Página 1 dos resultados de 6686 itens digitais encontrados em 0.013 segundos

Oxygen reduction and diffusion in electroactive nanostructured membranes (ENM) using a layer-by-layer dendrimer-gold nanoparticle approach

Crespilho, Frank N.; Nart, Francisco C.; Oliveira Jr., Osvaldo N.; Brett, Christopher M. A.
Fonte: Universidade de Coimbra Publicador: Universidade de Coimbra
Tipo: Artigo de Revista Científica Formato: aplication/PDF
Português
Relevância na Pesquisa
350.76523%
The fabrication of an electroactive nanostructured membrane (ENM) for oxygen reduction, made of layer-by-layer (LbL) films comprising Au nanoparticle-containing amine-terminated G4 PAMAM dendrimer alternated with poly(vinylsulfonic acid) (PVS) layers is reported. Electrochemical impedance spectroscopy and cyclic voltammetry show that electrodes with PVS/PAMAM-Au multiple bilayers are efficient for oxygen reduction and diffusion. A linear increase of oxygen reduction current occurs for up to 3 bilayers, with no further significant increase occurring for more than 3 bilayers. The 3-bilayer PVS/PAMAM-Au electrode, as an Au-ENM, is an attractive new system with potential for building diverse electrocatalytic devices with high molecular control.; http://www.sciencedirect.com/science/article/B6TG0-4MYMFYF-9/1/8855a87cb0ee008f2c3da593edfeec53

Morphology of cobalt ferrite nanoparticle-polyelectrolyte multilayered nanocomposites

ALCANTARA, G. B.; PATERNO, L. G.; Fonseca, Fernando Josepetti; MORAIS, P. C.; SOLER, M. A. G.
Fonte: ELSEVIER SCIENCE BV Publicador: ELSEVIER SCIENCE BV
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
350.76523%
Novel magnetic nanocomposite films with controlled morphology were produced via the electrostatic layer-by-layer assembly of cationic CoFe(2)O(4) nanoparticles and anionic poly(3,4-ethylenedioxy thiophene)/poly(styrene sulfonic acid) (PEDOT:PSS) complex. The electrostatic interaction between nanoparticle and the polyelectrolyte complex ensured a stepwise growth of the nanocomposite film with virtually identical amounts of materials being adsorbed at each deposition cycle as observed by UV-vis spectroscopy. AFM images acquired under the tapping mode revealed a globular morphology with dense and continuous layers of nanoparticles with voids being filled with polymeric material. (C) 2010 Elsevier B.V. All rights reserved.

Desenvolvimento de um gerador de nanopartículas e caracterização de nanopartículas de cobalto; Development of a nanoparticle generator and caracterization of cobalt nanoparticles

Landi, Gabriel Teixeira
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 26/03/2009 Português
Relevância na Pesquisa
350.76523%
Neste trabalho, desenvolvemos um gerador de nanopartículas (NPs) como uma adaptação para um sistema de magnetron sputtering. Com ele, somos capazes de produzir NPs de materiais diversos e codepositá-las em matrizes dielétricas ou metálicas. A adaptação consiste em incluir uma região de alta pressão relativa de Ar no caminho do vapor atômico removido do alvo. A aglomeração ocorre termodinamicamente devido a diminuição da energia cinética após colisões com o gás. Desenvolvemos também, uma metodologia para colimar o fluxo de NPs dentro da região de alta pressão. A deposição é feita no substrato na forma de uma mancha com alguns milímetros de diâmetro e o tempo de preparação da amostra é significativamente curto. Desenvolvemos um modelo fenomenológico para explicar a condensação e a colimação do nosso sistema. Este, apesar de não sofisticado, explica bem ambos os fenômenos e consegue prever o diâmetro das nanopartículas para certas condições. Em paralelo ao desenvolvimento, produzimos e caracterizamos nanopartículas de cobalto. Da caracterização morfológica, através de microscopia eletrônica, concluímos que as NPs produzidas tem diâmetros médios de 10 nm com uma dispersão de 13 %. Através de análises de retro espalhamento Rutherford estudamos a distribuição do material sobre o substrato e observamos que este segue uma distribuição Gaussiana de espessuras. Além disso...

