Detection of ciprofloxacin and pH by carbon dots and rapid, visual sensing analysis

Food safety is a serious issue worldwide and practical detection method is vital for the supervision of food safety. It is necessary to establish efficient and economical methods to detect antibiotics, especially antibiotics in complex systems. This study employs citric acid and m-phenylenediamine to synthesize N, P-codoped carbon dots (N, P-CDs) by a microwave-assisted method. Anhydrous ethanol and phosphoric acid are essential to the properties of N, P-CDs. A "turn-on" fluorescent probe based on N, P-CDs was established for detecting ciprofloxacin (CIP) with detection limit down to 24.2 nm. Semiquantitative test stripe and a PS color detection system for CIP were developed to achieve visual and smart detection. The test stripe is applied to the visual detection of CIP residues in milk and a popular Chinese cuisine, Malatang, for the first time. N, P-CDs can also be used to detect pH in the range of pH 7.5-12.