共查询到20条相似文献,搜索用时 31 毫秒
1.
Chen Q Saltiel C Manickavasagam S Schadler LS Siegel RW Yang H 《Journal of colloid and interface science》2004,280(1):91-97
The aggregation behavior of colloidal single-walled carbon nanotubes (SWNT) in dilute aqueous suspensions was investigated using a novel light scattering measurement technique. The aggregation of SWNT in three suspensions was examined: (1) nanotubes after acid treatment; (2) as-received nanotubes stabilized by a nonionic surfactant; and (3) acid-treated nanotubes with nonionic surfactant. Continuous light scattering measurements of the SWNT suspensions (probing the 38-436 nm length scale) made over two weeks showed that the nanotubes in each sample formed networks with fractal-like structures. The as-received nanotubes were stable over the measurement period, while the acid-treated nanotube suspension showed greater dispersion variability over time, yielding looser structures at large length scales and more compact structures at smaller length scales. The addition of surfactant to the acid-treated suspension significantly enhanced nanotube dispersion. 相似文献
2.
Chen Ma Xi‐Zhi Yang Li‐Jun Ji Chan Zhang Ji Liang 《Journal of Dispersion Science and Technology》2013,34(4):502-507
It has been proven that electric fields can be used to improve the dispersion and alignment of carbon nanotubes (CNTs) in liquid media. In this article, an AC electric field is applied to blending of suspension of CNTs in methlmethacrylate (MMA) monomer during the polymerization of the MMA monomer initiated by 2 2‐azoisobytyronitrile (AIBN). Polymethlmethacrylate (PMMA) composites with macroscopic CNTs networks are prepared. It is found that morphologies of the CNTs networks are strongly dependent on the electric field parameters and polymerization conditions, such as the voltage, frequency, exerting time of the electric field, shapes of the electrodes for introducing the electric field, and the polymerization temperature. Increased voltage and frequency are found to be beneficial for the improvement of the CNTs dispersion and alignment, while fine CNTs networks are formed with optimized polymerization temperature and exerting time of the electric field. 相似文献
3.
Tang C Zhou T Yang J Zhang Q Chen F Fu Q Yang L 《Colloids and surfaces. B, Biointerfaces》2011,86(1):189-197
Ultrasonication is often used to disperse nano-particles in aqueous solution. However, a good dispersion of nano-particles in aqueous solution is not always achieved, due to the fact that incoming ultrasonicwaves in liquid are usually reflected and damped at the gas/liquid interface. In this work, we report a so-called wet-grinding assisted ultrasonication (GU) method, in which wet-grinding of multi-walled carbon nanotubes (MWCNTs) in chitosan solution is carried out before ultrasonication. The dispersions of MWCNTs were characterized by visual comparison, UV/vis spectroscopy, and scanning electron microscopy (SEM). The results demonstrate that the dispersion quality of chitosan/MWCNT suspension prepared by wet-grinding assisted ultrasonication is much better than that by ultrasonication or wet-grinding alone. It was found that wet-grinding could improve the water wettability of MWCNTs and eliminate the barrier of air layer around MWCNTs to ultrasonicwaves. Meanwhile, the composite from the chitosan/MWCNTs suspension prepared by GU method has an obvious improvement in mechanical property compared to pure chitosan. This simple method for integrating MWCNTs and biocompatible chitosan into a homogeneous dispersion may have great potential application in biotechnology, such as preparing composite materials for medicine, bio-fiber, biosensor, antibacterial coating, and cell cultivation. 相似文献
4.
如果能在无需聚合物或共价官能团辅助的条件下, 将多壁碳纳米管(MWNTs)高浓度地分散在乙醇中, 那么向各种复合材料引入MWNTs的过程就会更加便捷. 为此, 制备了多种含有表面活性剂的多壁碳纳米管乙醇悬浮液并对比考查了它们的稳定性. 非离子表面活性剂Triton X-100 和Tween 65显示出了在乙醇中分散悬浮高浓度MWNTs的能力, 能够使1.0 g·L-1 MWNTs乙醇悬浮液的上层清液经240 h后浓度仍分别在0.50和0.35 g·L-1以上. 这样长时间稳定的、没有聚合物或共价官能团辅助的MWNTs乙醇悬浮液, 其浓度比文献报道的值高. 进一步探讨了这些非离子表面活性剂分子结构对于分散MWNTs的优势, 并直观给出了其吸附于碳纳米管表面的可能形式. X射线光电子能谱和透射电子显微镜的表征结果都证实了表面活性剂分子吸附于碳纳米管表面. 相似文献
5.
