Dual-channel fluorescence detection of hydroxyl radical based on red emitted carbon dots derived from imidazole cationic organic cage.

The dual-channel fluorescent sensing of hydroxyl radicals (·OH) is of great importance for environment and life. Organic cage for fluorescence sensing suffers from short excitation/emission wavelength and poor water solubility, while the application of carbon quantum dots is also hindered by the time-consuming preparation in high pressure and temperature conditions. Herein, we report a red emitted carbon dots derived from cationic organic cage for dual-channel fluorescent sensing of ·OH. The abundant flexible methylene within the cationic organic cage leads to remarkable collapse of intrinsic cavity. The ring-opening of imidazole structure occurs via redox reaction at acidic condition, resulting in the simple formation of carbon dots with the emission at 640 nm. Under acidic conditions, the ·OH generated via Fenton reaction exhibits strong affinity toward the prepared carbon dots. The mild oxidation at pH 1 significantly enhances the fluorescence, whereas the severe oxidative degradation at pH 6 leads to obvious fluorescence quenching. Based on the mutual verification of dual signals, a dual-channel fluorescent sensing method is established for ·OH in environmental samples and biological fluids. The sensing at pH 6 and 1 respectively achieves the linearity range of 1-50 and 5-50 μM, the limit of detection of 7.3 and 11.8 nM, and the relative standard deviation of 0.76% and 0.83% for 10 replicate analysis. The proposed method gives the recoveries of spiked ·OH ranged from 97.3% to 103.4% in real samples, demonstrating excellent accuracy and reliability. This study underscores the promising application potential of organic cage and carbon dots in fluorescent sensing. Furthermore, combined with Fenton reaction, the proposed dual-channel sensing platform can also be utilized to the detection of hazardous substances or biomarkers capable of HO generation.