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Growth of carbon nanowalls at atmospheric pressure for one-step gas sensor fabrication.

Yu K, Bo Z, Lu G, Mao S, Cui S, Zhu Y, Chen X, Ruoff RS, Chen J - Nanoscale Res Lett (2011)

Bottom Line: However, Raman and X-ray photoelectron spectroscopies confirmed that most of the oxygen groups could be removed by thermal annealing.A gas-sensing device based on such CNWs was fabricated on metal electrodes through direct growth.The sensor responded to relatively low concentrations of NO2 (g) and NH3 (g), thus suggesting high-quality CNWs that are useful for room temperature gas sensors.PACS: Graphene (81.05.ue), Chemical vapor deposition (81.15.Gh), Gas sensors (07.07.Df), Atmospheric pressure (92.60.hv).

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Mechanical Engineering, University of Wisconsin-Milwaukee, Milwaukee, WI 53211, USA. jhchen@uwm.edu.

ABSTRACT
Carbon nanowalls (CNWs), two-dimensional "graphitic" platelets that are typically oriented vertically on a substrate, can exhibit similar properties as graphene. Growth of CNWs reported to date was exclusively carried out at a low pressure. Here, we report on the synthesis of CNWs at atmosphere pressure using "direct current plasma-enhanced chemical vapor deposition" by taking advantage of the high electric field generated in a pin-plate dc glow discharge. CNWs were grown on silicon, stainless steel, and copper substrates without deliberate introduction of catalysts. The as-grown CNW material was mainly mono- and few-layer graphene having patches of O-containing functional groups. However, Raman and X-ray photoelectron spectroscopies confirmed that most of the oxygen groups could be removed by thermal annealing. A gas-sensing device based on such CNWs was fabricated on metal electrodes through direct growth. The sensor responded to relatively low concentrations of NO2 (g) and NH3 (g), thus suggesting high-quality CNWs that are useful for room temperature gas sensors.PACS: Graphene (81.05.ue), Chemical vapor deposition (81.15.Gh), Gas sensors (07.07.Df), Atmospheric pressure (92.60.hv).

No MeSH data available.


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TEM characterization of CNWs. (a) A CNW sheet supported on a Cu grid. Electron diffraction from the CNW is shown as an inset. (b) The areas of a CNW with different thicknesses and wrinkles. (c) and (d) HRTEM images showing the edges of CNW film consisting of one, and five graphene layers, respectively. (d corresponds to the area defined by the white box in b). (e) HRTEM iamge of a CNW sheet with two well-crytallined regions (arrowed). The diffractogram (the inset) is from the red-squared region in (e). (f) A filtered image of the squared region in (e). (g) The intensity profile along the red dashed line in (f).
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Figure 4: TEM characterization of CNWs. (a) A CNW sheet supported on a Cu grid. Electron diffraction from the CNW is shown as an inset. (b) The areas of a CNW with different thicknesses and wrinkles. (c) and (d) HRTEM images showing the edges of CNW film consisting of one, and five graphene layers, respectively. (d corresponds to the area defined by the white box in b). (e) HRTEM iamge of a CNW sheet with two well-crytallined regions (arrowed). The diffractogram (the inset) is from the red-squared region in (e). (f) A filtered image of the squared region in (e). (g) The intensity profile along the red dashed line in (f).

Mentions: TEM images of the product CNWs were shown in Figure 4. Two low-magnification TEM images are shown as Figure 4a and 4b. The inset in Figure 4a is a SAD pattern of the CNW sample, which displays a hexagonal pattern confirming the threefold symmetry of the arrangement of carbon atoms. Well-defined diffraction spots (instead of ring patterns) were observed for most CNWs, while ring patterns were observed seldomly, indicating the mostly few-layer structure and a high degree of crystallinity of the resulting CNWs. HRTEM examination of the samples confirms that the CNW sheets consist of only a few graphene layers (typically one to five layers, Figure 4c,4d). The edges of the suspended CNWs often fold back, allowing for a cross-sectional view of the graphene [48,52]. By observing these edges through HRTEM images, the number of layers at multiple locations on the graphene can be measured (Figure 4c,4d). The estimated interlayer spacing is about 3.50 Å, which is a little larger than the d-spacing of graphite (3.36 Å). The small amount of oxygen-containing functional groups might be the main reason for this difference [44].


