Optically Transparent Diamond Electrodes for Chemical Analysis

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ABSTRACT CHE-0616730 Swain/Michigan StateThis research project funded by the Analytical and Surface Chemistry program seeks to investigate the electrical, electrochemical and optical properties of boron-doped diamond thin films with the goal of developing a new type of optically transparent electrode that can be used for transmission spectroelectrochemical measurements in both the UV/Visible and infrared regions of the electromagnetic spectrum. Professor Greg M. Swain and his group at Michigan State University are studying several different electrode architectures, including free-standing films and thin films deposited on transparent substrates like quartz and silicon. They seek to develop a low frequency IR ( 1000 cm-1) spectroelectrochemical method that can be used to study redox-linked metal-ligand modes in metalloproteins and enzymes. Recent advances in protein film voltammetry along with spectroelectrochemical measurements using IR-transparent diamond electrodes will be employed to gain insight into the mechanistic details of radical-producing metalloproteins and enzymes. Redox-linked metal-substrate and metal-cofactor normal modes will be probed by electrochemical difference spectroelectrochemical techniques with the goal of understanding how these structural changes correlate with biological function. The focus initially is on method development using well-characterized inorganic/organic redox systems and soluble redox proteins (e.g., myoglobin), but will be extended to representatives of the metalloradical enzyme class (e.g., cytochrome c oxidase (CcO)). A second task involves coupling an optically transparent diamond electrode in the UV/Vis with microchip capillary electrophoresis to enable multiple detection strategies (electrochemical, UV/Vis absorbance, and fluorescence) on the same device. The possibility of multiple detection schemes will facilitate high-throughput analysis and improved sample characterization. Demonstrating the method for the analysis of the sympathetic nervous system neurotransmitters norepinephrine (NE) and adenosine triphosphate (ATP), and their metabolites, is the goal. If successful, the method will be used to provide new insight into neural control mechanisms in hypertension. The chemical problems being addressed are at the interface between chemistry and biology; therefore, the undergraduate and graduate students working on the project will receive broad training in materials science, electrochemistry, separation science, optical spectroscopy, redox protein chemistry, and neurochemistry as it relates to the disease state, hypertension.