A. Berko et F. Solymosi, Effects of different gases on the morphology of Ir nanoparticles supportedon the TiO2(110)-(1 x 2) surface, J PHYS CH B, 104(44), 2000, pp. 10215-10221
The preparation of Zr nanoparticles supported on the TiO2(110)-(1x2) surfac
e and the effects of annealing in different gases were studied by scanning
tunneling microscopy. The smallest Ir particles, measuring 1 nm and consist
ing of 8-10 atoms, were produced by the deposition of approximately 0.005 m
onolayer (ML) of Ir at 300 K. On an increase of the Ir coverage, the diamet
er of the particles gradually rose to 5 nm at 2 ML coverage. Annealing of t
he Ir-covered surfaces caused only slight changes below 700 K but led to mi
gration and coalescence of the particles above 700 K. The hexagonal appeara
nce of the larger particles suggested the formation of Ir crystallites with
their (111) faces parallel to the plane of the support. The orientation of
the slightly elongated particles was adjusted to the [001] direction of th
e TiO2(110)-(1 x 2) surface. In the presence of CO (10(-3) mbar), the small
est Ir particles (consisting of 8-10 atoms) disrupted into atomically dispe
rsed Ir within a few minutes at 300 K. On an increase of the particle size,
the disintegration proceeded more slowly, even at higher CO pressure. For
particles larger than 3-4 nm, only minor corrosion of the nanoclusters was
observed, even in the presence of 10 mbar CO. At higher temperature (600 K)
, the reversed process, the GO-induced agglomeration of small Ir particles,
occurred. The adsorption of NO and O-2 also caused disruption of the Ir na
noparticles at 300-500 K. Such an effect was not experienced in the presenc
e of N-2, which interacts only weakly with Ir-x crystallites.