Shape-Controlled Synthesis of Silver and Palladium Nanoparticles Using β-Cyclodextrin

Shape-controlled silver and palladium nanoparticles were for the first time synthesized by seed-mediated techniques in the presence of beta-cyclodextrin (beta-CD). Palladium and silver seeds were prepared by reduction of palladium or silver ions with sodium borohydride in the presence of sodium citrate dihydrate as a stabilizer. Seeds were then injected into a growth solution containing the same Pd (or Ag) precursor, ascorbic acid (as a weak reducing agent), and beta-CD. Using beta-cyclodextrin impacts the final morphology of silver nanoparticles through a strong capping effect slowing down the growth regime and shifting it to thermodynamic-controlled conditions. Adjusting the beta-CD/Ag molar ratio can lead to the selective formation of multiply twinned icosahedral particles presenting mainly {111} facets. On palladium, beta-cydodextrin selectively led to the controlled aggregation of primary nanopartides into nanodendrites or multipods. After deposition on TiO2, these nanostructured Pd catalysts show excellent activity for the hydrogenation of cinnamaldehyde.