EIS Characterization Of Alkanethiol Self Assembled Monolayers On Au Surface And Investigation Of Immunosensor

Self-assembled monolayers (SAMs) derived from the adsorption of alkanethiol on gold electrodes have been extensively studied over the past three decades due to their ease of preparation, high-density accumulation, perfect structure, stability performance which has been used for many different areas, such as biochemical analysis, electronic devices, antisepsis, etc showing a broad applied prospect. The design flexibility of SAMs technique allows for the immobilization of biological macromolecules and living organisms, such as cells, proteins, antibodies, DNA, etc. These studies apply simple and effective technique for investigating biosensor and its application. The characterization of SAMs is the important content of molecule-assembled technique. Especially real-time in-situ characterization of SAMs technical research is the problem starved for resolving. In this paper electrochemistry impedance spectroscopy(EIS) was used to track the film-forming process of the thiol SAMs3-Mercaptopropionic acid(MPA) and11-mercaptoundecanoic acid(MUA) on gold electrodes. Investigate different longth of alkyl chain alkanethiol by real-time in-situ characterization. SAMs of aromatic thiols are of interest owing to their higher rigidity and the presence of delocalized π-electrons in the aromatic ring. There are some scattered reports on SAMs of aromatic thiols in biosensor. In this paper,we report our studies on the applications of potentiometric immunosensor by electric potential controlling of Ab on4-aminothiophenol (4-ATP) modified gold electrode for detection of IgG. The major contents in this thesis are described as follows:1、 EIS characterization of MPA self assembled on Au surface in aqueous solutionMPA can dissolve in water, this apply a convenience of real-time in-situ characterization of its film-forming process. In water,KCl and [Fe(CN)6]3-/4-were used as support electrolyte and redox probe respectively, EIS was used to characterize MPA film-forming process on Au surface real-time in-situ. The conditions of experiment were optimized and studied the influence of solvent on MPA film-forming process.The results show that the optimized conditions of charactering MPA film-forming process are at open circuit potential, in the100mmol·K-1Cl and5mmol-L-1[Fe(CN)6]3-/4-. When the concentration of MPA is more than6mmol-L·L-1, the film-forming process no longer changes. 2、 EIS characterization of MUA self assembled on Au surface in propylene carbonate solutionLong alkyl chain MUA do not easily dissolve in water. We choose propylene carbonate as electrolyte solution in this chapter through comparing. NaC104and ferrocene were used as support electrolyte and redox probe. A new method of real-time in-situ characterization was built to character the process of MUA self assembled on Au surface. The conditions of experiment were optimized. The results show that at0.25V applied ac bias potential, the concentrations of NaClO4and ferrocene were respectively300mmol·L-1and15mmol-L-1is the best condition of charactering the process of MUA film-forming process. When the concentration of MUA is more than5mmol·L-1, the film-forming process no longer changes.3、A Potentiometric Immunosensor Based on Electric potential control of antibodies immobilization on gold electrodeImmunosensor has a broad application prospect for many different areas, such as clinical diagnoses, food analysis, environmental protection, military affairs, physic, etc. The immobilizations of antibody and antigen are the the key to investigat biosensor and its application. In this chapter,a new method of electric potential controlling to immobilize antibody was proposed. Goat Anti-Rat immunoglobulin G was immobilized on gold electrode modified by mixing monolayers of4-aminothiophenol(4-ATP) and3-Mercaptopropionic acid(MPA),which used the method of electric potential controlling to develop a Ab/4-ATP and MPA SAMs/Au. The immunosensor was used to detect the antigen in the solution, it was found that the biosensor had a high sensitivity on the preparations(potention-200mV, immobilized time20min, pH3.0PBS). The linear calibration range starting extending over5orders of magnitude of Ag concentrations (1x10-4to10ng/mL), life time for above15d.