Hydrothermal synthesis of fluorescent nitrogen-doped carbon quantum dots from ascorbic acid and valine for selective determination of picric acid in water samples

摘要

Nitrogen doped carbon quantum dots (N-CQDs) were synthesised by a hydrothermal method using ascorbic acid and valine as precursors. The as-synthesised N-CQDs were characterised by transmission electron microscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, UV-vis absorption spectra, as well as fluorescence spectrophotometer. The results revealed that the as-prepared N-CQDs were spherical shaped with an average diameter of 4 nm and emitted bright blue photoluminescence with a quantum yield of approximately 4.8 %. Additionally, we found that the fluorescence of the N-CQDs was intensively quenched by the addition of picric acid (PA). The decrease of the fluorescence intensity made it possible to determine PA in the linear range of 0.06-7.81 mu g ml(-1) based on the fluorescence resonance energy transfer between PA and N-CQDs. The detection limit was as low as 11.46 ng ml(-1). The proposed approach was further successfully applied for the determination of PA in water sample collected from Fenhe river for public safety and security, suggesting its great potential towards water routine analysis.