Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 125 (2014) 73–78
Contents lists available at ScienceDirect
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy journal homepage: www.elsevier.com/locate/saa
Synthesis and characterization of CuO–montmorillonite nanocomposite by thermal decomposition method and antibacterial activity of nanocomposite Sh. Sohrabnezhad a,⇑, M.J. Mehdipour Moghaddam b, T. Salavatiyan a a b
Department of Chemistry, Faculty of Science, University of Guilan, P.O. Box 1914, Rasht, Iran Department of Biology, Faculty of Science, University of Guilan, P.O. Box 1914, Rasht, Iran
h i g h l i g h t s
g r a p h i c a l a b s t r a c t
We used thermal decomposition
method for synthesis of CuO/MMT nanocomposite. The antibacterial activity of CuO– MMT nanocomposite was tested against Escherichia coli. The minimum inhibitory concentration value against E. coli of CuO–MMT was 0.1 ng/mL. The XRD result implied that CuO nanoparticles can exist in micropore of MMT. The FT-IR spectra confirm substitution of aluminum in octahedral layer by Cu2+ cations.
a r t i c l e
i n f o
Article history: Received 4 November 2013 Received in revised form 10 January 2014 Accepted 16 January 2014 Available online 31 January 2014 Keywords: Antibacterial activity Copper oxide Diffuse reflectance spectroscopy Thermal decomposition CuO–montmorillonite
CuO nanoparticles
a b s t r a c t CuO–montmorillonite (CuO–MMT) nanocomposite was synthesized by thermal decomposition methods and characterized by diffuse reflectance spectroscopy (DRS), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and transmission electron microscopy (TEM). The resultant particles are nearly spherical and particle size is in the range of 3–5 nm. X-ray diffraction patterns indicate that MMT (1.22 nm) has a d-spacing higher than CuO–MMT nanocomposite (0.97 nm). This result implied that CuO nanoparticles can exist in micropore of MMT. The disappeared of band at 918 cm1 and decreasing of intensity of 3630 cm1 band in FT-IR spectra confirm substitution of aluminum in octahedral layer by Cu2+ cations. The diffuse reflectance spectra show that the value of band gap energy for CuO–MMT nanocomposite (2.7 eV) is more than CuO nanoparticles (1.2 eV). It was found that decrease in the particle size of CuO nanoparticles due to quantum size effect. The antibacterial activity of CuO–MMT nanocomposite was tested against Escherichia coli. Nanocomposite showed efficient bactericidal effect. Ó 2014 Elsevier B.V. All rights reserved.
Introduction Copper and its complexes have been widely utilized as effective materials for sterilizing liquids, textiles and also human tissues for
⇑ Corresponding author. Tel.: +98 131 3233262. E-mail address: [email protected] (Sh. Sohrabnezhad). http://dx.doi.org/10.1016/j.saa.2014.01.080 1386-1425/Ó 2014 Elsevier B.V. All rights reserved.
centuries [1]. CuO nanoparticles are stable, robust and have a longer shelf life compared to organic antimicrobial agents. Some advantages of copper materials including their bactericidal activity were well known even since the time of ancient civilizations. Today copper sometimes is utilized as an agent for purification of water and inactivation of some microorganisms and bacteria [2]. In spite of the negligible responsiveness of human tissues to copper [3], microorganisms show high sensitivities to copper [4].
