Design Of Functional Molecule Conductor And Its Application In Direct Electrochemistry Of Enzyme

Molecular wires with small size and variable properties have received increasing attention in many fields such as chemistry, biomedical sciences, molecular electronics. Design and construction of molecular wires for specific enzyme molecules to achieve direct electron transfer between the enzyme and the electrode, which has an important significance for the development of the third-generation electrochemical biosensors and the efficient biofuel cells. This dissertation focuses on developing molecular wires with speical functionalized ends and size and investigation of its application in the direct electrochemistry of enzymes. The details are summarized as following:1. Research of single-walled carbon nanotubes (SWCNT), which was chemically tailored and covalently functionalized via various methods, along with deep analysis of its corresponding electrical properties. The tailored and functionalized SWCNT was characterized by transmission electron microscopy (TEM) and fourier transform infrared spectroscopy (FTIR), while four point probe resistivity measurements at different temperatures based on prepared specific SWCNT membrane was carried out for the characterization of its electrical propertyies. More experiments were done to investigate the possible applications of the as-treated SWCNT acting as molecular wires for the direct electrochemistry of immobilized enzymes. The experimental results show that:1) The SWCNT could be effectively tailored by binary acid mixture, leaving semi-conducting SWCNT (s-SWCNT) dominated. The average length of the cutting SWCNT prepared at optimal experimental conditions was 600 nm with desired solubility in aqueous media; 2) The OH-functionalized SWCNT short in length performed well as molecular wires for control and oriented immobilization of laccase. The immobilized Laccase showed good electrocatalytic activity for the reduction of O2.2. Investigation of as-prepared s-SWCNT acting as molecular wires in the application of the direct electrochemistry of immobilized enzymes. s-SWCNT with average length of 600 nm was synthesized as described above. Myoglobin (Mb) was selected as a model enzyme to investigate the potential application of the prepared s-SWCNT for direct electrochemistry of immobilized enzymes, where s-SWCNT was used as molecular wires. The results of the FTIR and ultraviolet-visible absorption spectroscopy (UV-Vis) indicated that the immobilized Mb still retained its nature conformation even after adsorption. The electrochemistry results showed that the s-SWCNT modified electrode with immobilized Mb underwent direct electron transfer and performed excellently to the reduction of H2O2 and O2 with a wide linear range (0.62-44 μM) and a low detection limit (0.3 μM) for detection of H2O2. The as-prepared Mb-modified electrodes based on s-SWCNT was stable with high repro-ducibility. By contrast, while Mb was immobilized via the pristine SWCNT, the immobilized enzyme, with obvious change in the conformation, had no significant electrocatalytic activity for the reduction of H2O2.3. Investigation of s-SWCNT/nano-gold composite electrodes in the application of the direct electrochemistry of immobilized enzymes. By one-step in situ reduction approach, water-soluble gold nanoparticles (AuNPs) with mean diameter of 3.5 nm was synthesized under optimized conditions. Preparation of s-SWCNT/AuNPs nano-composite molecular wires and investigation of its application in the direct electrochemistry of immobilized enzymes was carried out. The electrochemistry results indicated that s-SWCNT/AuNPs nano-composite molecular wires could promote the effective direct electron transfer between Mb and the glassy carbon electrode. s-SWCNT/AuNPs modified electrode displayed excellent electrocatalytic activity toward the reduction of H2O2 and O2. The resulting Mb-modified electrodes based on s-SWCNT/AuNPs nanocomposites exhibited a wider linear range (0.25～49 μM), lower detection limit (0.13 μM) and better stability for the detection of hydrogen peroxide, when compared to the s-SWCNT-based modified electrodes.