Studies On Electrochemical Properties Of The Polyoxometalates Modified Electrodes

Recently, the considerable interests have been focused on polyoxometalates (POMs) clusters not only due to their special intrinsic structure but also due to their potential application in the field of material science, catalysis, biology and medicine. In order to promotes their applications in electrocatalytic research, develop some novel fabrication method to immobilize POMs on electrodes is a new challenge in this fields. The present reaserch work focused on the selecting and optimizing materials, improving immobilizing methods, and designing several types of novel polyoxometalates modified electrodes. The main points of this dissertation are addressed as follows:1. Electrochemical behavior and its electrocatalytic properties of chemically modified electrode with Keggin-type [SiNi(H2O)W11O39]6?A monolayer of Keggin-type heteropolyanion [SiNi(H2O)W11O39]6? was fabricated by electrodepositing [SiNi(H2O)W11O39]6? on cysteamine modified gold electrode. The monolayer of [SiNi(H2O)W11O39]6? modified gold electrode was characterizedby atomic force microscopy (AFM) and electrochemical method. AFM results showed the [SiNi(H2O)W11O39]6? uniformly deposited on the electrode surface and formed a porous monolayer. Cyclic voltammetry exhibited one oxidation peak and two reduction peaks in 1.0M H2SO4 in the potential range of ?0.2 to 0.7 V. The constructed electrode could exist in a large pH (0–7.6) range and showed good catalytic activity towards the reduction of bromate anion (BrO3?) and nitrite (NO2?), and oxidation of ascorbic acid (AA) in acidic solution. The well catalytic active of the electrode was ascribed to the porous structure of the [SiNi(H2O)W11O39]6? monolayer.2. A Novel Sensor Based on Layer-by-Layer Hybridized Phosphomolybdate and Poly(ferrocenylsilane) on a Cysteamine Modified Gold ElectrodeA novel sensor have been constructed by layer-by-layer hybridizing phosphomolybdate (POM) and poly(ferrocenylsilane) (PFS) on a cysteamine modified gold electrode. The properties and performance of the sensor have been measured by electrochemistry and atomic force microscopy in detail. The results showed that the constructed multilayers modified gold electrode combined the properties of POM and PFS, and exhibited good electrocatalytic ability to a series of inorganic ions, including BrO3-﹑IO3-﹑NO2-﹑Fe3+﹑ascorbic acid and SO32-. The well catalytic activity of the sensor was ascribed to the porous structure of hybrid POM-PFS multilayer. The resulted sensor exhibited extremely fast amperometric response, low detection limit, high selectivity and wide linear range to these analyses. 3. Type I Collagen /Polyoxometalate Composite Films on Cysteamine Modified Gold Electrode and Its Electrocatalytic PropertiesA novel multilayer of the type I collagen and PW12O403- was successfully fabricated. The type I collagen was firstly assembled on cysteamine modified gold electrode to form a network and then PW12O403- was electrodeposited on the modified electrode. By recycling the assembly and electrodeposition, the PW12O403- (collagen-PW12O403-)n modified electrode was prepared. Electrochemistry and atomic force microscopy (AFM) were used to characterize the PW12O403- (collagen-PW12O403-)n multilayer. AFM results showed that the PW12O403- preferentially deposited on the collagen network to produce the PW12O403- network. Electrochemical experiments results showed that the resulted electrode exhibited good electrochemical and electrocatalytic properties towards the reduction of nitrite. The electrochemical and electrocatalytic properties of modified electrode were investigated in detail.4. A Novel Strategy for the Construction of Polyoxometalate Modified Electrode and Its Electrochemical BehaviorsA novel polyoxometalate modified electrode is fabricated by immersing the gold electrode in the benzene solution of phthalocyanatocobalt(II), the solution of poly(ferrocenylsilane) and the solution of Keggin-type [SiNi(H2O)W11O39]6- stepwisely. The properties of the modified electrode have been investigated by atomic force microscopy (AFM) and electrochemical methods. AFM results show the modified electrode has been successfully covered by the three materials. The resulted electrode has good catalytic activity towards the reduction of oxygen (O2) and oxidation of uric acid.