Nanoparticle-coated organic-inorganic microparticles : experimental design and gastrointestinal tolerance evaluation

Beck, Ruy Carlos Ruver; Haas, Sandra Elisa; Guterres, Silvia Stanisçuaski; Ré, Maria Inês; Benvenutti, Edilson Valmir; Pohlmann, Adriana Raffin
Fonte: Universidade Federal do Rio Grande do Sul Publicador: Universidade Federal do Rio Grande do Sul
Tipo: Artigo de Revista Científica Formato: application/pdf
Português
Relevância na Pesquisa
354.67027%
The influences of the spray-drying parameters and the type of nanoparticles (nanocapsules or nanospheres) on the characteristics of nanoparticle-coated diclofenac-loaded microparticles were investigated by using a factorial design 32. Gastrointestinal tolerance following oral administration in rats was evaluated. Formulations were selected considering the best yields, the best encapsulation efficiencies and the lowest water contents, presenting surfaces completely coated by nanostructures and a decrease in the surface areas in relation to the uncoated core. In vitro drug release demonstrated the influence of the nanoparticle-coating on the dissolution profiles of diclofenac. Nanocapsule-coated microparticles presented a protective effect on the gastrointestinal mucosa.

Auto-organização de nanoparticulas utilizando padrões formados por transição de molhabilidade; Nanoparticle self-assembly using patterns formed by dewetting

Camila Alves de Rezende
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 02/03/2007 Português
Relevância na Pesquisa
361.80117%
Neste trabalho, estudou-se um método original para auto-organizar nanopartículas de sílica e de ouro utilizando padrões formados no processo de transição de molhabilidade de filmes aquosos contendo poli (N-isopropilacrilamida) (PNIPAM) e o surfactante dodecil sulfato de sódio (SDS). A transição de molhabilidade é um processo em que a superfície livre de um filme líquido fino inicialmente uniforme torna-se instável e se deforma levando à ruptura do mesmo e à formação de estruturas micro ou nanométricas sobre o substrato. Este estudo mostra que essas estruturas podem ser utilizadas para induzir a auto-organização de nanopartículas em padrões complexos. Soluções poliméricas e dispersões contendo nanopartículas são depositadas sobre substratos sólidos e analisadas, após a secagem, por microscopia eletrônica de transmissão (TEM), microscopia eletrônica de varredura (SEM) e microscopia de força atômica (AFM). A técnica de refletância de nêutrons foi utilizada para obter informações quantitativas sobre a adsorção de nanopartículas na interface e avaliar os efeitos da interação entre as nanopartículas e superfícies hidrofílicas e hidrofóbicas. Dois fatores principais influenciam os padrões formados: a hidrofilicidade do substrato e as interações partícula-substrato. Os filmes depositados sobre superfícies hidrofílicas (mica) espalham-se espontaneamente e secam formando padrões e estruturas auto-organizadas que dependem da densidade de carga sobre o polímero e da temperatura. Em baixa temperatura e densidade de carga...

Effect of ferromagnetic nanoparticle on dyes biodegradation

Apostol, Laura; Pereira, Luciana; Pereira, Raquel; Alves, M. M.; Gavrilescu, M.
Fonte: Universidade do Minho Publicador: Universidade do Minho
Tipo: Artigo de Revista Científica
Publicado em //2011 Português
Relevância na Pesquisa
350.76523%
In this study the biodecolourisation of two dyes, a xanthene dye, Erythrosine B (Ery B) and an azo dye, Reactive Red 51 (RR120), was investigated colourdecolourisationunder batch anaerobic conditions by using non - acclimated anaerobic granular sludge. The effect of ferromagnetic nanoparticle (FN) (as adsorbent or mediator) on dyes removal was experienced.

Nanoparticle-coated organic-inorganic microparticles: experimental design and gastrointestinal tolerance evaluation

Beck,Ruy Carlos R.; Haas,Sandra Elisa; Guterres,Silvia Stanisçuaski; Ré,Maria Inês; Benvenutti,Edilson V.; Pohlmann,Adriana Raffin
Fonte: Sociedade Brasileira de Química Publicador: Sociedade Brasileira de Química
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/10/2006 Português
Relevância na Pesquisa
354.67027%
The influences of the spray-drying parameters and the type of nanoparticles (nanocapsules or nanospheres) on the characteristics of nanoparticle-coated diclofenac-loaded microparticles were investigated by using a factorial design 3². Gastrointestinal tolerance following oral administration in rats was evaluated. Formulations were selected considering the best yields, the best encapsulation efficiencies and the lowest water contents, presenting surfaces completely coated by nanostructures and a decrease in the surface areas in relation to the uncoated core. In vitro drug release demonstrated the influence of the nanoparticle-coating on the dissolution profiles of diclofenac. Nanocapsule-coated microparticles presented a protective effect on the gastrointestinal mucosa.

