Turn-On Fluorescent Sensing of Dust Particles Using Optimized Microwave-Synthesized Carbon Quantum Dots

A significant contributor to particulate matter (PM), dust particles negatively affect air quality and pose serious health risks, such as cardiovascular and respiratory issues. Therefore, it is crucial to accurately and efficiently detect dust particles to monitor air pollution and reduce its harmful effects. This research involved synthesising carbon quantum dots (CQDs) from citric acid and urea using microwave-assisted irradiation, with systematic adjustments of precursor ratios and reaction times to increase fluorescence. The CQDs emitted a distinct blue glow, achieved with a 1:2 urea-citric acid mixture and a microwave treatment lasting 2 min, which produced the highest fluorescence levels. When evaluated as fluorescent probes for particulate matter detection, using quartz sand as a model substrate, the CQDs showed a concentration-dependent decrease in fluorescence intensity, with a detection limit (LOD) of 0.31 mg/ml within the concentration range of 0.1–1 mg/ml. Although the method demonstrates potential, its current detection threshold is above typical ambient particulate matter concentrations, and the use of quartz sand limits direct applicability to chemically diverse real-world aerosols. These findings highlight the promise of CQDs for air quality monitoring and suggest avenues for improving sensitivity and expanding applicability to actual particulate matter sources.