Soluble Single-walled Carbon Nanotubes Research Articles

Peptides that non-covalently functionalize single-walled carbon nanotubes to give controlled solubility characteristics

Methods which solubilize single-walled carbon nanotubes (SWNTs) in water as individuals, not bundles, while retaining their unique electronic, photonic and mechanical properties are highly desirable. Furthermore, functionalization with a diverse array of selectable chemical moieties would allow the range of useful applications to be significantly extended and may permit the designed assembly of SWNT networks. This paper presents a series of peptides that non-covalently solubilize carbon nanotubes in water using a design motif that combines a combinatorial library sequence to bind to nanotubes with a rationally designed section to create environmentally tuned solubility characteristics. The ability of the peptides to individually disperse carbon nanotubes without altering their electronic structure is shown by vis-NIR absorbance, fluorescence, and regular and vitreous ice cryo-TEM. Identification of the species composition of each sample by NIR fluorescence reveals that the peptides exhibit some diameter selectivity. Additionally, one of the rationally designed modifications addresses the poor stability of non-covalently solubilized SWNT suspensions by including cysteine residues for covalent crosslinking between adjacent peptides.

Single-Walled Carbon Nanotubes Template the One-Dimensional Ordering of a Polythiophene Derivative

We have used a mechanochemical high-speed vibration milling (HSVM) technique to solubilize single-walled carbon nanotubes (SWNTs) in organic solvents through the formation of complexes between the SWNTs and a polythiophene (PT) derivative. This HSVM approach is superior to the conventional sonication method used to solubilize SWNTs in organic solvents. Moreover, we found that in these supramolecular complexes the PT chains were ordered one-dimensionally on the SWNT surfaces in organic solvents. [structure: see text].

Synthesis of, Light Emission from, and Optical Power Limiting in Soluble Single-Walled Carbon Nanotubes Functionalized by Disubstituted Polyacetylenes

Single-walled carbon nanotubes are covalently functionalized by conjugated polyacetylenes through their cyclization reactions with poly(1-phenyl-1-alkyne) and poly(diphenylacetylene) derivatives carrying azido functional groups at the ends of their alkyl pendants. The resultant polyene nanotube addends are soluble in common solvents, emit intense visible lights and strongly attenuate the power of harsh laser pulses.

Protein-Assisted Solubilization of Single-Walled Carbon Nanotubes

We report a simple method that uses proteins to solubilize single-walled carbon nanotubes (SWNTs) in water. Characterization by a variety of complementary techniques including UV-Vis spectroscopy, Raman spectroscopy, and atomic force microscopy confirmed the dispersion at the individual nanotube level. A variety of proteins differing in size and structure were used to generate individual nanotube solutions by this noncovalent functionalization procedure. Protein-mediated solubilization of nanotubes in water may be important for biomedical applications. This method of solubilization may also find use in approaches for controlling the assembly of nanostructures, and the wide variety of functional groups present on the adsorbed proteins may be used as orthogonal reactive handles for the functionalization of carbon nanotubes.

Individual solubilization of single-walled carbon nanotubes using totally aromatic polyimide

We report here the finding by means of visible-near IR absorption and near-IR fluorescence spectroscopies and atomic force microscopy that a total aromatic polyimide has a high potential to solubilize single-walled carbon nanotubes (SWNTs) individually in organic solutions. The solutions contained SWNTs having (7, 6), (7, 5), (8, 4), (9, 5) and (8, 6) indices. With the increasing concentrations of SWNTs, the solutions became viscous and then changed to gels that exhibited characteristic spectral features of individually dissolved SWNTs.

Chemically Functionalized Water Soluble Single-Walled Carbon Nanotubes Modulate Neurite Outgrowth

We report the use of chemically-functionalized water soluble single-walled carbon nanotube (SWNT) graft copolymers for modulation of outgrowth of neuronal processes. The graft copolymers were prepared by the functionalization of SWNTs with poly-m-aminobenzene sulphonic acid and polyethylene glycol. When added to the culturing medium, these functionalized water soluble SWNTs were able to increase the length of various neuronal processes.

Spectroscopic study on the centrifugal fractionation of soluble single-walled carbon nanotubes

Optical absorption and resonant Raman spectra are proven to be convenient and effective to monitor the centrifugal fractionation and to evaluate the quality of soluble single-walled carbon nanotubes (SWNTs) achieved by inorganic oxidation and organic functionalization. Through a systemic study of a series of centrifuged solutions, we confirmed that heavily functionalized amorphous carbon was fractionated into the early centrifuged solutions, whereas lightly functionalized graphite fragments as well as polyhedral carbon and metal catalysts particles were fractionated into the late centrifuged solutions and centrifuged residue, and then highly pure and well dispersed SWNTs were collected from the middle centrifuged solutions. It is proposed that the purity, dispersibility, and aggregation state of SWNTs can be qualitatively estimated by the relative intensity of their absorption features, the fine structure and slope of their absorption curves. The Raman features of centrifuged SWNTs are found systematically up-shifted except the disorder-induced D band in comparison with those of as-prepared material, indicating that the SWNTs in centrifuged solutions are individual or in thin bundles. Two new features were identified at 1428 and 941 cm −1 in the Raman spectrum of thermally annealed centrifuged SWNTs, which were assigned to achiral nanotubes and combined mode, respectively.

