A sensitive fluorescence probe based on 3-mercaptopropionic acid (MPA) capped cadmium-sulfide quan- tum dots (CdS QDs) was prepared for determination of ciprofloxacin (CIP) in real samples. The synthesized MPA capped CdS QDs was characterized using fourier-transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), and transmission electron microscopy (TEM) measurements. Based on the results, the fluorescence of MPA capped CdS QDs was quenched in presence of Cu 2+ that it could have occurred because of the nonradiative electron–hole recombination annihilation through an electron transfer pro- cess. Subsequently, the fluorescence of MPA capped CdS QDs mixed with the Cu 2+ could be recovered after the addition of CIP due to its strong affinities for Cu 2+ . The recovered fluorescence intensity of capped CdS QDs was proportional to the concentration of CIP in the ranges of 0.13–150.0 mol L −1 and the detection limit was 0.04 mol L −1 . The established method showed a good selectivity for CIP among several kinds of ions and biomolecules. The fluorescent probe was successfully applied to determine CIP in pharmaceutical preparation and human serum samples.
