Fabrication of High-Performance Molybdenum Disulfide–Graphitic Carbon Nitride p–n Heterojunction Stabilized rGO/ITO Photoelectrode for Photoelectrochemical Determination of Dopamine

The construction of solar active photoelectrodes for photoelectrochemical purposes based on a heterojunction platform is one of the most promising strategies. Herein, a molybdenum disulfide–graphitic carbon nitride (MoS2–GCN) p–n heterojunction stabilized reduced graphene oxide/indium tin oxide (rGO/ITO) photoelectrode was fabricated and has been employed for the photoelectrochemical detection of the neurotransmitter dopamine (DA). First, the rGO was electrochemically reduced on an ITO slice in GO dispersion (pH = 7, −1.5–0 V potential window for 30 cycles) by using the cyclic voltammetry technique, and then the MoS2–GCN heterostructure was immobilized on rGO/ITO by the drop-casting method. The physicochemical characterization of the fabricated electrodes was performed by means of XRD, Raman, UV–vis DRS, EIS, PL, and SEM techniques. The type of MoS2 and GCN semiconductors and the p–n heterojunction formation between the MoS2 and GCN were investigated through the Hall effect and Mott–Schottky analyses. The fabricated electrode shows an enhanced photocurrent activity at 535 nm, which is confirmed from the UV-DRS measurement. The MoS2–GCN/rGO/ITO shows photoelectrochemical detection activity of dopamine in the linear response of 0.005–1271.93 μM with the detection limit of 1.6 nM. This MoS2–GCN/rGO/ITO electrode was tested for the determination of dopamine in human urine and serum samples.