Surface-modified carbon quantum dot for enhanced fluorescent-sensing of hexagonal valent chromium

As one of the most harmful heavy metal pollutants, hexavalent chromium Cr(VI) is becoming a serious threat to human health. Thus pursuing a remarkably sensitive method to monitor the Cr(VI) concentration in natural conditions is favored for the fast response to prevent harm. In the present work, an ethylenediamine (En) and SiO₂-modified wool keratin-based carbon quantum dot (CQD)(En@CQDs@SiO₂) fluorescent sensor is prepared, and the En is found to improve the discrimination ability by binding the Cr(VI) with the surface carboxyl groups. Based on these designs, the En@CQDs@SiO₂ achieves a significant improvement in the Cr(VI) detection ability, with a detection limit of 6.08 × 10^-4 mg/L, which succeeded 6 times over CQDs, and is better than conventional UV-Vis and flame atomic absorption (AAS) techniques. Furthermore, the fluorescent sensor has good relative sensitivity, selectivity, good spectral reproducibility, and excellent structural stability. These properties make the sensor suitable for environmental Cr(VI) detection, which undoubtedly improves the economy and environmental friendliness of the fluorescent sensor.