| Polyoxometalates (POMs) are exciting metal-oxygen cluster species with a diverse compositional range, enormous structural variety and fascinating adjustable multi-functional properties. The class of POMs has been known for almost 200 years since the first structural details were revealed. Up to now, POM chemistry continues to be a considerable focus in the ongoing research. On one hand, large numbers of the novel structures of POMs and their properties are reported, resulting in their wide potential and realized application areas including catalysis, magnetism, biology, medicine, material science, and chemical analysis, etc. On the other hand, the state in which would create opportunities for the development of new materials for semiconducting devices and separation membranes. However, POMs are typically inorganic materials and generally hard to process, especially they are difficult to be fabricated directly into organized thin films. Therefore, it is very necessary to develop the method to construct an organic-inorganic hybrid layered materials.However, if we use the surfactants to replace the charge-balancing countercations of the POMs to get the surfactant-encapsulated clusters (SECs), which can successfully introduce the POMs into organic phases. In addition, POMs have become promising candidates for the functional ultrathin films on the variety substrate surface by using different techniques such as Langmuir–Blodgett (LB), deposition, sol–gel processing, layer-by-layer (LbL) self-assembly method and so on.Polyoxometalates (POMs) are fascinating metal-oxygen cluster species with a diverse compositional range, enormous structural variety and interesting adjustable multi-functional properties, which have displayed reversible electron-transfer behavior without any significant structural change. Such reversible charge-transfer ability makes POMs promising candidates for homogeneous-phase electron exchange reactions. Based on these considerations, a new room temperature synthesis method for Au NPs was introduced, using partially reduced POMs both as reductants and stabilizers in water at room temperature.solution and the architectures on the solid surfaces for POMs are investigated in detail, First of all, we prepared a series of surfactant-encapsulated POMs including P8W48,Cu20,V12 and Fe16 compounds, DODA-P8W48,DODA-Cu20,DODA-V12 and DODA-Fe16 with different numbers of DODAs, and characterized their structures by 1H-Nuclear magnetic resonance (NMR), Fourier transform infrared (FT-IR), elemental analysis (EA), thermogravimetric analysis (TGA) and X-ray diffraction (XRD). The results indicate that the alkyl chains of DODAs in the hybrid compounds are highly ordered. XRD analysis suggests that two kinds of structures for POMs are present with different width and thickness layer spacings and that most of the DODAs are aligned along the width-axis in the hybrid compound. At the same time, we fabricated the microporous structures based on a series of surfactant-encapsulated polyoxometalate complexes (SECs) by using ordered condensed droplets as a template. We selected four wheel-shaped POMs with similar cluster cores, but different numbers of DODA cations on their surfaces. On the basis of the experimental results, we found only the SEP with an appropriate alkyl chain density could form an ordered honeycomb structures.Second, we introduced Cu20 and its hybrid compound into the LB films. And we used two different strategies to construct LB films in order to compare the differences on the structures between these two films. Thus-prepared LB films were characterized by surface pressure–area (π–A) isotherm measurement, UV–vis spectra, transmission-absorption and polarized FT-IR spectroscopy, XRD, XPS and AFM. The results indicate that Cu20 exhibited two different packing models in the two LB films depending on the deposition strategy used. In the DODA/Cu20 LB film the width-axis of Cu20 is almost vertical to the substrate, while in the case of the DODA-Cu20 LB film two types of Cu20 arrangements were observed: the width-axis orientation of Cu20 is either vertical or parallel to the substrate, but the experimental results suggest that most of the Cu20 are organized in the latter way.At last, we selected a wheel-shaped VV–VIV mixed-valence tungstovanadate of V12, acting as both the reducing agent and the stabilizer to synthesize Au NPs. The neutral Au NPs can absorb a layer of V12 on its surface, making the overall Au NPs negatively charged with a relatively hydrophilic surface. We obtained two different shapes of Au nanoparticles: spherical nanoparticles and multisegmented nanorods by controlling the ratio of two reagents. And when the ratio is equal to 1, we could get a spherical nanoparticles with the size around 30-70 nm, while the ratio is equal to 5 to 10, the multisegmented nanorods could be gotten with the length about 0.2-2μm. Further chara alytic activities for th cterization of these nanoparticles by XPS confirms that Au0 NPs are indeed obtained. Furthermore, this technique also revealed the presence of vanadium and tungsten atoms, indicating that V12 species are deposited on the surface of the nanoparticles. This observation supports the hypothesis that the V12 serves both as a reductant and as a capping layer, in agreement with the propensity, particularly of W-based POMs, to self-assemble on metal and other solid surfaces.In addition, the Au@V12 NPs and V12 can be further fabricated into the ultra-thin films by layer-by layer (LbL) assembly method. And in the UV-vis absorption spectra, there are obvious linear relationships of the absorbances versus the numbers of layers, as well as the redox peak currents of the electrochemical behaviors have good linear relationships with the numbers of layers, which indicate the stable, uniform deposition in each dipping cycle for two films. The LBL assembled Au@V12 electrode shows the same good electrocatalytic activities towards the reduction of O2 and methanol. Compared to this, V12 fabricated electrode does not show any electrocate reduction of O2 and methanol at the same condition.
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