voies aériennes. Dans ce manuscrit, les réponses cellulaires et moléculaires des macrophages alvéolaires de rat (NR8383) exposés à des nanoparticules d’oxydes métalliques : ZnO, ZnFe2O4, NiZnFe2O4, Fe2O3, TiO2-NM105 et TiO2-NRCWE001, ont été étudiées, en combinant des analyses toxicologiques classiques (caractérisation des nanoparticules par microscopie électronique à transmission et par diffusion dynamique de la lumière, évaluation de la cytotoxicité par tests WST-1 et libération de LDH); et de criblage moléculaire à haut débit (analyses de transcriptomique et de protéomique). Des cellules NR8383 ont été exposées aux nanoparticules ZnO, ZnFe2O4, NiZnFe2O4, Fe2O3, TiO2-NM105 et TiO2-NRCWE001 pendant 24 h ce qui a permis de déterminer une dose sub-toxique pour chaque nanoparticule à laquelle les macrophages ont été exposés pour l’analyse moléculaire. Quatre heures suite à l’exposition des cellules aux nanoparticules, de nombreux gènes et protéines étaient différentiellement exprimés. Le stress oxydant était la réponse biologique adverse suite à l’exposition des cellules aux nanoparticules composées de zinc. En revanche, l’inflammation était la principale voie activée dans les cellules exposées à la forme anatase et rutile des nanoparticules de TiO2. En conclusion, cette étude expose les « empreintes biologiques » des deux groupes de nanoparticules d’intérêt. Enfin, notre étude combinée à des travaux antérieurs de la littérature pourraient aussi être profitables pour valider les biomarqueurs d’exposition et d’effets aux nanomatériaux suggérés afin de prédire les effets biologiques adversesAs a consequence of the extension of the use of nanoparticles in different industrial sectors, the number of potentially exposed workers continues to grow, without fully knowing the toxicological properties of these materials. Since nanoparticles can be aerosolized in the occupational atmosphere, inhalation is the major occupational exposure route. For this reason, risk assessment of exposure to nanomaterials requires toxicology studies to be conducted on cellular models of the airways. In this manuscript, the cellular and molecular responses of rat alveolar macrophages (NR8383) exposed to metallic oxide nanoparticles: ZnO, ZnFe2O4, NiZnFe2O4, Fe2O3, TiO2-NM105 and TiO2-NRCWE001, were studied, combining conventional toxicological analyzes (characterization of nanoparticles by transmission electron microscopy and dynamic light scattering, evaluation of cytotoxicity by WST-1 assays and LDH release); and high throughput molecular screening (transcriptomic and proteomic analyzes). NR8383 cells were exposed to the ZnO, ZnFe2O4, NiZnFe2O4, Fe2O3, TiO2-NM105 and TiO2-NRCWE001 nanoparticles for 24 h which allowed for the determination of a sub-toxic dose for each nanoparticle to which the macrophages were exposed for molecular analysis. Four hours after exposure NR8383 to nanoparticles, many genes and proteins were differentially expressed. Oxidative stress was the adverse biological response following exposure of cells to nanoparticles composed of zinc. In contrast, inflammation was the main activated pathway in cells exposed to the anatase and rutile form of TiO2 nanoparticles. In conclusion, this study exposes the "biological fingerprints" of the two groups of nanoparticles of interest. Finally, our study, combined with previous literature studies, could also be beneficial in validating biomarkers of exposure and effects of nanomaterials suggested in order to predict adverse biological effects
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Piot, Lucas. "Influence de l’énergie d’interface sur les transitions de phase sous pression : étude de nanoparticules d’oxydes fonctionnels." Thesis, Lyon 1, 2013. http://www.theses.fr/2013LYO10238/document.
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La modification des diagrammes de phase sous pression dans les nanomatériaux en comparaison de matériaux massifs est généralement reliée de façon univoque à l'énergie de surface. L'objectif de ce travail a consisté à étudier l'influence de l'énergie d'interface, définie par l'état de surface (défauts cristallins et chimie de surface) et l'énergie de surface, sur le comportement à haute pression de différents nanomatériaux pour lesquels un effet de taille est fréquemment rapporté. Le contrôle et la caractérisation de l'état de surface de nanoparticules d'Y2O3 nous ont permis de montrer que l'amorphisation sous pression rapportée dans la littérature n'est pas uniquement due à la réduction de la taille de grain mais nécessite une densité de défauts initiale, généralement non contrôlée. Une forte dépendance en taille de la pression de transition dans ZnO est avancée dans la littérature. L'étude sous pression de différents échantillons nanométriques de ZnO (issus de diverses voies de synthèse) a été effectuée par spectroscopie Raman et diffraction de rayons X. La qualité cristalline de ces derniers a été estimée par Photoluminescence, XPS, Raman et IR. Tandis que les échantillons présentant une forte densité de défauts conduisent à une augmentation de la pression de transition, le comportement d'un échantillon "sans défauts" ne diffère que peu de celui de ZnO massif. Différentes approches et extensions de modèles thermodynamiques sont proposées: modèles de Gibbs, Landau et Ginzburg-Landau. Ces derniers ouvrent la voie à la définition d'un protocole expérimental permettant d'obtenir des données fiables pour étudier les transitions de phase de nanomatériaux sous pressionThe modification of phase diagrams under pressure into nanosized materials in comparison with bulk ones is usually attributed to surface energy. The goal of this work has consisted into studying the influence of interface energy, which includes both the surface state (crystalline defects and surface chemistry) and surface energy, on the high-pressure behavior of several nanomaterials for which size effects has been reported. The control and characterization of the surface state for Y2O3 nanoparticles has enabled us to show that the pressure induced amorphization reported into literature is not only linked to size reduction but require an initial density of defects A strong size dependence of ZnO transition pressure is claimed into literature. The high-pressure study of different ZnO nanometric samples (obtained through several ways of synthesis) has been performed by Raman spectroscopy and X-ray diffraction. The crystalline quality of our samples has been investigated by photoluminescence, XPS, Raman and IR. Whereas samples exhibiting a high density of defects lead to an increase of pressure transition, the behaviour of “defect free” nanoparticles is rather equivalent to bulk one. Several approaches and extensions of thermodynamic models are submitted: model of Gibbs, Landau and Ginzburg-Landau. Those models open the way to the definition of an experimental protocol which allow to obtain reliable data in order to study phase transitions of nanomaterials under pressure
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Elhaj, Baddar Zeinah. "ENGINEERING ZINC OXIDE NANOPARTICLES TO BE USED AS NANOFERTILIZERS." UKnowledge, 2018. https://uknowledge.uky.edu/pss_etds/109.
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Zinc deficient soils, or soils with low Zn bioavailability, are widespread, which exacerbates Zn deficiency in human as crops grown on these soils have low Zn content. Often crop yields are also compromised. Fertilizers based on soluble Zn salts often have limited efficacy in such soils. In this research, we evaluate the performance of polymer coated and bare ZnO nanoparticles (NPs) in an attempt to overcome limitations of soluble Zn salts in alkaline soils. We first synthesized 20-30 nm bare ZnO NPs with different surface chemistries to impart colloidal stability to the particles. Bare ZnO were treated in phosphate solution under certain conditions leading to the formation of a core made of ZnO NPs that is covered by a shell of amorphous Zn3(PO4)2 (core-shell NPs). This confers a negative charge to the particles over a wide pH range. The addition of nonionic (neutral dextran) and polyelectrolyte (negatively charged dextran sulfate (DEX(SO4)) during the synthesis resulted in the formation of DEX and DEX(SO4) ZnO NPs. Dextran has a minimal effect on the surface charge of ZnO but dextran sulfate confers a net negative charge. Bare and core-shell ZnO NPs were both electrostatically stabilized whereas DEX and DEX(SO4) ZnO NPs were sterically and electrosterically stabilized, respectively. We investigated the effect of treating seeds with ZnO NPs on the growth and accumulation of Zn in wheat (Triticum aestivum) seedlings in comparison to ZnSO4. All ZnO NPs stimulated seedling growth. Seedlings accumulated higher Zn concentrations when treated with ZnO NPs than with ZnSO4. Zinc sulfate was toxic even at the lower exposure concentrations, which was demonstrated by significantly lower germination success and seedling growth. In the second experiment, we investigated the effect of pH on the attachment and dissolution of ZnO NPs in soil, as compared to ZnSO4. Soil pH was adjusted to 6 and 8, then the soil was spiked with 100 mg Zn/kg soil in the form of ZnSO4, bare, DEX, DEX(SO4), and core-shell ZnO NPs. The results showed that DEX and core-shell ZnO NPs had significantly higher total Zn in soil solution compared to ZnSO4 at pH 8, with little dissolution. Dissolved Zn was similar among treatments except ZnSO4 at pH 6, indicating little dissolution of the ZnO NPs at either pH value. We also found that the engineered coatings dictate the behavior of the particles in simple aqueous systems, but their properties are altered in natural soil solutions because of the dominant effect of natural organic matter (NOM) on their surface chemistry. Based on the outcomes of the previous two experiments, we selected DEX and bare ZnO NPs to test the efficacy of ZnO NPs in delivering Zn to the grain of wheat under greenhouse conditions. We performed two independent studies where seeds were either treated with the NPs or grown in a soil spiked with Zn at pH 6 and 8 and spiked with Zn treatments (nano and ionic). We found that treating seeds with bare ZnO NPs significantly enhanced grain Zn concentrations as compared to the control, DEX-ZnO NPs, and ZnSO4. There were no differences in grain Zn concentration of plants treated with ionic or nano Zn treatments regardless of the soil pH. This work has elucidated important principles which will help carry forward efforts at developing effective ZnO NP-based fertilizers. It also suggests that treatment of seeds with ZnO NPs is more effective than amending soil or treating seeds with ZnSO4.
