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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.
ACS Nano 11/2010; 4(12):7499-507. · 10.77 Impact Factor
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ABSTRACT: The effect of azafullerene encapsulation on the electronic states of single-wall carbon nanotubes (SWCNTs) is investigated; UV-vis-NIR absorption and photoluminescence spectroscopy shows that the interaction between SWCNTs and the encapsulated azafullerenes is originated from the weak intermolecular forces, which suggests a lack of strong doping effect such as electron transfer between them.
Chemical Communications 02/2010; 46(8):1293-5. · 6.17 Impact Factor
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ABSTRACT: Methods of insertion of azafullerenes in single-walled carbon nanotubes (SWNTs) at different temperatures were investigated, while the effects of the conditions applied on the structure of azafullerene-based peapods, namely, C59N@SWNTs, were explored. Morphological characteristics of C59N@SWNTs were assessed and evaluated by means of high-resolution transmission electron microscopy (HR-TEM). Pathways and chemical reactions that occur upon encapsulation of C59N within SWNTs were evaluated. Monomeric azafullerenyl radical C59N. as inserted into SWNTs at high temperature, from purified (C59N)2 in the gas phase, can undergo a variety of different transformations forming dimers, oligomers or existing in its monomeric form inside SWNTs due to the stabilization effect by nanotube side walls. However, under milder conditions, that is, at lower temperature, bisazafullerene (C59N)2 can be inserted into SWNTs in its pristine dimeric form.
Journal of the American Chemical Society 06/2008; 130(19):6062-3. · 9.91 Impact Factor
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ABSTRACT: 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 (Cu(II)tpy) with oxidized carbon nanohorns (CNHs-COOH). The resulted CNHs-COO-Cu(II)tpy 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-Cu(II)tpy 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 Cu(II)tpy to CNHs. Photoexcitation of Cu(II)tpy resulted in the one-electron reduction of nanohorns with a simultaneous one-electron oxidation of the Cu(II)tpy unit (CNHs(*-)-COO-(Cu(II)tpy)*+) as revealed by transient absorption measurements. The charge-separated state of CNHs(*-)-COO-(Cu(II)tpy)*+ has been confirmed with the aid of an electron mediator, such as hexyl-viologen dication (HV2+) and an electron-hole shifter in polar solvents.
Journal of the American Chemical Society 05/2008; 130(14):4725-31. · 9.91 Impact Factor
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ABSTRACT: Carbon nanahorns (CNH) were functionalized following the methodology of 1,3-dipolar cycloaddition of azomethine ylides and found to form stable solutions in either organic solvents or water. The number of added functional units, in the form of pyrrolidine moieties, was calculated when a pyrene chromophore was utilized in the modification scheme. Moreover, complementary theoretical calculations revealed that reactivity enhancement is expected at locations near the conical-shaped tip of CNH, where the highest curvature and strain exist. Finally, additional organic transformation of already modified CNH was exploited by covalently linked ferrocene units.
Journal of Nanoscience and Nanotechnology 11/2007; 7(10):3468-72. · 1.56 Impact Factor
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ABSTRACT: Density functional (DFT) calculations, high-temperature electron paramagnetic resonance (EPR) and transmission electron microscopy (TEM) results suggest that thermal homolysis of C59HN involves a remarkably stable intermediate C59N-C59HN* structure characterised by charge redistribution from a C59N* radical to a bonded C59HN.
Chemical Communications 09/2007; · 6.17 Impact Factor
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ABSTRACT: We have designed and synthesized several structural isomers of anthramycin (heterocycles 2, 3, 5, 6, and 8) and found that, in particular, pyrrolobenzodiazepine 8 induces DNA cleavage and formation of small fragments of DNA. The cytotoxic effects of 8 were manifested with both non-transformed primary neuronal/glial cells and transformed Jurkat cells. The other compounds did not change the viability either of transformed or of non-transformed cells, and induced DNA cleavage to a lesser extent.
Bioorganic & Medicinal Chemistry Letters 08/2005; 15(13):3220-3. · 2.55 Impact Factor
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Tetrahedron. 60(48):10825-10832.
