Nanotubes In Aqueous Solution Research Articles

Efficient dispersion of multi-walled carbon nanotubes in aqueous solution by non-covalent interaction with perylene bisimides

A selection of bolaamphiphilic perylene bisimides (PBI) were prepared from the reaction of perylenetetracarboxylic dianhydride with α-amino acids. These molecules were obtained in good yield using a simple synthetic protocol and avoiding the need for complex purification methods, a major advantage for future applications. Carbon nanotubes (CNT) were dispersed in an aqueous solution of the PBI, buffered at pH 7, and the suspension was studied by absorption and emission spectroscopy. PBI functionalized with Boc-lysine and phenylalanine led to an excellent suspension of CNT in water, stable for at least 24 h at room temperature. Theoretical calculations were used to support and explain the experimental observations.

Study on the Influence Factors of the Dispersion of Carbon Nanotubes in Aqueous Solution

In this paper, the optimal ratio of surfactant and carbon nanotubes (CNTs), the best ultrasonic time and the effects of three different surfactants were studied based on which the CNTs dispersion method was recommended. For each surfactant, optimal mix ratio of surfactant and CNTs could be found. The results of UV-Vis spectrophotometer test and centrifugation showed that the best CNTs dispersion could be obtained with OP, and the optimal mass ratio between OP and CNTs was about 0.7, and when the concentration of CNTs was 1g/L, the optimal ultrasonic time was about 1 hour. With the concentration of CNTs increased, the optimal ultrasonic time also increased.

Bio-functionalization of multi-walled carbon nanotubes

Here we present a hybrid approach to functionalize multi-walled carbon nanotubes in aqueous solution, exploring a non-covalent binding strategy. We focus on formation of hybrid complexes consisting of carbon nanotubes decorated by single stranded DNA, non-covalently attached using surfactants as intermediate layers. Unlike single walled carbon nanotubes, revealing easy side wall wrapping of DNA, we observe that wrapping of nucleic acids around multi-walled carbon nanotubes is diameter dependent.

Electrochemical Responses and Sensitivities of Films Based on Multi-Walled Carbon Nanotubes in Aqueous Solutions

Novel films consisting of multi-walled carbon nanotubes (MWCNTs) were fabricated by means of chemical vapor deposition with decomposition of either acetonitrile (ACN) or benzene (BZ) using ferrocene as catalyst. The electrochemical responses of MWCNT-based films towards the ferrocyanide/ferricyanide, [Fe(CN)6]3−/4− redox couple were probed by means of cyclic voltammetry and electrochemical impedance spectroscopy at 25.0 ± 0.5 °C. Both MWCNT-based films exhibit Nernstian response towards [Fe(CN)6]3−/4− with some slight kinetic differences. Namely, heterogeneous electron transfer rate constants lying in ranges of 2.69 × 10−2–1.7 × 10−3 and 9.0 × 10−3–2.6 × 10−3 cm·s−1 were obtained at v = 0.05 V·s−1 for MWCNTACN and MWCNTBZ, respectively. The detection limit of MWCNTACN, estimated to be about 4.70 × 10−7 mol·L−1 at v = 0.05 V·s−1, tends to become slightly poorer with the increase of the scan rate, namely at v = 0.10 V·s−1 the detection limit of 1.70 × 10−6 mol·L−1 was determined. Slightly poorer response ability was exhibited by MWCNTBZ; specifically the detection limits of 1.57 × 10−6 and 4.35 × 10−6 mol·L−1 were determined at v = 0.05 and v = 0.10 V·s−1, respectively. The sensitivities of MWCNTACN and MWCNTBZ towards [Fe(CN)6]3−/4− were determined as 1.60 × 10−7 and 1.51 × 10−7 A·L·mol−1·cm−2, respectively. The excellent electrochemical performance of MWCNTACN is attributed to the presence of incorporated nitrogen in the nanotube’s structure.

