Chuang C-H, Wang Y-F, Shao Y-C, Yeh Y-C, Wang D-Y, Chen C-W, Chiou J W, Ray Sekhar C, Pong W F, Zhang L, Zhu J F, Guo J H
Department of Physics, Tamkang University, Tamsui 251, Taiwan.
Department of Material Science and Engineering, National Taiwan University, Taipei 106, Taiwan.
Sci Rep. 2014 Apr 10;4:4525. doi: 10.1038/srep04525.
Electronic structures of graphene oxide (GO) and hydro-thermally reduced graphene oxides (rGOs) processed at low temperatures (120-180°C) were studied using X-ray absorption near-edge structure (XANES), X-ray emission spectroscopy (XES) and resonant inelastic X-ray scattering (RIXS). C K-edge XANES spectra of rGOs reveal that thermal reduction restores C = C sp(2) bonds and removes some of the oxygen and hydroxyl groups of GO, which initiates the evolution of carbonaceous species. The combination of C K-edge XANES and Kα XES spectra shows that the overlapping π and π* orbitals in rGOs and GO are similar to that of highly ordered pyrolytic graphite (HOPG), which has no band-gap. C Kα RIXS spectra provide evidence that thermal reduction changes the density of states (DOSs) that is generated in the π-region and/or in the gap between the π and π* levels of the GO and rGOs. Two-dimensional C Kα RIXS mapping of the heavy reduction of rGOs further confirms that the residual oxygen and/or oxygen-containing functional groups modify the π and σ features, which are dispersed by the photon excitation energy. The dispersion behavior near the K point is approximately linear and differs from the parabolic-like dispersion observed in HOPG.
利用X射线吸收近边结构（XANES）、X射线发射光谱（XES）和共振非弹性X射线散射（RIXS）研究了在低温（120 - 180°C）下处理的氧化石墨烯（GO）和水热还原氧化石墨烯（rGO）的电子结构。rGO的C K边XANES光谱表明，热还原恢复了C = C sp(2)键，并去除了GO中的一些氧和羟基，从而引发了含碳物种的演变。C K边XANES和Kα XES光谱的结合表明，rGO和GO中重叠的π和π轨道与无带隙的高度有序热解石墨（HOPG）相似。C Kα RIXS光谱提供了证据，表明热还原改变了在GO和rGO的π区域和/或π与π能级之间的间隙中产生的态密度（DOS）。rGO深度还原的二维C Kα RIXS映射进一步证实，残余的氧和/或含氧官能团改变了π和σ特征，这些特征被光子激发能分散。K点附近的色散行为近似线性，与HOPG中观察到的抛物线状色散不同。
