Soluble Single-walled Carbon Nanotubes Research Articles

A Water Soluble Single Walled Carbon Nanotube Aryl Aziridino Carboxylic Acid Decorated Mn (II) Complex Increased Root Growth in Arabidopsis thaliana

AbstractSingle walled carbon nanotubes (SWCNTs) have been rendered water soluble as an aryl aziridino derivative decorated with carboxylic acids as a Mn (II) complex (III). This leads to increased root growth in Arabidopsis thaliana. The discovery of Nano‐carbon materials (NCMs) [Fullerenes, Carbon Nano Tubes (CNTs) and Graphene] has been recognized by the award of two Nobel prizes. Large‐scale industrial use of NCMs is hampered by their low solubility in most common solvents. The tensile strength of SWCNTs is approximately twenty three times more than that of steel and yet it is five times lighter. Successful functionalization makes CNTs more soluble allowing for many more possible applications in biomedical and material science (Solar cells). Synthesis of the water soluble SWCNT‐aryl‐aziridino‐carboxylic acid decorated Mn (II) complex (III) is described here along with its characterization using UV‐Visible, FT‐IR, Raman spectroscopy, EPR, TEM, Cyclic voltammetry techniques, confirming successful functionalization. SWCNT has been made water soluble by a two‐step procedure not involving any harsh steps like treatment with conc. acids. This has been achieved by reaction with an aryl azide followed by alkaline KMnO4 oxidation, when the above complex SWCNT−Mn (II) complex (III) was obtained. This complex has been observed to lead to increased root length growth in Arabidopsis thaliana.

Soluble single-walled carbon nanotubes for photovoltaics

Single wall carbon nanotubes (SWCNTs) have attracted great attentions in the fields of nanoscience and nanotechnology due to their unprecedented physical/chemical/mechanical stability and high dimensional aspect ratio resulting superior electrical properties. However, their poor solubility in both organic and aqueous solvents refrain their solution processability and hence practical applications. In the present work, we report one-pot functionalization of SWNCT based on the nitrene chemistry of two structurally different aromatic azides having ester functional groups (very low concentrations 10% w/w), by thermal activation which renders them soluble in organic solvents and water. The resulting functionalized SWCNTs (f-SWCNT I &f-SWCNT II) covalent linkage and the strong electronic interaction between the P3HT and f-SWCNTs are confirmed by various spectroscopic measurements and electrochemical analysis. The bulk heterojunction (BHJ) photovoltaic cell based on the solution cast P3HT:PCBM with doping concentrations of f-SWCNTs, demonstrate up to 30% increase in the power conversion efficiency with respect to the reference cell under AM 1.5 illumination (100mW/cm2).

In Vivo Fluorescence Imaging in the Second Near-Infrared Window with Long Circulating Carbon Nanotubes Capable of Ultrahigh Tumor Uptake

Cancer imaging requires selective high accumulation of contrast agents in the tumor region and correspondingly low uptake in healthy tissues. Here, by making use of a novel synthetic polymer to solubilize single-walled carbon nanotubes (SWNTs), we prepared a well-functionalized SWNT formulation with long blood circulation (half-life of ∼30 h) in vivo to achieve ultrahigh accumulation of ∼30% injected dose (ID)/g in 4T1 murine breast tumors in Balb/c mice. Functionalization dependent blood circulation and tumor uptake were investigated through comparisons with phospholipid-PEG solubilized SWNTs. For the first time, we performed video-rate imaging of tumors based on the intrinsic fluorescence of SWNTs in the second near-infrared (NIR-II, 1.1-1.4 μm) window. We carried out dynamic contrast imaging through principal component analysis (PCA) to immediately pinpoint the tumor within ∼20 s after injection. Imaging over time revealed increasing tumor contrast up to 72 h after injection, allowing for its unambiguous identification. The 3D reconstruction of the SWNTs distribution based on their stable photoluminescence inside the tumor revealed a high degree of colocalization of SWNTs and blood vessels, suggesting enhanced permeability and retention (EPR) effect as the main cause of high passive tumor uptake of the nanotubes.

