title: Chemical Modification of Graphene Oxide by Nitrogenation: An X-ray Absorption and Emission Spectroscopy Study.
abstract: Nitrogen-doped graphene oxides (GO:Nx) were synthesized by a partial reduction of graphene oxide (GO) using urea [CO(NH2)2]. Their electronic/bonding structures were investigated using X-ray absorption near-edge structure (XANES), valence-band photoemission spectroscopy (VB-PES), X-ray emission spectroscopy (XES) and resonant inelastic X-ray scattering (RIXS). During GO:Nxsynthesis, different nitrogen-bonding species, such as pyrrolic/graphitic-nitrogen, were formed by replacing of oxygen-containing functional groups. At lower N-content (2.7 at%), pyrrolic-N, owing to surface and subsurface diffusion of C, N and NH is deduced from various X-ray spectroscopies. In contrast, at higher N-content (5.0 at%) graphitic nitrogen was formed in which each N-atom trigonally bonds to three distinct sp2-hybridized carbons with substitution of the N-atoms for C atoms in the graphite layer. Upon nitrogen substitution, the total density of state close to Fermi level is increased to raise the valence-band maximum, as revealed by VB-PES spectra, indicating an electron donation from nitrogen, molecular bonding C/N/O coordination or/and lattice structure reorganization in GO:Nx. The well-ordered chemical environments induced by nitrogen dopant are revealed by XANES and RIXS measurements.
authors.affiliation: Department of Physics, Tamkang University, Tamsui 251, New Taipei City, Taiwan.
authors.forename: Cheng-Hao
authors.initials: CH
authors.lastname: Chuang
authors.affiliation: Department of Physics, University of South Africa, Florida Science Campus-1710, Johannesburg, South Africa.
authors.forename: Sekhar C
authors.initials: SC
authors.lastname: Ray
authors.affiliation: Department of Physics, University of South Africa, Florida Science Campus-1710, Johannesburg, South Africa.
authors.forename: Debarati
authors.initials: D
authors.lastname: Mazumder
authors.affiliation: Engineering Research Institute, School of Engineering, Ulster University, BT37 0QB, Newtownabbey, UK.
authors.forename: Surbhi
authors.initials: S
authors.lastname: Sharma
authors.affiliation: Engineering Research Institute, School of Engineering, Ulster University, BT37 0QB, Newtownabbey, UK.
authors.forename: Abhijit
authors.initials: A
authors.lastname: Ganguly
authors.affiliation: Engineering Research Institute, School of Engineering, Ulster University, BT37 0QB, Newtownabbey, UK.
authors.forename: Pagona
authors.initials: P
authors.lastname: Papakonstantinou
authors.affiliation: Department of Applied Physics, National University of Kaohsiung, Kaohsiung 811, Taiwan.
authors.forename: Jau-Wern
authors.initials: JW
authors.lastname: Chiou
authors.affiliation: National Synchrotron Radiation Research Center, Hsinchu 300, Taiwan.
authors.forename: Huang-Ming
authors.initials: HM
authors.lastname: Tsai
authors.affiliation: National Synchrotron Radiation Research Center, Hsinchu 300, Taiwan.
authors.forename: Hung-Wei
authors.initials: HW
authors.lastname: Shiu
authors.affiliation: National Synchrotron Radiation Research Center, Hsinchu 300, Taiwan.
authors.forename: Chia-Hao
authors.initials: CH
authors.lastname: Chen
authors.affiliation: National Synchrotron Radiation Research Center, Hsinchu 300, Taiwan.
authors.forename: Hong-Ji
authors.initials: HJ
authors.lastname: Lin
authors.affiliation: Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA.|Department of Chemistry and Biochemistry, University of California, Santa Cruz, California 95064, USA.
authors.forename: Jinghua
authors.initials: J
authors.lastname: Guo
authors.affiliation: Department of Physics, Tamkang University, Tamsui 251, New Taipei City, Taiwan.
authors.forename: Way-Faung
authors.initials: WF
authors.lastname: Pong