A spectrofluorometric sensing platform for ciprofloxacin detection based on Mn doped ZnS quantum dots modified with quercetin

Abstract

This study presents a spectrofluorometric approach for the sensitive determination of ciprofloxacin (CIP) at low concentrations in aqueous samples. Manganese(II)-doped zinc sulfide quantum dots (Mn:ZnS QDs) were prepared by co-precipitation method using thioglycolic acid (TGA) as capping agent and subsequently functionalized with quercetin (Qu) as a non-toxic ligand. This modification prevents the aggregation of the QDs and the residual hydroxyl groups of Qu available on the surface of Mn:ZnS QDs provide water-dispersed quantum dots. Mn:ZnS@Qu QDs were characterized by various techniques. As a result, under excitation at 330 nm, the emission intensity of the T- A transition of Mn:ZnS@Qu QDs at 588 nm enhanced. The data obtained from theoretical computation indicated the existence of strong hydrogen bonding between CIP and Qu. Therefore, a simple fluorometric probe was used for the selective detection of CIP in the yellow-orange band at a wavelength of 588 nm. The key parameters affecting the fluorescence emission intensity were systematically optimized. Under the optimal conditions, the calibration curve was linear in the CIP concentration range from 0.01 to 0.2 μg mL , with a detection limit of 0.01 μg mL and a relative standard deviation of 1.1%. The selectivity of the method was evaluated in the presence of potential interfering substances. The probe was validated for CIP assay by applying it to real drinking water and urine samples with recoveries ranging from 90.6% to 103.5%, demonstrating the reliability and practical applicability of the method. The developed fluorescent platform provides a facile, low-cost, low toxicity, and reliable approach for monitoring CIP residues in aqueous samples