Au-mediated Z-scheme TiO₂-Au-BiOI photoelectrode for sensitive and selective photoelectrochemical detection of L-cysteine

Accurate detection of L-Cysteine (Cyst) is critical because it is a recognized marker associated with diseases such as liver damage and kidney failure. Photoelectrochemical (PEC) sensor is an emerging strategy for biochemical analysis. However, the sensitivity of PEC sensor is limited by the high recombination rate of photogenerated electron-hole pairs. In this study, Au-mediated Z-scheme TiO₂-Au-BiOI (HTNTs-Au-BOI) photoelectrochemical sensing platform for Cyst detection is proposed. Au NPs with plasmon resonance effect not only boost the light absorption but also facilitate the formation of Z-heterojunction HTNTs-Au-BOI through its own mediating effect. The Z-heterostructure with built-in electric field dramatically suppress the recombination of photogenerated electron-hole pairs and improve the sensitivity of the sensor. Meanwhile, the dual-specificity of Bi-S and Au-S bonds achieves a highly selective and sensitive detection of Cyst. The PEC sensor shows a wide linearity detection range of 80 nM-200 μM with a detection limit of 70 nM. The sensor also shows good results in the detection of serum samples, with a relative standard deviation (RSD) of 0.68–7.3 %.