Fabrication And Sensing Of Vanadium-substituted Polyoxometalates Composite Film

Two composite films based on H₆[PMo₉V₃O₄₀] decorated by Ptnanoparticles and K₈P₂W₁₆V₂O₆₂·18H₂O decorated by Au-Pd nanoparticles wereprepared by the layer-by-layer self-assembly method. First, the particle size ofthe particles was detected by Transmission Electron Microscopy.The growthprocess of the composite film was monitored by UV-vis spectroscopy. X-rayphotoelectron spectra were qualitative analysis of the elemental composition ofthe film and proved the presence of PMo₉V₃, Pt and PEI in the composite film.Surface morphology was surveyed by atomic force microscopy. Result shows thata mass of dispersed particles can be observed on the surface of the film. Thethickness of the composite film was detected by Scanning Electron Microscope.Electrochemistry experiments revealed that the sensing properties of thecomposite films were markedly enhanced.1In the phosphate buffer solution （pH=6.5）, the {PEI/（PMo₉V₃-Pt/PEI）₈/PMo₉V₃-Pt} composite film exhibited high sensitivity of1.2μM/μAdopamine, fast response time （<1s）, low detection limit (～1.3×10^-7M), and awide linear range from4.2×10^-7to1.3×10^-3M toward amperometric sensingof dopamine, as well as no interference from the common interfering speciessuch as ascorbic acid, glucose, uric acid, L-cysteine and H2O2.2At physiological conditions, the {PEI/（P2W16V2-AuPd/PEI）8/P2W16V2-AuPd} composite film can be performed for the ascorbic acid and dopamine withgood catalytic at potential of+0.3V and+0.8V by the differential pulsevoltammetry. The slopes of the linear calibration curves between the peak currentand the concentration were estimated to be1.92and0.62μM/μA for DA and AA.The linear range of the concentration for the determination of DA and AA were2.1×10^-62.06×10^-3M and1.2×10^-61.61×10^-3M, respectively. Theresponse time of DA and AA were found0.6and0.9s. The low detection limit for DA and AA were8.3×10^-7and4.3×10^-7M, as well as no interference fromthe common interfering species such as glucose, uric acid and L-cysteine,CH₃OH, CH₃CH₂OH and H₂O₂.3The real serum sample analysis indicates the possible use of thesecomposite films as a potential candidate for routine dopamine and ascorbic acidanalysis. These electrochemical sensors have the advantage of ease ofpreparation over electro polymerization methods, and also have the advantage ofcontrol of layer thickness over sol-gel methods.