LAUSR

Abstract This study aimed to improve the fluorescence performance of lac dye by preparing carbon quantum dots in an attempt to diversify the applicability of lac dye in fluorescence detection. The highly photoluminescent (PL) ld-CQDs were synthesized for the first time using lac dye as a precursor by a facile, green, one-pot ethanol thermal method. The ld-CQDs were neither soluble nor dispersed in water, but could be dissolved or dispersed in organic solvents. The ld-CQDs were well dispersed in ethanol with a mean diameter of 1.76 nm and were found to emit a bright yellow fluorescence with an emission wavelength of 570 nm. The quantum yield of ld-CQDs was 0.40, which was a significant 20-fold improvement over the lac dye of 0.02. Meanwhile, ld-CQDs exhibited pH-sensitive and excellent affinity for silicon dioxide without further chemical modification. Further, ld-CQDs could be used to image silicon dioxide since the fluorescence intensity of the ld-CQDs/silicon dioxide composites was significantly improved. Furthermore, the ld-CQDs could be used as a highly sensitive fluorescent probe to detect the ethanol content of commercial wines. In conclusion, this study has demonstrated the novel application of the fluorescence properties of the lac dye, which has utility in visual detection applications and in tracking the detection of silicon dioxide and ethanol.