In Situ Formation of Bi(2)MoO(6)-Bi(2)S(3) Heterostructure: A Proof-Of-Concept Study for Photoelectrochemical Bioassay of l-Cysteine

A novel signal-increased photoelectrochemical (PEC) biosensor for l-cysteine (L-Cys) was proposed based on the Bi(2)MoO(6)–Bi(2)S(3) heterostructure formed in situ on the indium–tin oxide (ITO) electrode. To fabricate the PEC biosensor, Bi(2)MoO(6) nanoparticles were prepared by a hydrothermal method and coated on a bare ITO electrode. When L-Cys existed, Bi(2)S(3) was formed in situ on the interface of the Bi(2)MoO(6)/ITO electrode by a chemical displacement reaction. Under the visible light irradiation, the Bi(2)MoO(6)–Bi(2)S(3)/ITO electrode exhibited evident enhancement in photocurrent response compared with the Bi(2)MoO(6)/ITO electrode, owing to the signal-increased sensing system and the excellent property of the formed Bi(2)MoO(6)–Bi(2)S(3) heterostructure such as the widened light absorption range and efficient separation of photo-induced electron–hole pairs. Under the optimal conditions, the sensor for L-Cys detection has a linear range from 5.0 × 10(−11) to 1.0 × 10(−4) mol L(−1) and a detection limit of 5.0 × 10(−12) mol L(−1). The recoveries ranging from 90.0% to 110.0% for determining L-Cys in human serum samples validated the applicability of the biosensor. This strategy not only provides a method for L-Cys detection but also broadens the application of the PEC bioanalysis based on in situ formation of photoactive materials.