A Self-Powered Photoelectrochemical Sensor Based on an In2O3/Ag2S Heterojunction for Tetracycline Detection and Portable Applications

Tetracycline (TC) is a widely used broad-spectrum antibiotic that effectively inhibits a variety of bacteria. However, its extensive application has resulted in the release of residual TC into aquatic environments, where it has become a typical emerging contaminant that promotes bacterial resistance and disrupts ecological balance. In this study, a self-powered photoelectrochemical (PEC) sensor based on an In ₂ O ₃ /Ag ₂ S heterojunction was developed for the sensitive detection of tetracycline residues in water. In ₂ O ₃ with excellent photoelectric properties was first synthesized via a reflux-heating method followed by calcination. Subsequently, an In ₂ O ₃ /Ag ₂ S heterojunction was successfully constructed through an in situ growth strategy, exhibiting a significantly enhanced photoelectric response and a strong, stable initial photocurrent. Under optimized conditions, the proposed sensor exhibited a linear detection range for tetracycline from 1 nM to 1 mM, with a detection limit as low as 0.4 nM. In addition, the sensor demonstrated good stability, rapid response, high selectivity, and excellent reproducibility. Furthermore, by integrating a microcontroller-based system, sensor portability was achieved, offering a promising approach for the development of portable photoelectrochemical sensing technologies.