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Shortell, Matthew P. "Zinc oxide quantum dot nanostructures." Thesis, Queensland University of Technology, 2014. https://eprints.qut.edu.au/76335/4/Matthew_Shortell_Thesis.pdf.
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Zinc oxide (ZnO) is one of the most intensely studied wide band gap semiconductors due to its many desirable properties. This project established new techniques for investigating the hydrodynamic properties of ZnO nanoparticles, their assembly into useful photonic structures, and their multiphoton absorption coefficients for excitation with visible or infrared light rather than ultraviolet light. The methods developed are also applicable to a wide range of nanoparticle samples.
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Johnson, Clint Edwin. "In vitro toxicity assessment of silver and zinc oxide nanoparticles." University of Western Australia. School of Biomedical, Biomolecular and Chemical Sciences, 2010. http://theses.library.uwa.edu.au/adt-WU2010.0119.
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Nanotoxicology is a nascent field of study concerned with the potential for nanotechnology to adversely impact human health or result in ecological damage. Nanomaterials can display unique physicochemical properties not present in the parent bulk material and it is these properties that may be a potential source of toxicity. There are a growing number of examples of nanomaterials functioning differently in biosystems compared to the parent bulk material. With the rapid growth of nanotechnology and increasing exposure of people to novel nanomaterials there is an urgent need to evaluate the toxicity of nanomaterials. In this study the toxicities of silver and zinc oxide nanoparticles were assessed. The effects of size and surface coating on the cytotoxicity and immunogenicity of silver nanoparticles were investigated, with cytotoxicity found to be inversely proportional to nanoparticle size. The subcutaneous penetration of zinc oxide nanoparticles was assessed to determine whether this material can be safely used as a UV filter in sunscreens and cosmetics. No dermal penetration was detected using a porcine in vitro model. Zinc oxide nanoparticles were also used as a model material to investigate nano-specific toxicity by comparing cytotoxicity and changes to gene expression with bulk scale zinc oxide. In both cases cytotoxicity and changes to gene expression were greater for zinc oxide nanoparticles. Methods and techniques to test the toxicity of nanomaterials in vitro and the implication for in vivo toxicity are only beginning to be elucidated. The methods and techniques used in this study, particularly nanomaterial stabilization in biofluids and toxicity testing using blood cell cultures, may assist the establishment of standard in vitro testing protocols for nanomaterials.
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O'Rourke, Shona Aisling. "The environmental toxicology of zinc oxide nanoparticles to the oligochaete." Thesis, Heriot-Watt University, 2013. http://hdl.handle.net/10399/2681.
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This thesis investigated the potential toxicity of zinc oxide nanoparticles (NPs) and bulk particles (both with and without organic matter (HA)) to the Californian Blackworm, Lumbriculus variegatus. The NPs and bulk particles in this thesis were characterised using numerous techniques. ZnO NPs were found to be 91 (13364) nm (median (interquartile range)) and ZnO bulk particles were found to be 237 (322165) nm (median (interquartile range)) by TEM. In the acute behavioural study (96 hour), ZnO NPs had a dose-dependent toxic effect on the behaviour of the worms up to 10mg/L whereas the bulk had no significant effect. This result, however, was mitigated by the addition of 5mg/L HA in the NP study whereas a similar addition enhanced the toxicity of the bulk particles at 5mg/L ZnO. In the chronic study (28 days), ZnO NPs and bulk particles were found to have a dose-dependent significant effect on the behaviour of the worms after 28 days, with NPs causing a significantly greater negative response than bulk particles at 12.5, 25 and 50mg/L ZnO. HA had no effect on the toxicity of either particle type in the chronic study. Acute (96 hour) oxidative stress in L. variegatus in response to ZnO NP and bulk particle (with and without 5mg/L HA) exposure was evaluated by examining the changes in glutathione (GSH) content of cells, since NPs are expected to have potential for toxicity via mechanisms such as oxidative stress. Neither ZnO NPs nor bulk particles (with and without 5mg/L HA) were found to induce significant changes in the GSH content of L. variegatus cells after 96 hours of exposure. The uptake, accumulation and depuration of ZnO NPs and bulk particles in L. variegatus over a 48 hour period of uptake and a 48 hour period of depuration were also investigated. This study found a high level of variability and it was concluded that the protocol employed was not suitable for investigating the uptake, bioaccumulation and depuration of ZnO NPs and bulk particles. Finally, histological techniques and a number of fixatives were evaluated for use with L. variegatus. Bouin’s solution was found the most suitable fixative for use with these worms, with no histological damage observed in the morphology of the worms after a 96 hour exposure to ZnO NPs and bulk particles (with and without 5mg/L HA). When considering the toxicology results from all experiments within this thesis it is concluded that ZnO NPs can cause both acute and chronic toxicity in terms of behavioural response, but do not cause acute oxidative stress in L. variegatus.
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Fernando, Joseph F. S. "Crystal seeding and photochemistry of gold-zinc oxide hybrid nanoparticles." Thesis, Queensland University of Technology, 2016. https://eprints.qut.edu.au/101206/1/Joseph_Fernando_Thesis.pdf.
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This project investigated the synthesis of hybrid nanoparticles of gold and zinc oxide by using photodeposition and crystal seeding approach. The study extended our understanding of the factors that determine nanocrystal size, shape and ratio of gold and zinc oxide in the hybrid system. Control at this scale is important from a materials-engineering viewpoint and for technological applications such as nonlinear optics, photocatalysis and photovoltaics. This research found that nonlinear optical absorption of zinc oxide can be enhanced by several orders of magnitude by coupling zinc oxide nanoparticles to gold nanoparticles.
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Ntozakhe, Luyolo. "Synthesis of modified zinc oxide nanoparticles using pneumatic spray pyrolysis for solar cell application." Thesis, University of Fort Hare, 2017. http://hdl.handle.net/10353/5862.
