Deformation of single‐walled carbon nanotubes by interaction with graphene: A first‐principles study

The interaction between single‐walled carbon nanotubes (SWNTs) and graphene were studied with first‐principles calculations. Both SWNTs and single‐layer graphene (SLG) or double‐layer graphene (DLG) display more remarkable deformations with the increase of SWNT diameter, which implies a stronger interaction between SWNTs and graphene. Besides, in DLG, deformation of the upper‐layer graphene is less than in SLG. Zigzag SWNTs show stronger interactions with SLG than armchair SWNTs, whereas the order is reversed for DLG, which can be interpreted by the mechanical properties of SWNTs and graphene. Density of states and band structures were also studied, and it was found that the interaction between a SWNT and graphene is not strong enough to bring about obvious influence on the electronic structures of SWNTs. © 2015 Wiley Periodicals, Inc.     

Hybrids of Copolymers of Fluorene and C60‐Carrying‐Carbazole with Semiconducting Single‐Walled Carbon Nanotubes

Three different copolymers of C₆₀‐carrying‐carbazole and fluorene units with different copolymer composition ratios were designed and synthesized. On the basis of photoluminescence, atomic force microscopy, and Vis‐NIR and Raman spectroscopic analysis, we found that these copolymers solubilize only semiconducting single‐walled carbon nanotubes (sem‐SWNTs) to form copolymer/sem‐SWNT hybrids, in which energy transfer from the copolymer/C₆₀ moieties to the SWNTs was revealed. By comparing two possible hybrid structures with molecular‐mechanics simulations, the greatest stabilization was found when the C₆₀ moieties lay on the sem‐SWNT surfaces.     

MEKC‐LIF analysis of rhodamine123 delivered by carbon nanotubes in K562 cells

Oxidized single‐walled carbon nanotubes (o‐SWNTs) were employed as the drug carriers to deliver the small molecules of Rhodamine123 (Rho123) into the K562 cells via physical adsorption. However, due to the fluorescence quenching of Rho123 on carbon nanotubes, the quantitative determination of Rho123 in cells is difficult. Based on the MEKC coupled with LIF detection, a quantitative approach was developed for the determination of Rho123 delivered into K562 cells by o‐SWNTs. Where the adsorbed Rho123 on o‐SWNTs could be desorbed by SDS in running buffer and be simultaneously separated with o‐SWNTs due to the differences of their electrophoretic mobility by applying the electric potential at the both ends of capillary. Using this approach, the intracellular uptakes of Rho123 in multidrug‐resistant and multidrug‐sensitive leukemia cells were quantified, and the results showed that o‐SWNTs could be used as the potential drug carriers to deliver small molecules into cells via the physical adsorption along with the circumventing of multidrug resistance of leukemia cells.     

Dispersion of single‐walled carbon nanotubes using nucleobase‐containing poly(acrylamide) polymers

Single‐walled carbon nanotubes (SWNTs) possess extraordinary properties, but suffer from poor solubility and a lack of purity. Of the possible routes available to solubilize and purify nanotube samples, the use of noncovalent functionalization is ideal as carbon nanotube properties are not deleteriously affected. A multitude of different dispersants have been investigated thus far, but of particular interest is deoxyribonucleic acid (DNA), which has previously been demonstrated to effectively separate metallic and semiconducting carbon nanotubes. Here, we investigate the ability of synthetic nucleobase‐containing poly(acrylamide) polymers to produce stable nanotube dispersions in organic solvents. Polymers bearing different nucleobase and backbone structures, as well as block copolymers with different block sequences were investigated. Polymer:SWNT mass ratios and solvent compositions were optimized for the nucleobase‐functionalized polymers, and semiconducting and metallic SWNT populations were identified by a combination of UV‐Vis‐NIR absorption, Raman, and fluorescence spectroscopy. These results demonstrate the capacity for synthetic DNA analogues to disperse SWNTs in organic media. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 2611–2617     

Carbon Nanotubes Coated Fiber for Solid‐Phase Microextraction of Bovine Fibrinogen and Bovine Serum Albumin

