Highly efficient visible-light-induced photoactivity of the CdS–Mn/MoS2/CdTe/TiO2 quaternary photocatalyst for label-free immunoassay of tris-(2,3-dibromopropyl) isocyanurate and enhanced solar hydrogen generation

A gradually stepped CdS–Mn/MoS2/CdTe/TiO2 quaternary photocatalyst is successfully synthesized by a reliable and effective method. The as-synthesized CdS–Mn/MoS2/CdTe/TiO2 photocatalyst showed excellent improvement for visible-light absorption and the separation efficiency of photoinduced electron–hole pairs. The CdS–Mn/MoS2/CdTe/TiO2 photoelectrode exhibits optimum visible-light-induced photocatalytic activity in photoelectrochemical (PEC) immunoassay of tris-(2,3-dibromopropyl) isocyanurate (TBC) and producing hydrogen (H2) out of water, and a linear range of 2 pM to 100 nM, a low detection limit (3 S/N) of 1.02 pM and a H2 evolution rate of 10.165 mL cm−2 h−1 are obtained. The excellent photocatalytic activities are attributed to the synergetic effects of CdS–Mn, MoS2, CdTe and TiO2 nanophase structures in the CdS–Mn/MoS2/CdTe/TiO2 composites, which result in a step-wise-mechanism-assisted fast separation and slow recombination of photoinduced electron–hole pairs and thereby higher photocatalytic activity. The electrochemical impedance spectra and the significant enhancement of photocurrent responses indicated that the stepwise structure of band-edge levels dramatically facilitated the electron transfer in the CdS–Mn/MoS2/CdTe/TiO2 nanocomposite electrode. The CdS–Mn/MoS2/CdTe/TiO2 photoelectrode was demonstrated to be effective for photoelectrochemical sensing of trace environmental pollutants in water samples and solar H2 generation out of water.