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Stamplecoskie, Kevin. "Silver Nanoparticle Controlled Synthesis and Implications in Spectroscopy, Biomedical and Optoelectronics Applications." Thèse, Université d'Ottawa / University of Ottawa, 2013. http://hdl.handle.net/10393/24164.
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This thesis describes the photochemical synthesis of silver nano particles, several ways to make these particles as well as control the size and shape of the colloidal particles. Understanding the primary reactions in photochemical nanoparticle formation has lead to important contributions to the overall mechanism of metal nanoparticle synthesis. The size and shape control of the particles is shown to have important implications for the Raman spectrum of surface bound molecules. The particles have also been used in antibacterial properties where it was shown that silver nanoparticles are more antibacterial than the corresponding silver cation, while remaining non-toxic to several common cell lines. The particles were also shown to have some interesting properties that can be exploited in lithography and optoelectronics.
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Liu, Xiaojun. "Dendrimer templated silica networks: synthesis, characterization and application in silver nanoparticle construction." Thesis, McGill University, 2008. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=19287.
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In this thesis, 3,5-Dihydroxybenzylalcohol (DHBA) based dendrimers of generations 0-5 (G0-G5) were used as templates in the construction of hybrid silica networks via a simple sol-gel condensation methodology. Two types silane reagent Si(NMe2)4 and ClSi(NEt2)3 were used to react with the periphery situated hydroxyl groups in these dendrimers, followed by hydrolysis and polycondensation, leading to highly cross-linked, porous silica based hybrid materials. The removal of dendrimer templates was achieved via in situ or acid hydrolysis. In situ removal of dendrimer templates was carried out as the use of ClSi(NEt2)3, while in the case of Si(NMe2)4, the dendrimers were subsequently removed upon treatment with HCl. The detailed studies of silica network structures and surface morphology before and after removal of dendrimers and salt were carried out using techniques including solid-state NMR, FT-IR spectroscopies, transmission electron microscopy (TEM), and nitrogen adsorption (BET), showing that the aggregation of DHBA based dendrimers controls the evolution of the network structure and their pore sizes. The resulting dendrimer templated silica networks were found to be water repellant on their surfaces with a hydrophilic interior. The application of silica networks synthesized using DHBA based dendrimers as templates was successfully demonstrated in tailoring the preparation of silver metal nanoparticles. Due to the internal and external environment of the silica networks, G1-3 silica networks wet slowly with aqueous silver acetate, resulting in chemisorption of silver ions with internal silanol groups, and followed by the growth of silver oxide nanoparticles as higher local water content around silver ions inside the networks. G<br>Au cours de ce master, des réseaux hybrides de silice ont été synthétisés par simple condensation sol-gel et à l'aide de dendrimères de générations 0 à 5 (G0-G5), dont le squelette a été formé à partir de l'alcool 3,5-dihydroxybenzylique. Deux types de réactifs, Si(NMe2)4 et ClSi(NEt2)3, ont été employés de manière à réagir avec les groupements hydroxyles terminaux de ces dendrimères. Puis, par hydrolyse et polycondensation, des réseaux de silice très réticulés et poreux ont pu être produits. La suppression des dendrimères a été réalisée in situ ou par hydrolyse acide.En effet, l'élimination des dendrimères a lieu dans le cas du réactif ClSi(NEt2)3, tandis qu'avec Si(NMe2)4, un traitement avec l'acide chlorhydrique HCl a été nécessaire. Une étude détaillée des réseaux de silice, c'est-à-dire leur morphologie avant et après l'élimination des dendrimères et les sels, a été menée en utilisant diverses techniques telles que la RMN à l'état solide, la spectroscopie FT-IR, la microscopie électronique à transmission (TEM) et la technique d'adsorption d'azote (BET). Les résultats de la technique BET ont par ailleurs montré que l'agrégation des dendrimères précédant la synthèse sol-gel contrôle l'évolution de la structure du réseau et la taille de leurs pores. De plus, ces réseaux de silice ont été observés comme rejetant les molécules d'eau à leur surface et étant constitué d'un intérieur hydrophile. Enfin, il a été démontré avec succès que ces réseaux de silice pouvaient être appliqués à la préparation de nanoparticules d'argent. Dû à leur environnement hydrophobe, les réseaux de silice G1-3 réagissent très lentement avec l'acétate d'argent aqueux,
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Menezes, Roseline. "Synthesis, characterization and antibacterial activity of silver embedded silica nanoparticle/nanogel formulation." Master's thesis, University of Central Florida, 2011. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/4804.
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The antibacterial property of silver (Ag) has been known since ancient time. It is reported in the literature that silver nanoparticles (AgNPs) exhibit improved antibacterial properties in comparison to silver ions of equivalent metallic Ag concentration. Such improvement in antibacterial activities is due to the high surface area to volume ratio of AgNPs (which facilitates interaction with the bacterial cells), increased release of silver ions and direct intra-cellular uptake of AgNPs leading to localized release of Ag ions. To date, over 300 consumer products containing AgNPs are available in the market and the inventory is rapidly expanding. The antibacterial efficacy is related to the loading of AgNPs (which controls availability of active Ag ions). It is perhaps challenging to increase AgNPs loading in consumer products without compromising its aesthetic appearance. AgNPs exhibit yellow-brown color due to strong Surface Plasmon Resonance (SPR) absorption; and therefore, it is expected that an increase in loading would change the color of AgNP-containing materials. For applications, such as creating a fast-acting touch-safe surface, higher loading of AgNPs is desirable. It is also desirable to obtain a non-color forming surface. To meet the demands of desirable higher loading of AgNPs and non-color forming surface, the objective of this study is to minimize SPR by engineering Ag containing nanomaterials for potential fast-acting spray-based applications. Within this thesis several reports have been made including synthesis, characterization and antibacterial properties of Ag-loaded silica nanoparticle/nanogel (AgSiNP/NG) material containing nanoformulations. The effects of nanoformulation pH and metallic Ag content on the SPR absorption and antibacterial properties have been studied. The AgSiNP/NG materials were synthesized using silica sol-gel technique at room temperature in water.; The color formation of the AgSiNP/NG material was found to be dependent on silver ion loading (15.4 wt% and 42.3 wt %) as well as on the pH (pH 4.0 and pH 7.0). A number of material characterization techniques such as HRTEM, SEM and AFM were used to characterize particle size, crystalline and surface morphology in dry state. Dynamic light scattering (DLS) technique was used to characterize particle size and size distribution in solution. UV-VIS spectroscopy technique was applied to characterize Ag ions and AgNPs in the AgSiNP/NG material. Antibacterial studies were conducted against gram negative E.coli and gram positive B.subtilis and S.aureus. A number of qualitative (well diffusion, BacLight[Trademark] live-dead viability) and quantitative (turbidity, resazurin viability) assays were used for antibacterial studies. It was observed that lower pH and low Ag loading minimized SPR absorption, resulting in no yellow-brown color formation. The HRTEM confirmed the formation of ~5-25 nm size highly crystalline AgNPs which were coated with dielectric silica layer (silica gel). AFM, SEM and DLS studies confirmed formation of AgSiNPs in the range between 100 nm-200 nm. The AgSiNP/NG material was effective against both gram-negative and gram-positive bacteria. Based on this research it is suggested that by coating AgNPs with a dielectric material (such as silica); it is possible to suppress SPR absorption.<br>ID: 031001357; System requirements: World Wide Web browser and PDF reader.; Mode of access: World Wide Web.; Title from PDF title page (viewed May 3, 2013).; Thesis (M.S.)--University of Central Florida, 2011.; Includes bibliographical references (p. 74-79).<br>M.S.<br>Masters<br>Molecular Biology and Micro<br>Medicine<br>Biotechnology
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Otari, S. V., R. M. Patil, S. J. Ghosh, and S. H. Pawar. "Substrate Dependant Microbial Synthesis of Silver Nanoparticle and its Application as Antimicrobial Agent." Thesis, Sumy State University, 2012. http://essuir.sumdu.edu.ua/handle/123456789/34824.
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Microbial synthesis of nanoparticles is a green chemistry approach that interconnects nanotechnology
and microbial biotechnology. In this present study, synthesis of silver nanoparticles (AgNPs) has been
demonstrated using a metabolically versatile actinobacteria Rhodococcus sp. by reducing aqueous silver nitrate. The AgNPs were characterized by Ultraviolet–Visible (UV – vis) Spectrometer, Scanning Electron
Microscopy (SEM), Energy Dispersive X-ray Analysis (EDAX), Dynamic Light Scattering (DLS), Selected
Area Diffraction Pattern (SAED) and Transmission Electron Microscopy (TEM). The TEM showed spherical particles with an average size of 10 nm. The SAED pattern showed the characteristic Bragg peaks of
(111), (200), (220) and (311) facets of the face centered cubic (fcc) silver nanoparticles and confirmed that
these nanoparticles are crystalline in nature.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/34824
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Lukman, Audra Indrayani. "Biogenic Synthesis of Ag and Au Nanoparticles Using Aqueous Seed Exudates." Thesis, The University of Sydney, 2013. http://hdl.handle.net/2123/10262.
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This thesis focuses on the synthesis of silver (Ag) and gold (Au) nanoparticles (NPs) via direct bio-reduction of the metal ions under non-photomediated conditions by exudates from leguminous seeds of Medicago sativa and Lens culinaris. At [Ag+] or [Au3+] = 0.01 M and 30°C, the products prepared with the corresponding crude M. sativa and L. culinaris seed exudates exhibited the characteristic surface plasmon resonance bands of the metallic NPs in the UV-visible spectra at around 462 nm and 567 nm, respectively. As determined from the evolution of these bands, Ag and Au NP formations reached completion in <135 min and <60 min, respectively. Further studies by X-ray techniques and selected area electron diffraction corroborated that the NPs were zero-valent with face-centered cubic crystal structure. M. sativa seed exudate-synthesized Ag NPs were predominantly spherical ranging between 5-51 nm in diameter, whereas L. culinaris seed exudate synthesized-Au nanocrystals were comprised single crystalline plates (0.154 -1.39 micron in edge length), nanotriangles (10-84 nm in edge length) and pseudo-spherical NPs (7-77 nm in diameter). In general, average particle size increased with increasing pre-dilution of seed exudates (i.e. decreasing amount of exudates). With M. sativa reduced-Ag NPs, flower-like particle clusters (mean size = 104 nm) were observed on treatment at [Ag+] = 0.1 M. Regulation of the biochemical composition by pre-dilution of the exudate induced the formation of single-crystalline Ag nanoplates, forming hexagonal particles and nanotriangles with edge lengths of 86–108 nm, but only when the reaction was conducted above 27C, while pH adjustment to 11 resulted in monodisperse Ag NPs with an average size of 12 nm. However, no reaction took place at pH 2. With L. culinaris reduced-Au NPs, seed exudate pre-dilution promoted spiral growth on the (111) plane of hexagonal Au nanoplates and triangular Au nanoplates formed at pH 2 and small quasi spheres at pH 11.
