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 Electrochemical Quartz Crystal Microbalance (EQCM) was used as the main investigation tool coupled with other conventional electrochemical methods to study the electrocatalytic properties of polycrystalline Pt electrodes, including two separate projects. The first project studied the early stage of oxide film formation on the Pt surfaces and the inhibition of the catalytic properties by the oxide film. The inhibition of the fast electrode reaction of small molecules by the growth of oxide film allows those molecules to be used as probes for the nature of the oxide film. The hydrogen oxidation current, jox calculated by differencing the cyclic voltammetry currents with and without H₂ present showed a characteristic plateau-to-plateau profile, which implies a transition from the free Pt surface to the Pt surface completely covered by oxide film. This method allows determination of the onset potential for oxide formation and also the critical potential where a full monolayer of oxide is formed. This method applies to other fast surface reactions such as oxygen reduction reaction (ORR), and the results are enhanced by forced convection in the rotating disk electrode (RDE) experiments. The initial oxidation species was identified by charge and EQCM frequency analysis. Our results support the formation of a species with stoichiometry Pt₂O, for example, with an oxygen atom in the bridging position between two adjacent Pt atoms. In the second project, the stability of the Pt electrodes in acid media with Ag⁺ present was investigated. A substantial frequency drift (8.3 Hz cycle⁻¹, or 44 ng cm⁻² cycle⁻¹) was observed during Ag electrodeposition and stripping on the bare polycrystalline Pt surface. Cyclic voltammograms in pure HClO₄ solution showed nearly no frequency drift while the addition of 10⁻³ mol L⁻¹ Ag⁺ resulted in an immediate and characteristic frequency drift. The frequency drift appeared to be consistent with loss of material from the electrode surface and the ICP-MS detected a maximum Pt concentration of 2.3×10⁻⁶ mol L⁻¹ in solution due to Pt dissolution. The Pt concentration calculated from the EQCM frequency drift matched the ICP-MS results. This allowed the EQCM for direct investigation of Pt dissolution at different system temperatures, sweep rates, and potential ranges. The much higher rate of dissolution with Ag present than that in pure HClO₄ solution can be explained by the formation of Pt-Ag alloy during Ag underpotential deposition and the co-dissolution of Pt and Ag.