Influence of architecture on the Raman spectra of acid-treated carbon nanostructures

Abstract

Raman spectroscopy was used to characterise 11 varieties of carbon nanostructures (CNSs) consisting on seven varieties of commercial multi-walled carbon nanotubes, two types of carbon nanofibres and two types of lab-synthesised single-walled carbon nanotubes. The Raman spectra of these CNSs provided information on the structural ordering of the as-received (or as-synthesised) material. Additionally, the CNSs were chemically treated by two mixtures of nitric and sulphuric acids at markedly different concentrations and then characterised by Raman spectroscopy. The features of the G and D Raman bands of the CNSs were used to assess structural modifications and generation of defects induced by the acid treatments. Changes in the Raman spectra before and after acidic treatment depend strongly on the initial intensity ratio of the G to D bands and the architecture (number of layers or diameter) of the CNSs.

Novel Preparation, Microstructure, and Properties of Polyacrylonitrile-Based Carbon Nanofiber–Graphene Nanoplatelet Materials

“…28,29 A narrow G-band is an indication of higher structural ordering and crystallinity. 29 Therefore, the intensity ratio of the D- and G-bands and the shape of these bands can be used to determine the structural ordering in the CNFs. It is clearly seen from Table 2 that increasing the GNP concentration decreased the I D / I G ratio of the pyrolyzed samples, indicating greater graphitization in the samples.…”

Electrodeposition of Cu–SWCNT Composites

“…This observation suggests that the structure of the SWCNTs underwent a consistent change during the electroplating process, possibly due to the presence of acetic acid in the plating bath. Prior research has suggested that nanotubes with low diameters and initial IG:ID > 1 are significantly susceptible to structural modification during acid treatment [47]. It was observed previously [42] that when Cu coating is less than 0.165 µm the oxide is CuO (with a Cu 2 O interface to Cu); however, when the coating is thicker than 0.165 µm the oxide is Cu 2 O.…”

“…This observation suggests that the structure of the SWCNTs underwent a consistent change during the electroplating process, possibly due to the presence of acetic acid in the plating bath. Prior research has suggested that nanotubes with low diameters and initial IG:ID > 1 are significantly susceptible to structural modification during acid treatment [47].…”

Nanostructured carbons containing FeNi/NiFe2O4 supported over N-doped carbon nanofibers for oxygen reduction and evolution reactions

“… 46 The I D / I G ratio for G/CNT@NCNF decreased from 1.4 to 1.07 after acid treatment due to removal of amorphous and defective carbon from the CNF surfaces, thus, increasing the relative graphitic content. 47 In contrast, acid treatment increased the I D / I G ratio from 1.11 to 1.21 for GS@NCNF, which may be due to the removal of FeNi embedded graphene sheets from the CNF surfaces (Fig. S2 † ).…”