Systematic Study of the Dispersion of SWNTs in Organic Solvents

Cheng, Qiaohuan; Debnath, Sourabhi; O’Neill, Luke A.J.; Hedderman, Theresa G.; Gregan, Elizabeth; Byrne, Hugh J.

doi:10.1021/jp911202d

Cited by 54 publications

(76 citation statements)

References 18 publications

(66 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…These percolation thresholds correlate with their low dispersion limits of 2.3 × 10 −3 wt% and 5.4 × 10 −4 wt%, respectively. 35 A low dispersion limit means that MWCNTs aggregate at low wt%, which decreases the aspect ratio of the particles and results in a high percolation threshold. 36 In the MWCNT-ILs mixtures ( Figure 1c, 1d and 1e), the percolation state is reached below 1 wt%.…”

Section: Resultsmentioning

confidence: 99%

Enhanced Electrical Conductivity of Imidazolium-Based Ionic Liquids Mixed with Carbon Nanotubes: A Spectroscopic Study

Salazar

Chan

Stephens

et al. 2014

J. Electrochem. Soc.

View full text Add to dashboard Cite

We studied imidazolium-based ionic liquids mixed with multiwall carbon nanotubes using impedance spectroscopy and nuclear magnetic resonance. The results show a percolation threshold below 1 wt% of carbon nanotubes, which, due to their high dispersibility in imidazolium-based ionic liquids, is 3-to 8-fold lower than the percolation threshold for carbon nanotubes in typical organic solvents. The addition of carbon nanotubes appears to polarize their interface with imidazolium-based ionic liquids and increases the diffusion coefficient of the anions up to 35%, which is likely due to weak van der Waals interactions between the carbon nanotube walls and the cations. These effects produce a 3-to 5-fold increase in electrical conductivity of the electrolyte mixture, at carbon nanotube concentrations that are under the threshold for percolation. [7][8][9] In particular, mixing single-or multiwall CNTs in iodine-free DSCs can increase energy conversion efficiency by 100 to 300%.2,4 For example, Lee et al 4 mixed single-wall CNTs (SWCNTs) in 1-ethyl-3-methylimidazolium iodide to reach an efficiency of 1.9%, compared to 0.4% without SWCNTs. The room-temperature stability of their DSCs, with SWCNTs in the IL, is also reported to be superior to that of conventional DSCs, which use I − /I 2 in an organic solvent. While CNT-ILs show promise to enhance the efficiency of DSCs, the molecular mechanisms that enable the improved performance are not completely clear. 10 Moreover, the solubility of CNTs in ILs, and the compatibility of the mixture, is a processing challenge for several applications. 7,8,11 Because CNT-ILs are mixed ionic-electronic conductors, it is necessary to study the electronic contribution of the ions and CNTs systemically before many applications could be realized. These contributions must be examined above and below the threshold for CNT percolation to fully understand the system, but we found no studies of this type in the literature.CNTs [I] (purity >99%) from IOLITEC; DMF and DMSO from Sigma Aldrich; and MWCNTs and N-MWCNTs from US-nano (US4315 and US4882, respectively). According to product specifications, the MWCNTs had a length of 10-20 μm, outside diameter of 50-80 nm, and density of 2.1 g/cm 3 . The N-MWCNTs had an approximate length of 35 μm and outside diameter of 20-50 nm and about 3 wt% nitrogen content. The solvents, ILs, and CNTs were used as received.We stirred each mixture of MWCNT-IL on a hot plate for 30 minutes, then ultrasonicated the mixture for 30 minutes, followed by another stirring step for 15 minutes, with all steps occurring at a temperature of 65• C. The samples were allowed to cool at room temperature for at least 1 hour, followed by 5 minutes of stirring before taking measurements. To test if the MWCNTs re-agglomerate significantly after time, we made measurements within 5 minutes after the final stirring step, and after 6 hours without additional stirring, and the results only varied by about 5%. Typical sample volumes were approximately 6 mL. To increase the wt% of MWCNTs in ...

show abstract

Section: Resultsmentioning

confidence: 99%

Enhanced Electrical Conductivity of Imidazolium-Based Ionic Liquids Mixed with Carbon Nanotubes: A Spectroscopic Study

Salazar

Chan

Stephens

et al. 2014

J. Electrochem. Soc.

View full text Add to dashboard Cite

show abstract

“…In the example of TCB, the aggregation fraction decreases with decreasing concentration until it reaches a minimum of ~ 0.1 below the dispersion limit. A complete study of the variation of dispersion limit with solvent has recently been reported 13 . AFM studies have confirmed that the reduction of the aggregation fraction is due to exfoliation of the bundles with decreasing concentration until the bundles are maximally dispersed.…”

