Role of Anions in the AuCl₃-Doping of Carbon Nanotubes

Abstract

The doping/dedoping mechanism of carbon nanotubes (CNTs) with AuCl(3) has been investigated with regard to the roles of cations and anions. Contrary to the general belief that CNTs are p-doped through the reduction of cationic Au(3+) to Au(0), we observed that chlorine anions play a more important role than Au cations in doping. To estimate the effects of Cl and Au on CNTs, the CNT film was dedoped as a function of the annealing temperature (100-700 °C) under an Ar ambient and was confirmed by the sheet resistance change and the presence of a G-band in the Raman spectra. The X-ray photoelectron spectroscopy (XPS) analysis revealed that the doping level of the CNT film was strongly related to the amount of adsorbed chlorine atoms. Annealing at temperatures up to 200 °C did not change the amount of adsorbed Cl atoms on the CNTs, and the CNT film was stable under ambient conditions. Alternatively, Cl atoms started to dissociate from CNTs at 300 °C, and the stability of the film was degraded. Furthermore, the change in the amount of Cl atoms in CNTs was inversely proportional to the change in the sheet resistance. Our observations of the Cl adsorption, either directly or mediated by an Au precursor on the CNT surface, are congruent with the previous theoretical prediction.

The synthesis of carbon nanomaterials using chlorinated hydrocarbons over a Fe-Co/CaCO3 catalyst

“…Modification of CNTs has thus led to the creation of new functional and construction materials. 11 Doping of the carbonaceous materials with non-carbon atoms, such as nitrogen, [12][13][14][15][16][17][18][19] boron, [20][21][22][23][24] sulphur, [25][26][27][28][29] oxygen [30][31][32][33][34][35][36] and halogens 11,[37][38][39][40][41][42][43][44][45][46][47][48][49][50][51][52][53][54][55] has been explored over the past two decades. Modification of the carbon surface and electronic properties has also been explored but the effect of chlorine (Cl) on the morphology of carbon nanomaterials is not well established.…”

Insights into chemical doping to engineer the carbon nanotube/silicon photovoltaic heterojunction interface

“…The FOM degradation of the AgNW hybridized GOCNTs is caused by the oxidation of the metal nanowire, 70 while the severe desorption of physisorbed NO 2 and HNO 3 molecules 57 and the aggregation of Au nanoparticles 71 as well as the desorption of Cl À which may react with air are the potential reasons for the FOM degradation of GOCNT lms treated with HNO 3 and AuCl 3 . 44 The doping stability of SOCl 2 is better than those of the aforementioned three but worse than that of CuCl 2 . The better stability of CuCl 2 treated GOCNT lms is due to the Cu 2+ hydroxide in the redox dopant, which can persistently withdraw electrons from CNTs over the long term.…”

Application of Hole-Transporting Materials as the Interlayer in Graphene Oxide/Single-Wall Carbon Nanotube Silicon Heterojunction Solar Cells

“…Most researchers assign the p-type doping to the reduction of Au 3þ to Au, but others think that the formation of SWCNT-Cl plays an important role with the electrons of SWCNTs withdrawn to Cl. [51] Initial Testing of Photovoltaic Devices The performance of three sets of devices, GOCNT/Si, HTL/Si, and GOCNT/HTL/Si, is shown in Fig. 3, Table 1 ) from 300 to 1100 nm (Fig.…”