Evolution from hollow nanospheres to highly ordered FDU-12 induced by inorganic salts under weak acidic conditions

Sulfates have big influence on the structure and morphology of the mesoporous silicas synthesized under weak acidic conditions. The evolution from silica hollow nanospheres to doughnut-like nanoparticles, and to FDU-12 type mesoporous silicas with Fmover(3, -) m symmetry can be induced by CuSO₄ during the condensation of TMOS around Pluronic F127 surfactant in weak acidic solution (pH = 3.25). It is noteworthy that doughnut-like nanoparticles can be obtained in the presence of lower amounts of CuSO₄. Similar to CuSO₄, other divalent sulfates, such as ZnSO₄, NiSO₄, and MgSO₄ can also induce the formation of Fmover(3, -) m mesostructure. However, the presence of K₂SO₄ and Na₂SO₄ specially results in the formation of hollow nanospheres. Plausible mechanisms for the formation of FDU-12 and hollow nanospheres were also proposed.