Carbon nanotubes (CNTs) are a kind of novel and interesting carbon material which can be used for separation and purification. In this investigation, commercial solid‐phase microextraction (SPME) fibers (PDMS) were coated with single‐wall nanotubes (SWNTs) and multi‐wall nanotubes (MWNTs) to study their adsorption and extraction ability of proteins, and bovine fibrinogen (BFg) and bovine serum albumin (BSA) were selected as the target proteins. While MWNTs adsorbed more BFg than SWNTs, SWNTs adsorbed more BSA than MWNTs. CNTs can selectively adsorb BFg in certain conditions. The fibers coated with CNTs had advantages over traditional SPME fibers in selectivity and sensitivity. It could be used to separate BFg in bovine blood plasma and also purify BFg from it. The results show that the selectivity, sensitivity and reproducibility of this method are good for real sample analysis.     

Single‐Walled Carbon Nanotubes Modified Gold Electrodes as an Impedimetric DNA Sensor

A gold surface modified with a self‐assembled monolayer of 11‐amino‐1‐undecanethiol (AUT) was used for the covalent immobilization of oxidized single‐walled carbon nanotubes (SWNTs). The as‐described SWNTs‐modified substrate was subsequently used to attach single‐stranded deoxyribonucleic acid (ssDNA) used as a substrate for DNA hybridization. Electrochemical impedance spectroscopy measurements were performed to follow the DNA hybridization process by using the redox couple [Fe(CN)₆]^3−/4− as a marker ion. Specifically, changes in charge transfer resistance obtained from the Nyquist plots were used as the sensing parameter of DNA hybridization. The substrate sensitivity towards changes in target DNA concentration, its selectivity toward different DNA sequences and its reusability are successfully demonstrated in this report.     

Grafting of aldehyde structures to single‐walled carbon nanotubes for application in phenolic resin‐based composites

Grafting of aldehyde structures to single‐walled carbon nanotubes (SWNTs) has been carried out to endow the nanotubes with appropriate wettability. The results of Fourier transform infrared (FTIR) spectroscopy, ultraviolin‐visible‐near infrared (UV‐VIS‐NIR) spectroscopy, and Raman spectroscopy provide the supporting evidence of aldehyde structures covalently attached to SWNTs. The improved wettability of aldehyde‐functionalized SWNTs (f‐SWNTs) was demonstrated by their good dispersion in organic medium, namely, ethanol and phenolic resin. The prospective covalent bonding between aldehyde structures on the surfaces of f‐SWNTs and phenolic resin makes it possible to prepare an integrated composite with the enhanced‐interfacial adhesion. The f‐SWNT composites, therefore, show much higher average values of dσ/dW_CNT and dE/dW_CNT (i.e., tensile strength and Young's modulus per unit weight fraction) compared with the composites filled with pristine SWNTs or MWNTs. The respective maxima are 9680 MPa and 320 GPa. It is thus feasible for f‐SWNTs to prepare the moderately enhanced but lightweight phenolic composites. Furthermore, the incorporation of f‐SWNTs does not limit the application of phenolic resin as insulation material. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 6135–6144, 2009     

Electorchemical Studies of Cytochrome c on Electodes Modified by Single—Wall Carbon Naotubes

Single-wall carbon nanotubes(SWNTs) modified gold electrodes were prepared by using two different methods.The electrochemical behavior of cytochrome c on the modified gold electrodes was investigated.The first kind of SWNT-modified electrode (noted as SWNT/Au electrode)was prepared by the adsorption of carboxylterminated SWNTs from DMF dispersion on the gold electrode.The oxidatively processed SWNT tips were covalently modified by coupling with amines (AET) to form amide linkage.Via Au-S chemical bonding,the self-assembled monolayer of thiol-unctionalized nanotubes on gold surface was fabricated so as to prepare the others SWNT-modified electrode (noted as SWNT/AET/Au electrode).It was shown from cyclic voltammetry cxperiments that cytochrome c exhibited direct electrochemical responses on the both electrodes, but only the current of controlled diffusion existed on the SWNT/Au electrode while both the currents of controlled diffusion and adsorption of cytochrome c occurred on the SWNT/AET/Au electrode.Photoelastic Modulation Infared Reflection Absorpthion Spectroscopy (PEM-IRRAS) and Quartz Crystal Microbalance (QCM) were employed to verify the adsorption of SWNTs on the gold electrodes.The results proved that SWNTs could enhance the direct electron transfer proecss between the electrodes and redox proteins.     

