Effect of sulphuric–nitric acid mixture composition on surface chemistry and structural evolution of liquid‐phase oxidised carbon nanotubes

Abstract

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.

Effectiveness of carbon nanotube–cobalt ferrite nanocomposites for the adsorption of rhodamine B from aqueous solutions

“…34,46,53 and is conrmed in this work as demonstrated in entries 1 and 2 of Table 4. CoFe 2 O 4 nanoparticles and CNTs have been reported to have moderately large surface areas.…”

“…46 The suspension was stirred for 2 h; the tubes were ltered and washed with deionised water until a neutral pH was obtained.…”

Preparation, processing and analysis of physical properties of calcium ferrite-CNTs/PET nano-composite

“…In this paper we report the morphological organization and physical properties (thermal, mechanical, electrical) of nano-hybrid Calcium Ferrite-CNTs (CFCNTs) composites prepared by microinjection molding using a twin screw extruder. CF-CNTs (CNT content 76 wt%) were prepared by direct growth of CNTs over CF based catalysts [22][23].…”

Carbon supported gold and silver: Application in the gas phase hydrogenation of m -dinitrobenzene

“…Subsequent acid treatment (in HNO 3 + H 2 SO 4 ) was used to introduce oxygen containing groups as nucleation sites for the deposition of Au and Ag [22]. A displacement of the acid-base titration curves for AC pre-and post-acid treatment (not shown) confirmed an increase in surface acidity due to the generation of carbonyl (quinone and lactone) and carboxyl (acid and anhydride) functionalities [32]. Acid-base titration delivered a pH at the equivalency point (pK a ) of 6.4, which suggests the absence of strong carboxylic acid sites (pK a < 5) and the formation of surface quinone, lactone and anhydride groups [33].…”