A glassy carbon electrode modified with carbon quantum dots and polyalizarin yellow R dyes for enhanced electrocatalytic oxidation and nanomolar detection of l-cysteine

A novel electrochemical sensor for the detection of l-cysteine was proposed based on immobilizing poly (alizarin yellow R)/carbon quantum dots film on glassy carbon electrode. Hydrothermal treatment was used to prepare carbon quantum dots. Transmission electron microscopy and Fourier transform infrared spectroscopy were used for characterization of carbon quantum dots. Electrochemical impedance spectroscopy, cyclic voltammetry and amperommetry were utilized to confirm the successful stepwise assembly procedure of the sensor. The electrocatalytic behaviors of the sensor were also investigated by cyclic voltammetry and amperommetry. Results showed that poly (alizarin yellow R)/carbon dots exhibited a remarkable electrocatalytic activity for the oxidation of l-cysteine under optimal conditions. The electrocatalytic response of the sensor was proportional to the l-cysteine concentration in the range of (0.3 to 3.6 μM) and (3.9 to 7.2 μM) with a limit of detection and sensitivity of 90 nM and 0.482 μA/μM, respectively. The modified electrode demonstrated many advantages such as simple preparation, high sensitivity, low detection of limit, excellent catalytic activity at physiological pH values, short response time, and remarkable antifouling property toward l-cysteine and its oxidation product.