| Due to the versatility of the sol-gel processes and its aqueous solution microenvironment, the sol-gel technique becomes an ideal method for film preparation. In 1990s, the sol-gel electrochemistry is progressing rapidly, and applied enough in devices,sensors and fuel batteries, and so on. At the present time, the development of new-type non-silica sol-gel materials for immobilizing electrochemical activity composition is a new trend.Because of possessing intriguing size-dependent properties, metal nanoparticles have unique electronic, optical, and catalytic properties, and become an ideal research objective in surface nano- engineering and functionalized nano- structures construction. They have wide application in microelectronic devices, sensor technology, and surface-enhanced Raman spectroscopy. The research of nanoparticles not only continues to focus on the nanoparticles themselves but also has recently expanded to exploring organized assemblies of nanoparticles on surfaces.In chapter 2 of this article, a novel nitrite sensor was developed based on the immobilization of a functional compound partially quaternized poly(4-vinylpyridine) complexed with [Os(bpy)2Cl]+/2+ (PVP-Os) in a porous TiO2 sol-gel matrix by a vapor deposition method. The preparation process simplified the traditional sol-gel process and prevented the cracking of conventional sol-gel derived glasses. The PVP-Os entrapped in titania sol-gel films retains its electrochemical activity and shows excellent electrocatalytic reduction for nitrite. The linear range for nitrite determination was from 5.0×10-6 mol/L to 9.5×10-4 mol/L with a detection limit of 4.0×10-7 mol/L. The uniform porous structure of the titania sol-gel matrixes results in a very small mass transport barrier and a fast response for nitrite. The promising sensor also exhibits good mechanical and chemical stability.In chapter 3, a new amperometric sensor was fabricated based on the immobilization of complex of Na2H6CoW11Co(H2O)O39·14H2O(CoW11Co)and poly(4-vinylpyridine) (PVP) in a TiO2 sol-gel matrix by vapor deposition method. The electrochemical behavior of the new amperometric sensor was studied in detail by cyclic voltammetry, and three reversible two-electron redox waves were observed in acidic aqueous solution in the potential range of -0.1 to -0.7 V. The sensor displays good electrocatalytic activity toward the reduction of bromate, iodate and hydrogen peroxide in acidic aqueous solution and the catalytic mechanisms were also discussed. The catalysis of the sensor toward bromate and iodate was systematically studied by amperometric method. The method gave a linear range from 2.0×10-5 to 4.4×10-3 mol/L and a detection limit of 5.0×10-6 mol/L for BrO3- and 2.0×10-6 to 2.8×10-4 mol/L and 8.0×10-7 mol/L for IO3-, respectively. In addition, the sensor has some distinct advantages over the traditional polyoxometalate sensor, such as simple preparation process, fast response and long-term stability.In chapter 4, by vapor deposition method, both myoglobin (Mb) and colloidal gold nanoparticles were entrapped in a titania sol-gel matrix on the surface of a glassy carbon electrode. This matrix provided a biocompatible microenvironment for retaining the native structure and activity of the entrapped Mb. The sensor showed a pair of well-defined and nearly reversible cyclic voltammetric peaks for the Mb Fe(III)/Fe(II) with a formal potential (E°') of -335 mV and the peak-to-peak separation was 61 mV vs. Ag/AgCl (3.0 mol/L KCl) at 100 mV s-1 in 0.1 mol/L pH 7.0 phosphate buffer solutions (PBS). The formal potential of the Mb Fe(III)/Fe(II) couple shifted linearly with pH with a slope of–51.3 mV/pH, indicating that an electron transfer accompanies single-proton transportation. The sensor displayed a good electrocatalytic response to the reduction of TCA and the catalytic mechanism was also discussed. The overpotential for the reduction of TCA was lowered by at least 0.8 V compared with that obtained at bare glassy carbon electrode. The linear range spans the concentration of TCA from 2.0×10-6 to 1.2×10-5 mol/L and the detection limit was 1.2×10-7 mol/L. This novel method is simple, convenient and versatile. Moreover, the biosensor had good long-term stability. In addition, the biosensor also possesses high sensitivity and good chemical and mechanical stability.In chapter 5, highly ordered gold nanoparticle multilayer films were achieved conveniently by using didodecyldimethylammonium bromide (DDAB) films as a template. The template was produced by casting DDAB chloroform solution onto the surface of an (3-aminopropyl)trimethoxysilane (APTMS)-modified indium tin oxide glass substrate and then evaporating the organic solvent. Gold nanoparticle multilayer films were prepared by soaking the template in 2.6 nm colloidal gold solution for 120 min. The well-ordered superlattice structure of the DDAB template and the gold nanoparticle multilayer films was identified by X-ray diffraction. The characterizations of the gold nanoparticle multilayer films by UV-Vis spectroscopy and atomic force microscopy and cyclic voltammerty were described in detail. The application of the as-prepared gold nanoparticle multilayer films in surface-enhanced Raman spectroscopy (SERS) was investigated by using Rhodamine 6G as a probe molecule. It was found that the colloidal gold nanoparticle multilayer films exhibit remarkable enhancement ability, and can be used as SERS substrates.In chapter 6, highly ordered silver nanoparticle multilayer films were achieved conveniently by using didodecyldimethylammonium bromide (DDAB) films as a template. The obtained thin films were characterized by UV-Vis spectroscopy, cyclic voltammerty and atomic force microscopy in detail. The well-ordered superlattice structure of the DDAB template and the silver nanoparticle multilayer films were also identified by X-ray diffraction. The application of the as-prepared silver nanoparticle multilayer films in SERS was investigated by using 4-mercaptopyridine as a probe molecule. It was found that the silver nanoparticle multilayer films exhibit remarkable enhancement ability, and can be used as SERS substrates.
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