Savka Vračević, et al., Antimicrobial and photocatalytic properties of doped and undoped zinc oxide nanoparticles Contemporary Materials, XI‒2 (2020) Page 128 of 134 Original scientific papers UDK 616.314-089.28:615.281 DOI 10.7251/COMEN2002128V ANTIMICROBIAL AND PHOTOCATALYTIC PROPERTIES OF DOPED AND UNDOPED ZINC OXIDE NANOPARTICLES Savka Vračević 1,* , Aleksandra Šmitran 2 , Sanja Pržulj 1 , Dragana Gajić 1 , Mladena Malinović 1 , Ljiljana Božić 2 , Dijana Jelić 1 1 University of Banja Luka, Faculty of Natural Sciences and Mathematics, Chemistry Department, Mladena Stojanovića 2, Banja Luka, Republic of Srpska, Bosnia and Herzegovina 2 University of Banja Luka, Faculty of Medicine, Save Mrkalja 14, Banja Luka, Republic of Srpska, Bosnia and Herzegovina Abstract: In this paper, zinc oxide nanoparticles doped with copper (ZnO/Cu NP) were synthesized by using black and green tea, vitamin C and trisodium citrate as a reduction agent. Antimicrobial and photocatalytic properties were tested. The antimicrobial activity of the doped synthesized ZnO NP against the clinical isolates of Acinetobacter baumannii and methicillin resistant Staphylococcus aureus (MRSA) was performed by the agar well diffusion method. ZnO NP with all four reduction agents showed good antimicrobial efficiency against both microorganisms, with similar inhibition zone. Photocatalytic activity was more pronounced in case of undoped, pure ZnO nanoparticles, while the best results for doped ZnO samples were obtained for ZnO/Cu NPs using black tea. Keywords: zinc oxide; nanoparticles; antimicrobial activity; photocatalysis. 1. INTRODUCTION Zinc oxide is well known multifunctional material; it is used in optoelectronics [1], biotechnology [2], microbiology field [3] etc. ZnO has a unique ability to form different nanoforms with different morphology: nanorods nanobelts, nanorings, nanosticks, nanospheres and nanoflowers. These ZnO nanoforms have better chemical and photochemical stability, greater surface area, optical permeability and biocompatibility. Due to its non- toxicity and antimicrobial properties ZnO is very often used as a cosmetic or pharmaceutical ingredient [4]. There are some reports in which antimicrobial activity is connected with generation of reactive oxygen species on the surface of inorganic oxides [5]. Also, inorganic oxides contain mineral elements which are essential to humans and exhibit activity when taken in small amounts [6]. Even though ZnO is a multifunctional material, its usage is somehow restricted due to inability to interact with solar system effectively and due to high recombination rate of electron and hole [7]. It is important to emphasize that nanomaterials have the ability to upgrade their properties due to incorporation of some other elements which significantly contributes to their application area [8,9]. This presents hypothesis of the presented research work. ZnO material was chosen because this material proved to be the most popular host material for metal incorporation [10]. There are great numbers of synthesis methods for ZnO reported in scientific literature. Some of them are sol-gel [11], solvent-free method [12], hydrothermal method [13], electrodeposition [14], pyrolysis [15], etc. The choice of synthesis method is very connected to nanomaterial properties such as uniformity, particle size and ultimately with its application. If application process requires good electrical and magnetic properties, the first evaluation step of a nanomaterial is toward photocatalytic abilities. On the other hand, if application goes in medical direction antimicrobial efficiency is very important. It was reported that ZnO nanoshapes keep their photocatalytic activity but lose their active sites upon aggregation due to absence of capping agents [7]. Chang et al reported that with higher concentration of Zn toxicity prevail over health benefit for Zn acting as essential mineral [16]. In order to overcome these disadvantages of pure ZnO, there are some reports in literature dealing with possibility to change absorption characteristic of ZnO via incorporation of some other elements in ZnO nanostructure. Silver, gold and copper are mostly used for better performances of ZnO properties. * Corresponding author: savka.jankovic@pmf.unibl.org