What is it about?
Hollow silica particles have attracted tremendous interests in recent years due to their remarkable properties and great potential for widespread applications. However, designing hollow silica materials with varying hollow structures and shapes remains a significant challenge. In this study, 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. 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).
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Why is it important?
In this study, HHSP particles were successfully synthesized via a sol-gel process by utilizing the reaction condition at room temperature. The developed synthetic process has demonstrated potential for large-scale synthesis as a result of the simplicity and effectiveness of the method at mild conditions, which is cost-effective and makes use of commercially available reagents. The organic groups of these silane coupling agents were grafted onto the surface of HHSP particles, which significantly increased the compatibility between particles and polymer matrix. The composite films exhibited high visible and UV light transmittance over than 95%, indicating that highly transparent PMMA/HHSP composite films were fabricated. Furthermore, the HHSP particles having a refractive index as low as 1.28 were obtained, which may result in a new generation of film materials. The versatility of HHSP particles with low refractive index as advanced materials presented in this study can pave a new avenue for potential applications in the fields of optical devices, electronics, and so on.
Perspectives
From the perspectives of synthesis and practical applications of nanostructured materials, exploring geometry optimization of hollow structures is highly desirable for research directions in the future. One of the advantages of HHSP particles is the flexibility of the fabrication approach for the production of composite thin films with high uniformity and dispersion. It should be pointed out that the large empty voids between the particles are a common issue of these simple hollow silica spheres, leading to decrease the material packing density. Constructing hollow structures with an optimal geometry (e.g. HHSP particles) for the purpose of enhancing packing density − which may address the above-mentioned limitation of hollow silica spheres – is desirable for better utilization of the inner hollow cavity. Therefore, it can be expected that the HHSP particles will demonstrate a significant increase in the packing density because of their much smaller empty cavities. On the other hand, until now, many studies have demonstrated the advantages of spherical hollow structures in various fields. However, synthesis of hollow structures with well-defined non-spherical morphologies has not been thoroughly investigated. Additionally, a low refractive index is the most important factor for the future production of thin films in the fields of electronics and optical devices. Thus, with the great achievements and continuous efforts in this field, we assume that the preparation of HHSP particles will contribute to the development of new materials, which renders this approach attractive for diverse applications.
Kiet Le Anh Cao
Hiroshima University
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This page is a summary of: Precisely tailored synthesis of hexagonal hollow silica plate particles and their polymer nanocomposite films with low refractive index, Journal of Colloid and Interface Science, July 2020, Elsevier,
DOI: 10.1016/j.jcis.2020.03.064.
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