Carbon Nanotube Surfactant Research Articles

Comparative investigation of carbon nanotubes dispersion using surfactants: A molecular dynamics simulation and experimental study

Poor dispersion is a major obstacle limiting the practical application of carbon nanotubes (CNTs) in composites. A comparative analysis of the dispersion ability of six representative surfactants for CNTs was conducted using both molecular dynamics (MD) simulations and experimental investigations. The dispersion stability of the surfactant-assisted CNTs was characterised via ultraviolet–visible spectroscopy, surface potential analysis, and transmission electron microscope. The chemical structures of the surfactants and CNTs-surfactant ratios directly affected the adsorption behaviours of surfactants on CNTs surface, thus exerting significant impacts on the final dispersion effect. The interaction energy analysis showed that Triton X-100 and sodium dodecyl benzenesulfonate (SDBS) exhibited the strongest interaction with CNTs with respect to other surfactants, whereas sodium dodecyl sulfate (SDS) displayed the weakest interaction. The van der Waals forces were the main driving forces of this adsorption process. Several structural factors, such as the presence of benzene rings and long alkyl chains, were important and favourable in enhancing the adsorption efficiency of surfactants on CNTs surface. The MD simulation results also revealed that different concentrations of surfactants in the system led to different adsorption behaviours, as low amounts of surfactants tended to exhibit random adsorption without a particular orientation on CNTs surface. Based on the experimental results, Triton X-100 and SDBS showed the strongest dispersion ability, which was consistent with the MD calculation results. Notably, excess amounts of surfactants above the optimum amount caused the entanglement and agglomeration of CNTs owing to the interaction between unfavourable micelles. This study provides an effective guidance for the selection of optimal surfactants for CNTs dispersion.

(Invited) A Cleanly Removable Surfactant for Carbon Nanotubes

Surfactants are widely used to stabilize single-walled carbon nanotubes (SWCNTs) and many other nanomaterials to facilitate their solution processing and device integration. However, it is notoriously difficult to subsequently remove these molecules when they are no longer needed. Methods to remove surfactant, including rinsing with organic solvents, acidic oxidation and annealing at high temperature, are inefficient to recover their intrinsic electrical and optical properties or even damage these nanomaterials. Here, we report the synthesis of a new carbon nanotube surfactant that can be cleanly removed by a two-step post-annealing process at a relatively low temperature. Additionally, this tailored surfactant is as efficient as sodium deoxycholate at individually dispersing SWCNTs in water. The insight may help guide the choice or design of surfactants for nanomaterials applications such as sensors, printed electronics, and high performance devices, where the clean removal of the dispersant is key to enhanced performance.

Effects of Temperature and Shear on the Adsorption of Surfactants on Carbon Nanotubes

Carbon nanotube suspensions in water can be stabilized with the use of surfactants. However, when a suspension is exposed to harsh conditions, the surfactants might detach from the carbon nanotube (CNT) surface leading to CNT agglomeration and precipitation. In order to explore temperature effects on the suspension, the surfactant adsorption isotherms of an ionic surfactant (alkylpropoxy sulfate, alfoterra 123-8s) and a nonionic surfactant (secondary alcohol ethoxylate, tergitol 15-s-40) on a CNT are obtained at various temperatures using dissipative particle dynamics (DPD) simulations. The effects of shear stresses, such as those experienced by the CNT–surfactant suspension when it passes through pumps, are also explored by applying different levels of constant shear on the suspension. It is seen that there is good agreement between the DPD results and the Langmuir model for the adsorption of both alfoterra and tergitol on CNTs. The detachment of the surfactant from the nanotubes occurs with the detachme...

Polyether from a biobased Janus molecule as surfactant for carbon nanotubes

A new polyether (PE) was prepared from a biobased Janus molecule, 2-(2,5-dimethyl-1H-pyrrol-1-yl)-1,3- propanediol (serinol pyrrole, SP). SP was synthesized with very high yield (about 96%) and high atom efficiency (about 80%) by reacting a biosourced molecule, such as serinol, with 2,5-hexanedione in the absence of solvent or catalyst. The reaction of SP with 1,6-dibromohexane led to PE oligomers, that were used as surfactants for multiwalled carbon nanotubes (MWCNT), in ecofriendly polar solvents such as acetone and ethyl acetate. The synergic interaction of aromatic rings and oxyalkylene sequences with the carbon allotrope led to dramatic improvement of surfactant efficiency: only 24% of SP based PE was extracted with ethyl acetate from the adduct with MWCNT, versus 98% of a typical pluronic surfactant. Suspensions of MWCNT-PE adducts in ethyl acetate were stable for months. High resolution transmission electron microscopy revealed a film of oligomers tightly adhered to MWCNT surface.

