A universal biological-materials-assisted hydrothermal route to prepare various inorganic hollow microcapsules in the presence of pollens

A universal bio-economical hydrothermal route has been developed to prepare various inorganic hollow microcapsules with the help of rapeseed pollens for the first time. The pollens were used without any modifications. TiO₂, ZnO, zeolite ZSM-5, BaTiO₃ and ZnS were prepared by this route using the regular synthesis solutions added with rapeseed pollens. The obtained products were examined by scanning and transmission electron microscopy, X-ray diffraction, FT-IR, N₂ adsorption and thermogravimetric analysis. The hollow microcapsules are composed of inorganic particles around the derivations of pollens. And the diameter of the hollow has been demonstrated almost the same size as the derivations microspheres. The derivations were decomposed in high temperature crystallization procedure; therefore, no additional procedure is needed to remove the templates for the hollow structure. The hollow microcapsules prepared with rapeseeds have much higher specific surface area. The formation mechanism can be ascribed to the template effect of derivative microspheres formed from decomposition of these pollen grains. Furthermore, other pollens are also used in the preparation by the universal hydrothermal route. Still, inorganic hollow microcapsules but with different hollow diameters were obtained probably resulting from the different size of the derivations.