Synthesis of core-shell structured Au@Bi2S3 nanorod and its application as DNA immobilization matrix for electrochemical biosensor construction

The core-shell structured Au@Bi₂S₃ nanorods have been prepared through direct in-situ growth of Bi₂S₃ at the surface of pre-synthesized gold nanorods. The product was characterized by X-ray diffraction, transmission electron microscopy and energy-dispersive X-ray spectroscopy. Then the obtained Au@Bi₂S₃ nanorods were coated onto glassy carbon electrode to act as a scaffold for fabrication of electrochemical DNA biosensor on the basis of the coordination of -NH₂ modified on 5'-end of probe DNA and Au@Bi₂S₃. Electrochemical characterization assays demonstrate that the Au@Bi₂S₃ nanorods behave as an excellent electronic transport channel to promote the electron transfer kinetics and increase the effective surface area by their nanosize effect. The hybridization experiments reveal that the Au@Bi₂S₃ matrix-based DNA biosensor is capable of recognizing complementary DNA over a wide concentration ranging from 10 fmol/L to 1 nmol/L. The limit of detection was estimated to be 2 fmol/L (S/N=3). The biosensor also presents remarkable selectivity to distinguish fully complementary sequences from basemismatched and non-complementary ones, showing great promising in practical application.