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Open Access Nano Express

A study on the effect of different chemical routes on functionalization of MWCNTs by various groups (-COOH, -SO3H, -PO3H2)

Pawan Kumar1, Jin-Soo Park2*, Prabhsharan Randhawa1, Sandeep Sharma1, Mun-Sik Shin2 and Satpal Singh Sekhon1*

Author Affiliations

1 Department of Physics, Guru Nanak Dev University, Amritsar, 143005, India

2 Department of Environmental Engineering, College of Engineering, Sangmyung University, Cheonan, Chungnam Province, 330-720, Republic of Korea

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Nanoscale Research Letters 2011, 6:583  doi:10.1186/1556-276X-6-583

Published: 7 November 2011

Abstract

Pristine multiwall carbon nanotubes [MWCNTs] have been functionalized with various groups (-COOH, -SO3H, -PO3H2) using different single- and double-step chemical routes. Various chemical treatments were given to MWCNTs using hydrochloric, nitric, phosphoric, and sulphuric acids, followed by a microwave treatment. The effect of the various chemical treatments and the dispersion using a surfactant via ultrasonication on the functionalization of MWCNTs has been studied. The results obtained have been compared with pristine MWCNTs. Scanning electron microscopy, energy dispersive X-ray [EDX] spectroscopy, and transmission electron microscopy confirm the dispersion and functionalization of MWCNTs. Their extent of functionalization with -SO3H and -PO3H2 groups from the EDX spectra has been observed to be higher for the samples functionalized with a double-step chemical route and a single-step chemical route, respectively. The ID/IG ratio calculated from Raman data shows a maximum defect concentration for the sample functionalized with the single-step chemical treatment using nitric acid. The dispersion of MWCNTs with the surfactant, Triton X-100, via ultrasonication helps in their unbundling, but the extent of functionalization mainly depends on the chemical route followed for their treatment. The functionalized carbon nanotubes can be used in proton conducting membranes for fuel cells.

Keywords:
functionalization; carbon nanotubes; dispersion; surfactant