Bioelectrochemical single-walled carbon nanotubes

Metalloproteins and enzymes can be immobilized on SWNTs of different surface chemistry. The combination of high surface area, robust immobilization and inherent nanotube electrochemical properties is of promising application in bioelectrochemistry.     

Antenna chemistry with metallic single-walled carbon nanotubes

We show that, when subjected to microwave fields, surfactant-stabilized single-walled carbon nanotubes (SWNTs) develop polarization potentials at their extremities that readily drive electrochemical reactions. In the presence of transition metal salts with high oxidation potential (e.g., FeCl3), SWNTs drive reductive condensation to metallic nanoparticles with essentially diffusion-limited kinetics in a laboratory microwave reactor. Using HAuCl4, metallic particles and sheaths deposit regioselectively at the SWNT tips, yielding novel SWNT-metal composite nanostructures. This process is shown to activate exclusively metallic SWNTs; a degree of diameter selectivity is observed using acceptors with different oxidation potentials. The reaction mechanism is shown to involve Fowler-Nordheim field emission in solution, where electric fields concentrate at the SWNT tips (attaining approximately 10(9) V/m) due to the SWNT high aspect ratio (approximately 1000) and gradient compression in the insulating surfactant monolayer. Nanotube antenna chemistry is remarkably simple and should be useful in SWNT separation and fractionation processes, while the unusual nanostructures produced could impact nanomedicine, energy harvesting, and synthetic applications.     

Glassy carbon electrodes modified with DNA-partly-wrapped single-walled carbon nanotubes

DNA-partly-wrapped single-walled carbon nanotubes (DNA-p-SWCNTs) were separated from the mixtures of calf thymus DNA and SWCNTs in solution by differential centrifugation for the first time. Average mass ratios of DNA to SWCNTs for DNA-p-SWCNTs and DNA-fully-wrapped-SWCNTs (DNA-f-SWCNTs) were determined to be 0.8 and 2.0, respectively. It has been found that DNA-p-SWCNTs could form a uniform and porous film on glassy carbon electrodes due to special structure of them, which could facilitate the electron transfer between positively-charged compounds and electrodes, and showed good enrichment capability at low ionic strength.     

Soluble ultra-short single-walled carbon nanotubes

Soluble, ultra-short (length < 60 nm), carboxylated, single-walled carbon nanotubes (SWNTs) have been prepared by a scalable process. This process, predicated on oleum's (100% H2SO4 with excess SO3) ability to intercalate between individual SWNTs inside SWNT ropes, is a procedure that simultaneously cuts and functionalizes SWNTs using a mixture of sulfuric and nitric acids. The solubility of these ultra-short SWNTs (US-SWNTs) in organic solvents, superacid and water is about 2 wt %. The availability of soluble US-SWNTs could open opportunities for forming high performance composites, blends, and copolymers without inhibiting their processibility.     

Interaction of single-walled carbon nanotubes with sulfuric acid

An increase in the radiation yield of paramagnetic centers in H₂SO₄ + nanotubes (NTs) solutions was evidence of the sensitizing influence of NTs on the low-temperature radiolysis of sulfuric acid, that is, on excitation energy and charge transfer. Under the conditions selected, the influence of NTs extended to distances of 100–300 nm. The presence of NTs also influenced the interstice nanodiffusion of atomic hydrogen by decreasing kinetic heterogeneity of the vitrified matrix surrounding NTs. No chemical interaction between atomic hydrogen and carbon NTs was observed at 77–120 K. The diffusion of radical-base anions occurred following the vacancy mechanism and was independent of the presence of NTs. Nanotubes did not form a separate phase as sulfuric acid solutions were cooled to 77 K. The transition from the vitreous to supercooled liquid state was observed as irradiated and nonirradiated solutions were heated to 175 K; no phase transitions occurred over the temperature range 180–300 K. For the first time, substantial changes in the electronic spectra of sulfuric acid solutions of NTs with time were observed: an intense additional absorption band at 320 nm appeared in the spectra in several days. This band was supposedly related to the formation of complexes between H₂SO₄ molecules and the surface of NTs.     

