| This thesis consists of three parts. Each part includes a review and a research report.With the development of genetics, DNA biosensor had gotten more and more attention. The studies on DNA become very important especially after the finish of genome. The prime research of DNA was based on the radial elements such as 32P, 3H as marker and DNA was analyzed by the half life of radial elements. Though this method has a very high sensitivity and a low limit (the common limitation is pg), it has a dreadful drawback, which is the radial pollution. Then many other methods were studied to replace the traditional way. Optic method and electric method was the main methods investigated on DNA study. Electrochemical DNA biosensors have attracted a great deal of interest and have become the subject of intense investigations. The electrochemical DNA biosensors perform simple, fast, specific and accurate monitoring with compact and user-friendly instrumentation to transform traditional methods of analysis. The study of electrochemical DNA biosensors is focused on finding new indicator and improving the immobilization methods.The keys to a successful electrochemical biosensor are the stability of the immobilization on the electrode and the sensitivity of the hybridization indicator.At the first part of this thesis, we researched the electrochemical behavior of thionine on the gold electrode immobilized with DNA by CV and EIS. The CV results of dsDNA showed a positive shift compared with that of ssDNA, which can be attributed to the special interaction between dsDNA and thionine. So thionine can be used as hybridization indicator.At the second part, two electrochemical DNA biosensors based on platinum electrode were investigated. To improve the immobilization technique, we use polyvinyl butyral (PVB) as matix to immobilize DNA on a platinum electrode and get a novel DNA electrochemical biosensor. This immobilization method is simple and efficient compared with the other method. To enhance the immobilization quantity on the electrode, we added Au colloids in PVB. Au colloids are a kind of nanoparticle, which can play an important role in adsorption of DNA for the large specific surface area and high surface free energy. In addition, colloidal gold provides an environment similar to the native environment of DNA, which is its good biocompatibility. This DNA biosensor showed a very good electrochemical character when studied by Cyclic voltammogram (CV) and electrochemical impedance spectroscopy (EIS). The detection limit of DNA sensor was 9x10-8 g/mL and sensor showed a very good stability stored at 4C. The other one DNA sensor was made on a gold electrode and thionine was used as hybridization indicator first time.Recently, study on solvent polymeric membrane (SPM) anion selective electrodes based on metal complexes as neutral carrier and exhibiting anti-Hofmeister selectivity pattern is an important project in the fields of electrochemistry and electroanalytical chemistry. Second part of the thesis focuses on the development of SPM anion selective electrodes based on new neutral carriers and their application as electrochemical sensors in food and medicine.A novel selective thiocyanate electrode of PVC membrane based on bis-[N-(2-hydroxy-ethyl) salicylaldimino] copper(II) [Cu(II)-BNSDM] as neutral carrier is reported. The selectivity sequence of this electrode is as follow: SCN"> C1O4- > I- > Sal- > Br- > NO2- > Cl- > NO3- > H2PO4- > SO4-, which is an anti-Hofmeister selectivity sequence. The electrode exhibits Nernstian potential linear range to thiocyanate from 1.0x10-1 to 6x10-6 mol/L with detection limit of 2x10-6 mol/L and a slop of-59.0 mV/decade in pH 6.0 of phosphorate buffer solution at 25 C . Electrochemical impedance spectroscopy (EIS) and UV-vis spectroscopy technique was performed to discuss the response mechanism of the electrode. Theother electrodes based on bis-[N-(2-hydroxy-ethyl) salicylaldimino] cobalt(II) [Co(II)-BNSDM] were observed. The electrode had the advantage of simplicity,... |
PDF Full Text Request