Publication: Functionalization of multi wall carbon nanotubes via acid oxidation
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Date
2009-05-01
Authors
Khalid, Noor Hifzana
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Abstract
Since their discovery in 1991 by Iijima, carbon nanotubes have been of great interest, both from a fundamental point of view and for future applications. The most eye- catching features of these structures are their electronic, mechanical, optical and chemical characteristics, which open a way to future applications. Most applications require nanotube purification after growth, consisting in the separation of the nanotubes from other phases. Multi Wall Carbon Nanotubes (MWCNTs) were oxidized with concentrated nitric acid (HNO3) at 140 %C but different oxidizing time and oxidized at 140 %C for 3h in different acid ratio, nitric acid (HNO3) and a mixture of concentrated nitric acid and sulfuric acid (1:3 and 3:1, v/v). Oxidized MWCNTs were then evaporated at 75 %C and collected after dried in vacuum oven at 90 %C for 5 hours. The resulting oxidized MWCNTs also have been modified by attachment of carboxylic acid groups on the surface MWCNTs thus formed stable dispersion state in the polar solvents without the help of surfactants that provided possibility for further functionalization and application. Morphological (SEM, TEM and EDX) and structural (XRD and FTIR) analyses were also performed on MWCNTs, both before and after the functionalization processes. Titration of the oxidized MWCNTs with sodium hydroxide, NaOH solutions was used to determine the amount of acidic sites. Based on visual observation, the dispersion stability of MWCNTs was investigated. Concluded that 3 h nitric acid oxidized MWCNTs have been selected as the efficient sample since it shown better dispersibility in polar solvent with the amount of acidic sites also high which is 2.814 x 10-4 mol.