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In this work, the pneumatic spray pyrolysis was used to synthesize un-doped and carbon doped zinc oxide (ZnO) nanoparticles. The zinc acetate, tetrabutylammonium bromide and ethanol were used as starting materials for the desired ZnO nanoparticles and the prepared samples were annealed at 400 oC in the furnace. The as synthesized un-doped and carbon doped ZnO NPs were evaluated using X-ray diffraction (XRD), Scanning electron microscope (SEM), Energy dispersive x-ray spectroscopy (EDX), High-resolution transmission electron microscopy (HRTEM), Raman spectroscopy (RS) and Ultraviolet-visible spectroscopy (UV-Vis). XRD analysis of the synthesized NPs revealed peaks at 31.90°, 34.50°, 36.34°, 47.73°, 56.88°, 63.04°, 68.20°, and 77.33° belonging to the hexagonal Wurtzite ZnO crystal structure. The incorporation of C species into ZnO lattice was cross examined by monitoring the peak positions of the (100), (002) and (001) planes. These three main peaks of C-ZnO NPs show a peak shift to higher 2θ values which indicates substitutional carbon doping in ZnO NPs. SEM analysis has revealed that the as synthesized NPs have spherical shape and the morphology of the NPs change as the concentration of carbon increases. The EDX spectra of both un-doped and doped ZnO nanoparticles have revealed prominent peaks at 0.51 keV, 1.01 keV, 1.49 keV, 8.87 keV and 9.86 keV. Peaks at, X-ray energies of 0.51 keV and 1.01 keV respectively represent the emissions from the K-shell of oxygen and L-shell of zinc. The L-shell emission at 1.01 keV is considered as convolution of Zn 2p3/2 and Zn 2p1/2 photoelectron energies. The occurrence of these peaks in the EDX endorses the existence of Zn and O atoms in the PSP prepared samples. HRTEM analysis has revealed NPs size modal range from 6.65-14.21 nm for the PSP synthesized samples which is in mutual agreement with the XRD data calculated values. More over the selected area diffraction images displaying the fact that only the diffraction planes of (101), (002) and (100) are responsible for the diffraction pattern belonging to Wurtzite ZnO. RS analysis has revealed that the un-doped ZnO and doped ZnO samples have characteristic Raman vibration modes at 325 cm-1, and 434 cm-1 belonging to Wurtzite ZnO structure. Moreover, the prominent peak at 434 cm-1 which is the characteristic peak of E2(2) (high) mode of the Wurtzite ZnO and the E2(2) (high) has been red shifted by 4 cm-1, as compared to that found in the bulk ZnO. Additionally, the effect of carbon doping through Raman spectroscopy peak shifts of the E2(2) (high) mode, A1(LO) mode and multi-phonon has also been considered and discussed in detail. UV-Vis diffuse reflectance spectroscopy has revealed a red shift of the absorption edge with increase in C doping. Finally, the effect of nano-crystallite size and gradual prominence of C into ZnO lattice due to increase in C doping concentration in the PSP prepared nanoparticles was meticulously elaborated through Raman Spectroscopy analysis.
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Sharma, Vyom. "An investigation into the mechanism of toxicity of zinc oxide nanoparticles." Thesis, University of Bradford, 2011. http://hdl.handle.net/10454/5421.
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The wide scale use of ZnO nanoparticles (NPs) in the world consumer market has resulted in likelihood of exposure to human beings. The present study was aimed to assess the in vitro and in vivo interactions of ZnO NPs in the mammalian system and to elucidate the possible mechanism of their toxicity. Our in vitro results using human epidermal cells (A431), primary human epidermal keratinocytes and human liver cells (HepG2) demonstrated that cells exposed to ZnO NPs exhibit a decrease in cell viability which was independent of NP dissolution. ZnO NPs also induced oxidative DNA damage as evidenced by an increase in the Fpg sensitive sites. The reactive oxygen species triggered a decrease in mitochondrial membrane potential and an increase in the ratio of Bax/Bcl2 leading to apoptosis through the intrinsic pathway. In addition, ZnO NPs induced phosphorylation of JNK, P38 and P53ser15. The results from our in vivo studies using a mouse model showed that ZnO NPs induce lipid peroxidation, oxidative DNA damage and apoptosis in liver which further confirmed our in vitro findings. The data from the present study provide valuable insights into the cellular interactions of ZnO NPs and the underlying molecular mechanism of their toxicity. The results also stress the need for a comprehensive environmental health and safety assessment of engineered nanomaterials to ensure safer nanotechnology based products.
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Alasvand, Zarasvand Azita. "Comparative Analysis of Zinc Oxide Nanoparticles Induced Transcriptomic Responses in Arabidopsis." Thesis, North Dakota State University, 2019. https://hdl.handle.net/10365/31694.
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The impact that zinc oxide nanoparticles (ZnONP) have on plant physiological responses was evaluated by comparing gene expression changes after Arabidopsis thaliana plants were exposed to ZnONP, in comparison with ionic Zn2+ (ZnSO4) and non-treated controls. After treatment with ZnONP (concentration10 μg L−1), ionic Zn2+ (applied as ZnSO4 at a concentration of 19.7 μg/ L −1), expression analyses via RNA sequencing revealed that 369 genes were down regulated and 249 were upregulated (p < [FDR] 0.05, expression difference < 3). The downregulated genes in ZnONP treated seedlings compared to the Zn +2 ion and untreated controls were mainly abiotic stress (oxidative stress, low temperature) and biotic stress such as defense responsive genes based on the gene ontology analysis. The upregulated genes in response to ZnONP treated plants compared to the Zn +2 ion control plants were mainly photosynthesis, light harvesting complex, and hormone responsive genes such as abscisic acid.
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Wallace, Rachel. "Physicochemical characterisation of zinc oxide nanoparticles for use in toxicity studies." Thesis, University of Leeds, 2013. http://etheses.whiterose.ac.uk/5899/.
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This thesis is focused on the detailed physicochemical characterisation of zinc oxide (ZnO) nanoparticles (NPs) intended for use in toxicological investigations. A characterisation protocol has been developed in order to determine detailed physicochemical characteristics of 5 ZnO NP samples, selected to investigate in in vitro toxicity assays. The characterisation protocol aims to establish the samples’ distribution of particle sizes, morphology, crystallinity, phase content, purity, surface composition, dispersion and solubility and as such includes the following techniques: inductively coupled plasma mass spectrometry (ICP-MS), X-ray diffraction (XRD), BET gas adsorption, thermogravimetric analysis with evolved gas analysis by Fourier transform infra-red spectroscopy (TGA-EGA with FTIR), FTIR, X-ray photoelectron spectroscopy (XPS), nuclear magnetic resonance spectroscopy (NMR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), dynamic light scattering (DLS), plunge freezing transmission electron microscopy (PF-TEM) and Zeta potential measurement. Initially 12 commercial samples were sourced and screened using TEM to obtain information on the average particle size. 3 of the commercial samples were then selected to carry forward to toxicity studies: EN-Z-1, EN-Z-2 and EN-Z-3. Synthesis of ZnO NPs was investigated in house by a flame spray pyrolysis and a polyol route; 2 synthesized samples were carried forward to the toxicity studies: EN-Z-4 and EN-Z-6. A coating was detected on the surface of EN-Z-1 (a colloidal suspension in water), identified as an aliphatic polyether (TGA-EGA, FTIR, XPS and NMR). Physically and chemically adsorbed H2O and CO2 was detected at the surface of the other 4 samples, which were all dry powders. A small amount hydrozincite was present in EN-Z-2 and EN-Z-3, identified by XRD, TGA-EGA, FTIR, XPS and NMR. Additionally, a small amount of diethylene glycol was identified on the surface of EN-Z-6, left over from synthesis. The dispersion and solubility of the samples in water, Dulbecco’s modified Eagle Medium (DMEM) and bovine serum albumin (BSA) was investigated by DLS, PF-TEM and ICP-MS the results of which are presented in Chapter 6. Most samples showed similar dissolution kinetics and equilibrium solubility with the exception of EN-Z-1 which showed slower dissolution, presumably due to the coating present on the NPs. Due to the equilibrium solubility of ZnO in DMEM, for concentrations of ZnO below 10 μg/ml, a significant amount is dissolved or re-precipitated as zinc carbonate. The agglomeration and solubility of ZnO NPs was found to increase when suspended in DMEM as compared to in water. The solubility of ZnO was found to increase with decreasing solution temperature (37 and 25 ºC). The addition of BSA was found to have a dispersing effect on ZnO NP suspensions. PF-TEM was investigated as an alternative technique to DLS for measuring size distributions of ZnO NPs in suspensions. It was determined that PF-TEM measurements give an accurate representation of the range of agglomerates in the suspension, however the sampling size is very low and data processing is time consuming and therefore the technique should be used as a complementary technique to DLS. The cytotoxicity and genotoxicity of ZnO NPs was assessed using the MTT (thiazolyl blue tetrazolium bromide) and comet assay respectively. A lower toxicity was measured for ZnO NP powder samples as compared to the coated colloidal dispersion. The polymer coating enhances NP interaction with lipid membranes which may increase toxicity through increased cellular uptake followed by intracellular dissolution. Coated and uncoated ZnO NPs are taken up by A549 cells and were located in both the cytoplasm and the nucleus. In cells exposed to 100 μg/ml EN-Z-4 and EN-Z-6, smaller than primary particle size NPs were located in the cells, suspected to be zinc carbonate particles formed from dissolved zinc precipitating from solution in the extracellular or intracellular environment.
