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Revelation of graphene-Au for direct write deposition and characterization.

Bhandari S, Deepa M, Joshi AG, Saxena AP, Srivastava AK - Nanoscale Res Lett (2011)

Bottom Line: Graphene nanosheets were prepared using a modified Hummer's method, and Au-graphene nanocomposites were fabricated by in situ reduction of a gold salt.Scanning helium ion microscopy (HIM) technique was employed to demonstrate direct write deposition on graphene by lettering with gaps down to 7 nm within the chamber of the microscope.Bare graphene and graphene-gold nanocomposites were further characterized in terms of their composition and optical and electrical properties.

View Article: PubMed Central - HTML - PubMed

Affiliation: National Physical Laboratory, Council of Scientific and Industrial Research, Dr, K,S, Krishnan Road, New Delhi, 110 012, India. aks@nplindia.ernet.in.

ABSTRACT
Graphene nanosheets were prepared using a modified Hummer's method, and Au-graphene nanocomposites were fabricated by in situ reduction of a gold salt. The as-produced graphene was characterized by X-ray photoelectron spectroscopy, ultraviolet-visible spectroscopy, scanning electron microscopy, and high-resolution transmission electron microscopy (HR-TEM). In particular, the HR-TEM demonstrated the layered crystallites of graphene with fringe spacing of about 0.32 nm in individual sheets and the ultrafine facetted structure of about 20 to 50 nm of Au particles in graphene composite. Scanning helium ion microscopy (HIM) technique was employed to demonstrate direct write deposition on graphene by lettering with gaps down to 7 nm within the chamber of the microscope. Bare graphene and graphene-gold nanocomposites were further characterized in terms of their composition and optical and electrical properties.

No MeSH data available.


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HR-TEM micrographs of acid-functionalized grapheme. (a) Sheets with wrinkle contrast, (b) different layers of graphene and (c, d) lattice scale fringes of graphene resolved from two different regions as marked A and B in (b).
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Figure 4: HR-TEM micrographs of acid-functionalized grapheme. (a) Sheets with wrinkle contrast, (b) different layers of graphene and (c, d) lattice scale fringes of graphene resolved from two different regions as marked A and B in (b).

Mentions: Crumpled, folded, layers of bare graphene can be seen in the SEM image shown in Figure 3a. The SEM image of bare graphene displayed in Figure 3b shows stacks of graphene layers, bound by van der Waals forces. The thick edges of the sheets therein (inset of Figure 3b) reveal that the layers are atop each other with a thickness of about 0.45 µm. HR-TEM was employed to study the graphene and Au-graphene nanocomposites to investigate the microstructure of graphene as well as the size, shape, and distribution of Au nanoparticles in the graphene matrix (Figure 4). A conventional folded microstructure of thin graphene sheets was observed throughout the specimen (Figure 4a). The thickness of these sheets varies between 1 to 2 nm, whereas the size of these sheets is on an average between 500 nm to 1 µm (Figure 4a). A significant observation was made by resolving the graphene sheets at lattice scale. The magnified regions, marked as A and B (as indicated in Figure 4b), are displayed in Figure 4c,d, respectively. Figure 4c exhibits a cluster of graphene sheets with well-resolved fringes showing the crystalline nature of individual sheets at lattice scale, whereas Figure 4d further reveals the lattice fringe spacing of about 0.34 nm from a single sheet of a graphene. A good distribution of Au nanoparticles in the matrix phase of graphene has been delineated in the graphene-Au composite materials with a good interface between the matrix and the nanoparticle. An inset in Figure 4a exhibits the presence of carbon decorated with ultrafine dispersion of Au nanoparticle in a graphene-Au nanocomposite. Moreover, a faceted morphology of Au nanoparticle with the edges of about 30 nm clearly shows that the nanoparticle of Au is crystalline with preferred orientation (inset in Figure 4a). Since Au is characterized by a face-centered cubic crystal structure, the hexagonal-shaped particles are presumably due to the preferred growth along the 111 planes of a cubic crystal. The 111 planes of Au with graphene of c-axis growth of carbon lattice also justify a distinct orientation relationship and therefore a crystallographic compatibility between the carbon as matrix and the Au as second phase.


