Development of co-doped ZnS-CdS quantum dots based composite sensor for the detection of cefixime (CXM) and tetracycline (TET), and application in real samples from local dairies

The excessive use of antibiotics, particularly Cefixime (CXM) and tetracycline (TET), poses serious risks to human health and the environment. This study presents a novel detection method utilizing zinc sulfide-cadmium sulfide/cobalt (ZnS-CdS/Co) quantum dots, characterized through scanning electron microscopy (SEM), photoluminescence (PL), energy dispersive X-ray (EDX), mapping, Line scan, Fourier-transform infrared spectroscopy (FT-IR) techniques, and X-ray diffraction (XRD). Aqueous solutions of varied TET and CXM concentrations were prepared and analyzed using these synthesized quantum dots. The analysis revealed a significant decrease in fluorescence intensity with increasing antibiotic concentrations, demonstrating the method's high specificity and sensitivity. Recovery experiments with spiked milk samples yielded high accuracy, with CXM recovery rates ranging from 96.0 to 100.77% for Bistoon milk and 100.5-100.33% for Kalleh milk; TET recovery rates ranged from 97.2 to 106.0% for Bistoon milk and 93.16-102.5% for Kalleh milk. The optimized ZnS-CdS/Co nanoparticles showed low detection limits of 4.5 nM for CXM and 5.2 nM for TET. These findings underscore the potential of this rapid detection system as an effective tool for monitoring antibiotic residues in food products, significantly contributing to food safety and environmental sustainability. Future research could focus on enhancing the selectivity of these quantum dots for broader applications in complex matrices, promoting more sustainable antibiotic monitoring practices.