Precisely tailored synthesis of hexagonal hollow silica plate particles and their polymer nanocomposite films with low refractive index

Hollow silica particles are desirable for numerous applications, however, designing hollow silica materials with varying hollow structures and shapes remains a significant challenge. Herein, a strategy for the precisely controlled synthesis of hexagonal-shaped hollow silica plate (HHSP) particles was successfully prepared via a sol-gel method at room temperature, using tetraethyl orthosilicate (TEOS) as a silica precursor and zinc oxide (ZnO) particles as a colloidal template. The effect of reaction time was carried out to control the structure and morphology of HHSP particles, and the thickness of silica shell can be tuned in the range from 12.2 to 43.2 nm by adjusting the TEOS/ZnO molar ratios. In addition, the polymer/HHSP composite thin films were prepared using poly(methyl methacrylate) (PMMA) matrix and surface modified HHSP particles by grafting silane coupling agents. High transmittance values were observed (>95%) for the composite thin films (5 μm in thickness, 0.1–1.0 wt% HHSP) in the ultraviolet and visible regions. Furthermore, the refractive index of HHSP particles was observed to be 1.28, which is significantly lower than dense silica (n = 1.46). These results suggest that the approach adopted herein will open up opportunities for the development of a new generation of film materials with a low refractive index.