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Cinar, Simge. "Synthesis Of Silver Nanoparticles And Cable Like Structures Through Coaxial Electrospinning." Master's thesis, METU, 2009. http://etd.lib.metu.edu.tr/upload/2/12611472/index.pdf.
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The aim of this study is to demonstrate the possibility of production of nanocables as an alternative to the other one dimensional metal/polymer composite structures like nanowires and nanorods. There is no certain definition of nanocables<br>however they could be considered as assemblies of nanowires. Nanocable structure can be defined as a core-shell structure formed by a polymeric shell and a metal core that runs continuously within this shell. To produce nanocables, two main steps were carried out. Firstly, monodispersed silver metal nanoparticles to be aligned within the cable core were produced. Investigations on reduction reactions in the presence of strong and weak reducing agents and different capping agents revealed the importance of the kinetics of reduction in the production of monodispersed nanoparticles. Use of capping agents to give a positive reduction potential, resulted in the slow reduction rates that was critical for fine tuning of the final particle sizes between 1-10 nm. Hydrazine hydrate and oleylamine/ oleic acid systems were used as strong and weak reducing agents, respectively. By using weak reducing agent, monodisperse spherical silver nanoparticles with the diameter of 2.7 nm were produced. It was shown that particles with controlled diameter and size distribution can be obtained by tuning the system parameters. Secondly, particles produced as such were electrospun within the core of the polymer nanofibers and long continuous nanocables were produced. Polyvinyl pyrrolidone and polycaprolactone were used in shell part of nanocables. Transmission electron microscopy (TEM), scanning electron microscopy (SEM), photon correlation spectroscopy (PCS), X-ray diffraction (XRD) and surface plasmon resonance spectroscopy (SPR) analyses were carried out in order to understand the mechanism by which the nanoparticles were reduced and for further characterization of the product.
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McNamara, Nicholas D. "Sonochemical Synthesis and Characterization of Metal Nanoparticle-Decorated Carbon Supports." University of Dayton / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1311690542.
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Maleszewski, Adam A. "The Functionalization and Characterization of Adherent Carbon Nanotubes with Silver Nanoparticles for Biological Applications." Wright State University / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=wright1310428619.
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Keskin, Selda. "Synthesis And Characterization Of Copolymers Of Diisocyanates And Dialcohol." Phd thesis, METU, 2008. http://etd.lib.metu.edu.tr/upload/3/12609995/index.pdf.
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This study was aimed to synthesize low molecular weight hydroxyl terminated polyurethane acrylate polymers that can be used in biomedical applications. Acrylate end capping via inter-esterification reaction was successfully achieved with the methacryloyl chloride addition to the hydroxyl ends of the polyurethane at low temperatures. Isocyanate terminated polyurethane acrylates were also synthesized for the sake of comparison. TDI, HDI and MDI were used as diisocyanates for urethane synthesis and they were end capped with MMA and HEMA. Nature of the monomers used had an effect on thermal, morphological, and rheological properties that were interpreted in terms of the level of hydrogen bonding and degree of phase separation. Synthesized polymers were characterized by NMR, FTIR-ATR, DSC, TGA, GPC, Mass Spectroscopy, SEM and rheometry.
In the literature, polyurethane acrylate polymers have been synthesized from the isocyanate terminated polyurethanes in which the urethane chains were ended with isocyanate groups. However, the toxicity of the isocyanate groups limited their biomedical applications especially in prosthetic dentistry as a soft lining material. Therefore, it is inevitable to explore the cytotoxicity of polyurethane acrylate polymers. For this purpose, silver nanoparticles that have an average particle size of 40 nm, were incorporated to the synthesized polymers. This addition, which intends to improve the degree of cytotoxicity, was successful to a certain extent.
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Petrucci, Oscar. "Ferritin-Based Photo-Oxidation of Biomass for Nanoparticle Synthesis, Bioremediation, and Hydrogen Evolution." BYU ScholarsArchive, 2013. https://scholarsarchive.byu.edu/etd/4308.
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The cell is the basic unit of all living organisms. It is an amazing machine capable of self-replicating, growing, and synthesizing and shuttling thousands of compounds. To perform all of these activities the cell needs energy. The original source of energy for all living beings is the Sun. The energy of the sun is collected by the autotrophs (mostly plants) through photosynthesis and stored in the chemical bonds of carbohydrates and lipids through carboxylic acid intermediates; animals use these compounds to obtain the energy for their cells. Most of the energy extracted by the cell comes from the citric acid cycle. Therefore, two crucial energy transfer checkpoints are photosynthesis and citric acid cycle. With growing need for energy, the limited supply of fossil fuel, and the search for a cleaner environment, scientists have turned to the Sun (directly or indirectly through wind, tides, biomass, etc.) to satisfy the needs of modern society trying to reach the dual Holy Grail of energy: harvesting energy through Artificial Photosynthesis and Low Temperature Biomass Oxidation. This work represents one more step toward reaching these Holy Grails. The core reagent used in our technique is ferritin. Ferritin recapitulates some of the essential features of a plant cell: it contains a semiconductor capable of charge separation, like chlorophyll, acts as a membrane to isolate compartments, and has an enzymatic activity that prevents charge build up and oxidative damage. The energy absorbed by ferritin from the artificial “solar” radiation is used to extract reducing equivalents from stable and partially oxidized compounds, mainly carboxylic acids. The energized electrons produced are then used for a number of technical applications, from synthesis of catalytically active nanoparticles, to reductive precipitation of contaminant heavy metals (i.e.: mercury), to hydrogen evolution.
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Oliveira, Roberto Angelo de. "Estudo sobre a conversão, formação e desenvolvimento de nanopartículas de prata pelo método de Turkevich modificado." Universidade de São Paulo, 2013. http://www.teses.usp.br/teses/disponiveis/3/3137/tde-09072014-122808/.
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Pretendeu-se, com este trabalho, estudar a síntese e o desenvolvimento de nanopartículas de prata, utilizando o método de Turkevich com algumas modificações. Dada a importância dessas nanopartículas no atual desenvolvimento científico, é de grande valia o melhor entendimento dos mecanismos que regem a síntese e desenvolvimento das nanopartículas de prata. Neste método, nitrato de prata sofre redução pelo citrato de sódio, numa mistura aquecida e bem agitada, para formar as nanopartículas. Amostras dessa mistura foram coletadas em vários intervalos de tempo, e reservadas para análises de concentração de prata por ICPAES, absorbância UV-Vis, imagens de MEV e distribuição de tamanhos por DLS. Com essas análises, foi possível estabelecer uma relação direta entre os valores de absorbância e os de conversão de prata. Também foi possível propor uma rota de desenvolvimento das nanopartículas, mostrando que, durante esse desenvolvimento, as partículas apresentam diferentes morfologias, tamanhos e tendência a formar aglomerados. Dependendo da aplicação das nanopartículas de prata, é possível interromper a reação quando elas apresentarem as características mais favoráveis.<br>It was intended, with this work, to study the synthesis and development of silver nanoparticles using the Turkevich method with some modifications. Given the importance of these nanoparticles in the current scientific development, it is of great value the better understanding of the mechanisms governing the synthesis and growth of silver nanoparticles. In this method, silver nitrate is reduced by sodium citrate, in a well-stirred and heated mixture to form nanoparticles. Samples of this mixture were taken at various time intervals, and reserved for analysis of silver concentration by ICP-AES, UV-Vis absorbance, SEM images and size distribution by DLS. With these analyzes, it was possible to establish a direct relationship between the absorbance values and the conversion of silver. It was also possible to propose a synthesis and growth pathway of the silver nanoparticles, showing that during this development, the particles have different morphologies, sizes and tendencies to form agglomerates. Depending on the application of silver nanoparticles, it is possible to stop the reaction when they have the most favorable characteristics.
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Schelestow, Kristina. "Synthesis of silver nanoparticles in hydrogels." Master's thesis, Pontificia Universidad Católica del Perú, 2016. http://tesis.pucp.edu.pe/repositorio/handle/123456789/11908.
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The present work is concerned with the fabrication of a novel hydrogel-silver hybrid material, the characterization regarding its structural and antibacterial properties and the investigation of its interaction with glass surfaces. Hydrogels based on N-isopropylacrylamide, a functionalized macromonomer of 2-oxazolines and N,N'-methylene bisacrylamide as a cross-linker were synthesized via radical polymerization using ammonium persulfate and N,N,N,N'-tetramethylene diamine as initiator system. By complexion with silver cations from a silver nitrate solution and a subsequent reduction with sodium borohydre, silver nanoparticles inside the polymer network were formed. Bulk hydrogels of different composites were characterized concerning their structure and their water absortive capacity. The formation of silver nanoparticles as well as its influencing factors were analysed and could be confirmed quantitavely. The antibacterial activity of the developed composite material in this powder form was determinated via count test applying it to Staphylococcus aureus. The number of bacteria could be reduced to approximately 0.1% compared to the reference value without silver nanoparticles. Thus, the hydrogel-sliver hybrid can be appraised as suitable for biomedical applications. Finally, different hydrogel layers were produced on fotosensitive glass FS21 and evaluated regarding their applicability for microsystems technology.<br>Tesis
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Wickramasinghe, Sameera Madhusanka. "Synthesis and Study of Silver Molecular Nanoparticles." University of Toledo / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1438866207.
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Grasmik, Viktoria [Verfasser], and Matthias [Akademischer Betreuer] Epple. "Silver-based nanoparticles : synthesis and characterization of bimetallic silver-platinum and silver-gold nanoparticles / Viktoria Grasmik ; Betreuer: Matthias Epple." Duisburg, 2018. http://d-nb.info/1167683110/34.
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Bhattarai, Badri Bhattarai. "Green Synthesis and Gold Alloying of Silver Molecular Nanoparticles." University of Toledo / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1533312041161417.
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CHUGH, MOHITA. "GREEN SYNTHESIS OF SILVER NANOPARTICLES FROM CHLORELLA MINUTISSIMA." Thesis, DELHI TECHNOLOGICAL UNIVERSITY, 2021. http://dspace.dtu.ac.in:8080/jspui/handle/repository/18838.
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The development of a remediation technique that is environment friendly, efficient and
economical for the abatement of heavy metals and dyes will be an important step towards
the treatment of water pollutants. For this, silver nanoparticles were synthesized from
green algae Chlorella minutissima extract. For the enhancement of silver nanoparticles
synthesis, various optimization studies were carried out where different cell disruption
techniques (sonication, heating and autoclave), various range of pH (4 to 12) of reaction
mixture, various salt and biomass concentration along with contact time were studied.
