Longitudinal unzipping of carbon nanotubes to form graphene nanoribbons
Summary (1 min read)
Summary
- Graphene, or single-layered graphite, with its high crystallinity and interesting semimetal electronic properties, has emerged as an exciting two-dimensional material showing great promise for the fabrication of nanoscale devices 1-3 .
- Thin, elongated strips of graphene that possess straight edges, termed graphene ribbons, gradually transform from semiconductors to semimetals as their width increases [4] [5] [6] [7] , and represent a particularly versatile variety of graphene.
- Several lithographic 7,8 , chemical [9] [10] [11] and synthetic 12 procedures are known to produce microscopic samples of graphene nanoribbons, and one chemical vapour deposition process 13 has successfully produced macroscopic quantities of nanoribbons at 950 6C.
- Here the authors describe a simple solution-based oxidative process.
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Frequently Asked Questions (15)
Q2. What is the versatile variety of graphene?
elongated strips of graphene that possess straight edges, termed graphene ribbons, gradually transform from semiconductors to semimetals as their width increases4–7, and represent a particularly versatile variety of graphene.
Q3. What is the promising material for nanoscale devices?
or single-layered graphite, with its high crystallinity and interesting semimetal electronic properties, has emerged as an exciting two-dimensional material showing great promise for the fabrication of nanoscale devices1–3.
Q4. What is the advantage of the preparative route described here?
Although the preparative route described here can have the advantage of producing accessible nanoribbons on a large scale, these unzipping-derived nanoribbons, with their residual oxidizeddefect sites, have electronic characteristics inferior to those of wide, mechanically peeled sheets of graphene2,30.
Q5. What are the p-conjugated graphite and graphite oxide?
Both the nanoribbons and graphite oxide possess oxygen-containing functionalities such as carbonyls, carboxyls and hydroxyls23 that have been shown to exist at the edges and the surface24.
Q6. What is the effect of the oxidation on the carbon nanotubes?
relief of the bond-angle strain when the nanotube opens to the graphene ribbon (5, Fig. 1b) slows further dione formation and cutting20.
Q7. What is the effect of the oxidized nanoribbons on the field effect?
bilayers of these reduced graphene nanoribbons have field-effect properties with a minimum conductivity at zero gate voltage, which is as expected for undoped field-effect devices made from exfoliated graphene sheets and is superior to CCGs (Fig. 4c, d)2,30.
Q8. What is the TGA weight loss of the reduced nanoribbons?
The TGA weight loss of the reduced nanoribbons was ,33% less than that of the oxidized starting material, which also indicates that fewer oxygen-containing functionalities are present on the nanoribbon surface (see Supplementary Fig. 4d for TGA curves).
Q9. Why is the edge curling attributed to the oxidized nanoribbons?
This is due, in part, to edge curling, and could be further attributed to the extensive edge oxidation; this may be removed only upon treatment at $2,000 uC, which would result in reconstruction and modified electronic properties.
Q10. What is the degree of openness of the MWCNTs?
It is evident from TEM images (Fig. 2a–e) that the walls of the MWCNTs open to a higher degree as the level of oxidation increases, with less MWCNT inner tube remaining in successive iterations.
Q11. What is the atomic concentration of oxygen in the nanoribbons?
In addition, the XPS-determined atomic concentration of oxygen (complete table found in Supplementary Fig. 4b) decreases from 42% to 16% upon reduction, but is still higher than the oxygen content of MWCNTs (2.1%), owing, in large part, to the edge carboxylic acid moieties.
Q12. What is the simplest way to make graphene ribbons?
The opening of the nanotubes appears to occur along a line, similar to the ‘unzipping’ of graphite oxide18,19, affording straightedged ribbons.
Q13. what is the edge state of graphene ribbons?
5. Nakada, K., Fujita, M., Dresselhaus, G. & Dresselhaus, M. S. Edge state in graphene ribbons: nanometer size effect and edge shape dependence.
Q14. What are the XPS signals of the oxidized and reduced nanoribbons?
In the XPS carbon 1s spectra of the oxidized and reduced nanoribbons (Fig. 3d), the signals at 286 eV and 287 eV correspond to C–O and C5O, respectively.
Q15. What is the effect of juxtaposition of the buttressing ketones?
Juxtaposition of the buttressing ketones distorts the b,c-alkenes (red in 3), making them more prone to the next attack by permanganate.