Chemically modified electrodes with nanocatalysts and their layer-by-layer self-assembled nanothin films: Preparation, characterization and application

The objective of this thesis is to develop high performance electrochemical sensors with high sensitivity and selectivity for the determination of biologically important redox-active species. Various electrocatalysts of manometer size were immobilized onto electrode surfaces by new techniques such as layer-by-layer self-assembly. The properties of the modified electrodes were characterized by a line of physical techniques. The applications of our modified electrodes in biosensors were systematically explored in both chemical and biological media.; Chapter 2 describes preparation, characterization and application of the electrodes modified with namo-scale mixed-valence transition metal oxide films, including hydrous ruthenium oxide (RuO₂·2H₂ O) and molybdenum oxide films. The GCE-(RuO₂·2H ₂O)_n film exhibits an excellent electrocatalytic property in the oxidation of ascorbic acid and oxidation/reduction of hydrogen peroxide. Analytical applications of the GCE-(RuO₂·2H₂O) _n as sensors for ascorbic acid and glucose are demonstrated.; Chapters 3 and 4 present the syntheses, characterization, and applications of the inorganic-inorganic multilayer films self-assembled alternatively from polyoxometalates (POM) and transition metal ammine complexes (MN). FT-IR spectra further demonstrated the layer-by-layer self-assembly of alternating layers and the hydrogen bond interaction between molecules. Two novel non-metal oxide-substituted POMs (P₂W₁₇SO₆₁4− and P₂W₁₇PO₆₁5−) were electrochemically synthesized for the first time. Various transition metal ion and lanthanide (or actinide) ions can be incorporated into lacunary POMs by electrochemical method, which is a simple but powerful method to synthesize new polyoxometalates. In chapter 5, the very stable multilayer films have been developed from POMs and organic macrocycles such as MPP, MPc, and ME.; Chapter 6 focuses mainly on the development of biosensors for L-ascorbate and nitric oxide based on the films described in chapter 5. In addition, the films fabricated from MPP (or MPc) and POM can be employed to construct electrochemical sensors for several electroactive species at physiological pH. Particularly, GCE-(P₂W₁₈/CuPc)_n multilayer film exhibits an enhanced electrocatalytic activity towards the NO oxidation, as well as the O₂ and H₂O₂ reduction. In this system, we combined together the electrocatalytic reduction properties of P₂ W₁₈ to the O₂ and H₂O₂ and the electrocatalytic oxidation properties of CuPc to NO. The sensor was successfully utilized to monitor NO release from rate brain slice when a stimulator for NOS was injected. (Abstract shortened by UMI.)...