Supramolecular hybrids of [60]fullerene and single-wall carbon nanotubes

Noncovalent interactions between purified HiPCO single-wall carbon nanotubes (SWNT) and a [60]fullerene-pyrene dyad, synthesized through a regioselective double-cyclopropanation process, produce stable suspensions in which the tubes are very well dispersed, as evidenced by microscopy characterization. Cyclic voltammetry experiments and photophysical characterization of the suspensions in organic solvents are all indicative of sizeable interactions of the pyrene moiety with the SWNT and, therefore, of the prevalence in solution of [60]fullerene-pyreneSWNT hybrids.     

An unexpected new optimum in the structure space of DNA solubilizing single-walled carbon nanotubes

Here we report quantitative data on the amount of single-walled carbon nanotubes that can be suspended with oligodeoxynucleotides in aqueous buffer, together with rate constants for the thermal denaturation of the resulting DNA-nanotube complexes at elevated temperatures. Sequence motifs d(GT)n and d(AC)n with n=2, 3, 5, 10, 20, or 40 were employed, both individually and as equimolar mixtures of the complementary strands. Unexpectedly, the greatest suspending efficiency was found for the mixture of short, complementary oligonucleotides d(GT)3 and d(AC)3. Unlike the suspending efficiency, the kinetic stability of the nanotube suspensions increases with increasing chain length of the DNA, with half life times of >25 h at 90 degrees C for the complexes of the longest strands. Our results identify a new, unexpected optimum in DNA sequence space for suspending carbon nanotubes. They also demonstrate that suspending power depends on the presence of complementary strands. Exploratory assays suggest that nanotubes can be deposited site-selectively from suspensions formed with short DNA sequences.     

Toward a 6pi+6pi zwitterion or a bioinhibitors-related OH-substituted aminoquinone: identification of a key intermediate in their pH controlled synthesis

Their pH-controlled reactivity places the N,N'-dialkyl-2-amino-5-lithium alcoholate-1,4-benzoquinonemonoimines [C(6)H(2)(NHCH(2)R') (=NCH(2)R')(=O)(OLi)] 7 (R'=tBu) and 8 (R'=p-C(6)H(4)-tBu) at the crossroads of a new versatile strategy for the preparation of two very different classes of substituted quinones. We describe new 2-(N-alkyl)amino-5-hydroxy-1,4-benzoquinones, which are parent molecules to biologically active substituted aminobenzoquinones, for which changes of the N-substituent will become readily possible. The results of the first X-ray structural determination of such compounds ([C(6)H(2)(NHCH(2)tBu)(OH)(=O)(2)] 13) are also reported and we compare the influence of the number of N-substituents of the C(6) ring on the supramolecular networks resulting from self-assembling of 13, zwitterionic N,N'-dineopentyl-2-amino-5-alcoholate-1,4-benzoquinonemonoiminium [C(6)H(2)(=NHCH(2)tBu)(2)(=O)(2)] 9 and N,N',N",N"'-tetraneopentyl-2,5-diamino-1,4-benzoquinone diimine [C(6)H(2)(NHCH(2)tBu)(2)(=NCH(2)tBu)(2)] 15.     

Noncovalent functionalization and solubilization of carbon nanotubes by using a conjugated Zn-porphyrin polymer

A highly soluble, conjugated Zn-porphyrin polymer was synthesized and found to strongly interact with the surface of single-walled carbon nanotubes, producing a soluble polymer-nanotube complex. Successful complexation required the addition of trifluoroacetic acid to the solvent (THF). It was found that the complex remained soluble after excess free polymer was removed from solution, and could be centrifuged at high speed with no observable sedimentation. Furthermore, the polymer-nanotube assembly resulted in enhanced planarization and conjugation within the porphyrin polymer, which was manifested in a 127 nm bathochromic shift of the Q-band absorption. Control experiments with the Zn-porphyrin monomer indicated that homogeneous solutions could be prepared by means of sonication, but the monomer-nanotube interactions were significantly weaker, leading to nanotube precipitation within minutes. Atomic force microscopy (AFM) studies indicated that the polymer enables exfoliation of nanotube bundles and is able to "stitch" multiple nanotubes together into a series of long, interconnected strands.     

Concave versus planar geometries for the hierarchical organization of mesoscopic 3D helical fibers

Chromophore-peptide systems: a study on a series of pentapeptides covalently connected to planar π systems (1 a and 1 b) or to a curved π system (1 c) showed the influence of the concave shape on the efficient chiral transmission at nano- and mesoscales. Control over the hierarchical growth by H bonding, π-π, and solvophobic interactions made possible the efficient generation of electroactive 3D helical fibers.     

