AVS 50th International Symposium
    Nanotubes Wednesday Sessions
       Session NT-WeP

Paper NT-WeP19
Experimental and Theoretical Studies on the Ozone Reactivity with Carbon Nanotubes

Wednesday, November 5, 2003, 11:00 am, Room Hall A-C

Session: Poster Session
Presenter: I. Armentano, University of Perugia, Italy
Authors: S. Picozzi, INFM and University of L'Aquila, Italy
L. Lozzi, INFM and University of L'Aquila, Italy
F. Di Gregorio, INFM and University of L'Aquila, Italy
S. Santucci, INFM and University of L'Aquila, Italy
C. Cantalini, INFM and University of L'Aquila, Italy
C. Baratto, INFM and University of Brescia, Italy
G. Sberveglieri, INFM and University of Brescia, Italy
L. Valentini, University of Perugia, Italy
I. Armentano, University of Perugia, Italy
B. Delley, Paul Scherrer Institut, Switzerland
Correspondent: Click to Email
In a previous paper@footnote 1@ it has been reported how carbon nanotubes (CNTs) thin films deposited by plasma-enhanced chemical vapor deposition have a strong reactivity with NO2. In this work we investigate a CNT film as resistive gas sensors for O3. The sensor composed by the aligned CNT film with a thickness of 200 nm exhibits sensitivity to O3 gas at concentrations as low as 25 ppb, fast response time with a baseline drift that has been observed if the operating temperature of the sensor is increased over 70°C Upon the reaction with O3, the electrical resistance of the CNTs is found to decrease. In order to obtain a theoretical validation of the experimental results, the equilibrium position, charge transfer and density of states are calculated from first principles for the CNT+O3 system within the density functional theory, using the all-electron Dmol3 (density functional theory for molecules and three-dimensional periodic solids) code.@footnote 2@ Our calculations show that the ozone molecule adsorbs on the tube with a binding energy of the order of 300 meV and gains about 0.1 electrons from the CNT. The calculated density of states shows that O3 adsorption gives rise to an acceptor peak at the Fermi level, which lies in correspondence to the tube valence band maximum, rendering the CNT+O3 system metallic. This is consistent with the experimentally observed increase in conductivity. The baseline shift of the sensor experimentally observed for the higher working temperatures may be ascribed to a consumption of the carbon nanotube under the ozone exposition at the defective sites.@footnote 3@ @FootnoteText@ @footnote 1@ L. Valentini, I. Armentano, J. M. Kenny, C. Cantalini, L. Lozzi, and S. Santucci, Applied Physics Letters Volume 82, Issue 6, pp. 961-963 (2003). @footnote 2@ B. Delley, J. Chem. Phys. 113, 7756 (2000); ibid. 92(1), 508 (1990) @footnote 3@ D.B. Mawhinney, V. Naumenko, A. Kuznetsova and J.T. Yates Jr., J. Am. Chem. Soc., 122, 2383 (2000).