The five distinct peaks corresponding to monolayer EG were clearly observed [22]. The magnified Fermi edge spectrum (Figure  4d) revealed the typical characteristics of monolayer EG. The red spectrum, obtained from the GOx surface, displayed remarkable insulating properties, as demonstrated by the band gap at 0.25 eV. 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. Other spectra were obtained after depositing at various Torin 2 concentration coverages. These figures showed that the valence band spectra were similar to the spectra obtained from the GOx surface, even at higher coverage deposition. The oxidation process did not appear to affect the structure of the GOx surface, Etomoxir ic50 suggesting that the oxygen groups present on the GOx surface supplied oxygen atoms during the oxidation reaction. The Raman spectra and HRPES experiments further supported the conclusion that the oxidation reaction occurred on the GOx surface. The work function of the surface was monitored as the doping characteristic changed from p-type to n-type due to charge transfer from the GOx surface to the adsorbed aniline or azobenzene. The doping characteristic changed from n-type to p-type as the oxidation reaction proceeded from aniline to azobenzene. Conclusions The oxidation of aniline to azobenzene was investigated on a GOx surface prepared

using benzoic acid. Micro optical images and their corresponding Raman spectra, HRPES measurements, and work function measurement were conducted from the samples prepared under a variety of conditions. The Raman images revealed the structure of the GOx surface prepared using benzoic acid. The HRPES measurements indicated that the relative concentration of aniline and azobenzene varied with the aniline surface coverages. The work functions of the samples were measured as a function of the aniline surface coverage to identify

the major product of the surface reaction. 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 oxygen carriers present on the GOx surface were found to act as the reaction reagents. Acknowledgements This research was Amylase supported by the Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education, Science and Technology (2013–021127). The experiments at the PLS were supported in part by MEST, POSTECH, XFEL project. References 1. Bolotiin KL, Sikes KJ, Jiang Z, Klima M, Fudenber G, Hone J, Kim P, Stormer HL: Ultrahigh electron mobility in suspended graphene. Solid State Commun 2008, 146:351–355.CrossRef 2. Morozov SV, Novoselov KS, Katsnelson ML, Schedin F, Eliasm DC, Jaszcazk JA, Geim AK: Giant intrinsic carrier mobilities in graphene and its bilayer. Phys Rev Lett 2008, 100:016602(4).