Lattice-matched SnS/SnIn₄S₈ heterojunction-based molecularly imprinted photoelectrochemical sensor for tetracycline detection in milk

Tetracycline residues in milk pose potential food safety risks, highlighting the need for sensitive and selective analytical methods. In this work, we developed a molecularly imprinted photoelectrochemical (PEC) sensor based on a lattice-matched SnS/SnIn₄S₈ heterojunction. The ultralow lattice mismatch (0.33%) promotes efficient charge separation and migration, producing a markedly enhanced photocurrent response (2.81 μA·cm^-2), up to 3.6 times the responses of the individual components. Coupling the heterojunction with molecular imprinting yielded a signal-off PEC sensing platform, and machine-learning-assisted optimization further improved its analytical performance. The sensor achieved a wide linear range (1 × 10^-4 - 1 × 10² μmol·L^-1) and a low detection limit (2.43 × 10^-4 μmol·L^-1), with reliable performance in real milk samples. These results identify lattice-matched heterointerface engineering as an effective strategy for regulating carrier transport and enhancing PEC signals, providing a general framework for high-performance analytical sensing.