Dynamic Magnetic Fields Remote-Control Apoptosis via Nanoparticle Rotation

Zhang, Enming; Kircher, Moritz F.; Koch, Martin; Eliasson, Lena; Goldberg, S. Nahum; Renström, Erik
Fonte: American Chemical Society Publicador: American Chemical Society
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
350.76523%
The ability to control the movement of nanoparticles remotely and with high precision would have far-reaching implications in many areas of nanotechnology. We have designed a unique dynamic magnetic field (DMF) generator that can induce rotational movements of superparamagnetic iron oxide nanoparticles (SPIONs). We examined whether the rotational nanoparticle movement could be used for remote induction of cell death by injuring lysosomal membrane structures. We further hypothesized that the shear forces created by the generation of oscillatory torques (incomplete rotation) of SPIONs bound to lysosomal membranes would cause membrane permeabilization, lead to extravasation of lysosomal contents into the cytoplasm, and induce apoptosis. To this end, we covalently conjugated SPIONs with antibodies targeting the lysosomal protein marker LAMP1 (LAMP1-SPION). Remote activation of slow rotation of LAMP1-SPIONs significantly improved the efficacy of cellular internalization of the nanoparticles. LAMP1-SPIONs then preferentially accumulated along the membrane in lysosomes in both rat insulinoma tumor cells and human pancreatic beta cells due to binding of LAMP1-SPIONs to endogenous LAMP1. Further activation of torques by the LAMP1-SPIONs bound to lysosomes resulted in rapid decrease in size and number of lysosomes...

Fabrication of Highly Ordered Nanoparticle Arrays Using Thin Porous Alumina Masks

Lei, Y.; Teo, L.W.; Yeong, K.S.; See, Y.H.; Chim, Wai Kin; Choi, Wee Kiong; Thong, J.T.L.
Fonte: MIT - Massachusetts Institute of Technology Publicador: MIT - Massachusetts Institute of Technology
Tipo: Artigo de Revista Científica Formato: 4395834 bytes; application/pdf
Português
Relevância na Pesquisa
360.67066%
Highly ordered nanoparticle arrays have been successfully fabricated by our group recently using ultra-thin porous alumina membranes as masks in the evaporation process. The sizes of the nanoparticles can be adjusted from 5-10 nm to 200 nm while the spacing between adjacent particles can also be adjusted from several nanometers to about twice the size of a nanoparticle. The configuration of the nanoparticles can be adjusted by changing the height of the alumina masks and the evaporation direction. Due to the high pore regularity and good controllability of the particle size and spacing, this method is useful for the ordered growth of nanocrystals. Different kinds of nanoparticle arrays have been prepared on silicon wafer including semiconductors (e.g., germanium) and metals (e.g., nickel). The germanium nanoparticle arrays have potential applications in memory devices while the nickel catalyst nanoparticle arrays can be used for the growth of ordered carbon nanotubes.; Singapore-MIT Alliance (SMA)

Nanoparticle toxicity and oxidative stress assessed through pulmonary cell models

Rushton, Erik K. ; Finkelstein, Jacob N.
Fonte: Universidade de Rochester Publicador: Universidade de Rochester
Tipo: Tese de Doutorado Formato: Number of Pages:xiv, 173 leaves
Português
Relevância na Pesquisa
354.67027%
Thesis (Ph. D.)--University of Rochester. School of Medicine & Dentistry. Dept. of Environmental Medicine, 2007. ; Nanomaterials are defined by the National Nanotechnology Initiative as those materials with at least one dimension less than 100 nanometers and possessing unique characteristics due to their small size. These unique properties are responsible for the dramatic growth in their proposed utilization in a multitude of new applications. With their increase in use and production comes the potential for increased human exposure to materials with poorly characterized toxicological profiles. Inhalation has been identified as one of the major routes of exposure for nanoparticles both occupationally and environmentally. Detailed modeling and experimental data reveal that nanoparticles are capable of being deposited deep within the pulmonary system in the alveolar regions. Particulate matter has long been recognized as a risk factor associated with both morbidity and mortality. Hypotheses about the effects reveal that reactive oxygen species (ROS) may play a role in associated toxicities associated with nanoparticles. The ROS have been demonstrated as being generated from the particle itself as intrinsic activity, or by the cell...

