Electrochemical detection of chlorpyrifos in fruits with gold-histidine functionalized graphene quantum dot-graphene hybrid and target-induced DNA cycle amplification

Abstract

Hybrid of gold and graphene may improve the electrochemical performances due to their unique structure and properties, but synthesis of gold-graphene hybrid with ideal dispersion and catalytic activity still faces great challenges. The paper describes synthesis of gold-graphene hybrid using histidine-functionalized graphene quantum dot (His-GQD) as the linker between gold and graphene and semiconductor. Firstly, His-GQDs were immobilized on graphene sheets via π-π stacking. Then, it coordinated with Au3+ and thermally reduced in N2. The resulting Au-His-GQD-G offers small gold nanoparticles, good dispersion and Schottky heterojunction. The Au-His-GQD-G was used for construction of electrochemical sensor for detection of chlorpyrifos coupled with DNA cycling signal amplification. Chlorpyrifos was hybridized with aptamer DNA in duplex DNA to release auxiliary strand DNA, triggering the DNA cycle. By the DNA cycle, one target molecule can bring many ferrocene probes to the electrode surface. This produces a significant signal amplification. Differential pulse voltammetric current increases linearly with the increase of chlorpyrifos in the range of 1 × 10−16-1.0 × 10−11 M with the detection limit is 3.8 × 10−17 Μ (S/N = 3). The proposed method exhibits ultrahigh sensitivity and selectivity and was successfully applied in electrochemical detection of chlorpyrifos in fruits.