Interfacial charge engineering of Ti₃C₂T_x/Bi₂S₃ for fully integrated photoelectrochemical sensing arrays

Developing a high-performance and fully integrated photoelectrochemical (PEC) sensing platform for the on-site detection of antibiotic residues still remains challenging, as the key lies in constructing photoactive materials and integrated electrode arrays. Herein, we introduce highly conductive and hydrophilic Ti₃C₂T_x MXene to engineer the interfacial charge dynamics of bismuth sulfide (Ti₃C₂T_x/Bi₂S₃), addressing the rapid charge recombination and low conductivity in Bi₂S₃-based biosensors. This strategy not only facilitates electron extraction but also establishes a Schottky barrier suppresses electron backflow, thereby boosting photoelectric conversion efficiency for enhanced detection sensitivity. A fully integrated photoelectrode array is then fabricated by assembling Ti₃C₂T_x/Bi₂S₃ with carbon nanotubes via a template filtration method, yielding superior conductivity, stability, and reproducibility. This array features adjustable multichannel Ti₃C₂T_x/Bi₂S₃ disc working electrodes alongside integrated Ag/AgCl disc reference/counter electrodes. As a proof of concept, aptamer-functionalized sensing arrays achieve detection limits as low as 3.91 pM for chloramphenicol (CAP) and 4.91 pM for amoxicillin (AMX) in simultaneous assays, demonstrating robust selectivity in complex real samples. This work establishes a generalized strategy for translating interfacial charge regulation into high-performance, fully integrated PEC biosensing devices, advancing toward portable and multiplexed bioanalysis.