Superior photocatalytic performance of reduced graphene oxide wrapped electrospun anatase mesoporous TiO 2 nanofibers Thirugnanam Lavanya a,b , Kaveri Satheesh c , Mrinal Dutta a,⇑ , N. Victor Jaya b , Naoki Fukata a,⇑ a International Center for Materials Nanoarchitectonics (MANA), National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan b Department of Physics, Anna University, Chennai 600025, India c Centre for Nanoscience and Technology, Anna University, Chennai 600025, India article info Article history: Received 21 January 2014 Received in revised form 6 May 2014 Accepted 7 May 2014 Available online 2 June 2014 Keywords: Nanofiber Mesoporous TiO 2 Wrapping Composite Photocatalysis abstract Reduced graphene oxide (rGO) wrapped with anatase mesoporous TiO 2 nanofibers (TNFs) were synthe- sized, by using the electrospinning technique along with easy chemical methods. The structural and mor- phological results demonstrate the success of wrapping of nanofibers with rGO. Wrapping with rGO leads to an efficient photogenerated charge carrier separation across the interface of rGO and TNFs. As a result, the photocatalytic activity of the composites is enhanced to 96% compared to only 43% for TNFs alone, in the photo degradation of methyl orange. This simple synthetic method can be applied not only to wrap rGO over other nanostructures of different morphology, but also for enhancing the properties of multi- functional materials. Ó 2014 Published by Elsevier B.V. 1. Introduction Semiconductor photocatalysis of organic compounds in water and air is a promising technology for solving worldwide environ- mental pollution. Among various semiconductor photocatalysts, titanium dioxide (TiO 2 ) has been considered as the most suitable material for widespread environmental applications because of its strong photocatalytic performance, easy availability, long-term stability, and nontoxicity [1–3]. Compare to conventional nano- powders and thin film photocatalysts, TiO 2 nanofibers (NFs) show higher surface active sites for adsorption and catalysis of reactants due to greater surface to volume ratio [4,5]. However, the photo- catalytic activity of TiO 2 is limited by absorbing only in the UV region of the solar spectrum due to its wide bandgap. In addition to this, the recombination time of the electron–hole pairs is very short (10 9 s) compared to the chemical interaction time (10 3 to 10 8 s) on the surface of TiO 2 with the adsorbed dyes or other molecules [6–8]. These limitations have been often over- come by doping with and without metal ions, loading of noble metals, or making composites of TiO 2 with other metal oxides [9,10]. However, the materials synthesized by the above methods show low stability against photo corrosion, and in some cases, suf- fer from low concentration of doped ions. Furthermore, in the case of composites with other metal oxides the partial loss of active sur- face sites often occurred, resulting in a decrease in the photocata- lytic efficiency [11]. Nevertheless, the introduction of carbon materials, including activated carbon, carbon nanotubes, and ful- lerenes can effectively enhance the charge separation rate of TiO 2- AC composites [12,13]. Among the carbon family, Graphene, a two-dimensional honeycomb lattice of carbon atoms, due to its unique properties such as excellent carrier mobility (20,000 cm 2 - v 1 s 1 ), high transmittance, large surface area (2600 m 2 g 1 ), and chemical stability, has become a rising star for future nanode- vice applications [14–16]. Thus, graphene could be an ideal mechanical support and electric charge carrier transporter to con- struct nanocomposites with enhanced performances [16,17]. Among the graphene-based composites, TiO 2 -graphene composites (TGCs) have been widely studied for various applications with enhanced performances in photocatalysis, solar cells, and lith- ium-ion batteries [18–21]. However, TGCs showed the cytotoxic effect on minuscule animals under solar irradiation, which limits the extensive use of these highly efficient composite photocata- lysts as reported by Akhavan et al. [22]. Among the different meth- ods, such as hydrothermal, solvothermal, heterogeneous coagulation and electrospinning, so far used for the synthesis of TiO 2 -graphene composites, electrospinning is a simple and cost- effective technique for fabricating nanofibers in a core/shell, ran- dom and aligned, and hollow configurations [23–26]. In spite of http://dx.doi.org/10.1016/j.jallcom.2014.05.088 0925-8388/Ó 2014 Published by Elsevier B.V. ⇑ Corresponding authors. Tel.: +81 8032959665 (M. Dutta). E-mail addresses: DUTTA.Mrinal@nims.go.jp (M. Dutta), FUKATA.Naoki@nims. go.jp (N. Fukata). Journal of Alloys and Compounds 615 (2014) 643–650 Contents lists available at ScienceDirect Journal of Alloys and Compounds journal homepage: www.elsevier.com/locate/jalcom