Loading of single-walled carbon nanotubes in cationic cholesterol suspensions significantly improves gene transfection efficiency in serum

We present here a series of cholesterol based cationic lipid suspensions that solubilize single-walled carbon nanotubes (SWCNT) efficiently in water. Each cationic lipid formulation was characterized in terms of their energy minimized molecular structures, bilayer widths of the aggregates based on X-ray diffraction. Then these aggregates were investigated pertaining to their DNA binding and release efficiency, effect of CNT inclusion on the stability of cationic cholesterol lipid-DNA complexes, Zeta potential values and changes in the chiro-optical property of DNA, effect on Raman spectral shift and changes in morphology by SEM and AFM. Each cationic lipid formulation was optimized for the amount of SWCNT solubilized in water, lipid-DNA ratio, amount of the plasmid DNA that can be transfected and the effect on the cellular toxicity. The resulting SWCNT-lipid formulations were then used for in vitro transfection of pEGFP-C3 in A549 (human alveolar basal epithelial) cells and HeLa (human cervical cancer) cells. Advantageously, the CNT-loaded formulations confer an excellent transfection efficiency even in high percentages of blood serum and showed significantly better gene transfer efficiency compared to one of the potent, well-known commercial transfection reagent, Lipofectamine2000.

Portrait of carbon nanotube salts as soluble polyelectrolytes

Soluble single-walled carbon nanotube (SWNT) salts have been synthesized with varying negative charges, and their saturation solubilities in DMSO measured. A thermodynamic model of the Gibbs free energy of dissolution, widely used for polyelectrolytes, reproduces the experimental results with striking agreement. SWNT salts appear as a paradigm of stiff polyelectrolytes.

Meso-meso linked diporphyrin functionalized single-walled carbon nanotubes

Meso-meso linked diporphyrins ([H 2Por] 2) covalently functionalized soluble single-walled carbon nanotubes ([H 2Por] 2-SWNTs) have been successfully prepared. As a light-harvesting chromophore, meso-meso linked diporphyrins have been incorporated into a photosynthetic electron-transfer model with SWNTs as an electron-acceptor. The steady emission characteristics revealed the existence of the effective energy and electron transfer between the excited porphyrin moiety and SWNTs, and the electron transfer process was confirmed by electrochemical study. The charge separation quenching process was supported by the results of time-resolved transient absorption spectra, and the lifetime of charge-separation state was observed to be 145 ns, which was 2.5 times of that of monoporphyrin modified SWNTs (TPP-SWNTs).

Carbon nanotubes as modulators of neuronal growth

Event Abstract Back to Event Carbon nanotubes as modulators of neuronal growth Vladimir Parpura1* 1 University of Alabama, Department of Neurobiology, United Kingdom We are attempting to define whether carbon nanotubes (CNTs) could be used as prosthetics devices in the process of neuronal regeneration after injury. Towards that end we are investigating neuronal growth on multi-walled CNTs (MWNTs). Neuronal growth was systematically controlled by modified MWNTs, prepared by covalently conjugating CNTs with functionalities designed to carry negative, zwitterionic or positive charges at physiological extracellular pH. By using these CNTs as the scaffold for neuronal growth, it was found that the neurons grown on positively charged MWNTs showed more numerous growth cones, longer neurite outgrowth and more successful neurite branching than the neurons grown on negatively charged CNTs. Similarly, we prepared chemically-functionalized water soluble single-walled CNT (SWNT) graft copolymers for modulation of outgrowth of neuronal processes. The graft copolymers were prepared by the functionalization of SWNTs with poly-ethylene glycol (SWNT-PEG). When added to the culturing medium of neurons grown on a standard permissive substratum, these functionalized water soluble SWNTs were able to increase the length of various neuronal processes. By spraying a film of SWNT-PEG onto hot glass coverslips we created retainable conductive substrates on which we could culture neurons. We could specifically control the conductivity of the substrate by varying the thickness of the nanotube film. We show that conductive nanotubes are biocompatible as substrates for neuronal growth and that the specific level of conductivity is important as it affects neuronal growth and neurite outgrowth. Taken together these studies demonstrate that CNTs can be used as a scaffold/ substrate for neuronal growth and that modifications of the CNTs can be employed to modulate the arborization of neuronal processes and their outgrowth. This suggests that in the future, it may be possible to employ suitably functionalized CNTs as neural prostheses in neurite regeneration. Keywords: neuroengineering Conference: The Monte Verita' Workshop on the Frontiers in Neuroengineering, Ascona, Switzerland, 5 Sep - 9 Sep, 2010. Presentation Type: Oral Presentation Topic: Frontiers in Neuroengineering Citation: Parpura V (2010). Carbon nanotubes as modulators of neuronal growth. Front. Neuroeng. Conference Abstract: The Monte Verita' Workshop on the Frontiers in Neuroengineering. doi: 10.3389/conf.fneng.2010.10.00026 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 17 Aug 2010; Published Online: 10 Sep 2010. * Correspondence: Prof. Vladimir Parpura, University of Alabama, Department of Neurobiology, Birmingham, United Kingdom, vlad@uab.edu Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Vladimir Parpura Google Vladimir Parpura Google Scholar Vladimir Parpura PubMed Vladimir Parpura Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Supramolecular Surface Modification and Solubilization of Single‐Walled Carbon Nanotubes with Cyclodextrin Complexation

