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

Azafullerenes Encapsulated within Single-Walled Carbon Nanotubes

Azafullerenes Encapsulated within Single-Walled Carbon Nanotube

(Terpyridine)copper(II)−Carbon Nanohorns: Metallo-nanocomplexes for Photoinduced Charge Separation

New metallo-nanostructured materials of carbon nanohorns (CNHs), within the family of elongated carbon nanotubes, have been prepared by the coordination of copper(II)−2,2‘:6‘,2‘ ‘-terpyridine (CuIItpy) with oxidized carbon nanohorns (CNHs-COOH). The resulted CNHs-COO−CuIItpy metallo-nanocomplexes have been characterized by diverse analytical spectroscopic tools and cyclic and differential pulse voltammetry. Scanning transmission electron microscopy (STEM), dynamic light scattering (DLS), and energy dispersive X-ray spectroscopy (EDX) measurements have been employed to probe the morphological characteristics and particle-size distribution of CNHs-COO−CuIItpy as well as to investigate the elemental composition of the metallo-nanocomplex. Steady-state and time-resolved fluorescence emission studies have shown efficient fluorescence quenching, suggesting that electron transfer occurs from the singlet excited state of CuIItpy to CNHs. Photoexcitation of CuIItpy resulted in the one-electron reduction of nanohorns with a simultaneous one-electron oxidation of the CuIItpy unit (CNHs•--COO−(CuIItpy)•+) as revealed by transient absorption measurements. The charge-separated state of CNHs•--COO−(CuIItpy)•+ has been confirmed with the aid of an electron mediator, such as hexyl-viologen dication (HV2+) and an electron−hole shifter in polar solvents

Case Study for Artificial Photosynthesis: Noncovalent Interactions between C₆₀-Dipyridyl and Zinc Porphyrin Dimer

In this study, a new modified C₆₀ derivative with an oPE/oPPV conjugated bridge bearing two pyridyl groups has been used in combination with a flexible porphyrin dimer (<b>ZnP</b>_<b>2</b>) to construct an electron donor/acceptor hybrid (<b>C</b>_<b>60</b><b>-dipyr·ZnP</b>_<b>2</b>). This hybrid is based on metal to ligand coordination between the zinc centers of the porphyrin dimer and the two pyridyl groups that oPE/oPPV linker bears. In order to investigate the interactions between the electron donor and acceptor entities, both in the ground state and in the excited states, comprehensive photophysical assays have been carried out. In particular, both absorption and fluorescence titrations provided evidence for strong interactions between the electron donor and the electron acceptor within the hybrid. A binding constant (<i>K</i>_ass) in the order of 5.0 × 10⁵ M^–1 has been derived. Furthermore, transient absorption measurements revealed intramolecular electron-transfer from the photoexcited porphyrin dimer (<b>ZnP</b>_<b>2</b>) to the fullerene derivative (<b>C</b>_<b>60</b><b>-dipyr</b>), leading to a long-lived charge-separated state with a lifetime of up to 1525 ps