Later, characterization techniques like visual detection and UV-Visible spectroscopy are
used for the characterization of silver nanoparticles. In the end, the application of these
silver phyconanoparticles were assessed in the remediation of six different heavy metals
and 5 different dyes. It is observed that it can remediate more than 96% of EY, MO and
EB and more than 87% CV and MB within 5 minutes and 65.18% nickel, 45.83% copper,
42% mercury, 33.84% cadmium within 1 hour and are less efficient in the case of cobalt
(4.5%) and chromium (0.5%). These results have shown the potential of silver
nanoparticles in the field of remediation of heavy metals and dyes. This project aims to
develop a more economical, sustainable and promising tool for the remediation of heavy
metals and dyes.
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Mesquita, Ricardy Leonam Pontes. "Synthesis of silver nanoparticles by ultrasound using galactomannan." Universidade Federal do CearÃ, 2016. http://www.teses.ufc.br/tde_busca/arquivo.php?codArquivo=17063.
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Universidade Federal do CearÃ<br>Silver nanoparticles (NPAg) have attracted considerable interest in the context of research in recent years due to numerous applications, such as a bactericide, sensors and catalysts. In this paper the use of galactomannan of fava danta (GFD) in obtaining NPAg by ultrasonic method was studied based on the principles of green chemistry without the use of conventional chemical reducing agent. This study aimed to evaluate the ultrasound employment in NPAg synthesis GFD solutions. The NPAg were obtained with the aid of an ultrasonic probe using AgNO3 aqueous solution in concentrations of 10, 40 and 100 mmol / L. The galactomannan in aqueous solution (0,032%, 0,32% and 0,0032% w/ v) was used as stabilizer of NPAg. The synthesis occurred at varying pH (10, 11, 12) and temperature (15, 25 and 35 ÂC). The characterizations were performed using techniques such as gel permeation chromatography (GPC), nuclear magnetic resonance of hydrogen (NMR1H), spectrophotometry UV-Vis, dynamic light scattering (DLS) and scanning electron microscopy (SEM). UV-Vis analysis for colloids formed during the synthesis at the three concentrations showed the emergence of the plasmon band (around 400 nm) suggesting the formation of NPAg. It was observed faster kinetic profile for concentration systems 10 mmol/ L AgNO3. The pH 11 and 12 provided the best conditions for synthesis of NPAg. The different concentrations of synthetic GFD showed satisfactory results, but the formed colloid concentration 0,0032% w/ v showed no stability. Two of the synthesized colloids were selected FDAg 10/12/25 and FDAg 100/12/25, to submit the study to estimate size during the time of formation of NPAg as were also objects of analysis by electron microscopy scan. DLS was evidenced by the two colloids have decreased the size NPAg during the synthesis time, reaching average sizes near 10 to 4 nm for FDAg 10/12/25 and FDAg 100/12/25 respectively. Monitoring the polysaccharide degradation by GPC analysis was conducted and it was observed the decrease in distribution of the molar masses of the same of 6,65 x 106 to 3,11 x 104 g/ mol during the degradation process. The mannose/ galactose ratio was observed for the GFD, from 1:1,23 to GFD unmodified to 1:2,14 for the GFD degraded in 420 minutes. Thus, this study showed that the ultrasonic path in conjunction with the use of the galactomannan of fava danta in aqueous solution provides a versatile synthetic route for NPAg with good stability.<br>NanopartÃculas de prata (NPAg) tÃm atraÃdo bastante interesse no Ãmbito da pesquisa durante os Ãltimos anos devido Ãs inÃmeras aplicaÃÃes, tais como agente bactericida, sensores e catalisadores. Neste trabalho o uso de galactomanana da fava danta (GFD) na obtenÃÃo das NPAg por mÃtodo ultrassÃnico foi estudado com base nos princÃpios da quÃmica verde sem a utilizaÃÃo de redutores quÃmicos convencionais. Este estudo teve como objetivo, avaliar o emprego do ultrassom na sÃntese de NPAg em soluÃÃes de GFD. As NPAg foram obtidas com auxÃlio de uma sonda ultrassÃnica, utilizando soluÃÃo aquosa de AgNO3 nas concentraÃÃes 10, 40 e 100 mmol/L. A galactomanana em soluÃÃo aquosa (0,032%, 0,32% e 0,0032% m/v) foi utilizada como estabilizante das NPAg. As sÃnteses ocorreram com variaÃÃo de pH (10, 11 e 12) e de temperatura (15, 25 e 35 ÂC). As caracterizaÃÃes foram realizadas atravÃs de tÃcnicas como Cromatografia de permeaÃÃo em gel (GPC), RessonÃncia magnÃtica nuclear de hidrogÃnio (RMN 1H), Espectrofotometria UV-Vis, Espalhamento de luz dinÃmico (DLS) e Microscopia eletrÃnica de varredura (MEV). As anÃlises de UV-Vis para os coloides formados durante as sÃnteses nas trÃs concentraÃÃes mostraram o surgimento da banda de plasmon (em torno de 400 nm) evidenciando a formaÃÃo das NPAg. Observou-se perfil cinÃtico mais rÃpido para os sistemas de concentraÃÃo 10 mmol/L de AgNO3. Os valores de pH 11 e 12 proporcionaram as melhores condiÃÃes de sÃntese das NPAg. As diferentes concentraÃÃes de GFD apresentaram resultados de sÃntese satisfatÃrios, porÃm o coloide formado em concentraÃÃo 0,0032% m/v nÃo apresentou estabilidade. Dois dos coloides sintetizados foram selecionados, FDAg 10/12/25 e FDAg 100/12/25, a se submeterem a estudo para estimativa de tamanho durante todo o tempo de formaÃÃo das NPAg, assim como tambÃm foram objetos de anÃlise por Microscopia eletrÃnica de varredura. Por DLS foi evidenciado que os dois coloides tiveram diminuiÃÃo de tamanho das NPAg no decorrer do tempo de sÃntese, atingindo tamanhos mÃdios prÃximos de 10 e 4 nm para FDAg 10/12/25 e FDAg 100/12/25 respectivamente. Foi realizado o acompanhamento da degradaÃÃo do polissacarÃdeo atravÃs de anÃlise por GPC, tendo sido observado a diminuiÃÃo da distribuiÃÃo das massas molares do mesmo de 6,65 x 106 para 3,11 x 104 g/mol durante o processo de degradaÃÃo. A razÃo manose/galactose foi verificada para a GFD, passando de 1:1,23 para a GFD nÃo modificada para 1:2,14 para a GFD degradada em 420 minutos. Sendo assim, este estudo mostrou que a via ultrassÃnica em conjunto com a utilizaÃÃo da galactomanana da fava danta em soluÃÃo aquosa proporciona uma rota sintÃtica bastante versÃtil para as NPAg com boa estabilizaÃÃo.
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Geng, Xi. "Bioenabled Synthesis of Anisotropic Gold and Silver Nanoparticles." Diss., Virginia Tech, 2017. http://hdl.handle.net/10919/86274.
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Anisotropic plasmonic noble metallic nanoparticles (APMNs) have received enormous attention due to their distinct geometric features and fascinating physicochemical properties. Owing in large part to their tailored localized surface plasmon resonance (LSPR) and the intensive electromagnetic field at the sharp corners and edges, APMNs are exceptionally well suited for biomedical applications such as biosensing, bioimaging, diagnostics and therapeutics. Although a rich variety of surfactant-assisted colloidal routes have been developed to prepare well-defined APMNs, biomedical applications necessitate tedious and rigorous purification processes for the complete removal of toxic surfactants. In this dissertation, we aim to develop generic bioenabled green synthetic methodologies towards APMNs. By applying a series of thermodynamic, kinetic and seed quality control, a series of APMNs with varied morphologies such as branched nanostars and triangular nanoprisms have been successfully prepared.
We first presented the preparation of gold nanostars (Au NSTs) through a two-step approach utilizing a common Good's buffer, HEPES, as a weak reducing agent. Single crystalline Au NSTs with tunable branches up to 30 nm in length were produced and the halide ions rather than the ionic strength played a significant roles on the length of the branches of Au NSTs. Then consensus sequence tetratricopetide repeat (CTPR) proteins with increasing number of repeats were used as model proteins to probe the effects of concentration as well as the protein shape on the morphology and resulting physicochemical properties of plasmonic gold nanoparticles.
Since the underlying growth mechanism for the biomimetic synthesis of APMNs remains elusive and controversial, the other objective is to elucidate the molecular interactions between inorganic species and biopolymers during the course of NP evolution. Fluorescent quenching and 2D NMR experiments have confirmed the moderate binding affinity of CTPR to the Au(0) and Au(III). We observed that the initial complexation step between gold ions and CTPR3 is ionic strength dependent. Furthermore, we also found that NPs preferentially interact with the negatively charged face of CTPR3 as observed in 2D NMR. Knowledge of binding behavior between biospecies and metal ions/NPs will facilitate rational deign of proteins for biomimetic synthesis of metallic NPs.
A modified seed-mediated synthetic strategy was also developed for the growth of silver nanoprisms with low shape polydispersity, narrow size distribution and tailored plasmonic absorbance. During the seed nucleation step, CTPR proteins are utilized as potent stabilizers to facilitate the formation of planar-twinned Ag seeds. Ag nanoprisms were produced in high yield in a growth solution containing ascorbic acid and CTPR-stabilized Ag seeds. From the time-course UV-Vis and transmission electron microscopy (TEM) studies, we postulate that the growth mechanism is the combination of facet selective lateral growth and thermodynamically driven Ostwald ripening.
By incorporation of seeded growth and biomimetic synthesis, gold nanotriangles (Au NTs) with tunable edge length were synthesized via a green chemical route in the presence of the designed CTPR protein, halide anions (Br⁻) and CTPR-stabilized Ag seeds. The well-defined morphologies, tailored plasmonic absorbance from visible-light to the near infrared (NIR) region, colloidal stability and biocompatibility are attributed to the synergistic action of CTPR, halide ions, and CTPR-stabilized Ag seeds.
We also ascertained that a vast array of biosustainable materials including negatively charged lignin and cellulose derivatives can serve as both a potent stabilizers and an efficient nanocrystal modifiers to regulate the growth of well-defined Ag nanoprisms using a one-pot or seeded growth strategy. The influential effects of reactants and additives including the concentration of sodium lignosulfonate, H2O2 and NaBH4 were studied in great detail. It implies that appropriate physicochemical properties rather than the specific binding sequence of biomaterials are critical for the shaped-controlled growth of Ag NTs and new synthetic paradigms could be proposed based on these findings.
Last but not the least, we have demonstrated the resulting APMNs, particularly, Au NSTs and Ag NTs exhibit remarkable colloidal stability, enhanced SERS performance, making them promising materials for biosensing and photothermal therapy. Since the Ag nanoprisms are susceptible to morphological deformation in the presence of strong oxidant, they also hold great potential for the colorimetric sensing of oxidative metal cation species such as Fe3+, Cr3+, etc.<br>Ph. D.
