A label-free fluorescent sensor based on yellow-green emissive carbon quantum dots for ultrasensitive detection of congo red and cellular imaging

Herein, an innovative label-free fluorescent sensor based on yellow-green emissive carbon quantum dots (YG-CQDs) was first constructed to determine congo red with high speed and sensitivity. The YG-CQDs were simply and quickly prepared using p-phenylenediamine and citric acid as precursors via a hydrothermal method. The prepared YG-CQDs exhibits favorable water solubility and excellent photoluminescence. The YG-CQDs showed an obvious fluorescence quenching behavior as the congo red content increase duo to an inner filter effect (IFE). YG-CQDs served as an effective fluorescent sensor in detecting congo red with high selectivity and sensitivity in a fast and direct manner under optimal conditions. Two good linear relationships were obtained for congo red detection over the concentration ranges of 0.5–50 and 50–170 μg mL−1, corresponding to two lower detection limits of 0.04 and 0.03 μg mL−1, respectively. Meanwhile, the constructed fluorescent sensor was successfully adopted to determine congo red in tap and lake water samples where the accuracy was high. In addition, due to low toxicity and superior biocompatibility, YG-CQDs was also found to be an effective agent for cellular imaging with satisfactory results. The results reveal the good potential of the prepared YG-CQDs for congo red sensing and cellular imaging.