Labeling the Defects of Single-Walled Carbon Nanotubes Using Titanium Dioxide Nanoparticles

Abstract

We describe here a new method for labeling the defects of single-walled carbon nanotubes (SWNTs) using TiO2 nanoparticles as markers. SWNTs were prepared by chemical vapor deposition, and dilute nitric acid (2.6M) oxidation was used to introduce carboxylic acid groups at the defect sites. Characterization of the SWNTs using ultrastructural and spectroscopic analyses was carried out following introduction of TiO2 nanoparticles. The results indicated that TiO2 nanoparticles were chemically absorbed at SWNT defect sites via an ester-type linkage between carboxylic acid groups at the defect sites and hydroxyl groups at the surface of the TiO2 nanoparticles. In addition, the adsorption behavior of TiO2 nanoparticles on SWNTs was determined following oxidization of the SWNTs using different processes. The results indicated that gas-phase oxidation introduces very few defect sites as evidenced by the low adsorption density of TiO2 nanoparticles. Refluxing in dilute nitric acid can be considered as a mild oxidation for SWNTs, affecting only those defects already present and causing no further damage. In contrast, sonication of SWNTs in H2SO4/H2O2 increased the incidence of carboxylic acid groups, not only at original defect sites but also at newly created defect sites along the walls of SWNTs, resulting in a higher density of TiO2 nanoparticles. In conclusion, labeling of SWNT defect sites using TiO2 nanoparticles permits direct determination of the density, distribution, and location of the defects and offers new possibilities for the creation of heterojunctions between nanotubes and nanoparticles in the future.

A Vibrational Spectroscopic Study of the Fate of Oxygen-Containing Functional Groups and Trapped CO2 in Single-Walled Carbon Nanotubes During Thermal Treatment

“…The formation of anhydride functionalities is likely when the reactant groups are near each other and our observation suggests a high local density of carboxylic acid groups on the HNO 3 -refluxed samples. A report by Li 27 suggests that the concentration of carboxylic acid groups is larger at the ends, the curves, and the connecting regions of SWNTs bundles.…”

Catalyst Residue and Oxygen Species Inhibition of the Formation of Hexahapto-Metal Complexes of Group 6 Metals on Single-Walled Carbon Nanotubes

“…The concentration of the latter functional group can be one oxygen per 123 carbon atoms in as prepared samples and as high as one oxygen per 105 carbon atoms in "purified" samples [16]. Clearly, this dramatically alters the chemical nature of the surface of the SWCNT, although this is often used as an advantage when reacting species at the surface [17,18]. Another complication in the real picture of SWCNTs is the presence of significant residue from the catalyst used to grow the tubes.…”

Enhanced Electrocatalytic Activity for the NADH Oxidation with Oxidatively Treated Carbon Nanotubes Incorporated on a Redox Polymer Modified Electrode

“…22,23 SWNTs were cut and carboxylated by the reported procedure. [24][25][26] The carboxyl group was confirmed with IR spectrometry by the band at 1720 cm −1 , which was shown only with the treated …”