Kazuki Yoshii

Platinum nanoparticle immobilization onto carbon nanotubes using Pt-sputtered room-temperature ionic liquid

Establishment of a facile Pt nanoparticle–SWCNT composite fabrication method that never requires a laborious pretreatment of SWCNTs or any chemical reagent was achieved by using Pt-sputtered RTILs.

Ultrathin oxide shell coating of metal nanoparticles using ionic liquid/metal sputtering†

The surface coating of metal nanoparticles resulting into core–shell structures is expected to improve the physicochemical properties of the nanoparticle cores without changing their size and shape. Here, we developed a novel strategy to coat Au, AuPd or Pt catalyst cores having average sizes smaller than 2.5 nm, which were pre-synthesized in ionic liquids by corresponding metal sputtering, with an extremely thin In2O3 layer (ca. <1.5 nm) by sputter deposition of indium in a room-temperature ionic liquid. The metal cores of Au or AuPd in core–shell particles exhibited superior stability against heat treatments or during electrocatalytic reactions compared to the corresponding bare metal particles. The In2O3 shell coating considerably enhanced the durability of electrocatalytically active Pt particles (1.2 nm). This sequential metal sputter deposition of different metals in ionic liquids will considerably contribute to the exploitation of key nanostructured components for next-generation energy-conversion systems.

Highly durable Pt nanoparticle-supported carbon catalysts for the oxygen reduction reaction tailored by using an ionic liquid thin layer

Pt nanoparticles monodispersed in an ionic liquid (IL), which can be readily prepared by magnetron sputtering onto an IL, are a key material for tailoring highly durable Pt nanoparticle-supported carbon electrocatalysts, e.g., Pt nanoparticle-supported single-walled carbon nanotubes (Pt-SWCNTs) and Vulcan® XC-72 (Pt-Vulcan®), for the electrochemical oxygen reduction reaction. The durability largely surpasses that of one of the commercially available Vulcan® XC-72-based catalysts, TEC10V30E. The differences were very obvious from the results of electrochemical measurements, ex situ TEM observation, and in situ SEM/STEM observation; that is, considerable damage by carbon corrosion was recognized for the TEC10V30E, but it was not the case for the Pt-SWCNT and Pt-Vulcan®. The unexpected high durability should be due to the suppression of carbon corrosion by the ionic liquid thin layer that exists between the Pt nanoparticles and carbon support.

Emission properties of platinum(II) terpyridyl complexes with hydrophobic poly-l-glutamic acid

The reaction of sodium salt of poly-l-glutamic acid (P(Glu)) with didodecyldimethylammonium (DDA) bromide was demonstrated to afford P(Glu)-DDA, which was confirmed to form the α-helical structure even in methanol. The introduction of 0.2 equiv. amount of the platinum(II) complex [Pt(trpy)C = CPhC12H25-p](OTf) (trpy = 2,2′,6′,2″-terpyridine; PtC 12 ) into P(Glu)-DDA in methanol was found to induce the aggregation of platinum(II) complexes, resulting in the exhibition of the triplet metal-metal-to-ligand charge transfer emission. Such synergistic effect was not observed in the case of the platinum(II) complex [Pt(trpy)C = CPh](OTf) (PtH), wherein the emission intensity based on metal-to-ligand charge transfer/ligand-to-ligand charge transfer was increased.