Individually Dispersing Single-Walled Carbon Nanotubes with Novel Neutral pH Water-Soluble Chitosan Derivatives

Abstract

Chitosan and its various neutral pH water-soluble derivatives were investigated for dispersing single-walled carbon nanotubes (SWNTs). Chitosan (CS) can produce good dispersion of SWNTs, but only in acidic pH condition. Our two novel derivatives, O-carboxymethylchitosan (OC) and OC modified by poly(ethylene glycol) at the −COOH position (OPEG), were able to produce highly effective debundling and dispersion of SWNTs in neutral pH aqueous solution. Atomic force microscopy (AFM), transmission electron microscopy (TEM), photoluminescence, UV−vis−NIR spetroscopy, and Raman spectroscopy confirmed that SWNTs are present as individual nanotubes in the dispersions. The solubilities of individually dispersed SWNTs in neutral water are 0.021 and 0.032 g/L for OC and OPEG, respectively, which are comparable to 0.038 g/L for SWNTs using CS in acetic acid. Further, OC and OPEG aqueous solutions (1 wt %) do not significantly lower the surface tensions (65−67 mN/m). From the Fourier transform infrared spectroscopic results, we conclude that the free electron pair in the pendant amine groups of OC and OPEG plays a vital role in finely dispersing the SWNTs; the −NH2 contributes to the adsorption of these two chitosan derivatives on the nanotubes. Quaternary ammonium chitosan (QC), with alkyl substitution at the protonated amine, was found to be unable to disperse SWNTs; possibly cation−π interaction with nanotubes is diminished due to steric hindrance.

Preparation of semiconductor-enriched single-walled carbon nanotube dispersion using a neutral pH water soluble chitosan derivative

“…The absorption bands in the wavelength range from 400 to 600 nm represent the lowest energy M 11 van Hove transition of metallic SWNTs, from 550 to 800 nm represent the second van Hove transition of semiconducting SWNTs (S 22 ) and from 800 to 1400 nm correspond to the first van Hove transition of semiconducting SWNTs (S 11 ). The S 11 peaks marked increase of intensity as they are easily affected by the SWNT chemical environment [35]. Fig.…”

Interaction of water soluble chitosan with multiwalled carbon nanotubes

“…10 Chitosan and its derivatives have been studied for its dispersing of CNTs in solvents. 11,12 On the other hand, the conformation of chitosans on CNTs is very important for the application of the CNT composite. 13,14 Though chitosan/CNTs systems have been extensively studied, little research is reported for the interaction of chitosans with CNTs.…”

Fundamental Limits on the Mobility of Nanotube‐Based Semiconducting Inks

“…Figure 1e shows a representative AFM image of nanotube network deposited on wafers. www.advmat.de www.MaterialsViews.com COMMUNICATION 96reported to be around 0.12 mg mL − 1 , [ 12 ] although when these solutions are further processed for purifi cation and separation, only a fraction of nanotubes compared to the starting solution are left in the resultant solution. In our experiments, we varied the nanotube concentration until just prior to precipitation, and also via dilution until no nanotubes were visibly deposited.…”