Thesis (Ph. D.)--Ohio State University, 2006. / Title from first page of PDF file. Includes bibliographical references (p. 154-162).

[Introduction, p. 3] The solubilities of the silver halides cannot be determined by the conventional methods of analytical chemistry because they are too sparingly soluble (of the order 1 x 10⁻⁵ to 1 x 10⁻⁶ g . equiv./1. at 25°C.) However, electrical, and to a lesser extent optical methods, are admirably suited because of their greater sensitivity. The conductometric and potentiometric methods are the two most important electrical techniques for the measurement of the solubilities of sparingly soluble salts, and are the ones employed in this research. There are large discrepancies between the published values for the solubility of silver chloride. Results obtained by the conductometric and potentiometric methods disagree. In addition, figures quoted by independent authors using the same method differ by as much as 15%.

Diabetes is a disease that causes many complications in human normal function. This disease represents the sixth-leading cause of death in USA. Prevention of diabetes-related complications can be accomplished through tight control of glucose levels in blood. In the last decades many different glucose sensors have been developed, however, none of them are really non invasive. Herein, we present the study of the application of gold and silver nanoparticles with different shapes and aspect ratios to detect glucose traces in human fluids such as tears and sweat. This is to our knowledge the first truly non invasive glucose optical sensor, with extraordinary limit of detection and selectivity. The best proven nanoparticles for this application were gold nanospheres. Gold nanospheres were synthesized using chloroauric acid tri-hydrated (HAuCl4.3H2O) in solution, in the presence of glucose and ammonia hydroxide. The higher the glucose concentration, the higher the number of nanoparticles generated, thus the higher the extinction efficiency of the solution. The linear dependence of the extinction efficiency of the gold nanoparticles solution with glucose concentration makes of this new sensor suitable for direct applications in biomedical sensing. Our approach is based on the well known Tollens test.

The aim of this study is to examine the possibility of calculating the total weight of coins in poorly documented Viking Age silver hoards found on Gotland. A method for calculating the total weight of the silver coins in the hoards, and thus the weight relationship between minted and un-minted silver, would facilitate further and deeper studies using the hoards from Gotland. The method will be based on the average coin weights obtained from numismatic sources. Two calculations, one of Arabic coins and another with mixed coin, is attempted. Apart from the calculations of the Viking Age coins, earlier studies of the relation between silver coins and silver object will be discussed in the earlier research. The different Viking Age coins in the calculation and the development of the Viking age minting will also be discussed in earlier research. The result of the study demonstrate that an estimated total weight could be calculated for the Arabic silver coins. Unfortunately the mixed coin hoards could not achieve a calculation that could estimate an equivalent total weight of the silver coins

A comparison of the antimicrobial efficacy of silver diamine fluoride and silver nitrate on various cariogenic bacteria: an ex vivo study By: Reham AlNajjar, D.D.S. A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science in Dentistry at Virginia Commonwealth University. Virginia Commonwealth University, 2019 Thesis Advisor: William Dahlke, D.M.D., Associate Professor and Chair of Pediatric Dentistry, School of Dentistry Purpose: The use of silver-based antimicrobials is an emerging method for the treatment of dental caries. In this study, the authors compare the efficacy of the two most prominent silver- based therapeutics, silver diamine fluoride (SDF) and silver nitrate (AgNO3), on cariogenic and non-cariogenic multispecies biofilms. Currently there is a lack of studies comparing the efficacy of SDF to AgNO3. Methods: Plaque samples from anterior and posterior tooth sites from children presenting both with early childhood caries and caries-free children were collected, pooled, and utilized to create four ex vivo biofilm systems in artificial saliva. SDF and AgNO3 were administered to these biofilms and bacterial survival was quantified and compared to untreated controls. Results: Each of the four pooled sample types was applied to plates coated in artificial saliva + 1% sucrose. Both SDF and AgNO3 were very effective against plaque derived biofilms when compared to untreated biofilms (P0.05) in the potency of each compound. Conclusions: SDF and AgNO3 significantly inhibit ex vivo cariogenic and non-cariogenic biofilms at similar levels.

No description available.

No description available.