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Abou, Chaaya Adib. "Conception de nanomatériaux à base d'oxyde par ALD : de la détection aux membranes." Thesis, Montpellier 2, 2014. http://www.theses.fr/2014MON20117/document.
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Conception de nanomatériaux à base d'oxyde par ALD : de la détection aux membranesIn this context, the aim of this PhD work is the synthesis of different nanostructured materials based on ALD oxide thin film (Al2O3, ZnO and Al2O3/ZnO nanolaminates) deposited on different types of substrates such as silicon substrate, glass, nanofibers, multipores and monopores membranes, PET and gold coated nickel dogbones. ALD deposition was performed on those substrates with changing the film thickness (number of cycles), the deposition temperature, and the film composition (doping, multilayers etc.). After the ALD deposition chemical, structural, optical, electrical and mechanical characterization were performed on the ALD deposited layer in order to study the influence of the deposition parameters on the thin film properties. The deposited and characterized ALD films were investigated on different fields:• Optical properties for solar cell applications (Chapter 2) • UV detection (Chapter 3)• Protective coating and gas barrier (chapter 4)• Ionic transport, water desalination, Mass spectrometry, DNA sequencing and Gas purification (chapter 5)The atomic layer deposition technique combined with nanostructured templates show several advantages on several application fields that will be reported on this thesis. The structural and properties evolution of the ALD thin film with the deposition parameter evolution leaded to a doped ZnO layer and Al2O3/ZnO multilayer with tunable optical, electrical and mechanical properties that can be interesting for different applications such as solar cell and UV detection. The conformal coating on high aspect ratio template with the angstrom range thickness control offered by the atomic layer deposition technique meted our target on nanopores diameter tuning for different applications on the nanometeric range such as gas purification. Moreover the compatibility of the deposited materials with some biological function leaded to a combination between nanostructure materials and biological function that shows promising results for different applications such as ionic transport, water desalination, mass spectrometry and DNA sequencing
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Allard, Garvin Richard Johan. "Synthesis and characterization of zinc-doped magnetic nanoparticles for diagnostic studies." University of the Western Cape, 2015. http://hdl.handle.net/11394/4815.
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Magister Scientiae - MScIn the present study we report the synthesis and characterization of iron oxide magnetic nanoparticles doped with zinc in an attempt to enhance the magnetic properties. The nanoparticles were prepared via the co-precipitation route and capped with 3-phosphonopropionic acid (3-PPA). The amount of zinc dopant was varied to yield nanoparticles with the general formula ZnxFe3-xO4 (x=0, 0.1, 0.2, 0.3, 0.4). Characterization was carried out using high resolution transmission electron microscopy (HRTEM), X-ray diffraction spectroscopy (XRD), energy-dispersive X-ray spectroscopy (EDS), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA) and superconducting quantum interference device (SQUID) analysis. Results from HRTEM, XRD and SQUID confirm that doping took place and x=0.2 was found to be the doping limit for these nanoparticles with a maximum size of 10.73 nm and saturation magnetization of 73.37 emu/g. The EDS further confirmed successful doping with zinc, while FTIR and TGA confirmed successful capping with 3-PPA. Despite agglomeration at all doping levels, these nanoparticles show great potential for application in breast cancer diagnostic studies.
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Valour, Arnaud. "Synthèse d'oxyde de zinc dopé azote sous formes de poudre et de couche mince : caractérisation du type de semiconductivité." Thesis, Rennes 1, 2017. http://www.theses.fr/2017REN1S014/document.
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Cette thèse fait suite à des travaux ayant permis, de manière non reproductible, la stabilisation de l’oxyde de zinc de type-p (p-ZnO:N) sur une période de plus de deux ans par décomposition de ZnO2 sous flux de NH3. L’objectif de ces travaux était de maîtriser de manière reproductible la synthèse de p-ZnO:N sous formes de poudre, puis de couche mince, dans l’optique de réaliser des homojonctions p-ZnO:N/n-ZnO ayant de potentielles applications dans le domaine de l’optoélectronique. Dans ce but, différents paramètres de la synthèse ayant permis initialement l’obtention de p-ZnO:N fortement lacunaire en zinc (20%) ont été étudiés sans aboutir de nouveau à la stabilisation du caractère-p. La formation in-situ d’impuretés NO3- mise en évidence conduit à une ambiguïté quant à l’origine du type-p dans notre matériau. Parallèlement, une nouvelle voie de synthèse a été mise en place, en utilisant l’approche colloïdale, permettant d’obtenir des nanocristaux de ZnO inférieurs à 10 nm facilement convertibles en nanoparticules de ZnO2 par simple traitement avec une solution diluée d’H2O2 à température ambiante. Le matériau final ZnO:N est obtenu après nitruration sous flux d’ammoniac à 250°C. Ces résultats ont été efficacement transposés à la réalisation de couches minces (CM) de ZnO:N par dip-coating, mais les mesures Mott-Schottky ont également révélé une conductivité de type-n pour tous les échantillons. Enfin, les résultats préliminaires des calculs théoriques menés en parallèle de cette thèse nous ont amenés à reconsidérer les conditions de synthèse pour favoriser l'insertion de NH3 / NH4+ lors de la préparation des échantillons dans la quête de p-ZnO:NCette thèse fait suite à des travaux ayant permis, de manière non reproductible, la stabilisation de l'oxyde de zinc de type-p (p-ZnO:N) sur une période de plus de deux ans par décomposition de ZnO2 sous flux de NH3. L'objectif de ces travaux était de maîtriser de manière reproductible la synthèse de p-ZnO:N sous formes de poudre, puis de couche mince, dans l'optique de réaliser des homojonctions p-ZnO:N/n-ZnO ayant de potentielles applications dans le domaine de l'optoélectronique. Dans ce but, différents paramètres de la synthèse ayant permis initialement l'obtention de p-ZnO:N fortement lacunaire en zinc (20%) ont été étudiés sans aboutir de nouveau à la stabilisation du caractère-p. La formation in-situ d'impuretés NO3- mise en évidence conduit à une ambiguïté quant à l'origine du type-p dans notre matériau. Parallèlement, une nouvelle voie de synthèse a été mise en place, en utilisant l'approche colloïdale, permettant d'obtenir des nanocristaux de ZnO inférieurs à 10 nm facilement convertibles en nanoparticules de ZnO2 par simple traitement avec une solution diluée d'H2O2 à température ambiante. Le matériau final ZnO:N est obtenu après nitruration sous flux d'ammoniac à 250°C. Ces résultats ont été efficacement transposés à la réalisation de couches minces (CM) de ZnO:N par dip-coating, mais les mesures Mott-Schottky ont également révélé une conductivité de type-n pour tous les échantillons. Enfin, les résultats préliminaires des calculs théoriques menés en parallèle de cette thèse nous ont amenés à reconsidérer les conditions de synthèse pour favoriser l'insertion de NH3 / NH4+ lors de la préparation des échantillons dans la quête de p-ZnO:N
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Orchard, Katherine Lorraine. "The mild synthesis of zinc oxide nanoparticles and nanocomposites via hydrolysis of well-characterised zinc organometallics." Thesis, Imperial College London, 2011. http://hdl.handle.net/10044/1/17786.
