Non-Surfactant Self-Templating Strategy for Mesoporous Silica Nanospheres: beyond Stöber Method
The well-known Stöber method has been widely used to synthesize nonporous silica nanospheres (NPs), however in the absence of surfactant templates, the synthesis mesoporous silica nanospheres (MSNs) has not been achieved. Herein, in the absence of organic surfactant template, by a simple premixing of three components tetraethoxysilane-water-ethanol (TEOS-H2O-EtOH) with precise molar ratio, the parent silica nanoparticles with low condensation degree and controlled particle size can be readily obtained. Subsequently, via a simple two-step post-treatment, the obtained MSNs exhibited high surface area (ca. 500 m2/g), accessible mesopores (3.0 nm), and large pore volume (0.87 mL/g ), similar to that of MCM-41 and SBA-15 silicas. The unique self-templating role of ‘pre-Ouzo’ effect of ternary surfactant-free TEOS-H2O-EtOH systems was proposed to understand the formation of mesoporosity.