Revealing the potential of biogenic carbon dot-based nanosensor for the high-throughput detection of carcinogenic Hg+2 and tetracyclines.

We have classified antibiotics and heavy metals as two major classes of contaminants and developed a casein protein and thymine-derived carbon dot-based sensor (CasT@CDs) that can monitor the presence of the substances in the aqueous medium. Our synthetic protocol has achieved a 36% quantum yield. CasT@CDs were characterized by FETEM, XRD, XPS, FT-IR, and EDS. The nanosensor has exhibited excellent fluorescence quenching in the presence of tetracycline derivatives-tetracycline (TC), chlortetracycline (ClTC), and doxycycline (DTC)-as well as mercury ions (Hg⁺2). The detection limits for the tetracycline derivatives were 10-13 nM. At the same time, for Hg⁺2, the nanosensor exhibited the highest selectivity with a detection limit of 5.3 nM (1.7 ppb), below the permissible limit in water set by the US EPA (2 ppb). The linear range of detection for TC, DTC, and ClTC is 39 nM-45 µM, and for Hg+2 is 19.6 nM to 1.8 µM. For both classes of analytes, the nanosensor demonstrated a remarkable response time of less than 10 s and exhibited high selectivity even in the presence of co-existing interfering species. The quenching mechanism was thoroughly investigated and confirmed through time-resolved photoluminescence (TRPL) and various spectroscopic analyses. The practical applicability of the sensor was validated using real sample analysis through fluorescence and paper strip-based detection experiments under an UV lamp. Overall, the synthesized nanodots show significant potential for contributing to environmental and ecosystem safety.