In Situ Formation of Bi2MoO6-Bi2S3 Heterostructure: A Proof-Of-Concept Study for Photoelectrochemical Bioassay of l-Cysteine

Abstract

A novel signal-increased photoelectrochemical (PEC) biosensor for l-cysteine (L-Cys) was proposed based on the Bi2MoO6–Bi2S3 heterostructure formed in situ on the indium–tin oxide (ITO) electrode. To fabricate the PEC biosensor, Bi2MoO6 nanoparticles were prepared by a hydrothermal method and coated on a bare ITO electrode. When L-Cys existed, Bi2S3 was formed in situ on the interface of the Bi2MoO6/ITO electrode by a chemical displacement reaction. Under the visible light irradiation, the Bi2MoO6–Bi2S3/ITO electrode exhibited evident enhancement in photocurrent response compared with the Bi2MoO6/ITO electrode, owing to the signal-increased sensing system and the excellent property of the formed Bi2MoO6–Bi2S3 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.

Enzymatically Mediated In Situ Generation of Z-Scheme Bi2S3/Bi2MoO6 Heterojunction-Based Organic Photoelectrochemical Transistor for METTL3/METTL14 Detection

“…36 It should be noted that after in situ formation of Bi 2 S 3 /Bi 2 MoO 6 , the binding energy of Mo 6+ in the sample shifted to low binding energy, indicating that the Mo content in the sample decreased, which might be caused by the strong interaction between Bi 2 S 3 and Bi 2 MoO 6 . 36 The binding energies of 530.02 and 529.89 eV in Figure 1I were assigned to the high-resolution XPS spectra of O 1s in Bi 2 MoO 6 before and after the anion exchange reaction, 37 respectively. XPS results further indicated that after the anion exchange reaction, part of Bi 2 MoO 6 was transformed into Bi 2 S 3 , forming the Bi 2 S 3 /Bi 2 MoO 6 heterojunction.…”

“…According to the equation of E VB = E g + E CB , 40 the E VB of Bi 2 MoO 6 was calculated to be 2.07 eV. Since the valence band and conduction band of Bi 2 S 3 were higher than those of Bi 2 MoO 6 , 37 the photogenerated electrons generated by Bi 2 S 3 under photoexcitation would be rapidly transferred to the conduction band of Bi 2 MoO 6 , and then transferred to the detection solution. The occurrence of electron transfer could effectively improve the separation of electrons and holes, and generate larger cathode photocurrent signals.…”