Fabrication And Characterization Of Dawson-type Vanadium-substituted Phosphotungstate Composite Film

In this work, the {PEI/[P₂W₁₇V/CdS-PEI]_n} composite films of Dawson-type vanadium-substituted phosphotungstate/CdS nanoparticle and the{PEI/PSS/[PDDA/P₂W₁₇V-CNTs]_n} composite films of Dawson-type vanadium-substituted phosphotungstate/carbon nanotube are fabricated successfully bylayer-by-layer assembly. UV-visible spectrum is used to monitor the film growthprocess. The results show that the growth of composite films is repeated, uniform.The atom force microscope is applied to study the surface morphology ofcomposite films. The images indicat that the nanoparticles is uniformly andsmoothly distributed on the film surface.UV-visible spectrum monitors the absorbance alteration of the methyleneblue solution in the irradiation of250W high pressure UV lamps to examine thephotocatalytic property of {PEI/[P₂W₁₇V/CdS-PEI]_n} films. When pH=5.5,5mmol of BrO₃-concentration and the catalytic time of70min, the catalyticefficiency of {PEI/[P₂W₁₇V/PEI]_n},{PEI/[PSS/CdS-PEI]_n} and{PEI/[P₂W₁₇V/CdS-PEI]_n} three composite films are74.30%,82.58%and98.55%,{PEI/[P₂W₁₇V/CdS-PEI]_n} composite films show more excellentphotocatalytic properties, and when the P₂W₁₇V concentration of composite filmsis4mmol, the film show the best photocatalytic effect which can reach98.80%.The electrochemical properties of the composite films are studied by cyclicvoltammetry. We investigate that the electrochemical properties of{PEI/PSS/[PDDA/P₂W₁₇V-CNTs]_n}composite films in different types of thebuffer solutions with different pH values. The experimental results show thatelectrochemical properties are the best in pH=7.0,0.1mol phosphate buffer solution. And the composite films in the above solution catalyzed dopamine,ascorbic acid and uric acid. The {PEI/PSS/[PDDA/P₂W₁₇V-CNTs]_n} compositefilms have excellent catalytic activity for ascorbic acid. The sensitivity ofcatalytic oxidation is0.3μA·μmol-1, the linear range is7.59³8.43μmol, itsdetection limit is about5μmol, response time is about5s and correlationcoefficient is0.9953. Comparative study finds that the films is not response toascorbic acid and uric acid, so it can be applied to the detection of dopamine inthe three coexist system. In addition, the UV-visible spectrum absorbance offilms does not change significantly in the temperature range of-20¹40℃,indicating good stability of the films for temperature.