Monochromatic UV light in the spectral interval between 4.0 and 5.5 eV is used in order to selectively excite 3- and 4-coordinated oxygen anion sites on the surface of MgO nanoparticles exposed to O2 gas. As a result, two different paramagnetic O surface species and also ozonide anions O3 are observed by electron paramagnetic resonance (EPR) spectroscopy. The relative abundance of each of the O species exhibits a specific dependence on the energy of the exciting photons. EPR data together with the results of theoretical modeling suggest that both O species are located at 3-coordinated sites having different local environments. At sufficiently high O2 pressures molecular oxygen does not only act as an electron trap, favoring the O formation, but it also contributes to UV induced O3 formation with a maximum efficiency at 4.2 eV.

1.
C. G.
Harkins
,
W. W.
Shang
, and
T. W.
Leland
,
J. Phys. Chem.
73
,
100
(
1969
).
2.
A. M.
Volodin
,
Catal. Today
58
,
103
(
2000
).
3.
M.
Anpo
,
Y.
,
Yamada
,
Y.
Kubokawa
,
S.
Coluccia
,
A.
Zecchina
, and
M.
Che
,
J. Chem. Soc., Faraday Trans. 1
84
,
751
(
1988
).
4.
R. L.
Nelson
and
J. W.
Hale
,
Trans. Faraday Soc.
52
,
77
(
1971
).
5.
F.
Garrone
,
A.
Zechina
, and
F. S.
Stone
,
Philos. Mag. B
42
,
683
(
1980
).
6.
A.
Zecchina
and
F. S.
Stone
,
J. Chem. Soc., Faraday Trans. 1
71
,
1476
(
1975
).
7.
A. L.
Shluger
,
P. V.
Sushko
, and
L. N.
Kantorovich
,
Phys. Rev. B
59
,
2417
(
1999
).
8.
P. V.
Sushko
and
A. L.
Shluger
,
Surf. Sci.
421
,
157
(
1999
).
9.
M.
Anpo
and
M.
Che
,
Adv. Catal.
44
,
119
(
1999
), and references therein.
10.
S. Coluccia, in Adsorption and Catalysis on Oxide Surfaces, edited by M. Che and G. C. Bond (Elsevier, Amsterdam, 1984), p. 59.
11.
S. Coluccia and A. J. Tench, in Proceedings of the 7th International Congress on Catalysis, 1980, edited by T. Seyama, K. Tanabe, and Kodansha (Tokyo, 1981), p. 1154.
12.
M.
Iwamoto
and
J. H.
Lunsford
,
Chem. Phys. Lett.
66
,
48
(
1979
).
13.
T.
Ito
,
A.
Kawanami
,
K.
Toi
,
T.
Shirakawa
, and
T.
Tokuda
,
J. Phys. Chem.
92
,
3910
(
1988
).
14.
M.
Che
and
A. J.
Tench
,
Adv. Catal.
31
,
77
(
1982
).
15.
M.
Sterrer
,
O.
Diwald
, and
E.
Knözinger
,
J. Phys. Chem. B
104
,
3601
(
2000
).
16.
M.
Che
and
A. J.
Tench
,
Adv. Catal.
32
,
1
(
1983
).
17.
M.
Anpo
,
M.
Che
,
B.
Fubini
,
E.
Garrone
,
E.
Giamello
, and
M. C.
Paganini
,
Top. Catal.
8
,
189
(
1999
).
18.
A. M.
Ferrari
,
R.
Soave
,
A.
D’Ercole
,
C.
Pisani
,
E.
Giamello
, and
G.
Pacchioni
,
Surf. Sci.
479
,
83
(
2001
).
19.
P. V. Sushko, J. L. Gavartin, and A. L. Shluger, J. Phys. Chem. B (to be published).
20.
P. V.
Sushko
,
A. L.
Shluger
, and
C. R. A.
Catlow
,
Surf. Sci.
450
,
153
(
2000
).
21.
E.
Knözinger
,
K.-H.
Jacob
,
S.
Singh
, and
P.
Hofmann
,
Surf. Sci.
290
,
388
(
1993
).
22.
E.
Knözinger
,
M.
Sterrer
, and
O.
Diwald
,
J. Mol. Catal. A: Chem.
162
,
83
(
2000
).
23.
A. D.
Becke
,
J. Chem. Phys.
98
,
5648
(
1993
).
24.
M. J. Frisch, G. W. Trucks, H. B. Schlegel, et al., GAUSSIAN 98, Edition A1, Gaussian, Inc., Pittsburgh, PA, 1998.
25.
J. R.
Brailsford
and
J. R.
Morton
,
J. Chem. Phys.
51
,
4794
(
1969
).
26.
G. Martra, S. Coluccia, E. Knözinger (unpublished).
27.
M.
Che
,
E.
Giamello
, and
A. J.
Tench
,
Colloids Surf.
13
,
231
(
1985
).
28.
J. H. Lunsford, in Handbook of Heterogenous Catalysis, edited by G. Ertl, H. Knözinger, and J. Weitkampp (VCH-Weinheim, New York, 1997), Vol. 4, p. 1843.
This content is only available via PDF.
You do not currently have access to this content.