Individual Single-Walled Nanotubes and Hydrogels Made by Oxidative Exfoliation of Carbon Nanotube Ropes

Abstract

Single-walled carbon nanotubes were oxidized by a technique previously developed for the oxidation of graphite to graphite oxide (GO). This process involves treatment with concentrated H(2)SO(4) containing (NH(4))(2)S(2)O(8) and P(2)O(5), followed by H(2)SO(4) and KMnO(4). Oxidation results in complete exfoliation of nanotube ropes to yield individual oxidized tubes that are 40-500 nm long. The C:O:H atomic ratio of vacuum-dried oxidized nanotubes is approximately 2.7:1.0:1.2. XPS and IR spectra show evidence for surface O-H, C=O, and COOH groups. The oxidized nanotubes slowly form viscous hydrogels at unusually low concentration (>or=0.3 wt %), and this behavior is attributed to the formation of a hydrogen-bonded nanotube network. The oxidized tubes bind readily to amine-coated surfaces, on which they adsorb as smooth and dense monolayer films. Thin films of the oxidized nanotubes show ohmic current-voltage behavior, with resistivities in the range of 0.2-0.5 Omega-cm.

Minimizing purification-induced defects in single-walled carbon nanotubes gives films with improved conductivity

“…The C 1s spectrum of SWNTs purifi ed by refl uxing in HNO 3 (3 mol/L) for 18 h was fitted to several symmetrical components according to the peak assignment used by Hiura et al [31]. The three peaks in the high energy shoulder of the main peak, with binding energies located at 286, 287.4, and 289.1 eV, can be assigned to C O (e.g., alcohol and ether), C=O (e.g., ketone and aldehyde), and O C=O (e.g., carboxylic acid and ester) species, respectively [32,33]. These groups are introduced during the oxidizing purification of as-synthesized carbon nanotubes.…”

Fluorescent Magnetic Silica Nanotubes with High Photostability Prepared by the Conventional Reverse Micro-Emulsion Method

“…10 A silica layer was deposited through a surface sol-gel method. 11,12 Briefly, one cycle of sol-gel processing involved immersing the templates in SiCl 4 (99.8%) solution for 5 min, washing them with hexane and methanol, drying them, immersing them in DI water for 5 min and washing them with methanol. Five such cycles produced a silica layer of optimal thickness (ca.…”

Preparation, Characterisation and Photocatalytic Applications of TiO2-MWCNTs Composite

“…5(b) functionalised MWCNTs exhibits characteristic strong and broad band between 3173-3600 cm -1 which can be attributed to O-H stretching vibrations in C-OH groups. The broad band between 1766-2017 cm -1 is attributed to C=O stretching vibrations in carboxyl, aldehyde and acid anhydride groups 37 .…”