利用同步輻射X光技術鑑定氧化石墨烯、其水熱還原法和氮摻雜影響的化學組態和電子結構

Chemical Composition and Electronic Structure of Graphene Oxide with the Hydrothermal Reduction and Nitrogenation Effect by Synchrotron-related Spectroscopies

莊程豪(Cheng-Hao Chuang)

《化學》 75卷2期 (2017/06) Pp. 135-154

https://doi.org/10.6623/chem.2017018

摘要

利用同步輻射X光技術，鑑定氧化石墨烯和其還原或氮摻雜影響，透過元素分析的化學組態、電子結構、和能帶結構，提升對相關石墨烯材料的了解。利用化學合成法，將塊狀石墨解離成可溶於水的氧化石墨烯片，再透過水熱還原法，減少石墨烯片表面氧化物量，因表面電阻率和光致螢光產生明顯變化，經由X 光吸收和發射光譜鑑定出苯環結構重組和氧化官能基轉換，並得出元素分辨的能隙結構與表面混合sp^2和sp^3鍵結環境有關，最終經過高水熱還原後，其能帶結構出現線性能量與動量分布趨勢。另外，氧化石墨烯使用微波氮摻雜法，除了氮摻雜比例可增加外，也有效還原氧化官能基和其苯環結構，使用光電子能譜定義出氧和氮官能基鍵結，而費米能階下出現明顯價帶極限變化(5.1 eV → 2.6 eV)，再經由元素相關X光能譜，分析石墨烯和表面官能基相關未佔據態行為，由共振或非共振下探測法，將高低氮摻雜下價帶結構和價電子分布對應出相似的能隙行為。相比於一般分析方法，同步輻射技術將更可針對複合性材料做元素相關的電子結構和化學鍵結環境分析。

關鍵字

氧化石墨烯 ； 水熱還原法 ； 氮參雜 ； 拉曼光譜 ； X光吸收光譜 ； X光放射光譜 ； 共振非彈性X光散射光譜 ； 光電子能譜

並列摘要

Using the synchrotron-related X-ray technologies, the graphene oxide and its chemical reduction and nitrogen modification can be identifiedfrom the element-dependent chemical composition, electronic structure, and band structure, for further understanding in graphene-related materials. The chemical oxidation method can separate the multi-layer graphite effectively into the graphene-like flake in water solution owing to the surface oxidation and hydrophilic property. The hydrothermal treatment with the certain degrees offers the obvious change of surface resistances and photoluminescence. Soft X-ray absorption and emission spectroscopy identifies the element-resolved band gap with the mixing region between sp^2 and sp^3 configuration of graphene. Resonant inelastic X-ray scattering measurement delivers the linear energy-momentum dispersion near K point in highest hydrothermal graphene oxide. Microwave nitrogenation method for graphene oxides is considered to the possibility of the carbon purification to the benzene structure, nitrogen doping to the ordered binding structure, and surface oxidation to the chemical reduction. X-ray photoelectron spectroscopy is employed to investigate the oxygen and nitrogen functional groups and the shift of valence band maximum below the Fermi level (5.1 eV → 2.6 eV). The element-resolved absorption and emission spectroscopy can probe the unoccupied and occupied state (partial density of state) near Fermi level, corresponding to the shift of total density of state in valence band. On/off-resonant emission spectroscopy can dynamically examine the bonding configuration in the band structure. Relatively speaking, X-ray spectroscopies can focus on the analysis of electronic structure and chemical environment of heterogeneous materials.

並列關鍵字

Graphene oxide ； Hydrothermal reduction ； Nitrogenation ； Raman spectroscopy ； X-ray absorption spectroscopy ； X-ray emission spectroscopy ； Resonant inelastic X-ray scattering ； X-ray photoelectron spectroscopy