Ratiometric electrochemiluminescence biosensor based on Ir nanorods and CdS quantum dots for the detection of organophosphorus pesticides

Abstract

The poor solubility and limited ECL emission efficiency of iridium (Ir) complexes in aqueous restricted their application in ECL field. This work prepared water-soluble Ir nanorods (Ir NRs) via carboxyl-functionalizing tris (2-phenylpyridine) iridium(Ⅲ) (Ir(ppy)3) using poly(styrene-co-maleicanhydride) (PSMA) and further developed a highly sensitive dual-signal nanoprobe with Ir NRs as anodic emitter and CdS quantum dots (QDs) as cathodic emitter. Ir [email protected] QDs served as the matrix to immobilize enzymes to construct an ECL ratio biosensor for detecting organophosphorus pesticides (OPs). The dual-functional H2O2 produced by enzymatic reaction had an opposite effect on two ECL signals, namely enhanced the cathodic signal and quenched the anodic signal. With the OPs, the activity of enzyme was inhibited and the generation of H2O2 was prevented, thus the opposite changes of two ECL signals were detected. The detection of ethyl paraoxon (EP) as target OPs was achieved with a linear range from 5.0 × 10−12 to 5.0 × 10−8 M and detection limit was 1.67 × 10−12 M. The excellent solubility and high ECL efficiency of Ir NRs in aqueous greatly expanded the application of Ir(Ⅲ) complexes. The opposite effect of H2O2 on two emissions of Ir [email protected] QDs provided a novel ratio ECL platform for bioanalysis.