Cluster‐Based Self‐Assembly Route toward MoO3 Single‐Walled Nanotubes

MoO₃ has a unique rigid double‐layer structure, which makes it a real challenge to prepare nanotubular structures. The controlled synthesis of MoO₃ single‐walled nanotubes (SWNTs) is achieved through a cluster‐based self‐assembly route on the dodecanethiol/water interface. Various factors are studied at length, including precursor type, reaction time, temperature, pH value, and their influence on the morphology of products. The concept of “self‐assembly—from simple clusters to nanostructures” is proposed here based on preliminary results from the synthesis of MoO₃ SWNTs, which provides a new aspect for traditional synthetic chemistry of nanomaterials and polyoxometalates.     

Single‐Walled Carbon Nanotubes as Scaffolds to Concentrate DNA for the Study of DNA–Protein Interactions

Genomic DNA in bacteria exists in a condensed state, which exhibits different biochemical and biophysical properties from a dilute solution. DNA was concentrated on streptavidin‐covered single‐walled carbon nanotubes (Strep ? SWNTs) through biotin–streptavidin interactions. We reasoned that confining DNA within a defined space through mechanical constraints, rather than by manipulating buffer conditions, would more closely resemble physiological conditions. By ensuring a high streptavidin loading on SWNTs of about 1 streptavidin tetramer per 4 nm of SWNT, we were able to achieve dense DNA binding. DNA is bound to Strep ? SWNTs at a tunable density and up to as high as 0.5 mg mL^?1 in solution and 29 mg mL^?1 on a 2D surface. This platform allows us to observe the aggregation behavior of DNA at high concentrations and the counteracting effects of HU protein (a histone‐like protein from Escherichia coli strain U93) on the DNA aggregates. This provides an in vitro model for studying DNA–DNA and DNA–protein interactions at a high DNA concentration.     

Air‐tolerant Fabrication and Enhanced Thermoelectric Performance of n‐Type Single‐walled Carbon Nanotubes Encapsulating 1,1′‐Bis(diphenylphosphino)ferrocene

The thermally‐triggered n‐type doping of single‐walled carbon nanotubes is demonstrated using 1,1′‐bis(diphenylphosphino)ferrocene, a novel n‐type dopant. Through a simple thermal vacuum process, the phosphine compounds are moderately encapsulated inside single‐walled carbon nanotubes. The encapsulation into SWNTs is carefully characterized using Raman/X‐ray spectroscopy and transmission electron microscopy. This easy‐to‐handle doping with air‐stable precursors for n‐type SWNTs enables the large‐scale fabrication of thermoelectric materials showing an excellent power factor exceeding approximately 240 μW mK^?2.     

Properties of single‐walled carbon nanotube‐based poly(phenylene vinylene) electroluminescent nanocomposites

Devices with varying concentrations of single‐walled carbon nanotubes (SWNTs) dispersed in three derivatives of poly(p‐phenylene vinylene) are prepared, and their electroluminescent properties evaluated. Increasing the concentration of SWNTs improves the electrical conductivity of the nanocomposites. However, an undesired increase in the electroluminescence (EL) turn‐on voltage is observed for the hybrids, possibly due to photoluminescence quenching of excitons by the SWNTs. At relatively low concentrations of SWNTs, there is an increase in the EL lifetime; in contrast, at relatively high concentrations of SWNTs, due to photoluminescence quenching by the nanotubes, significant reduction in brightness and faster degradation of the EL performance of the devices is observed. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2011     

A Computational Study of a Single‐Walled Carbon‐Nanotube‐Based Ultrafast High‐Capacity Aluminum Battery

Exploring suitable electrode materials is a fundamental step toward developing Al batteries with enhanced performance. In this work, we explore using density functional theory calculations the feasibility of single‐walled carbon nanotubes (SWNTs) as a cathode material for Al batteries. Carbon nanotubes with hollow structures and large surface area are able to overcome the difficulty of activating the opening of interlayer spaces as observed in graphite electrode during the first intercalation cycle. Our results show that AlCl₄ binds strongly with the SWNT to result in an energetically and thermally stable AlCl₄‐adsorbed SWNT system. Diffusion calculations show that the SWNT system allows ultrafast diffusion of AlCl₄ with a more favorable inner surface diffusion than outer surface diffusion. Our charge‐density difference and Bader atomic charge analysis confirm the oxidation of SWNT upon adsorption of AlCl₄, which shows a similar behavior to the previously studied graphite cathode. The average open‐circuit voltage and AlCl₄ storage capacity increases with increasing SWNT diameter and can be as high as 1.96 V and 275 mA h g⁻¹ in (25,25) SWNT relative to graphite (70 mA h g⁻¹). All of these properties show that SWNTs are a potential cathode material for high‐performance Al batteries and should be explored further.     

