A New Raman Metric for the Characterisation of Graphene oxide and its Derivatives

Abstract

Raman spectroscopy is among the primary techniques for the characterisation of graphene materials, as it provides insights into the quality of measured graphenes including their structure and conductivity as well as the presence of dopants. However, our ability to draw conclusions based on such spectra is limited by a lack of understanding regarding the origins of the peaks. Consequently, traditional characterisation techniques, which estimate the quality of the graphene material using the intensity ratio between the D and the G peaks, are unreliable for both GO and rGO. Herein we reanalyse the Raman spectra of graphenes and show that traditional methods rely upon an apparent G peak which is in fact a superposition of the G and D’ peaks. We use this understanding to develop a new Raman characterisation method for graphenes that considers the D’ peak by using its overtone the 2D’. We demonstrate the superiority and consistency of this method for calculating the oxygen content of graphenes, and use the relationship between the D’ peak and graphene quality to define three regimes. This has important implications for purification techniques because, once GO is reduced beyond a critical threshold, further reduction offers limited gain in conductivity.

Bioconjugated graphene oxide‐based Raman probe for selective identification of SKBR3 breast cancer cells

“…However, to enable photoluminescence, the band gap of graphene can be opened by reducing its size to the nanometer scale, introducing reduction in size of sp 2 domains and/or formation of sp 3 defects or modifying its two‐dimensional carbon–carbon network with functional groups. 44–46 Recent reports show a strong emission from the electronic transitions at various energy levels when the GO is modified to oxy functional groups . The luminescence properties can be optimized with pH of the GO in aqueous solution.…”

Physicochemical properties of reduced graphite oxide conglomerated polyethylene nanocomposites

“…It is noteworthy that the I D / I G ratio increases from 0.951 for GO to 1.406 for rGO. This confirms the reduction of GO with the formation of more numerous smaller graphitic domains during the reduction by sodium borohydride …”

Evolution of the graphite surface in phosphoric acid: an AFM and Raman study

“…However, after subtraction we still observe other second-order features, which are commonly found in disordered carbon materials or graphene molecules [20]. The Raman features of the disordered phase show remarkable analogies to the Raman spectra of samples of graphene oxides subjected to chemical reduction [21]. This analogy suggests that the material formed at the graphite surface is the result of the EC oxidation of graphene sheets, possibly followed by partial reduction.…”