74
Sh. Sohrabnezhad et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 125 (2014) 73–78
It is well known that clay minerals possess many unique properties such as an ability to ‘‘swell’’ in aqueous environments, high surface area, and high cationic exchange capacity [5] which lead them ideal adsorbents for multiple applications. Among the many kinds of clay minerals, montmorillonite (MMT) has been recognized as an effective adsorbent due to its large specific surface area (SSA) and high cationic exchange capacity (CEC) [6]. Montmorillonite are a subset of aluminosilicate clays having a 2:1 layer structure [7]. Within the layers of these clays, substitution of other metal ions for silicon or aluminum can occur resulting in a net negative charge on the surface of the clay platelet. This negative charge is offset by hydrated cations, such as Na+ and Ca2+. The surface chemistry of montmorillonite clays can be altered by exchanging the predominant interlaminar cations with organic materials and inorganic cations that are positively charged. In recent years, the use of inorganic antimicrobial agents has attracted interest for the control of microbes [8]. The key advantages of inorganic antimicrobial agents are improved safety and stability as compared to organic antimicrobial agents. CuO with a band gap ranging from 1.2 to 1.6 eV [9] can be also utilized as effective photocatalyst materials [10–12]. In our previous work we synthesized the CuO nanoparticles onto MCM-41 matrix by solid state reaction with band gap 1.7 eV. This composite is good candidate for photocatalysis under visible light [10]. Recently, due to development of some resistant bacteria strains against the antibiotics [11,12], the antibacterial activity of nanomaterials, such as silver [13–15] and copper [16–18], with their unique size dependent properties has attracted great attentions. But, antibacterial activity of copper and copper oxide nanoparticles has not been extensively studied, likely due to fast oxidation of metallic copper nanoparticles in exposure to air [19]. Among not many investigations concerning the antibacterial activity of CuO, Trapalis et al. [20] reported antibacterial activity of CuO/SiO2 composite thin film. They indicated that antibacterial activity of the composite decreased after thermal reduction of the film to Cu/SiO2 film, due to reduction of surface area of the total metal contained in the coating. Abou Neel et al. [21] also reported antibacterial activity of CuO-doped phosphate glass fibers. Perelshtein et al. [22] reported significant antibacterial activity of CuOcotton nanocomposite. Toxicity of nanosized and bulk CuO to bacteria was studied and compared to toxicity of corresponding ZnO and TiO2 by Heinlaan et al. [23]. Recently, Shape effect on antibacterial activity of CuO nanoflakes and flower-shaped was reported by Karthikeyan et al. [24] and Sathyamoorthy et al. [25]. They found that all the synthesized CuO crystals with the different morphologies exhibit good bactericidal activities. Thongtem et al. [26] reported synthesis of monoclinic CuO thin films on Cu foils by a simple wet chemical method. They showed that CuO film has better antimicrobial activity against S. aureus than E. coli. In the present work, bactericidal activity of CuO nanoparticles immobilized into interlayer of montmorillonite was investigated against E. coli bacteria. E. coli as a representative of fecal, facultative anaerobic microorganisms was used to represent gram negative (G-) bacteria. The thermal decomposition approaches was used for synthesis of CuO nanoparticles in montmorillonite. The lattice parameters, diffuse reflectance spectroscopy, antibacterial activity of nanocomposite was studied using different characterization techniques. Experimental Materials The commercial sodium montmorillonite clay (NaMMT), CuO > MMT. It has been reported that when nanoparticles of metallic Cu (or Cu