Photoluminescence of zinc oxide nanopowder synthesized by a combustion method N.L. Tarwal, P.R. Jadhav, S.A. Vanalakar, S.S. Kalagi, R.C. Pawar, J.S. Shaikh, S.S. Mali, D.S. Dalavi, P.S. Shinde, P.S. Patil ⁎ Thin Film Materials Laboratory, Department of Physics, Shivaji University, Kolhapur-416 004, India abstract article info Article history: Received 16 June 2010 Received in revised form 12 December 2010 Accepted 16 December 2010 Available online 24 December 2010 Keywords: Zinc oxide Combustion X-ray diffraction Infrared spectroscopy Photoluminescence Zinc oxide (ZnO) nanopowder was synthesized by a simple and quick combustion method using zinc nitrate as a precursor and glycine as a fuel material. The starting materials were mixed at room temperature and spontaneous ignition of which resulted into the ZnO nanopowder. The synthesized nanopowder was characterized by X-ray diffraction (XRD), scanning electronic microscope (SEM), Infrared (IR) spectropho- tometer and spectroflurometer in order to study the structural, morphological, compositional and photoluminescence (PL) properties. The ZnO powder shows polycrystalline nature with preferential peak (101) having crystallite size 25 nm. A significant band at 532 cm -1 in the IR spectrum corroborates the presence of characteristic band of ZnO. Room temperature photoluminescence spectrum of the synthesized nanopowder exhibits a dominant, sharp and strong ultraviolet (UV) emission with a suppressed deep-level emission indicating good crystal quality and optical properties. © 2010 Elsevier B.V. All rights reserved. 1. Introduction Zinc oxide (ZnO), a wide band gap (3.3 eV) semiconductor with high exciton binding energy (60 meV), has been widely used in myriad applications such as varistors, functional devices, thermoelec- tric materials, UV protection, photocatalysis, field emission displays, superhydrophobic coatings, etc. due to its excellent physical and chemical properties [1–5]. Therefore, it can be applied widely to information technology, bio-technology and environmental technol- ogy as next generation technologies. Nanoscale particles possess different physical and chemical properties. Nanopowders, controlled to nanocrystalline size (less than 100 nm) can show atom-like behaviors which result from higher surface energy. It is due to their large surface area as well as wider band gap between the valence and conduction band when they are divided to near atomic size [6]. There is a need to improve the techniques of synthesis ZnO nanopowder, since the generally used vapor method and sol–gel method [7] are proven to be time consuming and expensive. An alternative to these methods, Park et al. proposed and reported a novel solution combustion method (SCM) [8–11]. They have obtained ZnO nanopowders with 30 nm size, using different oxidant and fuel combinations such as [Zn(OH) 2 ] and glycine, Zn(NO 3 ) 2 ·6H 2 O and glycine dissolved in nitric acid as the starting materials. Vaezi et al. [12] and Shokuhfar et al. [13] prepared single crystals and elongated ZnO nanoparticles having an average particle size of 45 nm by a new solochemical processing from an aqueous solution of a zinc-containing complex. Zhang et al. [14] reported the preparation of amorphous and crystalline ZnO nanopowders via thermal decomposition of the mixture of Zn(CH 3 COO) 2 ·2H 2 O and NaHCO 3 by a solid state reaction. Cai et al. [15] unintentionally obtained ZnO nanopowder with an average particle size of 35 nm by a solvothermal synthesis method in dimethylformamide (DMF) solvent, using zinc chloride, potassium hydroxide and potassium borohydride as starting materials. Riahi- Noori et al. [16] obtained ZnO nanopowder of about 30 nm size by combustion method using zinc nitrate and urea, glycine, citric acid at a neutral pH and a calcination temperature of 500 °C. Mondelaers et al. [17] also obtained ZnO nanoparticulates via an aqueous carboxylate gelation route starting from a solution of zinc acetate with citric acid as a complexing agent. A solid glassy gel is obtained after drying that is converted into fine powder. Nanocrystalline ZnO powder was synthesized by Hwang et al. [18] and the electrical properties of the as-prepared ZnO varistor were reported. The combustion process involves an exothermic reaction between an oxidizer such as metal nitrates and an organic fuel, typically citric acid (C 6 H 8 O 7 ), carbohydrazide (CH 6 N 4 O), urea (CH 4 N 2 O) or glycine (C 2 H 5 NO 2 ) and completed within a few minutes. Generally, a good fuel should react nonviolently, produce nontoxic gases, also it acts as a chelating material for metal cations. The selection of the appropriate fuel is very important for the system under study in the combustion method [16–19]. Among known fuels, glycine has demonstrated the versatility of combustion methods by the successful preparation of a large number of single-phase, well crystallized, multicomponent oxides [20]. Also, it is inexpensive and its combustion heat (-3.24 kcal/g) is more negative compared with urea (-2.98 kcal/g) and citric acid (-2.76 kcal/g). In the reaction, glycine serves two principal purposes: firstly, it serves as fuel for the combustion reaction Powder Technology 208 (2011) 185–188 ⁎ Corresponding author. Tel.: +91 231 2609230; fax: +91 231 2691533. E-mail address: psp_phy@unishivaji.ac.in (P.S. Patil). 0032-5910/$ – see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.powtec.2010.12.017 Contents lists available at ScienceDirect Powder Technology journal homepage: www.elsevier.com/locate/powtec