Smartphone-assisted colorimetric sensing platform based on molybdenum-doped carbon dots nanozyme for visual monitoring of ampicillin

Monitoring and control of ampicillin (AMP) residues in environment are of great significance for reducing bacterial resistance, maintaining microecological balance, and protecting human health. In this work, an innovative molybdenum-doped carbon dots (Mo-CDs) nanozyme was designed and synthesized via one-step hydrothermal synthesis. Due to the suitable selection of precursors, the carbon dots were doped with variable valence Mo, resulting in excellent peroxide-like activity to catalyze H2O2 to 1O2 (Km = 0.176 mM of H2O2). Based on the considerable reactivity between AMP and generated 1O2 of the catalytic system, a colorimetric sensor for AMP detection was constructed with a good linear relationship from 0.0500 to 100 μg/mL, and detection limit down to 12 ng/mL. Furthermore, the visual sensing platform of colorimetric test strips integrated with smartphone were established and successfully realized rapid, portable, and sensitive visual monitoring of AMP in water samples. This work has not only developed a new and efficient carbon dots nanozyme and constructed a smartphone-assisted colorimetric sensor, but also proposed a novel design strategy for developing a low-cost and easy-to-operate antibiotic detection tool with good specificity and sensitivity.