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Effect of sulphuric–nitric acid mixture composition on surface chemistry and structural evolution of liquid‐phase oxidised carbon nanotubes
Author(s) -
Santangelo S.,
Messina G.,
Faggio G.,
Abdul Rahim S. H.,
Milone C.
Publication year - 2012
Publication title -
journal of raman spectroscopy
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.748
H-Index - 110
eISSN - 1097-4555
pISSN - 0377-0486
DOI - 10.1002/jrs.4097
Subject(s) - chemistry , nitric acid , raman spectroscopy , carboxylic acid , carbon nanotube , carbon fibers , liquid phase , organic chemistry , phenols , homogeneity (statistics) , inorganic chemistry , chemical engineering , materials science , physics , composite number , optics , composite material , thermodynamics , engineering , statistics , mathematics
Liquid phase functionalisation of carbon nanotubes is carried out via a H 2 SO 4 + HNO 3 mixture, and the effect of the sulphuric to nitric acid volume ratio (1:3–3:1) is systematically investigated by means of complementary techniques, observing the expected progressive downgrade of the crystalline quality, along with the increase of oxygenated functionality concentration. In addition, in contrast with common expectations, the results obtained demonstrate that the concentration of carboxylic groups (acids and anhydrides) never exceeds that of all other functionalities (lactones, phenols, quinones/carbonyls and sulphonic groups) introduced by chemical oxidation. Only by using equal volumes of sulphuric and nitric acids the concentrations of carboxylic and non‐carboxylic groups become comparable. Raman analysis reveals that a change in the sample homogeneity accompanies the variations of the relative proportions of the various oxygenated groups, by the typology of which the vibration modes of carbon pairs and carbon rings appear to be affected to different extents. Copyright © 2012 John Wiley & Sons, Ltd.