A general approach for synthesis of functional metal oxide nanotubes and their application in dye- sensitized solar cells† Parthiban Ramasamy, Da-Hye Lim, Jungsu Kim and Jinkwon Kim * TiO 2 , SnO 2 , ZnO, Fe 2 O 3 , and ZrO 2 nanotubes were synthesized through a combination of templating and solvothermal processes. Selenium nanowires have been used as a template for the first time to synthesis a family of functional metal oxide nanotubes. The nanotubes so obtained were composed of fine particles with sizes as small as 6–8 nm. These nanotubes were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), transmission electron microscopy (TEM) and Raman spectra. The influence of TiO 2 nanotubes on the performance of dye-sensitized solar cells (DSSCs) based on the TiO 2 nanotube/nanoparticle composite films was investigated. The power conversion efficiency of DSSC was enhanced from 5.84% for the pure nanoparticle film to 6.66% for the composite film with 10 wt% nanotubes. Advantages of this method include that it is a simple and general process that can open new avenues for the synthesis of a variety of functional nanotube structures. 1. Introduction In the past two decades, the study of metal-oxides has gradually become one of the hottest topics in the eld of materials science. The unique properties of metal-oxides such as wide bandgaps, 1,2 high dielectric constants, 3,4 good electrical, 5 and optical 6 characteristics are anticipated for the development of multifunctional materials to use in various applications. One- dimensional (1D) nanostructures such as nanotubes, nano- wires, nanorods, and nanobelts have attracted special attention because of their size and dimensionality dependent electrical, optical and mechanical properties and also they are expected to play an important role as building blocks for the future nano- scale electronic and optical devices. 7 Compared with solid nanowires, metal oxide tubular nanostructures have attracted signicant research interest because of their large specic surface areas, very narrow inner pores, and enhanced surface catalytic properties. Furthermore, 1D nanotubes have showed improved performance in gas sensors, 8,9 eld-emission, 10 photovoltaics, 11,12 and lithium rechargeable batteries. 13 Among various metal oxides, TiO 2 , SnO 2 , and ZnO are common wide band gap semiconductors and have been found to be widely used in many elds. TiO 2 (E g z 3 eV) is one of the most extensively studied oxide material and has been widely used in photovoltaics, and photocatalysis. 14 As a n-type direct wide-band gap semiconductor SnO 2 (E g z 3.6 eV), has attracted the most scientic attention because of its excellent properties, which make it suitable for use in gas sensing and as anode materials in lithium rechargeable batteries. 8,15 Because of its unique optical and electrical properties ZnO have potential application in UV lasers, light-emitting diodes (LED), eld-effect transistors, and solar cells. 16 Fe 2 O 3 is widely used in gas sensors, lithium ion batteries, catalysis, and magnetic storage. 17 ZrO 2 is an important material and widely used in ceramics, fuel cells, thermal barrier coatings, and refractory materials. 18 Up to now, a number of synthesis strategies for 1D nano- tubes have been reported, such as template-directed process, hydrothermal/solvothermal process, sol–gel techniques, elec- trochemical synthesis, and atomic layer deposition (ALD) into the template. 19–23 Among them, the template-assisted approach has been demonstrated to be a powerful method for the construction of 1D nanotubes. The templating method has many advantages over templateless methods, such as simple fabrication, various compositions of materials, and control over the sizes of the formed nanotubes. Many different templates such as, carbon nanotubes, 24 carbon nanobres, 25 anodic aluminum oxide (AAO) membranes, 26 ZnO arrays, 27 1D silica mesostructures, 28 and microporous organic nanotubes were used to fabricate 1D metal oxide nanotubes. 13 Since different metal salt sources have different reactivities towards one particular template, it is difficult to extend any reaction process obtained from previous experiments to others. There are very few reports on the synthesis of various metal oxide nanotubes Department of Chemistry and GETRC, Kongju National University, 182, Shinkwondong, Kongju, 314-701, Chungnam-do, Republic of Korea. E-mail: jkim@ kongju.ac.kr; Fax: +82-41-850-8613; Tel: +82-41-850-8496 † Electronic supplementary information (ESI) available: FT-IR spectra of functionalized Se NWs, EDS and Raman spectra of TiO 2 nanotubes, BET surface area measurements, XRD pattern and Raman spectra of SnO 2 nanotubes, XRD pattern of ZnO, Fe 2 O 3 and ZrO 2 nanotubes. See DOI: 10.1039/c3ra45506h Cite this: RSC Adv. , 2014, 4, 2858 Received 1st October 2013 Accepted 7th November 2013 DOI: 10.1039/c3ra45506h www.rsc.org/advances 2858 | RSC Adv. , 2014, 4, 2858–2864 This journal is © The Royal Society of Chemistry 2014 RSC Advances PAPER Published on 07 November 2013. Downloaded by Daegu Gyeongbuk Institute of Science and Technolog on 04/06/2015 12:38:58. View Article Online View Journal | View Issue