We demonstrate that Pd nanospheres exhibit much higher susceptibility of the localized surface plasmon resonance (LSPR) peak to medium refractive index changes than commonly used plasmonic sensing materials such as Au and Ag. The susceptibility of spherical Au nanoparticle-core/Pd-shell nanospheres (Au/PdNSs, ca. 73 nm in diameter) was found to be 4.9 and 2.5 times higher, respectively, than those of Au (AuNSs) and Ag nanospheres (AgNSs) having similar diameters. The experimental finding was theoretically substantiated using the Mie exact solution. We also showed from a quasi-static (QS) approximation framework that the high susceptibility of Pd LSPR originates from the smaller dispersion of the real part of its dielectric function than those of Au and Ag LSPR around the resonant wavelength. We conclude that the Pd nanoparticle is a promising candidate of "the third plasmonic sensing material" following Au and Ag to be used in ultrahigh-sensitive LSPR sensors.

The pentavalent bismuthate BaBi 2 O 6 was prepared by a lowtemperature hydrothermal reaction using NaBiO 3 .nH 2 O and Ba (OH) 2 .8H 2 O as starting materials. The X-ray powder diffraction pattern was indexed with a hexagonal cell (space group: P-31 m), the same as a PbSb 2 O 6 -type crystal. The crystal structure of this compound was refined using synchrotron X-ray powder diffraction data. The cell parameters were found to be a = 5.57534(6) and c = 5.7381(1) Å and the final reliability (R) factors obtained by Rietveld analysis were R wp = 5.15 % and R p = 3.62 %. This compound exhibited profound photocatalytic activity for phenol decomposition under visible light irradiation.

Using the layer-by-layer method, 12 tungsto(VI) phosphoric acid (PW12) and TiO2 hybrid thin films were prepared. In 2-propanol decomposition, two-bilayer thin films (ca. 15 nm) showed more rapid decomposition than control TiO2 and PW12 films under both UV and visible light illumination. Visible light illumination was required for continuous 2-propanol decomposition. Photocatalytic decomposition activity depends on the number of bilayer coatings, the top coating, and the organic compounds for decomposition. On the basis of the wavelength dependence of the hybrid thin films, a reaction scheme for this system was discussed.

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