Light-Addressable Electrochemical Sensing with Electrodeposited n-Silicon/Gold Nanoparticle Schottky Junctions

Light-addressable electrochemical sensors (LAESs) are a class of sensors that use light to activate an electrochemical reaction on the surface of a semiconducting photoelectrode. Here, we investigate semiconductor/metal (Schottky) junctions formed between n-type Si and Au nanoparticles as light-addressable electrochemical sensors. To demonstrate this concept, we prepared n-Si/Au nanoparticle Schottky junctions by electrodeposition and characterized them using scanning electron microscopy, cyclic voltammetry, and electrochemical impedance spectroscopy. We found that the sensors behaved almost identically to Au disk electrodes for the oxidation of an outer-sphere redox couple (ferrocene methanol) and two inner-sphere redox couples (potassium ferrocyanide and dopamine). In buffered dopamine solutions, we observed broad linear ranges and submicromolar detection limits. We then used local illumination to generate a virtual array of electrochemical sensors for dopamine as a strategy for circumventing sensor fouling, which is a persistent problem for electrochemical dopamine sensors. By locally illuminating a small portion of the photoelectrode, many measurements of fouling analytes can be made on a single sensor with a single electrical connection by moving the light beam to a fresh area of the sensor. Altogether, these results pave the way for Schottky junction light-addressable electrochemical sensors to be useful for a number of interesting future applications in chemical and biological sensing.