24November2017

Materials and Electronics Engineering

ZnO nanowires synthesized massively with actively antibacterial properties

Yaozhong Zhang1,*, Chao Zhang1, Hao Tian2, Xiaojun Zhang2, Xiaolin Li1, Lei Yin3, Eric Siu-Wai Kong1

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1Laboratory for Thin Film and Microfabrication Technology, Research Institute of Micro/Nano Science and Technology, Shanghai Jiao Tong University, Shanghai, China
2Laboratory of Molecular Microbial Ecology and Ecogenomics, College of Life Science and Biotechnology, Shanghai Jiaotong University, Shanghai, China
3Shanghai Chang Zheng Hospital, Feng Yang Road No.415, Shanghai 200003,China

Materials and Electronics Engineering 2014,1:6

Publication Date (Web): December 17, 2014 (Article)

DOI:10.11605/mee-1-6

*Corresponding author. E-mail: This email address is being protected from spambots. You need JavaScript enabled to view it.

 

Abstract

 


Figure 1 The procedure schematic of antibacterial activity testing
      ZnO Nanowires (NWs) have been synthesized massively by a modified carbon thermal reduction method. The ZnO nanowires, which looks like cotton, are observed as entangled and curved wire-like single crystalline structures. The edges of the ZnO NWs are smooth and  straight without secondary growth or extra structural features. Antibacterial properties of ZnO NWs against gram-negative bacterium Escherichia coli (E. Coli) have been evaluated by estimating the growth ratio of bacterial colonies in the presence and absence of ZnO NWs in liquid nutrient broth using colony-counting method. The results show that this material performs good antibacterial effect against E. Coli due to extremely large surface areas, high surface state and low crystal defect. Finally, the mechanism of pure ZnO NWs is discussed and it is mainly attributed to the ionic bond properties of ZnO based on noncentral symmetry and polar surfaces, and reactive oxygen species generated by ZnO NWs, which could damage and draw up bacteria. [1]

 

Keywords

ZnO nanowires, antibacterial properties, colony counting, ionic bond properties

 

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Introduction

      Disease-causing organism transmission and microbial contamination are serious issues in health care and food industry. The emergence of antibiotics promised an end to bacteria-based disease since 1950. However, the looming problem of antibiotic-resistant microbes shattered the optimism and complacency. Nowadays, the spreading of antibiotic-resistant pathogens is still a growing concern globally [1]. It is therefore imperative to find an alternative antibacterial agent to tackle this issue.

      Antibacterial agents can be divided into two categories, according to their chemical composition: inorganic and organic agents. Many shortcomings of organic antibacterial agents have heavily limited their applications, such as low heat resistance, high decomposability and short life expectancy [2]. As a result, the use of inorganic antibacterial agents, such as ZnO [3], MgO [4], CuO [5] and Ag-containing materials [6], has attracted great interests and thus considered to be good alternatives to conventional antibiotics for the control of micro-organisms. The key advantages of inorganic antibacterial agents are improved safety and stability, superior durability, less toxicity, greater selectivity and heat resistance, which are lacking in organic antibacterial agents [7, 8].

      Tam et al. [9] reported that ZnO nanorods prepared by hydrothermal method show antibacterial properties against gram-negative Escherichia coli (E. coli) and gram-positive Bacillus atrophaeus. Singh et al [10] reported that shape-controlled hierarchical ZnO architectures prepared by s simple soft chemical approach can inhibit the growth of staphylococcus aureus (S. auerus) bacterium and they are more effective under UV light than in dark conditions. Jalal et al [11] reported ZnO nanofluids prepared by dispersing ZnO nanoparticles in glycerol in the presence of ammonium citrate produces strong antibacterial activity toward E. coli. However, there are still little research about the antibacterial properties of ZnO nanowires (NWs), which are important one-dimensional nanostructure with large surface area and high surface state [12].

      In this work, the antibacterial properties of ZnO NWs fabricated by a modified carbothermal reduction method were investigated. The antibacterial activities of ZnO NWs were tested by using gram-negative E. coli as the model bacterium. The colony-counting method was employed to test antimicrobial abilities and all process was conducted in liquid nutrient broth. The quantitative examination of bacterial activity has been estimated by the growth ratio (Nt/N0) curves as calculated from the number of viable bacterial cells (Nt) at specified time t and the initial viable cells (N0), in which the sample bacterial suspensions taken at specified time t have been diluted 10-4 times firstly and coated on the nutrient agar plates to form colonies.

