Nitrogen@Carbon Quantum Dots for Fluorescence Detection of L-alanine, L-methionine and L-cysteine.

Nitrogen@Carbon quantum dots (N@CQDs) are prepared using microwave hydrothermal method, and polyvinylpyrrolidone (PVP) and melamine are used as mixed C source and N source. Microwave reaction conditions of preparing the N@CQDs are 170 ℃ and 3 h. This N@CQDs are are used as fluorescence probe for detection of amino acids. The N@CQDs can recognize L-alanine in water solution, and simultaneously recognize both L-methionine and L-cysteine in dimethyl sulfoxide (DMSO) solution. The linear ranges for L-alanine, L-methionine and L-cysteine are 0-15 µM, 2-50 µM and 0-17 µM, respectively. While limits of detection (LOD) for them are 11.092 nM, 7.8067 nM and 0.67476 nM, respectively. Compared to presently available detection methods, as-prepared N@CQDs have the advantage of high sensitivity and selectivity. Furthermore, coexistence of other amino acids has minimal interference in the detection of L-alanine, L-methionine and L-cysteine. For the as-prepared N@CQDs, solvent plays important roles in influencing the identification of amino acid types and detection sensitivity.