A versatile route to edge-specific modifications to pristine graphene by electrophilic aromatic substitution

Abstract

This work presents a general method for producing edge-modified graphene using electrophilic aromatic substitution. Five types of edge-modified graphene were created from graphene/graphite nanoplatelets sourced commercially and produced by ultrasonic exfoliation of graphite in N-methyl-2-pyrrolidone. In contrast to published methods based on Friedel-Crafts acylation, this method does not introduce a carbonyl group that may retard electron transfer between the graphene sheet and its pendant groups. Graphene sulphonate (G-SO 3-) was prepared by chlorosulphonation and then reduced to form graphene thiol (G-SH). The modifications tuned the graphene nanoparticles' solubility: G-SO 3 was readily dispersible in water, and G-SH was dispersible in toluene. The synthetic utility of the directly attached reactive moieties was demonstrated by creating a ''glycographene'' through radical addition of allyl mannoside to G-SH. Chemical modifications were confirmed by FT-IR and XPS. Based on XPS analysis of edge-modified GNPs, G-SO 3 and G-SH had a S:C atomic ratio of 0.3:100. XPS showed that a significant amount of carbon sp 2 character remained after functionalisation, indicating little modification to the conductive basal plane. The edge specificity of the modifications was visualised on edge-modified samples of graphene produced by chemical vapour deposition (CVD): scanning electron microscopy of gold nanoparticles attached to G-SH samples,

Functional groups in graphene oxide

“…7b). 137 Due to the reactivity of thiol groups, edge localization was visualized by attaching gold nanoparticles on the graphene-SH. 137…”

“…136 Shellard and co-workers reported electrophilic aromatic substitution as an alternative method for designing edge-thiolated graphene. 137 The experimental process involves the chlorosulphonation of graphene sheets, followed by reduction into thiol (–SH) moieties, which was further attached with allyl mannoside via radical addition reaction to create glycographene for biomedical applications (Fig. 7b).…”

Preparation of graphene/copper composites with a thiophenol molecular junction for thermal conduction application

“…48 It has been reported that the characteristic peaks of sulfur-related functional groups are usually less pronounced in the infrared spectrum. 49 Here, although there are no obvious characteristic stretching signals assigned to S-H in the region of 2500-2600 cm À1 , 44,47,50 a weak peak attributed to the C-SH bending vibration can still be observed at 797 cm À1 . 43,47,51 The new presence of the characteristic peaks to thiophenol groups in the infrared spectrum of TP-Gr can preliminarily confirm the successful grafting of thiophenol groups onto the graphene.…”

Highly active PtCo nanoparticles on hierarchically ordered mesoporous carbon support for polymer electrolyte membrane fuel cells

“…The absorption at about 1580 cm -1 (G band) is related to the vibration of sp 2hybridized carbon atom known as graphite band, and the D band at around 1340 cm -1 is correlated with the disorder sp 3 -hybridized carbon know as non-graphitic band. The disorder degree of carbon structure is usually evaluated by the intensity ratio I D /I G [42]. The value of I D /I G of Vulcan @ XC-72 is much greater than that of OMC, indicating a lower graphitization degree in Vulcan @ XC-72.…”