oxide) are dispersed throughout clay, Cu2+ ions are released when the materials interact with an aqueous phase [24,43,44]. These Cu2+ ions are responsible for the exhibited antibacterial activity of the materials. Under physiologic conditions, bacterial cell walls are negatively charged due to functional groups such as carboxyls, phosphate and hydroxyl present in lipoproteins at the surface [24,45]. The mechanism of the antimicrobial action of Cu2+ ions involves the binding of Cu2+ ions to functional groups of proteins and enzymes, which causes inactivation and inhibition in cell processes [46,47]. This is the main reason for the antibacterial property of the synthesized CuO nanoparticles and CuO–MMT nanocomposite. In this current study, the MIC value obtained was 0.1 ng/mL for CuO–MMT nanocomposite, whereas that of CuO nanoparticles and MMT matrix was 10, 100 ng/mL. The results showed that the surface morphologies of the synthesized materials are different. One of the major factors that determine the MIC of a material is the interaction of bacteria with active Cu2+ ions [24]. Due to the comparatively larger surface area CuO–MMT clay and smaller particle size of CuO in MMT, released Cu2+ ions in CuO–MMT is more than CuO nanoparticles, thus E. coli bacteria have more opportunity to come in contact with the Cu2+ ions. This might be the reason for comparatively lower MIC value of CuO–MMT, which has a larger surface area than CuO and MMT. Conclusions
the order of antibacterial activities of nanomaterials was CuO– MMT > CuO > MMT. Antibacterial activity was attributed to the presence of ionic copper that are released when the CuO materials interact with an aqueous phase. References [1] [2] [3] [4] [5] [6] [7]
[8] [9] [10] [11] [12] [13] [14] [15] [16] [17] [18] [19] [20] [21] [22] [23] [24] [25] [26] [27] [28] [29]
[30] [31] [32] [33] [34] [35] [36] [37] [38] [39] [40]
In summary, CuO nanoparticles and CuO–montmorillonite (CuO–MMT) nanocomposite was synthesized by thermal decomposition method. After copper modification, the formation of CuO over the clay was observed by TEM, XRD, FT-IR and DRS. XRD result implied that CuO nanoparticles can exist in micropore of MMT. The comparison of antibacterial activity of different synthesized samples (CuO nanoparticles and CuO–MMT nanocomposite) clearly indicated that the CuO nanosphers incorporated in micropores of montmorillonite is the most active antibacterial for inhibition properties over the growth of E. coli. The results demonstrated that
[41] [42] [43] [44] [45] [46] [47]
H.H.A. Dollwet, J.R.J. Sorenson, Trace Elem. Med. 2 (1985) 80. Y. Pang, J.A. Patterson, T.J. Applegate, Poult. Sci. 88 (2009) 586–592. J.J. Hostynek, H.I. Maibach, Rev. Environ. Health 18 (2003) 153. H.T. Michels, Stand. News. 34 (2006) 28–31. P. Laszlo, J. Phys. Org. Chem. 11 (1998) 356–361. H. Chen, X.M. He, X.M. Rong, W.L. Chen, P. Cai, W. Liang, Appl. Clay Sci. 46 (2009) 102–108. G. Borchardt, Smectites, in: J.B. Dixon, S.B. Weed (Eds.), Minerals in Soil Environments Soil Science of America, second ed., Madison, WI, 1989, pp. 675– 727. M. Wilczynski, Ceram. Eng. Sci. Proc. 21 (2000) 81–83. A. Nezamzadeh-Ejhieh, M. Karimi-Shamsabadi, Chem. Eng. J. 228 (2013) 631– 641. X. Liu, Zh. Li, Q. Zhang, F. Li, T. Kong, Mater. Lett. 72 (2012) 49–52. A. El-Trass, H. ElShamy, I. El-Mehasseb, M. El-Kemary, Appl. Surf. Sci. 258 (2012) 2997–3001. Sh. Sohrabnezhad, A. Valipour, Spectrochim. Acta, Part A 114 (2013) 298–302. O. Akhavan, E. Ghaderi, Curr. Appl. Phys. 9 (2009) 1381–1385. V. Gopinath, S. Priyadarshini, N. Meera Priyadharsshini, K. Pandian, P. Velusamy, Mater. Lett. 91 (2013) 224–227. A. Seung-Hyun Min, A. Jae-Hun Yang, B. Joon Young Kim, Kwon Young-Uk, Micropor. Mesopor. Mater. 128 (2010) 19–25. K. Malachova, P. Praus, Z. Rybkova, O. Kozak, Appl. Clay Sci. 53 (2011) 642– 645. J. Ramyadevi, K. Jeyasubramanian, A. Marikani, G. Rajakumar, A.A. Rahuman, Mater. Lett. 71 (2012) 114–116. O. Akhavan, E. Ghaderi, Surf. Coat. Technol. 