KINETICS OF NESTED INORGANIC FULLERENE-LIKE NANOPARTICLE FORMATION

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.