In this study, a new nanocomposite based on Polyvinylalcohol/Polyaniline/Zinc oxide (PVA/PANi/ ZnO) was successfully synthesized. ZnO powder was used to produce its nanoparticles (NPs) using conventional method. PVA/PANi composite was used to produce ZnO NPs. Polyaniline was synthesized in sol solution of PVA in the presence of ammonium persulphate. Morphology and the size of ZnO NPs in nanocomposites were studied via Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD) analysis and

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... red (IR) spectroscopy. According to XRD results, the average size of prepared ZnO NPs was found to be at the range 22 -34 nm. SEM images were shown hexagonal shape for ZnO NPs, which was used for the investigation of antibacterial property. Finally, the antibacterial activity of the prepared ZnO NPs and nanocomposites was evaluated against two bacteria of Gram positive Staphylococcus aureus and Gram negative Escherichia coli using paper disc diffusion method. The results were shown that the prepared nanocomposites were effective against two bacteria. A. Samzadeh-Kermani et al. 2 ology, medicine, and electronics because of their unique particle size and shape dependent physical, chemical and biological properties [3] [4] . ZnO is a wide band gap (3.37 eV) II-VI compound semiconductor which has received a lot of attentions over the last decade because, it has a wide range of useful properties including electrical [5], optical [6], chemical [7] and magnetic [8]. Therefore, ZnO has become extraordinarily important because of its wide applications such as in catalysis [9], gas sensing [10], semiconductors [11], piezoelectric devices [12], UV-shielding materials [13], polymer coating [14], photochemical [15] and antibacterial agents [16]. As ZnO is a multifunctional material, the study on its NPs has been focused on their preparation using various methods including solid state reaction [9], flame spray pyrolysis [17], microwave-assisted method [18], sonochemical route [19], sol-gel [20], hydrothermal [21] and mechanochemical methods [22] . ZnO powder inhibits the growth of gram-positive bacteria more strongly than gram-negative bacteria [23] . This research was focused on metal oxides like ZnO as antibacterial agents to prevent bacterial growth. Recently, there have been several reports regarding the antimicrobial activity of ZnO NPs [24] . ZnO displays many interesting properties at nanoscale, and has significant applications as antibacterial and antifungal agents. It also holds importance in biomedical sciences [25] . ZnO has shown a considerable antibacterial activity at pH values at the range 7 -8 without the presence of light [26] . Polyvinyl alcohol (PVA) is an important water-soluble transparent polymer, and is extensively used in industries due to the excellent chemical and physical properties, non-toxicity, good chemical resistance, good film formation capacity, biodegradability and high crystal modulus. PVA is used here in hydrolyzed form with the degree of 85% hydrolysis [27] . It is a polymer with many technological, pharmaceutical and biomedical applications [28] . It can be used for coating of ZnO [29], titanium dioxide [30] and Ag [31] . PANi, an intrinsically conducting polymer, has received great attentions because of its wide potential formany technological applications, such as sensors, anticorrosion coatings, electro rheological fluids [32] and good environmental stability [33] . PANi is usually obtained as powder via precipitation polymerization [34] .