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Adam, Sarah. "Synthesis of monodisperse silver nanoparticles for antibacterial purposes." Master's thesis, University of Cape Town, 2018. http://hdl.handle.net/11427/29392.
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Safe drinking water is a scarcity for many in the developing world. Currently, 884 million people, 48% of whom live in sub-Saharan Africa, are without access to even basic drinking-water services (WHO/UNICEF Joint Monitoring Programme for Water Supply and Sanitation, 2017). This has a severe impact on the health of those living in such communities, which is why the universal access to safe and affordable drinking water has been made a priority by the United Nations. There is an undeniable need for change so that the lives of these many millions of people may be improved. Silver nanoparticles have great potential in being used in water disinfection applications because of their high antibacterial activity and broad antimicrobial spectrum (Qu, Alvarez, & Li, 2013). Development in this area is critical, particularly in advancing technology to allow greater accessibility to clean drinking water for people in poor, rural areas in developing countries. Incorporating nanotechnology into current water disinfection systems, as well as developing new water treatment nanotechnology, shows promise in addressing this issue. However, much research needs to be done first before this can become a reality (Q. Li et al., 2008). There is particular concern about the toxicity aspects of silver nanoparticles, both in humans and towards the environment. Whilst the current study does not investigate their toxicity, it is important to highlight the need to fully understand the human and environmental impacts nanoparticles may have in assessing their applicability in microbial control. Literature indicates that, although the role of silver nanoparticles themselves in the antibacterial mechanism cannot be excluded entirely, it is the silver ions that are mostly responsible for their antibacterial activity (Foldbjerg, Jiang, Miclăuş, et al., 2015; Le Ouay & Stellacci, 2015; Panacek et al., 2006; Xiu, Zhang, Puppala, Colvin, & Alvarez, 2012). Sotiriou & Pratsinis (2010) found that silver nanoparticles of smaller than 10 nm had a negligible antibacterial effect in comparison to the ions they released. Thus, to isolate just the effect of the released silver ions, it was desired to prepare uniformly sized particles of smaller than 10 nm. Controlling the size of the formed particles requires consideration of parameters that affect their nucleation and growth (Thanh et al., 2014). These can be thermodynamic, kinetic or stoichiometric parameters. It is on this basis that the work described herein was developed. This study aimed to synthesise silver nanoparticles suitable for use in water disinfection applications by exploring how preparation conditions affect the particle size and distribution. To do this, two different aqueous chemical reduction preparation methods were performed and reaction conditions such as surfactant concentration, agitation rate, synthesis temperature, and method of chemical addition were varied to produce monodisperse silver nanoparticles with an average size of smaller than 10 nm. This study also aimed to investigate the antibacterial efficacy of silver nanoparticles deposited on quartz fibre filters against E. coli. Two silver nanoparticle syntheses procedures were extensively investigated. Method One (AL-Thabaiti et al, 2008) uses ascorbic acid as the reducing agent and SDS (sodium dodecyl sulphate) as the surfactant whilst Method Two (Yang, Yin, Jia, & Wei, 2011) uses aniline as the reducing agent, DBSA (dodecylbenzenesulfonic acid) as the surfactant and NaOH (sodium hydroxide) as the ‘activating’ chemical. The surfactant concentrations, agitation rates, synthesis temperature, reducing agent concentrations and methods of chemical addition were varied for each of these synthesis procedures and the effect thereof on particle size was investigated. Both synthesis methods produced fcc metallic silver nanoparticles with (111) and (200) lattice planes, confirmed by studying nanoparticle d-spacings. For Method One, the unaltered synthesis procedure produced the smallest particles with a numberbased mean size of 3.6 ± 3.8 nm and a volume-based mean particle size of 15.4 ± 6.4 nm. For Method Two, which is performed at 90 °C, the ‘hot’ injection of NaOH into the system resulted in the production of the smallest nanoparticles with a number-based mean particle size of 6.7 ± 5.4 nm and a volumebased mean particle size of 22.3 ± 10.9. Removing excess surfactant and collecting these nanoparticles in powder form would facilitate antibacterial efficacy studies, however this proved to be difficult. Additionally, the presence of large nanoparticles in both samples, as evidenced from the volume-based size distributions, means that in assessing antibacterial activity of the nanoparticles, it will be difficult to interpret whether the bactericidal effect is due to silver ions or because of an interaction between the bacteria and the actual nanoparticles. Antibacterial efficacy studies were therefore not performed on these synthesised silver nanoparticles. Silver nanoparticles deposited on quartz fibre filters via spark ablation were prepared at Delft University of Technology. SEM revealed that the deposited nanoparticles on the filters had a mean particle size ranging from 25 to 70 nm. Studies using E. coli (ATCC® 25922™) did not conclusively demonstrate antibacterial activity of the filters. It is believed the large particle size, and thus slow dissolution into silver ions, may be the reason for the lack of evidence of bactericidal activity over the 24-hour experimental period. The results of this study indicate how small changes in synthesis parameters can have a significant effect on nanoparticle size and uniformity, morphology, and degree of agglomeration. This reveals the importance in specifying exact parameters used in nanoparticle preparation to allow for better reproducibility, including vessel size, mixing speed, and rate of chemical addition. This work also showed that it is important to quantify the release of silver ions from silver nanoparticles before performing antibacterial efficacy assessments. Since silver ions are the most important factor in the antibacterial action of silver nanoparticles, understanding their rate of release will allow for improved experimental design thus producing useful results. There is great potential for the use of silver nanoparticles for disinfection, as evidenced particularly by the antibacterial efficiency of Ag+ against E. coli (ATCC® 25922™). However, improvements in both the synthesis of silver nanoparticles and methods of assessing their bactericidal efficacy are clearly necessary. This study has highlighted the challenges that may be faced in the pursuit of efficiently and safely using silver nanoparticles for water treatment and disinfection. Numerous recommendations for future studies have been put forward. These include: further optimisation of the nanoparticle synthesis procedure so as to produce particles of the desired size and acquire them in powder form, performing a thermodynamic estimation of the equilibrium silver ion concentration as a function of silver nanoparticle size to quantify the effect nanoparticle size will have on bactericidal activity, and using more realistic water conditions for antibacterial efficacy experiments to simulate the environment in which silver nanoparticles will be applied.
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Kemal, Lydia Materials Science & Engineering Faculty of Science UNSW. "Gold and silver nanoparticles: synthesis, characterization and functional properties." Publisher:University of New South Wales. Materials Science & Engineering, 2008. http://handle.unsw.edu.au/1959.4/43108.
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This thesis focuses on the shape-controlled metal nanoparticles for functional applications, covering the synthesis, characterization and optical properties. Three parts are mainly involved in this work, including, gold worm-like nanoparticles, silver nanoplates, and silver induced selenium nanowires. The first part focuses on a facile synthesis method for shape control of gold nanoparticles by treating an aqueous solution of chloroauric acid with sodium citrate and poly(vinyl pyrrolidone) (PVP), in which those worm-like nanoparticles were investigated by various advanced experimental characterizations combining density function theory (DFT) calculation. These nanoparticles can be used for optical sensing detection of ions in aqueous system. The second part involves the synthesis, growth, and optical properties of silver nanoplates (triangles and circular discs). Such nanoplates could be synthesized by a self-seeding co-reduction method at ambient conditions. In particular, molecular dynamics simulation is used to quantify the interaction energies between surfactant molecules and different facets of silver crystal. Such molecular information, together with measurements using x-ray diffraction (XRD), transmission electron microscopy (TEM), atomic force microscopy (AFM) and ultraviolet??visible (UV??vis) spectroscopy, has proven to be useful for understanding the growth mechanisms of silver nanoplates. The third part focuses on the template of silver nanoparticles for generating trigonal selenium (t-Se) nanowires. This technique exhibits some advantages in fabricating t-Se nanostructures, including no need to use stabilizers and sonichemical process and all operations being proceeded in aqueous media and at room temperature. Particularly it can successfully achieve the transformation from amorphous α-Se to crystalline t-Se in aqueous solution and this method would be useful for generating one-dimensional nanostructures with similar lattice parameter(s). It is considered that the technique for the shape-controlled metal nanoparticles can at least partially, be extended to other nanomaterials for functional applications.
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Sithole, Zimasa N. "Synthesis of silver nanoparticles and investigating their antimicrobial effects." University of the Western Cape, 2015. http://hdl.handle.net/11394/4707.
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>Magister Scientiae - MSc<br>Water is essential for life, yet access to safe drinking water is still a major concern worldwide due to waterborne diseases. The current study proposes silver nanoparticles (AgNPs) as an antibacterial agent. Silver nanoparticles were synthesised using different reductants and stabilisers, and the resulting structures were characterised with Ultra-violet visible (UV-vis) spectroscopy, transmission electron microscopy (TEM), energy-dispersive spectroscopy (EDS) analysis. The antibacterial properties of the AgNPs were tested against a panel of 5 indicator organisms: Cupriavidus metallidurans, Staphylococcus epidermidis, Mycobacterium smegmatis, Bacillus cereus and a multi-drug resistant Escherichia coli 1699. Spherical AgNPs that absorbed at around 400 nm, with diameters ranging between 18.8-26.4 nm or 5.4-13.1 nm were prepared by ascorbic acid or sodium borohydride respectively. The optimum processing conditions that produced 6±1.8 nm spherical nanoparticles included maintaining the temperature at 0 ⁰C, the pH at 9.78 and the NaBH4/Ag/PVP ratio at 16:1:10. Exposing AgNPs to light for 6 hours did not alter the particle size rather it changed the particles shape from spherical to icosahedral. Stirring caused particles to agglomerate, however, no agitation resulted in the formation of irregular structures of different sizes. Sensitivity to the AgNPs ranged between 25 % and 100 % reduced bacterial growth depending on the strains used and the concentration of the AgNPs. The Gram negative bacteria were more sensitive to AgNPs than Gram positive bacteria. However silver ions were more toxic than AgNPs for all but one of the strains tested, B. cereus was completely resistant to both Ag+ and AgNPs. C. metallidurans and E.coli (1699) showed a dose dependent sensitivity to AgNPs and the minimum inhibitory concentrations were established at 50 and 20 mg/L AgNPs respectively. C. metallidurans and E.coli (1699) were also eradicated by 10 mg/L Ag+. The E. coli TEM images showed accumulation of AgNPs within the cells, cell shrinking and leakage of cellular components. This suggests that AgNPs have a similar toxicity effect on bacterial cells as Ag+.
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Ashenfelter, Brian A. "Understanding the Synthesis and Properties of Molecular Silver Nanoparticles." University of Toledo / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1431052162.
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Amendola, Vincenzo. "Synthesis of gold and silver nanoparticles for photonic applications." Doctoral thesis, Università degli studi di Padova, 2008. http://hdl.handle.net/11577/3425014.