Probing the Selectivity of Azomethine Imine Cycloaddition to Single‐Walled Carbon Nanotubes by Resonance Raman Spectroscopy

Selective covalent surface modification of single‐walled carbon nanotubes (SWNTs) is of great importance to various carbon nanotube‐based applications as it might offer an alternative method for enriching metallic and semiconducting nanotubes. Herein, we report on the surface modification of SWNTs through 1,3‐dipolar cycloaddition of 3‐phenyl‐phthalazinium‐1‐olate, which is a stable and reactive azomethine imine. For this reaction, microwave heating was found to be more efficient than conventional and solvent‐free heating. The sensitivity of cycloaddition to the molecular structure of SWNTs was probed using resonance Raman spectroscopy with three different laser excitations. Based on the obtained results, azomethine imine addition to the surface of nanotubes is selective for metallic and large‐diameter semiconducting SWNTs. Thermogravimetric analysis coupled with mass spectrometry showed that fragments released at high temperatures corresponded to the phenylphthalazine group, thus confirming the covalent surface functionalization. Modified SWNTs were further characterized by X‐ray photoelectron and UV/Vis‐NIR spectroscopies.     

Single‐gap Microelectrode Functionalized with Single‐walled Carbon Nanotubes and Pbzyme for the Determination of Pb2+

Lead is a highly toxic metal, which can persist in the natural environment and enrich in biological bodies. It can cause many severe diseases in the human body even at extremely low concentration. Here, we developed a new biosensor using single‐walled carbon nanotubes (SWNTs) modified with a specific Pbzyme (Pbzyme/SWNTs/FET) to detect lead ion (Pb²⁺), which can monitor the lead pollution. This biosensor used 3‐aminopropyltriethoxysilane to immobilize SWNTs on the area between the source and the drain of single‐gap microelectrode (FET), and the duplex DNA (Pbzyme) consisted of DNAzyme (GR‐5) and complementary DNA (CS‐DNA) was functionalized with the SWNTs’ surface through a peptide bond. The use of GR‐5 DANzyme and Pb²⁺ to form a stable complex structure to cleave the CS‐DNA can change radically the Pbzyme's structure on the SWNTs’ surface, which will further affect the number of carriers in SNWTs and the conductivity of the Pbzyme/SWNTs/FET. The change in conductivity can be used to evaluate the Pb²⁺ concentration. Under the optimal conditions, the relative resistances presented a positive correlation with the Pb²⁺ concentrations, showing a good linear relationship in the range of 10 pM to 50 nM, where the linear regression equation was y=10.104log [C_Pb]+5.8656, and the detection limit was 7.4 pM. Finally, the biosensor was applied to measure the Pb²⁺ contents in the soil collected from the forest grass green belt and paint, and the results were compared with the results of atomic fluorescence spectrometry.     

Experimental and Computational Investigations of the Properties of Fluorinated Single‐Walled Carbon Nanotubes

Fluorination of single‐walled carbon nanotubes by reaction with elemental fluorine at elevated temperatures provides fluorinated single‐walled carbon nanotubes (F‐SWNT), which have the highest degree of functionalization (up to F/C=1/2) of any derivatized carbon‐nanotube material reported to date. Also, F‐SWNTs have received more scrutiny than any other functionalized carbon nanotubes. This Minireview covers experimental and computational investigations of F‐SWNTs with a focus on the nature and the strength of the C–F linkage.     