In this paper, we present the analyses of surface tension of surfactant-stabilized dispersions of carbon nanotubes. This method allows one to study interactions of carbon nanotubes with surfactants at different levels of nanotube loading when optical methods fall short in quantifying the level of nanotube separation. Sodium dodecyl sulfate was used as a stabilizing agent to uniformly disperse single-walled carbon nanotubes in an aqueous media. We show that surface tension is very sensitive to small changes of nanotube and surfactant concentrations. The experimental data suggest that, at moderate concentrations, surfactant displaces carbon nanotubes from the air-water interface and the nanotubes are mostly moved into the bulk of the liquid. By analyzing the surface tension as a function of surfactant concentration, we obtained the dependence of critical micelle concentration on nanotube loading. We then constructed the adsorption isotherm for dodecyl sulfate on carbon nanotubes and bundles of carbon nanotubes. The results of these experiments enabled us to extend the phase diagram of the produced dispersions to a broader range of surfactant and nanotube concentrations. 相似文献
6.
Blackburn JL Engtrakul C McDonald TJ Dillon AC Heben MJ 《The journal of physical chemistry. B》2006,110(50):25551-25558
We examine the Breit-Wigner-Fano (BWF) line shape in the Raman spectra of carbon single-wall nanotubes (SWNTs) dispersed in aqueous suspensions. Bundling and electronic effects are studied by comparing undoped SWNTs (C-SWNTs) to boron-doped nanotubes (B-SWNTs) in a variety of different surfactant solutions. For SWNTs dispersed with nonionic surfactants that are less effective in debundling than ionic surfactants, the Raman spectra retain a large BWF feature. However, we demonstrate that even for SWNTs dispersed as isolated nanotubes by ionic surfactants the BWF feature may be present and that the intensity of the BWF is highly sensitive to the specific surfactant. In particular, surfactants with electron-donating groups tend to enhance the BWF feature. Also, modification of the SWNT electronic properties by boron doping leads to enhanced surfactant dispersion relative to undoped C-SWNTs and also to modification of the BWF feature. These observations are in agreement with reports demonstrating an enhancement of the BWF by bundling but also agree with reports that suggest electron donation can enhance the BWF feature even for isolated SWNTs. Importantly, these results serve to caution against using the lack or presence of a BWF feature as an independent measure of SWNT aggregation in surfactant dispersions. 相似文献
7.
Katsufumi Tanaka Yutaka Fujioka Atsushi Kubono Ryuichi Akiyama 《Colloid and polymer science》2006,284(5):562-567
In situ optical observations were performed for suspensions composed of carbon nanoparticles under the sinusoidal electric
field with an amplitude around 20 kV/mm (volt per micrometer) and various frequencies. For extremely diluted suspensions of
mixed fullerenes or multiwalled carbon nanotubes (MWNTs) in a silicone oil, the dark-field optical microscopy was effective
for the in situ observation of the particle behavior under the electric field. The nanoparticles in a fullerene suspension
under the sinusoidal electric field with a frequency of 100 Hz (in short, 100 Hz electric field) were aggregated to form a
rigid spherical microstructure around the halfway between the electrodes. On the other hand, the nanoparticles in an MWNT
suspension under 100 Hz electric field were also aggregated but aligned to form a chain-like microstructure which spans the
electrodes. Both of the aggregated particles were stable even after the removal of the electric field, and they were redispersed
by application of 10 Hz electric field. 相似文献
8.
Polymer dispersed liquid crystal (PDLC) films are fabricated by well-known polymerization-induced phase separation method. In this paper, the dispersion of multi-walled carbon nanotubes (MWCNT) in liquid crystals has been enhanced by chemical modification and we have investigated their effects on the morphology, electro-optical properties and conductivity of the PDLC films. Results indicated that the threshold voltage and the saturation voltage of PDLC films decreased with the increase of the doping concentration of MWCNT or chemically modified MWCNT, because carbon nanotubes can enhance the electric field by reducing the resistivity of the medium and increasing the capacitance of the cells. It can be viewed obviously that the contrast ratio of the PDLC films doped with the chemically modified MWCNT is higher than that of the MWCNT. 相似文献
9.
Xiao-Ning Liang 《Journal of Dispersion Science and Technology》2016,37(9):1360-1367
Aligned carbon nanotubes (CNTs) composites can be prepared by post-growth alignment or through the use of CNT bundles. Post-growth alignment requires stringent processing conditions (high-voltage electric field/high-strength magnetic field). In this study, we focused on well-aligned multi-walled CNT bundles (AMWNTs). Achieving a balance between dispersion and required orientation was the main aim of this study. Ultrasonic dispersion will inevitably produce heat, which will adversely affect dispersion. Hence, we developed and attached a temperature-control system to a water bath ultrasonic dispersion device. Further, we studied effects of additional factors such as the type and amount of surfactant on dispersion. 相似文献
10.
