Exfoliation and Chemical Modification Using Microwave Irradiation Affording Highly Functionalized Graphene

Abstract

Efficient exfoliation of graphite flakes by sonicating them in benzylamine was accomplished, affording stable suspensions of few-layers graphene. The latter were chemically modified following the Bingel reaction conditions, with the aid of microwave irradiation, producing highly functionalized graphene-based hybrid materials. The resulting hybrid materials, possessing cyclopropanated malonate units covalently grafted onto the graphene skeleton, formed stable suspensions for several days in a variety of organic solvents and were characterized by diverse and complementary spectroscopic, thermal, gravimetric, and high-resolution electron microscopy techniques. When a malonate derivative, bearing the electro-active extended tetrathiafulvalene (exTTF) moiety, was synthesized and used for the functionalization of graphene, energy dispersive X-ray (EDX) analysis verified the presence of sulfur in the corresponding graphene-based hybrid material. Moreover, the redox potentials of the exTTF-graphene hybrid material were determined by electrochemistry, while the formation of a radical ion pair that includes one-electron oxidation of exTTF and one-electron reduction of graphene was suggested with the energy gap of (graphene)•−−(exTTF)•+ being calculated as 1.23 eV.

Exfoliation of graphene via wet chemical routes

“…Further optimization of the solvents led to some improvements in the dispersibility of graphene. For instance, concentrations as high as 0.03 mg/mL, 0.1 mg/mL and 0.5 mg/mL were achieved using o-DCB [32] and perfluorinated aromatic solvents such as pentafluorobenzonitrile [33] and benzylamine [34], respectively. However, due to the long ultrasonication process, the lateral dimension of LPE graphene is relatively small (<3 m).…”

Facile synthesis of graphene by pyrolysis of poly(methyl methacrylate) on nickel particles in the confined microzones

“…The resultant graphene still remains 4.2 wt.% as high temperature as 1000 8C. From the TGA curve, it can be concluded that the number of functional groups on the graphene sheets derivative from the stuff is less than that prepared using chemical methods [38,39]. Fig.…”

Interplay Between Mechanochemistry and Sonochemistry

“…The first step (halogenation reaction), involving the intercalation of the halogen between the graphite layers, is accelerated by microwaves so that the modified material can then be easily exfoliated into monolayer graphene in organic solvents under mild sonication. Alternatively, stable suspensions of few-layer graphene have been obtained via the sonication of graphite flakes in benzylamine which were then subjected to cyclopropanation under MW irradiation [71]. If all-carbon graphene has so far attracted enormous attention in mass media, the fact that polymerized organic crystals can also be exfoliated to create two-dimensional sheets should likewise open a new age of innovation in materials design.…”