Growth and local structure analysis of ZnS nanoparticles R. Saravanan n , S. Saravanakumar, S. Lavanya PG Department and Research Centre of Physics, The Madura College, Madurai 625 011, India article info Article history: Received 28 April 2010 Received in revised form 19 May 2010 Accepted 21 May 2010 Keywords: Nano ZnS MEM Rietveld Powder Electron density abstract The ZnS nanoparticles synthesized using sol–gel method are characterized using XRD and SEM. The powder XRD analysis is done using the Rietveld method. The bonding feature of ZnS nanoparticles is analyzed using the maximum entropy method. The bonding between Zn and S is clearly visible in the 3D and 2D MEM maps. The electron density at the middle of the bond between Zn and S atom is found to be 0.433 e/ ˚ A 3 . The particle size of ZnS nanoparticles is also analyzed. There is a close comparison between the particle size estimated using XRD and SEM. & 2010 Elsevier B.V. All rights reserved. 1. Introduction In the recent decades, semiconductor nanocrystals have been extensively studied and reports are available for the preparation methods, physical and chemical properties of nano crystals because of their potential application. ZnS is an important material due to its variety of applications. The theoretical band gap for this II–VI compound semiconductor is 3.6 eV [1]. It is commercially used as phosphor and thin-film electroluminescence devices [2,3]. Impurity activated ZnS nano material differs from that of bulk ZnS material. Photo physical and photochemical properties of ZnS semiconductor nanocrystals doped with Mn 2+ , Cu 2+ and Ag 2+ have been researched recently [4–9]. The action of dopant atoms on the base material is very complex. Yang et al. [1] has studied luminescence properties of Al 3+ , In 3+ and Ga 3+ doped ZnS nanocrystallites. Photoacoustic (PA) characteristics of Mn-doped ZnS nanoparticles were also reported by Almira Briones Cruz et al. [10]. The nanosized semiconductor crystallites could change the optical properties which are different from bulk materials. As the size is reduced to approach the exciton Bohr radius, there are some drastic changes in the electronic structure and physical properties. Wu et al. [11] have observed that the nano material has higher hardness than its bulk materials. Zinc sulfide is a wide gap and direct transition semiconductor [12]. Consequently, it is a potentially important material to be used as an antireflection coating for heterojunction solar cells [13]. It is an important device material for the detection, emission and modulation of visible and near ultra violet light [14,15]. In particular, ZnS is believed to be one of the most promising materials for blue light emitting laser diodes [16] and thin-film electroluminescent displays [17]. ZnS nano particles have the potential for applications in areas such as nonlinear optical devices and fast optical switches and have been studied extensively. Nano mechanical behavior determines the applications in nanodevices and nanosystems. Nath et al. [18] have studied the variation of admittance with frequency on the CdS and ZnS quantum dots. These results indicate their potential application in electronics as nano tuned and nano high pass filters. ZnS nanotubes with crossed-channels have been synthesized successfully by Yun Chen et al. [19] in a hydrothermal system using simultaneous solvent-oxidation–hydrolysis reaction. The nanotubes with crossed-channels have potential applications in making nanode- vices, nanoreactors, storage devices, and can be used in high efficient multiple-catalysis. ZnS thin film is used to store solar energy. This film can store solar energy and radiate visible light without photoelectric and photothermic middle transformation processes. This method is a new way to use solar energy [20]. In the present work, we have studied the bonding behavior of ZnS nano material. The statistical approach MEM has been used (maximum entropy method) to determine electron density at any position within the unit cell. The bonding and interaction between the neighboring charges are clearly understood in the present work. 2. Sample preparation Analar grade Na 2 S and ZnCl 2 were taken in the 1:1 ratio and dissolved individually in distilled water in two glass beakers. Contents lists available at ScienceDirect journal homepage: www.elsevier.com/locate/physb Physica B 0921-4526/$ - see front matter & 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.physb.2010.05.069 n Corresponding author. E-mail address: saragow@dataone.in (R. Saravanan). URL: http://www.saraxraygroup.net (R. Saravanan). Physica B 405 (2010) 3700–3703