Experimental section

2.1 Preparation of ZnO NWs

      ZnO NWs were prepared by a modified carbothermal reduction method in our previous work [13]. Firstly, a quartz tube furnace was heated to 1,150°C and a quartz boat was placed in the middle of the furnace, which was filled with mixtures of ZnO  and graphite (325 mesh) powder (2 g) with a weight ratio of 1:0.8. Then, the furnace was purged continuously with a mixed gas of air (0.1 L/min) and N2 gas (4.5 L/min). After about 5 min, white snowflake-like product was carried out by the carrier gas and collected by a 5000-mL flask, covered at the downstream of the quartz tube furnace. The weight of the prepared ZnO NWs was about 0.82 g, which means the nanocrystallization efficiency of this method was 82%. 

2.2 Sample characterizations

      The morphology and microstructure of ZnO NWs were characterized using field-emission scanning electron microscopy (SEM, Ultra 55, Carl Zeiss) and transmission electron microscopy (TEM, JEM-2100, JEOL). The crystal structure of prepared ZnO NWs was analyzed by X-ray diffraction (XRD, D/max- 2200/PC, Rigaku), using Cu Kα (λ = 1.54Å) radiation and the diffraction angel ranges from 20° to 80°. To investigate the optical properties of the prepared ZnO nanowires, UV-VIS absorption (Nicolet Evolution 300) and photoluminescence (PL, Hitachi F-4600) spectroscopy were utilized. All photo images in this paper were taken by Panasonic DMC-FX75 Digital Camera. 

2.3 Tests of antibacterial activity

      The antibacterial properties of ZnO NWs were tested by colony-counting method and gram-negative E. coli were chosen as test bacteria for antibacterial experiment. Luria-Bertani broth and Luria-Bertani agar were used as culturing nutrient sources. In a typical experiment, E. Coli was grown as seed solutions at 37 °C under the condition of shock culturing with the speed of 180 r/min for 5 h. Then the seed solutions (1mL) were diluted into 50 mL Luria-Bertani broth. After that, 70 mg ZnO NWs and 70 μL normal saline (blank control) were added into 7 mL diluted seed solutions respectively and the mixtures were grown at 37 °C under the condition of shock culturing with the speed of 150 r/min. We took bacterial suspension from both samples every 20 min and diluted separately. Then the processed mixture bacterium-solutions were coated on Luria-Bertani agar plates homogeneously. The whole experiment lasted 100 min. Finally, these plates were put into 37 °C incubator for 24 h and we counted the bacteria colonies to evaluate the antibacterial activities of ZnO NWs. By calculating the growth ratio (Nt/N0) between the viable bacterial counts (Nt (CFU/L)) at specified time and the initial counts (N0 (CFU/L)) of bacteria, antibacterial activity was evaluated. The procedure schematic of antibacterial activity testing is shown in Figure 1. 

Figure 1 The procedure schematic of antibacterial activity testing

Figure 1 The procedure schematic of antibacterial activity testing

Results and discussion

      Figure 2 (a) is the photograph of the prepared ZnO nanowires and the flask used for collecting the prepared product. The photograph was taken when the production process was finished. It can be seen that ZnO nanowires are spurted under the action of high temperature and carrier gas. Figure 2 (b) is the image of ZnO nanowires, which are like cotton. Figure 2(c) and 2(d) present a typical SEM image of the ZnO NWs. It shows a general view of the morphology of the nanowires. The ZnO NWs are observed as entangled and curved wire-like structure. The edges of the ZnO NWs are smooth. It shows a straight and smooth nanowire with no secondary growth or extra structural features.

Figure 2 (a) the photograph of the prepared ZnO nanowires and the flask used for collecting the prepared product. (b) the image of ZnO nanowires. A typical (c) low magnification, (d) high magnification SEM image of ZnO NWs.

Figure 2 (a) the photograph of the prepared ZnO nanowires and the flask used for collecting the prepared product. (b) the image of ZnO nanowires. A typical (c) low magnification, (d) high magnification SEM image of ZnO NWs.

