Growth of rutile TiO 2 nanorods on TiO 2 seed layer prepared using facile low cost chemical methods P. Soundarrajan a , K. Sankarasubramanian a , T. Logu a , K. Sethuraman a,n , K. Ramamurthi b a School of Physics, Madurai Kamaraj University, Madurai 625021, Tamil Nadu, India b Department of Physics and Nanotechnology, SRM University, Chennai 603203, Tamil Nadu, India article info Article history: Received 8 October 2013 Accepted 6 November 2013 Available online 12 November 2013 Keywords: Spray pyrolysis TiO 2 thin film Hydrothermal Crystal growth X-ray techniques Raman abstract Dense rutile TiO 2 nanorods were grown on an anatase TiO 2 seed layer by a wet-chemical approach in which the nuclei layer was prepared by the chemical spray pyrolysis technique. Structural, morpholo- gical, and optical properties of prepared samples were investigated using X-ray diffraction (XRD), micro- Raman, scanning electron microscopy (SEM), atomic force microscopy (AFM), UV–vis spectroscopy, and fluorescence spectroscopy. From XRD, a clear authentication that, the preferentially oriented (101) crystallographic planes indicate that the rutile TiO 2 nanorods are standing randomly along the normal to the substrate surface. Anatase TiO 2 seed layer and rutile nanorods structural phases are clearly confirmed by micro-Raman measurement. SEM and AFM studies reveal that the TiO 2 seed layer consists of high density nanoparticles with the thickness of 0.15 μm and the height of the as-grown nanorods is 0.6 μm. The band gap energy of the anatase TiO 2 seed layer and rutile as-grown nanorods is calculated using UV– vis absorption spectra and the band gap values of seed layer and nanorods are 3.21 eV and 2.95 eV respectively. The crystal defects of prepared films are measured using photoluminescence spectra. & 2013 Elsevier B.V. All rights reserved. 1. Introduction Metal oxide semiconductor nanomaterials have received con- siderable attention during past decades owing to their potential applications especially, in the field of solar energy conversion technology. Particularly, TiO 2 nanoparticles have received much attention, after the discovery of photoelectrochemical cell (PEC) water splitting by Fujishima and Honda, and dye sensitized solar cell by O’Regan and Gratzel in the nineties [1,2]. The major drawback of TiO 2 nanoparticles is associated with the recombina- tion process during cell performance. In order to overcome the aforementioned, one dimensional (1D) TiO 2 nanostructures such as nanorods (NRs), nanowires (NWs), and nanotubes (NTs) have been chosen that exhibit excellent ideal electron transport owing to their well-defined crystalline structure, unique optical proper- ties and the quantum confinement effect, which minimizes the charge recombination process and have been considered as an alternative to nanoparticles in the solar cells and electronic devices [3–8]. The dense rutile TiO 2 NRs were grown on TiO 2 seed layer deposited by electron beam evaporation [9]. Dense and aligned TiO 2 nanorod arrays have been fabricated using oblique-angle deposition on ITO substrate by Wolcott et al. [10]. Wang et al. [11] have studied the oriented single crystalline TiO 2 NRs on FTO substrate by hydrothermal synthesis for the application of quan- tum dot sensitized solar cell. Therefore, we believe that seed layer is the key in obtaining the 1D NRs on bare glass substrate. In the present work, two chemical methods such as spray pyrolysis and hydrothermal are used for TiO 2 seed layer and NRs preparation and compared with references [9,10]; chemical methods are of lower cost, the reason behind is the need of no sophisticated instruments for preparations. To the best of our knowledge, the dense TiO 2 NRs on TiO 2 seed layer prepared by chemical spray pyrolysis are not reported elsewhere. 2. Experimental details C 12 H 28 O 4 Ti (TTIP) was purchased from Sigma-Aldrich. Acetic acid was used as a stabilizing agent and HCl as an acidic catalyst to control the hydrolysis rate of titanium. All chemicals used in this work were of analytical grade. The microscope glass slide was used as a substrate. Prior to seed layer coating, the glass substrate was carefully washed with soap solution and kept in hot chromic acid at 70 1C for 30 min and then subsequently cleaned in an ultrasonic bath containing double distilled water and acetone separately. Non-aqueous solution was prepared by TTIP added drop by drop into ethanol solution at room temperature. The resultant solution was stirred for 15 min and then sprayed onto the preheated glass substrates at a temperature of 150 1C. The deposition parameters Contents lists available at ScienceDirect journal homepage: www.elsevier.com/locate/matlet Materials Letters 0167-577X/$- see front matter & 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.matlet.2013.11.026 n Corresponding author. Mobile: þ91 944 525 2309. E-mail address: sethuraman_33@yahoo.com (K. Sethuraman). Materials Letters 116 (2014) 191–194