RESUMO
It is shown that by using cryo-transmission electron microscopy (cryo-TEM) it is possible to image the aggregation behaviour of nanoparticles while they are still in solution. This technique has allowed the study of the arrangement of colloidal palladium particles in solution by preparing the specimen by the plunge-freezing technique. This method of rapidly cooling the specimen avoids rearrangement of the particles during specimen preparation. The palladium particles were identified by energy-filtered cryo-TEM. The aggregation of particles in solution was studied as a function of pH and ionic strength. The results can be used as recommendations for colloidal solutions intended for deposition of single particles.
RESUMO
Soluble ruthenium nanoparticles of uniform size (see picture) with a porous spongelike structure were obtained by the reaction of [Ru(C(8)H(10))(C(8)H(12))] with H(2) in methanol or THF/methanol. The particle size can be controlled in the range 15-100 nm by varying the MeOH/THF ratio. The particles catalyze benzene hydrogenation without modification of their size or structure. Their formation is proposed to occur in the droplets of a nanosized emulsion, which act as nanoreactors.
