Expanding the detection of analytes by use of mediators and ligands in developing new spectroelectrochemical sensor

The concept of spectroelectrochemistry using an ATR system has been explored in our research group for a number of years. To date the concept of achieving a sensor with multimodes of selectivity has been demonstrated with potassium ferrocyanide, Ru(bipy)32+, and Ru(CN)4 -. This sensor has three modes of selectivity: applied potential, chosen wavelength and chemically selective film. In this sensor device in order for an analyte to be detected it must first partition into the sensing film, be electroactive at the applied potential, and have a change in absorbance at the wavelength of light.;In the first part of my research, I evaluated expanding the sensor concept to detect an analyte which itself did not undergo electron transfer at the electrode and which is not optically monitored. To explore this system a mediated electrode reaction was used in which the mediator undergoes spectroelectrochemical modulation. The analyte is detected indirectly by its effect on the optical signal from the modulated mediator. The system explored was that of ascorbic acid as the analyte and Ru(bipy)32+ as the mediator using a composite film of Nafion-SiO2. Factors such as scan rate, concentration of mediator in the film, film composition and thickness, and analyte solution pH was studied to achieve optimal sensor conditions.;This concept can be further expanded in developing a biosensor. This concept was explored using mediated detection and the addition of an enzyme. Investigation into to developing a more selective glucose biosensor was explored as well as several different mediators for this reaction.;The final part of my research was development of a sensor capable of determining the concentration of technetium in various chemical forms (mainly pertechnetate) in the vadose zone and ground water at the U.S. DOE Hanford site. In this research Re and Mn are being used as a chemical surrogate for radioactive Tc. The chemical and electrochemical reduction of ReO4 -, and MnO4- was explored as well as its reaction with several different classes of ligands. Both the electrochemical and optical properties were studied.