Poly(N-vinylisobutyramide)-stabilized platinum nanoparticles: synthesis and temperature-responsive behavior in aqueous solution

Colloidal platinum nanoparticles in the size range of 10–30 Å were prepared in ethanol–water mixture with an ethanol volume fraction of 0.8 via the reduction of PtCl62− by ethanol in the presence of poly(N-vinylisobutyramide) (PNVIBA). The formation of PNVIBA–Pt colloidal dispersion was followed by UV-visible spectroscopy. The PNVIBA–Pt nanoparticles can be easily transferred into distilled water, and then TEM and AFM studies of the nanoparticles have been performed. The particle size and size distribution are dependent on the monomeric unit/Pt molar ratio and the molecular weight of stabilizer, PNVIBA. The colloidal PNVIBA–Pt nanoparticles exhibit inverse temperature solubility and a cloud-point temperature of 38.9°C in water. The catalytic behaviors of PNVIBA–Pt nanoparticles were studied for the hydrogenation of allyl alcohol in water. At temperatures lower than the cloud-point, the temperature dependence of reaction rate follows normal Arrhenius behavior. Above 40°C, however, the catalystʹs activity is abruptly decreased owing to the phase separation of PNVIBA–Pt from the continuous phase containing the substrate. On cooling the reaction solution below the cloud-point, the catalyst redissolves and its activity is renewed to the original level.