One-Step Synthesis of CuO–Cu2O Heterojunction by Flame Spray Pyrolysis for Cathodic Photoelectrochemical Sensing of l -Cysteine

CuO–Cu 2 O heterojunction was synthesized via a one-step flame spray pyrolysis (FSP) process and employed as photoactive material in construction of a photoelectrochemical (PEC) sensing device. The surface analysis showed that CuO–Cu 2 O nanocomposites in the size less than 10 nm were formed and uniformly distributed on the electrode surface. Under visible light irradiation, the CuO–Cu 2 O-coated electrode exhibited admirable cathodic photocurrent response, owing to the favorable property of the CuO–Cu 2 O heterojunction such as strong absorption in the visible region and effective separation of photogenerated electron–hole pairs. On the basis of the interaction of l -cysteine ( l -Cys) with Cu-containing compounds via the formation of Cu–S bond, the CuO–Cu 2 O was proposed as a PEC sensor for l -Cys detection. A declined photocurrent response of CuO–Cu 2 O to addition of l -Cys was observed. Influence factors including CuO–Cu 2 O concentration, coating amount of CuO–Cu 2 O, and applied bias potential on the PEC response toward l -Cys were optimized. Under optimum conditions, the photocurrent of the proposed sensor was linearly declined with increasing the concentration of l -Cys from 0.2 to 10 μM, with a detection limit (3S/N) of 0.05 μM. Moreover, this PEC sensor displayed high selectivity, reproducibility, and stability. The potential applicability of the proposed PEC sensor was assessed in human urine samples.