A novel approach to solubilize single-walled carbon nanotubes (SWCNTs) in the aqueous phase is described by employing supramolecular surface modification. We use cyclodextrin complexes of synthetic molecules that contain a planar pyrene moiety or a bent, shape-fitted triptycene moiety as a binding group connected through a spacer to an adamantane moiety that is accommodated in the cyclodextrin cavity. The binding groups attach to the sidewalls of SWCNTs through a pi-pi stacking interaction to yield a supramolecular system that allows the SWCNTs to dissolve in the aqueous phase through the formed hydrophilic cyclodextrin shell. The black aqueous SWCNT solutions obtained are stable over a period of months. They are characterized through absorbance, static, and time-resolved fluorescence spectroscopy as well as Raman spectroscopy, TEM, and fluorescence-decay measurements. Furthermore, the shape-fitted triptycene-based system shows a pronounced selectivity for SWCNTs with a diameter of 1.0 nm.

Photoinduced Formation and Characterization of Electron–Hole Pairs in Azaxanthylium‐Derivatized Short Single‐Walled Carbon Nanotubes

2-Azaxanthone, a nitrogenated derivative of the well-studied organic chromophore xanthone, has been covalently bound through 2-(ethylthio)ethylamido linkers to the carboxylic acid groups of short, soluble single-walled carbon nanotubes (CNTs) of 450 nm average length, and the resulting azaxanthylium-functionalized CNTs (AZX-CNT, 8.5 wt % AZX content) characterized by solution (1)H NMR, Raman and IR spectroscopy and thermogravimetric analysis. Comparison of the quenching of the triplet excited state of AZX (steady-state and time-resolved) and of the transient optical spectra of CNTs and AZX-CNT shows that the covalent linkage boosts the interaction between the azaxanthylium moiety and the short CNT units. The triplet excited state of the azaxanthylium derivative is quenched by CNT with and without covalent bonding, but when it is covalently bonded, the singular transient spectrum is compatible with the photogeneration of electron holes through electron transfer from CNT to excited azaxanthylium units.

A Stable Electroactive Monolayer Composed of Soluble Single-Walled Carbon Nanotubes on ITO

Abstract Self-assembled monolayers (SAMs) of single-walled carbon nanotubes (SWNTs) covalently attached to a (3-aminopropyl)trimethoxysilane-modified ITO surface (SAM–ITO) were prepared by the coupling reaction of the amine groups with the carboxyl groups from the soluble SWNTs, which were safely obtained via a two-step process assisted by microwave irradiation. The surface composition of the SAM–ITO was examined using X-ray photoelectron spectroscopy. The cyclic voltammetry (CV) behavior of the SAM–ITO in an organic system showed a higher capacitor charging current, which indicated the presence of a tethered SWNT monolayer. However, the CV behavior of the SAM–ITO in acidic aqueous solutions showed unexpected oxidation signals because of redox reactions involving the defects and sidewalls of soluble functionalized SWNTs. To make the CVs of the resulting SWNT monolayers more stable in acidic aqueous solutions, a conductive oligomer of tetramer aniline was additionally incorporated onto the residual carboxyl groups on the SWNTs. The UV–vis spectrum showed that the SWNT monolayer was successfully endcapped by the conductive oligomer, and atomic force microscopy images showed that the SWNTs from the self-assembled monolayer were thickened and the SWNT surfaces were roughened. The CV data showed a single reversible redox couple, which indicated a more stable state.

