Electrochemical Detection And Application Research Of Several Small Organic Molecules

Chemical modified electrodes are promising for the analysis of small organic mol-ecules due to their advantages of convenience, rapidity, low cost and ease of miniatur i-zation. In the proposed dissertation, nanomaterial-based modified electrodes were suc-cessfully constructed for the detection of several organic molecules including5-methylcytosine (5-mC), cytosine (C), guanine (G), adenine (A) and thymine (T) withsatisfactory results, indicating that the system could provide an effective platform forthe research of genetic information.First of all, the fundamental conception and research progress of DNA methylation,the fabrication methods and applied fields of chemical modified electrodes were re-viewed. The research background, significance and contents of the dissertation weresummarized.Secondly, an efficient electrochemical approach for the evaluation of DNA meth-ylation level was proposed according to the oxidation signal of DNA bases at an ove r-oxidized polypyrrole (PPyox) directed multiwalled carbon nanotubes (MWNTs) filmmodified glassy carbon electrode (GCE). The methylation status of salmon sperm DNAsample was efficiently detected within45min without the need for bisulfite conversion,enzyme digestion or labeling procedures. Moreover, the signal interference of T, whichmarkedly blocked the electrochemical exploration of DNA methylation, was success-fully eliminated by an innovative strategy based on the stoichiometric relationship be-tween purine and pyrimidine bases in DNA molecular structure.Thirdly, simultaneous detection of G and A was realized at a choline (Ch) mono-layer supported MWNTs film modified GCE. The MWNTs/Ch film exhibited remarka-ble electrocatalytic activities towards the oxidation of G and A due to the advantages ofhigh electrode activity, large surface area, prominent antifouling property, and highelectron transfer kinetics. As a result, the proposed method exhibited good performanc-es of higher sensitivity, wider linear range and lower detection limit for the analysis ofpurine bases.Finally, in order to investigate the construction mechanism of Ch monolayer modi-fied GCE, an electrochemical sensor for the detection of nitrite was developed by elec-trodeposition of gold-platinum alloy nanoparticles on Ch/GCE. The interfacial proper- ties of nano-AuPt/Ch/GCE was characterized by field emission scanning electron mi-croscope (FE-SEM) and X-ray photoelectron spectroscopy (XPS), indicating that Chmonolayer could provide a suitable supporting substrate and favorable local microenvi-ronment for the construction of nanomaterials, which are of great siginificance for thedetection of small organic molecules.