Fabrication And Sensing Properties Of Vanadium-substituted Polyoxometalates Composite Films

In this paper, the two composite films based on two vanadium-substitutedpolyoxometalates decorated by grapheme, Au nanoparticles or tris(2,2-bipyridine)ruthenium(II)[Ru(bpy)3] were prepared by the layer-by-layer self-assembly methodon the ITO, quartz and silicon.In this paper, the growth process of the composite films was monitored byUV-vis spectroscopy. The result shows that an uniform and stabilizing growthprocess of the two composite films. The surface morphology and roughness wereexamined by using atomic force microscopy (AFM) and scanning electronmicroscope (SEM). The result shows that the nanoparticles were uniformly dispersedon the fold shaped surface of composite films. X-ray photoelectron spectra (XPS)were used to identify the chemical composition of the composite films. The resultshows that nanoparticles, graphene and polyoxometalates were successfullydeposited on the film. Amperometric and cyclic voltammograms (CV) detection wereused to investigate the electrochemical properties and sense for uric acid (UA) andascorbic acid (AA) of the composite films. Electrochemistry experiments revealedthat in the phosphate buffer solution (pH=7.0), the {PEI/[P2W16V2-Au/PDDA-rGO]8/P2W16V2} composite film exhibits a high electrochemical activitytoward sensing of UA at0.43V. The current response of the sensor exhibited thelinear correlation to UA concentration in the range from2.5×10-7to1.025×10-4M,the detection limit1.4×10-7M with sensitivity0.24μM/μA. At the same time thecomposite film exhibits good repeatability and stability properties. The resultsexhibit that the sensor was capable of detecting UA with a good average recovery of100.4%in urine samples. There is no interference to detect UA from the commoninterfering species under catalytic potential. Electrochemistry experiments show that the sensing properties of the composite films{PEI/[PMo9V3/Ru(bpy)3/PSS/PDDA-rGO]5/PMo9V3} to AA were good in thephosphate buffer solution (pH=6.5) at0.15V. The linear analysis shows that thelinear range from7.5×10-7to2.07×10-4M, the detection limit1.0×10-7M andsensitivity0.24μM/μA. And the sensor of AA shows good selectivity with commoninterfering species. The composite film was used for ascorbic acid determinations inreal samples with satisfactory results.