Au Nanoparticles-Decorated BiOI Nanosheet Arrays for Cathodic Photoelectrochemical Dopamine Sensors

Photocathode-based photoelectrochemical (PEC) sensors can well evade the intrinsic hole oxidation reactions occurring at the photoelectrode–electrolyte interface and expand the application of PEC sensors in the field of bioanalysis. Herein, a cathodic PEC sensor based on p-type semiconductor bismuth oxyiodide nanosheet arrays (BiOI NSAs) integrated with gold nanoparticles (AuNPs) on indium-doped tin oxide (ITO) electrode (ITO/BiOI NSAs/AuNPs) is fabricated by a two-step electrodeposition method. The local surface plasmon resonance (LSPR) effect of AuNPs facilitates the capability of visible light absorption of the BiOI NSAs. Meanwhile, AuNPs, as an electron reservoir, improve the charge separation efficiency of carriers by forming a Schottky barrier, allowing more electrons to be transferred to O2 dissolved in the electrolyte, consequently promoting the PEC activity of the photoactive materials. Furthermore, dopamine (DA) can enhance the photocurrent of the ITO/BiOI NSAs/AuNPs photoelectrode by binding to Bi3+ on the BiOI NSAs surface to in-situ-form a charge-transfer complex (CTC). Based on this phenomenon, a PEC sensor was designed for the determination of DA, and the PEC sensor showed acceptable results for DA detection in real samples. The PEC sensor demonstrates the prospect of BiOI-based materials in cathodic PEC biosensing.