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Guimera, Coll Pablo. "A wet chemistry synthesis of silver nanoparticles from bulk material." Thesis, Kansas State University, 2015. http://hdl.handle.net/2097/32790.
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Master of Science<br>Department of Physics<br>Christopher M. Sorensen<br>An easier, cheaper and scalable method to obtain silver nanoparticles, AgNPs, directly from the bulk material has been obtained. Two different solvents were tried, water and ethylene glycol, the coating agent was polyvinylpyrrolidone, PVP, and two different silver sizes were used, micron size powder and silver shots, millimeter size. It was seen that changing the size of bulk silver, the temperature of reaction, the amount of oxygen, the concentration of PVP and its molecular weight all had an important influence in the synthesis of nanoparticles. Different morphologies could be obtained when these parameters were adjusted ranging from spheres to triangles and hexagons. A complex mechanism is proposed: during the first step, bulk silver is oxidized by oxygen in solution, forming a thin layer of oxidized silver on the surface. Then, PVP acts as a reducing agent at the oxidized surface, where silver becomes Ag⁰ again. At the same time that PVP reduces the oxidized silver back to metallic silver; it coordinates with the silver atoms acting as a protecting agent. That coordination between PVP and silver pulls out the atoms and produces a detachment of silver atoms from the bulk surface. These silver-PVP complexes in solution later combine to form silver nanospheres and evolve to rods first and then triangles and hexagon with longer reaction time.
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Torres, Heredia Victor Elias. "Silver nanostructures: chemical synthesis of colloids and composites nanoparticles, plamon resonance properties and silver nanoparticles monolayer films prepared by spin-coating." Doctoral thesis, Universitat Politècnica de Catalunya, 2011. http://hdl.handle.net/10803/52807.
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El presente trabajo tiene como objetivo desarrollar en solución acuosa y a tem-peratura ambiente, rutas de síntesis química coloidal de nanopartículas de plata y nano-partículas compuestas estables. Se obtienen nanopartículas de plata reproducibles, con un control morfológico de tamaño y forma durante el proceso de síntesis. Llevamos a cabo el estudio de las propiedades ópticas (espectros de absorción de las resonancias de plasmones superficiales (SPR)) que caracterizan a una determinada forma y tamaño. El análisis incluye estructuras nanométricas de plata de diferentes tamaños, en ambientes diversos y formas diferentes, como esferas, prolates, y prismas de diferente sección transversal, etc
Se ha demostrado que la síntesis química produce coloides de nanopartículas de plata esféricas y anisotrópicas estables. La morfología y estabilidad de las nanopartícu-las coloidales son estudiadas mediante técnicas de espectroscopia y microscopía elec-trónica. El rol y concentración necesaria de cada uno de los reactivos para producir co-loides estables mediante síntesis química son determinadas. Se ha demostrado que, con-trariamente a las opiniones actualmente expresadas en la literatura, es posible controlar el tamaño de las nanopartículas de plata y obtener coloides de nanopartículas de plata esféricas y anisotrópicas estables por largo tiempo, utilizando una ruta de síntesis quí-mica sencilla y una baja concentración de reactivos estabilizadores (PVP).
Recubrimientos de nanopartículas esféricas de plata estabilizadas con polivinilpirroli-dona (PVP) sobre substratos de vidrio óptico son preparados mediante el proceso de spin-coating y un posterior tratamiento térmico.
Diferentes morfologías tipo core-shell de Ag@SiO2 son preparados mediante un método químico simple y rápido, sin necesidad de adicionar reactivos de acoplamiento o modificadores superficiales de la sílice. Proponemos mecanismos de reacción para la preparación de diferentes nano-estructuras tipo core-shell de plata-sílice. Las nanopartí-culas compuestas de sílice-plata muestran unas propiedades de absorción de resonancia plasmónica muy evidentes. El trabajo de éste capítulo ha sido realizado en colaboración con Juan C. Flores, quien desarrolló la ruta de síntesis como parte de sus estudios de doctorado.
Por último, una modificación del método sol-gel es empleada para la prepara-ción de nanopartículas de TiO2, y partículas compuestas de Ag@TiO2, SiO2@TiO2-Ag y SiO2@Ag@TiO2. Diferentes morfologías tipo core-shell son preparadas mediante un método químico simple y rápido sobre un substrato óxido, sin necesidad de adicionar agentes de acoplamiento o modificaciones superficiales. Las evidentes propiedades de absorción plasmónica de las nanopartículas de plata mostradas por las partículas com-puestas han demostrado la presencia de plata metálica sobre la titania, sin la posterior oxidación de la capa de plata por el contacto directo con la titania (TiO2). Esta evidencia es confirmada por la técnica de microscopía electrónica de alta resolución. Las propie-dades de absorción plasmónica de las partículas compuestas hacen a estos materiales muy prometedores para aplicaciones foto-catalíticas.<br>The present work aims to develop chemical synthesis routes of stable colloidal silver nanoparticles and composites nanoparticles in aqueous solution at room tempera-ture. We obtain reproducible morphological control of silver nanoparticles size and shape during synthesis solely by solution chemistry and carry out the study of the opti-cal properties (surface plasmon resonances (RPS) absorption spectra) which character-ize a specific shape and size. The analysis includes silver nanosized bodies of different size, in diverse environments and of various shapes, as spheres, prolates, and prisms of different transversal section, etc.
Synthetic wet chemistry routes yielding stable colloids of spherical and aniso-tropic silver nanoparticles are demonstrated, and the morphology and stability of the colloidal nanoparticles studied extensively through spectroscopy and electron micros-copy techniques. The role of each reagent and the concentrations required to obtain sta-ble colloid via these wet chemical routes is determined. It was shown that, contrary to commonly expressed opinions in the literature, it is possible to control the particle size of silver nanoparticles and obtain long-term sable colloids of both spherical and aniso-tropic silver nanoparticles using simple chemical routes and low concentration of stabi-lizing agent (PVP).
Films of polyvinylpyrrolidone (PVP) stabilized spherical silver nanoparticles are also prepared, by using spin coating on standard optical glass plates and subsequent thermal processing.
Different core-shell type morphologies of Ag@SiO2 are also produced using a simple and rapid chemical method, without using added coupling agents or surface modifications of silica. We propose reaction mechanisms for the formation of the dif-ferent silica-silver core-shell nanostructures. The silica-silver composite nanoparticle display clear plasmonic resonance absorption properties. This chapter work has been done in collaboration with PhD student Juan C. Flores who developed the synthesis route as part of his doctoral studies.
Finally, a sol-gel chemistry approach was used to fabricate nanoparticles in the systems TiO2, Ag@TiO2, Ag@TiO2-SiO2 and TiO2@Ag@SiO2. Different core-shell morphologies are produced using a simple and rapid chemical method. without using added coupling agents or surface modifications of the oxide substrate. Clear silver na-noparticle plasmonic absorption properties shown by the composite nanoparticles demonstrate the formation of metallic Ag, without the oxidation of Ag nanoshell in di-rect contact with TiO2, evidence confirmed also by high resolution electron microscopy. The plasmonic absorption properties of the composites nanoparticles make them a promising material for photocatalytic applications.
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Khlebtsov, B. N., and E. V. Panfilova. "Synthesis and Study of PNIPAM Nanogels Incorporated with Colloidal Silver." Thesis, Sumy State University, 2013. http://essuir.sumdu.edu.ua/handle/123456789/35090.
Full textAbstract:
Composite nanoparticles consisting of polymer gels with incorporated silver nanoparticles have been synthesized. The synthesis comprises two main stages. Initially, monodisperse hydrogel particles with a controlled diameter of approximately 500 nm are obtained by N-isopropylacrylamide polymerization. Then, silver ions are reduced on the surface of the polymer network. Variations in the concentration ratio between reductants and silver nitrate make it possible to produce silver nanoparticles with sizes in a range of 10-30 nm and different packing densities on the gel particle surface. The resultant nanocomposites have been studied by transmission electron microscopy, spectrophotometry, and dynamic light scattering. Depending on the size and packing density of the silver nanoparticles on the polymer particle surface, the plasmon resonance of the nanocomposites varies in a range of 420-750 nm, which determines variations in the color of the colloid from yellow, orange, and red to blue and blue-green. After the inclusion of silver nanoparticles, nanogels of poly(N-isopropylacrylamide) retain their capability for thermosensitive phase transition with a lower critical mixing temperature of 31 °C.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/35090
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Nqunq, Sphamandla. "Optical and microarray silver-gold based sensors for the detection of e.coli 0157:h7 in seawater." University of the Western Cape, 2021. http://hdl.handle.net/11394/8256.
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>Magister Scientiae - MSc<br>Recently researchers reported that nanoparticles functionalised through chemical methods possess risks to the environment and to the human health since they use hazardous chemicals and produce toxic waste. The increasing demand of nanomaterials for application in the field of science require an alternative method for synthesis of nanomaterials that are environmentally friendly, eco-friendly and non-toxic. The present study describes the green synthesis method for functionalisation of nanomaterials. Green synthesis methods are considered as a novel approach for functionalisation of nanoparticles using biological sources.<br>2022
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Cumberland, Susan Alison. "Synthesis and environmental chemistry of silver and iron oxide nanoparticles." Thesis, University of Birmingham, 2011. http://etheses.bham.ac.uk//id/eprint/1736/.
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Engineered nanoparticles are defined as having a dimension that is between one and one hundred nanometres. With toxicology studies reporting various degrees of toxicity the need to investigate nanoparticle fate and behaviour is vital. Monodispersed engineered nanoparticles were synthesised in-house to produce suitable materials to examine such processes. Iron oxide nanoparticles (5 nm) and citrate coated silver nanoparticles (20 nm) were subjected to different conditions of pH, ionic strength and different types of commercially available natural organic matter. Changes in particle size and aggregation were examined using a multi-method approach. Results showed that the natural organic matter was able to absorb onto nanoparticle surfaces and improve their stability when subjected to changes in pH and ionic strength, where they would normally aggregate. The presence of higher concentrations of NOM in some cases promoted aggregation due to bridging. This work also concluded that silver nanoparticles could be produced in the presence of NOM without additional stabilisers and that they themselves were stable. This work has demonstrated that engineered nanoparticles could remain stable within a range of environmental conditions, and thus raise future pollution concerns.
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Ziegler, Christoph. "Syntheses and Assemblies of Noble Metal Nanostructures." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2013. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-101781.
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Shape and size control as well as the control of the assembly of nanostructures are current challenges in nano sciences. Focussing on metal nanostructures all of these aspects have been addressed in the frame of the present work. It was possible to develop a new aqueous seeded growth method that produces gold nanoparticles with adjustable diameters over a large range of sizes. The spherical particles obtained show very low polydispersities and a good long term stability. Furthermore it was possible to reveal the growth mechanism of these particles utilizing electron microscopy and optical investigations coupled with theoretical calculations. It was found that there is a formation of small nucleation sites on the surface of the seeds in the beginning of the growth process. These sites then subsequently grow into "blackberry-like" intermediate particles. A final intraparticle ripening step leads to smooth and uniform spherical gold nanoparticles. By correcting the dielectric function of gold for charging and the free mean path effect and taking into account the particle size distribution it was possible to accurately model the optical properties of the gold sols obtained using Mie theory.
