Interesting fluorescence properties of C60-centered dendritic adduct with twelve symmetrically attached pyrenes.

A C60-centered dendritic adduct with 12 symmetrically attached pyrene species was synthesized and found to have relatively simple fluorescence emission kinetics, in particular, the mono-exponential decay of the significant pyrene excimer emission.

Dispersion and solubilization of carbon nanotubes.

Carbon nanotubes are generally insoluble in any solvents, resulting in their poor processability for many proposed potential applications. Several strategies have been developed to introduce carbon nanotubes into solvent systems, including dispersion and suspension under special experimental conditions and the chemical modification and functionalization. The well-dispersed and solubilized carbon nanotubes make it possible to characterize and study the carbon nanotubes by using solution-based techniques, to realize some of the unique properties of the nanotubes, and to carry out further chemical transformations. In this review, recent development in the experimental methods for the dispersion and solubilization of carbon nanotubes will be summarized and discussed.

Spectroscopic probing of organic molecules encapsulated in functionalized carbon nanotubes in solution.

Pyrene was introduced into cavities in functionalized single-walled and multiple-walled carbon nanotubes to be used as a molecular probe in the study of encapsulation. The solubility of these materials in common organic solvents allowed solution-phase absorption and emission spectroscopic measurements. The results, which are consistent with the formation of pyrene excimer, are explained in terms of high local pyrene concentrations and perhaps pyrene microcrystals inside the carbon nanotube cavities. The fluorescence decay results show that there is significant quenching of pyrene excited states by the hosting carbon nanotubes.

Functionalization of carbon nanotubes with bovine serum albumin in homogeneous aqueous solution.

Single-walled (SWNTs) and multiple-walled (MWNTs) carbon nanotubes were solubilized via the esterification of nanotube-bound carboxylic acids by oligomeric polyethylene glycol compounds. The water-soluble samples were used as starting materials in reactions with bovine serum albumin (BSA) protein in ambient aqueous solutions. The reaction conditions were designed for thermodynamically favorable transformation from ester to amide linkages, yielding SWNT-BSA and MWNT-BSA conjugates. The results show that the use of soluble starting nanotube materials in an indirect functionalization method represents a valuable approach to the biomodification of carbon nanotubes.

Gel permeation chromatography of fullerene-centered macromolecules.

Gel permeation chromatography (GPC) behavior of fullerene-centered macromolecules is investigated. Because of the globular shape of the macromolecules, their GPC results are different from those of linear polystyrene standards. These macromolecules may serve as alternative molecular weight standards for polymers or dendrimers of similar globular structures. The results also show that the GPC analysis is capable of discerning relatively minor structural differences in the fullerene-centered macromolecules.

Functionalized carbon nanotubes: properties and applications.

Carbon nanotubes can be functionalized via amidation and esterification of the nanotube-bound carboxylic acids. The solubility of these functionalized carbon nanotubes makes it possible to characterize and study the properties of carbon nanotubes using solution-based techniques. Representative results concerning the solubility, dispersion, defunctionalization, and optical properties of the functionalized carbon nanotubes are presented. Several examples for the use of functionalized carbon nanotubes in the fabrication of polymeric carbon nanocomposites, the probing of nanotube-molecule interactions, and the conjugation with biological species are highlighted and discussed.

Deuterium attachment to carbon nanotubes in deuterated water.

A systematic investigation on the unusual attachment of labile deuterium to carbon nanotubes in deuterated water and alcohols is reported. The carbon nanotubes were solubilized through the established functionalization of the nanotube-bound carboxylic acids to allow solution-phase reaction and characterization. The deuterium attachment was found under several experimental conditions, including the use of deuterated ethanol as a co-reactant in the nanotube functionalization reaction and the refluxing of functionalized or simply purified carbon nanotubes in deuterated water and alcohols. The solubility of the functionalized carbon nanotube samples in common organic solvents and water allowed unambiguous (2)H NMR characterization. The reproducible broad (2)H NMR signal at approximately 6.5 ppm is assigned to carbon nanotube-attached deuterium species. The assignment is supported by the results from FT-IR measurements. The carbon-deuterium interaction is so strong that the corresponding vibration resembles the typical C-D stretching mode in the characteristic frequency region. The FT-IR peak intensities also correlate well with the (2)H NMR signal integrations in a series of samples. Mechanistic implications of the results are discussed.