Optimizing the Dispersion Conditions of SWCNTs in Aqueous Solution of Surfactants and Organic Solvents

Md Mahfuzur Rahman,Amal Al Ghaferi,Hammad Younes,Navaladian Subramanian

doi:10.1155/2014/102621

Abstract

The optimum concentration of surfactants in aqueous medium and the optimum sonication time for organic medium to achieve the best dispersion of SWCNTs are investigated in this study. Scanning electron microscope (SEM), atomic force microscope (AFM), and UV-vis-NIR study show that the optimum surfactant concentrations to achieve best dispersion for 0.25 mg/mL of SWCNTs are 9-10 mg/mL for (sodium dodecylbenzenesulfonate (SDBS)) and 8-9 mg/mL for (sodium deoxycholate (DOC)). The diameter of the SWCNT lies between 0.7 and 2.5 nm in the case of aqueous solvent, which is in good agreement with the chirality. Moreover, SEM analysis reveals the presence of well-dispersed nanotubes along with some amount of surfactant particles; that is, some nanotubes might be covered with surfactants. Best dispersion of SWCNTs in organic solvents (1,2-Dichloroethane (DCE) and N,N-Dimethylformamide (DMF)) is achieved by four hours of tip sonication. It realized that organic solvents provide pure SWCNTs after drying, which may possibly have SWCNTs with intrinsic properties.

Highlights

Single-walled carbon nanotubes (SWCNTs) are promising materials for many applications such as photovoltaic, medical diagnostics, drug delivery, nanofluids, grease, optical sensing, nanoelectronics, and polymer nanocomposites [1,2,3,4,5,6]
Organic solar cells made of single polymer and two electrodes are inefficient because of the low carrier mobility which can be solved by introducing carbon nanotubes (CNTs) [8, 9]
Naumov et al have recently showed that the background could be induced by ultrasonication of SWCNTs and surfactants and the differences in the background absorption are related to the nanotube lengths, plasmonic absorption of SWCNTs and carbonaceous impurities, contributions from chemical derivations, spectral broadening from nanotube bundling, and spectral congestion from closely spaced peaks in samples with many (n, m) species [31]

Summary

Introduction

Single-walled carbon nanotubes (SWCNTs) are promising materials for many applications such as photovoltaic, medical diagnostics, drug delivery, nanofluids, grease, optical sensing, nanoelectronics, and polymer nanocomposites [1,2,3,4,5,6]. Ultrasonication of the CNT solution with surfactant provides enough energy to separate the nanotubes by overcoming Van der Waals force [13]. At very low surfactant concentration, the dispersion quality is poor because nanotubes form bundles. Surfactant-aided aqueous dispersion of SWCNTs can individualize nanotubes, but the removal of surfactant is difficult, because of its high boiling point. Surfactants wrap SWCNTs and this may degrade hole transport properties of nanotubes in the organic solar cell. Organic solvents can dissolve SWCNTs at very low concentration without altering the properties of pristine nanotubes. A comparative analysis has been made between organic solvent and surfactant aided aqueous dispersion of SWCNTs for photovoltaic application

Experimental Details

Results and Discussion

Conclusions