Interactions between Single-Walled Carbon Nanotubes (SWNT) and Ciliates: SWNT Interfere with Ciliate Ecological Functions and Ciliates Transport/Transform SWNT

AbstractWe investigated the interactions of water soluble single-walled carbon nanotubes (SWNT) with unicellular organisms, in particular a ciliated protozoan (Tetrahymena thermophila) and a bacteria (Escherichia coli), which are common constituents of natural fresh water. The ciliates could effectively incorporate SWNT into natural organic matter (NOM), and therefore into normal ecological processes. Further, SWNT induced the ciliates to egest viable bacteria in membrane-enclosed vesicles. The egested bacteria aggregates had escaped digestion by the protozoan and were able to proliferate and resist antibiotic/disinfectant treatments, which may have important implications to public health. This work highlights the importance of studies on nanoparticle ecotoxicology.

Water Soluble Single-Walled Carbon Nanotubes Inhibit Stimulated Endocytosis in Neurons

We report the use of chemically functionalized water soluble single-walled carbon nanotube (SWNT) graft copolymers to inhibit endocytosis. The graft copolymers were prepared by the functionalization of SWNTs with polyethylene glycol. When added to the culturing medium, these functionalized water soluble SWNTs were able to increase the length of various neuronal processes, neurites, as previously reported. Here we have determined that SWNTs are able to block stimulated membrane endocytosis in neurons, which could then explain the previously noted extended neurite length.

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)).

Supramolecular functionalization of single-walled carbon nanotubes with uncharged water-soluble porphyrins

We synthesized an uncharged water-soluble porphyrin, meso-tetrakis-(3,4,5-tri-{2-[2-(2-methoxy-ethoxy)-ethoxy]-ethoxy}-phenyl)-porphyrin, to solubilize single-walled carbon nanotubes (SWNTs) in aqueous solutions through supramolecular interactions. The porphyrin-SWNTs composites in aqueous solution are stable for several weeks. The porphyrin-SWNTs composites in aqueous solution have been characterized by UV-vis absorption and fluorescence spectroscopy and with atomic force microscope (AFM). The fluorescence emitted from the porphyrin ring in the aqueous solution of the porphyrin-SWNTs composite is highly quenched, evidently implying the presence of strong electronic interactions between the SWNTs and the porphyrin molecules in aqueous solution. The AFM investigation furthermore supports that the porphyrin molecules are complexed on the SWNTs side wall through π-π interaction.

Biomolecules-carbon nanotubes doped conducting polymer nanocomposites and their sensor application

A simple method for preparing bio-functionalized soluble single-walled carbon nanotubes (SWNTs) is described. Different proteins such as bovine serum albumin (BSA), cytochrome c and horseradish peroxidase (HRP) were used to solubilize low functionality SWNTs in water aided by sonication. The unbound proteins were removed by column chromatography and the SWNT-protein conjugate was used as the sole anionic dopant in electropolymerization of polypyrrole from polymerization solution at pH above the isoelectric point of the protein to provide a negative charge. The morphology of the polypyrrole with SWNT-protein dopant was found to be three-dimensional and fibrous with wide open interlocking pores in contrast to smooth and cauliflower-like for chloride doped polypyrrole. Enhanced sensor performance was demonstrated for hydrogen peroxide detection on polypyrrole/SWCNT-HRP nanocomposites modified electrode. Such nanocomposites can be potentially applied for other biosensor and bio-fuel cell applications.

