Determination of cytochrome c based on its enhancing effect on the electrogenerated chemiluminescence of carbon quantum dots

Carbon dots (C-dots) display strong cathodic electrogenerated chemiluminescence (ECL) in neutral aqueous solution in the presence of potassium persulfate. ECL intensities strongly depend on the method of synthesis of C-dots. The reactions between the electrochemically reduced intermediates of C-dots and potassium persulfate generate a strong ECL signal. Spectral and electrochemical studies revealed that cytochrome c reacts with potassium persulfate before its electrochemical reduction to generate the strong oxidant radical SO4 (aEuro cent-) which reacts with C-dots to give an enhanced ECL signal. This finding was exploited to design a sensitive ECL assay for cytochrome c. The effects of the amount of C-dots, the pH value, and the persulfate concentration were optimized. Under the optimal conditions, the ECL signals (generated at -1.4 V) increase linearly with the concentration of cytochrome c in the range from 1.0 nM to 10 mu M, with a detection limit of 0.2 nM. The modified electrode exhibits high sensitivity and good selectivity.