Immobilization Of The Rare Earth-containing Polyoxometalate EuW₁₀ And Its Property Research

Polyoxometalates (POMs) represents a large family of discrete inorganic materials derived from the early transition metals of V, Mo, W, and Nb etc, and they have shown great potential in catalysis, magnetism, nanoscale devices on surfaces and molecular electronics etc. In particular, rare earth containing polyoxometalates have become a hot topic in POM research, due to they have superior versatility from rare earth cation and POM anion. Na9EuW10O36·32H20(donated as EuW10) as a member of rare earth containing polyoxometalates has attracted substantial interest, owing to its excellent luminescent and catalytic property. In terms of catalytic EuW10has advantages of good stability and high selectivity, as luminescent materials, EuW10has virtues of high luminescent efficiency, excellent monochromaticity and long-wavelength emissions. Nevertheless, it should be noted that practical applications of POMs are in general largely restricted by formation of aggregates since their high crystalline energy of pure POMs as inorganic crystalline and/or powered materials. Aggregates of EuW10powder would lead to some inevitable defects of its property, such as diminution of catalytic efficiency, cumbersome procedure for recycling of catalyst and flurescence quenching, short lifetime in the aspects of catalytic and luminescence, respectively. As a result, how to solve the above problems is particularly important for the development of POMs-containing multi-functional materials.This paper is amid at solving the problems of practical applications of EuW10as functional materials by using simple and general methods of immobilization. The research content includes two aspects as follows:1. In order to solve the cumbersome procedure for recycling of EuW10powder used as catalyst, directional self-assembly of the exfoliated layered europium hydroxide nanosheets (denoted as LEuH) and EuW10has been established by electrostatic self-assembly technology, leading to the formation of a new inorganic-inorganic hybrid material of LEuH-EuW10. This hybrid material used as the heterogeneous catalyst not only showed high catalytic efficiency of extractive oxidative desulfurization but aslo easily recycled by simple centrifugation.2. In order to avoid the phenomenon of flurescence quenching and poor stability in EuW10powder used as luminescent material, the continuous, flexible and self-supporting nanocomposite films of EuW10/PAN (EuW10=Na9[EuW10O36]·32H2O; PAN=polyacrylonitrile) have been successfully fabricated through electrospinning technique. The resulting films display strong red emission of Eu(Ⅲ) ion and exhibit reversible pH-modulated luminescent photoswitching.