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This thesis centres on the development of a clean, one step method for generating surface-functionalised zinc oxide (ZnO) nanoparticles for application in the synthesis of well-dispersed inorganic-organic nanocomposites. The nanoparticle synthesis method utilises the controlled hydrolysis of organometallic zinc compounds, employing diethylzinc as a bulk precursor and an alkylzinc carboxylate as a substoichiometric, secondary precursor to deliver the capping ligands. A series of ethylzinc carboxylate species were synthesised and studied by NMR spectroscopy (EtZn(OOCR); R = H, CH3, and (CH2)nCH3, where n = 4, 10, 16). The ligand stoichiometry of the complexes was found to depend on the nature of the solvent (coordinating vs. non-coordinating), and single crystal X-ray experiments indicated that the strength of the donor interaction of a coordinating solvent affects the nuclearity of the complex‟s repeat unit in the solid state. In addition, the isolated complexes of the acetate derivative were active catalysts for the copolymerisation of CO2 and cyclohexene oxide. The ZnO nanoparticle synthesis route was first explored in the absence of a polymer matrix and was proven to yield hydrophobic nanoparticles with a narrow size distribution without the need for size selection steps (average particle size 3.6 ± 0.2 nm, σ = 15% using stearate; HR-TEM). The effect of varying different synthesis parameters on the resulting ZnO particle size and morphology was investigated. Additional inorganic zinc phases were observed on slowing the reaction rate, allowing insight into the mechanism of delivery of carboxylate groups to the growing nanoparticle surfaces. Finally, in situ ZnO/epoxy resin nanocomposites were prepared. The degree of nanoparticle dispersion improved with surface-functionalisation in the order stearate < uncapped < benzoate (TEM), which correlated with the nature of the particle-matrix interaction (DSC). In situ prepared nanoparticles (uncapped) were also introduced into conventional microcomposites and found to improve the composite density and thermal conductivity relative to the highest loading of microparticles alone.
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Hirschmann, Johannes [Verfasser], and Marcus [Akademischer Betreuer] Halik. "Electrical Characteristics of Functionalized Zinc Oxide Nanoparticles / Johannes Hirschmann. Gutachter: Marcus Halik." Erlangen : Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), 2014. http://d-nb.info/1054342687/34.
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Urban, Ben E. "Zinc Oxide Nanoparticles for Nonlinear Bioimaging, Cell Detection and Selective Cell Destruction." Thesis, University of North Texas, 2013. https://digital.library.unt.edu/ark:/67531/metadc271908/.
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Light matter interactions have led to a great part of our current understanding of the universe. When light interacts with matter it affects the properties of both the light and the matter. Visible light, being in the region that the human eye can "see," was one of the first natural phenomenon we used to learn about our universe. The application of fundamental physics research has spilled over into other fields that were traditionally separated from physics, being considered two different sciences. Current physics research has applications in all scientific fields. By taking a more physical approach to problems in fields such as chemistry and biology, we have furthered our knowledge of both. Nanocrystals have many interesting optical properties. Furthermore, the size and properties of nanocrystals has given them applications in materials ranging from solar cells to sunscreens. By understanding and controlling their interactions with systems we can utilize them to increase our knowledge in other fields of science, such as biology. Nanocrystals exhibit optical properties superior to currently used fluorescent dyes. By replacing molecular dyes with nanoparticles we can reduce toxicity, increase resolution and have better cellular targeting abilities. They have also shown to have toxicity to cancer and antibacterial properties. With the understanding of how to target specific cells in vitro as well as in vivo, nanoparticles have the potential to be used as highly cell specific nanodrugs that can aid in the fight against cancer and the more recent fight against antibiotic resistant bacteria. This dissertation includes our work on bioimaging as well as our novel drug delivery system. An explanation of toxicity associated with ZnO nanoparticles and how we can use it and the nonlinear optical properties of ZnO for nanodrugs and nanoprobes is presented.
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Wilkinson, John Henry. "Picosecond time-resolved photoluminescence of zinc oxide single crystals, films and nanoparticles /." Electronic thesis, 2003. http://etd.wfu.edu/theses/available/etd-09162005-083525/.
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Young, Michael I. "Synthesis of zinc oxide nanoparticles with different morphologies by wet chemistry routes." Thesis, Loughborough University, 2016. https://dspace.lboro.ac.uk/2134/25368.
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The objectives of this project were to synthesise semi-conducting ceramic nanoparticles including zinc oxide (ZnO) and aluminium doped zinc oxide (AZO) through a wet chemistry route to obtain nanoparticles with a controlled size and morphology. Wet chemistry methods (co-precipitation method and hydrothermal method) were used to synthesise ZnO and AZO particles. In the synthesis, various compounds and morphologies were synthesised. ZnO, Zn(OH)2 and unknown phases were co-precipitated, with only ZnO obtained following hydrothermal treatment. Morphologies ranging from platelets, flower-like, nanorods and microflowers were obtained. Particle sizes as small as 11 nm were characterised. Nanorod and nanosphere AZO particles were also synthesised with the results indicated the average grain size decreasing with increasing Al atomic content. Three orthogonal arrays were carried out to investigate the effects of the reaction parameters on the size and morphology of ZnO particles. The applicability of the orthogonal array was successful, with the optimum parameters of both hydrothermal experiments showing an increase in aspect ratio. The L/D ratio of ZnO nanorods obtained in the confirmation experiment increased to 9.4 which was larger than the ZnO synthesised using other reaction conditions (1.0 8.0). Scanning electron microscopy, transmission electron microscopy and X-ray diffraction were used to characterise the properties of the obtained particles. Morphology, crystallinity and particle size were all characterised.
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Pokhrel, Lok R., Brajesh Dubey, and Phillip R. Scheuerman. "Developmental Phytotoxicity of Silver and Zinc Oxide Nanoparticles to the Crop Plants." Digital Commons @ East Tennessee State University, 2012. https://dc.etsu.edu/etsu-works/2950.
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Saliba, Sarmenio. "Thermotropic and lyotropic liquid crystals for the formation of zinc oxide nanohybrids." Toulouse 3, 2011. http://thesesups.ups-tlse.fr/1598/.
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Le travail présenté dans ce manuscrit décrit l'incorporation de matériaux inorganiques à l'intérieur des matrices organiques. Notre ambition était de réussir à hybrider des nanostructures de ZnO avec des matériaux cristal liquides (CL). Ceci a été réalisé en utilisant différentes stratégies, dont le choix dépendait des propriétés finales du matériau. L'objectif était non seulement de réaliser la synthèse et la stabilisation des nanoparticules (NP), mais aussi d'étudier leur organisation dans un milieu cristal liquide. A cette fin, la première approche envisagée a consisté dans la fonctionnalisation des NPs isotropes préformées de ZnO par des ligands CLs thermotropes. Ceci a été rendu possible en utilisant un mécanisme d'échange de ligands. En raison d'un équilibre dynamique à la surface de ZnO, les molécules mésogènes peuvent s'organiser à la surface des NPs, donnant naissance à des hybrides CL/NP possédant des propriétés innovantes. Une seconde approche utilisant des cristaux liquides lyotropes, a ensuite été utilisée pour organiser les NPs. Dans ce cas, les NPs ont été synthétisé directement à l'intérieur des phases lyotropes. La synthèse de ZnO a donc été confinée à des domaines de taille définie. La forme de ces domaines permettant un contrôle direct de l'organisation des NPs. En dehors de l'organisation des NPs, notre objectif a consisté dans l'élaboration des nano-objets anisotropes assistée par des CL. Les molécules thermotropes avec une structure ramifiée se sont révélés être des modèles de croissance remarquable pour des nanocristaux anisotropes de ZnO. Cette croissance anisotrope est en particulier influencée par la taille des molécules CLsThe work presented in this manuscript describes the incorporation of inorganic materials inside organic hosts. Our ambition was to successfully hybridize ZnO nanostructures with liquid crystals. This was achieved using different strategies, the choice of which depended on the desired properties of the final material. The objective was not only the synthesis and stabilization of the nanoparticles within, but also their organization in the LC medium. One approach was the functionalization of preformed ZnO spherical nanoparticles by thermotropic LC ligands. This was made possible using a ligand exchange mechanism. Due to a dynamic equilibrium at the surface of ZnO NPs, the mesogenic molecules could exhibit order at the molecular level, giving rise to novel LC/NP hybrids with enhanced LC properties. The organization of NPs could also be induced by the use of lyotropic liquid crystals. In this case, the NPs were not simply doped into a LC material, but synthesized directly inside the lyotropic phases. The synthesis of ZnO was therefore confined to domains of defined size and shape which can directly control the organization of the nanostructures growing within. Apart from organization of NPs, our constant objective was the fabrication of anisotropic nanoobjects via LC-assisted synthesis. Thermotropic liquid crystals consisting of novel low molecular weight branched mesogens have proved to be remarkable templates for anisotropic growth of ZnO nanocrystals. This anisotropic growth was also found to be influenced by the size of the LC molecules as observed with the fabrication of ZnO inside LC polymers. This work has shown the possibility of integrating inorganic material in LCs providing that the two constituents are able to sufficiently interact with one another
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Zhu, Yao. "ZnO nanoparticles as a luminescent down-shifting layer for solar cells." Thesis, Lyon, INSA, 2015. http://www.theses.fr/2015ISAL0090/document.