   Figure 3 (a) is the EDS spectrum of the prepared ZnO nanowire. The crystal structure of the ZnO NWs was measured by XRD analysis. Figure 3 (b) shows a typical XRD pattern of the ZnO NWs recorded from 20°to 80°. The diffraction peaks are exactly indexed to the hexagonal wurtzite ZnO phase (JCPDS 65-3411) with cell constants of a = 3.24 Å and c = 5.19 Å. Diffraction peaks associated with zinc or carbon were not detected in the prepared sample. The broadening of ZnO peaks is due to the small nanowire size. Figure 3 (c) shows a UV–VIS absorption spectrum of the prepared ZnO nanowires. It can be seen that there was a strong excitonic absorption peak located at 369 nm, attributed to the large exciton binding energy and the good optical quality of the nanowires. The calculated bandgap of the nanowires was 3.36 eV, which was blue shifted by ~0.06 eV with respect to the bulk ZnO of 3.30 eV. The room temperature photoluminescence spectrum of the prepared ZnO nanowires excited at 325 nm is shown in Figure 3 (d). It can be seen that there were an ultraviolet emission peak located at ~381 nm and a strong and broad green-yellow emission peak located at ~508 nm. [13]

Figure 3 (a) EDS spectrum of the prepared ZnO nanowire; (b) The XRD pattern of the prepared ZnO NWs; (c) UV-VIS absorption spectrum of the prepared ZnO nanowire dispersed in ethanol solution; (d) Room temperature photoluminescence spectrum of the prepared ZnO nanowire excited at 325 nm.

Figure 3 (a) EDS spectrum of the prepared ZnO nanowire; (b) The XRD pattern of the prepared ZnO NWs; (c) UV-VIS absorption spectrum of the prepared ZnO nanowire dispersed in ethanol solution; (d) Room temperature photoluminescence spectrum of the prepared ZnO nanowire excited at 325 nm.

   The antibacterial activities of ZnO NWs were examined on gram-negative E. coli by colony-counting method. Fig. 4 shows the image of bacteriological tests of E. coli on solid agar plates with and without ZnO NWs. The results show that only a few E. coli colonies appeared on the solid agar plates with ZnO NWs in Fig. 4(a); however, high-density E. coli colonies are observed on the solid agar plates without ZnO NWs in Fig. 4(b), revealing that ZnO NWs have good ability to inhibit the growth of E.Coli.

Figure 4 The images of bacteriological tests of E. coli on solid agar plates with (a) and without (b) ZnO NWs.

Figure 4 The images of bacteriological tests of E. coli on solid agar plates with (a) and without (b) ZnO NWs.

      We also measured the growth ratio curve of E. Coli in the presence and absence of ZnO NWs. By calculating the ratio (Nt/N0) between the viable bacterial counts (Nt (CFU/L)) at specified time t and the initial counts (N0 (CFU/L)) of bacteria, antibacterial activity was evaluated. It can be seen clearly in Fig. 5 that E.Coli colonies remain stable in the presence of ZnO NWs. On the contrary, the bacterial colonies increase dramatically in the absence of ZnO NWs, reaching nearly 30 times after 60 min and 40 times after 100 min. The comparison between two curves also demonstrates that ZnO NWs can restrain the proliferation of E.Coli.

Figure 5 The growth ratio curve of E.Coli in the presence and absence of ZnO NWs

Figure 5 The growth ratio curve of E.Coli in the presence and absence of ZnO NWs

      A number of detailed antibacterial mechanisms have been proposed to interpret the antibacterial behavior of ZnO and there are mainly two mechanisms which have been widely accepted. One is the ionic bond properties of ZnO. The structure of ZnO can be described as a number of alternating planes composed of tetrahedrally coordinated O2- and Zn2+ ions, stacked alternatively along the c-axis. The oppositely charged ions produce positively charged (0001)-Zn and negatively charged (0001¯)-O polar surfaces, resulting in a normal dipole moment and spontaneous polarization along the c-axis as well as a divergence in surface energy. This kinds of noncentral symmetry and polar surfaces are unsuitable for the growth of bacteria, thus leading to the death of bacteria. Another is chemical interaction between ZnO and bacterium cell which can be explained on the basis of the oxygen species released on the surface of ZnO, which cause fatal damage to microorganisms [14, 15]. When ZnO NWs are irradiated by UV or visible light, electrons (e-) will transfer from valence band (VB) to conduction band (CB) and leave positive holes (h+) in VB in ZnO NWs [16]. Dissolved oxygen (O2) adsorbed on surface of ZnO NWs can react with e- to form superoxide radical (•O2-) and H2O molecules from the suspension of ZnO NWs will be split into .OH and H+ by h+. (•O2-)radicals can in turn react with H+ to generate (HO2•) radicals, then produce hydrogen peroxide anions (HO2) with e-, finally react with H+ to produce molecules of H2O2. The generated H2O2 can penetrate the cell membrane and kill the bacteria [17, 18]. The typical reaction steps in the antibacterial activities can be summarized as follows:

ZnO + hν ZnO (e- + h+)                      (1)

ZnO (e-) + O2 → ZnO + •O2-                   (2)

ZnO (h+) + H2O → ZnO + •OH + H+          (3)

•O2- + 2H+ + ZnO (e-) → H2O2                 (4)

      Besides, the larger surface areas and lower crystal defect are also contributed to the higher antibacterial properties of pure and graphene-decorated ZnO NWs compared with ZnO powder.

