Study On Electrochemical Properties Of Multi-ferrocenyl Complexes And Sensing Properties Of The Gold Electrode Modified With Polydopamine Derivative Monolayer

An electrical double layer (EDL) on electrode is a structure formed on the interface between electrode surface and electrolyte solution. Electrochemical reactions happen in EDLs, and its thickness is nano-sized. For a long time, the size of objective molecules is smaller than the thickness of EDLs, so the influence of molecular size and structure is neglected. Since bulky molecules including biomacromolecules, dendritic molecules and polymer molecules whose size is comparative to the thickness of EDLs have been the research hot spots, the molecular size and structure should have influence on its electrochemical properties. Researches on electrochemistry of macromolecules mainly focus on the number of electrons transferred as well as the.influence of electrostatic effect on complexes with multi-redox-center, however, there is little research on the influence of molecular size and structure on its electrochemical properties.A chemically modified electrode (CME) is an electrode designed by chemical modification on electrode surface. CMEs have specific chemical and electrochemical properties, and its selectivity and sensibility are enhanced. Polydopamine coating is an extremely versatile platform for secondary reaction. For its remarkable properties and ease of preparation, the polydopamine coating was widely employed in electroless metallization and creation of functional organic ad-layers. If the polydopamine film is used on electrode surface for its adhesive property, the application of CMEs will be enlarged.To investigate the influence of bulky molecular size and structure on its electrochemical properties, multiferrocenyl complexes with different sizes and different number of ferrocenyl units were employed. The number of electrons transferred in one complex was calculated through the result of voltammetry, which was less than that of redox centers. The thickness of EDLs was adjusted by changing concentration of electrolyte. We investigated the influence of EDLs on electrochemical properties of macromolecules, and detected the influence of molecular size and structure on its electrochemical properties. Besides, we focused on researches about a gold electrode modified with polydopamine derivative monolayer. The polydopamine derivative monolayer was formed on the surface of a gold electrode, and a new method to modify electrode by utilizing the adhesive property of polydopamine derivatives was established. The efficiency of this secondary reaction surface was proved, for the horseradish peroxidase (HRP) that was adhered on polydopamine derivative monolayer could catalyze the redox of hydrogen peroxide (H2O2) successfully.This paper is composed of the following three chapters. Chapter One:PrefaceThe structures of EDLs and corresponding theoretical simulations were shown to describe the significance of EDLs’structures to electrochemical reaction. The electrochemical research on bulky molecules was included. Besides, the developing situation of CMEs and the electrode modification methods was described in this chapter. It also introduced the analytical methods used in electrochemistry. Eventually, this chapter stated the purpose or significance of the research. Chapter Two:Research on electrochemical properties of multi-ferrocenyl complexesThis chapter showed the influence of bulky molecular size and structure on its electrochemical properties. A family of multiferrocenyl complexes were employed. The three kinds of complexes were rings, and had 2,3,6 ferrocenyl units respectively. There was no communication among redox centers for the complexes, and every redox center could react separately. The number of electrons transferred in one complex was calculated through the result of voltammetry, which was less than that of redox centers. Besides, the thickness of EDLs was adjusted by changing the concentration of electrolyte, and the influence of bulky molecular size and structure on its electrochemical properties was detected further.Chapter Three:Research on sensing properties of the gold electrode modified with polydopamine derivative monolayerThis chapter focused on the construction and application of an electrode modified by polydopamine derivative monolayer. Thiol dopamine derivatives were modified on gold electrode surface by S-Au covalent bonding and dopamine derivative monolayer was formed. Through electro-polymerization, the polydopamine derivative monolayer was developed. The polydopamine derivative was used as secondary reaction surfaces to develop a new electrode modification method for its adhesive property. Besides, influence of pH value on the formation of polydopamine monolayer was also detected, and the optimal pH value to form polydopamine derivative monolayer was found. HRP was adhered on polydopamine derivative monolayer and it could catalyze the oxidation of H2O2, which proved the efficiency of this secondary reaction surface and supported theory evidence for its application in the future.