By controlling the concentration of chloride ions it was possible to influence both the ripening of the "blackberry-like" shaped particles and the morphology of gold nanoparticles. An increased concentration of the chloride ions in the standard citrate reduction procedure leads to larger and elongated particles, whereas the complete removal of the chloride ions made it possible to obtain star shaped, decahedral and \"desert-rose\" shaped particle morphologies. Using the layer-by-layer technique gold nanoparticles of different sizes could be immobilized on glass substrates. The surface-enhanced Raman scattering intensity of these mixed films were about 60% higher than compared to a film made of a single particle size. The optical properties were further investigated by comparing experimentally obtained UV/Vis spectra with generalized Mie theory simulations.
Additionally it could be shown that tetrazole and its derivatives are suitable stabilizing agents in the aqueous synthesis of silver nanoparticles. It was found that depending on the tetrazole derivative used the tendencies of the nanoparticles to agglomerate vary significantly. Different agglomeration stages have been investigated by UV/Vis and Raman spectroscopy. The removal of the ligands used and a resulting improvement of the applicability of the silver nanostructures as SERS substrates is still a challenge.
In the last part of this work the focus was changed from the optical properties of noble metal nanoparticles to their catalytic properties. Therefore gold and palladium nanoparticles have been successfully immobilized on highly porous zinc oxide aerogels. It was possible to synthesize sponge-, flake-, and ribbon-like zinc oxide gels with high specific surface areas. The facile approach of generating mixed metal oxide/noble metal aerogels is very promising for the preparation of highly selective and highly active heterogenous catalysts. First catalytic investigations of a sponge-like palladium loaded zinc oxide aerogel toward the semi-hydrogenation of acetylene showed very high selectivities of up to 85%.
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Abkhalimov, E. V., R. D. Solovov, and B. G. Ershov. "Composite Ag-Pt Nanoparticles in Aqueous Solution." Thesis, Sumy State University, 2012. http://essuir.sumdu.edu.ua/handle/123456789/35033.
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It is shown that the saturation of an aqueous solution containing K2PtCl4 with hydrogen in the presence of 6.3 nm silver nanoparticles leads to the reduction of platinum on the silver surface and the formation of Ag/Pt core-shell nanoparticles. The Ag:Pt molar ratio is varied from 9:1 to 1:9 for synthesizing Pt
shell layer of different thickness. An apparent shift of Ag surface plasmon band from 405 nm to 230 nm
and broadening of one with decrease of Ag:Pt ratio was observed. The TEM images and SAED pattern of
Pt@Ag nanoparticles has been obtained. The UV-Vis and TEM data confirms a formation of Ag/Pt coreshell nanoparticles.
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Vassilieff, Tatiana. "Dumbbell shaped dendrimers: synthesis, characterization and application in assemblilng silver nanoparticles." Thesis, McGill University, 2008. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=19290.
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Synthesis and detailed characterization of dendrimers that evolve symmetrically from a linear bifunctional core (2-butyne-1,4-diol) with 3,5-dihydroxybenzyl alcohol based dendron wedges, are reported. The divergent, layer-by-layer build-up of the dumbbell shaped dendrimers, is based on simple acid-base hydrolytic chemistry of bis(dimethylamino)dimethylsilane with OH terminated molecules. Evaluation of some of the structure-property relationships in these dendrimers was carried out to obtain a better understanding of their potential applications. The self-assembly of these dendrimers in THF and water is significantly influenced by their generation number, the backbone structure and the solvent. Generations 1-3 dendrimers form aggregates at a higher critical aggregation concentration (cac) compared to generation 4 in THF. This behavior is related to the open structure in the lower generations with a linear core becoming important in their self-assembly, while in generation 4, more globular architecture with more prominent hydrogen bonding sites, facilitates self-assembly at lower concentrations. In water and in generations 1 and 2 dendrimers, the inability of more polar solvent to interact with their backbones, leads to aggregates that are formed by minimizing the repulsive forces. In generations 3 and 4, the major interaction of the solvent with the dendrimer is at the periphery which has a higher concentration of polar OH groups, and it does not interfere significantly with their ability to self-associate. Using these dendrimers as templates, a simple methodology in which silver nanoparticles are synthesized in one pot reaction, has been developed. The dendrimer structure provides reactive peripheral hydroxyl groups as well<br>Ce master présente la synthèse et la caractérisation détaillée de dendrimères symétriques constitués d'un noyau bifonctionnel linéaire (2-butyne-1,4-diol) et de dendrons formés à partir de l'alcool 3,5-dihydroxybenzylique. La construction divergente, couche-par-couche de ces dendrimères en forme d'haltères est basée sur une simple hydrolyse acido-basique entre l'aminosilane Me2Si(NMe2)2 et les molecules possédant des groupements hydroxyles terminaux. Certaines propriétés physiques de ces dendrimères ont été explorées afin de mieux comprendre leurs applications potentielles. Notamment, nous avons démontré que l'auto- assemblage de ces dendrimères en agrégats dépend du nombre de génération, de leur structure et du solvant. En effet, les dendrimères de générations 1 à 3 forment des agrégats à une concentration critique d'agrégation plus élevée que celle des dendrimères de génération 4 dans le THF. Ce phénomène est dû à la structure plutôt ouverte des dendrimères de basse génération qui possèdent un noyau linéaire devenant prédominant dans le phénomène d'auto-assemblage. Par contre, les dendrimères de génération 4 adoptent une architecture plus globulaire qui favorisent les liaisons hydrogène et facilitent leur auto assemblage à basses concentrations. Dans l'eau, les dendrimères générations 1 et 2 forment des agrégats en minimisant leurs forces répulsives, ce solvant plus polaire ne pouvant que très peu interagir avec les noyaux aromatiques constituant les dendrons. Dans le cas des dendrimères de générations 3 et 4, le solvant interagit principalement avec les groupes hydroxyles terminaux présents à plus haute concentration, et ceci n'influence pas de manière sig
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Ritson, David R. "The sonoelectrochemical synthesis of silver nanoparticles and their applications to SERS." Thesis, University of Liverpool, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.494096.
Full textAbstract:
Due to the unique ability of metallic nanoparticles to change their optical properties depending on their size and morphology there is an ever increreasing need to not only discover new methods for their anisotropic synmthesis but also to understand more fully the processes which lead to this shape directed growth The aim of this research was both the wet chemical and the electrochemical synthesis of metallic nanoparticles and nanorods for the construction of films appropriate for their use in Surface Enhanced Raman Spectroscopy in analytical applications. For this, a controlled nucleation and growth strategy coupled to ultrasonic pulses has been investigated. The kinetics of the electrochemical phase transformation of silver onto both platinum and glassy carbon along with the influence of pulse parameters on current density in varying conditions were systematically studied by means of cyclic voltammetry and potential step experiments. Nucleation and growth were controlled independently and electrodeposited small clusters were dislodged using an ultrasonic pulse at an appropriate time of the nucleation-growth sequence. Monodisperse silver nanoparticles of varing sizes stabilised by polyvinylpyrrohdone have been synthesised and were characterised by UV-Vis Spectroscopy and Transmission Electron Microscopy.
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Tejamaya, Mila. "Synthesis, characterization, and stability test of silver nanoparticles in ecotoxicology media." Thesis, University of Birmingham, 2014. http://etheses.bham.ac.uk//id/eprint/5360/.
Full textAbstract:
Currently silver nanoparticle (AgNP) is the most widely used NP. Potential hazard of AgNP to the environment, however, is largely unknown. Lack of NP characterization data in most of (eco) toxicology study, transformation of NPs in the test media and environment, etc. have challenged the attempt of presenting NP dose and toxic outcome. Therefore more control over NP ecotoxicology study need to be done. This study was aimed to synthesis a stable, fully characterized and tightly constrained PVP-capped AgNPs via bottom-up method. Modification of Mulfinger et al. (2007) synthesis protocol has been successful in generating spherical and monodisperse PVP-capped AgNPs. Another straightforward synthesis method was developed via ligand-exchanged (indirect method) from a monodisperse citrate-capped AgNPs. PEG-SH, Fulvic acid and Tween-80 polymers was also tried to recap citrate-coated AgNPs. There were no size and shape alterations as PVP and fuvic acid replaced citrate coating, while PEG-SH and Tween-80 polymer did. Ali polymers, nevertheless improved the AgNPs stability in ecotoxicology media. The stability of citrate; PEG-SH; and PVP-capped AgNPs due to incubation in several ecotoxicology media with variation in media ionic strength/concentration and composition was examined. It was seen that PVP polymer showed a better stabilization effect than citrate and PEG-SH. Shape transformation was seen for AgNPs after incubated in media without chloride (nitrate and sulphate media), especially in concentrated media. Thus type of capping agent; media ionic strength and chemical composition determined the behavior and stability of AgNPs in ecotoxicology media.
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Nqakala, Zimkhitha Biancah. "Synthesis of DMSO based silver nanoparticles for application in wound healing." University of Western Cape, 2021. http://hdl.handle.net/11394/8233.
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>Magister Scientiae - MSc<br>Silver nanoparticles (AgNPs) apart from being chemically significant, have shown a lot of health benefits, the most studied being their anti-bacterial and anti-inflammatory properties. These biological properties can be further enhanced by adding compounds with known medical properties giving rise to even more desired potent materials. Anti-bacterial and cytotoxicity studies show that these AgNPs can kill bacteria, prevent infections and regenerate skin cells. On the other hand, previous studies have reported dimethyl sulfoxide (DMSO) with attractive wound healing abilities specifically cell growth promotion. It was then envisaged that the combination of DMSO and AgNPs could lead to a potent wound healing agent. It is a well-known fact that non-healing wounds pose a socioeconomic threat to a large population worldwide.<br>2023
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Tsibakhashvili, N. Ya, E. J. Kirkesali, D. T. Pataraya, et al. "Microbial synthesis of silver nanoparticles by streptomyces glaucus and spirulina platensis." Thesis, Sumy State University, 2011. http://essuir.sumdu.edu.ua/handle/123456789/20679.
