Ag particles supported on a metal oxide support have been used for various catalytic reactions (e.g. selective oxidation of ethylene). To improve the catalytic activity, size reduction of Ag particles is desired. However, it is challenging to obtain small Ag particles due to the low Tammann temperature of Ag. In this study, we successfully deposited 20 wt% of Ag clusters (~2 nm) onto TiO₂ using flame spray pyrolysis. The Ag clusters were stabilized by strong metal-support interaction (SMSI) between Ag and TiO₂ which was induced in the combustion reaction zone. SMSI formed TiOx as confirmed by X-ray diffraction. The amount of TiOx depended on the flame conditions and Ag content (10–40 wt%). The surface area of Ag clusters was estimated by H₂ pulse titration. The Ag surface area increased with Ag content up to 20 wt%, and by further increasing the Ag content to 40 wt%, the surface area did not change. The stability of Ag clusters depended on the Ag content, the flame conditions, and the specific surface area of the titanium oxide support. In the future, we will explore catalytic activity of FSP-made Ag clusters for some reactions.

Hemolysis assay using red blood cells has been widely used as the simplest cytotoxicity test for nanoparticles. Nevertheless, the hemolytic action mechanism of nanoparticles is still poorly understood. In this study, the hemolytic action of silica nanoparticles with different particle diameters (5–120 nm) and surface functional groups (none, amino group, and carboxyl group) was investigated under different exposure environments: temperatures (4–43°C) and phosphatic buffered saline solutions (additive-free, serum added, and serum albumin added). Adding to the hemolysis assay, the adhesion number of nanoparticles to red blood cells and the aggregation/dispersibility of red blood cells were measured, whereby the overall picture of the hemolytic action mechanism of nanoparticles was given.

We have developed a phase retrieval holography module for microparticle measurement. The system that this module has comprises two cameras connected to a single-board computer (SBC) with a graphics processing unit (GPU), a diode-pumped solid-state green laser, and a beam splitter. Furthermore, the GPU provides real-time reconstruction. The system can record the shapes and positions of particles falling in a static flow in a three-dimensional volume as two holograms generating an interference pattern. Phase retrieval holography with two holograms solves the twin image problem that arises due to the lack of phase information. We also present the requirement of this module for experimentally recording and numerically reconstructing holograms of particles. Finally, we conclude that holographic measurement, limited to use in a laboratory, can be used for in-line/ on-line measurement of powder production processes.

In order to functionalize the powders, it is important to understand the relationship between the powders’ structure and their functionalities. As one of the techniques, the Mahalanobis-Taguchi system (MTS) has been utilized because that effective variables which improve accuracy of classification can be visualized. The surface-roughness-related variables were the effective powder structure which improve accuracy of classification into male/female of Japanese beetles larval droppings as the model powders. Considering that binder concentration in the females’ dropping was higher than in the males’ dropping, the females’ droppings could be deformed during molding process through the larval gut. The MTS can be expected as the effective way to improve the accuracy of the classification by visualization of the relationship between powder structure and functionalities without individual differences.

Si-Si σ bonds exhibit reactivity and physical properties similar to those of C=C π bonds. The research group is utilizing the flexibility of the Si–Si σ bond and the σ–π conjugation with aromatic substituents to investigate the synthesis, structure, and physical properties of various disilane-bridged macrocycles. We have already studied the synthesis and temperature-dependent behavior of a dimer (tetrasilacyclophane). Here we report on the synthesis of trimeric and tetrameric macrocycles and their crystal structures at different temperatures.