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Le but de cette thèse était de concevoir des matériaux à base de nanoparticules de ZnO qui puissent être utilisés de manière efficaces comme couche de down-shifting sur la face avant des cellules solaires photovoltaiques. Le défi principal a donc été d’obtenir des nanoparticules de ZnO avec un rendement de photoluminescence (PL QY) aussi élevé que possible. Diverses méthodes ont été et comparées utilisées pour la synthèse de nanoparticules de ZnO. Nous avons en premier lieu étudié des particules synthétisées par voie physique (le dépôt par jet d’agrégats de basse énergie, LECBD). Les particules résultantes démontrent une faible PL QY. Nous avons par la suite étudié des particules commerciales qui se sont comportées comme celles issues de la LECBD. Par conséquent, nous ne les avons pas retenues. Enfin, nous nous sommes concentrés sur des particules produites par voies chimique humide: la co-précipitation de l’acétate ou du sulfate de zinc en présence d’hydroxyde alcalin. Pour chaque cas, les paramètres de synthèses ont été variés pour optimiser les propriétés optiques en vue de l’effet de down-shifting. Avec un choix approprié de la nature (Li+) et de la quantité d’ions alcalins, le PL QY a été accru à 13 %. Nos résultats reproduisent l’état de l’art concernant cette technique. Cependant, la technique par hydrolyse s’est révélée bien plus intéressante. La seule réaction d’hydrolyse n’a pas initialement conduit à des particules très brillantes. Nous avons donc proposé une approche originale : l’ajout d’un acide faible, l’acide polyacrylique (PAAH), durant la synthèse. Alors que le PAAH a déjà été utilisé comme agent passivant de la surface de ZnO, son utilisation pendant la synthèse n’a jamais été tentée. Notre travail montre que en contrôlant la quantité et le poids moléculaire (longueur de chaine) du PAAH introduit pendant la croissance, un nanocomposite hybride très efficace à base de nanoparticules de ZnO et de PAAH peut être obtenu, avec un PL QY aussi élevé que 20 %. En mélangeant le PAAH avec son sel de sodium, PAANa, le nanocomposite présente un PL QY record de 50%, qui augmente jusqu’à 70 % après un mois. Les raisons physico-chimiques de cet accroissement sont discutées dans le manuscrit. Nos explications pointent vers un effet combiné de la taille, de la morphologie et de la composition. Dans la partie suivante, des nanoparticules de ZnO pouvant être dispersées dans l’eau ont été obtenues avec succès tout en maintenant leur rendement quantique entre 20 % et 34 % ; ce en utilisant un mélange de PAAH/PAANa de ratio volumique, de concentration et de volume réactionnel optimaux. Nous insistons sur la nécessité d’obtenir un compromis entre une bonne capacité de dispersion et un fort PL QY. Cette partie de la thèse pave la voie vers des applications industrielles ultérieures.Finalement, l’effet de down-shifting des nanoparticules luminescentes de ZnO a été simulé pout déterminer le gain potentiel de rendement de cellules photovoltaïquesIn this thesis, we aim at designing mechanically stable ZnO nanoparticle based materials as a luminescent down-shifting layer that can be processed on a scalable amount and deposited on standard solar cells at a reduced cost. The main challenge was thus to get ZnO nanoparticles with as high photoluminescence quantum yield (PL QY) as possible. Different methods have been used and compared to synthesize ZnO nanoparticles. We have first studied particles synthesized by a physical route (the Low Energy Cluster Beam Deposition relying on the adiabatic expansion of a plasma). The resulting particles did not exhibit a PL QY high enough to be interesting for down-shifting. We next investigated commercial particles which behaved as the LECBD ones. We consequently discarded them. Eventually, we concentrated on nanoparticles produced by wet chemistry. Two routes were explored: the conventional co-precipitation method of Zn acetate or sulfate in presence of an alkaline hydroxide and the hydrolysis of ZnEt2. For both cases the synthesis parameters have been tuned to optimize the optical properties for down-shifting process. When appropriately choosing the alkaline ion (Li+ instead of K+) nature and amount, the PL QY has been increased to 13 % in the co-precipitation method. Our results reproduce the state-of-the-art knowledge concerning this technique. The hydrolysis route proved to be even more interesting. The sole hydrolysis reaction did not lead to very bright particles. We have thus proposed an original strategy: the addition of a weak acid, the polyacrylic acid (PAAH) during the synthesis. If PAAH has been used previously as a passivating capping agent of ZnO, its use during the synthesis has never been tempted. Our work shows that by tuning the amount and molecular weight (chain length) of PAAH introduced during the synthesis, a very efficient hybrid nanocomposite consisting of ZnO nanopaerticles in a PAAH matrix can be obtained with PL QY as high as 20 %. When mixing PAAH to its sodium salt PAANa, the nanocomposite exhibits record values of PL QY of 50 %, increasing to 70 % over a month. The physico-chemical reasons for this enhancement are discussed in the manuscript. Our explanations point to a combined effect of the size, morphology and composition. In the subsequent part, ZnO NPs dispersible in water have been successfully achieved while maintaining their PL QY high, between 20 % - 34 %, using a PAAH/PAANa mixture at the optimal volume ratio, concentration, lengths and volume. We highlight the need to get a compromise between a good dispersibility and a high PL QY. This part of the thesis paves the way for the further industrial applications. Finally, the down-shifting effect of luminescent ZnO nanoparticles on solar cells has been simulated to obtain a potential enhancement of solar cell efficiency by the ZnO NPs down-shifting layer
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Scown, Tessa M. "Uptake and effects of nanoparticles in fish." Thesis, University of Exeter, 2009. http://hdl.handle.net/10036/93696.
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Nanotechnology is a rapidly growing industry of global economic importance, with new technologies exploiting the novel characteristics of materials manufactured at the nanoscale being developed for use within the biomedical, electronic, energy production and environmental sectors. The unusual properties of engineered nanomaterials (ENMs) that make them useful in such applications have led to concerns regarding their potential impact on the environment. The aquatic environment is particularly at risk of exposure to ENPs, yet, there is currently little known about their behaviour in aquatic systems, their capacity to be taken up by aquatic organisms or their potential toxic effects. The studies that were conducted during this work sought to investigate the ecotoxicology of a range of metal and metal oxide nanoparticles using fish as a vertebrate model. In order to gain a better understanding of the uptake and effects of ENMs in fish, rainbow trout (Oncorhynchus mykiss) were exposed to nanoparticulate (34 nm) and bulk (>100 nm) titanium dioxide particles via the water column (500 and 5000 µg L-1), and to titanium dioxide nanoparticles via the diet (0.1 and 1 mg g-1 food) and via intravenous injection (1.3 mg kg-1 body weight). Uptake of titanium dioxide into the tissues of trout after waterborne and dietary exposure was found to be very low, suggesting limited bioavailability of the nanoparticles to the fish, although small amounts of uptake of titanium dioxide across the gill epithelial membrane were observed using coherent anti-stokes Raman scattering. Intravenously injected titanium dioxide accumulated and was retained in the kidneys for up to 21 days, but no adverse effect on kidney function was detected. Silver nanoparticles are already in widespread use in a variety of consumer products such as wound dressings, food containers, sock fabrics and paints, principally for their antimicrobial activity. Despite its growing commercialisation, there is little known about the environmental effects of the use of nanoparticulate silver in these products. In order to investigate these potential effects, rainbow trout were also exposed to 10 nm, 35 nm and bulk (0.6-1.6 µm) silver particles via the water column at concentration of 10 and 100 µg L-1. Uptake of silver in the gills and liver of trout occurred, with smaller nanoparticles showing a greater propensity for association with gill tissue, but with no significant differences in uptake between particles of different sizes in the liver. No increases in lipid peroxidation were detected in gills, liver or blood plasma of trout, however, expression of cyp1a2 was significantly up-regulated in exposures to 10 nm silver particles in the gill, suggesting an increase in oxidative metabolism. In an attempt to develop an effective high through-put in vitro screening assay for ENMs, the suitability of isolated rainbow trout primary hepatocytes was examined as a potential model for in vitro screening of a range of toxicological endpoints in response to nanoparticles and for studying uptake of nanoparticles into cells. The hepatocytes retained a good level of functionality after culturing as evidenced by vitellogenin production in response to the synthetic oestrogen, 17β-oestradiol. The cultured hepatocytes, however, showed limited responses on exposure to titanium dioxide, zinc oxide, cerium oxide and silver nanoparticles for lipid peroxidation and glutathione-s-transferase activity assays. Furthermore, the hepatocytes were unresponsive to the induction of these biological responses in the positive controls, suggesting they are not a good model for investigating the potential toxic effects of ENMs in terms of these endpoints. Uptake of the nanoparticles into the cells, however, was demonstrated by coherent anti-stokes Raman spectroscopy, indicating that this in vitro assay may provide a useful model for studying uptake of ENPs into cells. The studies conducted in this thesis contribute the science base regarding the bioavailability of ENPs in aquatic media as well as highlighting the importance of characterisation of ENPs in understanding their behaviour, uptake and effects in aquatic systems and in fish.
