Hole-oriented interface engineering for sensitive photoelectrochemical detection of tetracycline

High-performance photoelectrochemical (PEC) sensors require efficient utilization of photogenerated holes at the semiconductor/electrolyte interface. However, the rational design of an efficient interlayer for directed hole transport remains challenging. Herein, a CoMn-layered double hydroxide (CoMn-LDH) hole transport layer is integrated with a BiVO₄ photoelectrode to regulate interfacial charge transfer. Kelvin probe force microscopy (KPFM) and in situ X-ray photoelectron spectroscopy reveal that CoMn-LDH efficiently promotes hole extraction from BiVO₄ while markedly suppressing both interfacial and bulk charge recombination. Coupled with target-specific molecular recognition, the resulting PEC sensor enables highly sensitive and selective detection of tetracycline, affording a low detection limit of 8.4 nM and a wide linear range of 0.01-20 μM. The enhanced sensing performance originates from the built-in electric field at the CoMn-LDH/BiVO₄ heterojunction, which facilitates hole extraction and interfacial oxidation of tetracycline while suppressing electron-hole recombination. In addition, the sensor exhibits good repeatability, robust operational stability, and satisfactory recoveries in tap water, Chaohu lake water, and aquaculture water. This work establishes hole-oriented interfacial engineering as an effective strategy for developing high-performance PEC platforms for antibiotic monitoring.