Influence of dry and wet ball milling on dispersion characteristics of the multi-walled carbon nanotubes in aqueous solution with and without surfactant

Abstract The current paper presents a new approach of attaining the optimum grinding condition of a planetary ball mill and simple method for purifying multi-walled carbon nanotubes (MWCNTs) to investigate the dispersion characteristics of MWCNTs. This work was conducted under dry and wet grinding conditions at various rotation speeds (200 rpm–500 rpm), and the dispersion characteristics of MWCNTs in aqueous solutions with and without surfactant were studied. The results were examined by scanning electron microscopy (SEM), transmission electron microscopy (TEM), particle-size analysis (PSA), UV-spectrophotometry and zeta potential (ζ) measurements. The purification results show that the structures of amorphous carbon and carbon particles of MWCNTs were completely eliminated and the tips of nanotubes opened. Moreover, both dry and wet grinding caused the lengths of the MWCNTs to be shortened with increasing rotation speed. The maximum absorbance of nanofluid was revealed to be 2.485 abs at wavelength of 253 nm for the best dispersion. The best dispersion characteristics were observed for wet grinding at a rotation speed of 500 rpm assisted by the ultrasonication dispersion of CNTs in aqueous solutions with surfactant.

Development of a Novel Composite Material with Carbon Nanotubes Assisted by Self-Assembled Peptides Designed in Conjunction with β-Sheet Formation

A novel composite material is developed with single-walled carbon nanotubes (SWCNTs) and artificially designed peptides, and its chemical and physicochemical characteristics are evaluated with an aim toward biomedical application. The peptides were designed to form a β-sheet structure that would be suitable for wrapping SWCNTs. The complex of SWCNTs and peptide (SWCNT-peptide) showed good dispersibility in aqueous media and was considerably stable even in the absence of an excess amount of peptide in the media. The formation of SWCNT-peptide was confirmed by its performance in water, atomic force microscopy and transmission electron microscopy observation, and molecular modeling. The possibility of introducing various functions to SWCNT-peptide was also demonstrated by several methods, such as introduction of special amino acids, chemical modification, and additional complex formation based on electrostatic interaction. These results suggest the potential of the SWCNT-peptide complex as a molecular platform on which a desirable structure and/or function can be constructed for biomedical and industrial application.

Achieving Ultrahigh Concentrations of Fluorescent Single‐Walled Carbon Nanotubes Using Small‐Molecule Viscosity Modifiers

Surfactant dispersion is a well-established method for stabilizing individual single-walled carbon nanotubes in aqueous solutions. However, achieving high concentrations of individually dispersed nanotubes with this technique has proven challenging. Here it is demonstrated that the introduction of viscosity-enhancing compounds such as sucrose can increase the maximum concentration of surfactant-dispersed single-walled carbon nanotubes by more than a factor of 100 while still retaining the optical properties of individual nanotubes. When these solutions are used as inks for methods such as inkjet printing, they retain their fluorescent properties even after the ink has dried.

Biotemplated synthesis of hollow double-layered core/shell titania/silica nanotubes under ambient conditions.

Bacterial flagella, protein nanotubes (∼15 nm wide) detached from Salmonella typhimurium bacteria, are used to template the formation of titania/silica core/shell double-layered nanotubes in aqueous solution under ambient conditions through a sol-gel process. The thickness of each layer is tunable by varying the concentration of precursor solutions or reaction times. Upon heating, the flagella can be removed and the inner titania layer can be transformed into a nanocrystalline layer supported by the outer silica sheath. Nanotubes with different inner pore diameters and morphologies could be templated by other bionanofibers such as M13 phage and bacterial pili. This work shows that bionanofibers can be used as a universal biotemplate for the green synthesis of nanotubes with tunable wall thicknesses.

