- Email: [email protected]
Morphology-controlled synthesis of ZnO crystals with twinned structures and the morphology dependence of their antibacterial activities
Materials Letters 115 (2014) 205–207
Contents lists available at ScienceDirect
Materials Letters journal homepage: www.elsevier.com/locate/matlet
Morphology-controlled synthesis of ZnO crystals with twinned structures and the morphology dependence of their antibacterial activities Da-Hae Jin a, Dahye Kim a, Youngsik Seo b, Heonyong Park b, Young-Duk Huh a,n a b
Department of Chemistry, Dankook University, Gyeonggi-Do 448-701, Republic of Korea Department of Molecular Biology, Dankook University, Gyeonggi-Do 448-701, Republic of Korea
art ic l e i nf o
a b s t r a c t
Article history: Received 7 October 2013 Accepted 16 October 2013 Available online 23 October 2013
ZnO crystals with twinned structures were prepared by using a hydrothermal reaction. N,N′-Dimethylethylenediamine and sodium 1-heptanesulfonate were used as the hydroxide ion generator and the morphology controller respectively. As the concentration of sodium 1-heptanesulfonate increases, the morphology of the ZnO crystals varies from thin hexagonal rods to thick hexagonal plates, and the ratio of the areas of the (001) polar and (110) nonpolar planes increases, as determined from XRD data. Further, the antibacterial activity of the ZnO crystals appears to increase with increases in the ratio of the areas of their (001) polar and (110) nonpolar planes, which provides insight into the morphology dependence of the antibacterial activity of ZnO. & 2013 Elsevier B.V. All rights reserved.
Keywords: Crystal growth Microstructure Morphology Antibacterial activity ZnO
1. Introduction The morphology-controlled synthesis of inorganic oxides has recently been extensively investigated because their optical, catalytic, and antibacterial properties depend on their morphologies, i.e. on their surface atomic arrangements [1,2]. The specific atomic arrangement on the surface can be selected by fine tuning the morphology of the inorganic oxide. Morphology-controlled syntheses of inorganic oxides can thus be developed by simply adjusting the synthetic conditions and examining the resulting morphologies. Zinc oxide (ZnO) is an important inorganic oxide that has been widely used in solar cells, gas sensors, and photocatalysts [3,4]. Moreover, nanograined ZnO doped with magnetic atoms have been extensively investigated due to their high temperature ferromagnetism [5–7]. Since ZnO has a hexagonal wurtzite crystal structure, the hexagonal prisms or plates of ZnO have (001) polar planes and (110) nonpolar planes that are parallel and perpendicular to the c axis respectively [8,9]. The main focus of the research into the morphology-dependent properties of ZnO has been its photocatalytic activity. The (001) polar planes of ZnO have higher photocatalytic activity than (110) nonpolar planes [10]. The morphology dependence of the antibacterial activities of ZnO has also been investigated. Flower-like ZnO with a highly exposed (001) polar plane has a higher antibacterial activity than ZnO spherical aggregates, fusiformshaped microrods, and rod-like and sphere-like crystals [11,12].
However, it has been difficult to evaluate the antibacterial activities of the (001) polar and (110) nonpolar planes of ZnO because ZnO products have highly diverse morphologies. Therefore, fine morphological tuning is required to determine the morphology dependence of the antibacterial activity of ZnO, and in particular the antibacterial activities of the (001) polar and (110) nonpolar planes. ZnO crystals with twinned structures are commonly obtained by utilizing the characteristic reactions of protonated amines with the (001) and (001) polar planes [13]. Twinned dumbbelllike ZnO has been prepared with a simple solution method by using hexamethylenetetramine [14]. Twinned hourglass-like ZnO crystals were prepared with a solvothermal method in the presence of zinc acetylacetonate in toluene [15]. Twinned hexagonal prism ZnO crystals were prepared by using a microwaveassisted method in mixed solvents consisting of water and ethylene glycol [16]. However, relatively little is known about the morphology dependence of the antibacterial activities of twinned ZnO structures. This paper presents a simple hydrothermal method for the preparation of twinned ZnO structures from ZnCl2 and N,N′-dimethylethylenediamine (DMEDA) in the presence of sodium 1-heptanesulfonate (C7H15SO3Na). Further, we show that the concentration of C7H15SO3Na is a crucial factor in the control of the morphologies and the aspect ratios of the ZnO crystals.
