Controlled synthesis of mesoporous silica nanoparticles with tunable architectures via oil-water microemulsion assembly process

Mesoporous silica nanoparticles (MSNs) have received extensive attention owing to their fascinating properties in recent years. However, the controllable synthesis of MSNs with different morphologies and the transformation of various structures by using simple oil-water microemulsion assembly methods remains a challenge. Herein, a facile microemulsion assembly approach has been developed to fabricate MSNs with various morphologies, tunable particle diameter (135–280 nm), and pore size (2.8–32.8 nm). In the same reaction system, the evolution of walnut-like MSNs to mulberry-like MSNs has been easily achieved. The amount of pentanol not only plays an important role in the evolution of pore sizes but also significantly affects the interfacial interaction between soft templates and silica precursors, which is critical to the morphology of the resulting particles. As a result, wrinkle-like, dendritic-like, walnut-like, and mulberry-like mesoporous nanospheres can be synthesized. More importantly, MSNs with visible voids in the center can be successfully obtained during the synthesis process when the appropriate pentanol is employed. Other experimental parameters, such as the amount of isopropanol, the concentration of surfactant, and the concentration of alkali, were also investigated. A possible mechanism is proposed to account for the formation and growth of MSNs. The Au@NH₂-MSNs composite nanostructures can be used as a catalyst for the reduction of 4-nitrophenol by NaBH₄ into 4-aminophenol and exhibit superior catalytic performance.