Geim AK, Novoselov KS: The rise of graphene. <>/Rotate 0/Type/Page>> J Phys Chem B 2007, 111: 7541–7549. > Among the various systems composed only of carbon 5atoms, graphene (a two-dimensional allotrope of carbon) presents a framework for understanding of the properties of all other carbon allotropes. 3-4, 2002, Pages 285-293 DOI: 10.1142/S0219581X02000255. 10.1021/cm2000649, Schreier F: The Voigt and complex error function: a comparison of computational methods. Because aniline and azobenzene were in competition on the GOx surface, the secondary electron edge did not show a significant shift toward higher kinetic energies. The amine group in the aniline donated an electron carrier to the GOx surface, indicating that aniline acted as an electron dopant on the EG surface (n-type characteristic). <>/Rotate 0/Type/Page>> Figure 2a shows the optical microscopy image of the EG surface grown on a 6H-SiC(0001) substrate. 10.1016/j.ssc.2008.02.024, Article  The surface-bound products were investigated using micro Raman spectroscopy, high-resolution photoemission spectroscopy, and work function measurements. The EG and GOx surfaces were used in the subsequent experiments involving the oxidation of aniline, which is difficult to oxidize in general. The red spectrum in Figure 4a shows the work function of the GOx surface, showing that the secondary electron edge had shifted by 220 meV (Δϕ = 0.22 eV) toward higher kinetic energies relative to the monolayer EG secondary electron edge. Raman spectroscopy and high-resolution photoemission spectroscopy (HRPES) were used to characterize the surface-bound products. Aminoazobenzene. Unlike aniline, azobenzene acted as an electron acceptor (p-type characteristic). <> The doping characteristic changed from n-type to p-type as the oxidation reaction proceeded from aniline to azobenzene. Figure 3d, on the other hand, clearly revealed that the relative intensity ratio between aniline and azobenzene increased with increasing aniline coverage on the GOx surface. A Si-terminated 6H-SiC(0001) substrate (Cree Research, Durham, NC, USA) was used to fabricate EG. The work function was measured as the center position of the low kinetic energy cut-off for each sample, as shown in Figure 4a. Correspondence to The morphological discrepancies observed between the optical images could only be explained in terms of a surface reaction, as supported by the HRPES results. Phys Rev Lett 2008, 100: 016602(4). © 2002 World Scientific Publishing Company, www.worldscinet.com/ijn. Raman spectra of the samples were collected using a home-built system equipped with an Ar+ ion laser (Spectra-Physics Stabilite 2017, Santa Clara, CA, USA) as an excitation source; a spectrometer (Horiba Jobin Yvon TRIAX 550, Kyoto, Japan), and a CCD detector (Horiba Jobin Yvon Symphony) cooled to 140 K. The wavelength of the incident excitation beam was 514.5 nm. Manage cookies/Do not sell my data we use in the preference centre. 2018-01-23T06:11:09-08:00 This result indicated that the oxygen carriers on the GOx surface acted as p-type dopant materials. Lee, M., Kim, K. & Lee, H. The aniline-to-azobenzene oxidation reaction on monolayer graphene or graphene oxide surfaces fabricated by benzoic acid. Nature 2007, 448: 457–460. The scheme indicates that the fabrication of the GOx surfaces using benzoic acid. Because aniline and azobenzene … 10.1021/jp072440j. AppendPDF Pro 5.5 Linux Kernel 2.6 64bit Oct 2 2014 Library 10.1.0 Cahen D, Kahn A: Electron energetics at surfaces and interfaces: concepts and experiments. Solid State Commun 2008, 146: 351–355. > Micro optical images of (a) monolayer EG and (b) a GOx surface. %PDF-1.7 %���� Phys Rev B 2009, 79: 125437(7). n-Type doping was observed at high aniline concentrations (at lower aniline deposition), whereas p-type doping was observed at high azobenzene concentrations (at higher aniline deposition) on the GOx surface. > The spectra are colored as in Figure 4a. 10.1021/cm201131v, Dikin DA, Stankovich S, Zimney EJ, Piner RD, Dommett GHB, Evmenenko G, Nguyen ST, Ruoff RS: Preparation and characterization of graphene oxide paper. Nature Mater 2008, 7: 151–157. The oxidation of aniline to azobenzene was conducted in the presence of either monolayer graphene (EG) or graphene-oxide-like surface, such as GOx, under ultra-high vacuum conditions maintaining a 365-nm … Black curve, monolayer EG; red curve, GOx surface prepared using benzoic acid; green curve, 3,600 L aniline; blue curve, 10,800 L aniline; and purple, 14,400 L aniline. The magnified valence band spectra indicated the presence of a band gap, and the insulating properties resulted from the high oxide character of the substrate. endobj Unlike aniline, azobenzene acted as an electron acceptor (p-type characteristic). Optical microscopy images of the EG (a) and GOx (b) surfaces were acquired, and their corresponding Raman spectra at two positions (over a particle and over the bottom region) were collected, as shown in Figure 2. The Raman D/G intensity ratio for the GOx surface was found to be 0.92, similar to the results reported previously for graphene oxide[18]. As shown in Figure 1, the EG surface structure was confirmed using LEED and C 1 s core-level spectroscopy (not shown here) and then immersed into a benzoic acid solution for 3 min. endobj Terms and Conditions, J. Langston, Rochester Institute of Technology | A higher aniline concentration increased the p-type doping character by increasing the azobenzene concentration on the GOx surface. All spectra were recorded in the normal emission mode. It is a useful platform for fabricating functionalized graphene that can potentially confer improved mechanical, thermal, or electronic properties. The substrate was degassed, annealed at 1,200 K under a Si flux (1 Å/min), and graphitized at temperatures up to 1,500 K (for 2 min) to produce a monolayer of graphene (EG). <>/Rotate 0/Type/Page>> 5 0 obj Note that the G band (1,613.1 cm–1) obtained from the particle position was shifted toward higher wavenumbers relative to the G bands of graphene and graphite. 10.1038/nmat2082, Schedin F, Geim AK, Morozov SV, Jiang D, Hill EH, Blake P, Novoselov KS: Detection of individual gas molecules adsorbed on graphene.

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