Electrochemical Biosensor Based on Au5ir@Graphene Quantum Dot Nanocomposite and DNA Walker for Detection of Atrazine in Environmental Water with Extremely High Sensitivity and Selectivity

Abstract

Existing electrochemical sensors are inadequate for pesticide analysis at extremely low level. The study describes an electrochemical biosensor based on Au5Ir@graphene quantum dot nanocomposite and DNA walker for detection of atrazine. Au5Ir was made via reduction of chloroauric acid and iridium trichloride with arginine and folic acid-functionalized boron and phosphorus-doped graphene quantum dot (RFBP-GQD). Synergy of Au and Ir and formation of Schottky heterojunction enhance the catalytic activity. It was covalently combined with hairpin DNA and thionin. The obtained redox probe was utilized to construction of electrochemical biosensor for detection of atrazine coupling with DNA walker. Atrazine can trigger the DNA walker and results in numerous redox probes being introduced to the gold electrode surface. Oxidation and reduction of thionin molecule in these redox probe elicit sensitive electrochemical response. Integration of Au5Ir@RFBP-GQD catalysis with DNA walker achieve significant signal amplification. The biosensor exhibits much better sensitivity and selectivity than other atrazine sensors. The detection signal linearly increases with the increase of atrazine concentration from 1×10-18 to 1×10-12 M with low detection limit of 3.4×10-19 M (S/N=3). The proposed method was satisfactorily applied in detection of atrazine in environmental waters.

Keywords: AuIr nanoalloy, DNA walker, Electrochemical detection, Water