Facile synthesis of carbon quantum dots with yellow-green emission and the applications in sunset yellow detection, anti-counterfeiting, and light-emitting diodes

Yellow-green emissive carbon quantum dots (CQDs) were synthesized via the pyrolysis of sodium citrate and urea in the air. The as-synthesized CQDs manifested bright fluorescence with a maximum emission peak at 520 nm, a quantum yield of 8.43%, excellent photostability, and outstanding stability in high-salt conditions. The CQDs were used for the selective detection of sunset yellow (SY). The presence of SY resulted in a remarkable reduction in the fluorescence of the CQDs, which was caused by the inner filter effect. A good linear relationship was achieved in the range of 0-30 uM with a limit of detection of 0.22 uM. Additionally the CQDs were exploited in anti-counterfeiting and the fabrication of light-emitting diodes with satisfactory performance.