Fabrication And Research Of Electrochemical Sensors Based On Dawson-type Polyoxometalates Containing Vanadium To Detect Small Biological Molecules

As a new material, polyoxometalates nano-composite film were studied andapplied in varies of fields. Nevertheless, it also has a lot of development space basedon its excellent features, particularly in the field of electrochemical sensors. Twocomposite films {[PEI/PSS]₂/Au@2Ag/[PEI/P₂Mo₁₇V]₂} and {PEI/[(P₂W₁₇V-CuO)/（CS-Pd）]7/[P₂W₁₇V-CuO]} based on Dawson-type polyoxometalatescontaining vanadium were prepared by the layer-by-layer self-assembly method todetect small biological molecules L-cysteine and DA in this article.The UV-vis spectroscopy, X-ray photoelectron spectra （XPS） and atomic forcemicroscopy （AFM） were used to characterize the composition and surfacemorphology of films. The results show the uniform, stabilizing growth process andsmooth surface morphology of the two composite films, as well as the elementalcomposition of polyoxometalates and nanoparticles. Then, the electrochemicalbehavior of films was investigated by the measurements of electrochemicalimpedance spectroscopy （EIS）, cyclic voltammogram and amperometry. Theelectronic conductivity and catalytic properties of the composite films were enhancedgreatly because of the introduction of nanoparticles. By the measurement ofamperometric sensing of the two composite films, the results were obtained asfollows: the detection limit (～5.07×10^-6M), linear range from2.25×10^-7to1.82×10^-4M, response time （<2s） and sensitivity （0.0082μA/μM） for detectingL-cysteine of the {[PEI/PSS]₂/Au@2Ag/[PEI/P₂Mo₁₇V]₂} composite film, as well asthe detection limit (～4.5×10^-8M), linear range from2.5×10^-7to2.17×10^-4M,response time （<2s） and sensitivity （0.92μA/μM） for detecting dopamine of{PEI/[(P₂W₁₇V-CuO)/（CS-Pd）]7/[P₂W₁₇V-CuO]} composite film were obtainedrespectively. Additionally, the interference of the two composite films was investigated at best potential. The results exhibit there is no interference to detectL-cysteine from the common interfering species such as L-Tryptophan,L（+）-glutamic acid, citric acid, lactic acid and glucose of{[PEI/PSS]₂/Au@2Ag/[PEI/P₂Mo₁₇V]₂} composite film, as well as no interference todetect dopamine from the common interfering species such as ascorbic acid, uric acid,L-cysteine, glucose and H2O2of {PEI/[(P₂W₁₇V-CuO)/（CS-Pd）]7/[P₂W₁₇V-CuO]}composite film.Based on the results of the experiments, the sensing performance to the practicalsamples was investigated. The analysis results indicate the possible use of thesecomposite films as a potential candidate for routine L-cysteine and dopamineanalysis.