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Graphene oxide-modified ZnO particles: synthesis, characterization, and antibacterial properties.

Zhong L, Yun K - Int J Nanomedicine (2015)

Bottom Line: The morphology of the graphene oxide sheets and ZnO particles was confirmed with field emission scanning electron microscopy and biological atomic force microscopy.Enhanced electrochemical properties were detected with cyclic voltammetry, with a redox peak of the composites at 0.025 mV.After further study of the antibacterial mechanism, we concluded that a vast number of reactive oxygen species formed on the surface of composites, improving antibacterial properties.

View Article: PubMed Central - PubMed

Affiliation: Department of Bionanotechnology, Gachon University, Gyeonggi-do, Republic of Korea.

ABSTRACT
Nanosized ZnO particles with diameters of 15 nm were prepared with a solution precipitation method at low cost and high yield. The synthesis of the particles was functionalized by the organic solvent dimethylformamide, and the particles were covalently bonded to the surface of graphene oxide. The morphology of the graphene oxide sheets and ZnO particles was confirmed with field emission scanning electron microscopy and biological atomic force microscopy. Fourier transform infrared spectroscopy and X-ray diffraction were used to analyze the physical and chemical properties of the ZnO/graphene oxide composites that differed from those of the individual components. Enhanced electrochemical properties were detected with cyclic voltammetry, with a redox peak of the composites at 0.025 mV. Excellent antibacterial activity of ZnO/graphene oxide composites was observed with a microdilution method in which minimum inhibitory concentrations of 6.25 µg/mL for Escherichia coli and Salmonella typhimurium, 12.5 µg/mL for Bacillus subtilis, and 25 µg/mL for Enterococcus faecalis. After further study of the antibacterial mechanism, we concluded that a vast number of reactive oxygen species formed on the surface of composites, improving antibacterial properties.

No MeSH data available.


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FE-SEM images and EDX result.Notes: (A) ZnO particles are round in shape and disperse on the substrate; (B) a big ZnO particle contains some small nanoparticles; (C) graphene oxide has grooves and wrinkles on the edges; (D) ZnO particles were anchored onto the surface of graphene oxide via the covalent bonds; (E) EDX image clearly show that the sample has pure ZnO phases.Abbreviations: FE-SEM, field emission scanning electron microscopy; EDX, energy dispersive X-ray spectroscopy; ZnO, zinc oxide.
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f3-ijn-10-079: FE-SEM images and EDX result.Notes: (A) ZnO particles are round in shape and disperse on the substrate; (B) a big ZnO particle contains some small nanoparticles; (C) graphene oxide has grooves and wrinkles on the edges; (D) ZnO particles were anchored onto the surface of graphene oxide via the covalent bonds; (E) EDX image clearly show that the sample has pure ZnO phases.Abbreviations: FE-SEM, field emission scanning electron microscopy; EDX, energy dispersive X-ray spectroscopy; ZnO, zinc oxide.

Mentions: Alkaline solution played a key role in this study because Na+ is attracted to the OH− around the ZnO core and forms a virtual capping layer to inhibit particle growth.33 As shown in Figure 3A, ZnO particleŝ170 nm in size were uniformly dispersed in the FE-SEM images. The high-magnification FE-SEM image in Figure 3B shows that nanosized ZnO particles assemble to form a round particle. We oxidized graphite to manufacture graphene oxide and exfoliated the graphene oxide monolayer via ultrasonication. Figure 3C shows that the edges of the transparent graphene oxide sheets tended to crimp, and many wrinkles were observed across all of the graphene oxide sheets. Generally, graphene oxide sheets contain unique chemically reactive groups such as carboxyl, hydroxyl, and epoxy groups on their basal planes for covalent reactions.34 The highly disordered arrangement of the covalently bonded ZnO particles on the graphene oxide sheets is shown in Figure 3D. We detected weight and atomic ratio of C, O, Zn elements of Figure 3D by energy dispersive X-ray spectroscopy. Except coating elements Pt and substrate component Si, no other elements were detected from ZnO/graphene oxide composites. The morphology of the ZnO particles demonstrated on Bio-AFM images is consistent with the FE-SEM micrographs. Figure 4A shows round ZnO particles uniformly dispersed on the substrate. The average size of the ZnO particles is 170 nm, as detected by a Malvern Zetasizer Range. Figure 4B shows the wrinkles and thin grooves on the surface of graphene oxide. The wavy features are much more apparent in the Bio-AFM three-dimensional image. Figure 4C shows unordered ZnO particles anchored on the surface of the graphene oxide sheets. Three-dimensional images show clear morphology in Figure 4D–F.