Interaction of SiO2 with single-walled carbon nanotubes

The effects of coating of a single-walled carbon nanotube (SWNT) with a nonbonded layer of silica are investigated via model system employing fully coordinated silica clusters. The geometric and electronic structures of the SWNT@SiO(2) composite system are calculated using periodic density functional (DF) calculations for a range of confining silica coatings. We show that silica can provide a protective bound coating to a single walled nanotube, which, importantly, only weakly perturbs the underlying properties of both components. Detailed analysis of the charge redistribution and changes in electronic structure upon coating the SWNT are performed to support this conclusion. Furthermore, as allowed by our versatile model system, the energetics of rotating a silica "bearing" around a nanotube "spindle" is also calculated to indicate the possibilities for SWNT@SiO(2)-based nanomechanical devices.     

Pegylated single-walled carbon nanotubes with gelable block copolymers

Functional amphiphilic block copolymer poly（ethylene glycol）-block-poly[（3-（triethoxysilyl）propyl methacrylate）-co -（1-pyrene-methyl） methacrylate],PEG₁₁₃-b-P(TEPM₂₆-co-PyMMA₄),was synthesized via atom transfer radical polymerization（ATRP） initiated by monomethoxy capped poly（ethylene glycol） bromoisobutyratc.This polymer exhibited strong ability to disperse and exfoliate single-walled carbon nanotubes（SWNTs） in different solvents due to the adhesion of pyrene units to surface of SWNTs.In aqueous solution,the PTEPM segments that were located on the nanotube surfaces with the pyrene units could be gelated and,as a result,the silica oxide networks with PEG coronas were formed on the surface of nanotubes,which ensured the composites with a good dispersibility and stability.Furthermore,functional silane coupling agents,3-mercaptopropyltrimethoxysilane and 3-aminopropyltriethoxysilanc,were introduced during dispersion of SWNTs using the block copolymers.They were co-gelated with PTEPM segments,and the-SH and-NH₂ functionalities were introduced into the silica oxide coats respectively.     

Lithium storage in single-walled carbon nanotubes

Here, we investigated the lithium insertion/extraction mechanism in single-walled carbon nanotubes (SWNTs) based both on the empty SWNTs and filled SWNTs, including ferrocene-filled SWNTs (Fc@SWNTs) and C₆₀-filled SWNTs (C₆₀@SWNTs). SWNTs, C₆₀@SWNTs and Fc@SWNTs were systematically investigated as anode materials for Li-ion batteries. The electrochemical performance of the C₆₀@SWNT electrode was slightly better than that of the SWNTs, and the reversible capacity of Fc@SWNTs per unit weight was ～1.7 times greater than that of the empty SWNTs due to its special tube internal structure. It was proved that the dominant reversible sites for lithium storage in empty SWNTs are the trigonal interstitial channels. Meanwhile, lithium can reversibly insert or extract the inner channels of the tubes after doping with ferrocene; the reversible capacity presented in the inner channels of Fc@SWNTs is about Li_1.13C₆.     

Fluorimetric characterization of single-walled carbon nanotubes

Single-walled carbon nanotubes (SWCNTs) are a family of structurally related artificial nanomaterials with unusual properties and many potential applications. Most SWCNTs can emit spectrally narrow near-IR fluorescence at wavelengths that are characteristic of their precise diameter and chiral angle. Near-IR fluorimetry therefore offers a powerful approach for identifying the structural species present in SWCNT samples. Such characterization is increasingly important for nanotube production, study, separation, and applications. General-purpose and specialized instruments suitable for SWCNT fluorimetric analysis are described, and methods for interpreting fluorimetric data to deduce the presence and relative abundances of different SWCNT species are presented. Fluorescence methods are highly effective for detecting SWCNTs in challenging samples such as complex environmental or biological specimens because of the methods’ high sensitivity and selectivity and the near absence of interfering background emission at near-IR wavelengths. Current limitations and future prospects for fluorimetric characterization of SWCNTs are discussed.     

