Barberio M, Barone P, Bonanno A, Oliva A
Lab. IIS--Physics Department, University of Calabria and INFN gruppo collegato di Cosenza, Via P Bucci, Cubo 31c, 87036 Arcavacata di Rende, Italy.
J Nanosci Nanotechnol. 2012 Jun;12(6):5039-42. doi: 10.1166/jnn.2012.4933.
In this work we present a purification technique for oxygen removal from carbon nanotubes (CNTs) at relatively low temperature monitored by X-ray Photoelectron Spectroscopy and electrical characterization (change in resistance). We dope the sample with alkali metal (Na, K and Cs), which successively bind with the residual impurities of oxygen. The removal of the so formed oxides occur by heating the sample at relatively low temperatures (500-600 degrees C) without collateral damage to CNTs mat. In particular we investigate the in situ intercalation of alkali in SWNT followed by oxygen adsorption monitored by DC resistance measurements and X-ray photo-spectroscopy (XPS), demonstrating that the alkali intercalation in the samples trigger the oxygen adsorption. A subsequent sample heating at 500 degrees C removes both oxygen and alkali. Furthermore, the amount of the oxygen removal depends upon the deposited alkali species: in effect only with Na and K we obtain a complete oxygen removal, while other alkalis probably do not intercalate properly inside the nanotube walls. We hypothesize that the atomic radius of alkali can affect the intercalation properties of them inside the CNT structure.
