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Thesis--University of California, Berkeley, 1961. / "UC-4 Chemistry General" -t.p. "TID-4500 (16th Ed.)" -t.p. Includes bibliographical references (p. 98-99).

[From Introduction]. The thermal decomposition of solids is characterized by the formation and growth of nuclei at sites on the surface of the solid or within the crystal lattice. Such nuclear formation is favoured by disorganisation of the crystal either by mechanical damage, or by the presence of impurities. Disorganisation results in positions which have a high thermodynamic instability. The nuclei are likely to be formed initially at the corners and the edges of the crystal since these are more prone to damage. Careful handling and storage in vacuo often leads to a large reduction in their number, while deliberate scratching of the surface facilitates their production. The number of potential sites for nuclear formation is also increased by pre-irradiation with ultra-violet light, though there are indications that a different type of nucleus may be produced. Nucleation can be facilitated by pre-irradiation with electrons, neutrons, X-rays, gamma-rays and atomic particles. The nature of the nuclei is not always clearly defined, but it is generally accepted that they are composed of solid reaction products e.g. in the decomposition of barium azide and silver oxalate, nuclei of metallic barium and silver, respectively, are formed.

This thesis is concerned with the formation and nature of intravesicular solids in chemical and biological systems. The precipitation of Ag₂O within unilamellar vesicle microvolumes is described in detail. Formation of small (<10nm) single-domain cubic Ag₂O crystallites occurs on membrane diffusion of hydroxide ions. Nucleation initiates at a single site on the inner membrane surface followed by slow crystal growth. No precipitation is observed below an extravesicular pH (pH_OUT) of <u>ca</u>. 11.0. Permeable intravesicular nitrate ions permit hydroxide influx only when a critical membrane potential gradient is surpassed. Above a pH_OUT of 11.0 rate of precipitation is dependent on the rate of crystal growth. Kinetics are firstorder with respect to intravesicular Ag(I) concentration and approximately first-order with respect to hydroxide concentration below a pH_OUT of 12.0. Solubility equilibria for intra-and extravesicular Ag₂O formation are the same. Further <u>in situ</u> intravesicular precipitation reactions are described for FeO(OH) (crystalline), FeO(OH) (amorphous), Ag₂SiO₃ (crystalline), CoSiO₃ (amorphous), Co(OH)₂ (amorphous), Ag₂S (crystalline), CoS (amorphous), and Agl (crystalline). Precipitation of single oxidation state compounds is the same in vesicle space as for normal aqueous solution. For a mixed valency state solid, Fe₃0₄, intravesicular precipitation results in an amorphous material compared with a crystalline material prepared in aqueous solution. Inclusion of pre-formed Fe₃0₄, into vesicles is of potential use as a magnetic drug carrier system and n.m.r. relaxation probe. Intravesicular silica deposition in <u>Stephenaoeca diplocostata</u> Ellis is investigated. Siliceous costal strips are found to be extremely amorphous in structure, have surfaces active to Co(II) and Fe(III) ions, and demineralise from their centre of axis. T-joins of costal strips in intact loricae are found to be joined by a connective material containing amorphous silica centred around a filamentous material of unknown composition. Sectioned material indicates that silicification possibly initiates on an organic preformer laid down within an elongated intracellular vesicle. Potential EM stains, K₅SiPhGeW₁₁0₃₉, Gd(fod)₃, and t-BuNH₃[(nC₂₂H₄₅PO₃)₂Mo₅O₁₅] interact with vesicle bilayers resulting in observable images in the EM. Binding of K₅SiPhGeW₁₁0₃₉ can be followed by ¹H n.m.r. spectroscopy . Gd(fod)₃ loaded vesicles are potential n.m.r. probes for protein - membrane binding studies.

