| Piezoelectric quartz crystal (PQC) sensor can detect the kinetic changes in mass loading on the surface of an electrode down to nanogram or a single layer of molecule, and provide the information about the effect of non-mass loading or impedance on PQC resonance. Combination technique of piezoelectric quartz crystal impedance (PQCI) with electrochemistry is capable of proving multidimensional piezoelectric quartz crystal information of the investigated system. Infrared spectroelectrochemistry can characterize an electrochemical process at the molecular level by acquiring real time information about molecular structure of related species.Based on PQCI and in situ infrared spectroelectrochemistry, the method of piezoelectric quartz crystal impedance in combination with electrochemical impedance and further with in situ infrared spectroscopy, namely piezoelectric infrared spectroelectrochemistry, has been established. The new technique can provide multidimensional information of piezoelectric quartz crystal resonance and molecular structure of related species of the investigated system. In this thesis, the combined technique of PQCI with electrochemistry has been used to study protein adsorption on the newly prepared polymer or the surfaces of layer-by-layer assembled film, to monitor the interaction between tannic acid and the immobilized BSA. The polymerization of aniline and aniline-co-o-aminophenol, and the electrochemical behavior of o-tolidine were also investigated using piezoelectric infrared spectroelectrochemistry. The main work is summarized as follows:1. The recent researches using piezoelectric quartz crystal sensor and in situ FTIR spectroelectrochemistry were briefly reviewed.2. A new method for preparing the hydrophobicity-controllable modified electrode was proposed. A series of modified electrodes using polypyrrole (PPY) doped with dodecyl benzene sulfonate (DBS) were prepared. Combined measurements of piezoelectric quartz crystal impedance and electrochemical impedance were utilized to monitor in situ adsorption of two proteins (bovine serum albumin and fibrinogen) onto the prepared surfaces. Three of these modified electrodes, PPY/DBS-I, PPY/DBS-II and PPY/DBS-III, which were obtained by galvanostatic electropolymerization of pyrrole in aqueous solutions containing 0.6, 1.2 and 2.0 mmol/L sodium dodecyl benzene sulfonate (SDBS), respectively, showed that their hydrophobicity were different, and PPY/DBS-II exhibited the largest hydrophobicity. The adsorption of BSA on these three surfaces was the "end-on" adsorption, which can be explained with Langmuir model. Anyway, fibrinogen showed a multilayer adsorption.3. Combined measurements of piezoelectric quartz crystal impedance and electrochemical impedance were utilized to in situ monitor the adsorption of bovine serum albumin (BSA) onto the newly prepared Au colloid-modified electrode and study the binding of tannic acid (TA) to the immobilized BSA. The time courses of the resonant frequency and the equivalent parameters of the sensor were obtained simultaneously. The results showed that the molar binding ratio of TA tn BSA obtained from the frequency shift of the adsorbed BSA and tannin was estimated to be 10.3:1. Based on the frequency decrease with time, the kinetics of thebinding was also quantitatively studied. The binding equilibrium constant4. A new method of in situ piezoelectric infrared spectroelectrochemistry, i.e., a combination of in situ FTIR and electrochemical quartz crystal microbalance (EQCM), was developed to study the electropolymerization of aniline and aniline-co-o-aminophenol, and to investigate the oxidation-reduction properties of the polymers in 0.2 mol/L HC1O4. The piezoelectric electrochemical studies showed that the molar ratio of 0-aminophenol affected the copolymerization speed. The effects of scan rate and pH values on the electroactivity of the copolymer were also investigated. The results obtained from in situ piezoelectric FTIR spectroelectrochemisty indicated that the copolymerization process and the properties of the copolymer were different from that of polyaniline. The copolymer formed through head-to-tail coupling of the two monomers via -NH- groups was a new polymer rather than a mixture of polyaniline and poly-o-aminophenol.5. In situ piezoelectric infrared spectroelectrochemistry was used to study the electrochemical behavior of o-tolidine on the gold electrode. The result showed that the oxidation of o-tolidine in the BR buffer solution was greatly affected by potential. If the potential range was set at 0-0.4 V, the charge transfer compound was formed and dissolved during the potential scanning, and the frequency response was shown in a type of "v". While the potential was scanned up to 0.6 V or higher, the charge transfer compound was found to formed and dissolved during the potential scanning, and some of them were also found to deposit at the electrode surface at the same time. The in situ piezoelectric infrared spectroelectrochemistry showed that o-tolidine was oxidized and thecharge transfer compound was formed during the potential scanning. The large ion affected o-tolidine oxidation doping into the charge transfer compound.
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