Chemical functionalization of exfoliated graphene.

Graphene is turning out to be the material that will effectively kick-start a new era for nanotechnology. The impressive properties of this atom-thick carbon layer are taking shape and form with early reports of successful applications based on it. The turning point for this material will be its low-cost mass production. In this report a chemist's perspective on the production methods for graphene and the subsequent functionalization processes is discussed.

Exfoliation and chemical modification using microwave irradiation affording highly functionalized graphene.

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.

Microwave assisted covalent functionalization of C(60)@SWCNT peapods.

The covalent functionalization of the external wall of C(60)@SWCNT peapods, by in situ generated aryl diazonium salts, assisted by microwave irradiation is reported. Spectroscopic, thermal and microscopy characterization was performed. Electrochemistry revealed the three reversible reductions of encapsulated C(60), however, shifted towards positive potentials when compared with those of intact C(60).

Fullerene-coumarin dyad as a selective metal receptor: synthesis, photophysical properties, electrochemistry and ion binding studies.

A coumarin derivative with a malonate unit has been synthesized and used for the preparation of a fullerene-coumarin dyad through the Bingel cyclopropanation method. The newly synthesized dyad is soluble in organic solvents and has been fully characterized with traditional spectroscopic techniques. Electronic interactions between the two components of the dyad were probed with the aid of UV/Vis spectroscopy, fluorescence emission, and electrochemistry measurements. Our studies clearly show the presence of electronic interactions between C(60) and modified coumarin in the ground state; efficient electron-transfer quenching of the singlet excited state of the coumarin moiety by the appended fullerene sphere was also observed. Time-resolved fluorescence measurements revealed lifetimes for the coumarin-C(60) dyad at a maximum of 50 ps, while the quantum yield was reaching unity. Additionally, the redox potentials of the C(60)-coumarin dyad were determined and the energetics of the electron-transfer processes were evaluated. Finally, after alkaline treatment of C(60)-coumarin, which resulted in the deprotection of carboxylate units, the dyad was tested as a metal receptor for divalent metal cations; ion competition studies and fluorescence experiments showed binding selectivity for lead ions.