Dual-emission ratio fluorescent probe based on carbon dots and copper-silver bimetallic nanoclusters for visual and fluorescent detection of ciprofloxacin

Ciprofloxacin (CIP) plays an important role in many physiological processes. Previously reported methods for CIP detection have many drawbacks and so it is crucial to develop highly sensitive methods to detect CIP. In this study, a dual-emission ratiometric fluorescent probe (SF-CQDs/CuAg NCs) of a nanocomposite of carbon quantum dots (SF-CQDs) and copper-silver bimetallic nanoclusters (CuAg NCs) was developed for sensitive and selective detection of CIP. The fluorescent signal of CuAg NCs was quenched while the fluorescence intensity of SF-CQDs was enhanced in the presence of CIP. The working principle of the fluorescent probe SF-CQDs/CuAg NCs is mainly based on the complexation of CIP with CuAg NCs to free SF-CQDs. The quenching of CuAg NCs by CIP arises from the chelation between the metal and the 1-oxo substituent and the adjacent carboxyl group of CIP. The fluorescence recovery of SF-CQDs is attributing to the release of SF-CQDs from SF-CQDs/CuAg NCs and the hydrogen bonding interaction between SF-CQDs and CIP. The ratiometric fluorescence measurement of SF-CQDs/CuAg NCs has been employed to analyze CIP with good sensitivity and selectivity. The working range of CIP is 5.0–200.0 μM and the detection limit is 3.3 μM. More importantly, the fluorescence of SF-CQDs/CuAg NCs can be detected intuitively via a smartphone which can be applied to determine CIP.