Conclusion

      The antibacterial activities of ZnO NWs have demonstrated on the basis of noncentral symmetry and polar surfaces of ZnO. Since ZnO NWs have large surface area and high surface state, they can produce more active oxygen species and thus show good antibacterial properties, making them promising an alternative antibacterial agent in the application of medical and food industries.

References

1. J. Lederberg, Infectious history. Science 288, 287 (2000). doi:10.1126/science.288.5464.287
2. M. Fang, J.H. Chen, X.L. Xu, P.H. Yang, H.F. Hildebrand, Antibacterial activities of inorganic agents on six bacteria associated with oral infections by two susceptibility tests. Int. J. Antimicrob. Ag. 27, 513 (2006). doi:10.1016/j.ijantimicag.2006.01.008
3. N. Jones, B. Ray, K.T. Ranjit, A.C. Manna, Antibacterial activity of ZnO nanoparticle suspensions on a broad spectrum of microorganisms. Fems Microbiol. Lett. 279, 71 (2008). doi:10.1111/j.1574-6968.2007.01012.x
4. S. Makhluf, R. Dror, Y. Nitzan, Y. Abramovich, R. Jelinek, A. Gedanken, Microwave-assisted synthesis of nanocrystalline MgO and its use as a bacteriocide. Adv. Funct. Mater. 15, 1708 (2005). doi:10.1002/adfm.200500029
5. G.G. Ren, D.W. Hu, E.W. Cheng, M.A. Vargas-Reus, P. Reip, R.P. Allaker, Characterisation of copper oxide nanoparticles for antimicrobial applications. Int. J. Antimicrob. Ag. 33, 587 (2009). doi:10.1016/j.ijantimicag.2008.12.004
6. V.K. Sharma, R.A. Yngard, Y. Lin, Silver nanoparticles: Green synthesis and their antimicrobial activities. Adv. Colloid Interfac. 145, 83 (2009). doi:10.1016/j.cis.2008.09.002
7. J. Sawai, T. Yoshikawa, Quantitative evaluation of antifungal activity of metallic oxide powders (MgO, CaO and ZnO) by an indirect conductimetric assay. J. Appl. Microbiol. 96, 803 (2004). doi:10.1111/j.1365-2672.2004.02234.x
8. Y.H. Kim, D.K. Lee, H.G. Cha, C.W. Kim, Y.S. Kang, Synthesis and characterization of antibacterial Ag-SiO2 nanocomposite. J. Phys. Chem. C. 111, 3629 (2007). doi:10.1021/jp068302w
9. K.H. Tam, A.B. Djurisic, C.M.N. Chan, Y.Y. Xi, C.W. Tse, Y.H. Leung, W.K. Chan, F.C.C. Leung, D.W.T. Au, Antibacterial activity of ZnO nanorods prepared by a hydrothermal method. Thin Solid Films 516, 6167 (2008). doi:10.1016/j.tsf.2007.11.081
10. S. Singh, K.C. Barick, D. Bahadur, Shape-controlled hierarchical ZnO architectures: photocatalytic and antibacterial activities. Cryst. Eng. Comm. 15, 4631 (2013). doi:10.1039/C3CE27084J
11. R. Jalal, E.K. Goharshadi, M. Abareshi, M. Moosavi, A. Yousefi, P. Nancarrow, ZnO nanofluids: Green synthesis, characterization, and antibacterial activity. Mater. Chem. Phys. 121, 198 (2010). doi:10.1016/j.matchemphys.2010.01.020
12. H.B. Chen, X. Wu, L.H. Gong, C. Ye, F. Qu, G.Z. Shen, Hydrothermally grown ZnO micro/nanotube arrays and their properties. Nanoscale Res. Lett. 5, 570 (2010). doi:10.1007/s11671-009-9506-4
13. Z.H. Zhou, C.H. Zhan, Y.Y. Wang, Y.J. Su, Z. Yang, Y.F. Zhang, Rapid mass production of ZnO nanowires by a modified carbothermal reduction method. Mater. Lett. 65, 832 (2011). doi:10.1016/j.matlet.2010.12.032
14. K. Sunada, Y. Kikuchi, K. Hashimoto, A. Fujishima, Bactericidal and detoxification effects of TiO2 thin film photocatalysts. Environ. Sci. Technol. 32, 726 (1998). doi:10.1021/es970860o
15. G. Apperot, A. Lipovsky, R. Dror, N. Perkas, Y. Nitzan, R. Lubart, A. Gedanken, Enhanced antibacterial activity of nanocrystalline ZnO due to increased ROS-mediated cell injury. Adv. Funct. Mater. 19, 842 (2009). doi:10.1002/adfm.200801081
16. R. Georgekutty, M.K. Seery, S. C. Plllal, A highly efficient Ag-ZnO photocatalyst: Synthesis, properties, and mechanism. J. Phys. Chem. C. 112, 13563 (2008). doi:10.1021/jp802729a
17. O. Yamamoto, M. Komatsu, J. Sawai, Z. Nakagawa, Effect of lattice constant of zinc oxide on antibacterial characteristics. J. Mater. Sci-Mater. M. 15, 847 (2004). doi:10.1023/B:JMSM.0000036271.35440.36
18. L.L. Zhang, Y. Jiang, Y.L. Ding, N. Daskalakis, L. Jeuken, M. Povey, A.J. Neill, D.W. York, Mechanistic investigation into antibacterial behaviour of suspensions of ZnO nanoparticles against E. coli. J. Nanopart. Res. 12, 1625 (2010). doi:10.1007/s11051-009-9711-1