Growth of carbon nanowalls at atmospheric pressure for one-step gas sensor fabrication.

Yu K, Bo Z, Lu G, Mao S, Cui S, Zhu Y, Chen X, Ruoff RS, Chen J - Nanoscale Res Lett (2011)

TEM characterization of CNWs. (a) A CNW sheet supported on a Cu grid. Electron diffraction from the CNW is shown as an inset. (b) The areas of a CNW with different thicknesses and wrinkles. (c) and (d) HRTEM images showing the edges of CNW film consisting of one, and five graphene layers, respectively. (d corresponds to the area defined by the white box in b). (e) HRTEM iamge of a CNW sheet with two well-crytallined regions (arrowed). The diffractogram (the inset) is from the red-squared region in (e). (f) A filtered image of the squared region in (e). (g) The intensity profile along the red dashed line in (f).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3211258&req=5

Figure 4: TEM characterization of CNWs. (a) A CNW sheet supported on a Cu grid. Electron diffraction from the CNW is shown as an inset. (b) The areas of a CNW with different thicknesses and wrinkles. (c) and (d) HRTEM images showing the edges of CNW film consisting of one, and five graphene layers, respectively. (d corresponds to the area defined by the white box in b). (e) HRTEM iamge of a CNW sheet with two well-crytallined regions (arrowed). The diffractogram (the inset) is from the red-squared region in (e). (f) A filtered image of the squared region in (e). (g) The intensity profile along the red dashed line in (f).
Mentions: TEM images of the product CNWs were shown in Figure 4. Two low-magnification TEM images are shown as Figure 4a and 4b. The inset in Figure 4a is a SAD pattern of the CNW sample, which displays a hexagonal pattern confirming the threefold symmetry of the arrangement of carbon atoms. Well-defined diffraction spots (instead of ring patterns) were observed for most CNWs, while ring patterns were observed seldomly, indicating the mostly few-layer structure and a high degree of crystallinity of the resulting CNWs. HRTEM examination of the samples confirms that the CNW sheets consist of only a few graphene layers (typically one to five layers, Figure 4c,4d). The edges of the suspended CNWs often fold back, allowing for a cross-sectional view of the graphene [48,52]. By observing these edges through HRTEM images, the number of layers at multiple locations on the graphene can be measured (Figure 4c,4d). The estimated interlayer spacing is about 3.50 Å, which is a little larger than the d-spacing of graphite (3.36 Å). The small amount of oxygen-containing functional groups might be the main reason for this difference [44].

Bottom Line: However, Raman and X-ray photoelectron spectroscopies confirmed that most of the oxygen groups could be removed by thermal annealing.A gas-sensing device based on such CNWs was fabricated on metal electrodes through direct growth.The sensor responded to relatively low concentrations of NO2 (g) and NH3 (g), thus suggesting high-quality CNWs that are useful for room temperature gas sensors.PACS: Graphene (81.05.ue), Chemical vapor deposition (81.15.Gh), Gas sensors (07.07.Df), Atmospheric pressure (92.60.hv).

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Mechanical Engineering, University of Wisconsin-Milwaukee, Milwaukee, WI 53211, USA. jhchen@uwm.edu.

ABSTRACT
Carbon nanowalls (CNWs), two-dimensional "graphitic" platelets that are typically oriented vertically on a substrate, can exhibit similar properties as graphene. Growth of CNWs reported to date was exclusively carried out at a low pressure. Here, we report on the synthesis of CNWs at atmosphere pressure using "direct current plasma-enhanced chemical vapor deposition" by taking advantage of the high electric field generated in a pin-plate dc glow discharge. CNWs were grown on silicon, stainless steel, and copper substrates without deliberate introduction of catalysts. The as-grown CNW material was mainly mono- and few-layer graphene having patches of O-containing functional groups. However, Raman and X-ray photoelectron spectroscopies confirmed that most of the oxygen groups could be removed by thermal annealing. A gas-sensing device based on such CNWs was fabricated on metal electrodes through direct growth. The sensor responded to relatively low concentrations of NO2 (g) and NH3 (g), thus suggesting high-quality CNWs that are useful for room temperature gas sensors.PACS: Graphene (81.05.ue), Chemical vapor deposition (81.15.Gh), Gas sensors (07.07.Df), Atmospheric pressure (92.60.hv).

No MeSH data available.


Related in: MedlinePlus