Section: Methodsmentioning

confidence: 99%

“…However, the dispersion limit of SWNTs in TCB is only ~ 0.005 mg/ml, but the aggregation fraction below D L is found to be 0.1. AFM has demonstrated that a high aggregation fraction is due to only partial debundling of SWNTs aggregates during the sonication 13 . The dispersion limit and aggregation fraction of SWNTs below D L in each solvent are listed in Table 2, together with some of the physical parameters of the solvents, including molecular weight, viscosity, vapour pressure, density and surface tension.…”

Section: Methodsmentioning

confidence: 99%

Ultrasound-Assisted SWNTs Dispersion: Effects of Sonication Parameters and Solvent Properties

Cheng¹,

Debnath²,

Gregan³

et al. 2010

J. Phys. Chem. C

Self Cite

168

127

View full text Add to dashboard Cite

Ultra-sonication is widely used for preparing Single-Walled Carbon Nanotube (SWNT) dispersions in different solvent media and it has been shown to play a critical role in dispersing and debundling SWNTs. The strong shear force which can exfoliate the SWNT bundles during sonication comes from cavitation, which entails a process of bubble formation, growth and collapse. The efficiency of the cavitation process is closely correlated to many solvent parameters, including vapour pressure, viscosity, surface tension, as well as the sonication frequency, intensity and time. In this study, SWNTs were dispersed in a range of organic solvents assisted by tip sonication. The effects of sonication intensity and time were investigated in ortho-dichlorobenzene (o-DCB) and dimethylformamide (DMF).The aggregation fraction below the dispersion limit of SWNTs in the range of organic solvents was found to be influenced by the solvent parameters, particularly solvent vapour pressure and viscosity. It is demonstrated that the parameters associated with the sonication process rather than solvent solubility 2 parameters govern the dispersion process. It is further confirmed that significant degradation of the SWNTs is affected during the dispersion process.

show abstract

“…In addition, chlorinated aromatic solvents, such as mono-chlorobenzene, ortho-dichlorobenzene (ODCB), meta-dichlorobenzene and 1,2,4-trichlorobenzene, have been demonstrated to be efficient at dispersing SWCNTs [69,70]. However, it has been found that phenyl rings within solvent molecules are not the dominant factor in obtaining stable SWCNTs dispersions [71]. This conclusion is reasonably proved by poor dispersibility of SWCNTs in toluene [67].…”

Section: Carbon Nanotubes In Imidazolium Ionic Liquidsmentioning

confidence: 99%

“…The dispersion quality of CNTs in solvents is also affected by the nanotube concentration and processing techniques as well as the physical parameters of as-produced CNTs [68,69,71]. However, "stable suspensions" of SWCNTs in the best organic solvents (DMF and NMP) still aggregate on a time-scale of days, even minutes, in the absence of any external agents [64].…”

Section: Carbon Nanotubes In Imidazolium Ionic Liquidsmentioning

confidence: 99%

Progress in Imidazolium Ionic Liquids Assisted Fabrication of Carbon Nanotube and Graphene Polymer Composites

et al. 2013

View full text Add to dashboard Cite

Carbon nanotubes (CNTs) and graphene sheets are the most promising fillers for polymer nanocomposites due to their superior mechanical, electrical, thermal optical and gas barrier properties, as well as high flame-retardant efficiency. The critical challenge, however, is how to uniformly disperse them into the polymer matrix to achieve a strong interface for good load transfer between the two. This problem is not new but more acute in CNTs and graphene, both because they are intrinsically insoluble and tend to aggregate into bundles and because their surfaces are atomically smooth. Over the past decade, imidazolium ionic liquids (Imi-ILs) have played a multifunctional role (e.g., as solvents, dispersants, stabilizers, compatibilizers, modifiers and additives) in the fabrication of polymer composites containing CNTs or graphene. In this review, we first summarize the liquid-phase exfoliation, stabilization, dispersion of CNTs and graphene in Imi-ILs, as well as the chemical and/or thermal reduction of graphene oxide to graphene with the aid of Imi-ILs. We then present a full survey of the literature on the Imi-ILs assisted fabrication of CNTs and graphene-based nanocomposites with a variety of polymers, including fluoropolymers, hydrocarbon polymers, polyacrylates, cellulose and polymeric ionic liquids. Finally, we give a future outlook in hopes of facilitating progress in this emerging area. OPEN ACCESSPolymers 2013, 5 848

show abstract

Systematic Study of the Dispersion of SWNTs in Organic Solvents

Cited by 54 publications

References 18 publications

Enhanced Electrical Conductivity of Imidazolium-Based Ionic Liquids Mixed with Carbon Nanotubes: A Spectroscopic Study

Enhanced Electrical Conductivity of Imidazolium-Based Ionic Liquids Mixed with Carbon Nanotubes: A Spectroscopic Study

Ultrasound-Assisted SWNTs Dispersion: Effects of Sonication Parameters and Solvent Properties

Progress in Imidazolium Ionic Liquids Assisted Fabrication of Carbon Nanotube and Graphene Polymer Composites

Contact Info

Product

Resources

About