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Mgwili, Phelisa Yonela. "Graphenated organic nanoparticles immunosensors for the detection of TB biomarkers." University of the Western Cape, 2017. http://hdl.handle.net/11394/6355.
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Magister Scientiae - MSc (Chemistry)Pulmonary Tuberculosis (TB) a disease second to HIV/AIDS is a global health problem that arises in two states; as an active state and as a latent state. Diagnosis of active TB is tedious and requires expensive procedures since there is no recognizable method for the sole detection of active TB. The current diagnosis consists of chest X-rays and multiple sputum cultures used for acid-fast bacilli detection. The TB diagnosis of children is particularly difficult which further complicates the diagnosis. Thus, rapid identification of this pathogen is important for the treatment and control of this infection to allow effective and timely therapy. In an effort to solve this issue, this study reports the development of immunosensors constructed with electroactive layers of amino groups functionalized graphene oxide (GO) doped respectively with green synthesized zinc oxide (ZnO NPs) nanoparticles and silver (Ag NPs) nanoparticles on glassy carbon electrodes. The surface morphology of GO, ZnO NPs, Ag NPs and their composites was revealed by employing High-Resolution Transmission Electron Microscopy (HR-TEM) and High-Resolution Scanning Electron Microscopy (HR-SEM) while the composition and structure of these materials were studied using Fourier Transform Infra-Red Spectroscopy (FTIR). The resultant graphene oxide-metallic composites were covalently attached with CFP-10 and/or ESAT-6 antibodies to achieve the electrochemical detection. The immunosensor was then used for the impedimetric and amperometric detection of anti-CFP-10 and/or anti-ESAT-6 antigens in standard solutions.
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Tshoko, Siphokazi. "Spectroelectrochemical graphene-silver/zinc oxide nanoparticulate phenotype biosensors for ethambutol and pyrazinamide." University of the Western Cape, 2019. http://hdl.handle.net/11394/6842.
Full textAbstract:
>Magister Scientiae - MScTuberculosis (TB), a deadly disease second to HIV/AIDS, is a global health problem. Diagnosis of active tuberculosis is tedious and requires expensive procedures since there is no recognizable method for sole detection of active TB. Although this is a deadly disease, treatment drug toxicity is also an issue that also causes fatalities in diagnosed patients. Therefore, a rapid sensitive and specific diagnostic method is imperative for TB drug management. In this study spectroscopic and/or electrochemical biosensors were developed for the detection and quantification of TB treatment drugs. The biosensors were constructed with electroactive layers of graphene oxide coupled to silver nanoparticles and/or zinc oxide nanoparticles. These nanoparticles coupled with graphene oxide sheets were covalently attached onto the enzymes such as Cytochrome P450-2D6 to achieve the electrochemical detection of the TB treatment drugs and obtain the required electron transfer between the electrode surface and enzyme. The surface morphology of graphene oxide, nanoparticles as well as the green synthesized nanocomposites were achieved using High-Resolution Transmission Electron Microscopy (HRTEM), Atomic Force Microscopy (AFM), and High- Resolution Scanning Electron Microscopy (HRSEM) while the elemental analysis were obtained using Fourier Transform Infrared Spectroscopy (FTIR), Energy Dispersive X-Ray (EDX), Raman spectroscopy and X-Ray diffraction (XRD). Additionally, the optical properties of the developed nanocomposites where further characterised using Small Angle X-ray Scattering (SAXS), Photoluminescence Spectroscopy (PL) and Ultraviolet Spectroscopy (UV-vis). The electrochemical studies were obtained using cyclic voltammetry (CV) and showed an increase in electron conductivity for the green synthesized zinc oxide nanoparticles coupled with graphene oxide (ZnONPs/GO) and silver nanoparticles coupled with graphene oxide (AgNPs/GO) nanocomposite which was an indication that they were suitable as platforms towards biosensor development. Furthermore, amperometric technique was also used for biotransformation of the TB treatment drugs (Ethambutol and Pyrazinamide) in standard solutions of 0.1 M phosphate buffer (pH 7.0). Furthermore, the sensitivity value of 0.0748 μA/μM was determined for the ethambutol biosensor while a value of 0.1715 μA/μM was determined for the pyrazinamide biosensors. Very good detection limits were obtained for the standard solutions of ethambutol and pyrazinamide where a value of 0.02057 nM was determined for ethambutol at concentration linear range of 50 μM – 400 μM. Additionally, a value of 0.8975 x 10-2 nM was determined for pyrazinamide at the concentration linear range of 100 μM – 300 μM. The determined limit of detections have provided a clear indication that these biosensors have potential of being used in human samples since these values are below the peak serum concentrations of these drugs in TB diagnosed patients as reported in literature. This was further confirmed by the limit of quantification values determined for each biosensor where a value of 0.8975 x 10-2 nM was determined for pyrazinamide and a value of 0.02057 nM was determined for ethambutol.
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Deka, Priyanka. "The Effect of Zinc Oxide Nanoparticles on Plants, and on Host-Pathogen Interactions." Diss., North Dakota State University, 2019. https://hdl.handle.net/10365/29270.
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Zinc oxide nanoparticles (ZnO NPs) are a type of engineered nanomaterial that is currently being explored for use in different aspects of agriculture. So far, research on this area is limited to evaluating the phenotypical responses of plants to a high concentration of the NPs which is realistically not feasible in the actual environment. This research aims to investigate the molecular-level interactions between ZnO NPs and plants, together with another significant component of the environment, a fungal plant pathogen. Prior to studying these molecular-level interactions, the uptake of ZnO NPs in planta was validated using a fluorescent zinc ion sensor, Zinpyr-1 and a zinc ion chelator, TPEN in confocal laser scanning microscopy (CLSM) and Transmission Electron Microscopy (TEM). Phenotypical effects were studied in soybean plants exposed to environmentally relevant concentrations of ZnO NPs and bioaccumulation of zinc was studied in seeds of soybean and other soy products. The next phase of this research focused on investigating the physiological responses of plants exposed to ZnO NPs. This was achieved by elucidating the complete transcriptome of the plants using a Next Generation sequencing (NGS) platform, RNA seq. A significant part of this research emphasized on exploring the effects of ZnO NPs on host-pathogen interactions. The model monocot plant, barley was used in this study, together with a necrotrophic pathogen, Pyrenophora teres f. teres (Ptt). The barley line which was used, CI5791 is resistant to the disease Net Form Net Blotch (NFNB), caused by Ptt. Rapid responses of plants to ZnO NPs were observed that subsided at the later time-points, whereas the heightened responses to the pathogen alone (P) and combined application (ZnO NP + P) persisted. Exposure to ZnO NPs also induced transcriptional reprogramming in the Ptt inoculated plant that resulted in compromised immunity in the otherwise resistant barley, due to the persistence of salicylic acid (SA)-related genes. In ZnO NP-exposed Arabidopsis thaliana, the effects were contradictory. From the barley and Arabidopsis expression data, it could be concluded that both species react differently to ZnO NPs, giving a glimpse of the differential responses that ZnO NPs may elicit in different plant species.USDA-NIFA
National Science Foundation (NSF)
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Lyimo, Germana Vincent. "Green synthesised Zinc Oxide Nanoparticles and their antifungal effect on Candida albicans Biofilms." University of Western Cape, 2020. http://hdl.handle.net/11394/7606.
