Y. Feldman et al., KINETICS OF NESTED INORGANIC FULLERENE-LIKE NANOPARTICLE FORMATION, Journal of the American Chemical Society, 120(17), 1998, pp. 4176-4183
Recently, a model for the growth mechanism of inorganic fullerene-like
(IF) nanoparticles of MS2 (M = Mo, W) from the respective oxides was
presented (Feldman, Y.; Frey, G. L,.; Homyonfer, M.; Lyakhovitskaya, V
.; Margulis, L.; Cohen, H.; Hodes, G.; Hutchison, J. L.; Tenne, R. J.
Am. Chem. Sec. 1996, 118, 5362). According to this model, sulfidizatio
n of oxide particles of <150 nm leads to the formation of a sulfide en
capsulate with oxide core, which is progressively converted into a hol
low IF nanoparticle. Using transmission electron microscopy, the sulfi
dization of a group of oxide nanoparticles is demonstrated step by ste
p. This study provides direct evidence for the quasi spiral growth of
the sulfide layers into the oxide nanoparticle core. However, the mech
anism for the formation of the first closed sulfide layer which engulf
s the oxide encapsulate remained a puzzle thus far. The analysis of th
e kinetics of simultaneous reduction and sulfidization of WO3 powders
suggests the occurrence of a unique driving force for the fast growth
of the first curved sulfide layer (001) around an oxide nanoparticle.
According to the present model, a synergy between the reduction and su
lfidization processes which occurs in a very narrow window of paramete
rs leads to the formation of the first one or two closed sulfide layer
s. The present study is not limited to the sulfides. The formation of
IF-WSe2 (Tsirlina, T.; Feldman, Y.; Homyonfer, M.; Sloan, J.; Hutchiso
n, J. L.; Tenne, R. Fullerene Sci. Technol. 1998, 6, 157) is found to
be consistent with the same kind of model.