Revelation of graphene-Au for direct write deposition and characterization.

Bhandari S, Deepa M, Joshi AG, Saxena AP, Srivastava AK - Nanoscale Res Lett (2011)

HR-TEM micrographs of acid-functionalized grapheme. (a) Sheets with wrinkle contrast, (b) different layers of graphene and (c, d) lattice scale fringes of graphene resolved from two different regions as marked A and B in (b).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3211841&req=5

Figure 4: HR-TEM micrographs of acid-functionalized grapheme. (a) Sheets with wrinkle contrast, (b) different layers of graphene and (c, d) lattice scale fringes of graphene resolved from two different regions as marked A and B in (b).
Mentions: Crumpled, folded, layers of bare graphene can be seen in the SEM image shown in Figure 3a. The SEM image of bare graphene displayed in Figure 3b shows stacks of graphene layers, bound by van der Waals forces. The thick edges of the sheets therein (inset of Figure 3b) reveal that the layers are atop each other with a thickness of about 0.45 µm. HR-TEM was employed to study the graphene and Au-graphene nanocomposites to investigate the microstructure of graphene as well as the size, shape, and distribution of Au nanoparticles in the graphene matrix (Figure 4). A conventional folded microstructure of thin graphene sheets was observed throughout the specimen (Figure 4a). The thickness of these sheets varies between 1 to 2 nm, whereas the size of these sheets is on an average between 500 nm to 1 µm (Figure 4a). A significant observation was made by resolving the graphene sheets at lattice scale. The magnified regions, marked as A and B (as indicated in Figure 4b), are displayed in Figure 4c,d, respectively. Figure 4c exhibits a cluster of graphene sheets with well-resolved fringes showing the crystalline nature of individual sheets at lattice scale, whereas Figure 4d further reveals the lattice fringe spacing of about 0.34 nm from a single sheet of a graphene. A good distribution of Au nanoparticles in the matrix phase of graphene has been delineated in the graphene-Au composite materials with a good interface between the matrix and the nanoparticle. An inset in Figure 4a exhibits the presence of carbon decorated with ultrafine dispersion of Au nanoparticle in a graphene-Au nanocomposite. Moreover, a faceted morphology of Au nanoparticle with the edges of about 30 nm clearly shows that the nanoparticle of Au is crystalline with preferred orientation (inset in Figure 4a). Since Au is characterized by a face-centered cubic crystal structure, the hexagonal-shaped particles are presumably due to the preferred growth along the 111 planes of a cubic crystal. The 111 planes of Au with graphene of c-axis growth of carbon lattice also justify a distinct orientation relationship and therefore a crystallographic compatibility between the carbon as matrix and the Au as second phase.

Bottom Line: Graphene nanosheets were prepared using a modified Hummer's method, and Au-graphene nanocomposites were fabricated by in situ reduction of a gold salt.Scanning helium ion microscopy (HIM) technique was employed to demonstrate direct write deposition on graphene by lettering with gaps down to 7 nm within the chamber of the microscope.Bare graphene and graphene-gold nanocomposites were further characterized in terms of their composition and optical and electrical properties.

View Article: PubMed Central - HTML - PubMed

Affiliation: National Physical Laboratory, Council of Scientific and Industrial Research, Dr, K,S, Krishnan Road, New Delhi, 110 012, India. aks@nplindia.ernet.in.

ABSTRACT
Graphene nanosheets were prepared using a modified Hummer's method, and Au-graphene nanocomposites were fabricated by in situ reduction of a gold salt. The as-produced graphene was characterized by X-ray photoelectron spectroscopy, ultraviolet-visible spectroscopy, scanning electron microscopy, and high-resolution transmission electron microscopy (HR-TEM). In particular, the HR-TEM demonstrated the layered crystallites of graphene with fringe spacing of about 0.32 nm in individual sheets and the ultrafine facetted structure of about 20 to 50 nm of Au particles in graphene composite. Scanning helium ion microscopy (HIM) technique was employed to demonstrate direct write deposition on graphene by lettering with gaps down to 7 nm within the chamber of the microscope. Bare graphene and graphene-gold nanocomposites were further characterized in terms of their composition and optical and electrical properties.

No MeSH data available.


Related in: MedlinePlus