Hydrothermal synthesis of TiO 2 nanofibres Fei-Bao Zhang, Hu-Lin Li ⁎ College of Chemistry and Chemical Engineering, Lanzhou University, Lanzhou 730000, P.R. China Received 29 November 2005; received in revised form 11 January 2006; accepted 5 February 2006 Available online 20 March 2006 Abstract TiO 2 nanofibres were synthesized by the hydrothermal method. The result shows that the growth of TiO 2 nanofibres is sensitive to the concentration of NaOH and the heating temperature. © 2006 Elsevier B.V. All rights reserved. Keywords: Nanofibres; Transmission electron microscopy; X-ray diffraction 1. Introduction Investigation on T iO 2 has been attracting worldwide interest during the past decades [1–3] for its promising application in l ight emission, gas sensors, catalyst and solar cells. Low dimensional nanostructures materials have shown many advantages. Low di- mensional CdSe nanoro ds have been reported to be better in sola r energy conv ersion for their single -crystal structures can supply a directed path for electron transport [4]. A more than 2-fold increase in maximum photoconversion efficiency for water splitting has been observed b y replacing TiO 2 nanocrystalline f ilms with T iO 2 nanowires [5]. Thus designing novel TiO 2 nanostructures, especially well-defined anisotropic and low dimensiona l nanos- tructures, is of significant impor tance f or fundamental r esearch a s well as va rio us relevant applications.Uptonow,differentmethods have been used to sy nthesize the low dimensional TiO 2 .Growthof 1-D TiO 2 nanostructures, including nanowires and nano tubes, has been demonstrated using sol–gel, electrodeposition, and hydro- thermal methods with or without a nodic a luminum o xide (AAO) [6–9].TiO 2 nanorods have also been grown on a WC-Co substrate by metalorganic chemical vapor deposition ( MOCVD) using t ita- nium-tetraisopropoxide (TTIP) as the precursor [10]. In this paper, we report a novel strategy to synthesize TiO 2 nanofibres under hydrothermal conditions in alkaline solution. Compared with the other reporters who use hydrothermal me- thod to synthesize TiO 2 , the reaction temperature we used was higher while the concentration of NaOH was lower. To our knowledge, there are few reports about synthesizing TiO 2 na- nofibres based on the hydrothermal method. This method may open a new door to synthesize novel morphology via changing some conditions. 2. Experimental The titanium dioxide (TiO 2 , anatase) and sodium hydroxide (NaOH) are obtained as analysis pure grade and used without Materials Science and Engineering C 27 (2007) 80– 82 www.elsevier.com/locate/msec ⁎ Corresponding author. Tel.: +86 931 891 2517; fax: +86 931 891 2582. E-mail address: lihl@lzu.edu.cn (H L. Li). 0 1020304050607080 9 0 2 θ /degree (2 1 1) (1 0 5) (2 0 0) (0 0 4) (1 0 0) Fig. 1. XRD patterns for the sample. 0928-4931/$ - see front matter © 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.msec.2006.02.001 further purification and treatment. TiO 2 nanofibres were synthesized in a typical procedure. 0.2 g TiO 2 (anatase) powder was put into a Teflon-lined stainless steel autoclave of 30 ml capacity. The autoclave was filled with 1 M NaOH solutions up to 80% of its capacity, maintained at 160 °C for 24 h, and then cooled to room temperature naturally. A white precipitation was filtered and washed with distilled water and absolute ethanol in sequence. Finally, the products were dried at 50 °C. The structure and morphology of products were characterized by several techniques. Powder X-ray diffraction (XRD) data were collected using a Rigaku D/MAX 2400 dif- fractometer with Cu-Kα radiation (λ = 1.5418 Å). Transmission Fig. 2. TEM images of TiO 2 nanofibres. (A) Scale bar=1 μm; (B) scale bar=167 nm; (C) scale bar=286 nm; (D) scale bar=200 nm; (E) scale bar = 3.3 μm. 81F B. Zhang, H L. Li / Materials Science and Engineering C 27 (2007) 80–82 electron microscopy (TEM; Hitachi 600, Japan) was used to observe the morphology. 