Current and potential distribution in electrolyte cells. A cell has been built which has two Luggin capillaries mounted on micrometer drives so that the current and potential distribution around a working electrode can be measured. The current and potential distributions for a variety of electrode geometries have been measured. Experiments have been performed which show the effect of electrode geometry, current density and electrolyte conductivity on the current and potential distribution. Experimentally measured current distributions are compared with those calculated from existing theory.^8 Kinetic measurements of the electrolytic formation of argentous oxides in potassium hydroxide. Cyclic current step measurements during the Ag-Ag_2O oxidation plateau have been made. The results of measurements are very similar to those obtained from systems (Ag-Ag(NH_3)_2^+, (Fe^+2-Fe^+3) where the concentration of the electroactive species is diffusion controlled. The exchange current density, i_0, calculated from the relationship developed by Wijnen and Smit^49 decreased from 1.44 ma/cm^2 to 0.75 ma/cm^2 along the Ag-Ag_2O plateau. The changes in the ohmic resistance of the silver oxide film formed in 0.0543, 0.109, 1.09, 5.43, and 10.9 F KOH have been measured. The maximum resistance of the oxide measured in these electrolytes was 0.31, 0.28, 2.44, 5.15, and 0.16ohm-cm^2. Evidence for a proposed explanation of the changes which occurs in the oxide film resistance is presented.

Yes / Oxidative desulfurization process (ODS), enhanced with a novel metal oxide (Ag ions) as an active component over nano-zeolite that has not been reported in the literature, is used here to improve the fuel quality by removing mercaptan (as a model sulfur compound in the light naphtha). Nano-crystalline (nano-support (Nano-zeolite)) composite is prepared by Incipient Wetness Impregnation method loaded with a metal salt to obtain 0.5, 1 and 1.5% of Ag2O3 over Nano-zeolite. The new homemade nano-catalysts (Ag2O3/Nano-zeolite) prepared are characterized by Brunauer-Emmett-Teller (BET) (surface area, pore volume and pore size), X-ray Diffraction (XRD), Fourier Transform Infra Red (FTIR), and Scanning Electron Microscopy (SEM) analysis. The ODS process is then used to evaluate the performance of the catalysts for the removal of sulfur at different reaction temperatures (80-140 °C) and reaction times (30-50 min) in a batch reactor using the air as oxidant. 87.4% of sulfur removal has been achieved using 1% silver oxide loaded on Nano zeolite (1% of Ag2O3/Nano-zeolite) giving a clear indication that our newly designed catalyst is highly efficient catalyst in the removal of sulfur compound (mercaptan) from naphtha. A new mechanism of chemical reaction for sulfur removal by oxygen using the new homemade catalyst (Ag2O3/Nano-zeolite) prepared has been suggested in this study. The best kinetic model parameters of the relevant reactions are also estimated in this study using pseudo first order technique based on the experimental results.

AgCdO is one of the most widely used contact materials in the world because of its outstanding performance. Nevertheless, due to environmental considerations, it will soon be completely forbidden by European environmental directives. Therefore, finding a good substitute is of crucial importance. Electrical arc erosion plays a crucial role in the reliability and life of power switching devices. Depending on the contact material's behavior in response to an electrical arc, surface damage can induce severe changes in contact material properties that will impact the power switching device's functioning. Consequently, electrical arc effects and consequences on the contact material surface are of first importance. In this context, we have focused our research activities on the following axes. First of all, in order to better understand AgCdO (Current contact material in aerospace industry) and AgSnO₂(Potential candidate to AgCdO substitution) arc erosion behaviors, arc erosion experiments, where the power switching devices have been subjected to different numbers of arc discharges, have been realized. Further, a general macroscopic electrical contact arc erosion model valid for low and high currents was developed. To compare model results to experimental data, this model describes the complete breaking process of electrical contacts and gives the total amount of material removed after one breaking operation. In parallel, arc erosion experiments on AgCdO power switching devices have been conducted at high currents (0 -> 1000 A) in order to validate the arc erosion model. Next, using the general arc erosion model, the properties having the greatest influence on the electrical arc erosion process have been determined through simulations on silver contact material. At this stage, ab initio calculations were needed to obtain ranges of variation of certain silver contact material properties. Finally, an investigation of the trends of changing local contact material on these identified material properties was performed. This study composition of AgSnO₂was based on ab initio calculations for two different oxide compositions of AgSnO₂. These will allow us to give directions to aid the design of a good substitute for AgCdO, and therefore, to complete the main objective of this research work.

