Ionic liquid and ZnO/carbon quantum dots derived from cat hair as an electrochemical sensor for ciprofloxacin in food samples: Experimental and cell‐imaging studies

Ciprofloxacin (CIP) has been widely used to treat bacterial infections, generating biofluid residues and it endangers health via the food chain; thus, the determination of CIP is essential in food samples. In this work, CPE/ZnO/CQD was prepared from ZnO nanoparticles (ZnO NPs) and carbon quantum dots (CQD) derived from cat hair and modified the graphite carbon paste electrode (CPE); the above electrode sample was further modified by incorporating ionic liquid (IL) to give CPE/ZnO/CQD@IL. The above materials were employed as electrochemical sensors for the recognition of CIP in milk and eggs after the characterization by different analytical techniques (XRD, FT‐IR, SEM, TEM, and EDS). The results show that the presence of nanoparticles in the CPE has improved the electrocatalytic properties, giving a greater heterogeneous electron transfer rate constant (k0=6.51×10−4 cm/s) for CPE/ZnO/CQD as compared to unmodified CPE (3.94×10−4 cm/s), and for CPE/ZnO/CQD/IL, with modification of sample by IL, the rate constant has been further increased to k0=8.34×10−4 cm/s. Thereafter, CPE/ZnO/CQD and CPE/ZnO/CQD@IL were employed for the detection of CIP in food samples such as milk and eggs, observing a maximum oxidation current for CIP at pH 3.0; the limit of detection (LOD) was 0.24, and 0.30 μM for CPE/ZnO/CQD, and CPE/ZnO/CQD@IL, respectively, and those values are much lower than those reported due to the synergistic effect generated by the combination of ZnO/CQD and IL. Furthermore, cell images were developed using ZnO/CQD and ZnO/CQD@IL in real samples like Saccharomyces cerevisiae cells in the presence of CIP.