Well-dispersed Single-walled Carbon Nanotubes Research Articles

High Performance Organic Thin-Film Transistor based on Amorphous A,B-Alternating Poly(arylenevinylene) Copolymers

A series of amorphous polymers of poly(arylenevinylene) copolymers, in which heterocycles (furan, thiophene, selenophene) and dialkoxy phenylenes were alternatingly linked by vinylene unit, was prepared by the Horner−Emmons reaction. Because of high regularity of the polymer microstructure by selective formation of E olefin, the resulting polymers showed good interchain π−π stacking in thin film state despite being amorphous polymers. When the A,B-alternating poly(phenylene thiophene vinylene), in particular with the bis(heptoxy) group, was used as a semiconductor material in an organic thin-film transistor, the best hole mobility up to 0.03 cm2/(V s) was observed, which is one of the highest values recorded from amorphous polymer film. The mobility was even improved to 0.06 cm2/(V s) when the polymer was blended with well-dispersed single-wall carbon nanotubes (SWCNT). Although this mobility is lower than that from the best crystalline polymers, these amorphous polymers showed advantages such as the devi...

Improved Light Output Power of GaN-Based Light Emitting Diodes by Enhancing Current Spreading Using Single-Wall Carbon Nanotubes

Single-wall carbon nanotubes (SWCNTs) have been combined with indium tin oxide (ITO) to improve the output power of GaN-based light emitting diodes (LEDs). LEDs fabricated with the SWCNT/ITO contacts give a forward voltage of 3.61 V at 350 mA, which is slightly higher than that of LEDs with ITO-only contacts. The SWCNT/ITO and ITO-only contacts produce transmittance values of 91.5 and 94.4% at 460 nm, respectively. However, LEDs with SWCNTs show a higher output power by 60% at 20 mA compared to those without SWCNTs. Photoemission microscope analyses show that the well-dispersed SWCNT bundle efficiently serves as a current spreader.

Exfoliation of Single-Walled Carbon Nanotubes Induced by the Structural Effect of Perylene Derivatives and Their Optoelectronic Properties

We designed an innovative and effective dispersion system for single-walled carbon nanotubes (SWCNTs) by introducing an exfoliation concept. Perylene derivatives were used as organic additives for dispersion of the SWCNTs. The SWCNT solutions were characterized with UV−vis−NIR absorption spectroscopy and transmission electron microscopy. Our newly designed dispersion system improved the degree of dispersion of the SWCNTs more than 10% and showed much better dispersion stability, compared to a conventional dispersion system. Furthermore, from the optoelectronic properties, we found that our designed dispersion system reduced the sheet resistance by about 50% at similar transmittance. Our analysis demonstrated that our designed dispersion system could provide a well-dispersed SWCNTs solution with long-term dispersion stability even under an extremely low dispersant concentration for dispersion of SWCNTs (weight ratio of CNTs/organic additive = 1, concentration of organic additives = 0.1 g/L, sonic treatment...

Gas sensing properties of single-wall carbon nanotubes dispersed with dimethylformamide

Abstract For NO 2 gas sensing, we deposited single-walled carbon nanotubes (SWCNTs) on a pair of interdigitated electrodes (IDEs) by using a simple casting method. In order to achieve well-dispersed SWCNTs, we dispersed the as-grown SWCNT powder into dimethylformamide (DMF). We selected DMF as one of the candidate materials to ravel the entangled SWCNT bundles because the amide group could easily attach to the surface of the nanotubes. The resultant SWCNTs were well separated. However, the SWCNTs dispersed in DMF required a heat treatment to eliminate the DMF molecules adsorbed on the surface of the SWCNTs. Therefore, we heated the SWCNTs on the IDEs to 350 °C for 1, 2, 3, and 5 h, to remove the outer DMF adsorbed layers. The assembled sensors were exposed to NO 2 of 3 and 10 ppm concentrations. We attributed the NO 2 gas sensing to the direct charge transfer from the physically adsorbed molecules to the individual p-type semiconducting SWCNTs.