Decolorisation of Reactive Red 120 Dye by Using Single‐Walled Carbon Nanotubes in Aqueous Solutions

Dyes are one of the most hazardous chemical compound classes found in industrial effluents and need to be treated since their presence in water bodies reduces light penetration, precluding the photosynthesis of aqueous flora. In the present study, single‐walled carbon nanotubes (SWCNTs) was used as an adsorbent for the successful removal of Reactive Red 120 (RR‐120) textile dye from aqueous solutions. The effect of various operating parameters such as initial concentration of dye, contact time, adsorbent dosage and initial pH was investigated in order to find the optimum adsorption conditions. Equilibrium isotherms were used to identify the possible mechanism of the adsorption process. The optimum pH for removing of RR‐120 dye from aqueous solutions was found to be 5 and for this condition maximum predicted adsorption capacity for RR‐120 dye was obtained as 426.49 mg/g. Also, the equilibrium data were also fitted to the Langmuir, Freundlich and BET equilibrium isotherm models. It was found that the data fitted to BET (R2 = 0.9897) better than Langmuir (R2 = 0.9190) and Freundlich (R2 = 0.8819) model. Finally it was concluded that the single‐walled carbon nanotubes can be used for dye removal from aqueous solutions.

Fluorophore and Dye-Assisted Dispersion of Carbon Nanotubes in Aqueous Solution

DNA short oligo, surfactant, peptides, and polymer-assisted dispersion of single-walled carbon nanotube (SWCNTs) in aqueous solution have been intensively studied. It has been suggested that van der Waals interaction, π-π stacking, and hydrophobic interaction are major factors that account for the SWCNTs dispersion. Fluorophore and dye molecules such as Rhodamine B and fluorescein have both hydrophilic and hydrophobic moieties. These molecules also contain π-conjugated systems that can potentially interact with SWCNTs to induce its dispersion. Through a systematic study, here we show that SWCNTs can be dispersed in aqueous solution in the presence of various fluorophore or dye molecules. However, the ability of a fluorophore or dye molecule to disperse SWCNTs is not correlated with the stability of the fluorophore/dye-SWCNT complex, suggesting that the on-rate of fluorophore/dye binding to SWCNTs may dominate the efficiency of this process. We also examined the uptake of fluorophore molecules by mammalian cells when these molecules formed complexes with SWCNTs. The results can have potential applications in the delivery of poor cell-penetrating fluorophore molecules.

Effect of grinding speed changes on dispersibility of the treated multi-walled carbon nanotubes in aqueous solution and its thermal characteristics

For the purpose of increasing the dispersibility and thermal conductivity of fluid containing nanoparticles, raw multi-walled carbon nanotubes (MWCNTs) were treated by strong acids. The purified structures were dispersed into aqueous solution by using wet grinding conditions at various rotation speeds (300–600rpm) merged with ultrasonication. The particle size analyzer reveals that the agglomerated size of ground particles at rotation speed of 300rpm was 39.811μm. Nevertheless, the agglomerated size of particles significantly decreased to 11.482μm after grinding at rotation speed of 600rpm. The maximum absorbance (4.0 abs at wavelength of 300nm) and highest thermal conductivity (0.6074W/mk at 30°C) of the suspension corresponds to the grinding speed of 600rpm assisted by ultrasonication dispersion. From the overall results, grinding method with high rotation speed plays can be significantly increased both the dispersibility and thermal conductivity of MWCNTs in aqueous solution.

Removal of Bisphenol A and 17β-Estradiol by Single-Walled Carbon Nanotubes in Aqueous Solution: Adsorption and Molecular Modeling

Single-walled carbon nanotubes, both before (SWNTs) and after treatment (t-SWNTs) with acidified ammonium persulfate, were successfully used to adsorb bisphenol A (BPA) and 17β-estradiol (E2) from aqueous systems. The surface characteristics of the SWNTs and t-SWNTs were analyzed by measuring their surface charge and by imaging their morphological properties through transmission electron microscopy. The extent of defects on the SWNT scaffold generated through acid etching was analyzed by Raman spectroscopy. A total of 19.4, 15.4, and 14.3 mg/g of BPA was adsorbed on SWNTs, while a total of 8.0, 6.4, and 5.1 mg/g was adsorbed on t-SWNTs with a 72-h contact time at 280, 295, and 315 K, respectively. A significantly high fraction of E2 (27.2 mg/g) was absorbed by both SWNTs and t-SWNTs, as compared to BPA. The adsorption kinetics was analyzed using a pseudo-second-order model. Sorption experiments showed that t-SWNTs adsorbed less than half as much BPA as SWNTs, but their E2 adsorption was similar. The sorption mechanism was investigated by performing molecular-level calculations. Adsorption energies calculated using density functional theory show preferential sorption of E2 to SWNTs and graphene (−26.2 kcal/mol on SWNT and −34.1 kcal/mol on graphene) compared to BPA (−17.1 kcal/mol on SWNT and −22.5 kcal/mol on graphene), which were consistent with the experimental findings. Thus, ab initio calculations can mechanistically explain the adsorption differences of BPA and E2 on SWNTs.