Full textAbstract:
Microbial synthesis of nanoparticles has a potential to develop simple, costeffective
and eco-friendly methods for production of technologically important
materials. In this study, for the first time a novelactinomycete strain Streptomyces glaucus71
MD isolated from a soy rhizosphere in Georgiais for the first time extensively
characterized and utilized for the synthesis of silver nanoparticles. Scanning Electron
Microscope (SEM) allowed observing extracellular synthesis of nanoparticles, which
has many advantages from the point of view of applications. Production of silver nanoparticles
proceeded extracellularlywith the participation of another microorganism, bluegreen
microalgae Spirulinaplatensis (S. platensis). In this study it is shown that the
production rate of the nanoparticles depends not only on the initial concentration of
AgNO3 but also varies with time in a nonmonotonic way. SEM study of silver nanoparticles
remaining on the surface of microalgae revealed that after 1 day of exposure to 1
mM AgNO3 nanoparticles were arranged as long aggregates along S. platensiscells
strongly damaged by silver ions. However, after 5 days of exposure to silver S. platensiscells
looked completely recovered and the nanoparticles were distributed more uniformly
on the surface of the cells.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/20679
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Nate, Zondi. "Green synthesis of copper and silver nanoparticles and their antimicrobial activity." Thesis, Vaal University of Technology, 2018. http://hdl.handle.net/10352/424.
Full textAbstract:
M. Tech. (Department of Chemistry, Faculty of Applied and Computer Sciences), Vaal University of Technology<br>The present study includes the use of a green synthetic method to prepare copper and silver nanoparticles using chitosan, aqueous extracts of Camellia sinensis, Combretum molle and Melia azedarach linn leaves. This study aims to investigate the influence of capping and precursor concentration on the properties of silver nanoparticles with emphasis on the medicinal plants chosen. The effect of capping agent on the properties of copper nanoparticles is also investigated. The phytochemical properties of plant extracts and the antimicrobial activity of the synthesized particles were also studied; this was achieved by using microdilution bioassay. Decoction method was used to extract secondary metabolites from plant leaves. Preliminary phytochemical screening carried out on the aqueous extracts of the plant leaves showed the presence of tannins, proteins, flavonoids, phenols, and carbohydrates. The total phenolic and flavonoids content of the aqueous extract was determined using spectroscopic methods. The highest phenolic content was found in the aqueous extract of Combretum molle (135 mg/g), and the highest flavonoid content was found in the aqueous extract of Camellia sinensis (0.4 mg/g).
Characterization was done by a combination of spectroscopic, microscopy and XRD techniques. Both the size and shape of the synthesized silver nanoparticles were dependent on the identity of the capping molecule, precursor and capping agent concentration as depicted from their TEM and XRD results. Silver nanoparticles were found to be predominantly spherical. The capping agent concentration was also found to influence the degree of agglomeration, with an increase in capping agent concentration giving lesser agglomeration. FTIR spectral analysis showed that silver nanoparticles interact with bioactive compounds found in the plants through the hydroxyl functional group. Other shapes including diamond were observed for the effect of precursor concentration. The XRD micrographs revealed a face-centered cubic geometry and the phase remained the same with an increase in precursor concentration. The synthesized silver nanoparticles were all blue shifted compared to the bulk material. The TEM results revealed that copper nanoparticles with different sizes and shapes were successfully synthesized.
All the prepared copper and silver nanoparticles showed satisfactory antifungal and antibacterial activity against Candida albicans, Cryptococcus neoformans, Staphylococcus aureus, Enterococcus faecalis, Klebsiella pneumonia and Pseudomonas aeruginosa. The capping molecules used in this study also showed some antibacterial and antifungal activity against the selected strains. However nanoparticles performed better than these capping molecules. Both silver and copper nanoparticles were found to be more active against gram-negative bacteria compared to gram-positive bacteria. Amongst all the prepared silver nanoparticles Combretum molle capped nanoparticles were found to be the most active nanoparticles. Also with copper nanoparticles, it was found that Combretum molle capped nanoparticles were the most active nanoparticles. Between the two metal nanoparticles, silver nanoparticles showed high antibacterial and antifungal activity compared to copper nanoparticles.
The antioxidant activity of silver nanoparticles was assessed using 2.2-diphenyl-1-picrylhydrazyl. Silver nanoparticles were found to have some antioxidant activity. However, the capping molecules were found to be more active than the synthesized nanoparticles. This observation is attributed to the presence of some bioactive compounds in the plant extracts.
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Pardoe, Andrea. "Photochemical Synthesis of Mono and Bimetallic Nanoparticles and Their Use in Catalysis." Thèse, Université d'Ottawa / University of Ottawa, 2011. http://hdl.handle.net/10393/19951.
Full textAbstract:
Nanomaterials have become a popular topic of research over the years because of their many important applications. It can be a challenge to stabilize the particles at a nanometer size, while having control over their surface features.
Copper nanoparticles were synthesized photochemically using a photogenerated radical allowing spatial and temporal control over their formation. The synthesis was affected by the stabilizers used, which changed the size, dispersity, rate of formation, and oxidation rate. Copper nanoparticles suffer from their fast oxidation in air, so copper-silver bimetallic nanoparticles were synthesized in attempts to overcome the oxidation of copper nanoparticles. Bimetallic nanoparticles were synthesized, but preventing the oxidation of the copper nanoparticles proved difficult.
One important application of nanoparticles that was explored here is in catalyzing organic reactions. Because of the fast oxidation of copper nanoparticles, silver nanoparticles were synthesized photochemically on different supports including TiO2 and hydrotalcite (HTC). Their catalytic efficiency was tested using alcohol oxidations. Different silver nanoparticle shapes (decahedra and plates) were compared with the spheres to see the different catalytic efficiencies.
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Kutsevol, N., T. Bezugla, M. Rawiso, M. Bezuglyi, and V. Chumachenko. "In Situ Synthesis of Silver Nanoparticles in Linear and Branched Polymer Matrices." Thesis, Sumy State University, 2012. http://essuir.sumdu.edu.ua/handle/123456789/34840.
Full textAbstract:
Silver nanoparticles were synthesized in linear and branched polymer matrices at different temperatures. The template role of the host linear Polyacrylamide and star-like copolymer Dextran-graft-Polyacrylamide for in situ synthesis of nanoparticles was studied by TEM, UV-Vis spectrophotometry and
Dynamic light scattering. It was shown that the internal structure of polymers in solution drastically affects the process of Ag NPs formation. Branched polymer matrix allows to obtain a stable silver colloid
even at high temperature when the linear PAA matrix is not efficient.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/34840
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Lei, Guangyin. "Synthesis of Nano-Silver Colloids and Their Anti-Microbial Effects." Thesis, Virginia Tech, 2007. http://hdl.handle.net/10919/31915.
Full textAbstract:
The antimicrobial effects of silver nanoparticles were studied. Silver nanoparticles were synthesized through wet chemistry method, and were dispersed in aqueous suspension. With nanoscale silica particles served as heterogeneous nucleation sites, silver nanoparticles were formed anchoring on the silica surface. Suspensions were found to be stable at high silver concentrations as well as over a broad pH range. By varying the processing conditions, diameter of the silver nanoparticles could be controlled between ~2 nm to ~25 nm. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to reveal the formation and the corresponding morphology of the silver-silica coupling nanoparticles. Ultra-violet visible (UV-vis) scanning spectrophotometer was used to detecting the distinct absorption spectrum of silver nanoparticles. The antimicrobial activities of these silver-silica coupling nanoparticles were investigated. E. coli and S aureus were used as representatives of Gram-negative and Gram-positive bacteria, respectively. Bacteriological tests showed either bacterial growth inhibition or cell death occurred, corresponding to different concentrations of silver nanoparticles and the type of bacteria that were testing on. Fluorescent microscopic images were also provided to confirm the bacterial viability after several hoursâ treatment with silver nanoparticles.<br>Master of Science
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Paluri, Sesha Lakshmi Arathi. "Synthesis, Characterization and Manipulation of Creighton Silver Nanoparticles for Future Cytotoxicity Studies." Wright State University / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=wright1326576201.
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Joshi, Deepti. "Laser-assisted synthesis of gold and silver nanoparticles and spectroscopic study of their interaction with protein." Thesis, IIT Delhi, 2016. http://localhost:8080/iit/handle/2074/6995.
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LIU, BOYANG. "SYNTHESIS AND ASSEMBLY OF CUBIC NANOPARTICLES WITHIN A SPHERICAL CONFINEMENT AT VARYING TEMPERATURES." University of Akron / OhioLINK, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=akron1619430294520583.
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Cabala, Guillermo Van Erven. "Desenvolvimento de filtros cer?micos impregnados com nanopart?culas de prata para desinfec??o de ?gua pot?vel." Universidade Federal do Rio Grande do Norte, 2013. http://repositorio.ufrn.br:8080/jspui/handle/123456789/12843.
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Previous issue date: 2013-04-19<br>Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior<br>Brazil has vast amounts of hydric resources, whose quality has been deteriorating due to pollutant dumping. Household waste disposal is one of the main sources of water pollution, stimulating bacteria proliferation and introducing microorganisms, including those from fecal matter. Conventional water disinfection methods are a solution, but on the downside, they lead to the formation byproducts hazardous to human health. In this study, aiming to develop bactericidal filters for the disinfection of drinking water; silver nanoparticles were deposited on alumina foams through three routes: sputtering DC, dip coating and in situ chemical reduction of silver nitrate. The depositions were characterized through X-ray diffraction, scanning electron microscopy and EDS element mapping. The influence of the depositions on permeability and mechanical properties of the ceramic foams was assessed and, in sequence, a preliminary antibacterial efficiency analysis was carried out. Characterization results indicate that the chemical reduction routes were efficient in depositing homogeneously distributed silver particles and that the concentration of the metallic precursor salt affects size and morphology of the particles. The antibacterial efficiency analysis indicates that the chemical reduction filters have potential for water disinfection<br>O Brasil apresenta vastos recursos h?dricos cuja qualidade tem deteriorado como consequ?ncia do despejo de poluentes. A descarga de res?duos domiciliares ? uma das principais fontes de polui??o dos mananciais, estimulando a prolifera??o de bact?rias e inserindo outros microrganismos, incluindo aqueles oriundos de mat?ria fecal. O tratamento ou purifica??o da ?gua residencial se apresenta como solu??o, entretanto os m?todos tradicionais de desinfec??o da ?gua t?m sido contestados por conduzirem ? forma??o de subst?ncias prejudiciais ? sa?de humana. No presente estudo, com o intuito de desenvolver filtros com a??o bactericida para desinfec??o de ?gua para consumo humano, nanopart?culas de prata foram depositadas em s?lidos celulares cer?micos de alumina atrav?s de tr?s rotas distintas: sputtering DC, dip coating e redu??o qu?mica in loco de nitrato de prata. As deposi??es foram caracterizadas por difra??o de raios-X (DRX), microscopia eletr?nica de varredura (MEV) e mapeamento por espectrometria por dispers?o de energia de raios-X (EDS). A influ?ncia da deposi??o sobre as propriedades mec?nicas e de permeabilidade do s?lido celular cer?mico foi avaliada, sendo posteriormente executada uma an?lise preliminar de efici?ncia antibacteriana. Os resultados da caracteriza??o indicam que as rotas via redu??o qu?mica in loco de nitrato de prata foram eficientes na deposi??o de part?culas homogeneamente distribu?das e que a concentra??o do precursor met?lico afeta o tamanho e a morfologia das part?culas. A an?lise de efici?ncia antibacteriana indica que os filtros confeccionados por redu??o qu?mica apresentam potencial para a desinfec??o de ?gua para consumo humano
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Samsodien, Mogammad Luqmaan. "Nanoparticles for use in imaging, catalysis and phthalocyanine synthesis." University of the Western Cape, 2018. http://hdl.handle.net/11394/6446.
