Electrochemical UV Sensor Using Carbon Quantum Dot/Graphene Semiconductor

Our group has developed an electrochemical UV sensor utilizing carbon quantum dots as the photoactive material functionalizing a graphene semiconductor layer. When used as a photoactive electrode in contact with a solid polymer electrolyte in a photoelectrochemical cell, illumination under UV radiation at 365 nm induces a photocurrent with a corresponding change in device voltage. The time-dependent change in voltage is a function of UV radiation intensity. Varying the UV LED power density from 26.6 mW/cm2 (approximately 100% intensity) to 5.1 mW/cm2 (approximately 20% intensity) results in time-dependent potential changes (dU/dt) ranging from approximately 4.0 mV/s to 0.5 mV/s. The dU/dt vs. LED power density trend is nearly linear (r2 = 0.97). Similarly, when a constant bias potential is applied to the cell, a sustained photocurrent is observed under UV illumination, with the magnitude of the photocurrent a linear function of the LED power density. In that case, the coefficient of determination r2 = 0.98. These results indicate that a graphene semiconductor, when functionalized with a photoactive material like carbon quantum dots, has application as a UV sensor with the ability to quantify the intensity of UV radiation.