Nanostructured plasmonic materials, not only metals such as Au and Ag but also hydrogen-doped semiconductors such as H_xMoO₃, represent another class of important materials that strongly absorb visible light in a wide range of the solar spectrum owing to their localized surface plasmon resonance (LSPR). To harvest and convert the abundant sunlight to drive chemical reactions, the rational design and precise manipulation of plasmonic nanostructures are important. Intriguingly, in addition to acting as a visible light absorber, plasmonic materials themselves can also directly induce chemical reaction as heterogeneous catalysts. The integration of plasmonic and catalytic properties into nanostructured materials paves a new route for visible light driven photocatalysis, and has shown great potential in selective catalytic transformations in a mild manner compared with thermal reactions.

Photochemically induced dynamic electron polarization (DEP) of free radicals has been utilized in time-resolved (TR) ESR spectroscopy for long time to understand photoreaction dynamics and mechanisms. The present review article focuses on more recent progresses of DEP applications to advanced TR-ESR spectroscopic measurements on some photochemical processes such as singlet oxygen reactions, enhancement of DEP by xanthene dye photoirradiation, and photo-induced radical addition reactions to olefins. The former two topics are related to experimental findings of particularly large DEP generation by the radical-triplet pair mechanism. The latter topics is concerning with DEP assisted electron spin echo detection of reacting radicals with olefins utilizing pulsed ESR method. Details of these applications were described and some potentials of these novel spectroscopic methods were mentioned and argued.

The steady-state/time-resolved spectroscopic and photoelectrochemical properties of dye-dispersing amorphous titania gels were investigated to clarify the influence of the dye–titania interaction on their photoelectric conversion performance. The photocurrent quantum efficiency of the dye-dispersing titania electrodes was remarkably increased by a steam treatment due to the crystallization and densification of the titania layer and the dye–titania surface complex formation. The electron injection from the dye to the steam-treated titania dispersing the dye was confirmed to be more efficient than that in the conventional dye-adsorbing titania. In the dye-sensitized solar cells using crystalline titania electrodes coated with N3 dye-dispersing amorphous titania, the dye-dispersing titania layer prevented interaction between the dye molecules and back electron transfer from the titania to the electrolyte. The charge separation and photoelectric conversion performance of the solar cells were improved by forming the specific dye-dispersing titania layer.

Researches on coordination compounds with lanthanide arrangement get much attentions for their photophysical properties. Here, we describe characteristic optical properties of clusters and coordination polymer crystals with well-organized lanthanide structures. The lanthanide clusters with a Ln-O-Ln lattice provide characteristic photoluminescence properties and opto-magneto properties (i.e., Faraday effect). On the other hand, the coordination polymer crystals with extended lanthanide arrangement via linker ligand demonstrate characteristic luminescent properties, such as a temperature sensitive luminescence or triboluminescence. These photochemistries are expected to open up a new field of advanced lanthanide materials.

Plasmonic properties of metal nanoparticles can be especially controlled by their shapes. However, anisotropic metal nanoparticles are thermally and chemically less stable than spherical ones. Thus, it is very important to improve their stabilities so as to apply their unique optical properties to practical devices. In this study, we successfully improved the stabilities of rod-shaped gold nanoparticles (gold nanorods) and of plate-shaped silver nanoparticles (silver nanoplates) by coating with thin titanium oxide films.