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Hirotaro Mori

Publications and source records attributed to Hirotaro Mori.

7 recordsLinked to original sources
PubMed2006

Synthesis and photophysical properties of EuS nanoparticles from the thermal reduction of novel Eu(III) complex.

EuS nanoparticles were synthesized by the thermal reduction of single source precursor (SSP), (PPh4)[Eu(S2CNEt2)4].2H2O, under microwave irradiation. The average size of the EuS nanoparticles was found to be 8 nm (3-16 nm in size). The organic products on the EuS surface were observed by using FT-IR, NMR, and MS analyses. We have found that these are resulted from the chemical reactions of SSP and cover the nanocrystal surface. A thermal reaction of SSP gave EuS nanoparticles and the organic product (*SCN(Et)2). The organic product would make a dimmer, (Et)2NC(S)-(S)CN(Et)2, by the couping of the radicals formed in the thermal reaction and/or thiopolymer in the solution through the polymerization of the radicals. The effective surface modification by the organic products led to protection of the EuS surface, resulting in the formation of the strongly luminescent EuS nanoparticles at room temperature (emission peak = 350 nm, fwhm = 58 nm, emission quantum yield = 27 +/- 5%).

Journal Article↗
PubMed2005

In situ HVEM study on copper oxidation using an improved environmental cell.

A window-type environmental cell that can be used over the temperature range from room temperature to approximately 1000 K was improved by incorporating a new window material that increases resolution and contrast in high voltage electron microscopy. With this improvement, the resolution was a few nanometers and the maximum pressure in the cell was approximately 1.3 x 10(4) Pa. Using this new window-type environmental cell, oxidation of copper and reduction of copper oxides, which occur through gas (oxygen or hydrogen)-solid (copper metal) reactions, have been successfully observed in situ, i.e. the formation process of oxides (Cu --> Cu2O --> CuO) and their subsequent reduction (CuO --> Cu) in the cell. The growth process of CuO whiskers on a thick (50 microm) Cu film was also observed in situ. It was found that whisker growth occurs at the tips of whiskers.

Journal Article↗
PubMed2005

Asymmetrically modified silica particles: a simple particulate surfactant for stabilization of oil droplets in water.

Spherical silica particles that are able to assemble at a phase boundary of a dual-phase mixture of water and an immiscible organic solvent were prepared by a partial modification of their surface hydroxyl groups with an alkylsilylation agent. Scanning electron microscopic observation of these particles in which their remaining surface hydroxyl groups had been selectively modified with colloidal gold particles revealed that each particle has an asymmetric surface structure: one side of the surface is hydrophilic and the other is hydrophobic. We found that these particles could form a micellar structure in water in the presence of an organic solution of a toluene/polystyrene mixture. The micellar structure was evidenced by formation of golf-ball-like polystyrene particles with dimples imprinting morphologies of the hydrophobic part of modified silica particles.

Journal Article↗
PubMed2005

Scientific Grid activities and PKI deployment in the Cybermedia Center, Osaka University.

The Cybermedia Center (CMC), Osaka University, is a research institution that offers knowledge and technology resources obtained from advanced researches in the areas of large-scale computation, information and communication, multimedia content and education. Currently, CMC is involved in Japanese national Grid projects such as JGN II (Japan Gigabit Network), NAREGI and BioGrid. Not limited to Japan, CMC also actively takes part in international activities such as PRAGMA. In these projects and international collaborations, CMC has developed a Grid system that allows scientists to perform their analysis by remote-controlling the world's largest ultra-high voltage electron microscope located in Osaka University. In another undertaking, CMC has assumed a leadership role in BioGrid by sharing its experiences and knowledge on the system development for the area of biology. In this paper, we will give an overview of the BioGrid project and introduce the progress of the Telescience unit, which collaborates with the Telescience Project led by the National Center for Microscopy and Imaging Research (NCMIR). Furthermore, CMC collaborates with seven Computing Centers in Japan, NAREGI and National Institute of Informatics to deploy PKI base authentication infrastructure. The current status of this project and future collaboration with Grid Projects will be delineated in this paper.

Computational Biology↗
PubMed2003

In situ HREM study on the structural instability of isolated nanometre-sized alloy particles in the Sn-Bi system.

The structural instability of isolated nm-sized alloy particles has been investigated by in situ transmission electron microscopy, using particles in the Sn-Bi system. In a pure tin (Sn) particle, no structural fluctuation was induced under electron-beam irradiation. In a tin-rich solid solution particle, an orientational fluctuation took place at a rate of approximately once per 1-3 s. In a high concentration alloy particle with a two-phase microstructure, a structural fluctuation occurred at a rate of a few hertz. Namely, the fluctuation became more frequent with increasing bismuth (Bi) concentration, no matter whether it consists of a single phase or multiple phases. A good parallelism can be found between this fluctuation enhancement with bismuth concentration and the fact that the free-energy difference between a solid particle and the corresponding liquid one decreases continuously with bismuth concentration and approaches a value close to zero at the eutectic composition. These results lead to a view that a nm-sized solid particle exhibits a structural instability under electron-beam irradiation when the free-energy difference between a solid particle and the corresponding liquid one is reduced to a value close to zero.

Journal Article↗