2. Experimental n
Corresponding author. Tel.: þ 82 31 80053154; fax: þ 82 31 80053148. E-mail address: [email protected] (Y.-D. Huh).
0167-577X/$ - see front matter & 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.matlet.2013.10.056
ZnCl2 (98%, Aldrich), N,N′-dimethylethylenediamine (DMEDA, 95%, Aldrich), and sodium 1-heptanesulfonate (C7H15SO3Na, 98%, TCI)
206
D.-H. Jin et al. / Materials Letters 115 (2014) 205–207
were used as received. In a typical synthesis of ZnO, 0.345 mL of DMEDA was added to 30 mL of a 0.10 M ZnCl2 solution. The solution was then added to 30 mL of a 0.05 M C7H15SO3Na solution. The final mixed solution was transferred to a 100 mL Teflon-lined autoclave and heated at 140 1C for 24 h. The product was centrifuged, washed several times with water and dried in an oven at 60 1C for 24 h. Other concentrations (0.30 M, 0.60 M, and 1.0 M) of C7H15SO3Na were also used to obtain various morphologies of ZnO, with the remaining conditions held constant. The structures and morphologies of the ZnO products were characterized by using powder X-ray diffraction (XRD, PANalytical, X'Pert-PRO MPD) and scanning electron microscopy (SEM, Hitachi S-4300) respectively. The antibacterial activities of the ZnO products were measured with a previously reported method [4]. 100 mL of Escherichia coli overnight culture was aliquoted evenly into 5 mL Luria-Bertani (LB) media containing 100 mg/mL of each ZnO product. The aliquoted E. coli cultures were then incubated in a 37 1C shaking incubator for the indicated periods of time. The optical densities were measured at 600 nm by using a UV–vis spectrophotometer (Perkin-Elmer Lambda 25).
shown in Fig. 1(c), with an estimated aspect ratio of 1.7. When the concentration of C7H15SO3Na was finally increased to 1.0 M, the ZnO crystals were thick twinned hexagonal plates, as shown in Fig. 1(d). This morphology has a significantly decreased aspect ratio, 0.9. The twinned morphologies of the ZnO products evolve from thin hexagonal rods with bipyramidal ends to thick hexagonal plates with increases in the C7H15SO3Na concentration. Fig. 2 shows the XRD patterns and Miller indices of the ZnO crystals obtained in the presence of various concentrations of C7H15SO3Na. All the peaks in Fig. 2 are in good agreement with the reported data for hexagonal ZnO (JCPDS 36-1451, a¼ 0.3249 nm and c ¼0.5206 nm). No other peaks were detected, so we conclude that this method yields ZnO free from impurities. Hydroxide ions (OH ) and protonated DMEDA, DMEDAH þ , are produced by the addition of DMEDA. The zinc ion (Zn2 þ ) reacts with OH to form ZnO22 ion, and finally ZnO is formed. The C7H15SO3 ion acts as a morphology-directing surfactant and so competes with ZnO22 ions in the formation of ZnO product. The possible chemical reactions producing ZnO are as follows: DMEDA (l)þ H2O⇄DMEDAH þ (aq)þOH (aq)
(1)
Zn2 þ (aq) þ4OH (aq)⇄ZnO22 (aq) þ2H2O
(2)
3. Results and discussion
ZnO22 (aq) þH2O⇄ZnO (s) þ2OH (aq)
(3)
Fig. 1 shows SEM images of the ZnO products obtained with the hydrothermal method and various concentrations of C7H15SO3Na. For [C7H15SO3Na]¼0.05 M, twinned hexagonal rod-like ZnO with bipyramidal ends and an average length of 10.6 mm and an average diameter of 1.0 mm were formed with an aspect ratio of 10.6, as shown in Fig. 1(a). A boundary is evident in the middle of each pair of linked hexagonal rods. Both ends of each rod have pyramidal shapes. When the concentration of C7H15SO3Na was increased to 0.30 M, shorter twinned hexagonal ZnO crystals were obtained, as shown in Fig. 1(b). The ends of the hexagonal rods are flattened, so twinned hexagonal prisms of ZnO have formed. The average length and diameter of the twinned hexagonal prisms are 6.6 mm and 1.4 mm respectively, with an estimated aspect ratio of 4.7. When the concentration of C7H15SO3Na was increased to 0.60 M, shorter twinned hexagonal prism ZnO crystals were formed, as
