Fabrication of silica/platinum core-shell particles by electroless metal plating

Abstract An electroless metal plating method was used to form Pt shells on sub-micrometer-sized silica (SiO 2 ) particles fabricated by a sol-gel method. The electroless metal plating method was comprised of three steps: (1) surface-modification of SiO 2 particles with polyvinylpyrrolidone (PVP) (SiO 2 /PVP) or poly-diallyldimethylammonium chloride (PDADMAC) (SiO 2 /PDADMAC), (2) pre-deposition of Pt nuclei or Pt fine particles on the SiO 2 particles by reducing Pt ions in the presence of SiO 2 /PVP particles (SiO 2 /PVP-Pt) or SiO 2 /PDADMAC particles (SiO 2 /PDADMAC-Pt), and (3) growth of the pre-deposited Pt by immersing the SiO 2 /PVP-Pt or SiO 2 /PDADMAC-Pt particles in a Pt-plating solution. The pre-deposition of Pt nanoparticles was successfully performed for the surface-modified SiO 2 particles since the surface modification possibly strengthened the affinity between the SiO 2 particle surfaces and Pt ions. The Pt nanoparticles were pre-deposited more uniformly in the case of PVP because the pre-deposition took place more slowly for the PVP, which provided uniform surface-modification followed by the uniform pre-deposition of Pt nanoparticles. The formation of Pt shells was successfully performed on the SiO 2 /PVP-Pt particles in the electroless metal plating process because Pt nuclei were generated by the reduction of H 2 PtCl 6 and then further deposited on the Pt particle surfaces on the SiO 2 /PVP-Pt particles.