[Ru(bpy)₃]²⁺-mediated photoelectrochemical detection of bisphenol A on a molecularly imprinted polypyrrole modified SnO₂ electrode.

A ruthenium-mediated photoelectrochemical sensor was developed for the detection of BPA, using molecularly imprinted polymers (MIPs) as the recognition element, a tin oxide (SnO2) nanoparticle-modified ITO as the electrode, and a blue 473-nm LED as the excitation light source. Photoelectrochemical oxidation of BPA on SnO2 electrode was achieved by Ru(bpy)3 under the irradiation of light. It was found that BPA was oxidized by Ru(3+) species produced in the photoelectrochemical reaction, resulting in the regeneration of Ru(2+) and the concomitant photocurrent enhancement. MIPs film was prepared by electropolymerization of pyrrole on SnO2 electrode using BPA as the template. Surface morphology and properties of the as-prepared electrode were characterized by SEM, electrochemical impedance spectroscopy, and photocurrent measurement. In the presence of BPA, an enhanced photocurrent was observed, which was dependent on the amount of BPA captured on the electrode. A detection limit of 1.2 nM was obtained under the optimized conditions, with a linear range of 2-500 nM. Selectivity of the sensor was demonstrated by measuring five BPA analogs. To verify its practicality, this sensor was applied to analyze BPA spiked tap water and river water. With advantages of high sensitivity and selectivity, low-cost instrument, and facile sensor preparation procedure, this sensor is potentially suitable for the rapid monitoring of BPA in real environmental samples. Moreover, the configuration of this sensor is universal and can be extended to organic molecules that can be photoelectrochemically oxidized by Ru(3+).