L-glutamate plays a vital role in central nervous system. It is a neurotransmitterassociated with several neurological disorders like Parkinson's disease, epilepsyand stroke. Continuous and fast monitoring of this neurotransmitter has become amajor concern for neuroscientists throughout the world. A simple, sensitive, and reliable L-glutamate microsensor with short responsetime has been developed using ceramic-based microelectrode arrays with platinum recording sites. The electrodes were modified by electrodeposition of Platinum black (Pt-black) to detect hydrogen peroxide (H2O2) which was produced by enzymatic reactions of glutamate oxidase immobilized on the electrode surface. Modification of Pt electrodes with Pt-black has been adoptedbecause the microscale roughness of Pt-black increases the effective surface area of the electrode and promotes efficiency of H2O2 electro-oxidation. The modified Pt recording sites were coated with m-phenylenediamine (mPD) and L-glutamate oxidase (L-GluOx). mPD acts as an barrier for extracellular interferents such as ascorbic acid and dopamine, thus increasing the selectivity of electrode for Glutamate (Glu). This modified microsensor was highly sensitive to H2O2(686.3??156.48 ??AmM-1cm-2), and Glutamate (492.2??112.67 ??AmM-1cm-2) at 700mV versus Ag/AgCl reference. Deposition of Pt nano-particles on recording sites enhanced the sensitivity to H2O2 by 2 times and the sensitivity to glutamate by 1.5 times.

The purpose of this work is to develop and evaluate electroding methods for a reverse osmosis (RO) membrane that results in an in situ sensor able to detect RO membrane protein fouling. Four electroding techniques were explored: i) gold exchange-reduction, ii) encapsulated carbon grease, iii) "direct assembly process" (DAP), and iv) platinized polymer graft. The novel platinized polymer graft method involves chemically modifying the RO membrane surface to facilitate platinization based on the hypothesis that deposition of foulant on the platinized surface will affect platinum/foulant/solution interfacial regions, thus sensor impedance. Platinized polymer graft sensors were shown to be sensitive to protein fouling. Electrodes were characterized by their electrical properties, SEM and XPS. Assembled sensors were evaluated for sensitivity to electrolyte concentration and protein fouling. Micrographs showed coating layers and pre-soak solution influence gold exchange-reduction electrode formation. High surface resistance makes gold exchange-reduction an unsuitable method. Concentration sensitivity experiments showed carbon grease and DAP electroding methods produce unusable sensors. Carbon grease sensors have time-dependent impedance response due to electrolyte diffusion within the micro-porous polysulfone support. DAP electroded sensors proved quite fragile upon hydration; their impedance response is transient and lacks predictable trends with changes in concentration. A parametric study of the platinized polymer graft method shows amount of grafted monomer correlates to grafting time, and deposited platinum is a function of exchange-reduction repetitions and amount of grafted monomer. Platinized polymer graft sensors were fouled in both dead-end and cross-flow RO systems, and their impedance trends, while varying between sensors, indicate protein-fouling sensitivity. / Master of Science

No description available.