Electrooptical response and microstructure of dispersions of multiwall carbon nanotubes in N-(4-ethoxybenzilidene)-4-n-butyl aniline nematic liquid crystal (LC) are studied. Irreversible response on the applied electric field (electrooptical
memory) was revealed in oriented layers of such suspensions. The essence of this effect consists in the fact that, after the
switch-on and subsequent switch-off of the field, the optical transmittance of suspension layer placed between two crossed
polarizers substantially increases compared to the initial value which is typical for homeotropic orientation of LC. The efficiency
of electrooptical memory nonmonotonically depends on the concentration of nanotubes in suspension, c
CNT, reaching its maximum at c
CNT = 0.02–0.05 wt %. It is shown that the memory of suspensions is caused by the incomplete relaxation of LC molecules from
planar to initial homeotropic state after the electric field switch-off. The model is proposed and substantiated, according
to which the planar state of LC is stabilized by the network of nanotubes formed upon the disintegration of aggregates under
the action of electrohydrodynamic flows. The disclosed memory effect is rather common; it is brought about in the suspensions
of carbon nanotubes based on other LCs in which electrohydrodynamic instabilities are developed. 相似文献
11.
Haggenmueller R Rahatekar SS Fagan JA Chun J Becker ML Naik RR Krauss T Carlson L Kadla JF Trulove PC Fox DF Delong HC Fang Z Kelley SO Gilman JW 《Langmuir : the ACS journal of surfaces and colloids》2008,24(9):5070-5078
The use of single wall carbon nanotubes (SWCNTs) in current and future applications depends on the ability to process SWCNTs in a solvent to yield high-quality dispersions characterized by individual SWCNTs and possessing a minimum of SWCNT bundles. Many approaches for the dispersion of SWCNTs have been reported. However, there is no general assessment which compares the relative quality and dispersion efficiency of the respective methods. Herein we report a quantitative comparison of the relative ability of "wrapping polymers" including oligonucleotides, peptides, lignin, chitosan, and cellulose and surfactants such as cholates, ionic liquids, and organosulfates to disperse SWCNTs in water. Optical absorption and fluorescence spectroscopy provide quantitative characterization (amount of SWCNTs that can be suspended by a given surfactant and its ability to debundle SWCNTs) of these suspensions. Sodium deoxy cholate (SDOCO), oligonucleotides (GT)(15), (GT)(10), (AC)(15), (AC)(10), C(10-30), and carboxymethylcellulose (CBMC-250K) exhibited the highest quality suspensions of the various systems studied in this work. The information presented here provides a good framework for further study of SWCNT purification and applications. 相似文献
12.
We review the recent advances in dispersing single-wall carbon nanotubes (SWNTs) using amphiphilic surfactants in aqueous solutions. Three aspects are discussed. (1) On the organization of surfactant molecules with SWNTs, new insights at the microscopic level arise from electron microscopy and detailed computer simulation studies. (2) Quantitative measurements, such as molecular interactions between functional groups and SWNTs, the coverage of surfactant on SWNTs in solution, the charge state of the SWNT/surfactant complex, and the degree of dispersion are critical for better understanding dispersion mechanisms and for the further development of dispersion strategies. (3) The thermodynamic driving forces and the role of metastability in the structure of surfactant dispersed SWNT suspensions are analyzed. An outlook on practical and fundamental issues is also presented. 相似文献
13.
It has been suggested to use suspensions of solid samples in viscous liquids for the determination of the elemental composition by the total reflection X-ray fluorescence (TRXF) method. Two liquids—ethylene glycol and glycerol—have been studied as a dispersion phase. It turned out that the sedimentation stability of suspensions in these liquids is higher than in water. During 5 min of sedimentation, the suspended analyte concentration changes by 10–15 rel. % in nonaqueous media and by up to 50 rel. % in aqueous media. It has been determined that the repeatability of measurements in nonaqueous suspensions is 3–5 rel. % against 10–15 rel. % for aqueous suspensions. It has been demonstrated that ethylene glycol and glycerol can be efficiently used for preparing samples for the TRXF method. 相似文献
14.
15.
Hammershøj P Bomans PH Lakshminarayanan R Fock J Jensen SH Jespersen TS Brock-Nannestad T Hassenkam T Nygård J Sommerdijk NA Kilså K Bjørnholm T Christensen JB 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(28):8716-8723
We describe herein the synthesis of a triptycene-based surfactant designed with the ability to solubilise single-walled carbon nanotubes (SWNTs) and C(60) in water through non-covalent interactions. Furthermore, an amphiphilic naphthalene-based surfactant with the same ability to solubilise SWNTs and C(60) has also been prepared. The compounds synthesised were designed with either two ionic or non-ionic tails to ensure a large number of supramolecular interactions with the solvent, thereby promoting strong solubilisation. The surfactants produced stable suspensions in which the SWNTs are dispersed and the surfactant/SWNT complexes formed are stable for more than one year. UV/Vis/NIR absorption spectroscopy, TEM and AFM were employed to probe the solubilisation properties of the dispersion of surfactants and SWNTs in water. 相似文献
16.