Cellular structures of carbon nanotubes in a polymer matrix improve properties relative to composites with dispersed nanotubes

A new processing method has been developed to combine a polymer and single wall carbon nanotubes (SWCNTs) to form electrically conductive composites with desirable rheological and mechanical properties. The process involves coating polystyrene (PS) pellets with SWCNTs and then hot pressing to make a contiguous, cellular SWCNT structure. By this method, the electrical percolation threshold decreases and the electrical conductivity increases significantly as compared to composites with well-dispersed SWCNTs. For example, a SWCNT/PS composite with 0.5wt% nanotubes made by this coated particle process (CPP) has an electrical conductivity of ∼3×10−4S/cm, while a well-dispersed composite made by a coagulation method with the same SWCNT amount has an electrical conductivity of only ∼10−8S/cm. The rheological properties of the composite with a macroscopic cellular SWCNT structure are comparable to PS, while the well-dispersed composite exhibits a solid-like behavior, indicating that the composites made by this new CPP are more processable. In addition, the mechanical properties of the CPP-made composite decrease only slightly, as compared with PS. Relative to the common approach of seeking better dispersion, this new fabrication method provides an important alternative means to higher electrical conductivity in SWCNT/polymer composites. Our straightforward particle coating and pressing method avoids organic solvents and is suitable for large-scale, inexpensive processing using a wide variety of polymers and nanoparticles.

Supramolecular Hydrogels Hybridized with Single-Walled Carbon Nanotubes

In this study, well-dispersed single-walled carbon nanotubes (SWNTs) were successfully incorporated into a supramolecular hydrogel through combining dual roles of Pluronic copolymer in dispersing SWNTs and forming inclusion complexes with α-cyclodextrin (α-CD). Such hydrogel hybridized with SWNTs was prepared by mixing an aqueous solution of α-CD with an aqueous dispersion of SWNTs stabilized by Pluronic copolymer. The structure and properties of the supramolecular hydrogels were studied in detail by means of a variety of characterization methods. The results obtained from X-ray diffraction (XRD), Raman spectroscopy, differential scanning calorimetry (DSC), and scanning electron microscopy (SEM) showed that the introduction of well-dispersed SWNTs had no obvious influence on the structure and morphology but changed the gelation mechanism comparing with that of the native hydrogel. The resultant hybrid hydrogel retained the basic characters of supramolecular hydrogel, especially the shear-thinning and reversible temperature-responsive properties. It is noteworthy that the introduction of SWNTs accelerated the gel formation obviously, but the ultimate strength of the hybrid hydrogels, characterized by viscosities and storage modulus, declined with the increase of SWNTs.

Controlled nanostructure and high loading of single-walled carbon nanotubes reinforcedpolycarbonate composite

This paper presents an effective technique to fabricate thermoplastic nanocomposites withhigh loading of well-dispersed single-walled carbon nanotubes (SWNTs). SWNTmembranes were made from a multi-step dispersion and filtration method, and thenimpregnated with polycarbonate solution to make thermoplastic nanocomposites. Highloading of nanotubes was achieved by controlling the viscosity of polycarbonate solution.SEM and AFM characterization results revealed the controlled nanostructure in theresultant nanocomposites. Dynamic mechanical property tests indicated that thestorage modulus of the resulting nanocomposites at 20 wt% nanotubes loadingwas improved by a factor of 3.4 compared with neat polycarbonate material.These results suggest the developed approach is an effective way to fabricatethermoplastic nanocomposites with good dispersion and high SWNT loading.

Manipulation of single-wall carbon nanotubes into dispersively aligned arrays between metal electrodes

A dispersively aligned carbon nanotube array has been achieved between metal electrodes by electric-field assisted manipulation of surface modified single-wall carbon nanotubes (SWCNTs). Surface modification of SWCNTs with octadecylamine (ODA) molecules creates well-dispersed SWCNT solutions and effectively obviates the entanglement between deposited SWCNTs. The alignment effect of SWCNTs is improved by aligning them with an ac electric field of high frequency in a high-volatility solvent. The good electrical contact between the aligned SWCNTs and the metal electrodes is obtained by adopting a UV-light radiation method for removing the grafted ODA on the aligned SWCNTs.

Single-step in situ synthesis of polymer-grafted single-wall nanotube composites.

An in situ composite synthesis technique has been developed by grafting polystyrene chains onto single-wall carbon nanotubes (SWNTs) via a single-step debundling/polymerization scheme. The method, based on established anionic polymerization techniques, eliminates the need for nanotube pretreatment prior to functionalization and allows attachment of polymer molecules to pristine tubes without altering their original structure. The composites obtained contain well-dispersed SWNTs with good nanotube-matrix interaction. The scheme is quite general in nature and can be applied to different polymer systems. The simplicity and scalability of the process can lead to the realization of superior nanotube-based polymer composites for applications as advanced multifunctional structural materials.