High selectivity fluorescence-based CQDs@cellulose membrane sensor for detection of hazardous gas

Toluene, a harmful gas, is extremely harmful to living organisms, and its distribution and concentration in the environment have always attracted much attention. However, traditional detection methods have poor selectivity, cannot detect low concentrations, and the equipment is bulky, expensive, and time-consuming. In this study, a fluorescence spectroscopy method based on carbon quantum dots (CQDs) composite cellulose membrane (CQDs@CMC membrane) was developed, which addressed the limitations of CQDs, such as excessive operational expenses, intricate detection procedures, and prolonged analysis duration, enabling highly sensitive and specifically targeted detection of toluene gas. Firstly, hydrophobic propylene glycol/betaine (Gly/Bet) CQDs was prepared by hydrothermal method, and Gly/Bet CQDs composite membranes were prepared by combining them with CMC membrane, and they were characterized separately. It was found that Gly/Bet CQDs had a slight blue shift compared to the optimal excitation wavelength of the Gly/Bet CQDs @CMC membrane. Gly/Bet CQDs were uniformly loaded on the CMC membrane, and the fluorescence lifetime and fluorescence quantum yield (FQY) increased to 5.3 ns and 18.34 ns, respectively. The detection of harmful gas toluene was carried out by Gly/Bet CQDs composite membrane, and the toluene concentration had a great influence on the fluorescence intensity of Gly/Bet CQDs@CMC membrane, and when the toluene concentration was in the range of 200-1400 ppm, the fluorescence intensity was in proportion to the toluene concentration. The detection limit for p-toluene is 0.452 ppm, which is very sensitive. According to the results, the Gly/Bet CQDs@CMC membrane is capable of effectively detecting toluene gas, which offers a solid theoretical foundation for the later use of toluene emission in real industry and toluene gas detection in daily life. In addition, it detects toluene and interfering gases with high selectivity.