Bismuth Tungstate Hollow Sphere and Its Preparation

Hollow spheres refer to a hollow nanomaterials. Because this kind of material has low density, large surface area, good stability and has the characteristics of surface permeability, so both in chemistry, biology and material science applications, porous hollow spheres and hollow spheres formed by stacking have great potential application value in the field of catalysis coating protection slow release, drug packaging, artificial cell simulation and protein, enzyme, DNA and other bioactive molecules as well as coating or paint etc..

Bismuth tungstate hollow spheres have a good orthogonality structure composed of a molecular layer of bismuth ion and oxygen ion and an octahedral layer of WO₆^6-, that is, sandwiching the WO₆^6- octahedral layer between the two atomic layers. This fine microstructure makes bismuth tungstate in the electrical insulation, ionic conductivity, light and photocatalytic fields are promising.

Some scholars have provided a quick and easy preparation of bismuth tungstate (Bi₂WO₆) hollow ball preparation method:

The saturated sodium tungstate water solution and the saturated bismuth nitrate solution are respectively arranged. In the condition of constant stirring, 15mL saturated bismuth nitrate solution is added to 120mL anhydrous ethanol to form a suspension. Then the two are mixed, slowly stirring for 30 minutes, and then heated to 100 centigrade in the sealing reactor and 12 hours for heat preservation. The solid phase material produced by the reaction is collected, and the white powder products are obtained after separation and washing. The product was identified as bismuth tungstate by X ray diffraction. The structure of hollow sphere was analyzed by transmission electron microscope. The particle size was about 50nm and the wall thickness was about 10nm.

The bismuth tungstate hollow sphere prepared by the above method does not need to add other substances than the reactant as a template, the solid particles precipitated directly from the water soluble bismuth salt (bismuth nitrate and bismuth chloride, etc.) in polar organic solvents (ethanol, acetone, etc.) are used as templates. The template was converted into a target product of bismuth tungstate hollow sphere in the subsequent interface reaction. This method is widely used, mild conditions, simple process and easy to be produced in industrial production. 

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