Dual-peak electrogenerated chemiluminescence of carbon dots for iron ions detection

Carbon dots (CDs) have rigorously been investigated on their unique fluorescent properties but rarely their electrogenerated chemiluminescence (ECL) behavior. We are here to report a dual-peak ECL system of CDs, one at -2.84 V (ECL-1) and the other at -1.71 V (ECL-2) during the cyclic sweep between -3.0 and 3.0 V at scan rate of 0.2 V s(-1) in 0.1 M tetrabutyl ammonium bromide (TBAB) ethanol solution, which is more efficiency to distinguish metallic ions than single-peak ECL. The electron transfer reaction between individual electrochemically reduced nanocrystal species and coreactants led to ECL-1, in which the electron injected to the conduction band of CDs in the cathodic process. Ion annihilation reactions induced direct formation of exciplexes that produced another ECL signal, ECL-2. ECL-1 showed higher sensitivity to the surrounding environment than ECL-2 and thus was used for ECL detection of metallic ions. Herein, we can serve as an internal standard method to detect iron ions. A linear relationship of the intensity ratio R of ECL-1 and ECL-2 to iron ions was observed in the concentration extending from 5 × 10(-6) to 8 × 10(-5) M with a detection limit of 7 × 10(-7) M.