Spectroelectrochemical sensing based on multimode selectivity simultaneously achievable in a single device. 5. Simulation of sensor response for different excitation potential waveforms

The simulation of the optical response in spectroelectrochemical sensing ha s been investigated. The sensor consists of a sensing film coated on an opt ically transparent electrode (OTE), The mode of detection is attenuated tot al reflection. Only species that partition into the sensing film, undergo e lectrochemistry at the potentials applied to the OTE, and have changes in t heir absorbance at the wavelength of light propagated within the glass subs trate of the OTE can be sensed. A fundamental question arises regarding the excitation potential waveforms employed to initiate the electrochemical ch anges observed, Historically, selection has been based solely upon the effe ctiveness of the waveform to quickly electrolyte any analyte observable by the optical detection method employed. In this report, additional requireme nts by which the waveform should be selected for use in a remote sensing co nfiguration are discussed. The effectiveness of explicit finite difference simulation as a tool for investigating the applicability of three different excitation potential waveforms (square, triangle, sinusoid) is demonstrate d. The simulated response is compared to experimental results obtained from a prototype sensing platform consisting of an indium tin oxide OTE coated with a cation-selective, sol-gel-derived Nafion composite film designed for the detection of a model analyte, tris(2,2'-bipyridyl)ruthenium(II) chlori de. Using a diffusion coefficient determined from experimental data(5.8 x 1 0(-11) cm(2) s for 5 x 10(-6) M Ru(bipy)(3)(2+)), the simulator program was able to accurately predict the magnitude of the absorbance change for each potential waveform (0.497 for square, 0.403 for triangular, and 0.421 for sinusoid), but underestimated the number of cycles required to approach ste ady state. The simulator program predicted 2 (square), 3 (triangle), and 5 cycles (sinusoid), while 5 (square), 15 (triangle), and 10 (sinusoid) cycle s were observed experimentally.