Synthesis and characterization of single‐wall‐carbon‐nanotube‐doped emeraldine salt and base polyaniline nanocomposites

Nanocomposites of polyaniline (PANI) and single‐wall carbon nanotubes (SWNTs) were prepared and characterized via resonance Raman and electronic absorption spectroscopy (ultraviolet–visible/near‐infrared). The chemical synthesis of PANI was performed in the presence of SWNTs in concentrations ranging from 10 to 50 wt % (SWNT/PANI). The obtained materials were hydrophilic, homogeneous composite compounds. The chemical interaction between PANI (in the conducting emeraldine salt form and in the insulating emeraldine base form) and metallic and semiconducting nanotubes was investigated. The emeraldine salt form of the polymer was significantly stabilized in the composite in comparison with plain PANI. A selective electronic interaction process between PANI and metallic SWNTs was found. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 815–822, 2005     

Photochemical Behavior of Single‐Walled Carbon Nanotubes in the Presence of Propylamine

This report describes the photochemical behavior of single‐walled carbon nanotubes (SWNTs) in the presence of propylamine. The SWNTs are characterized by absorption and Raman spectroscopy. The spectral changes due to photoirradiation indicate that reactions occur predominantly with the metallic SWNTs and small‐diameter SWNTs. The detection of amine radicalcation species by ESR spectroscopy reveals photoinduced electron transfer from the amine to the excited SWNTs. After exposure of the photoirradiated SWNTs to air, the characteristic spectra were recovered, except for that of the small‐diameter SWNTs. The results suggest that, after photoreduction of the SWNTs, subsequent selective sidewall functionalization of the small‐diameter SWNTs occurs.     

Surfactant‐Dependent Charge Transfer between Polyoxometalates and Single‐Walled Carbon Nanotubes: A Fluorescence Spectroscopic Study

Hybridizations of redox‐active polyoxometalates (POMs) with single‐walled carbon nanotubes (SWNTs) have been widely investigated for their diverse applications. For the purpose of constructing high‐quality electronic devices, controlling charge transfer within POM/SWNT hybrids is an inevitable issue. As determined by means of fluorescence spectroscopy, electron transfer between SWNTs and a common POM dopant, phosphomolybdic acid (PMo₁₂), can be tuned simply by an alteration of nanotube surfactant type from anionic to nonionic. The mechanism is attributed to the influence of surfactant type on the stabilization of the electron donor–acceptor hybrid and effect of surfactant–nanotube interactions. These results will be important to control charge‐transport behavior in nanohybrids consisting of carbon nanotubes.     

1,3‐Dipolar cycloadditions of Stone–Wales defective single‐walled carbon nanotubes: A theoretical study

The presence of Stone‐Wales defects in single‐walled carbon nanotubes (SWNTs) not only leads to new interesting properties, but also provides opportunities for tailoring physical and chemical properties, and expands their novel potential applications. With a two‐layered ONIOM method, 1,3‐dipolar cycloadditions (1,3‐DCs) of a series of 1,3‐dipoles (azomethine ylide, nitrone, nitrile imine, nitrile ylide, nitrile oxide, and methyl azide) with Stone‐Wales defective SWNTs have been investigated theoretically for the first time. The calculated results demonstrate that the bond c , rather than the previously focused central bond a , exhibits the highest chemical reactivity among the defective sites. More interestingly, bond c is even more reactive thermodynamically and kinetically than the perfect C? C bond in SWNTs, suggesting the feasibility of utilizing 1,3‐DC reactions to separate and purify perfect and defective SWNTs. The reactivity order for nonequivalent bonds in defective sites is different from that of [1+2] cycloaddition, indicating that the reactivity order for nonequivalent bonds depends on the kind of the chemical reactions. Except azomethine ylide, nitrile ylide and nitrile imine are found to be good candidates for 1,3‐DCs upon Stone‐Wales defective SWNTs. The SW‐ A and SW‐ B defective SWNTs show different chemical reactivity toward nitrile ylide, making it possible to purify and separate the SW‐ A and SW‐ B defective SWNTs. The SWNT diameters are found to moderately influence the 1,3‐DC reactivity of both perfect and Stone‐Wales defective SWNTs, implying that Stone‐Wales defective SWNTs with different diameter would be separated experimentally through 1,3‐DC chemistry. The above 1,3‐DC reactivity can be well understood in terms of the distortion/interaction theory, which means that instead of frontier molecular orbitals interaction energy, the distortion energy controls the chemical reactivity. © 2013 Wiley Periodicals, Inc.