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Nanoscopic infrared characterisation of graphene oxide
[Thesis]. Manchester, UK: The University of Manchester; 2019.
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Abstract
Graphene oxide (GO) is a single layer of carbon atoms decorated with oxygen groups, which has recently gained interest as a reinforcing filler in composite materials, in filtration processes and for biomedical applications. However, the structure of GO has not been fully characterised, mainly due to the lack of spectroscopic techniques for the unambiguous identification of the oxygen groups onto the surface of GO at the nanoscale. Only recently it has been demonstrated that by using a contact mode Atomic Force Microscopy (AFM) coupled with an IR tuneable source (AFM-IR) it is possible to characterise monolayer GO flakes with a spatial resolution below the diffraction limit. This work investigates the thickness dependence of AFM-IR analysis with respect to GO spectroscopy and provides a comparison with the conventional FTIR of GO materials. This thesis highlights the great discrepancies within the two IR techniques especially on thinner samples (<10nm) and therefore goes some way to showing the limit of detection for AFM-IR of GO and other two-dimensional materials on a range of techniques. Through experimental investigation, it has been found that that the roughness of the substrate plays an important role in the AFM-IR characterisation of nanomaterials. It has also been discovered that by using an atomically smooth gold substrate the IR amplitude signals of GO flakes are significantly enhanced. It is anticipated that further improvements of the AFM-IR characterisation could arise from the results found in this thesis; such as the use of different substrates that could lead to an increase of the IR amplitude signal of monolayer GO, further decreasing the detection limit and increasing both the spectral and spatial resolution of this technique for two-dimensional materials.
Keyword(s)
Graphene; Graphene Oxide; Nanomapping; Nanoscale infrared Spectroscopy