Our recent results on the preparation of silica-based nanoporous materials with unique structures and porosities, derived from various starting materials, have been reviewed. The interactions between various silicate-based starting materials and organic substances are quite important to control the structures and morphologies. The main contents are 1) design of two dimensional nanospaces using layered silicates, 2) morphological control of mesoporous silica, and 3) self-directed systems derived from organoalkoxysilanes. In the section 1), both the utilization of interlayer space of layered silicates by introducing various organic compounds and the formation of three dimensional frameworks from layered silicates have been presented. In the section 2), the development of mesoporous silica and the formation of mesoporous films and nanoparticles have been reported. In the section 3), self-organization of hydrolyzed organoalkoxysilanes under controlled conditions to form mesostructured materials with designed structures and unique characters has been presented. The information presented here will be useful for future developments of materials design of silicate-based functional materials.

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In a luminescent metal complex, the singlet excited state readily converts the excitation energy to the triplet state by increasing the spin-orbit coupling due to the presence of a heavy atom such a metal ion. The emission is called phosphorescence, which can be frequently observed even at room temperature. This review indicates the problems that inorganic chemists may confront while measuring the emission spectra and the emission quantum yields of metal complexes and introduces the IUPAC project to prepare the guidelines for the measurements. Common textbooks in photochemistry usually aim at the physical and/or organic chemists, and they are not always suitable for inorganic chemists who measure the room-temperature phosphorescence. This review describes the procedures for measuring the emission spectra and the quantum yields of the metal complexes in solution from the viewpoints of selection of solvent, sample concentration, de-aeration, and temperature control. It describes both the relative and absolute methods to determine the emission quantum yields. It further indicates that the measurements of solid-state samples are much more difficult than solutions and recommends that the experimental conditions are reported in as much details as possible.

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Coordination polymers (CPs) or metal-organic frameworks (MOFs) are attractive porous materials because of their potential applications such as molecular storage, separation, heterogeneous catalysis, chemical sensing and others. Recently, nano-sized MOFs have been studied as drug delivery vehicles and biomedical imaging agents. Despite the growing interest on MOFs in the biological field, their instability and poor biocompatibility restrict their application to biomaterials. In order to improve the stability and to provide biocompatibility, surface modification of MOFs has been advanced by using a thin silica shell, hydrophilic organic polymers (PEG and PVP) and biomolecules. In this topic, I focus on the recent researches on the surface modification of MOF nanoparticles with biomolecules such as nucleic acid, lipid bilayer and protein. The MOF nanoparticles covered with biomolecules exhibit increased stability under physiological condition, and enhanced cellular uptake compared with unmodified MOF nanoparticles. These results clearly indicate that biomolecule conjugation to MOFs is a useful strategy for creating novel biomaterials.

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Ruthenium complexes are used as effective sensitizers for the dye-sensitized solar cells. The electrons are excited from the HOMO (metal) to LUMO (ligand), and then injected into the titania conduction band in such solar cells. Recently, titanium atom on the titania surface was coordinated to the organic ligands such as dihydroxyl and dicyanomethylene compounds in order to sensitize the titania without the Ru complexes. In such systems, the ligand to metal charge transfer process was induced by light irradiation, indicating the direct electron injection from the HOMO of the ligand to the titania conduction band. Additionally, the organic dye molecules were dispersed into the titania nanoparticles by the sol-gel method in order to enhance the interaction between the dye and titania surface. This resulted in the effective electron injection. The ligand molecules were also dispersed among the titania particles. In the 1,2-dihydroxynaphtalene-dispersing titania, a photocurrent was observed by the direct electron injection process. The electron injection efficiency can be improved by their strong interaction in the narrow spaces surrounded with the titania particles.

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