Fig. 3 shows the variation in the ratio of the XRD intensities of (002) and (110) with the C7H15SO3Na concentration. As the C7H15SO3Na concentration increases, the ratio of the intensities of (002) and (110) of the four ZnO products increases from 0.7 to 1.3, which suggests that the proportion of the (002) polar plane increases with respect to that of the (110) nonpolar plane of the hexagonal prisms. The characteristics of (001) planes resembles those of (002) planes. The absorption of C7H15SO3 ions onto the (001) polar surface prevents the reaction of ZnO22 ions. Thus, the length of the ZnO hexagonal prisms is shortened by the presence of the C7H15SO3 ions. Therefore, the ratio of the areas of the (001) polar plane and the (110) nonpolar plane of the ZnO products can with this method be simply tuned by varying the concentration of C7H15SO3Na, obtaining morphologies from thin hexagonal rods to thick hexagonal plates.
Fig. 1. SEM images of the ZnO products prepared with various concentrations of C7H15SO3Na: (a) 0.05 M, (b) 0.30 M, (c) 0.60 M, and (d) 1.0 M.
D.-H. Jin et al. / Materials Letters 115 (2014) 205–207
207
Fig. 4 shows the growth rates of E. coli in the absence or presence of ZnO products prepared with various concentrations of C7H15SO3Na. The incubation time for growth to 50% is known as the half maximal growth time. The half maximal growth times were 4.1, 5.5, 6.6, 7.1, and 9.2 h for E. coli cultures in the absence of ZnO and in the presence of ZnO products prepared with 0.05 M, 0.30 M, 0.60 M, and 1.0 M C7H15SO3Na, respectively. Thus the antibacterial activity of ZnO depends on its morphology. Thick twinned hexagonal prisms of ZnO have the highest antibacterial activity. Therefore, the (001) polar plane of ZnO plays an important role in its antibacterial activity against E. coli. 4. Conclusions
Fig. 2. XRD patterns for the ZnO products prepared with various concentrations of C7H15SO3Na: (a) 0.05 M, (b) 0.30 M, (c) 0.60 M, and (d) 1.0 M.
Various twinned morphologies of ZnO were prepared with a hydrothermal reaction by varying the C7H15SO3Na concentration. As the C7H15SO3Na concentration increases, the twinned ZnO structures evolve from thin hexagonal rods with bipyramidal ends to thick hexagonal plates, and the ratio of the areas of the (001) polar plane and the (110) nonpolar plane of ZnO also increases. The antibacterial activities also vary with the morphology of ZnO, which suggests that the polar properties of the (001) plane play key roles in the antibacterial activity of these ZnO crystals. Acknowledgment This study was supported by the Basic Science Research Program through the National Research Foundation of Korea funded by the Ministry of Education, Science and Technology (2010–0007492). References [1] [2] [3] [4] [5] [6]
Fig. 3. Ratio of the XRD intensities of (002) and (110) as a function of the C7H15SO3Na concentration.
[7] [8] [9] [10] [11] [12] [13] [14] [15] [16]
Fig. 4. E. coli growth rates in the absence (triangles) or presence of ZnO products prepared with various concentrations of C7H15SO3Na: (a) 0.05 M (inverted triangles), (b) 0.30 M (circles), (c) 0.60 M (stars), and (d) 1.0 M (diamonds).
