Refractive Index Susceptibility of the Plasmonic Palladium Nanoparticle: Potential as the Third Plasmonic Sensing Material

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

Assembly of Mid-Nanometer-Sized Gold Particles Capped with Mixed Alkanethiolate SAMs into High-Coverage Colloidal Films

We investigated the influence of the mixed <i>n</i>-alkanethiolate self-assembled monolayer (SAM) formed on gold nanoparticles (AuNPs: 50.0 ± 3.2 nm in diameter) on their assembly into colloidal films. Dodecanethiol and octadecanethiol were selected as the short- and long-chain alkanethiols, respectively. The mixed SAMs were formed by immersing AuNPs in a mixed alkanethiol solution at different molar ratios. Au colloidal films were fabricated on indium tin oxide substrates by our previously reported hybrid method. The composition of the two alkanethiolates in the SAM was deduced from the intensity ratio of two Raman bands at 1080 and 1105 cm^–1. The surface coverage of the colloidal films increased by forming equimolar or dodecanethiolate-dominant mixed SAMs on AuNPs instead of a pure dodecanethiolate or octadecanethiolate SAM. The highest coverage exceeded 80%. This improvement is attributed to the high dispersion stability of AuNPs covered with equimolar or dodecanethiolate-dominant mixed SAMs

Adsorption Behavior of Rare Earth Metal Cations in the Interlayer Space of γ‑ZrP

Adsorption competencies of rare earth metal cations in γ-zirconium phosphate were examined by ICP, synchrotron X-ray diffraction (SXRD), and ab initio simulation. The adsorption amounts are around 0.06–0.10 per zirconium phosphate. From the SXRD patterns of the adsorbed samples, the basal spacing estimated by <i>c</i> sin β increased linearly with an increasing ionic radius of rare earth metal cation, though <i>a</i> and <i>b</i> lattice constants show no change. These SXRD patterns can be classified into four groups that have different super lattices. The four superlattices have multiplicities of x131, x241, and x221 for the x<i>abc</i> axis, and the location of the rare earth metal cation in the original unit cell changes depending on the superlattice cell. In the x131 superlattice, Yb and Er occupied the site near the zirconium phosphate layer, though La and Ce in the x221 superlattice remained in the center position between the phosphate sheet. For the ab initio simulation of γ-ZrP with the typical rare earth metal cations (Tb, Eu, Dy, and La), the results of simulation show a similar tendency of the position estimated by SXRD refinements

Crystal Structure, Thermal Behavior, and Photocatalytic Activity of NaBiO₃·<i>n</i>H₂O

The crystal structure of NaBiO₃·<i>n</i>H₂O was refined using synchrotron powder X-ray diffraction and was assigned to a trigonal unit cell (space group <i>P</i>3̅) consisting of layered structures formed by edge-sharing BiO₆ octahedra and consisting of an interlayer composed of water molecules sandwiched between two layers of sodium atoms, perpendicular to the <i>c</i> axis. An intermediate phase was observed during the dehydration of the hydrated compound. Density of state calculations showed hybridization of the Bi 6s and O 2p orbitals at the bottom of the conduction bands for both the hydrated and the dehydrated phases, which narrows the band gap and promotes their photocatalytic activity in the visible region