The Role of Response-metric in Nanoparticle Toxicology

Han, Xianglu ; Oberdorster, Gunter ; Finkelstein, Jacob N.
Fonte: Universidade de Rochester Publicador: Universidade de Rochester
Tipo: Tese de Doutorado
Português
Relevância na Pesquisa
350.76523%
Thesis (Ph.D.)--University of Rochester. School of Medicine and Dentistry. Dept. of Environmental Medicine, 2009.; With the increasing number and variety of NPs and the current dispute regarding the value of in vitro assays in predicting in vivo toxicity of NPs, there is an urgent need for developing and validating screening assays that work well for evaluating nanoparticle (NP) toxicity. To test the overall hypothesis that results of in vitro assays can be used to predict acute in vivo effects and to establish a hazard scale based on careful analysis of the dose-response curve using appropriate response metric, we evaluated the usefulness of several assays by adopting NP surface area as the dose metric and a response metric that is based on surface area. Several anatase TiO2 NPs (of sizes from 3 to 100 nm) were examined for this purpose. In addition to in vitro studies where a cell-free assay and several cellular assays based on a rat lung Type I epithelial cell line (R3/1) were used, we examined pulmonary inflammation or cytotoxicity related in vivo endpoints following exposure of rats to the NPs via intratracheal instillation. For the correlation studies, in vitro endpoints included ROS generation in a cell-free system, lactate dehydrogenase (LDH) release from R3/1 cells...

Failure mechanisms of nanoparticle reinforced metal matrix composite

Basak, A.; Pramanik, A.; Islam, M.
Fonte: Trans Tech Publications Ltd.; Switzerland Publicador: Trans Tech Publications Ltd.; Switzerland
Tipo: Conference paper
Publicado em //2013 Português
Relevância na Pesquisa
350.76523%
The quest for the advanced functional material of superior functionality for advanced structure is being driven in various fronts of engineering materials. One of such front is metal matrix composite (MMC) which has already been proven as one of the most productive field in that respect. With the advance of technology, now it is possible to reinforce the MMCs with nano-sized particles compared to conventional micron-sized ones. However, the addition of nanoparticle in the MMC to improve its mechanical properties is not unconditional. To achieve positive gain by adding nanoparticles in the MMCs, all the influencing factors should be taken into consideration. The present paper reviews the failure mechanisms of nanoparticles reinforced MMCs in light of its strengthening mechanisms.; A. K. Basak, A. Pramanik, and M. N. Islam

Life cycle indicator comparison of copper, silver, zinc and aluminum nanoparticle production through electric arc evaporation or chemical reduction

Slotte, M.; Metha, G.; Zevenhoven, R.
Fonte: Springer Publicador: Springer
Tipo: Artigo de Revista Científica
Publicado em //2015 Português
Relevância na Pesquisa
357.3156%
Ways to produce metallic nanoparticles and the scale-up of these processes have seen increased interest as the industrial application of nanoparticles continues to grow. Their feasibility from an environmental point of view can be assessed by means of life cycle analysis (LCA). In this work two methods of metallic nanoparticle production, by evaporation/condensation of metal using electrical arc discharge reactors or by chemical reduction of metal salts in aqueous solutions or dry solid/solid mixtures, are evaluated based on the life cycle indicators. The evaporation of metal using electrical discharge reactors is a method studied in the European Commission 7th Framework Program “BUONAPART-E.” The environmental impact of the two different nanoparticle production approaches is here compared for four metals: copper, silver, zinc and aluminum. The chemical routes of producing nanoparticles require several different chemicals and reactions, while the electrical discharge routes use electricity to evaporate metal in a reactor under inert atmosphere. The nanoparticle production processes were modeled using “SimaPro” LCA software. Data for both the chemical production routes and the arc routes were taken from the literature. The choice of the best route for the production of each metal is strongly dependent on the final yield of the metallic nanoparticles. The yields for the chemical processes are not reported in the open literature...

Engineering Nanoparticle-Protein Associations for Protein Crystal Nucleation and Nanoparticle Arrangement

Benoit, Denise
Fonte: Universidade Rice Publicador: Universidade Rice
Português
Relevância na Pesquisa
361.80117%
Engineering the nanoparticle - protein association offers a new way to form protein crystals as well as new approaches for arrangement of nanoparticles. Central to this control is the nanoparticle surface. By conjugating polymers on the surface with controlled molecular weights many properties of the nanoparticle can be changed including its size, stability in buffers and the association of proteins with its surface. Large molecular weight poly(ethylene glycol) (PEG) coatings allow for weak associations between proteins and nanoparticles. These interactions can lead to changes in how proteins crystallize. In particular, they decrease the time to nucleation and expand the range of conditions over which protein crystals form. Interestingly, when PEG chain lengths are too short then protein association is minimized and these effects are not observed. One important feature of protein crystals nucleated with nanoparticles is that the nanoparticles are incorporated into the crystals. What results are nanoparticles placed at well-defined distances in composite protein-nanoparticle crystals. Crystals on the size scale of 10 - 100 micrometers exhibit optical absorbance, fluorescence and super paramagnetic behavior derivative from the incorporated nanomaterials. The arrangement of nanoparticles into three dimensional arrays also gives rise to new and interesting physical and chemical properties...

