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.

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.

Porous antimony-doped tin oxide (ATO) cathodes formed by supercritical CO2 (SCCO2) treatment for silver electro-deposition devices were proposed. The porous ATO cathode with a thickness of 1.4£gm was formed by coating the nano-particle ATO solution on ITO glass. The porous structure of the cathodes was obtained by applying SCCO2 treatment at 60oC on the spin-coated ATO thin films. A layer of electrolyte(formed by AgI, NaI and DMSO)was enclosed by two electrodes to to form a so-called¡§sandwich¡¨ structure. After the fabrication process, white paint was spray on the back side of the glass substrate. Due to the thickness of the ATO cathode, the cathode is observed to be transparent during the oxidation process. The Black state of the device was observed during the reduction of silver molecules which were anchored onto the surface of the 1.4£gm thick ATO cathode. The average transmission contrast ratio of 4.4 was obtained in visible spectrum at a driving voltage of 1V and a saturation current density of 3.1 mA/cm2. In addition to that, 0.5 cm by 0.5 cm device with 65£gm cell gap and 0.08 M electrolyte concentration, an electrochromic switching time of 3.7 seconds was achieved .

Thesis (M.Ch.E.)--University of Delaware, 2009. / Principal faculty advisor: Mark A. Barteau, Dept. of Chemical Engineering. Includes bibliographical references.

Silver nanoparticles (AgNPs) have gained much popularity in consumer products due to their strong antimicrobial ability. The majority of research concerning the biological effects of AgNPs has been limited to humans, mammals and freshwater organisms. Marine organisms, especially invertebrates, have been studied to a lesser extent. The objective of this thesis was to understand the effects of AgNPs on the marine benthic invertebrates. Specifically, we focused on the acute and sub-lethal toxicity of two AgNPs (Oleic acid coated AgNP (OAgNP) and Polyvinylpyrrolidone coated AgNP (PAgNP)) on marine invertebrate larvae across three phyla (i.e. the barnacle Balanus amphitrite, the limpet Crepidula onyx and the polychaete Hydroides elegans) in terms of mortality, growth, development and metamorphosis. Bioaccumulation and biodistribution of silver, as well as apoptosis induction were also investigated. To distinguish the toxic effects derived from nano-silver and aqueous form of silver, larvae were also exposed to silver nitrate (SN) in parallel. In the acute toxicity test, larvae were exposed to OAgNPs and PAgNPs for 48 hours, and the concentration leading to 10 % mortality (〖LC〗_10) were determined and compared. The results indicated that B. amphitrite and H. elegans were more sensitive to OAgNPs (〖LC〗_10: 0.138 and 2.63 × 〖10〗^(-4) μμg L-1, respectively) than PAgNPs (〖LC〗_10: 0.502 and 0.317 μμg L^(-1), respectively). In contrast, C. onyx was more susceptible to PAgNPs (LC10: 38.5 μμg L^(-1)) than OAgNPs (〖LC〗_10: 467 μμg L^(-1)). Among the three taxonomic groups, C. onyx was most tolerant of AgNPs, following by B. amphitrite and H. elegans. The sub-lethal effect of AgNPs resulted in a significant retardation in growth and development, and the reduction of settlement rate of all three species tested. In particular, the settlement rate of H. elegans was significantly lower in AgNPs treatment than in SN treatment, suggesting that toxicity of AgNPs might not be solely evoked by the release of silver ion (Ag+) into the test solution. The three species took up and accumulated silver efficiently from all forms. Importantly, AgNP aggregates were found along the digestive tract of C. onyx and the TEM images further confirmed that AgNPs were able to move across the plasma membrane. In addition, TUNEL assay indicated that AgNPs could induce apoptosis in B. amphitrite and C. onyx. In view of the very low number of detected apoptotic cells and the random occurrence of cell death found, AgNP-induced apoptosis does not appear to be the major toxicity mechanism in causing delayed growth and settlement failure. Unlike the results revealed from acute toxicity test, surface coatings did not affect the sub-lethal toxicity of AgNPs. This research clearly demonstrated that AgNPs exerted toxic effects in a speciesspecific manner, and long-term exposure of AgNPs might allow bioaccumulation of silver, induce apoptosis, and affect growth, development and recruitment of marine invertebrates. This study also highlighted the possibility that toxicity of AgNPs might be mediated through toxic Ag+ as well as the novel modalities of AgNPs. / published_or_final_version / Biological Sciences / Master / Master of Philosophy

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Silver was evaluated as disinfectant to maintain water quality in water distribution system. It was used to inhibit growth of two opportunistic bacteria in planktonik form and in biofilm formation in Robbins devices with stainless steel and PVC surfaces. The results of this work show that silver is a potential secondary disinfectant to be used in water distribution systems

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