Square-Wave Voltammetry Enables Measurement of Light-Activated Oxidations and Reductions on n-Type Semiconductor/Metal Junction Light-Addressable Electrochemical Sensors

Light-addressable electrochemical (LAE) sensing is a photoelectrochemical technique that enables high-density, individually addressed electrochemical measurements using light to activate an electrochemical reaction at the surface of a semiconducting photoelectrode. However, one major challenge is that only one electrochemical reaction (oxidation or reduction) will be activated by light. Here, we used square-wave voltammetry (SWV) to enable measurement of both types of electrochemical reactions using n-Si/Au NP LAE sensors. We demonstrated this approach for the oxidation of ferrocene methanol and the reduction of ruthenium hexamine and methylene blue. We found that for all molecules, SWV showed dramatic improvements in current under illumination in comparison with dark samples. We also demonstrated that this approach works for both fully illuminated and partially illuminated samples. Altogether, we hope these results open up new applications for LAE sensors, especially those based on semiconductor/metal junctions.