Decoupling photonic and thermal contributions for photoelectrochemical sensing of melatonin via graphene oxide nanoribbons

This work elucidates the photoelectrochemical (PEC) sensing of melatonin employing graphene oxide nanoribbons (GONRs) synthesized through a microwave-assisted method. GONRs served as electrocatalysts for screen-printed carbon electrodes (SPCE) to facilitate melatonin detection. We incorporated both a light-emitting diode (LED) and a solar simulator as light sources for PEC evaluations. Cyclic voltammetry revealed that the faradaic currents corresponding to melatonin oxidation on GONRs-modified SPCE were amplified under both LED and simulated solar light irradiation. Notably, the GONR (150 W) registered the most pronounced enhancement in the photo-assisted faradaic current and the highest conversion efficiency. Employing the solar simulator, certain thermal factor ratios concerning conversion efficiencies surpassed 50.0% at light intensities of both 80 mW/cm² and 100 mW/cm². Conversely, with the LED source, the thermal contribution remained below 15.0% of the total PEC faradaic current. We posit that obtaining conversion efficiencies devoid of thermal influences is pivotal for deepening our comprehension of PEC biosensing mechanisms.