3. Results and discussion Fig. 1 shows the X-ray powder diffraction pattern of the product. It is identified as pure TiO 2 (JCPDS card no. 21-1272). The crystalline structure of TiO 2 powders was further cha- racterized by using an X-ray diffractometer as shown in Fig 1. All these diffraction peaks, including not only the peak posi- tions but also their relative intensities, can be perfectly indexed into the crystalline structure of anatase TiO 2 . The result is in accordance with the standard spectrum (JCPDS, card no. 21-1272). The morphologies of the as-prepared products were inves- tigated by transmission electron microscopy (TEM; Hitachi 600, Japan). Fig. 2 shows a TEM micrograph for the product. One can see that the product consists of entangled fibres. Fig. 2 (E) shows a TEM micrograph for “ analytically pure” TiO 2 commercial powder. The particle size is about 10 μm. Compared with Kasuga et al. [7] , who have prepared titanium oxide nanotubes with a diameter of ≈ 8 nm and a length of ≈ 100 nm when sol–gel-derived fine TiO 2 -based powders were treated chemically (e.g., for 20 h at 110 °C) with a 5–10 M NaOH aqueous solution, we have prepared TiO 2 na- nofibres with lower concentration of NaOH and higher tem- perature. The experiment was also carried out with different concentrations of the alkali and at different temperatures. These TiO 2 nanofibres can be formed via the hydrothermal method when the concentration of the alkali is about 1 M and the temperature is not less than 160 °C. If the concentration of the alkali increased and the temperature was about 110 °C, short TiO 2 nanotubes wer e formed. Thus the growth process of TiO 2 nanofibres is controlled by the concentration of the alkali and temperature. Micron-sized TiO 2 is used as the precursor in this work, while in other experiments the nanoscale TiO 2 is used. 4. Conclusion In conclusion, TiO 2 nanofibres are successfully synthesized by using lower concentration of NaOH and higher temperature. Given the generality of this attempt, we hope to extend our synthetic method to prepare other 1-D nanostructure materials. Acknowledgements This work is supported by the National Natural Science Foundation of China (NNSFC No. 60471014). References [1] K.N.P. Kumar, K. Keizer, A.J. Burggraaf, J. Mater. Sci. Lett. 13 (1994) 59. [2] J.J. Wu, C.C. Yu, J. Phys. Chem., B 108 (2004) 3377. [3] J.G. Jia, T. Ohno, M. Matsumura, Chem. Lett. 908 (2000). [4] W.U. Huynh, J.J. Dittmer, A.P. Alivisatos, Science 295 (2002) 2425. [5] S.U.M. Khan, T. Sultana, Sol. Energy Mater. Sol. Cells 76 (2003) 211. [6] B.B. Lakshmi, P.K. Dorhout, C.R. Martin, Chem. Mater. 9 (1997) 857. [7] T. Kasuga, M. Hiramatsu, A. Hoson, T. Sekino, K. Niihara, Langmuir 14 (1998) 3160. [8] X.Y. Zhang, L.D. Zhang, W. Chen, G.W. Meng, M.J. Zheng, L.X. Zhao, Chem. Mater. 13 (2001) 2511. [9] T. Kasuga, M. Hiramatsu, A. Hoson, T. Sekino, K. Niihara, Adv. Mater. 11 (1999) 1307. [10] S.K. Pradhan, P.J. Reucroft, F. Yang, A. Dozier, J. Cryst. Growth 256 (2003) 83. 82 F B. Zhang, H L. Li / Materials Science and Engineering C 27 (2007) 80–82 . 2006 Abstract TiO 2 nanofibres were synthesized by the hydrothermal method. The result shows that the growth of TiO 2 nanofibres is sensitive to the concentration of NaOH. Hydrothermal synthesis of TiO 2 nanofibres Fei-Bao Zhang, Hu-Lin Li ⁎ College of Chemistry and Chemical Engineering,