We have two representative projects.
1: New Organic Transformations in Supercritical Water
One of the most promised green reaction fields for many chemical reactions is water. We use supercritical water (Tc; 374 °C, Pc; 22.1 MPa) as a reaction medium for organic transformations, since it shows quite unique properties, such as low polarity, low viscosity, high diffusion ability, and good solubility of organic compounds, different from ambient water and steam. We have shown a new aspect of biomasses by combination of simple reaction of supercritical water degradation of saccharides and direct reduction of alcohols or catalytic hydrogenation of olefins in one-pot single-step reactions. Thus, bulk biomasses can be used as hydrogen donors in one-pot single-step direct organic transformations in supercritical water.
2: Organic-inorganic Hybrid Nanoparticle Synthesis
Spherical mesoporous metal oxide nanoparticles are one of the functional materials especially in the fields of catalysts, semiconductors, and drug delivery, etc. We have defined a new category of nanoparticles as mesoporously architected roundly integrated metal oxide (MARIMO) nanoparticles, because their shapes resemble those of MARIMO (Cladophora aegagropila) moss balls. We have succeeded in synthesizing solid and hollow MARIMO nanoparticles, such as SiO2, ZnO, TiO2, ZrO2, CeO2, etc. by one-pot single-step reaction in fairly short reaction time (several min) using supercritical fluids as reaction media. Decoration of these MARIMO nanoparticles by many kinds of metal atoms in lattice doping, core-shell, yolk-core-shell, and surface attaching structures has been done. Many of them act as quite effective photocatalysts and chemical catalysts.