Qi L. Coord Chem Rev 2010;254:1054–71. He M, Jiu H, Liu Y, Tian Y, Li D, Sun Y, et al. Mater Lett 2013;92:154–6. Lee YJ, Kim S, Park SH, Park H, Huh YD. Mater Lett 2011;65:818–20. Chang J, Ahmed R, Wang H, Liu H, Li R, Wang P, et al. J Phys Chem C 2013;117:13836–44. Dietl T, Ohno H, Matsukura F, Cibert J, Ferrand D. Science 2000;287:1019–22. Straumal BB, Mazilkin AA, Protasova SG, Straumal PB, Myatiev AA, Schütz G, et al. Philos Mag 2013;93:1371–83. Straumal BB, Protasova SG, Mazilkin AA, Schütz G, Goering E, Baretzky B, et al. JETP Lett 2013;97:367–77. Jang ES, Won JH, Hwang SJ, Choy JH. Adv Mater 2006;18:3309–12. Ge MY, Wu HO, Niu L, Liu JF, Chen SY, Shen PY, et al. J Cryst Growth 2007;305:162–6. Mclaren A, Valdes-Solis T, Li G, Tsang SC. J Am Chem Soc 2009;131:12540–1. Tong GX, Du FF, Liang Y, Hu Q, Wu RN, Guan JG, et al. J Mater Chem B 2013;1:454–63. Talebian N, Amininezhad SM, Doudi M. J Photochem Photobiol B 2013;120:66–73. Wang Y, Hou Z, Guo H, Shen L, Wang G, Cui F, et al. Mater Lett 2013;91:107–10. Yu Q, Yu C, Yang H, Fu W, Chang L, Xu J, et al. Inorg Chem 2007;46:6204–10. Xu L, Hu YL, Pelligra C, Chen CH, Jin L, Huang H, et al. Chem Mater 2009;21:2875–85. Zhang L, Zhu YJ. Appl Phys A 2009;97:847–52.
Contents lists available at ScienceDirect
Materials Letters journal homepage: www.elsevier.com/locate/matlet
Morphology-controlled synthesis of ZnO crystals with twinned structures and the morphology dependence of their antibacterial activities Da-Hae Jin a, Dahye Kim a, Youngsik Seo b, Heonyong Park b, Young-Duk Huh a,n a b
Department of Chemistry, Dankook University, Gyeonggi-Do 448-701, Republic of Korea Department of Molecular Biology, Dankook University, Gyeonggi-Do 448-701, Republic of Korea
art ic l e i nf o
a b s t r a c t
Article history: Received 7 October 2013 Accepted 16 October 2013 Available online 23 October 2013
ZnO crystals with twinned structures were prepared by using a hydrothermal reaction. N,N′-Dimethylethylenediamine and sodium 1-heptanesulfonate were used as the hydroxide ion generator and the morphology controller respectively. As the concentration of sodium 1-heptanesulfonate increases, the morphology of the ZnO crystals varies from thin hexagonal rods to thick hexagonal plates, and the ratio of the areas of the (001) polar and (110) nonpolar planes increases, as determined from XRD data. Further, the antibacterial activity of the ZnO crystals appears to increase with increases in the ratio of the areas of their (001) polar and (110) nonpolar planes, which provides insight into the morphology dependence of the antibacterial activity of ZnO. & 2013 Elsevier B.V. All rights reserved.
