Gold Nanomaterial Modified Electrode By Electrodeposition And The Application In DNA Electrochemical Sensing

In this thesis, the nanomaterial modified electrodes with novel morphologies were prepared by electrodepositon techniques. The applications of the modified electrodes in DNA biosensor fabrication and electrocatalytic oxidation toward methanol were studied in detail. The main contents are listed below:1. In chapter two, A simple one-step electrodeposition method was used to fabricate various gold nanostructures on gold electrodes in a low concentration of HAuCl4 solution (5 mM) under a potential of 0.5 V. The morphologies of final gold nanostructures can be easily controlled by varying the pH of the precursors. Hierarchical waxberry-like gold nanostructures with high active surface areas were obtained in pH 5 bath. The whole DNA biosensor fabrication process was characterized by cyclic voltammetry (CV) or electrochemical impedance spectra (EIS) with the use of ferricyanide as the electrochemical redox indicator. The DNA immobilization and hybridization on the modified electrode was further studied with CV and differential pulse voltammetry (DPV) methods by using Ru(NH3)63+ as an electrochemical hybridization indicator. The fabricated DNA biosensor was proved to have a low detection limit of 1×10-11 M toward complementary target DNA and with a high stability and reusability.2. In chapter three, a dendritic gold nanostructure (DenAu) modified electrode was obtained by direct electrodeposition of planar electrode into under a very negative potential of ?1.5 V. The growth evolution of DenAu with time and mechanism was carefully investigated. The surface area of the DenAu modified electrode is about 8.3 times compared with that of planar gold electrode. The probe DNA immobilization and hybridization with target DNA on the modified electrode could be well distinguished by using methylene blue as an electrochemical hybridization indicator. The DenAu modified electrode could realize an ultra sensitivity of 1 fM toward complementary target DNA and a very wide dynamic detection range (from 1 fM to 1 nM).3. In chapter four, an electrochemical alloying/dealloying process was employed to prepare a novel three-dimensional nanoporous gold electrode (NPG). The electrode morphology was controlled by changing the solution temperature and process cycles. Furthermore, the Pt nanoparticles modified NPG (Pt-NPG) was obtained by an immersion and electroreduction (IE) strategy. A very well electrocatalytic acticity of Pt-NPG toward metananol electro-oxidation in alkaline solution was achieved for the optimized electrode. The current novel Pt-NPG is expected to receive a lot of applications in direct methanol fuel cell.