Effect of the molecular weight and the concentration of polyoxyethylene nonylphenyl ether on the dispersion efficiency of single-walled carbon nanotubes in aqueous solutions

We have investigated the dispersion efficiency of single-walled carbon nanotubes (SWCNTs) in polyoxyethylene nonylphenyl ether (PNE) solutions with various PNE molecular weights and concentrations by using Raman, photoluminescence, and absorption spectroscopy. The heavier the PNE’s are, as long as their molecular weight is greater than 441, the better capability of dispersing SWCNTs they exhibit for fixed PNE concentrations. For heavier PNE’s, the dispersion efficiency monotonically increases as their concentration increases up to 3 wt%.

Adsorption of perchlorate onto raw and oxidized carbon nanotubes in aqueous solution

Perchlorate (ClO4−) is an emerging trace contaminant. The adsorption of ClO4− on raw and oxidized carbon nanotubes (CNTs) was investigated to elucidate the affinity mechanism of CNTs with anion pollutants. The adsorption of ClO4− into different CNTs increased in the order multi-walled CNTs<single-walled CNTs<double-walled CNTs (DWCNTs). Co-existing anions (SO42−, NO3−, Cl−) significantly weakened ClO4− adsorption, while the co-existence of Fe3+ and cetyltrimethylammonium cations increased ClO4− adsorption 2- to 3-fold. ClO4− adsorption was promoted by oxidized DWCNTs due to the introduction of more oxygen-containing functional groups, which served as additional adsorption sites. The pH values significantly affected the zeta potential of raw and oxidized DWCNTs and thus ClO4− adsorption. The pH-dependent curves of ClO4− adsorption on CNTs were distinct from those of conventional sorbents (e.g., activated carbon and resin). Maximum ClO4− adsorption occurred at pH=the isoelectric point (pHIEP)+0.85 rather than at pH<pHIEP, which cannot be explained by electrostatic interactions alone. Hydrogen bonding is proposed to be a dominant mechanism at neutral pH for the interaction of ClO4− with CNTs, and variations of ClO4− affinity with CNTs in different pH ranges are illustrated.

Dispersant Effects in the Selective Reaction of Aryl Diazonium Salts with Single-Walled Carbon Nanotubes in Aqueous Solution

Current methods of synthesis for carbon nanotubes (CNTs) usually produce heterogeneous mixtures of different nanotube diameters and thus a mixture of electronic properties. Consequently, many techniques to sort nanotubes according to their electronic type have been devised. One such method involves the chemical reaction of CNTs with aryl diazonium salts. Here we examine the reactions of electric arc produced CNTs (dispersed by a variety of surfactants and polymers in aqueous solution) with 4-bromo-, 4-nitro-, and 4-carboxybenzenediazonium tetrafluoroborate salts in order to find conditions for maximum selectivity. Reactions were monitored through the semiconducting S22 and metallic M11 transitions in the UV–vis–NIR absorbance spectra of the nanotube dispersions. Selectivity was observed to depend heavily on the type of surfactant, the type of diazonium salt and its concentration, the reaction temperature, and the solution pH. Additionally, the surfactant concentration was found to exert a significant influence as the dediazoniation product yields are affected by this parameter. For certain combinations of surfactant and diazonium salt the selectivity is markedly improved, particularly in dispersions of nonionic surfactants Pluronic F-127 and Brij S-100, which are similar in structure. Smaller diameter HiPCO nanotubes were better functionalized in dispersions of Triton X-405. The greater selectivity afforded by these poly(ethylene oxide) containing polymers is postulated to arise from electron donation provided by their ether oxygens. The ionic surfactant sodium dodecyl sulfate was found to display unique behavior in that semiconducting nanotubes were preferentially functionalized at natural pH, likely due charge localization interactions with the surfactant.