205 (2010) 219–223. O. Akhavan, M. Abdolahad, R. Asadi, J. Phys. D Appl. Phys. 42 (2009) 135416. C.C. Trapalis, M. Kokkoris, G. Perdikakis, G. Kordas, J. Sol. – Gel. Sci. Technol. 26 (2003) 1213–1218. E.A. Abou Neel, I. Ahmed, J. Pratten, S.N. Nazhat, J.C. Knowles, Biomaterials 26 (2005) 2247–2254. I. Perelshtein, G. Applerot, N. Perkas, E. Wehrschuetz-Sigl, A. Hasmann, G. Guebitz, A. Gedanken, Surf. Coat. Technol. 204 (2009) 54–57. M. Heinlaan, A. Ivask, I. Blinova, H.-C. Dubourguier, A. Kahru, Chemosphere 71 (2008) 1308–1316. T. Pandiyarajan, R. Udayabhaskar, S. Vignesh, R. Arthur James, B. Karthikeyan, Mater. Sci. Eng., C 33 (2013) 2020–2024. K. Mageshwari, R. Sathyamoorthy, J. Mater. Sci. Technol. 29 (2013) 893–1004. N. Ekthammathat, T. Thongtem, S. Thongtem, Appl. Surf. Sci. 277 (2013) 211– 217. D. Das, B.Ch. Nath, P. Phukon, S.K. Dolui, Colloids Surf. B 101 (2013) 430–433. R.M. Torres Sanchez, M. Genet, S. Yunes, XV Cong. AFQQI. C-95 Tandil, 2007. R.M. Torres Sanchez, V. Lastiri, in: R. Trindade, R. Melamed, L. Gonzaga, S. Sobrado, J. Peres Barbosa (Eds.), XIII International Conference on Heavy Metals in the Environment, Rio de Janeiro, 2005, CD. ISBN 85-7227-212-7. M. Yang, J. He, J. Colloid Interf. Sci. 355 (2011) 15–22. D.M. Fernandes, R. Silva, A.A.W. Hechenleitner, E. Radovanovic, M.A.C. Melo, E.A.G. Pineda, Mater. Chem. Phys. 115 (2009) 110–115. C. Mosser, L.J. Michot, F. Villieras, M. Romeo, Clay Clay Miner. 45 (1997) 789– 802. H. Jia, W. Hou, L. Wei, B. Xu, X. Liu, Dent. Mater. 24 (2008) 244–249. K.M. Parida, D. Rath, J. Colloid Interf. Sci. 340 (2009) 209–217. A.A. Jalil, M.A.H. Satar, S. Triwahyono, H.D. Setiabudi, N.H.N. Kamarudin, N.F. Jaafar, N. Sapawe, R. Ahamad, J. Electroanal. Chem. 701 (2013) 50–58. P. Wang, X. Zheng, X. Wu, X. Wei, L. Zhou, Micropor. Mesopor. Mater. 149 (2012) 181–185. M.A. Vicente-Rodriguez, M. Suarez, M.A. Banares-Munoz, J.D. Lopez-Gonzalez, Spectrochim. Acta Part A 52 (1996) 1685–1694. G.E. Christidis, C. WScott, A.C. Dunham, Appl. Clay Sci. 12 (1997) 329–347. V.C. Farmer, in: H.V. Olephen, J.J. Fripiat (Eds.), Data Handbook for Clay Materials and Other, 1999, pp. 285–337. M. Vaseem, A. Umar, Y. Hahn, D. Kim, K. Lee, J. Jang, J. Lee, Catal. Commun. 10 (2008) 11–16. B. Tyagi, Ch.D. Chudasama, R.V. Jasra, Spectrochim. Acta Part A 64 (2006) 273– 278. T. Pandiyarajan, R. Udayabhaskar, S. Vignesh, R.A. James, B. Karthikeyan, Mater. Sci. Eng. C 33 (2013) 2020–2024. S. Min, J. Yang, J.Y. Kim, Y. Kwon, Micropor. Mesopor. Mater. 128 (2010) 19–25. S. Egger, R.P. Lehmann, M.J. Height, M.J. Loessner, M. Schuppler, Appl. Environ. Microbiol. 75 (2009) 2973–2976. A. Azam, A.S. Ahmed, M. Oves, M.S. Khan, S.S. Habib, A. Memic, Int. J. Nanomed. 7 (2012) 6003–6009. R.T. Belly, G.C. Kydd, Dev. Ind. Microbiol. 23 (1982) 567–577. P.D. Bragg, D.J. Rainnie, J. Microbiol. 20 (1974) 883–889.
Contents lists available at ScienceDirect
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy journal homepage: www.elsevier.com/locate/saa
Synthesis and characterization of CuO–montmorillonite nanocomposite by thermal decomposition method and antibacterial activity of nanocomposite Sh. Sohrabnezhad a,⇑, M.J. Mehdipour Moghaddam b, T. Salavatiyan a a b
Department of Chemistry, Faculty of Science, University of Guilan, P.O. Box 1914, Rasht, Iran Department of Biology, Faculty of Science, University of Guilan, P.O. Box 1914, Rasht, Iran
h i g h l i g h t s
g r a p h i c a l a b s t r a c t
We used thermal decomposition
method for synthesis of CuO/MMT nanocomposite. The antibacterial activity of CuO– MMT nanocomposite was tested against Escherichia coli. The minimum inhibitory concentration value against E. coli of CuO–MMT was 0.1 ng/mL. The XRD result implied that CuO nanoparticles can exist in micropore of MMT. The FT-IR spectra confirm substitution of aluminum in octahedral layer by Cu2+ cations.
