Hydrothermal Synthesis of Tartaric Acid Functionalized Amino Acid CQD for Sensing of Hg2+ and Fe3+ Ions in Aqueous Medium

Abstract

Carbon quantum dots (CQDs) are a type of carbon-based nanoparticles that are typically smaller than 10 nanometres in size. In this study, L-tryptophan-mediated CQDs were synthesized using the hydrothermal carbonization (HTC) technique, which is known for its non-toxic, environmentally friendly, and cost-effective nature. The synthesized carbon quntum dot was successfully characterized. The HR-TEM analysis clearly revealed the formation of specific aggregates with a size distribution ranging from 3.0 to 5.1 nm. These L-tryptophan-mediated CQDs exhibited remarkable emission behaviour, displaying strong and stable blue fluorescence. Moreover, they were utilized as a sensor for the sensitive detection of Fe3+ and Hg2+ ions in an aqueous solution, employing a fluorescence quenching mechanism. The limit of detection for Fe3+ sensing was determined to be 1.2×10−5 M, while for Hg2+ sensing, it was found to be 1.9×10−5 M. The sensing of Fe3+ and Hg2+ ions was also confirmed through visual eye detection, as a significant color change of the CQDs was observed. Additionally, a competitive study was conducted to verify the selectivity of the L-tryptophan-mediated CQDs towards Fe3+ and Hg2+ metal ions.