Synthesis of BaWO4 hollow structures

We have successfully fabricated various BaWO4 hollow structures, including spheres, peanuts, and ellipsoids, by a precipitation reaction between BaCl2 and Na2WO4 solutions in the presence of poly(methacrylic acid) (PMAA). The size and shape of the BaWO4 products could be modified by using different concentrations of Ba2+ ions in the reaction solution. This fabrication method was inspired by the polymer-cation in situ source templates technique. In the growth of these hollow structures, Ba2+ cross-linked with the PMAA to form templates for the in situ nucleation and crystallization of BaWO4 hollow crystals. We also found that the amount of PMAA, pH value of the reaction solution, and duration of processing had significant effects on the morphology of the products. It is possible that this technique can be applied to fabricate many other inorganic hollow structures.