a r t i c l e
i n f o
Article history: Received 4 November 2013 Received in revised form 10 January 2014 Accepted 16 January 2014 Available online 31 January 2014 Keywords: Antibacterial activity Copper oxide Diffuse reflectance spectroscopy Thermal decomposition CuO–montmorillonite
CuO nanoparticles
a b s t r a c t CuO–montmorillonite (CuO–MMT) nanocomposite was synthesized by thermal decomposition methods and characterized by diffuse reflectance spectroscopy (DRS), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and transmission electron microscopy (TEM). The resultant particles are nearly spherical and particle size is in the range of 3–5 nm. X-ray diffraction patterns indicate that MMT (1.22 nm) has a d-spacing higher than CuO–MMT nanocomposite (0.97 nm). This result implied that CuO nanoparticles can exist in micropore of MMT. The disappeared of band at 918 cm1 and decreasing of intensity of 3630 cm1 band in FT-IR spectra confirm substitution of aluminum in octahedral layer by Cu2+ cations. The diffuse reflectance spectra show that the value of band gap energy for CuO–MMT nanocomposite (2.7 eV) is more than CuO nanoparticles (1.2 eV). It was found that decrease in the particle size of CuO nanoparticles due to quantum size effect. The antibacterial activity of CuO–MMT nanocomposite was tested against Escherichia coli. Nanocomposite showed efficient bactericidal effect. Ó 2014 Elsevier B.V. All rights reserved.
Introduction Copper and its complexes have been widely utilized as effective materials for sterilizing liquids, textiles and also human tissues for
⇑ Corresponding author. Tel.: +98 131 3233262. E-mail address: [email protected] (Sh. Sohrabnezhad). http://dx.doi.org/10.1016/j.saa.2014.01.080 1386-1425/Ó 2014 Elsevier B.V. All rights reserved.
centuries [1]. CuO nanoparticles are stable, robust and have a longer shelf life compared to organic antimicrobial agents. Some advantages of copper materials including their bactericidal activity were well known even since the time of ancient civilizations. Today copper sometimes is utilized as an agent for purification of water and inactivation of some microorganisms and bacteria [2]. In spite of the negligible responsiveness of human tissues to copper [3], microorganisms show high sensitivities to copper [4].
74
Sh. Sohrabnezhad et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 125 (2014) 73–78
It is well known that clay minerals possess many unique properties such as an ability to ‘‘swell’’ in aqueous environments, high surface area, and high cationic exchange capacity [5] which lead them ideal adsorbents for multiple applications. Among the many kinds of clay minerals, montmorillonite (MMT) has been recognized as an effective adsorbent due to its large specific surface area (SSA) and high cationic exchange capacity (CEC) [6]. Montmorillonite are a subset of aluminosilicate clays having a 2:1 layer structure [7]. Within the layers of these clays, substitution of other metal ions for silicon or aluminum can occur resulting in a net negative charge on the surface of the clay platelet. This negative charge is offset by hydrated cations, such as Na+ and Ca2+. The surface chemistry of montmorillonite clays can be altered by exchanging the predominant interlaminar cations with organic materials and inorganic cations that are positively charged. In recent years, the use of inorganic antimicrobial agents has attracted interest for the control of microbes [8]. The key advantages of inorganic antimicrobial agents are improved safety and stability as compared to organic antimicrobial agents. CuO with a band gap ranging from 1.2 to 1.6 eV [9] can be also utilized as effective photocatalyst materials [10–12]. In our previous work we synthesized the CuO nanoparticles onto MCM-41 matrix by solid state reaction with band gap 1.7 eV. This composite is good candidate for photocatalysis under visible light [10]. Recently, due to development of some resistant bacteria strains against the antibiotics [11,12], the antibacterial activity of nanomaterials, such as silver [13–15] and copper [16–18], with their unique size dependent properties has attracted great attentions. But, antibacterial activity of copper and copper oxide nanoparticles has not been extensively studied, likely due to fast oxidation of metallic copper nanoparticles in exposure to air [19]. Among not many investigations concerning the