Ivar Kruusenberg Leonard Matisen Hua Jiang Maija Huuppola Kyösti Kontturi Kaido Tammeveski 《Electrochemistry communications》2010,12(7):920-923
The oxygen reduction reaction has been investigated on double-walled carbon nanotube (DWCNT) modified glassy carbon (GC) electrodes in acid and alkaline media using the rotating disk electrode (RDE) method. The surface morphology and composition of DWCNT samples was examined by transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). Aqueous suspensions of DWCNTs were prepared using Nafion and non-ionic surfactant Triton X-100 as dispersing agents. The RDE results indicated that the DWCNT modified GC electrodes are active catalysts for oxygen reduction in alkaline solution. In acid media DWCNT/GC electrodes possess poor electrocatalytic properties for O2 reduction which indicates lack of metal catalyst impurities in the DWCNT material studied. The oxygen reduction behaviour of DWCNTs was similar to that of multi-walled carbon nanotubes (MWCNTs) observed in our previous studies. 相似文献
17.
Martin Stěnička Vladimír Pavlínek Petr Sáha Natalia V. Blinova Jaroslav Stejskal Otakar Quadrat 《Colloid and polymer science》2011,289(4):409-414
Particles of polyaniline protonated with perfluorooctanesulfonic acid provided a material with hydrophobic surface. This property
enabled its perfect dispersion in silicone oil due to its good compatibility with the hydrophobic medium. In contrast, in
a suspension of hydrophilic polyaniline particles doped with sulfamic acid, strong interactions of particles prevailed, which
led to the formation of entangled chains of aggregated particles in suspension. The difference in structural properties of
suspensions exists already in the absence of electric field and significantly influences their electrorheological behavior
after application of electric field. The formation of electrorheological structure has been monitored by recording time dependences
of the shear stress and the electric current passing through the flowing suspensions. 相似文献
18.
We present a simple method of obtaining electrically conducting electrospun silk non-woven membranes consisting of nanofibers
with multi-walled carbon nanotubes (MWCNTs) adsorbed on their surface. Nanofibrous membranes with fibroin diameters of 460 ± 40 nm
were formed from aqueous Bombyx mori fibroin solution by electrospinning. The MWCNTs adhered well to the surface of the highly porous silk nanofibrous membranes
when Triton X-100 was used as the surfactant for the dispersion of the MWCNTs in aqueous media. The electrical conductivity
of the membranes was 2.4 × 10−4 S/cm due to the presence of the MWCNTs on their surface. In addition, the strong interaction between the MWCNTs and nanofibers
keeps them from separating each other, even after ultrasonication. The combination of the high conductivity of the membranes
and the simple process used to fabricate them could lead to significant advances in the development of new materials, such
as electromagnetic interference shielding or electrostatic dissipation membranes. 相似文献
19.
有机硅聚醚共聚物功能化处理制备多壁碳纳米管悬浊液 总被引:2,自引:0,他引:2
以有机硅聚醚共聚物(PSPEO)为分散剂, 水为溶剂, 超声波作用下对硝酸纯化的多壁碳纳米管、浓硫酸与浓硝酸组成的混酸剪切的多壁碳纳米管功能化处理, 分别得到1~2.5 mg/mL和3~5 mg/mL的多壁碳纳米管悬浊液. 所得悬浊液有较好的稳定性, 这得益于有机硅聚醚共聚物独特的结构与性能. 用TEM, HRTEM, UV-vis, Raman光谱等技术对多壁碳纳米管悬浊液进行表征, 结果表明5~10 nm的PSPEO覆盖在碳纳米管表面并与碳纳米管强相互作用, 实现了碳纳米管的分散. 相似文献
20.
A robust and reproducible method for the dispersion of carbon nanotubes, either single-walled or multi-walled is presented. Dispersion of nanotubes was achieved as surfactant-coated species of sodium dodecyl sulphate. The addition of small amounts of hydroxypropyl methyl cellulose (HPMC) together with the surfactant, sodium dodecyl sulphate, was found critical to achieve reproducible nanotubes dispersion and to obtain an homogeneous and stable solution. This solution is further analyzed by capillary electrophoresis using a background electrolyte solution containing a polymer, 0.025% (w/v) HPMC solution prepared in 5 mM ammonium acetate at pH 8.03. This electrophoretic method presents a high reproducibility between runs, being an interesting alternative to study nanotube size distribution or characterization after synthesis. In addition, the methodology developed allowed the study of the interaction of the different types of carbon nanotubes with a molecular probe such as pentachlorophenol. This procedure was showed effective to detect small differences on the chemical/physical surface properties of the nanotubes. The different interaction behavior found within the two SWNTs selected was critically discussed. 相似文献