분산제의 종류 및 사용량에 따른 CNT 보강 시멘트 복합체의 강도변화

Sung-Jin Ha Su-Tae Kang Jong-Han LeeAbstractThis study was aimed to investigate the difference in strength of Carbon Nanotube (CNT) reinforced cement mortars with different types of surfactants and doses. In the experimental program, CTAB, SDBS and TX10 which were common surfactants adopted to improve CNTs dispersion in fabricating CNT composites in many industrial fields were included and superplasticizer which was revealed to be effective to disperse CNTs especially in CNT reinforced cementitious composites were added as well.Superplasticizer presented less strength reduction in cement mortar and more strength gain by adding CNTs among four types of surfactants. Higher dosage of superplasticizer caused lower strength of cement mortar. Adding CNTs of 0.4 wt.% or less to cementdidn’t show strength enhancement by adding CNTs but 0.8 wt.% of CNTs resulted in strengthening effect after all. Finally, a combination of 0.1 wt.% of CNTs, superplasticizer and sonication treatment could lead to strength improvement by adding CNTsin cement mortar.Keywords : Carbon Nanotube surfactant, Superplasticizer, Dispersion, Strength

Highly efficient hyperbranched CNT surfactants: influence of molar mass and functionalization.

End-group-functionalized hyperbranched polymers were synthesized to act as a carbon nanotube (CNT) surfactant in aqueous solutions. Variation of the percentage of triphenylmethyl (trityl) functionalization and of the molar mass of the hyperbranched polyglycerol (PG) core resulted in the highest measured surfactant efficiency for a 5000 g/mol PG with 5.6% of the available hydroxyl end-groups replaced by trityl functions, as shown by UV-vis measurements. Semiempirical model calculations suggest an even higher efficiency for PG5000 with 2.5% functionalization and maximal molecule specific efficiency in general at low degrees of functionalization. Addition of trityl groups increases the surfactant-nanotube interactions in comparison to unfunctionalized PG because of π-π stacking interactions. However, at higher functionalization degrees mutual interactions between trityl groups come into play, decreasing the surfactant efficiency, while lack of water solubility becomes an issue at very high functionalization degrees. Low molar mass surfactants are less efficient compared to higher molar mass species most likely because the higher bulkiness of the latter allows for a better CNT separation and stabilization. The most efficient surfactant studied allowed dispersing 2.85 mg of CNT in 20 mL with as little as 1 mg of surfactant. These dispersions, remaining stable for at least 2 months, were mainly composed of individual CNTs as revealed by electron microscopy.

Dynamic Behavior of Carbon Nanotube and Bio-/Artificial Surfactants Complexes in an Aqueous Environment

We examined the characteristics and behaviors of the carbon nanotube (CNT) and surfactants complexes in an aqueous environment using computational techniques to elucidate the effects of surfactants used to disperse the CNTs in toxicity studies of CNTs. We found that the cohesive energy per one adsorbed surfactant molecule of the CNT–surfactants complex depends on the type and the amount of the adsorbed surfactant molecules on the CNT surface. The CNT–dipalmitoyl phosphatidylcoline (DPPC; a primary component of human lung surfactants) complex was more energetically stable than the CNT–Tween 80 (an artificial surfactant often used to disperse CNTs) complex by 20–60 kJ/mol. The average cohesive energy of the complexes was 330 kJ/mol. Such high cohesive energy suggests that the CNT molecule that was once covered by surfactant molecules is unlikely to return to its original bared form. Furthermore, we found that reactions of adsorption and desorption of surfactant molecules occur on the CNT surface in a time s...

Pool boiling characteristics of multiwalled carbon nanotube (CNT) based nanofluids over a flat plate heater

