Hydrothermal synthesis of Tartaric acid functionalized Amino acid CQD for sensing of Hg sup(2+) and Fe sup(3+) 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 Fe sup(3+) and Hg sup(2+) ions in an aqueous solution, employing a fluorescence quenching mechanism. The limit of detection for Fe sup(3+) sensing was determined to be 1.2x10 sup(-5) M, while for Hg sup(2+) sensing, it was found to be 1.9x10 sup(-5) M. The sensing of Fe sup(3+) and Hg sup(2+) 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 Fe sup(3+) and Hg sup(2+) metal ions.