Infrared and Raman spectroscopic analysis of functionalized graphene
Karsten Hinrichs, Tilmann Neubert, Christoph Kratz, Timur Shaykhutdinov, Jörg Rappich, Kannan Balasubramanian
In this mini-review, we discuss our work in the analysis of material properties of electrochemically functionalized graphene using infrared (IR) and Raman techniques as thin film sensitive vibrational spectroscopies. Multi-scale characterization is demonstrated using a combination of IR spectroscopic ellipsometry (IRSE), confocal Raman spectroscopy (RS) and photothermal atomic force microscopy coupled IR analysis (AFM-IR). IRSE is used for spots with dimensions of a few mm, RS for spots with a diameter of a few µm and AFM-IR at the sub-100 nm scale. In the first part of the article, functionalized large-area graphene sheets electrochemically modified by ultrathin oligomer films of maleimidophenyl (MP) or 4-aminophenyl acetic acid (4-APhAA) are studied. Characteristic molecular vibrations of the functional layers are analyzed by the IR methods while the graphene-related phonons are characterized by RS. This dual approach allowed for the determination of the attached functional groups as well as the identification of the nature of chemical coupling of the functional moieties to graphene. The thickness of the deposited layers extracted from IRSE data correlates very well with AFM measurements. In the second part of the article, functionalized graphene sheets are characterized by correlative vibrational optical spectroscopy directly at a device level.
material research, functional groups, graphene