Adsortion of CH4, C2H6, C3H8, C4H10, C2H5OH on SnO2 surfaces.
M.D. Ferreira1, J.D.Santos1, C A Taft2, A.C.Antunes3, S.R.M.Antunes3, E. Longo4.
1 - UEG-Universidade Estadual de Goiás, Anápolis, Go, Brazil. [email protected], [email protected]
2 - CBPF - Centro Brasileiro de Pesquisas Físicas, Rio de Janeiro, RJ, Brazil. [email protected]
3 - UEPG - Universidade Estadual de Ponta Grossa, Paraná, Brazil.
4 - UNESP -Universidade Estadual Paulista, Araraquara, SP, Brazil.
Keywords: SnO2, MNDO, gas sensor, HUZINAGA.
Chemical sensors have played a very important role in chemical sensors, in the detection of pollutant, toxic,
and industrially important gas species such as NOx, COx, NH3, SO2, and H2S[1]. MNDO studies of the ethanol
decomposition process on a SnO2 surface has been made in order to analyze this molecular mechanism [2].
In this paper, Hartree-Fock metods using HUZINAGA basis set and MNDO semiempirical studies of the
adsorption of CH4, C2H6, C3H8, C4H10 and C2H5OH on the oxygen on surfaces corresponding to the (SnO2)15 [110]
plans crystal rutile. Table 1 indicates the deltaE1 (eV) for first moment when there is interaction between the gas
in oxygen (O3, O8, O26) on the surface of the crystal (SnO2)15 at a distance of 4.0 angstroms and the values of
deltaE2(eV) for second moment when for interation resulting from the adsorption the hydrogen atom in surface
SnO2, formation radicals for the gas corresponding. The tables 2 and 3 presents the values deltaE1(eV) and
deltaE2(eV) for the interation of two molecules of gases for exemple:two CH4 or two C2H6. Two molecules of the
refering gases interact with the oxygen O3 and O6, resulting in the adsorption of the two hydrogen atoms on the
surface of the SnO2 crystal, formation of two radicals and the formation of a new hydrocarbon molecule resulting
between the two radicals formed. Figure 1 represents the interation two CH4, adsorption of the two atoms of
hydrogen on the surface of the sensor resulting in the formation of C2H6.
Table1:Variations of the MNDO energy Semi-empirical.
Gas
deltaE1(eV)
deltaE2(eV)
CH4­­­O26
0.00633
0.84958
C2H6­­­O26
0.01736
0.32443
C4H10­­­O26
0.0185
0.24485
-0.19635
2.26201
CH4­­­O3
0.00277
0.853640
C2H6­­­O3
-0.06646
0.339390
C4H10­­­O3
-0.06732
0.330670
-0.1907
2.25630
CH4­­­O8
0.000220
-6.837910
C2H6­­­O8
-0.000350
-0.998750
C4H10­­­O8
-0.001390
-6.778660
-0.177780
-6.743710
C2H5OH--O26
C2H5OH--O3
C2H5OH--O8
Fig 1: Adsorption of the two CH4 resulting
formation C2H6.
Table2:Variation of the MNDO energy.
Gas
deltaE1(eV)
deltaE2(eV)
CH4­­­O3/ CH4­­­O6
2.499840
-6.963540
C2H6­­O3/C2H6­­­O6
3.111150
-7.062670
Table3:Variation of the HF/HUZINAGA energy.
Gas
deltaE1(eV)
deltaE2(eV)
CH4­­­O3/ CH4­­­O6
5.972899
-8.277431
C2H6­­O3/C2H6­­­O6
6.626788
-8.950912
[1] Y. J. Chen, L. Nie, X. Y. Xue, Y. G. Wang, and T. H. Wang. Applied Physics Letters 88, 083105, 2006.
[2] S.R.M. Antunes, J.D.Santos, A.C. Antunes, E. Longo, J. A Varela. Journal of Molecular Structures (Theochem) 357 (1995) 153-159.