(112j) Shape-Controlled Synthesis of Platinum Nanoparticles and Their Catalytic Effect on the Reduction of Aromatic Nitro Compounds

The field of nanocatalysis has been a very active area of research recently. Most of the studies in the homogeneous colloidal nanocatalysis field involve use of mainly spherical nanoparticles or nanoparticles of undetermined shape. There are very few studies known in which catalysis is conducted with nanoparticles of specific shape in colloidal solution. Nanoparticles of different shapes have different facets. Furthermore, they have different fractions of atoms located at different corners, edges, and at different defects. To study the effect of shape on catalysis, platinum particles of dominantly tetrahedral, cubic, and spherical shape were prepared in colloidal solution. The procedure allowed the alteration of the nanoparticles' shape by varying the ratio of polymer stabilizer to platinum cations and also by the employment of a different polymer. The three prepared catalysts of tetrahedral, cubic, and spherical shape were then used to catalyze two reactions: the reduction of 4-nitrophenol via NaBH₄ and the reduction of 4-nitrophenol via H₂ gas. The tetrahedral shaped catalyst showed the highest activity, followed by spherical and cubic. The desired product of the reactions, 4-aminophenol was formed with all three catalysts, which was confirmed by UV-vis and mass spectroscopy.