Light-activated electrochemistry for the two-dimensional interrogation of electroactive regions on a monolithic surface with dramatically improved spatial resolution

The concept of light-activated electrochemistry (LAE) was recently presented where faradaic electrochemistry could be spatially resolved on a monolithic silicon electrode by illuminating the specific region with light. A major implication from the previous study using illumination from the nonsolution side, or backside, is that the spatial resolution is limited by the finite thickness of silicon wafer. To overcome this restriction, and enable the further application of LAE, in combination with optical imaging for example, herein the spatial resolution of LAE using topside illumination (illumination from the solution side) is explored. The applied potential and irradiated light intensity are found to have significant effects on the spatial resolution. A spatial resolution of ∼30 μm was achieved with optimal parameters, which is a 20 times improvement compared with the previously reported backside illumination design, demonstrating the potential application of the strategy including microarray patterning of silicon or for single cell analysis.