Novel carbon quantum dots for fluorescent detection of phenol and insights into the mechanism

Phenol is considered as one of the most important pollutants in the water environment, and thus its detection plays a cardinal role in environmental assessment and treatment. In this study, high quality carbon quantum dots (CQDs) were successfully prepared by ozone oxidation, with cheap coal as the carbon material. The as-prepared CQDs exhibited a narrow size distribution between 2 and 9 nm, with an average size of approximately 4.2 nm. The novel CQDs showed high sensitivity and selectivity for phenol detection with a low detection limit of 0.076 μM in water due to the fluorescence quenching effect of the CQDs, which is attributed to the hydrogen bonds (CO⋯H–O) between phenol and the fluorescent CQDs according to the density functional theory (DFT) and time-dependent density functional theory (TDDFT) results. The theoretical calculation matches well with the experimental data, which provides us a new way to investigate the detection mechanism of the CQDs for phenol.