Eco-friendly carbon quantum dots as a bi-functional fluorescent probe for Cr (VI) detection and optical thermometry

Carbon quantum dots (CQDs) from cumin (Cuminum cyminum) seeds have been synthesized using the hydro- thermal technique and were characterized by HR-TEM, XPS, FTIR, RAMAN, UV-Vis, and Photoluminescence (PL) spectroscopy. The photostability of CQDs was investigated through various tests such as in high saline conditions, with their storage time, under UV and white light exposure, pH values, and different solvents. They were found selective and sensitive to Cr6+ ions, so their potential as a fluorescent probe for Cr6+ ions sensing is being studied. The Lowest limit of detection (LOD) value for the current ion sensor in an aqueous solution is 8.3 mu M. The temperature dependence of PL intensity has also been utilized to demonstrate a temperature sensor with a thermal sensitivity of 0.658 degrees C-1. This study contributes significantly to temperature sensing and metal ions detection technologies by utilizing CQDs synthesized from natural precursors.