Keywords: Crystal growth Microstructure Morphology Antibacterial activity ZnO
1. Introduction The morphology-controlled synthesis of inorganic oxides has recently been extensively investigated because their optical, catalytic, and antibacterial properties depend on their morphologies, i.e. on their surface atomic arrangements [1,2]. The specific atomic arrangement on the surface can be selected by fine tuning the morphology of the inorganic oxide. Morphology-controlled syntheses of inorganic oxides can thus be developed by simply adjusting the synthetic conditions and examining the resulting morphologies. Zinc oxide (ZnO) is an important inorganic oxide that has been widely used in solar cells, gas sensors, and photocatalysts [3,4]. Moreover, nanograined ZnO doped with magnetic atoms have been extensively investigated due to their high temperature ferromagnetism [5–7]. Since ZnO has a hexagonal wurtzite crystal structure, the hexagonal prisms or plates of ZnO have (001) polar planes and (110) nonpolar planes that are parallel and perpendicular to the c axis respectively [8,9]. The main focus of the research into the morphology-dependent properties of ZnO has been its photocatalytic activity. The (001) polar planes of ZnO have higher photocatalytic activity than (110) nonpolar planes [10]. The morphology dependence of the antibacterial activities of ZnO has also been investigated. Flower-like ZnO with a highly exposed (001) polar plane has a higher antibacterial activity than ZnO spherical aggregates, fusiformshaped microrods, and rod-like and sphere-like crystals [11,12].
However, it has been difficult to evaluate the antibacterial activities of the (001) polar and (110) nonpolar planes of ZnO because ZnO products have highly diverse morphologies. Therefore, fine morphological tuning is required to determine the morphology dependence of the antibacterial activity of ZnO, and in particular the antibacterial activities of the (001) polar and (110) nonpolar planes. ZnO crystals with twinned structures are commonly obtained by utilizing the characteristic reactions of protonated amines with the (001) and (001) polar planes [13]. Twinned dumbbelllike ZnO has been prepared with a simple solution method by using hexamethylenetetramine [14]. Twinned hourglass-like ZnO crystals were prepared with a solvothermal method in the presence of zinc acetylacetonate in toluene [15]. Twinned hexagonal prism ZnO crystals were prepared by using a microwaveassisted method in mixed solvents consisting of water and ethylene glycol [16]. However, relatively little is known about the morphology dependence of the antibacterial activities of twinned ZnO structures. This paper presents a simple hydrothermal method for the preparation of twinned ZnO structures from ZnCl2 and N,N′-dimethylethylenediamine (DMEDA) in the presence of sodium 1-heptanesulfonate (C7H15SO3Na). Further, we show that the concentration of C7H15SO3Na is a crucial factor in the control of the morphologies and the aspect ratios of the ZnO crystals.
2. Experimental n
Corresponding author. Tel.: þ 82 31 80053154; fax: þ 82 31 80053148. E-mail address: [email protected] (Y.-D. Huh).
0167-577X/$ - see front matter & 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.matlet.2013.10.056
ZnCl2 (98%, Aldrich), N,N′-dimethylethylenediamine (DMEDA, 95%, Aldrich), and sodium 1-heptanesulfonate (C7H15SO3Na, 98%, TCI)
206
D.-H. Jin et al. / Materials Letters 115 (2014) 205–207
were used as received. In a typical synthesis of ZnO, 0.345 mL of DMEDA was added to 30 mL of a 0.10 M ZnCl2 solution. The solution was then added to 30 mL of a 0.05 M C7H15SO3Na solution. The final mixed solution was transferred to a 100 mL Teflon-lined autoclave and heated at 140 1C for 24 h. The product was centrifuged, washed several times with water and dried in an oven at 60 1C for 24 h. Other concentrations (0.30 M, 0.60 M, and 1.0 M) of C7H15SO3Na were also used to obtain various morphologies of ZnO, with the remaining conditions held constant. The structures and morphologies of the ZnO products were characterized by using powder X-ray diffraction (XRD, PANalytical, X'Pert-PRO MPD) and scanning electron microscopy (SEM, Hitachi S-4300) respectively. The antibacterial activities of the ZnO products were measured with a previously reported method [4]. 100 mL of Escherichia coli overnight culture was aliquoted evenly into 5 mL Luria-Bertani (LB) media containing 100 mg/mL of each ZnO product. The aliquoted E. coli cultures were then incubated in a 37 1C shaking incubator for the indicated periods of time. The optical densities were measured at 600 nm by using a UV–vis spectrophotometer (Perkin-Elmer Lambda 25).
