Mesoporous Silica Nanoparticles with Dispersibility in Organic Solvents and Their Versatile Surface Modification

Recently, colloidal mesoporous silica nanoparticles (MSNs) have attracted keen interest in scientific and technological fields. A significant issue regarding the effective use of colloidal MSNs is their dispersibility in various solvents, which is essential for their applications through surface modification. However, the dispersion media for colloidal MSNs have been extremely limited. Here, we report a new method for obtaining stable colloidal MSNs dispersed in various organic solvents through a gradual solvent exchange of colloidal MSNs from acidic water to an organic solvent by dialysis. This allows the colloidal MSNs to be dispersed as primary nanoparticles in organic solvents such as 1-butanol, 1-dodecanol, and tetrahydrofuran (THF), which are capable of hydrogen bonding with surface silanol groups. In addition, MSNs dispersed in THF can be modified with chlorosilanes while maintaining colloidal stability. Various organosilyl groups, such as trimethylsilyl and dimethylsilyl groups, can be densely grafted on the surfaces of MSNs. After trimethylsilylation, MSNs become dispersible even in a nonpolar and hydrophobic solvent like octane through the solvent exchange due to the preferential evaporation of THF. This method will offer a versatile approach to functionalizing colloidal MSNs toward a wide range of applications.