Molecular assemblies of perylene bisimide dyes in water

Perylene bisimides are among the most valuable functional dyes and have numerous potential applications. As a result of their chemical robustness, photostability, and outstanding optical and electronic properties, these dyes have been applied as pigments, fluorescence sensors, and n‐semiconductors in organic electronics and photovoltaics. Moreover, the extended quadrupolar π system of this class of dyes has facilitated the construction of numerous supramolecular architectures with fascinating photophysical properties. However, the supramolecular approach to the formation of perylene bisimide aggregates has been restricted mostly to organic media. Pleasingly, considerable progress has been made in the last few years in developing water‐soluble perylene bisimides and their application in aqueous media. This Review provides an up‐to‐date overview on the self‐assembly of perylene bisimides through π–π interactions in aqueous media. Synthetic strategies for the preparation of water‐soluble perylene bisimides and the influence of water on the π–π stacking of perylene bisimides as well as the resulting applications are discussed.     

Carbon nanotubes as a support for Pt-and Pt-Ru-catalysts of reactions proceeding in fuel cells

Comparative study of two types of single-wall carbon nanotubes and standard carbon black Vulcan XC-72 as supports for catalysts of reactions proceeding in fuel cells is carried out. The nanotubes were prepared by arc method; they differed in the degree of their purifying from amorphous carbon and metal impurities. The structure and hydrophobic-hydrophilic properties of these carbon supports are studied by etalon porosimetry. The effect of the supports’ specific surface area on the deposited catalyst particles size and specific surface area is studied. The catalysts (Pt-Ru and Pt) were deposited from aqueous solutions of their salts. Platinum was also deposited by thermal decomposition of ethoxy clusters. It is shown that in methanol oxidation reaction at the Pt-Ru catalysts the current values per unit true surface area do not depend on the support nature, provided the catalyst loading is equal and the particle size is similar. When oxygen is reduced at platinum deposited onto purified nanotubes and the carbon black Vulcan XC-72, specific kinetic currents also are close to each other. It is shown that the degree of nanotubes purification and their structure affect the kinetics of this reaction significantly.     

Formation of efficient catalytic silver nanoparticles on carbon nanotubes by adenine functionalization

Stuck together: Adenine/carbon nanotube hybrids trigger the formation of controlled-size catalytic silver nanoparticles on the nanotube surface. The catalytic efficiency of the resulting species was assessed in the oxidation of 2-methylhydroquinone to its corresponding benzoquinone, with complete recovery and without loss of activity of the catalyst.     

Synthesis and structural characterization of lanthanide picrate complexes with a new binaphthylamide

Solid complexes of lanthanide picrates with N-Ethyl-2-{2′-[(ethyl-phenyl-carbamoyl)-methoxy]-[1,1′]binaphthalenyl-2-yloxy}-N-phenyl-acetamide (L), [Ln(pic)₃L] (Ln=La, Tb, Y), have been prepared and characterized by elemental analysis, IR and ¹H NMR spectra. The molecular structure of [Tb(pic)₃L] shows that the Tb(III) ion is nine-coordinated by four oxygen atoms from the L and five from two bidentate and one unidentate picrates. The complex forms a 1D supramolecular structure along z-axis.     

UV-light mediated decomposition of a polyester for enrichment and release of semiconducting carbon nanotubes

Purification of single-walled carbon nanotubes using conjugated polymers to selectively disperse either semiconducting or metallic nanotubes is effective and has received significant attention. However, the interaction between the conjugated polymer and the nanotube surface is very strong, making it difficult to remove the adsorbed polymer. Here, we report a poly(carbazole-co-terephthalate) polymer that is not only selective for semiconducting carbon nanotubes but can also be largely removed from the nanotube surface via irradiation with UV light. Irradiation of the polymer-nanotube dispersion causes degradation of ester linkages in the polymer backbone, effectively cutting the polymer into fragments that no longer bind strongly to the nanotube surface. Characterization of the electronic nature of the samples was carried out via the combination of absorption, Raman, and fluorescence spectroscopy. In addition, thermogravimetric analysis allowed determination of the amount of polymer left on the nanotube surface after irradiation and indicated that a large proportion of the polymer is removed. The reported methodology opens new possibilities for purification of semiconducting single-walled carbon nanotubes and their isolation from the polymeric dispersant.