Investigation of Fluorescence Sensing Capabilities in Boron-Nitrogen Co-Doped Carbon Quantum Dots Towards Fe (III) and Hg(II) Ions.

The detection of toxic metal ions in water is crucial for safeguarding environmental and human health. The study demonstrates a dual-mode fluorescence sensing strategy using boron and nitrogen co-doped carbon quantum dots (BN-CQDs), capable of both significant quenching and emission wavelength shift, for selective detection of Fe (III) and Hg(II) ions. In this study, (BN-CQDs) were synthesized using a green, microwave-assisted approach. Comprehensive characterization revealed that co-doping with boron and nitrogen significantly enhanced the optical and sensing properties of the CQDs. BN-CQDs exhibited a particle size below 5 nm, abundant surface functional groups, and photoluminescence (PL) with a quantum yield of 3.4% against quinine sulphate. It demonstrated remarkable photostability, retaining 92% PL intensity under visible light for 5 h and ionic stability. The prepared BN-CQDs were further used for fluorescence sensing for Fe (III) and Hg(II) ions. The results of zeta potential and TRPL studies is used to elucidate the distinct interaction mechanisms with metal ions. Distinct quenching mechanisms were observed: dynamic quenching for Fe(III) via photoinduced electron transfer (PET) and static quenching for Hg (II) through surface state modification. The detection limits of 0.081 µM for Fe(III) and 0.025 µM for Hg(II), and quantification limits of 0.25 µM (Fe(III)) and 0.075 µM (Hg (II)) present the ability of detection of these metal ions by fluorometric sensor. This study underscores the potential of BN-CQDs as eco-friendly and effective sensors for environmental monitoring.