A Fluorescent Self‐Absorption Method for Detection of Captopril using Carbon Quantum Dots

Abstract A hydrothermal method for preparing water‐soluble carbon quantum dots (CQDs) was studied using the citric acid and thiourea. The CQDs have high fluorescence Intensity, high photoluminescence stability and uniform size. Their average size is 5 nm. Their maximum excitation and emission wavelengths are 364 and 452 nm, respectively. divalent copper ions can quench the fluorescence of CQDs and captopril can interact with divalent copper ions to form complexes, the complexes can further reduce the fluorescence of CQDs due to self‐absorption, and there was a linear relationship between the ratio of the fluorescence intensities before and after adding captopril and the captopril concentration. A novel, simple, and environmentally friendly fluorescence detection method for captopril was established. It has been successfully used for captopril detection in captopril tablets.