Contents lists available at ScienceDirect Ceramics International journal homepage: www.elsevier.com/locate/ceramint Role of block copolymer template for tailoring crystal structure and band gap of titania in mesoporous silica and organosilica particles Gopalu Karunakaran, Eun-Bum Cho * Biosensor Research Institute, Department of Fine Chemistry, Seoul National University of Science and Technology, Seoul, 01811, Republic of Korea ARTICLE INFO Keywords: Sol–gel processes Electron microscopy SiO 2 TiO 2 Functional applications ABSTRACT This work presents the tailoring of distinct titania (titania oxide) (TiO 2 ) crystal structures inside the mesoporous silica and organosilica using several different block copolymer templates in acidic aqueous solution with dif- ferent acidity. Different crystal structures of TiO 2 have been obtained as rutile and anatase phases, mainly depending on the chemical composition of block copolymer templates used in this study. A PEO-PLGA-PEO (EO 17 (L 28 G 7 )EO 17 , LGE54) triblock copolymer, as well as typical Pluronic P123 (EO 20 PO 70 EO 20 ) and F127 (EO 106 PO 70 EO 106 ) triblock copolymers was employed as structure-directing templates for the sol-gel reaction of silane precursors. As silica and organosilica precursors, tetraethyl orthosilicate (TEOS), 1,2-bis(triethoxysilyl) ethane (BTEE), and 1,4-bis(triethoxysilyl)benzene (BTEB) were utilized with a titanium butoxide precursor. The crystal structure of TiO 2 and its corresponding band gap were investigated using X-ray diffraction (XRD) and ultraviolet–visible spectroscopy (UV–vis) measurements, respectively. Anatase crystalline phase of TiO 2 was found in the mesoporous sample prepared with Pluronic copolymer (i.e. P123 and F127) templates. On the other hand, the rutile phase was developed only in mesoporous samples prepared with an LGE54 PEO-PLGA-PEO triblock copolymer template. It was found the TiO 2 crystal structure is varied mainly depending on the polymer template under various strong acidic conditions. It seems that a thermodynamically more stable rutile phase can be formed using a more hydrophobic LGE54 template which supplies stronger micelle core as a platform. Further, it is known that the incorporation of TiO 2 in mesoporous silica and organosilica samples induces the conduction activity, especially toward the blue light region. Thus, this work can be applied to produce effective blue region semiconductor material with different crystallite structures by tuning the precursors and copolymer templates. 1. Introduction Titania (TiO 2 ) is one of the most useful semiconducting materials which has a high band gap due to which it has been also used in dif- ferent applications such as photocatalysts, solar cell, hydrogen pro- duction and a redox catalyst [1–4]. Titania is known to be non-toxic to humans as well as to the environment [5]. Hence, due to this, it is a safe and widely used material for diverse applications. Recently, it has been reported that variation in the crystal structure, size, and shapes of TiO 2 can give a great influence on its functions and applications [6–8]. For example, rutile phase TiO 2 is used in applications like solar cells, Na-ion batteries, lithium-ion batteries, and cosmetic UV-blocking applications [9–12]. Anatase phase TiO 2 is also used in different applications like Na-ion Batteries, Friedel–Crafts alkylation, water cleaning, solar cells and photocatalysts [13–16]. Due to the versatile applications of TiO 2 , future research is focused on the synthesis of different morphology and crystalline phases of TiO 2 for several applications. Various works have reported the rutile phase TiO 2 can be prepared using typical chemical reactions including the sol- gel method [17], polyol process [18], and air-liquid foaming sol-gel method [19]. Also, the anatase phase TiO 2 can be obtained using the hydrothermal method for dye-sensitized solar cells [20]. Porous TiO 2 nanotubes with the anatase phase were reported using the electro- deposition method [21]. Even though different methods produce dif- ferent phases of pure TiO 2 , still TiO 2 has some drawbacks such as its instability at high temperature, morphological features, a smaller amount of pair electrons, and low surface area. These drawbacks limit its versatile usage in many industrial applications. Hence, recent works have been focused to improve the performance of TiO 2 for its efficient usage in different fields. For example, it was reported that the in- corporation of TiO 2 in any material and its composite materials mixed with different dopants enhances its activity of photocatalytic https://doi.org/10.1016/j.ceramint.2019.09.200 Received 3 September 2019; Received in revised form 11 September 2019; Accepted 20 September 2019 * Corresponding author. E-mail address: echo@seoultech.ac.kr (E.-B. Cho). Ceramics International xxx (xxxx) xxx–xxx 0272-8842/ © 2019 Elsevier Ltd and Techna Group S.r.l. All rights reserved. Please cite this article as: Gopalu Karunakaran and Eun-Bum Cho, Ceramics International, https://doi.org/10.1016/j.ceramint.2019.09.200