Pd nanoparticles prepared by controlled colloidal synthesis in solid/liquid interfacial layer on silica. I. Particle size regulation by reduction time

Controlled colloidal synthesis (CCS) was developed to prepare monodisperse palladium particles in the nano-scale range on suspended SiO2 particles in an ethanol–toluene mixture. On colloidal SiO2 an about 1 nm thick ethanol-rich adsorption layer was produced in adsorption equilibrium with the liquid mixture. Ethanol served as a reducing agent for the Pd(II) ions diffusing from a toluene-rich liquid solution into the interfacial layer. The low reduction rate ensures the dominancy of particle growth over the nucleation of palladium during the reduction process after the initial nucleation. The relation between the reduction time and the particle size produced was studied. XRF, XPS, TEM, CO chemisorption, and benzene hydrogenation as catalytic test were employed to characterize the samples prepared using different reduction time.