Acknowledgements

      This work was supported by National Natural Science Foundation of China (No. 8117219), Shanghai Science and Technology Grants (No. 12NM0503800). We also would like to thank the Instrumental Analysis Center of SJTU for the analysis support.

References

1. J. Lederberg, Infectious history. Science 288, 287 (2000). doi:10.1126/science.288.5464.287 
2. M. Fang, J.H. Chen, X.L. Xu, P.H. Yang, H.F. Hildebrand, Antibacterial activities of inorganic agents on six bacteria associated with oral infections by two susceptibility tests. Int. J. Antimicrob. Ag. 27, 513 (2006). doi:10.1016/j.ijantimicag.2006.01.008 
3. N. Jones, B. Ray, K.T. Ranjit, A.C. Manna, Antibacterial activity of ZnO nanoparticle suspensions on a broad spectrum of microorganisms. Fems Microbiol. Lett. 279, 71 (2008). doi:10.1111/j.1574-6968.2007.01012.x 
4. S. Makhluf, R. Dror, Y. Nitzan, Y. Abramovich, R. Jelinek, A. Gedanken, Microwave-assisted synthesis of nanocrystalline MgO and its use as a bacteriocide. Adv. Funct. Mater. 15, 1708 (2005). doi:10.1002/adfm.200500029 
5. G.G. Ren, D.W. Hu, E.W. Cheng, M.A. Vargas-Reus, P. Reip, R.P. Allaker, Characterisation of copper oxide nanoparticles for antimicrobial applications. Int. J. Antimicrob. Ag. 33, 587 (2009). doi:10.1016/j.ijantimicag.2008.12.004 
6. V.K. Sharma, R.A. Yngard, Y. Lin, Silver nanoparticles: Green synthesis and their antimicrobial activities. Adv. Colloid Interfac. 145, 83 (2009). doi:10.1016/j.cis.2008.09.002
7. J. Sawai, T. Yoshikawa, Quantitative evaluation of antifungal activity of metallic oxide powders (MgO, CaO and ZnO) by an indirect conductimetric assay. J. Appl. Microbiol. 96, 803 (2004). doi:10.1111/j.1365-2672.2004.02234.x 
8. Y.H. Kim, D.K. Lee, H.G. Cha, C.W. Kim, Y.S. Kang, Synthesis and characterization of antibacterial Ag-SiO2 nanocomposite. J. Phys. Chem. C. 111, 3629 (2007). doi:10.1021/jp068302w 
9. K.H. Tam, A.B. Djurisic, C.M.N. Chan, Y.Y. Xi, C.W. Tse, Y.H. Leung, W.K. Chan, F.C.C. Leung, D.W.T. Au, Antibacterial activity of ZnO nanorods prepared by a hydrothermal method. Thin Solid Films 516, 6167 (2008). doi:10.1016/j.tsf.2007.11.081 
10. S. Singh, K.C. Barick, D. Bahadur, Shape-controlled hierarchical ZnO architectures: photocatalytic and antibacterial activities. Cryst. Eng. Comm. 15, 4631 (2013). doi:10.1039/C3CE27084J
11. R. Jalal, E.K. Goharshadi, M. Abareshi, M. Moosavi, A. Yousefi, P. Nancarrow, ZnO nanofluids: Green synthesis, characterization, and antibacterial activity. Mater. Chem. Phys. 121, 198 (2010). doi:10.1016/j.matchemphys.2010.01.020 
12. H.B. Chen, X. Wu, L.H. Gong, C. Ye, F. Qu, G.Z. Shen, Hydrothermally grown ZnO micro/nanotube arrays and their properties. Nanoscale Res. Lett. 5, 570 (2010). doi:10.1007/s11671-009-9506-4 
13. Z.H. Zhou, C.H. Zhan, Y.Y. Wang, Y.J. Su, Z. Yang, Y.F. Zhang, Rapid mass production of ZnO nanowires by a modified carbothermal reduction method. Mater. Lett. 65, 832 (2011). doi:10.1016/j.matlet.2010.12.032 