Long super-bundles of single-walled carbon nanotubes

200 nm-thick super bundles showing a novel polygonization and densely aligned arrangement are found in long single-walled carbon nanotube (SWNT) strands prepared by the vertical floating catalytic method.     

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.     

Discrete dispersion of single-walled carbon nanotubes

Single-walled carbon nanotubes (SWNTs) have been effectively wetted and dispersed in saturated sodium hydroxide (NaOH) alcohol-water solutions with little surface damage or shortening of the tubes; the treated material was dissolvable as individual tubes in many common organic solvents.     

Azafullerenes encapsulated within single-walled carbon nanotubes

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.     

Infrared spectroscopy of single-walled carbon nanotubes

By using the spectral moments method, we calculate the infrared spectra of chiral and achiral single-walled carbon nanotubes (SWCNTs) of different diameters and lengths. We show that the number of the infrared modes, their frequencies, and intensities depend on the length and chirality of the nanotubes. Furthermore, the dependence of the infrared spectrum as a function of the size of the SWCNT bundle is analyzed. These predictions are useful to interpret the experimental infrared spectra of SWCNTs.     

Stability of supershort single-walled carbon nanotubes

How short can single-walled carbon nanotubes (SWNTs) be? How stable are such supershort SWNTs (ss-SWNTs)? This work is the first to address these questions. On the basis of binding energy (E(B)), standard heats of formation , and strain energy (E(S)), we found that SWNTs with only one benzene ring in the axial direction, which we refer to as supershort SWNTs (ss-SWNTs), can be thermodynamically stable. On the basis of the data of E(B), , and E(S), the relative stabilities of ss-SWNTs, fullerenes, polycyclic aromatic hydrocarbons, and butadiyne are discussed. This study has laid a theoretical foundation for the possible synthesis of ss-SWNTs.     

Functional macromolecules from single-walled carbon nanotubes: synthesis and photophysical properties of short single-walled carbon nanotubes functionalised with 9,10-diphenylanthracene

9,10-Diphenylanthracene (DPA), a well-studied organic chromophore (Phi(fl) = 0.98) that exhibits electroluminescence, has been covalently bound through 2-(ethylthio)ethylamido linkers to the carboxylic acid groups of short, soluble single-walled carbon nanotubes (sSWNTs) of 1 microm average length, and the resulting DPA-functionalised sSWNT (DPA- sSWNT) macromolecular adducts (4.6 wt % DPA content) characterised by solution (1)H NMR, Raman and IR spectroscopy and thermogravimetric analysis. Comparison of the quenching of DPA fluorescence (steady-state and time-resolved) and of the transient optical spectra of sSWNTs and DPA-sSWNTs show that the covalent linkage boosts the interaction between the DPA and the sSWNT units. DPA-sSWNTs exhibit emission in the near-IR region from 1100-1400 nm with an enhanced quantum yield (Phi = 5.7x10(-3)) compared with sSWNTs (Phi = 3.9x10(-3)).     

Sidewall functionalization of single-walled carbon nanotubes with organic peroxides

Single-wall carbon nanotubes (SWNTs) and their fluorinated derivatives (F-SWNTs) were reacted with organic peroxides including benzoyl and lauroyl peroxide to produce phenyl and undecyl sidewall functionalized SWNTs, respectively, which were characterized by Raman, FTIR, and UV-Vis-NIR spectra as well as TGA/MS, TGA/FTIR, and TEM data.     

Selective interactions of porphyrins with semiconducting single-walled carbon nanotubes

A derivatized porphyrin with long alkyl chains, 5,10,15,20-tetrakis(hexadecyloxyphenyl)-21H,23H-porphine, is selective toward semiconducting single-walled carbon nanotubes (SWNTs) in presumably noncovalent interactions, resulting in significantly enriched semiconducting SWNTs in the solubilized sample and predominantly metallic SWNTs in the residual solid sample according to Raman, near-IR absorption, and bulk conductivity characterizations.     

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.