Development and Application of Methods to Study Nanoparticle Diffusion Using Intensity Correlation Spectroscopy

Tcherniak, Alexei
Fonte: Universidade Rice Publicador: Universidade Rice
Português
Relevância na Pesquisa
359.22613%
The practical application of nanoparticles requires transitioning from well controlled experimental settings to highly variable "real-life" conditions. Understanding the resulting changes in the behavior and stability of nanoparticles is therefore of paramount importance. This thesis discusses the development and practical applications of tools to monitor the behavior of nanoparticles in real-time using intensity correlation spectroscopy techniques. I show how-correlation spectroscopy can be adapted to nanoparticle systems; and provide particular parameters and settings especially vital for heterogeneous systems. Oftentimes nanoparticles have to be labeled to be detected, which can complicate the system of study and can introduce systematic errors into the analysis. Intensity correlation spectroscopy was tested on dye-labeled magnetite nanocrystals. The fluorescence correlation spectroscopy results were surprisingly biased towards a low concentration of aggregates. Scattering and absorption cross-sections of gold nanoparticles are greatly enhanced near the plasmon resonance wavelength, providing strong intrinsic signals for directly visualizing nanoparticles. I show here how scattering and absorption scale with nanoparticle size; and how size heterogeneity within nanoparticle samples translates into the detected signals. One-photon luminescence of gold nanoparticles...

Bleach Imaged Plasmon Propagation (BlIPP) of Metallic Nanoparticle Waveguides

Solis, David
Fonte: Universidade Rice Publicador: Universidade Rice
Português
Relevância na Pesquisa
350.76523%
The high speed transfer of information in materials with dimensions below the sub-diffraction limit is essential for future technological developments. Metallic nanoparticle (NP) waveguides serve a unique role in efficient energy transfer in this size regime. Light may be confined to metallic structures and propagate along the surface of the waveguide via propagating plasmon waves known as surface plasmon polaritons (SPPs). Plasmon propagation of energy in metallic structures is not perfect however and damping losses from the waveguide material lead to a characteristic exponential decay in the plasmon near field intensity. This decay length is known as the propagation length and serves as an excellent metric to compare various waveguide materials and structures to one another at particular excitation wavelengths. This thesis presents recent work in the development of a novel measurement technique termed bleach imaged plasmon propagation (BlIPP). BlIPP uses the photobleaching property of fluorophores and far field fluorescence microscopy to probe the near-field intensity of propagating plasmons and determine the propagation length. The experimental setup, image analysis, conditions, and application of BlIPP are developed within this thesis and an in depth review of the 1-photon photobleaching mechanism is also investigated. The BlIPP method is used to investigate long plasmon propagation lengths along straight chains of tightly packed Au NPs through the coupling of light to sub-radiant propagating modes...

Theoretical and Experimental Analysis of Nanoparticle-Nanoparticle and Nanoparticle-Surface Interactions and Their Role in Defining Nanoparticle Stability and Mobility

Cardoso Zies, Camila
Fonte: Universidade Rice Publicador: Universidade Rice
Português
Relevância na Pesquisa
362.71%
The use of nanocrystals in a number of technological areas, such as in environmental remediation, oil fields illumination or even in situ cancer treatment, creates a challenge to the complete understanding of the transport of these nanoparticles in various types of porous media - soil, sandstone matrixes or tissue material, respectively. Even though nanocrystals present breakthrough possibilities in these various applications, their feasible use would be compromised without reaching the area of interest. As the library of nanoparticles is growing at a considerable rate over time, it is of great importance that efficient screening methods are developed and used routinely to assess their mobility. The central challenge of this work was to fully understand the phenomena behind nanoparticle interactions with other nanoparticles and with surfaces and, based on this knowledge, to characterize mobility and thus nanoparticle transport in different environments. The core of this analysis was explored outside neutral situations, i.e. nanoparticles in aqueous suspensions. We looked closely into how the mobility behavior of nanoparticles was affected by the influence of various chemistries, such as a broad range of ionic strength, different surrounding ionic valences...