This paper is mainly concerned about the pool boiling heat transfer behavior of multi-walled carbon nanotubes (CNTs) suspension in pure water and water containing 9.0% by weight of sodium lauryl sulphate anionic surfactant (SDS). Three different concentrations of 0.25%, 0.5% and 1.0% by volume of CNT dispersed with water and water containing 9.0% by weight of sodium lauryl sulphate anionic surfactant (SDS) were prepared and boiling experiments were conducted over a stainless steel flat plate heater of size 30mm2 and 0.44mm thickness. The test results exhibit that the addition of carbon nanotubes increases boiling heat transfer coefficients of the base fluids. At a given heat flux of 500kW/m2, the enhancement of heat transfer coefficient was found to be 1.5, 2.6 and 3.0 times of water corresponding to 0.25%, 0.5% and 1.0% concentration of CNT by volume in water, respectively. In water–CNT–surfactant nanofluid, it was found that 0.5% of CNT concentration gives the highest enhancement of 1.7 compared with water. In both water and water–surfactant base fluids, it was observed that the enhancement factor for 0.25% of CNT first increases up to the heat flux of 66kW/m2 and then decreases for higher heat fluxes. Further, the overall heat transfer coefficient enhancement in the water–CNT nanofluids is approximately two times higher than that in the water–CNT–surfactant nanofluids. With increasing heat flux, however, the enhancement was concealed due to vigorous bubble generation for both water–CNT and water–CNT–surfactant nanofluids. Foaming was also observed over the liquid-free surface in water–CNT–surfactant nanofluids during the investigation. No fouling over the test-section surface was observed after experimentation.

A Universal Ultracentrifuge Spectrometer Visualizes CNT–Intercalant–Surfactant Complexes

Interacting solutes form mUltiple associates and usually mask each other in ensemble characterization. They are susceptible to preparation artefacts in the single-molecule techniques commonly applied. To overcome the problem of bulk characterization of a single-walled carbon nanotube (CNT) dispersion with a novel surfactant-intercalant mixture, we obtain color movies of fractionation under extreme gravity, such that each colloidal component is characterized independently. We combine the unique fractionation power of ultracentrifugationl!) with full absorption spectra etA) at each radial position r at each time step t during the sedimentation process.[2,3) In ref. [8], ligand attachment CNTs was studied with the Beckman model XLA centrifuge, which tracks only e(r,t) at a single wavelength, requiring extended modeling for analysis. Our spectrometer/CCD opticsI2.3) adds a third dimension and generates wavelength-resolved movies of the centrifuge fractionation e(r,t,},). This allows independent ligand and CNT tracking without hydrodynamic modeling. We identify the interactions in unpurified intercalant-surfactant-CNT dispersions and obtain the unexpected proof of four coexisting heteroassociates by a novel model-free evaluation. Solubilization of carbon nanotubes is of primary importance to increase the processability of this unique class of materials. Despite the progress in separating and sorting SWCNTs by electrophoresis, density gradient ultracentrifugation or chromatography, CNT-based technology has not yet been realized on a commercial scale, as the CNT separation is limited to individualized nanotubes.14,S) It has previously been shown that designed water-soluble perylene bisimide derivatives such as 1 are excellent CNT surfactants, yielding CNT dispersions with up to 73 % of the CNTs stably dispersed and containing 60% of in-

Enzyme‐Activated Surfactants for Dispersion of Carbon Nanotubes

N-Fluorenyl-9-methoxycarbonyl-protected amino acids are used as surfactants for carbon nanotubes and their interactions are modeled using quantum mechanical computations. These surfactants are then converted into enzymatically activated CNT surfactants that create homogeneous aqueous nanotube dispersions on-demand under constant and physiological conditions

A novel biomimetic polymer as amphiphilic surfactant for soluble and biocompatible carbon nanotubes (CNTs)

Novel amphiphilic diblock copolymer, cholesterol-end-capped poly(2-methacryloyloxyethyl phosphorylcholine) (CPMPC), which has poly(2-methacryloyloxyethyl phosphorylcholine) (PMPC) as hydrophilic segment and cholesterol as hydrophobic segment, was specially designed as amphiphilic surfactant to achieve water-soluble and biocompatible carbon nanotubes (CNTs). The pristine CNTs were facilely dispersed via non-covalently binding the zwitterionic phosphorylcholine-based amphiphile onto the surfaces of the CNTs. It is interesting to find that CPMPC shows better CNTs solubilizing ability compared with the surfactant of pyrene-end-capped poly(2-methacryloyloxyethyl phosphorylcholine) (PPMPC). The biocompatibility of the CPMPC stabilized CNTs was evaluated using cholesterol-end-capped poly(2-(dimethylamino) ethyl methacrylate) (CPDMAEMA), cholesterol-end-capped poly(acrylic acid) (CPAA) and cholesterol-end-capped poly(ethylene oxide) (CPEG) as surfactants for CNTs as controls. While CPDMAEMA stabilized CNTs and CPAA stabilized CNTs showed obvious cytotoxicity, cytotoxicity of this novel zwitterionic phosphorylcholine-based amphiphile stabilized CNTs was not observed as indicated by cell culture. The biocompatible CNTs represent an excellent nano-object for potential biomedical applications.