Metal nanoparticle formation on layer silicate lamellae

Nanoparticles (Ag, Pd) were prepared by heterogeneous nucleation on the interlayer space of layered montmorillonite and kaolinite minerals in aquatic dispersion. Interlamellar incorporation of nanoparticles was monitored by X-ray diffraction and verified by transmission electron microscopy (TEM). After the reduction of adsorbed metal ions, a new Bragg reflection appeared, proving the formation of nanoparticles in the interlamellar space of clay mineral. Lamellar structure of layered silicates is partly destroyed by the particle formation. TEM images showed that larger nanoparticles were formed by UV irradiation and hydrazine hydrate than in the case of reduction by NaBH₄. Aqueous solutions of polyvinyl pyrrolidone and clay minerals were used for the stabilization of Pd° nanoparticles. The size of particles generated on the surface of clay minerals by heterogeneous nucleation increased with increasing metal concentration. When polymer is added to this system, particle size can be decreased by increasing polymer concentration. In this case, the particles are stabilized by the concerted action of the support and the macromolecule. The polymers promoted intercalation of nanoparticles into the clay mineral. In the absence of nanoparticles, the intercalation of polymers was significantly less extensive.