Spectroelectrochemical sensing based on multimode selectivity simultaneously achievable in a single device. 5. Simulation of sensor response for different excitation potential waveforms
Af. Slaterbeck et al., Spectroelectrochemical sensing based on multimode selectivity simultaneously achievable in a single device. 5. Simulation of sensor response for different excitation potential waveforms, ANALYT CHEM, 72(22), 2000, pp. 5567-5575
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.