antibacterial activity of CuO, Trapalis et al. [20] reported antibacterial activity of CuO/SiO2 composite thin film. They indicated that antibacterial activity of the composite decreased after thermal reduction of the film to Cu/SiO2 film, due to reduction of surface area of the total metal contained in the coating. Abou Neel et al. [21] also reported antibacterial activity of CuO-doped phosphate glass fibers. Perelshtein et al. [22] reported significant antibacterial activity of CuOcotton nanocomposite. Toxicity of nanosized and bulk CuO to bacteria was studied and compared to toxicity of corresponding ZnO and TiO2 by Heinlaan et al. [23]. Recently, Shape effect on antibacterial activity of CuO nanoflakes and flower-shaped was reported by Karthikeyan et al. [24] and Sathyamoorthy et al. [25]. They found that all the synthesized CuO crystals with the different morphologies exhibit good bactericidal activities. Thongtem et al. [26] reported synthesis of monoclinic CuO thin films on Cu foils by a simple wet chemical method. They showed that CuO film has better antimicrobial activity against S. aureus than E. coli. In the present work, bactericidal activity of CuO nanoparticles immobilized into interlayer of montmorillonite was investigated against E. coli bacteria. E. coli as a representative of fecal, facultative anaerobic microorganisms was used to represent gram negative (G-) bacteria. The thermal decomposition approaches was used for synthesis of CuO nanoparticles in montmorillonite. The lattice parameters, diffuse reflectance spectroscopy, antibacterial activity of nanocomposite was studied using different characterization techniques. Experimental Materials The commercial sodium montmorillonite clay (NaMMT), CuO > MMT. It has been reported that when nanoparticles of metallic Cu (or Cu oxide) are dispersed throughout clay, Cu2+ ions are released when the materials interact with an aqueous phase [24,43,44]. These Cu2+ ions are responsible for the exhibited antibacterial activity of the materials. Under physiologic conditions, bacterial cell walls are negatively charged due to functional groups such as carboxyls, phosphate and hydroxyl present in lipoproteins at the surface [24,45]. The mechanism of the antimicrobial action of Cu2+ ions involves the binding of Cu2+ ions to functional groups of proteins and enzymes, which causes inactivation and inhibition in cell processes [46,47]. This is the main reason for the antibacterial property of the synthesized CuO nanoparticles and CuO–MMT nanocomposite. In this current study, the MIC value obtained was 0.1 ng/mL for CuO–MMT nanocomposite, whereas that of CuO nanoparticles and MMT matrix was 10, 100 ng/mL. The results showed that the surface morphologies of the synthesized materials are different. One of the major factors that determine the MIC of a material is the interaction of bacteria with active Cu2+ ions [24]. Due to the comparatively larger surface area CuO–MMT clay and smaller particle size of CuO in MMT, released Cu2+ ions in CuO–MMT is more than CuO nanoparticles, thus E. coli bacteria have more opportunity to come in contact with the Cu2+ ions. This might be the reason for comparatively lower MIC value of CuO–MMT, which has a larger surface area than CuO and MMT. Conclusions
the order of antibacterial activities of nanomaterials was CuO– MMT > CuO > MMT. Antibacterial activity was attributed to the presence of ionic copper that are released when the CuO materials interact with an aqueous phase. References [1] [2] [3] [4] [5] [6] [7]
[8] [9] [10] [11] [12] [13] [14] [15] [16] [17] [18] [19] [20] [21] [22] [23] [24] [25] [26] [27] [28] [29]
[30] [31] [32] [33] [34] [35] [36] [37] [38] [39] [40]
In summary, CuO nanoparticles and CuO–montmorillonite (CuO–MMT) nanocomposite was synthesized by thermal decomposition method. After copper modification, the formation of CuO over the clay was observed by TEM, XRD, FT-IR and DRS. XRD result implied that CuO nanoparticles can exist in micropore of MMT. The comparison of antibacterial activity of different synthesized samples (CuO nanoparticles and CuO–MMT nanocomposite) clearly indicated that the CuO nanosphers incorporated in micropores of montmorillonite is the most active antibacterial for inhibition properties over the growth of E. coli. The results demonstrated that
[41] [42] [43] [44] [45] [46] [47]
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