Ag/CuO nanoparticles prepared from a novel trinuclear compound [Cu(Imdz) 4 (Ag(CN) 2 ) 2 ] (Imdz ¼ imidazole) by a pyrolysis display excellent antimicrobial activity Jaydeep Adhikary a , Balaram Das b , Sourav Chatterjee c , Sandeep Kumar Dash b , Sourav Chattopadhyay b , Somenath Roy b , Jeng-Wei Chen d, ** , Tanmay Chattopadhyay c, * a Department of Chemistry, University of Calcutta, 92 A. P. C. Road, Kolkata, 700 009, India b Immunology & Microbiology Laboratory, Department of Human Physiology with Community Health, Vidyasagar University, Midnapore, 721102, West Bengal, India c Department of Chemistry, Panchakot Mahavidyalaya, Sarbari, Purulia, Pin-723121, India d Department of Physics, National Taiwan University, Taipei,106, Taiwan article info Article history: Received 13 December 2015 Received in revised form 8 February 2016 Accepted 8 February 2016 Available online 11 February 2016 Keywords: X-ray crystal structure Ag/CuO nanoparticles Antimicrobial activity abstract One copper and two silver containing one hetero tri-nuclear precursor compound [Cu(Imdz) 4 (Ag(CN) 2 ) 2 ] (1) (Imdz ¼ Imidazole) has been synthesized and characterized by single crystal X-ray diffraction. Simple pyrolysis of the complex at 550  C for 4 h afforded Ag/CuO nanoparticles (NPs). The synthesized nanoparticles were characterized by ultravioletevisible (UVeVis), Fourier transform infrared (FT-IR), X- ray powder diffraction (XRPD), dynamic light scattering (DLS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray (EDX) and X-ray photo electron spectroscopy (XPS). Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) have been employed as model microbial species to study the anti-microbial activity of the synthesized NPs. The NPs showed potent anti-microbial activity evidenced from the Minimum Inhibitory Concentration (MIC) and Mini- mum Bactericidal Concentration (MBC) values. Very high level of cell uptake and then generation of reactive oxygen species (ROS) are the origin of such strong antimicrobial activity for the NPs. However, the cytotoxicity level of the NPs towards normal human cell is very low. © 2016 Elsevier B.V. All rights reserved. 1. Introduction Nanomaterials have considered growing attention due to their versatile properties [1e3]. Among the different types of nano- materials, nanostructured transition metals and transition metal oxides deserve special interest for their exceptional physical and chemical properties along with the technological applications [4e9]. In particular, Ag NPs have recently been revived due to the use of the NPs against the increasing threat of antibiotic resistance [10e12]. Ag nanoparticles interact with microbial cells via multiple biochemical pathways, including the production of reactive oxygen species (ROS) that can damage cell and finally cause cell death [13e19]. In spite of high bactericidal activity of silver-loaded ma- terials, Ag þ elution is an important issue [20]. To enhance bacteri- cidal activity and suppress the elution of Ag þ , it is needed to develop a new inorganic material that will effectively produce ROS and reduce Ag þ elution. Some studies were already reported where modified Ag NPs have been used in antibacterial activity [21,22]. In some previous reports, Ag nanoparticles have been immobilized onto various substrates such as polymers, silica, carbon, iron oxide, zeolite, layered double hydroxide (LDH) etc [23e33]. Some conju- gated silver-metal oxide particles like Ag/CeO 2 , Ag/ZnO and Ag/CuO were already reported [34e37]. These particles not only prevented the aggregation of Ag nanoparticles but also enhanced their anti- bacterial capacity. Gram-negative pathogens like Pseudomonas aeruginosa, Escherichia coli, Klebsiella pneumoniae and Gram- positive pathogens including Staphylococcus aureus, Enterococcus spp. have been associated with increased resistance to antibiotics, resulting in increased morbidity and mortality [38,39]. So there is an urgent need for the discovery and development of novel * Corresponding author. ** Corresponding author. E-mail addresses: jwchen@phys.ntu.edu.tw (J.-W. Chen), tanmayc2003@gmail. com (T. Chattopadhyay). Contents lists available at ScienceDirect Journal of Molecular Structure journal homepage: http://www.elsevier.com/locate/molstruc http://dx.doi.org/10.1016/j.molstruc.2016.02.029 0022-2860/© 2016 Elsevier B.V. All rights reserved. Journal of Molecular Structure 1113 (2016) 9e17