shown in Fig. 1(c), with an estimated aspect ratio of 1.7. When the concentration of C7H15SO3Na was finally increased to 1.0 M, the ZnO crystals were thick twinned hexagonal plates, as shown in Fig. 1(d). This morphology has a significantly decreased aspect ratio, 0.9. The twinned morphologies of the ZnO products evolve from thin hexagonal rods with bipyramidal ends to thick hexagonal plates with increases in the C7H15SO3Na concentration. Fig. 2 shows the XRD patterns and Miller indices of the ZnO crystals obtained in the presence of various concentrations of C7H15SO3Na. All the peaks in Fig. 2 are in good agreement with the reported data for hexagonal ZnO (JCPDS 36-1451, a¼ 0.3249 nm and c ¼0.5206 nm). No other peaks were detected, so we conclude that this method yields ZnO free from impurities. Hydroxide ions (OH ) and protonated DMEDA, DMEDAH þ , are produced by the addition of DMEDA. The zinc ion (Zn2 þ ) reacts with OH to form ZnO22 ion, and finally ZnO is formed. The C7H15SO3 ion acts as a morphology-directing surfactant and so competes with ZnO22 ions in the formation of ZnO product. The possible chemical reactions producing ZnO are as follows: DMEDA (l)þ H2O⇄DMEDAH þ (aq)þOH (aq)
(1)
Zn2 þ (aq) þ4OH (aq)⇄ZnO22 (aq) þ2H2O
(2)
3. Results and discussion
ZnO22 (aq) þH2O⇄ZnO (s) þ2OH (aq)
(3)
Fig. 1 shows SEM images of the ZnO products obtained with the hydrothermal method and various concentrations of C7H15SO3Na. For [C7H15SO3Na]¼0.05 M, twinned hexagonal rod-like ZnO with bipyramidal ends and an average length of 10.6 mm and an average diameter of 1.0 mm were formed with an aspect ratio of 10.6, as shown in Fig. 1(a). A boundary is evident in the middle of each pair of linked hexagonal rods. Both ends of each rod have pyramidal shapes. When the concentration of C7H15SO3Na was increased to 0.30 M, shorter twinned hexagonal ZnO crystals were obtained, as shown in Fig. 1(b). The ends of the hexagonal rods are flattened, so twinned hexagonal prisms of ZnO have formed. The average length and diameter of the twinned hexagonal prisms are 6.6 mm and 1.4 mm respectively, with an estimated aspect ratio of 4.7. When the concentration of C7H15SO3Na was increased to 0.60 M, shorter twinned hexagonal prism ZnO crystals were formed, as
Fig. 3 shows the variation in the ratio of the XRD intensities of (002) and (110) with the C7H15SO3Na concentration. As the C7H15SO3Na concentration increases, the ratio of the intensities of (002) and (110) of the four ZnO products increases from 0.7 to 1.3, which suggests that the proportion of the (002) polar plane increases with respect to that of the (110) nonpolar plane of the hexagonal prisms. The characteristics of (001) planes resembles those of (002) planes. The absorption of C7H15SO3 ions onto the (001) polar surface prevents the reaction of ZnO22 ions. Thus, the length of the ZnO hexagonal prisms is shortened by the presence of the C7H15SO3 ions. Therefore, the ratio of the areas of the (001) polar plane and the (110) nonpolar plane of the ZnO products can with this method be simply tuned by varying the concentration of C7H15SO3Na, obtaining morphologies from thin hexagonal rods to thick hexagonal plates.
Fig. 1. SEM images of the ZnO products prepared with various concentrations of C7H15SO3Na: (a) 0.05 M, (b) 0.30 M, (c) 0.60 M, and (d) 1.0 M.
