Amino Acid-Functionalized Carbon Quantum Dots for Ultrasensitive and Selective Fluorometric Chlorpyrifos Detection

Carbon quantum dots (CQDs) are carbon-based semiconductor nanomaterials that have attracted significant attention due to their unique optical properties, biocompatibility, and environmentally friendly nature. These features make them promising candidates for the sensitive and selective detection of harmful pesticides, particularly chlorpyrifos (CP), a widely used organophosphate insecticide that poses environmental and health risks. In this study, CQDs were synthesized via a hydrothermal method using grape acid and three different amino acids (L-cysteine, L-tryptophan, and L-serine). They were comparatively evaluated based on the type of amino acid used. The amino acids enhanced the surface functionalities of the CQDs, which were confirmed by scanning transmission electron microscopy (STEM) and density functional theory (DFT) analyses, including the highest occupied molecular orbital-lowest unoccupied molecular orbital (HOMO-LUMO) energy levels. The developed CQD based fluorescence sensor demonstrated high sensitivity and selectivity toward CP among four tested pesticides. Notably, cysteine-doped CQDs exhibited superior sensing performance at low concentrations (7.42 × 10^-12 mol L^-1). This study highlights the potential of amino acid-functionalized CQDs as effective, low-cost, and environmentally friendly platforms for the sensitive monitoring of pesticides, offering essential applications in environmental safety and public health protection.