Research paper Antibacterial activities of copper nanoparticle-decorated organically modified montmorillonite/epoxy nanocomposites Gautam Das a,1 , Ranjan Dutta Kalita b , Pankaj Gogoi a , Alok K. Buragohain b , Niranjan Karak a, ⁎ a Advanced Polymer and Nanomaterial Laboratory, Chemical Sciences Department, Tezpur University, India b Department of Molecular Biology and Biotechnology, Tezpur University, Napaam 784028, India abstract article info Article history: Received 11 June 2012 Received in revised form 31 December 2013 Accepted 2 January 2014 Available online xxxx Keywords: Nanostructures Coatings Mechanical properties Biomaterials Clay mineral Organically modified montmorillonite (OMt) was decorated by copper nanoparticles (with average diameters of 10 to 20 nm) at three different mass percentages at room temperature. Such OMt-Cu nanohybrid was incorpo- rated into Mesua ferrea L. seed oil modified epoxy resin (BPSE) to obtain clay mineral polymer nanocomposites (CPN). The nanohybrids and CPN were characterized by SEM, XRD, HRTEM and FTIR and UV–visible spectroscopic techniques. The antimicrobial efficacy of the as-prepared OMt-Cu nanohybrid and OMt-Cu/epoxy nanocomposites was also premeditated and significant antibacterial activity against ubiquitous Gram negative bacteria Klebsiella pneumonia and Gram positive bacteria Staphylococcus aureus was observed. In addition the OMt-Cu/epoxy nano- composites exhibited enhancement in thermostability over the pristine system by 15 °C and tensile strength and in scratch hardness by 2.5 and 2.1 units respectively along with marginal improvement in the elongation at break value. The study reveals that the OMt-Cu/epoxy nanocomposites have the potentiality to be used as advanced antimicrobial materials. © 2014 Elsevier B.V. All rights reserved. 1. Introduction Nanotechnology has emerged as a rapid growing field with multifac- eted application for new materials at the nanoscale level (Atiyeh et al., 2007). The unique combination of different nanostructures creates material properties which have a great potential in optical, electrical, medical, antibacterial etc. applications due to interfacial interactions that can be established between nanoscaled architectures (Drelich et al., 2011; Huang et al., 1997; Liu and Bando, 2003; Magdassi et al., 2010). Metallic nanoparticles for biomedical applications are the most promising as they show good antibacterial properties due to their large specific surface area (SSA) and high specificity (Gong et al., 2007). Copper and its complexes have found their uses as efficient materials for sterilizing liquids, clothing and also antibiotics for centuries (Borkow and Gabbay, 2009; Dutkiewicz and Fallowfield, 1998; Kaali et al., 2011; Pang et al., 2009; Perelshtein et al., 2009). Compared to other metals, copper has the advantage of insignificant sensitivity to human tissues (Hostynek and Maibach, 2004), however microorganisms have been found to show high sensitivities to copper (Michels et al., 2005). Recent- ly, due to the development of some resistant bacterial strains (Kyriacou et al., 2004) the antibacterial activity of nanomaterials, such as silver (Akhavan and Ghaderi, 2009a, 2011, 2009b; Ferraris et al., 2010) and copper based nanostructures (Akhavan and Ghaderi, 2009c Akhavan et al., 2011; Gao et al., 2009; Kim and Park, 2008; Pachoalino et al., 2008), with their unique size dependent properties has attracted great attention. The use of clay and clay minerals as a support for the synthesis of nanoparticles has been recognized as a promising method. Montmoril- lonite (Mt) in this regard, has been an apt choice due to its chemical and physical nature. Mt has been used for preparation of a wide range of nanoparticles like gold and silver, among others (Manikandan et al., 2007). This hybrid material is vouched for application in advanced coating materials such as antibacterial coatings, in biomedical devices or in antimicrobial packaging (Cioffi et al., 2005; Sunada et al., 2003). The rationale for the use of copper lies in the strong toxic action this metal exerts against prokaryotes (i.e., all types of bacteria), while it is much less toxic against eukaryotes (i.e., all other organisms). Thus dispersion of copper or copper oxide particles into organic matrixes has been employed as antifouling coatings by the paint industry, mainly for maritime applications. There are reports on the use of copper/polymer nanocomposites as a bioactive coating against bacteria (Anyaogu et al., 2008). However the use of the combined system of OMt decorated copper nanoparticles for such application is not known. This combined system has the advantage of being both a reinforcing filler as well as a bioactive material. Clay with its high aspect ratio provides effective rein- forcement of the matrix, further it also serves as a site for the anchorage of the copper nanoparticles. Today, the quest is for nontoxic antimicro- bial protection, which can prevent the surface from biofouling without causing environmental pollution and poisoning. A scrutiny of the Applied Clay Science 90 (2014) 18–26 ⁎ Corresponding author. Tel.: +91 3712 267009; fax: +91 3712 267006. E-mail address: karakniranjan@yahoo.com (N. Karak). 1 Present address: Department of Environment & Energy Engineering, Gachon University, Gyeonggi-Do 461-701, South Korea. 0169-1317/$ – see front matter © 2014 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.clay.2014.01.002 Contents lists available at ScienceDirect Applied Clay Science journal homepage: www.elsevier.com/locate/clay