14. K. Sunada, Y. Kikuchi, K. Hashimoto, A. Fujishima, Bactericidal and detoxification effects of TiO2 thin film photocatalysts. Environ. Sci. Technol. 32, 726 (1998). doi:10.1021/es970860o 
15. G. Apperot, A. Lipovsky, R. Dror, N. Perkas, Y. Nitzan, R. Lubart, A. Gedanken, Enhanced antibacterial activity of nanocrystalline ZnO due to increased ROS-mediated cell injury. Adv. Funct. Mater. 19, 842 (2009). doi:10.1002/adfm.200801081 
16. R. Georgekutty, M.K. Seery, S. C. Plllal, A highly efficient Ag-ZnO photocatalyst: Synthesis, properties, and mechanism. J. Phys. Chem. C. 112, 13563 (2008). doi:10.1021/jp802729a 
17. O. Yamamoto, M. Komatsu, J. Sawai, Z. Nakagawa, Effect of lattice constant of zinc oxide on antibacterial characteristics. J. Mater. Sci-Mater. M. 15, 847 (2004). doi:10.1023/B:JMSM.0000036271.35440.36
18. L.L. Zhang, Y. Jiang, Y.L. Ding, N. Daskalakis, L. Jeuken, M. Povey, A.J. Neill, D.W. York, Mechanistic investigation into antibacterial behaviour of suspensions of ZnO nanoparticles against E. coli. J. Nanopart. Res. 12, 1625 (2010). doi:10.1007/s11051-009-9711-1

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Additional Info

  • Type of Publishing: JOUR - Journal
  • Title:

    ZnO nanowires synthesized massively with actively antibacterial properties

  • Author: Yaozhong Zhang, Chao Zhang, Hao Tian, Xiaojun Zhang, Xiaolin Li, Lei Yin, Eric Siu-Wai Kong
  • Year: 2014
  • Volume: 1
  • Issue: 1
  • Journal Name: Materials and Electronics Engineering
  • Publisher: Nicety Press Company Limited
  • ISSN: 2410-1648
  • URL: http://www.meej.org/volume-1/december-2014/item/365-the-relationship-between-hardness-and-grain-size-in-electron-beam-evaporated-pb1-xgexte-thin-films
  • Abstract:

    ZnO Nanowires (NWs) have been synthesized massively by a modified carbon thermal reduction method. The ZnO nanowires, which looks like cotton, are observed as entangled and curved wire-like single crystalline structures. The edges of the ZnO NWs are smooth and  straight without secondary growth or extra structural features. Antibacterial properties of ZnO NWs against gram-negative bacterium Escherichia coli (E. Coli) have been evaluated by estimating the growth ratio of bacterial colonies in the presence and absence of ZnO NWs in liquid nutrient broth using colony-counting method. The results show that this material performs good antibacterial effect against E. Coli due to extremely large surface areas, high surface state and low crystal defect. Finally, the mechanism of pure ZnO NWs is discussed and it is mainly attributed to the ionic bond properties of ZnO based on noncentral symmetry and polar surfaces, and reactive oxygen species generated by ZnO NWs, which could damage and draw up bacteria. [1]

  • Publish Date: Wednesday, 17 December 2014
  • Start Page: 6
  • DOI: 10.11605/mee-1-6