Sonochemical Oxidation of Multiwalled Carbon Nanotubes

Abstract

Functionalization of carbon nanotubes (CNTs) is important for enhancing deposition of metal nanoparticles in the fabrication of supported catalysts. A facile approach for oxidizing CNTs is presented using a sonochemical method to promote the density of surface functional groups. This was successfully employed in a previous study [J. Phys. Chem. B 2004, 108, 19255] to prepare highly dispersed, high-loading Pt nanoparticles on CNTs as fuel cell catalysts. X-ray photoelectron spectroscopy (XPS), transmission electron microscopy, cyclic voltammetry, and settling speeds were used to characterize the degree of surface functionalization and coverage. The sonochemical method effectively functionalized the CNTs. A mixture of -C-O-/-C=O and -COO- was observed along with evidence for weakly bound CO at longer treatment times. The integrated XPS C 1s core level peak area ratios of the oxidized-to-graphitic C oxidation states, as well as the atom % oxygen from the O 1s level, showed an increase in peak intensity (attributed to -CO(x)()) with increased sonication times from 1 to 8 h; the increase in C surface oxidation correlated well with the measured atom %. Most of the CNT surface oxidation occurred between 1 and 2 h. The sonochemically treated CNTs were also studied by cyclic voltammetry and settling experiments, and the results were consistent with the XPS observations.

A study on the dependence of structure of multi-walled carbon nanotubes on acid treatment

“…The exfoliation of MWNTs bundles, as functional group, increases the solubility of MWNTs in polar media [2,3], and more easily incorporated in a polymer matrix. The treatment of MWNTs is more widely done by aqueous solution of acids or oxidizing agents such as nitric acid [14,15], sulfuric acid [16], H 2 SO 4 /HNO 3 [17,18], H 2 O 2 [17], etc.…”

Oxidation and silanization of MWCNTs for MWCNT/vinyl ester composites

“…It is observed that the AR nanotubes are mainly composed of carbon and oxy- Ox-Sil gen, with a few metal impurities such as Mg, Al, Mn, and Co likely originated during the production or purification process. After oxidation with nitric acid and hydrogen peroxide (Ox), the great majority of the metal impurities are removed given the recognized action of HNO 3 as a purifying agent [15,16,18]. For this treatment, additional oxygen containing groups are introduced on the CNT surface, as indicated by the increase in oxygen content shown in Table 2.…”

“…promotes the formation of functional groups at the nanotube surface, which may react with the functional groups of the organic polymer forming permanent bonds [4,5,[15][16][17]. Among the most frequent functionalization techniques reported to improve mechanical properties of CNT-thermosetting polymer composites are oxidations [5,[15][16][17][18] and amine based treatments [5,13,19,20], while CNT silanization has been less reported in the open literature [21][22][23][24][25]. Although silane treatments are quite common for micron-size fiber-reinforced polymers, such treatments have not been thoroughly examined for CNTs.…”

Characterizing Functionalized Carbon Nanotubes for Improved Fabrication in Aqueous Solution Environments

“…Sonication was performed for 1, 2, 4 and 8 hrs. The sonochemically treated MWNTs were then separated from the acids in a centrifuge (Thermal IEC Centra CL2), and thoroughly washed using doubly distilled, deionized water prior to analysis (Xing et al, 2005). The chemical oxidation states and surface compositions of the resulting sonochemically treated MWNTs and Pt electrocatalysts were analyzed by XPS using an ion-pumped PerkinElmer PHI ESCA 560 system using a PHI 25-270AR double pass cylindrical mirror analyzer.…”

“…Sensor applications involve the tethering of chemical moieties with specific recognition sites for the detecting ultra-trace analytes (Dai, 2002). Surface functionalization is also necessary for depositing high-loading, catalytically active metal nanoparticles on them (Xing et al, 2005). Great attention has been paid to attaching functional groups onto carbon nanotube surfaces (Holzinger et al, 2001;Kim et al, 2004;Chen et al, 2005;Park et al, 2006) and probing the electronic structure resulting from post-nanotube-synthesis preparations.…”