N,S-GQDs mixed with CdTe quantum dots for ratiometric fluorescence visual detection and quantitative analysis of malachite green in fish.

N,S-GQDS was prepared through citric acid cracking method from thiourea and citric acid, a ratiometric fluorescence sensor was constructed for the detection of malachite green based on CdTe quantum dots and N,S-GQDs. Interestingly the color of this ratiometric fluorescence sensor could change from red to blue under UV light upon exposure to different amounts of malachite green, and this ratiometric fluorescence sensor could be used for visual detection of malachite green. Fluorescence emission spectra of this ratiometric fluorescence sensor with different amounts of malachite green were also analyzed, and there was a good linear relationship between F/F and concentrations of malachite green, the lowest limit detection could reach 0.4597 nmol/L. Furthermore, this proposed ratiometric sensor is used for quantitative analysis of malachite green in fish sample. Results shown that this ratiometric fluorescence sensor is feasibility and practicality for both visual detection and quantitative analysis of malachite green.