Methods for integrating enzyme systems with electrochemical reactions having applications to diagnostic sensing are described. Diagnostic tests that include biological molecules can be classified as biosensors. Existing testing methods often require trained technicians to perform, and laboratory settings with complex infrastructure. The theme of this dissertation is the development of methods that are faster, easier to use, and more applicable for non-laboratory environments. These goals are accomplished in systems using enzymatic catalysis and galvanic processes. Two biosensors with specific model pathologies have been designed and demonstrated in this study. The first assay senses a DNA fragment representing the Epstein Barr virus and uses enzyme-mediated Ag deposition over a v microfabricated chip. The chip contains a specially designed pair of electrodes in an interdigitated array (IDA). Detection is signaled by a change in the resistance between the two electrodes. The second biosensor discussed in this study is targeted towards the digestive enzyme trypsin. It is selfpowered due to its construction within an open-circuit galvanic cell. In this system, a small volume of blood serum is introduced onto the device over barriers made of protein and Al that block the anode from solution. In the presence of trypsin, the protein gel is rendered more permeable to sodium hydroxide. Adding hydroxide initiates the dissolution of the Al layer, closing the cell circuit and illuminating a light-emitting diode (LED). A relationship was observed between LED illumination time and trypsin concentration. Biosensors that utilize enzymes to generate or amplify a detectable signal are widely used, and the final project of this study uses a nanoparticle based approach to protect the catalytic activity of alkaline phosphatase (AlkP) from hostile chemicals. By incubating Au colloid with AlkP overnight and adding Ag+, core@shell nanoparticles of Au@Ag2O can be isolated that show AlkP activity. The resulting enzyme-metal composite material was analytically characterized and demonstrated greater activity in the presence of organic inhibitors relative to either wild type vi or Au colloid-associated AlkP without the Ag2O shell. The stabilization procedure is complete in one day using a onepot synthesis. This method may provide opportunities to carry out biosensing chemistry in previously incompatible chemical environments. / text

The reactions which give the products ethylene oxide, vinyl alcohol, vinyl aldehyde and vinyl radical for ethylene oxidation and the reactions which give propylene oxide, propanal, acetone and pi-allyl radical for propylene oxidation were investigated by using Density Functional Theory (DFT) method with B3LYP/LanL2DZ and 6-31g(d,p) basis sets in Gaussian&rsquo / 03 software. Silver and silver oxide were used as catalyst surface cluster models. Surface comparison was made for silver (111), (110) and (100) surfaces. Ethylene oxidation reaction was studied on these silver surfaces. Oxygen effect on ethylene oxide formation reaction was also investigated on silver (111) surface. Ethylene and propylene oxidation reactions were completed on both Ag13(111) and Ag14O9(001) surface clusters. VASP software which utilizes periodic plane wave basis sets was also used to compare trends of reactions for ethylene and propylene oxidations obtained by using Gaussian&rsquo / 03 software. According to results, silver (110) surface is more active for ethylene oxide formation than (111) and (100) surfaces. Hill site of (110) surface is much more active than hollow site of (110) surface since oxygen atom weakly adsorbed on hill site. Ethyl aldehyde and vinyl alcohol can not be formed on Ag(111) surface because of those higher activation barriers while ethylene oxide can be formed on cluster. Activation barrier for ethylene oxide formation decreases with increasing oxygen coverage on Ag(111) surface. Ethylene oxametallocycle intermediate molecule was not formed on Ag2O(001) surface while it is formed on surface oxide structure on Ag(111). Ethyl aldehyde and vinyl alcohol are not formed on silver oxide (001) surface. For propylene oxidation, &amp / #928 / -allyl formation path has the lowest activation barrier explaining why silver is not a good catalyst for the propylene oxide formation while it is a good catalyst for the ethylene oxide formation. This situation is valid for silver oxide. Propylene oxide selectivity increased in the gas phase oxidation. The qualitative relative energy trend obtained by VASP software is the similar with that of calculations obtained by using GAUSSIAN&rsquo / 03 software.