Alternating Current Voltammetry at a Bipolar Electrode with Smartphone Luminescence Imaging for Point-of-Need Sensing

Bipolar electrochemistry allows for facile arraying of tens to thousands of electrochemical sensors that can be controlled by a single pair of driving electrodes. While bipolar electrodes (BPEs) have been applied to many sensing motifs, their sensitivity and specificity are limited by the lack of diversity in voltammetric methods that have been developed for these wireless electrodes. In this study, electrochemiluminescence (ECL) from the co-oxidation of Ru(bpy)(3)(2+) and tripropylamine (TPA) is evaluated as a reporting reaction for alternating current voltammetry (ACV) on a BPE at frequencies of 1.0 Hz and 5.0 Hz. We observe sinusoidal alternating luminescence that follows a similar trend to that of the simultaneously monitored current - a plot of the amplitude versus potential approximates a bell-shaped curve. Notably, the luminescent response to the current is detected with a smartphone, which underscores the portability of this method. The fidelity of the transduced signal is determined both in a traditional 3-electrode configuration and at a BPE. These experimental results indicate that the alternating luminescence follows the current sufficiently for quantitative sensing but is diminished at higher frequencies and peaks at a shifted potential. These results are significant because they demonstrate the potential for application of ACV at BPE arrays for multiplexed point-of-need sensors and provide guidance for the selection of reporting reactions in this context.