Synthesis and Characterization of Water Soluble Single-Walled Carbon Nanotube Graft Copolymers

Poly(aminobenzene sulfonic acid) (PABS) and polyethylene glycol (PEG) were covalently attached to single-walled carbon nanotubes (SWNTs) to form water-soluble graft copolymers. Quantitative near-IR (NIR) spectroscopic studies of these SWNT graft copolymers indicate a water solubility of about 5 mg/mL, and atomic force microscopy studies show a fairly uniform length and diameter. On the basis of thermogravimetric analysis, the loading of SWNTs in the graft copolymers is estimated to be 30% for SWNT-PABS and 71% for SWNT-PEG. NIR spectroscopic studies of SWNT-PABS show that this graft copolymer has a ground state that is a hybrid of the electronic structures of the isolated PABS and SWNT macromolecules.

Noncovalent Functionalization of Single-Walled Carbon Nanotubes with Water-Soluble Porphyrins

We have employed water-soluble porphyrin molecules [meso-(tetrakis-4-sulfonatophenyl) porphine dihydrochloride] to solubilize single-walled carbon nanotubes (SWNTs), resulting in aqueous solutions that are stable for several weeks. The porphyrin-nanotube complexes have been characterized with absorption and fluorescence spectroscopy and with AFM. We find that the porphyrin/SWNT interaction is selective for the free base form, and that this interaction stabilizes the free base against protonation to the diacid. Under mildly acidic conditions nanotube-mediated J-aggregates form, which are unstable in solution and result in precipitation of the nanotubes over the course of a few days. Porphyrin-coated SWNTs can be precisely aligned on hydrophilic poly(dimethylsiloxane) (PDMS) surfaces by combing SWNT solution along a desired direction and then transferred to silicon substrates by stamping. Parallel SWNT patterns have been fabricated in this manner.

Multifunctional Single-Walled Carbon Nanotube Polycarbonate Composites

ABSTRACTUniform single-walled carbon nanotube (SWNT) polycarbonate composites were fabricated using noncovalently functionalized, soluble SWNTs. These composites showed dramatic improvements in the electrical conductivity and mechanical tensile strength at low SWNT loading. We also observed a stress-induced SWNT alignment in polycarbonate film, which is very difficult to achieve with pristine SWNTs.

Assignment of the Fine Structure in the Optical Absorption Spectra of Soluble Single-Walled Carbon Nanotubes

Raw electric-arc-produced single-walled carbon nanotubes (SWNTs) were dispersed in organic solvents via a three-step wet chemistry procedure. The soluble sample was purified by continuous dispersion−centrifugation cycles and well-separated SWNTs with high purity were successfully obtained, which enable us to test the separated tube properties and make comparisons with theoretical predictions. Optical absorption experiments on such prepared samples yield fine structures. A series of optical absorptions including some unobserved in previous works are identified. On the basis of the electronic band theory, all the spectral features are systematically assigned to the electronic transitions between pairs of van Hove singularities of semiconducting and/or metallic SWNTs. Detailed analysis of the optical absorption and Raman scattering data reveals that electric-arc-produced SWNTs are preferentially formed with seven discrete diameters and with chirality close to the armchair direction, and a chiral indices (n, ...

Homogeneous carbon nanotube/polymer composites for electrical applications

Homogeneous carbon nanotube/polymer composites were fabricated using noncovalently functionalized, soluble single-walled carbon nanotubes (SWNTs). These composites showed dramatic improvements in the electrical conductivity with very low percolation threshold (0.05–0.1 wt % of SWNT loading). By significantly improving the dispersion of SWNTs in commercial polymers, we show that only very low SWNT loading is needed to achieve the conductivity levels required for various electrical applications without compromising the host polymer’s other preferred physical properties and processability. In contrast to previous techniques, our method is applicable to various host polymers and does not require lengthy sonication.

Ester-functionalized soluble single-walled carbon nanotubes

We report the preparation of soluble ester- functionalized single-wall carbon nanotubes (sSWNT-COO(CH2)17CH3). By use of solution phase IR spectroscopy we are able to compare the ratio of the carbon atoms in the SWNT backbone to the carbon atoms in the ester and amide functionalities of s-SWNTs.

Chromatographic purification and properties of soluble single-walled carbon nanotubes.

We report an improved chromatographic purification of soluble single-walled carbon nanotubes (s-SWNTs) using gel permeation chromatography. Three fractions are separated by gel permeation chromatography, and the first fraction contains 74% of the s-SWNTs as detected by atomic force microscopy and UV and near-infrared spectroscopy.

End-group and defect analysis of soluble single-walled carbon nanotubes

By use of solution phase mid-IR spectroscopy we are able to obtain an estimate for the ratio of the carbon atoms in the single-walled carbon nanotube (SWNT) backbone to the carbon atoms in the end-groups and at defect sites of the octadecylamido (ODA) functionalized soluble SWNTs (s-SWNT-CONH(CH 2) 17CH 3). This analysis shows that the weight percentage of the octadecylamido functionality in the s-SWNTs is about 50%.