Nanoparticle-in-Microparticle Delivery Systems (NiMDS): Production, Administration Routes and Clinical Potential

Imperiale, Julieta Celeste; Sosnik, Alejandro Dario
Fonte: American Scientific Publishers Publicador: American Scientific Publishers
Tipo: info:eu-repo/semantics/article; info:ar-repo/semantics/artículo; info:eu-repo/semantics/publishedVersion Formato: application/pdf
Português
Relevância na Pesquisa
354.67027%
Microparticles (MPs) and nanoparticles (NPs) have received considerable attention for the design of drug delivery systems (DDS) with unique properties owing to the increased surface area and the ability to fine tune the release process. More recently, a new type of DDS that capitalize on the advantages of both NPs and MPs has been introduced. Nanoparticle-in-Microparticle Delivery Systems (NiMDS) comprise the encapsulation of NPs within MPs and lead to features that are unique and different from those of the individual components. These technology platforms can be produced employing from conventional to more sophisticated methodologies and equipment and they are administered by different routes such as oral, pulmonary or even parenteral. Moreover, if designed appropriately, they can (i) protect drug payloads and prevent physical and chemical instability phenomena in the biological environment, (ii) improve the release profile of the encapsulated agent, (iii) reduce or eliminate the burst effect and (iv) target specific cells, tissues and organs. The present review overviews the different approaches to produce NiMDS and discusses their potential implementation in clinics.; Microparticles (MPs) and nanoparticles (NPs) have received considerable attention for the design of drug delivery systems (DDS) with unique properties owing to the increased surface area and the ability to fine tune the release process. More recently...

Atomic-scale and three-dimensional transmission electron microscopy of nanoparticle morphology

Leary, Rowan Kendall
Fonte: University of Cambridge; Department of Materials Science and Metallurgy Publicador: University of Cambridge; Department of Materials Science and Metallurgy
Tipo: Thesis; doctoral; PhD
Português
Relevância na Pesquisa
354.67027%
The burgeoning field of nanotechnology motivates comprehensive elucidation of nanoscale materials. This thesis addresses transmission electron microscope characterisation of nanoparticle morphology, concerning specifically the crystal- lographic status of novel intermetallic GaPd2 nanocatalysts and advancement of electron tomographic methods for high-fidelity three-dimensional analysis. Going beyond preceding analyses, high-resolution annular dark-field imaging is used to verify successful nano-sizing of the intermetallic compound GaPd2. It also reveals catalytically significant and crystallographically intriguing deviations from the bulk crystal structure. So-called ?non-crystallographic? five-fold twinned nanoparticles are observed, adding a new perspective in the long standing debate over how such morphologies may be achieved. The morphological complexity of the GaPd2 nanocatalysts, and many cognate nanoparticle systems, demands fully three-dimensional analysis. It is illustrated how image processing techniques applied to electron tomography reconstructions can facilitate more facile and objective quantitative analysis (?nano-metrology?). However, the fidelity of the analysis is limited ultimately by artefacts in the tomographic reconstruction. Compressed sensing...

Mechanisms of Silver Nanoparticle Toxicity in Laboratory Suspensions and Complex Environmental Media in Caenorhabditis Elegans

Yang, Xinyu
Fonte: Universidade Duke Publicador: Universidade Duke
Tipo: Dissertação
Publicado em //2014 Português
Relevância na Pesquisa
350.76523%

The rapidly increasing use of silver nanoparticles (Ag NPs) in consumer products and medical applications has raised ecological and human health concerns. Significant progress has been made in understanding the toxicity of silver nanoparticles (Ag NPs) under carefully controlled laboratory conditions. The goals of this dissertation were to investigate the mechanism of Ag NP toxicity under both laboratory conditions and environmental backgrounds, using Caenorhabditis elegans (C. elegans) as a model system. A key question for addressing these concerns is whether Ag NP toxicity is mechanistically unique to nanoparticulate silver or if it is a result of the release of silver ions. Ag NPs are produced in a large variety of monomer sizes and coatings, and since their physicochemical behavior depends on the media composition, it is important to understand how these variables modulate toxicity.

In order to test the hypothesis of a particle-specific effect, multiple techniques were used, including analytical chemistry, pharmacological rescue, and genetic analysis. Results suggested that dissolution was important for all tested Ag NPs and oxidative stress (a particle-specific effect) was important only for some Ag NPs...