Rapid microwave-assisted hydrothermal synthesis of Bi 12 TiO 20 hierarchical architecture with enhanced visible-light photocatalytic activities Zhuo Yang, Huiqing Fan n , Xin Wang, Changbai Long State Key Laboratory of Solidification Processing, School of Materials Science and Engineering, Northwestern Polytechnical University, Xi'an 710072, China article info Article history: Received 2 December 2012 Received in revised form 25 June 2013 Accepted 28 June 2013 Available online 6 July 2013 Keywords: A. Nanostructures A. Oxides B. Chemical synthesis D. Optical properties abstract Flower-like Bi 12 TiO 20 hierarchical nanostructures composed of numerous nanobelts were synthesized at 180 1C within 1 h by a microwave-assisted hydrothermal method in the presence of cetyltrimethylam- monium bromide (CTAB) for the first time. The as-prepared products were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and ultraviolet–visible (UV–vis) absorption spectroscopy. Furthermore, the hierarchical Bi 12 TiO 20 nanostruc- tures exhibited higher photocatalytic activities in the degradation of Rhodamine B under visible-light irradiation than that of the samples prepared without CTAB. In addition, the role of CTAB cationic surfactant has been investigated thoroughly and a possible mechanism is proposed. & 2013 Elsevier Ltd. All rights reserved. 1. Introduction Since the nanostructured materials with good control on their morphologies, size, and crystallographic structure may differ significantly from the corresponding bulk counterparts, nanos- tructured semiconductors have attracted a growing interest for their fascinating properties and potential applications in technology [1,2]. Recently, ternary bismuth oxide semiconductors, such as Bi 2 WO 6 , BiVO 4 , Bi 2 Ti 2 O 7 and Bi 12 TiO 20 have been widely studied as a class of promising photocatalysts with catalytic activity under visible-light irradiation [3–12]. Among them, Bi 12 TiO 20 crystals with sillenite structures is one of the most frequently investigated materials due to its excellent intrinsic properties and the potential applications including optical information processing, optical phase conjugation, photovoltaic cells and photocatalysts [13–16]. Bi 12 TiO 20 micro/nanostructures with different morphologies and sizes have been obtained via solid-state reactions, chemical method, or by conventional hydrothermal synthesis [17]. Those methods mentioned above, however, have obvious disadvantages like the requirement for high-temperature calcination, which often results in large-sized crystallization and hard aggregation, or requiring com- plicated equipments and long processing time [18]. Microwave irradiation could be used as a heat source for the hydrothermal process. It leads to a rapid heating to attain the desired temperature in a short time and increases the reaction kinetics, compared to the conventional hydrothermal method. Microwave-assisted reaction is seldom employed to synthesize Bi 12 TiO 20 crystals for photocatalysis although such a method has been used successfully to fabricate various materials [19]. Further, tailoring the architecture of nanoma- terials has been of great research interest due to their unique properties are closely related to the size and shape of nanostructures. In terms of morphology control, cetyltrimethylammonium bromide (CTAB) has been generally used to synthesize different nanostruc- tures, such as nanowires, nanotubes, hollow spheres, and 3D hierarchical structures [20,21]. Phuruangrat and co-workers described the synthesis of MoO 3 nanowire with unprecedentedly high aspect ratios in the presence of CTAB [22]. Hu et al. synthesized CuO nanotubes and nanorods using CTAB by a hydrothermal process [23]. Multilayered ZnO nanosheets with hierarchically porous struc- tures are successfully synthesized from a hydrothermal preparation and thermal decomposition by using CTAB [24]. However, relatively few studies on the synthesis of hierarchically Bi 12 TiO 20 nanostruc- tures using CTAB have been reported up to now. Herein, a microwave-assisted hydrothermal route was used to synthesize hierarchical nanostructured Bi 12 TiO 20 powders in the presence of cetyltrimethylammonium bromide (CTAB) for the first time. The key features of this method are that it is time-saving, has low energy consumption, and is inexpensive. Moreover, the photodegradation of Rhodamine B (RhB) was employed to evalu- ate the photocatalytic activities of Bi 12 TiO 20 hierarchical nanos- tructures under visible-light irradiation. It is worthy to note that the hierarchical Bi 12 TiO 20 materials exhibit enhanced visible-light- driven photocatalytic performance. Contents lists available at ScienceDirect journal homepage: www.elsevier.com/locate/jpcs Journal of Physics and Chemistry of Solids 0022-3697/$ - see front matter & 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.jpcs.2013.06.020 n Corresponding author. Tel.: +86 29 88494463; fax: +86 29 88492642. E-mail address: hqfan3@163.com (H. Fan). Journal of Physics and Chemistry of Solids 74 (2013) 1739–1744