| A mathematical model was developed to simulate the pulse clamp method for neural stimulation at the electrode/solution interface. Numerical results identified the recoverable and unrecoverable charges to be capacitive and faradaic, respectively, and indicated that during the open-circuit delay the capacitor discharges via faradaic reactions.; The electronic properties of electrodeposited RuO, films, an electrode material that displays ideal properties for this type of application, have been examined in situ by Ru LIII and LII -edge X-ray absorption near edge structure, allowing assignment of the main voltammetric peak to a redox couple involving formally Ru3+ and Ru4+ sites.; The effects of the applied potential on the interfacial capacity of lipid bilayers were examined using a mathematical model which accounts for the degree of ionization of surface functional groups, providing support to the view that the bilayer capacitance is largely independent of the applied potential in conditions of relevance to biological systems.; Insight into the chemistry of biological membranes was gained from attenuated total reflection (ATR) infrared studies of sequentially self-assembled bilayers supported on an ATR Ge crystal. Direct evidence for the success of this approach was obtained from the observed acid-base characteristics of carboxylic functionalized outer layers. Also investigated were the binding properties of such bilayers toward biologically active Cd2+ as a function of pH , and of sulfonate functionalized SAB toward solutions containing Cd2+, Fe3+ and Fe2+.; In related studies, the mode of binding of nitric oxide, a recently identified neurotransmitter, to Fe phthalocyanine, a species closely related to the active site of certain enzymes, has been elucidated from the analysis of the in situ Fe K-edge extended X-ray absorption fine structure (XAFS) of the material adsorbed on the surface of a high area carbon electrode.; Exploratory research was also conducted in the general area of in situ spectroscopy, including theoretical aspects of the quantitative analysis of potential modulation spectroelectrochemical techniques, in good agreement with experimental results for both absorption and probe-beam deflection-type experiments.; Progress was also made toward implementation of acoustic streaming to produce hydrodynamic flow patterns similar to those found for more conventional forced convection geometries but without moving parts, as well as acquisition of in situ electron yield XAFS from continuously emersed electrodes. |