Reacting soluble single-walled carbon nanotubes with singlet oxygen

Soluble single-walled carbon nanotubes were oxidized with singlet oxygen ( 1Δ g ) and the reaction progress was monitored utilizing FT-IR and UV–vis–NIR spectroscopy. The results indicate reversible covalent addition of oxygen to the walls of the nanotubes, most likely producing either the [2 + 2] or [4 + 2] cycloaddition product. Oxidative selectivity of singlet oxygen for metallic over semiconducting SWNTs was demonstrated and it is proposed that this selectivity can be utilized as a method for nanotube purification.

Debundling of single-walled carbon nanotubes by using natural polyelectrolytes

Natural polyelectrolytes (NPs), including sodium lignosulfonate, humic acid and soforth, are reported for the first time to solubilize single-walled carbon nanotubes(SWNTs) in water through a noncovalent interaction. A variety of methods, includingtransmission electron microscopy (TEM), visible–near-infrared (vis–NIR) spectra,Raman spectra and zeta potential measurements, were used to characterize theNP-dispersed SWNT solutions. It is found that the SWNTs can be exfoliatedinto thin bundles or individual tubes, even at NP concentrations as low as0.15 mg ml−1. Their high performance is attributed to the abundance of aromatic groups and ionizedgroups in the NP molecules. This method of solubilization opens the way for exploiting newnatural materials as SWNT solubilizers and may find applications in nanocomposites,self-assembly, and so forth.

Water Soluble Single-walled Carbon Nanotubes Using Inclusion Complex of Cyclodextrin with an Adamantane Derivative

Abstract Single-walled carbon nanotubes (SWNTs) were soluble in aqueous media by using host–guest complex between sodium adamantanecarboxylate (AdCNa) and β-cyclodextrin (β-CD), while SWNTs were insoluble with AdCNa or β-CD.

Retention of Intrinsic Electronic Properties of Soluble Single-Walled Carbon Nanotubes after a Significant Degree of Sidewall Functionalization by the Bingel Reaction

Sidewalls of acid-treated, shortened single-walled carbon nanotubes (SWNTs) with long alkyl chains at the open ends and defect sites have been functionalized by Bingel reaction to examine the structures and spectroscopic properties in detail for the first time. The microwave-assisted Bingel reaction has been successfully applied to the sidewall functionalization of which the reaction rate is ca. 50 times faster than that under the conventional conditions. The degree of the sidewall functionalization (one diester unit per 75−300 carbon atoms of SWNTs) was found to be controllable by changing the output power of the microwave under the same temperature. Atomic force microscopy and transmission electron microscopy showed the progressive exfoliation of the SWNT bundles by the double chemical modification. Resonant Raman and UV−vis−NIR absorption spectroscopies revealed that the electronic properties of SWNT are largely retained after a significant degree of sidewall modification by the Bingel reaction without apparent selective reactivity for metallic and semiconducting SWNTs. This is in remarkable contrast with the conventional sidewall functionalization of SWNTs leading to the loss of their electronic properties (one functional group per 10−100 carbon atoms on the sidewall). Thus, our covalent functionalization methodology can provide SWNT materials with both excellent solubility and inherent electronic properties which are highly desirable in solution-phase processing for the fabrication of SWNT-based molecular devices.

Soluble single-walled carbon nanotubes as longboat delivery systems for platinum(IV) anticancer drug design.

Amine-functionalized soluble single-walled carbon nanotubes (SWNTs) were derivatized with cisplatin prodrug conjugates as a delivery system by which to internalize multiple prodrug centers. The platinum(IV) complex, c,c,t-[Pt(NH3)2Cl2(OEt)(O2CCH2CH2CO2H)], was tethered to the surface of the carbon nanotubes through peptide linkages formed by the reaction of the SWNT-tethered amines with the carboxylate moiety. The SWNTs were taken into testicular cancer cells by endocytosis, where the drop in pH facilitates reductive release of the platinum(II) core complex, which then readily diffuses throughout the cell, as determined by platinum atomic absorption spectroscopy. The entrapment of the SWNTs within the endosomes was confirmed by fluorescence microscopy of SWNTs containing both tethered fluorescein and platinum units. The cytotoxicity of the free platinum(IV) complex increases by >100-fold when the complex is attached to the surface of the functionalized SWNTs.