Controlled synthesis of functional nanostructures is of paramount interest due to their novel properties and efficient functionalities. The size and morphology of each particle in the nanoscale contribute to their optical and electronic properties. Also, the collective arrangement of these nanostructures in 3D space maximizes active sites available for the cost-effective catalysis. Recent advances in the field show a vast range of nanostructures with unique designs that affect their catalytic properties. In this dissertation, utilizing silver halides as a unique platform to develop high-performance catalysts were discussed with their respective synthesis strategies, structural evolution, and structure-related properties. Initially, we synthesized well-defined silver chlorobromide (AgCl0.5Br0.5) nanostructures investigating the effects of various reaction parameters on the synthesis. Simple reaction parameters were overlooked to gain additional controllability on determining the morphology of the nanocrystals regardless of the composition. Thus, the influence of the size and exposed surface facets was investigated towards photocatalytic activity performing methylene blue degradation on AgCl0.5Br0.5 with different sizes and morphologies, under visible light. Then, the ability to use these AgCl0.5Br0.5 nanocubes were investigated as a reactive and sacrificial template for the synthesis of nanoplates and nanoshells. As an example, fast precipitation reaction between Ag+ and benzenethiol (BT–) results in an uncontrollable growth leading to aggregated structures. The low solubility and the planer surfaces of the silver halide cubes were utilized to reduce the reaction rate and promote the growth of layered AgBT as plates, which can be organized into hollow nanostructures. Time-dependent microscopic and spectroscopic measurements showed the structural evolution and associated kinetics of the conversions. Developing a comprehensive understanding enabled generalizing the procedure to synthesize other silver-based hollow nanostructures. Mechanistic studies showed two different hollowing mechanisms involving, that depends on the anion being exchanged. The degree of nucleation and the crystal structure of silver-sulfur compounds determined the relative diffusion of ions leading to their overall size and morphology. The hollow morphology was shown to have higher stability with a large surface area relative to its aggregated solid counterpart. Next, highly porous Ag nanostructures were synthesized electrochemically, using silver thiolate nanocages. High porosity and their arrangement as plates enhanced available active sites and mass transport for CO2 electroreduction. Furthermore, the strategy was extended to design bimetallic nanostructures with enhanced bimetallic boundaries where selectivity of ethanol formation from CO2 electroreduction can be increased. Overall, the study explores the novel approaches to utilize chemical and physical properties of silver halides for various material designs that determines their enhanced performance. / Chemistry

This research was undertaken to study the suitable physico-chemical conditions for the selective recovery of gold and silver from simulated thiosulfate leach liquors containing copper, gold or silver, ammonia and thiosulfate using three anion exchange resins. In particular, the effect of chemical variables such as thiosulfate, cupric ion and ammonia concentrations and the solution potential of the system on the batch loading of silver and gold onto the resins have been investigated in detail. Pourbaix diagrams have been constructed to understand the stability of this complex system under various Eh and pH conditions. The experimental results indicate that IRA-400 resin has the highest capacity for both silver and gold compared to IRA-68 and IRA-94. All the three resins investigated are not selective to silver and gold over copper. The elution studies using ammonium thiosulfate solutions have revealed that selective elution of silver from copper is not possible, while some selectivity can be achieved between gold and copper. (Abstract shortened with permission of author.)

Master of Science / Department of Biology / Peter P. Wong / Contamination of water with various disease causing agents such as bacteria and viruses leads to 4 billion cases of diarrheal disease and 1.8 million deaths per year worldwide. The World Health Organization estimates that 94% of these cases can be prevented by increasing the availability of clean and safe water to those at risk. They also claim that 1.1 billion individuals worldwide do not have access to clean water sources, and suggest the best way to improve this situation is to increase household water treatment and safe storage (HWTS). HWTS can dramatically improve water quality, leading to a significant reduction in diarrheal disease. Being able to produce a small and inexpensive device that can be used in a household to improve water quality will significantly aid in preventing diarrheal disease. Water purification systems have been manufactured in the past in order to turn potentially disease causing water into safe drinking water. The metal iodine has been used in some of these systems. However, iodine is known to leach off and become part of the drinking water, which can lead to non-infectious diseases such as hyperthyroidism. This project shows how the development of new water purification systems utilizing silver and other heavy metal nanoparticles may be used to help purify water and have the potential to prevent diarrheal disease. Various heavy metals, including silver nitrate, magnesium oxide, brominated magnesium oxide and titanium-silicon-manganese dioxide nanoparticles, are used in conjunction with ion-exchange resins to develop a biocidal column to sanitize water. A model virus from each of the following families is used: Reoviridae (rotavirus), Picornaviridae (enterovirus), and Caliciviridae (calicivirus). This research shows not only that some of these metals can be used to purify water by inactivating viruses, but also shows the mechanism of viral inactivation. This includes protein denaturation and destruction of viral RNA.