Full textAbstract:
Magister Scientiae - MSc (Chemistry)<br>Nanoscience and nanotechnology are known to be interdisciplinary, crossing and combining
various fields and disciplines in pursuit of desirable outcomes. This has brought about
applications of nanoscience and nanotechnology in multitudes of industries, spanning from the
health, pharmaceutical to industrial industry. Within the health industry, the medical field has
seen much advancement through nanoscience and nanotechnology. The importance of finding
cures to diseases is top priorities within the medical field, along with advancements in
understanding and diagnosing diseases. Due to these outcomes, we see the emergence of imaging
techniques playing a crucial role. The work covered in this thesis looks at a prospective
luminescent agent applicable in the medical field for bio-imaging, but also at a possible
phthalocyanine sensitizer for treatment of cancer through photodynamic therapy. Another area
where nanoscience and nanotechnology are found is in industry, where nanoparticles are utilised
as catalysts in many synthetic reactions. Highly desirable catalysts in industry are those involved
in oxidative reactions where we explore a metal nanoparticle catalyst within this work.
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Kashmery, Heba Abbas. "Exploration of a template-directed approach for the synthesis of silver nanoparticles." Thesis, University of Strathclyde, 2015. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=25770.
Full textAbstract:
The aim of this thesis is to develop a facile one-pot synthesis of silver nanoparticles (AgNPs) using Tollens' reagent as a silver source. The project focuses on the preparation of a series of sugar triazole ligands to template the formation of monodisperse AgNPs in a size- and shape-controlled manner. Chapter 1 introduces the optical properties of metal nanoparticles and the common methods for the preparation of AgNPs, highlighting the limitations of typical methods and the motivations of this research. Chapter 2 describes the influence of the structural parameters of these sugar triazole ligands (i.e., sugar units, triazole and aromatic core) on the size, shape, stability and dispersity of AgNPs. The work highlights how the Ag(I) binding affinity of these ligands is a key parameter to tune the size and shape of the resultant AgNPs formed. Weaker Ag(I) binding ligands with a phloroglucinol core form monodisperse angular AgNPs over a range of sizes (12 ± 1 nm - 33 ± 7 nm), whereas resorcinol core triazole ligands exhibiting a higher Ag(I) binding affinity produce monodisperse spherical AgNPs of a single size (8 ± 5 nm). Chapter 3 describes the synthesis of AgNPs using sugar triazole ligands and Tollens' reagent using silver trifluoroacetate to investigate the counter-ion effect of silver salts on the size and the morphology of formed AgNPs. This salt produces AgNPs with similar shapes and sizes compared to that formed using silver nitrate. Chapter 4 describes the synthesis of PEG-functionalised sugar triazoles bearing PEG groups to investigate their effects on the formation of AgNPs. This work identifies the southernmost triazole as a modular site to tune the size and shape of AgNPs. Installation of PEG chains into the southernmost triazole ring shows a significant reduction in the Ag(I) binding affinity and produces monodisperse angular AgNPs with diameters ranging from 15 ± 4 nm to 38 ± 7 nm. The surface enhanced Raman scattering properties of formed AgNPs are also discussed. Chapter 5 describes the synthesis of sugar-modified peptides to template the synthesis of AgNPs using Tollens' reagent. Increasing the sugar units using octamer peptide produces angular and smaller AgNPs (10 ± 2 - 23 ± 2) compared to that formed using pentamir peptide (16 ± 2 - 32 ± 4). In conclusion, this thesis reports a novel template-directed triazole ligand strategy for the one-step synthesis of AgNPs in a size- and shape-controlled fashion. The mild synthetic methodology outlined in this thesis opens up new opportunities for the development of optical biosensing and imaging applications.
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Kudaibergenov, S. E., E. K. Baigaziyeva, N. N. Yesmurzayeva, Zh A. Nurakhmetova, and B. S. Selenova. "Synthesis, Characterization and Catalytic Property of Polymer Protected Gold and Silver Nanoparticles." Thesis, Sumy State University, 2013. http://essuir.sumdu.edu.ua/handle/123456789/35096.
Full textAbstract:
Gold (AuNPs) and silver (AgNPs) nanoparticles protected by hydrophilic polymers were prepared by “one-pot” synthetic protocol. Absorption spectra, size, morphology and structure of obtained nanoparticles were investigated by UV-Vis spectroscopy, dynamic light scattering (DLS), and transmission electron mi-croscopy (TEM). The catalytic activity of polymer-protected AuNPs and AgNPs supported on the surface of aluminum oxide was evaluated with respect to decomposition of hydrogen peroxide.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/35096
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Zaker, Yeakub. "Facile Size Focusing Synthesis of Silver Nanoparticles Capped with Aliphatic Thiol Ligands." University of Toledo / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1480456850511426.
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Zhang, Huanjun. "Ag/TiO[subscript 2] nanocomposites : synthesis, characterizations and applications /." View abstract or full-text, 2009. http://library.ust.hk/cgi/db/thesis.pl?CBME%202009%20ZHANGH.
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Kanbertay, Elif. "Synthesis Of Dopamine Functionalized Silver Nanoparticles Together With Possible Interactions Between Silver And Dopamine Having Different Oxidation Forms." Master's thesis, METU, 2013. http://etd.lib.metu.edu.tr/upload/12615658/index.pdf.
Full textAbstract:
Dopamine is a neurotransmitter found in central nerve system which has a vital role for human health. Dopamine oxidation in body is an important issue since it may form reactive metabolites which can be toxic to the cell. Surface-enhanced Raman scattering (SERS) is currently recognized as one of the most sensitive spectroscopic tools, which can be exploited for ultrasensitive chemical and biological detection, addition to providing structural information on the systems of interest. SERS of dopamine displays three strong bands at 1269, 1331 and 1479 cm-1. These bands are the signature of dopamine molecule. The most intense band at 1479 cm-1 is contributed mainly from stretching of the carbon-carbon bond to which the oxygens are attached. A bidentate silver-dopamine complex or in general bidentate metal-dopamine complex formation is required for the SERS detection of dopamine and other catecholamines. In other words, for acquiring the characteristic dopamine SERS signature, both of the catechol oxygens should take a part in the adsorption of dopamine to the silver metal surface which is used as a SERS substrate. Therefore, the reactivity of different oxidation forms of dopamine for the formation of bidentate silver-dopamine complex was investigated by obtaining their SERS spectra and following the characteristic C-C ring vibration at 1479 cm-1. Dopamine oxidation was carried out electrochemically, utilizing platinum and silver electrodes as working electrode. Oxidation products formed were identified with UV-vis Spectrometer. Also, silver metal ions were used to oxidize dopamine, leading to formation silver nanoparticles. Dopamine functionalized silver nanoparticles were characterized by Scanning Electron Microscope, Transmission Electron Microscope, UV-vis Spectrometer. Surface- enhanced Raman spectra of polydopamine on the surface of synthesized silver nanoparticles and the electrodeposited dopamine on the porous surface of silver electrode were also obtained.
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Lin, Wing-shan, and 林穎珊. "Synthesis and biological studies of anti-cancer rhodium(II, II) carboxylates, anti-inflammatory silver(I) thiourea and microbially fabricated silver nanoparticles." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2014. http://hdl.handle.net/10722/206649.
Full textAbstract:
Discovery of cisplatin as an effective anticancer agent has stimulated the development of metal based medicine. The recent advances in research on platinum, ruthenium and gold complexes have received much attention in medicinal chemistry, and studies of other less explored metal complexes may reveal alternative mode of mechanism as novel therapeutic agents. A series of dirhodium(II,II) complexes with carboxylate and carboxamidate ligands and thiourea complexes of coinage metals have been prepared in this study. Their biological activities and mechanisms of action have been studied.
Dirhodium(II,II) carboxylate complexes with variations of alkyl and benzoyl side chains were synthesized and displayed remarkable cytotoxicities to cancer cells with potency down to submicromolar level. The cytotoxicities of rhodium complexes were found to significantly correlate with the cellular uptake of the rhodium complexes. As revealed by oligonucleotide microarray and bioinformatic analysis, the mode of action of the rhodium carboxylate complexes are highly similar to that of a proteasome inhibitor. Further cellular and biochemical studies showed that rhodium carboxylate complexes induced an accumulation of ubiquitinated proteins, inhibited the proteolytic activities of purified 20S proteasome and proteasomal deubiquitinating enzyme. These results corroborate that the impairment of the ubiquitin-proteasome system is linked to the cytotoxic action of rhodium carboxylate complexes.
Silver is known to be an anti-inflammatory agent for topical treatment. A silver complex of N, N’-disubstituted cyclic thiourea that is reasonably stable towards reduced glutathionewas found to potently inhibit the NF-B transcriptional activity. Treatment of cells with silver thiourea inhibited TNF-α-stimulated IκB kinase activity, IκBα phosphorylation and degradation, nuclear translocation of NF-κB p65 and eventually the stimulated gene expression of inflammatory cytokines. Suppression of IκB kinase activity was associated with modification of sensitive cysteine residues and disruption of IκB kinase assembly. These data demonstrated that the inhibitory properties of Ag+ ions on an anti-inflammatory and anti-cancer drug target could be effectively delivered via the thiourea ligand.
Silver is also an antimicrobial metal, and this study was also extended to understand the silver-bacteria interaction using a silver resistant bacteria as a model. Many silver resistant bacteria often produce considerable amount of silver particles when exposed to high concentrations of silver salts but the mechanism of biosynthesis is not well understood. A silver resistant E. coli that displays active silver efflux was shown to synthesize zero-valent silver nanoparticles in the periplasmic space through reduction of silver ions under anaerobic conditions. As the microbial c-type cytochromes are known to mediate respiratory metal reduction, their role in the biosynthesis of silver nanoparticles was examined. A deletion mutant of the cytoplasmic membrane-anchored tetra-heme c-type cytochrome subunit of periplasmic nitrate reductase (NapC) showed marked reduction of accumulation of silver nanoparticles. This study identified a molecular mechanism of biosynthesis of silver nanoparticles that may have implication in bioenvironmental processes and synthetic biology of metal nanomaterials.<br>published_or_final_version<br>Chemistry<br>Doctoral<br>Doctor of Philosophy