A new insight into the structural modulation of graphene oxide upon chemical reduction probed by Raman spectroscopy and X-ray diffraction

Lately, Raman spectroscopy has become powerful tool for quality assessment of graphene analogues with identification of intensity ratio of Raman active D-band and G-band (I-D/I-G ratio) as a vital parameter for quantification of defects. However, during chemical reduction of graphitic oxide (GrO) to reduced GrO (RGrO), the increased I-D/I-G ratio is often wrongly recognized as defect augmentation, with formation of more numerous yet smaller size sp(2) domains as its explanation. Herein, by giving due attention to normalized peak height, full-width half-maxima and integrated peak area of Raman D- and G-bands, and compliment the findings by XRD data, we have shown that in-plane size of sp(2) domains actually increases upon chemical reduction. Particularly, contrary to increased I-D/I-G ratio, the calculated decrease in integrated peak area ratio (A(D)/A(G) ratio) in conjunction with narrowing of D-band and broadening of G-band, evinced the decrease in in-plane defects. Finally, as duly supported by reduction induced broadening of interlayer-spacing characteristic XRD peak and narrowing of similar to 43 degrees centered XRD hump, we have also shown that the sp(2) domains actually expands in size and the observed increase in I-D/I-G ratio is indeed due to increase in across-plane defects, formed via along-the-layer slicing of graphitic domains.

Automated summary

Recently, Raman spectroscopy has been utilized as a powerful tool for quality assessment of graphene analogues by identifying the intensity ratio of Raman active D-band and G-band (I-D/I-G ratio) as a key parameter for quantifying defects. However, during the chemical reduction process of graphitic oxide (GrO) to reduced GrO (RGrO), the increased I-D/I-G ratio is often mistakenly interpreted as defect augmentation, when in fact the in-plane size of sp(2) domains actually increases. Additionally, the observed increase in I-D/I-G ratio is due to an increase in across-plane defects, formed via along-the-layer slicing of graphitic domains, as supported by XRD data.