Unexpected phenomenon in a conventional system: synthesis of raspberry-like hollow periodic mesoporous organosilica with controlled structure in one continuous step

Abstract

Nanoscale complex-shaped colloids with tunable morphologies and fascinating properties have attracted the attention of numerous scientists for decades. Exploring facile synthetic strategies has always been the target for the large-scale production and practical use of these remarkable materials. Herein, we developed a one-step strategy to fabricate raspberry-like hollow periodic mesoporous organosilica (RHPMO) with tunable surface structures and specific surface area as high as 1628 m² g⁻¹. Unexpectedly, this preparation method shares a similar protocol as that of the classical one to make spherical PMO. The dynamic formation process of RHPMO has been detected by TEM. PMOs with solid cores were formed at the first stage, followed by a hollowing process owing to the tension of condensation among the silica precursor molecules. The final RHPMO nanoparticles were generated by controlling the condensation and the adsorption of the as-formed precursor/surfactant assemblies and covalently bonding them subsequently onto the surface of the core. The size of corona particles increased with the concentration of NH₃·H₂O, while low reaction temperatures were beneficial for the formation of RHPMO instead of spherical HPMO (SHPMO). A superhydrophobic coating was realized by depositing fluorine-modified RHPMO layers onto the glass substrate. The measured contact angle reached 153.9°. This one-step strategy for fabricating RHPMO may bring the new understandings of the formation mechanism of PMO and is expected to serve as a facile way for the large-scale production of raspberry-like functional silica spheres, which will thus open gates for more targeted applications.