Synthesis of ZnO nanoparticles and study of their antibacterial and antifungal properties Deepali Sharma a, ⁎, Jaspreet Rajput a , B.S. Kaith a , Mohinder Kaur b , Sapna Sharma b a Department of Chemistry, Dr. B. R. Ambedkar National Institute of Technology, Jalandhar 144011, India b Department of Basic Sciences, Dr. Y. S. Parmar University of Horticulture and Forestry, Nauni-173230(Solan), India abstract article info Available online 25 August 2010 Keywords: ZnO nanoparticles Antibacterial Antifungal ROS In this paper, ZnO nanoparticles have been synthesized with and without the use of surfactants under different reaction conditions. The size of the ZnO nanoparticles varied in diameter (2 nm–28 nm) according to the reaction conditions employed. Promising particle size dependent antibacterial and antifungal activities of the ZnO nanoparticles have been observed. Transmission electron microscopy (TEM), X-ray diffraction (XRD) and Infrared spectroscopy (FTIR) techniques were used to characterize the particle size and morphology. © 2010 Elsevier B.V. All rights reserved. 1. Introduction In the recent years, nanoparticles within the size range of 100 nm have become an area of extensive research and concern due to their potential application in wide areas of science and technology. At present inorganic metal oxides (TiO 2 , MgO, CaO and ZnO) have attracted interest as antimicrobial agents because of their safety and stability. Methods like indirect conductometric assay have been used to investigate the minimal antibacterial activity of ceramic powders [1]. Among these, zinc oxide nanostructures are at the forefront of research due to their unique properties and widespread applications. The advantage of using ZnO nanoparticles is that they strongly inhibit the action of pathogenic microbes when used in small concentrations. Moreover these are durable and show great selectivity and heat resistance [2,3]. Since, ZnO nanoparticles possess antibacterial and antifungal activities at lower concentrations, therefore, the thin coatings of such nanoparticles can be used for the preparation of microbial resistant articles. Moreover, use of ZnO nanoparticles as antifungal agent does not affect the soil fertility in comparison to traditional antifungal agents. ZnO belongs to the class of metal oxides, which is characterized by photocatalytic and photo-oxidising capacity against chemical and biological species. It utilizes a multifunctional nanoplatform that bombards malignant cells from outside through the release of reactive oxygen species (ROS) [4]. The bactericidal properties of ZnO nanoparticles are due to electrostatic interaction between the nanoparticles and the cell surface and increased association of the nanoparticles results in the enhanced cell damage. The toxic effects of ZnO nanoparticles towards the pathogenic species of bacteria are enhanced on prolonged contact between the bacterium cell mem- brane and the nanoparticles. The bacterium and fungal lipid bilayer gets ruptured due to cytotoxic behaviour of ZnO nanoparticles resulting in the drainage of the cytoplasmic contents [5]. The ZnO nanostructures have novel applications in ultra-violet lasers, gas sensors, energy conversion, catalysis and biomedical sciences [6–12]. These days various environmentally benign processes such as solution based synthesis, template assisted growth and microwave synthesis are being used to synthesize ZnO nanostructures of diverse morphologies [13–20]. These synthetic methods are appealing as they are simple and lead to large scale production of nanoparticles. Moreover, they offer many advantages over the other sophisticated techniques. These have excellent control over stoichi- ometry and morphology using organic/capping molecules and inexpensive equipments. As ZnO is a polar crystal with hexagonal phase, the properties of ZnO are strongly dependent on the synthesis process and the external conditions (reaction temperature, concen- tration of reactants and type of capping agents used) during the processing of nanostructures. In the past decade, various synthetic amphoteric surfactants have been employed in the synthesis of ZnO nanostructures [21–23]. ZnO is an n-type semiconductor with wide direct band gap (3.37 eV), high exciton energy (60 meV) at room temperature which allows it to act as an efficient semiconducting and piezoelectric material [24,25]. These nanoparticles act as biosensors because of fast electron kinetics and biocompatibility. In the case of ZnO nanopar- ticles, the surface properties (surface-to-volume ratio) lead to the investigation of interaction of nanoparticles with the cell wall of fungi and bacteria [26]. The size of the particles plays an important role in studying the antimicrobial activity of the nanoparticles. The nano- particles enter the cell wall of microbes through carrier proteins or ion Thin Solid Films 519 (2010) 1224–1229 ⁎ Corresponding author. E-mail address: dps_chem@yahoo.co.in (D. Sharma). 0040-6090/$ – see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.tsf.2010.08.073 Contents lists available at ScienceDirect Thin Solid Films journal homepage: www.elsevier.com/locate/tsf