Full textAbstract:
Magister Scientiae Dentium - MSc(Dent)Candida albicans is a clinical fungal isolate that is most frequently isolated from different host niches, and is implicated in the pathogenesis of several fungal infections, including oral candidiasis. The pathogenesis and antifungal resistance mechanisms of Candida species are complex and involve several pathways and genes. Oral candidiasis incidence rates are rapidly increasing, and the increase in resistance to conventional antifungals has led to the need to develop innocuous and more efficacious treatment modalities. The purpose of this study was to explore a single pot process for phytosynthesis of zinc oxide nanoparticles (GZnO NPs) and to assess their antifungal potential.
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Liu, Yang Li Men`gshi. "Study of antimicrobial activity and mechanism of zinc oxide nanoparticles against foodborne pathogens." Diss., Columbia, Mo. : University of Missouri-Columbia, 2009. http://hdl.handle.net/10355/6718.
Full textAbstract:
The entire thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file; a non-technical public abstract appears in the public.pdf file. Title from PDF of title page (University of Missouri--Columbia, viewed on March 23, 2010). Thesis advisor: Dr. Mengshi Lin. Includes bibliographical references.
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Pokhrel, Lok R., Brajesh Dubey, and Phillip R. Scheuerman. "Potential Developmental Toxicity of Silver and Zinc Oxide Nanoparticles to the Terrestrial Plants." Digital Commons @ East Tennessee State University, 2012. https://dc.etsu.edu/etsu-works/2952.
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Saptarshi, Shruti R. "Nanoparticle-protein corona formation and immunotoxicity of zinc oxide nanoparticles." Thesis, 2015. https://researchonline.jcu.edu.au/43787/1/43787-saptarshi-2015-thesis.pdf.
Full textAbstract:
Engineered zinc oxide nanoparticles (ZnO-NPs) offer versatility and properties that have a vast array of applications, and are widely used in cosmetics and sunscreens, because of their excellent UV filtering properties and aesthetic appeal. Interestingly, despite high production volumes and a broad application base, there is always a possibility of unintentional side-effects of NPs due to their increased reactivity at the biological level. Bio-reactivity of nanoparticles can be influenced by their physical characteristics such as size, surface coating and propensity to interact with proteins. The main objective of this PhD thesis was to investigate and characterise the phenomenon of protein corona formation on ZnO NP surface in a protein rich environment such as cell culture medium, evaluate the nanotoxicological potential of these NPs using in vitro as well as in vivo test systems and furthermore relate this information to their physico-chemical properties.
NP-protein interactions as reviewed in chapter II can be affected by the primary size and agglomeration state of the NPs. Therefore accurate characterisation of the NP physico-chemical properties is vital. ZnO NP solutions of three different sizes, 30 nm, 80 nm and 200 nm in pristine and surfactant dispersed forms were characterised for their size, agglomeration and solubility in chapter III. Analytical disc centrifugation technique was chosen to determine the agglomeration state of the ZnO NPs in a protein enriched cell culture medium. The pristine ZnO NPs formed micron-sized agglomerates whereas; surfactant-treated material remained relatively monodispersed. Extracellular dissolution of ZnO NPs has been shown to affect their cellular interaction. Using ICP-AES technique I confirmed that the ZnO NPs used in this study have a low dissolution rate in cell culture medium.
Chapter IV of this thesis explored the identification and characterisation of the proteins adsorbed on the surface of ZnO NPs upon interaction with protein fortified cell culture medium which forms the foundation of good nanotoxicological studies. NPs due to their unique sizes interact with protein molecules, forming the NP-protein corona (NP-PC) that may influence their bio-reactivity. The adsorption of proteins on ZnO NP surface was instantaneous and did not change with time. Subsequent mass spectrometric analysis of the isolated ZnO NP-PC revealed enrichment of proteins with definite physiological roles, on the two 30 nm ZnO NP surfaces analysed. Interestingly, pristine and surfactant-dispersed ZnO-NP formed specific protein coronas by selectively binding low molecular weight proteins, derived from larger proteins such as haemoglobin, histones, fibrinogen etc. Interestingly, ZnO-NP induced protein conformational change depended on the type of protein interacting with the NP surface. ZnO NPs were also able to retain their BSA pre-coating after transfer into a new solution of cell lysate proteins, which demonstrated for the first time that, the protein corona formation of ZnO NPs is a constantly evolving process. Flow cytometry based side and forward scatter (measures of cytoplasmic granularity and size of cells respectively) analysis of human lung epithelial cells (A549) was largely affected when they were exposed to the 30 nm ZnO NP solutions dispersed in the absence of proteins vs 10% fetal bovine serum proteins. Furthermore, ZnO NP induced cytotoxicity at 100 μg/mL concentration was also significantly affected in the presence of increasing amounts of FBS proteins (10 or 40%). This clearly demonstrated that the adsorbed protein layer onto the NP surface influenced ZnO NP uptake and cytotoxicity.
Zinc oxide nanoparticles have been classified in to the category of highly reactive metal oxide NPs as outlined in chapter V. Exposure to ZnO NPs can occur not only via skin contact, but also via inhalation especially in the manufacturing sector and is an important occupational safety concern. Chapter VI of this thesis evaluates the capacity ZnO NPs in eliciting cytotoxicity and immunomodulation in human lung epithelial (A549) cells. The A549 cells represent the type II alveolar cells which form the first line of defence against inhaled particulate matter and were therefore chosen as suitable targets for this study. Direct exposure to ZnO NPs resulted in a size and dose-dependent cytotoxic response, indicated by decreased cell viability and increased lactate dehydrogenase release. DAPI staining of nuclear material in exposed cells revealed that cytotoxicity was mediated by apoptosis. The main objective of this section was to further investigate the immunomodulatory potential of ZnO NPS at the sub-cytotoxic level. The sub-cytotoxic ZnO NP concentration (20 μg/mL) induced significant up-regulation of the key pro-inflammatory cytokine IL-8 and redox stress marker heme oxygenase-1 at the mRNA level along with increased release of IL-8 protein in a time-dependent manner. The low doses of ZnO NPs also demonstrated that the increased expression of IL-8 involved transcriptional activation of NFκB, followed by further stabilisation of IL-8 mRNA by p38 mitogen activated protein kinase pathway. Pre-treatment of A549 cells with the sulfhydryl antioxidant Nacetyl cysteine resulted in significant reduction in the up-regulation of inflammatory markers, thus confirming the role of reactive oxygen species in the observed reactivity. This data highlights the inflammatory potential of ZnO NP at sub-cytotoxic doses, possibly due to a redox imbalance generated in exposed cells. This chapter increases our understanding of the kinetics and mechanisms underlying the observed immune modulatory and cytotoxic effects of ZnO NPs.
The last module of this thesis, chapter VII analysed the reactivity of ZnO NPs-in vivo system. 30nm ZnO NPs not only demonstrated differential protein binding but also higher cytotoxicity and pro-inflammatory potential in vitro and were consequently selected for the murine model investigation. Intranasal instillation of ZnO NPs and their ability to cause systemic inflammatory response in an acute high-dosage exposure animal model has not been investigated before. In this study, administration of a single dose (5 mg/kg BW) of either 30nm ZnO NP solutions resulted in substantial inflammatory infiltration into the alveoli and peri-bronchial regions of exposed mice. 24hr after the NP challenge. Significant up-regulation of eotaxin mRNA was also observed in the lung tissue obtained from mice treated with pristine 30nm. Cytokine profiling of pooled mouse serum from each NP treated or control mice groups revealed the presence of pro-inflammatory chemokines such as MCP-1, RANTES, IP-10 which known to recruit leukocytes to inflammatory sites. The preliminary results of the in vivo study highlight the inflammatory potential of inhaled ZnO NPs.
In conclusion, this thesis describes the dynamic interaction of serum proteins with sunscreen ZnO NPs and their strong immunomodulatory potential at a sub-cytotoxic dose. Moreover exposure to a single but relatively high dose of ZnO NPs via intranasal instillation causes acute pulmonary inflammatory reactions in vivo. The outcome of this thesis assists towards development of bio-compatible ZnO NPs for future use.