Ceramics International xxx (xxxx) xxx Please cite this article as: Hossein Safardoust-Hojaghan, Ceramics International, https://doi.org/10.1016/j.ceramint.2020.10.097 Available online 15 October 2020 0272-8842/© 2020 Elsevier Ltd and Techna Group S.r.l. All rights reserved. Green synthesis, characterization and antimicrobial activity of carbon quantum dots-decorated ZnO nanoparticles Hossein Safardoust-Hojaghan a , Masoud Salavati-Niasari a, * , Omid Amiri b, c , Somaye Rashki d , Mahdi Ashraf a a Institute of Nano Science and Nano Technology, University of Kashan, Kashan, P.O. Box 87317-51167, Iran b Department of Chemistry, College of Science, University of Raparin, Rania, Kurdistan Region, Iraq c Department of Chemistry, College of Science, International University of Erbil, Iraq d Department of Microbiology and Immunology, School of Medicine, Kashan University of Medical Sciences, P.O.Box:87137.81147, Kashan, Iran A R T I C L E INFO Keywords: Carbon quantum dots Minimum inhibitory concentration Nanocomposites Agar disk-diffusion ABSTRACT In this research, ZnO nanoparticles (ZnO NPs) and Carbon Quantum Dots-decorated ZnO nanoparticles (ZnO/ CQDs NCs) were prepared via different procedures and precursors. Soya chunk was applied as a source of carbon for the preparation of CQDs. Crystalline structure, purity, size, and morphological properties of products were investigated via X-ray diffraction (XRD) analysis, energy dispersive spectroscopy (EDS), Transmission Electron Microscopy (TEM), FT-IR, and Scanning Electron Microscopy (SEM) respectively. Findings showed that homo- geneity, size, and morphological properties of products can be intensively affected via different precursors and procedures. From the homogeneity, size, and morphological point of view, the hydrothermal route, ammonia, 5 h, and 180 ◦ C were the optimum procedure, pH adjuster, temperature, and time respectively. Optimum product was applied for carrying out minimum inhibitory concentration (MIC) and Agar disk-diffusion tests against various microorganisms. Results demonstrated that prepared ZnO NPs have maximum antibacterial activity against Staphylococcus aureus (19.53 μg/ml) and ZnO/CQDs NCs have no inhibitory effect against tested mi- croorganisms. For ZnO NPs, the disk diffusion test proved that the highest growth inhibition zone was related to Staphylococcus aureus (15 mm). The presence of CQDs in ZnO/CQDs NCs reduces the inhibitory effect of ZnO NPs intensively. 1. Introduction In recent years, ZnO nanostructures have been found more and more attention [1,2]. From an electronic point of view, ZnO is a wide direct-gap semiconductor that is crystallized in wurtzite structure [3,4]. For their interesting properties, ZnO nanostructures are widely used in various felds such as the paint industry [5], semiconductor-based in- dustry, water splitting [6], water disinfection [7], and cosmetic industry [8]. Till now various ZnO-based nanostructures have been applied in biomedical felds that include from cancer therapy to antimicrobial products. The biocompatibility of zinc oxide is a prominent factor in bio-related applications [9,10]. Various reports have demonstrated that the cytotoxicity of ZnO nanoparticles depends strongly on the size and morphology of nanoparticles. Achuth Padmanabhan and et al. investi- gated the effect of ZnO nanoparticles on ovarian cancer via human ovarian cancer cell lines. They found that the cytotoxicity of ZnO nanoparticles increases via size reduction [11]. So, the shape and size controlling of ZnO nanostructures could provide a most benefcial product. Doping is another route for improvement of ZnO-based nano- structures. Till now, various elements such as indium [12], magnesium [13], and aluminum [14] have been doped to zinc oxide. ZnO-based nanocomposites with excellent properties are another effort for the amelioration of ZnO nanostructures. So far, a variety of ZnO-based nanocomposites have been prepared and applied in bio-related appli- cations [15–17]. Cheng Zhong and et al. prepared bacterial cellulo- se/ZnO nanocomposites via a simple precipitation method and studied photocatalytic and antibacterial properties of nanocomposites. They found that prepared biocompatible nanocomposites have antibacterial activities against both Gram-positive and Gram-negative bacterial strains [18]. For excellent biocompatibility, electronic properties, non-complex preparation method, and availability, carbon quantum dots (CQDs) are a good candidate for the improvement of ZnO properties * Corresponding author. E-mail address: salavati@kashanu.ac.ir (M. Salavati-Niasari). Contents lists available at ScienceDirect Ceramics International journal homepage: www.elsevier.com/locate/ceramint https://doi.org/10.1016/j.ceramint.2020.10.097 Received 8 August 2020; Received in revised form 23 September 2020; Accepted 13 October 2020