Copyright © 2018 American Scientiﬁc Publishers All rights reserved Printed in the United States of America Article Journal of Nanoscience and Nanotechnology Vol. 18, 100–103, 2018 www.aspbs.com/jnn Tuning Wall Thicknesses in Mesoporous Silica Films for Optimization of Optical Anti-Reﬂective Properties Nawfel Abdullah 1 , Md. Shahriar A. Hossain 1 , Konstantin Konstantinov 1 , Hirofumi Tanabe 2 , Mikiya Matsuura 2 , Kazuhiko Maekawa 2 , Amanullah Fatehmulla 3 , Wazirzada Aslam Farooq 3 , Md. Tofazzal Islam 4 , Yoshio Bando 5 , Yusuf Valentino Kaneti 5 ∗ , and Yusuke Yamauchi 1 5 ∗ 1 Australian Institute for Innovative Materials (AIIM), University of Wollongong, Squires Way, North Wollongong, NSW 2500, Australia 2 Kuraray Co., Ltd., 41 Miyukigaoka, Tsukuba, Ibaraki 305-0841, Japan 3 Department of Physics and Astronomy, College of Science, King Saudi University, Riyadh 11451, Saudi Arabia 4 Department of Biotechnology, Bangabandhu Sheikh Mujibur Rahman Agricultural University, Gazipur 1706, Bangladesh 5 International Center for Materials Nanoarchitechtonics (MANA), National Institute for Materials Science (NIMS), 1-1 Namiki, Tsukuba, Ibaraki 305-0044, Japan This work reports the fabrication of mesoporous silica ﬁlms with controllable wall thicknesses by spin coating of precursor solutions consisting of polystyrene-block-polybutadiene-block-polystyrene based triblock copolymers (Hydrogenated methyl Styrene Ethylene Butadiene methyl Styrene, HmSEBmS) and tetraethyl orthosilicate (TEOS) followed by calcination in air at 600  C, for optical anti-reﬂection ﬁlms. By changing the relative weight of the triblock polymer to TEOS, the pore-to- pore distance in the mesoporous silica ﬁlm can be controlled without signiﬁcantly affecting the size of the mesopores, thus, enabling effective control of the refractive index and porosity of the ﬁlms. In terms of optical properties, the transmittance of the fabricated mesoporous silica ﬁlm is approx- imately 3.3% higher than that of the uncoated glass substrate in the wavelength range of 400 to 750 nm. Keywords: Mesoporous Materials, Mesoporous Films, Silica, Anti-Reﬂective Films, Optical Properties. 1. INTRODUCTION Controlling the morphology of mesoporous silica materi- als is critical for optimizing their functional applications. Among various morphologies, continuous mesoporous sil- ica ﬁlms are quite useful for optical applications, because of their high transparency. 1 Mesoporous silica ﬁlms are commonly prepared by solvent evaporation methods which enable coating of well-ordered mesoporous layers onto various substrates, such as glass and plastic substrates. 2–4 They have attracted great interests in optical applications due to their low dielectric constant and low refractive index as well as their high porosity and high thermal and mechanical stabilities. 5 6 To date, several types of mesoporous silica ﬁlms with different pore structures have shown excellent low dielectric properties and an ultra-low refractive index. ∗ Authors to whom correspondence should be addressed. An anti-reﬂection (AR) coating is a type of optical coat- ing which is applied to the surface of lenses and other optical devices in order to reduce reﬂectivity. 7–9 In order to enhance the anti-reﬂection properties, an AR ﬁlm having a low refractive index is desired. However, the conventional solvent evaporation method generally requires precise opti- mization of the experimental conditions, such as controls of temperature and humidity, selection of templates, sol- vent compositions etc. Recently, several reports have been published on the use of mesoporous silica nanoparticles for anti-reﬂection ﬁlms, but careful modiﬁcations of the internal and external surfaces of nanoparticles and proper selection of the matrix for the dispersion of nanoparticles is important. 10 To date, anti-reﬂection ﬁlms have been prepared by spray deposition, electrodeposition, chemical vapour depo- sition, physical vapour deposition, and so on. Wet- chemical methods are very convenient for practical 100 J. Nanosci. Nanotechnol. 2018, Vol. 18, No. 1 1533-4880/2018/18/100/004 doi:10.1166/jnn.2018.14558