Facile and mild solution synthesis of Cu2O nanowires and nanotubes driven by screw dislocations

We report a green synthesis of Cu(2)O nanowires and nanotubes in aqueous solution by reducing Cu(2+) to Cu(+) with glucose or fructose via Fehling's reaction. The screw dislocation-driven growth of Cu(2)O nanowires and nanotubes is confirmed by imaging the dislocation contrast, the Eshelby twist associated with dislocations and the spontaneously formed hollow nanotubes.

Absorption Properties of Hybrid Composites of Gold Nanorods and Functionalized Single‐Walled Carbon Nanotubes

We report on the optical properties of fabricated nanohybrid structures containing Au nanorods and functionalized single‐walled carbon nanotubes in aqueous solutions. In particular, the absorption spectra of these hybrid materials are studied as a function of the concentration of the functionalized single‐walled carbon nanotubes as well as the evolution time following preparation. The absorption spectra show a red shift of the longitudinal plasmon mode of the Au nanorods along with the emergence of broadened structures at wavelengths between 1000 and 1100 nm. These results, supported by TEM images, indicate the self‐assembly of the Au nanorods forming on the sidewalls of the functionalized SWNTs driven by polyelectrolyte interactions.

Double Stimuli-Responsive Copolymer Stabilizers for Multiwalled Carbon Nanotubes

A unique copolymer stabilizer is presented that can be used to stabilize multiwalled carbon nanotubes in aqueous solution to form "smart" dispersions. They showed double stimuli-responsive behavior (in dependence of temperature and ionic strength) and allowed for accurate control of the transition (exfoliated → agglomerated) temperature of nanotubes over a wide temperature range. In spite of its effective dispersion strength, the copolymer was easily synthesized in one step via free radical copolymerization of N-isopropylacrylamide and 1-ethyl-3-vinylimidazolium bromide.

Parametric analysis of sonication and centrifugation variables for dispersion of single walled carbon nanotubes in aqueous solutions of sodium dodecylbenzene sulfonate

Dispersion of single-walled carbon nanotubes with the aid of surfactants has become a common procedure for generating aqueous solutions containing a high fraction of individualized nanotubes, though methodologies vary greatly among the literature. A parametric study was performed in order to analyse the effect of ultracentrifugation temperature, duration and applied force on dispersions of arc-discharge nanotubes in sodium dodecylbenzene sulfonate. The amount of metallic impurities remaining after varying levels of centrifugation was investigated by electron microscopy and X-ray spectroscopy. The effect of intensity and duration of exposure to ultrasound was also examined. Solutions were characterized with UV–vis–NIR absorbance spectroscopy, Raman spectroscopy and atomic force microscopy in order to find optimal ranges of these parameters for this particular system. In general, optimal conditions were accomplished via tip sonication at a power below 0.6 W mL −1 to deliver around 450 J mL −1 to the solution, followed by centrifugation at ∼120 × 10 3 g for 1–2 h. The scission of nanotubes was found to follow a power law such that the average length of the ensemble decreased proportional to t −0.38 under continuous tip sonication, while the relationship between mean nanotube length and the Raman D:G ratio was approximately linear for both 1.58 and 2.33 eV excitation.

Kinetic resistance of carbon nanotubes in aqueous solution

By using the molecular dynamics (MD) method, the deceleration of (5,5), (7,7), (10,10) and (5,5)/(10,10) carbon nanotubes is first simulated in aqueous solution; their curves of resistance/velocity and resistance/Reynolds (Re) number are also obtained; then the MD results are compared with the macroscopic fluid dynamics (FD) ones of circular cylinder in aqueous solution for low Re numbers. It is shown that, in aqueous solution, the kinetic resistance of the carbon tubes only rests with their Re number, that, under the low Re numbers, the resistance of the carbon tubes in aqueous solution is higher than the macroscopic FD results by several ten times, and that the kinetic resistance of carbon tubes can be estimated through the macroscopic FD results multiplied by (17.17/0.19 Re).