Department of Chemistry and Pharmacy and Joint Institute of Advanced Materials and Processes (ZMP), Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Henkestrasse 42, 91054 Erlangen, Germany.
Chair for Applied Physics, Department of Physics, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Staudtstraße 7, 91058 Erlangen, Germany.
Sci Rep. 2017 Mar 27;7:45165. doi: 10.1038/srep45165.
Covalent functionalisation of graphene is a continuously progressing field of research. The optical properties of such derivatives attract particular attention. In virtually all optical responses, however, an enhancement in peak intensity with increase of sp carbon content, and a vanishing of the peak position shift in monolayer compared to few-layer systems, is observed. The understanding of these seemingly connected phenomena is lacking. Here we demonstrate, using Raman spectroscopy and in situ electrostatic doping techniques, that the intensity is directly modulated by an additional contribution from photoluminescent π-conjugated domains surrounded by sp carbon regions in graphene monolayers. The findings are further underpinned by a model which correlates the individual Raman mode intensities to the degree of functionalisation. We also show that the position shift in the spectra of solvent-based and powdered functionalised graphene derivatives originates predominantly from the presence of edge-to-edge and edge-to-basal plane interactions and is by large functionalisation independent.
石墨烯的共价功能化是一个不断发展的研究领域。这类衍生物的光学性质尤其受到关注。然而，在几乎所有的光学响应中，都观察到随着 sp 碳含量的增加，峰值强度增强，并且与少层系统相比，单层系统的峰值位置移动消失。对于这些看似相关的现象，人们缺乏理解。在这里，我们使用拉曼光谱和原位静电掺杂技术证明，在石墨烯单层中，由 sp 碳区域包围的光致发光π共轭域的额外贡献直接调制了强度。通过将各个拉曼模强度与功能化程度相关联的模型进一步证实了这一发现。我们还表明，溶剂化和粉末状功能化石墨烯衍生物的光谱中的位置移动主要源于边缘到边缘和边缘到基面相互作用的存在，并且在很大程度上与功能化无关。
