Short communication Effect of concentration and heating conditions on microwave-assisted hydrothermal synthesis of ZnO nanorods Nadi Shojaee, Touradj Ebadzadeh ⁎ , Alireza Aghaei Ceramic Division, Materials and Energy Research Center, P.O. Box 14155-4777, Tehran, Iran ARTICLE DATA Article history: Received 10 November 2009 Received in revised form 18 August 2010 Accepted 18 August 2010 Keywords: Crystal growth Nanomaterials Microwave heating Hydrothermal Zinc oxide 1. Introduction Zinc oxide (ZnO) is a unique material that exhibits semicon- ducting, piezoelectric, and pyroelectric properties [1]. ZnO has been extensively used in technical ceramics as it is: (1) a semiconductor material due to its wide band gap (3.37 eV) which is suitable for short wave length optoelectronic applications, (2) a laser material due to its high exciton binding energy, (3) a piezoelectric material due to its unsym- metrical structure which is a key factor in manufacturing electromechanical coupling sensors and (4) a biomaterial due to its biocompatibility [2]. ZnO is also an optimal material for applications in sensors, solar cells, UV detectors, acoustic devices and UV light emitting devices. Recently, one-dimen- sional (1D) materials have become a leading edge in nanoscience and nanotechnology. These materials have novel electrical, mechanical, chemical and optical properties MATERIALS CHARACTERIZATION 61 (2010) 1418 – 1423 ⁎ Corresponding author. Tel.: +98 261 6204131 6; fax: +98 21 88773352. E-mail addresses: n_shojaee@merc.ac.ir (N. Shojaee), t-ebadzadeh@merc.ac.ir (T. Ebadzadeh), a-aghaei@merc.ac.ir (A. Aghaei). as a result of increased surface and quantum confinement effect [3]. The most common methods for synthesizing ZnO nano- crystals are thermal evaporation, chemical vapor deposition and metal organic vapor phase epitaxy [4–6]. The general feasibility of these methods depends on some essential requirements such as using catalysts, applying high tempera- tures and vacuum. These requirements increase the process cost and limit the choice of substrates. Vayssieres [7] developed a new hydrothermal method to grow one-dimen- sional ZnO nanostructures at a low-temperature using simple precursors. This method was too slow to be introduced as a commercial route. Recently, the novel synthesis of nanos- tructure materials via microwave irradiation has been intro- duced. In comparison with the conventional heating, microwave heating has unique effects such as rapid and homogeneous volumetric heating, high reaction rate, short reaction time, enhanced reaction selectivity, energy savings and lower cost [8]. The present work reports the synthesis of ZnO nanorods via a rapid one-step chemical method using microwave irradiation. ZnO nanorods were vertically grown on different substrates through a simple aqueous solution without any pretreatment. 2. Experimental Procedures In this process, zinc nitrate hexahydrate (Zn (NO 3 ) 2 .6H 2 O) and Methenamine (Hexa methylenetetramine; HMT: (CH 2 ) 6 N 4 ) were used as zinc and OH - sources. Both raw materials were analytical reagents, obtained from MERK Chemical Co. Ltd. and used without further purification. The chemical reactions were carried out by heating the precursors in a microwave oven (Panasonic NN-C2003S, frequency 2.45 GHz, maximum 1044-5803/$ – see front matter © 2010 Elsevier Inc. All rights reserved. doi:10.1016/j.matchar.2010.08.006 available at www.sciencedirect.com www.elsevier.com/locate/matchar