Search

The present work proposes a method for fabricating metallic zinc (Zn) nanoparticles in aqueous solution. An aqueous colloidal solution of metallic Zn nanoparticles was prepared from Zn acetate by electrolysis under ultrasonic irradiation in water. Transmission electron microscopy and X-ray diffractometry revealed that metallic Zn nanoparticles with a crystal structure of hexagonal and a particle size of ca. 130 nm were produced using carbon bars as electrodes. However, the carbon that peeled off with the ultrasonic irradiation was included in the nanoparticles. High-purity metallic Zn nanoparticles with sizes of 30–90 nm could be fabricated using metallic Zn plates as the electrodes. The metallic Zn nanoparticles were chemically stable in both aqueous solution and the atmosphere. The chemically-stable metallic Zn nanoparticles are expected to be applied to catalyst, fabrication of alloy nanoparticles composed of Zn and other metals, anti-rust paint, etc.

An electroless metal plating method was used to form Pt shells on sub-micrometer-sized silica (SiO2) particles fabricated by a sol-gel method. The electroless metal plating method was comprised of three steps: (1) surface-modification of SiO2 particles with polyvinylpyrrolidone (PVP) (SiO2/PVP) or poly-diallyldimethylammonium chloride (PDADMAC) (SiO2/PDADMAC), (2) pre-deposition of Pt nuclei or Pt fine particles on the SiO2 particles by reducing Pt ions in the presence of SiO2/PVP particles (SiO2/PVP-Pt) or SiO2/PDADMAC particles (SiO2/PDADMAC-Pt), and (3) growth of the pre-deposited Pt by immersing the SiO2/PVP-Pt or SiO2/PDADMAC-Pt particles in a Pt-plating solution. The pre-deposition of Pt nanoparticles was successfully performed for the surface-modified SiO2 particles since the surface modification possibly strengthened the affinity between the SiO2 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 SiO2/PVP-Pt particles in the electroless metal plating process because Pt nuclei were generated by the reduction of H2PtCl6 and then further deposited on the Pt particle surfaces on the SiO2/PVP-Pt particles.

An electroless metal plating method was used to form Pt shells on sub-micrometer-sized titania particles fabricated by a sol–gel method. The electroless metal plating method comprised three steps: (1) surface-modification of titania particles with poly(diallyldimethylammonium chloride) (PDADMAC) (TiO 2 –PDADMAC), (2) pre-deposition of Pt nuclei or Pt fine particles on the titania particles by reducing Pt ions in the presence of TiO 2 –PDADMAC particles (TiO 2 –Pt) and (3) growth of the pre-deposited Pt by immersing the TiO 2 –Pt particles in a Pt-plating solution. TEM observation and X-ray diffractometry revealed that surface modification with PDADMAC promoted the pre-deposition of Pt and that crystalline Pt shells with a thickness of approximately 25 nm were successfully produced on the titania particles using initial concentrations of 0.8 × 10 −3 M TiO 2 and 0.375 × 10 −3 M Pt in the Pt-plating solution.