Graphene oxide-modified ZnO particles: synthesis, characterization, and antibacterial properties.

Zhong L, Yun K - Int J Nanomedicine (2015)

FE-SEM images and EDX result.Notes: (A) ZnO particles are round in shape and disperse on the substrate; (B) a big ZnO particle contains some small nanoparticles; (C) graphene oxide has grooves and wrinkles on the edges; (D) ZnO particles were anchored onto the surface of graphene oxide via the covalent bonds; (E) EDX image clearly show that the sample has pure ZnO phases.Abbreviations: FE-SEM, field emission scanning electron microscopy; EDX, energy dispersive X-ray spectroscopy; ZnO, zinc oxide.
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f3-ijn-10-079: FE-SEM images and EDX result.Notes: (A) ZnO particles are round in shape and disperse on the substrate; (B) a big ZnO particle contains some small nanoparticles; (C) graphene oxide has grooves and wrinkles on the edges; (D) ZnO particles were anchored onto the surface of graphene oxide via the covalent bonds; (E) EDX image clearly show that the sample has pure ZnO phases.Abbreviations: FE-SEM, field emission scanning electron microscopy; EDX, energy dispersive X-ray spectroscopy; ZnO, zinc oxide.
Mentions: Alkaline solution played a key role in this study because Na+ is attracted to the OH− around the ZnO core and forms a virtual capping layer to inhibit particle growth.33 As shown in Figure 3A, ZnO particleŝ170 nm in size were uniformly dispersed in the FE-SEM images. The high-magnification FE-SEM image in Figure 3B shows that nanosized ZnO particles assemble to form a round particle. We oxidized graphite to manufacture graphene oxide and exfoliated the graphene oxide monolayer via ultrasonication. Figure 3C shows that the edges of the transparent graphene oxide sheets tended to crimp, and many wrinkles were observed across all of the graphene oxide sheets. Generally, graphene oxide sheets contain unique chemically reactive groups such as carboxyl, hydroxyl, and epoxy groups on their basal planes for covalent reactions.34 The highly disordered arrangement of the covalently bonded ZnO particles on the graphene oxide sheets is shown in Figure 3D. We detected weight and atomic ratio of C, O, Zn elements of Figure 3D by energy dispersive X-ray spectroscopy. Except coating elements Pt and substrate component Si, no other elements were detected from ZnO/graphene oxide composites. The morphology of the ZnO particles demonstrated on Bio-AFM images is consistent with the FE-SEM micrographs. Figure 4A shows round ZnO particles uniformly dispersed on the substrate. The average size of the ZnO particles is 170 nm, as detected by a Malvern Zetasizer Range. Figure 4B shows the wrinkles and thin grooves on the surface of graphene oxide. The wavy features are much more apparent in the Bio-AFM three-dimensional image. Figure 4C shows unordered ZnO particles anchored on the surface of the graphene oxide sheets. Three-dimensional images show clear morphology in Figure 4D–F.

Bottom Line: The morphology of the graphene oxide sheets and ZnO particles was confirmed with field emission scanning electron microscopy and biological atomic force microscopy.Enhanced electrochemical properties were detected with cyclic voltammetry, with a redox peak of the composites at 0.025 mV.After further study of the antibacterial mechanism, we concluded that a vast number of reactive oxygen species formed on the surface of composites, improving antibacterial properties.

View Article: PubMed Central - PubMed

Affiliation: Department of Bionanotechnology, Gachon University, Gyeonggi-do, Republic of Korea.

ABSTRACT
Nanosized ZnO particles with diameters of 15 nm were prepared with a solution precipitation method at low cost and high yield. The synthesis of the particles was functionalized by the organic solvent dimethylformamide, and the particles were covalently bonded to the surface of graphene oxide. The morphology of the graphene oxide sheets and ZnO particles was confirmed with field emission scanning electron microscopy and biological atomic force microscopy. Fourier transform infrared spectroscopy and X-ray diffraction were used to analyze the physical and chemical properties of the ZnO/graphene oxide composites that differed from those of the individual components. Enhanced electrochemical properties were detected with cyclic voltammetry, with a redox peak of the composites at 0.025 mV. Excellent antibacterial activity of ZnO/graphene oxide composites was observed with a microdilution method in which minimum inhibitory concentrations of 6.25 µg/mL for Escherichia coli and Salmonella typhimurium, 12.5 µg/mL for Bacillus subtilis, and 25 µg/mL for Enterococcus faecalis. After further study of the antibacterial mechanism, we concluded that a vast number of reactive oxygen species formed on the surface of composites, improving antibacterial properties.

No MeSH data available.


Related in: MedlinePlus