A fluorescent sensor for rapid and quantitative aquatic bacteria detection based on bacterial reactive oxygen species using Ag@carbon dots composites

A novel fluorescent sensor based on silver nanoparticle-carbon dot composites (Ag@CDs) has been developed for the rapid and quantitative detection of aquatic bacteria. The sensor operates on the principle of plasmon-enhanced resonance energy transfer, where the fluorescence of CDs is quenched by Ag nanoparticles and restored upon bacterial interaction due to the generation of reactive oxygen species. The Ag@CDs exhibit a linear response to bacterial concentration over the range 7 × 10⁴ ~ 4 × 10⁷ CFU·mL^-1, with a low detection limit of 4 × 10⁴ CFU·mL^-1. The fluorescence recovery is rapid, reaching maximum intensity within 5 min. The method demonstrates high selectivity, with minimal interference from common ions and compounds found in municipal and industrial wastewater. The Ag@CDs-based 96-well plate assay for quantitative measurement of bacteria was developed. The assay's performance was further validated through the analysis of real water samples, showing a recovery of 94.0 ~ 102% for domestic wastewater and 97.6 ~ 106% for industrial wastewater. Also, Ag@CDs-based test strips assay for semi-quantitation were developed for rapid in-field aquatic bacteria detection. Ag@CDs can be conveniently integrated into 96-well plates and test strips, providing rapid on-site aquatic bacteria testing.