On the Suitability of Raman Spectroscopy to Monitor the Degree of Graphene Functionalization by Diazonium Salts

Abstract

Raman spectroscopy is undoubtedly the most frequently used technique for universal characterization of graphene and related materials. Quantification of parameters like disorder or strain is possible through analysis of particular Raman bands. However, under certain conditions, such evaluation can be jeopardized by-sometimes hidden-convolution of more overlapping effects. In this work graphene functionalization by the common nitrobenzene diazonium salt under simultaneous biaxial tensile deformation induced by substrate swelling was investigated by Raman spectroscopy. As expected, the disorder-related D band appeared in the spectra documenting the covalent attack on the graphene lattice. However, the strain-induced shift of the graphene bands exposed additional peaks, masked at exactly the same positions as the unstrained graphene bands. The new bands were assigned to vibrations of the diazonium molecule and its decomposition products adsorbed on top of the functionalized graphene. The external strain thus provided means for more correct quantification of the lattice disorder.

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

“…A Raman map of sulphonated CVD graphene (Figure S6) showed that the I D /I G ratio was lowered at the edges, demonstrating that the chemical modifications complicate this simple metric for graphene order. This effect has previously been discussed for graphene with its basal plane modified by diazonium salts [93]. Metrics based on the relative areas of the D and G peaks, namely the average domain diameter, L A a , and average distance between point defects, L D , were more consistent.…”

Grafting of Diazonium Salts on Surfaces: Application to Biosensors

“…One of the most important features of diazonium grafting is the stability of the construct; this was demonstrated by several methods including (i) thermogravimetry, where exfoliated graphene lost only 7% of its coating at 400 °C [50], (ii) spectrometric methods, where a small Raman band at 412 cm −1 was assigned to the Au(nP)-C(aryl) bond of gold nanoparticles modified by 4-nitrobenzenediazonium [51]; grafting of an aryl group on graphene [52] and carbon nanotubes [53,54] transformed an sp 2 carbon into a sp 3 , which translated into the growth of the D-band.…”

Advances and Trends in Chemically Doped Graphene

“…[148,149] In plenty of reports, these graphitic derivatives have presented remarkable applications ranging from energy generation to sensing and magnetic purposes. [150][151][152][153][154]…”