D.-H. Jin et al. / Materials Letters 115 (2014) 205–207
207
Fig. 4 shows the growth rates of E. coli in the absence or presence of ZnO products prepared with various concentrations of C7H15SO3Na. The incubation time for growth to 50% is known as the half maximal growth time. The half maximal growth times were 4.1, 5.5, 6.6, 7.1, and 9.2 h for E. coli cultures in the absence of ZnO and in the presence of ZnO products prepared with 0.05 M, 0.30 M, 0.60 M, and 1.0 M C7H15SO3Na, respectively. Thus the antibacterial activity of ZnO depends on its morphology. Thick twinned hexagonal prisms of ZnO have the highest antibacterial activity. Therefore, the (001) polar plane of ZnO plays an important role in its antibacterial activity against E. coli. 4. Conclusions
Fig. 2. XRD patterns for the ZnO products prepared with various concentrations of C7H15SO3Na: (a) 0.05 M, (b) 0.30 M, (c) 0.60 M, and (d) 1.0 M.
Various twinned morphologies of ZnO were prepared with a hydrothermal reaction by varying the C7H15SO3Na concentration. As the C7H15SO3Na concentration increases, the twinned ZnO structures evolve from thin hexagonal rods with bipyramidal ends to thick hexagonal plates, and the ratio of the areas of the (001) polar plane and the (110) nonpolar plane of ZnO also increases. The antibacterial activities also vary with the morphology of ZnO, which suggests that the polar properties of the (001) plane play key roles in the antibacterial activity of these ZnO crystals. Acknowledgment This study was supported by the Basic Science Research Program through the National Research Foundation of Korea funded by the Ministry of Education, Science and Technology (2010–0007492). References [1] [2] [3] [4] [5] [6]
Fig. 3. Ratio of the XRD intensities of (002) and (110) as a function of the C7H15SO3Na concentration.
[7] [8] [9] [10] [11] [12] [13] [14] [15] [16]
Fig. 4. E. coli growth rates in the absence (triangles) or presence of ZnO products prepared with various concentrations of C7H15SO3Na: (a) 0.05 M (inverted triangles), (b) 0.30 M (circles), (c) 0.60 M (stars), and (d) 1.0 M (diamonds).
Qi L. Coord Chem Rev 2010;254:1054–71. He M, Jiu H, Liu Y, Tian Y, Li D, Sun Y, et al. Mater Lett 2013;92:154–6. Lee YJ, Kim S, Park SH, Park H, Huh YD. Mater Lett 2011;65:818–20. Chang J, Ahmed R, Wang H, Liu H, Li R, Wang P, et al. J Phys Chem C 2013;117:13836–44. Dietl T, Ohno H, Matsukura F, Cibert J, Ferrand D. Science 2000;287:1019–22. Straumal BB, Mazilkin AA, Protasova SG, Straumal PB, Myatiev AA, Schütz G, et al. Philos Mag 2013;93:1371–83. Straumal BB, Protasova SG, Mazilkin AA, Schütz G, Goering E, Baretzky B, et al. JETP Lett 2013;97:367–77. Jang ES, Won JH, Hwang SJ, Choy JH. Adv Mater 2006;18:3309–12. Ge MY, Wu HO, Niu L, Liu JF, Chen SY, Shen PY, et al. J Cryst Growth 2007;305:162–6. Mclaren A, Valdes-Solis T, Li G, Tsang SC. J Am Chem Soc 2009;131:12540–1. Tong GX, Du FF, Liang Y, Hu Q, Wu RN, Guan JG, et al. J Mater Chem B 2013;1:454–63. Talebian N, Amininezhad SM, Doudi M. J Photochem Photobiol B 2013;120:66–73. Wang Y, Hou Z, Guo H, Shen L, Wang G, Cui F, et al. Mater Lett 2013;91:107–10. Yu Q, Yu C, Yang H, Fu W, Chang L, Xu J, et al. Inorg Chem 2007;46:6204–10. Xu L, Hu YL, Pelligra C, Chen CH, Jin L, Huang H, et al. Chem Mater 2009;21:2875–85. Zhang L, Zhu YJ. Appl Phys A 2009;97:847–52.