Yuki Nakagawa

Low temperature hydrogenation of iron nanoparticles on graphene.

Hydrogenation of iron nanoparticles was performed both computationally and experimentally where previously chemically-bonded iron hydride is considered to be unachievable under ordinary conditions. Density functional theory (DFT) calculations predict that hydrogenated iron nanoparticles are stabilized on a single-layer graphene/Cu substrate. Experimentally, iron nanoparticles were deposited onto a graphene/Cu substrate by vacuum deposition. Hydrogenation was done at 1atm of hydrogen gas and under liquid nitrogen. Mass spectrometry peak confirmed the hydrogen release from hydrogenated iron nanoparticles while a scanning transmission electron microscopy is used in order to link a geometrical shape of iron hydride nanoparticles between experimental and theoretical treatments. The hydrogenated iron nanoparticles were successfully synthesized where hydrogenated iron nanoparticles are stable under ordinary conditions.

Use of decomposable polymer-coated submicron Cu particles with effective additive for production of highly conductive Cu films at low sintering temperature

A method for producing Cu films with low resistivity, based on low temperature sintering, is demonstrated. The Cu inks for preparing conductive Cu films consisted of Cu particles that were coated with a decomposable polymer (poly(propylenecarbonate), PPC) as well as a self-reducible copper formate/1-amino-2-propanol (CuF–IPA) complex as an additive. The sintering temperature used in this study was as low as 100 °C. Following sintering at a temperature of 100 °C, the lowest reported resistivity (8.8 × 10−7 Ω m) was achieved through the use of Cu-based metal–organic decomposition (MOD) inks. This was due to the dual promotional effects of the aminolysis of PPC with IPA and the pyrolysis of the CuF–IPA complex.

Hydrogen Absorption of Palladium Thin Films Observed by in Situ Transmission Electron Microscopy with an Environmental Cell

A window type of the environmental cell system for a high-voltage electron microscope was developed and applied to in situ observation of a palladium (Pd) thin film. For in situ hydrogenation of Pd thin films, the distances of the lattice fringes were 0.20 and 0.23 nm, which correspond to the lattice d spacings of β-phase (200) and (111) planes. Expansion of the Pd lattice happened as a result of phase transformation from the α phase to the β phase. In particular, the lattice fringes were clearly distinguished, and the dislocation behavior during Pd hydrogenation was easily recognized according to the corresponding inverse fast fourier transform images. Furthermore, significant growth in the number of dislocations was observed at the grain boundary during increasing hydrogen pressure in the cell.

Homogeneity of Curie Temperature in La (Fe, Si)

The microstructure and magnetic properties for LaFe_10.85 Co_0.65Si _1.5C_0.2, LaFe_11.5Si_1.5C_0.2 and LaFe_10.85Co_0.65Si_1.5 compounds were investigated. The ingots were prepared by 5 kilogram Vacuum Induction Melting Furnace. Then LaFe _10.85Co_0.65Si_1.5C_0.2 and LaFe_11.5Si_1.5C_0.2 thin strips were prepared by the strip-casting process. The DSC measurement shows that the maximum latent heat of LaFe_11.5Si_1.5C_0.2 thin strips has been obtained after annealing at 1353 K for 12 h, longer time annealing seems to be no good for latent heat. Substitute Co for Fe could cause inhomogeneous distribution of Curie temperature (T_C) in the bulk ingots, but the inhomogeneity can be improved by preparing the strip from the ingot. Under magnetic field changes of 0-1.5 T, the magnetic entropy change near the Curie temperature was about -11.1 J/kg· K and -4.0 J/kg· K for LaFe_11.5Si_1.5C_0.2 and LaFe_10.85Co_0.65Si_1.5C_0.2, respectively.

_{13}

The electrical conductivity of the organic Mott insulator ET-F2TCNQ (ET = bis(ethylenedithio)tetrathiafulvalene, F2TCNQ = 2,5-difluoro-7,7,8,8-tetracyanoquinodimethane) crystal was found to be enhanced by conjugation with a tetrathiafulvalene (TTF) single crystal on its surface; surface sheet resistance decreased from 5 × l05 to 2 × 103 Ω/sq. The mechanism of this decrement was investigated through optical and atomic force microscopy measurements at the interface. When TTF was conjugated to the ET-F2TCNQ crystal, electron injection from TTF and complex formation between TTF and F2TCNQ occurred. Neutral ET molecules were consequently generated at the interface, and this charge doping broke the Mott insulating state.

Compounds by Co and C Doping

In the ionic charge-transfer (CT) complex composed of bis(ethylenedithio)tetrathiafulvalene (ET) and 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ), C10H8S8·C8Cl2N2O2, the donor and acceptor molecules both form centrosymmetric dimers associated by strong face-to-face π-π interactions. The disordered DDQ molecules form a one-dimensional π-stacked column, while the ET molecules form a two-leg ladder through additional short S···S contacts between adjacent π-π-bonded dimers. The crystal structure of ET-DDQ revealed in this study will provide a valuable example of the two-leg spin ladder system, which has rarely been reported for ET-based CT complexes.

Carrier doping to the organic Mott insulator by conjugating with tetrathiafulvalene

A number of autoimmune diseases are associated with the genotypes of human leukocyte antigen class II (HLA), some of which present peptides derived from self-proteins, resulting in clonal expansion of self-reactive T cells. Therefore, selective inhibition of self-peptide loading onto such disease-associated HLA could ameliorate the diseases. To effectively identify such compounds, in this study, we established, for the first time, a cell- and 96-well microplate-based high-throughput screening system for inhibitors of antigen presentation. A panel of DRB1 genes plus DRA*01:01 gene were expressed in HEK293T cells and in 3T3 cells, and their binding with biotinylated known self-antigen peptides was measured by flow cytometry. HLA-DR1 (DRB1*01:01) and DR15 (DRB1*15:01) showed a high affinity with myelin basic protein peptide (MBP83-98). Therefore, in 96-well plate wells, MBP83-99 was allowed to bind to DR1 or DR15 on 3T3 cells in competition with a test compound, and the HLA-bound peptide was detected by streptavidin-conjugated β-galactosidase, thereby identifying inhibitor compounds for rheumatoid arthritis or multiple sclerosis. Our assay system has a potential for broad applications, including designing peptide vaccines.

The bis(ethylenedithio)tetrathiafulvalene-based ionic charge-transfer complex with 2,3-dichloro-5,6-dicyano-p-benzoquinone.

Key descriptors representing the desorption temperature of ammonia borane against hydrides and chlorides are investigated and applied to machine learning. The desorption temperature of ammonia borane with hydrides and chlorides is experimentally measured and a database is constructed. The database indicates a correlation between the desorption temperature and electronegativity. A support vector machine with selected descriptors from the database reveals the optimal amounts of CuCl2 and AgCl needed for decreasing the desorption temperature of ammonia borane. Prediction of the electronegativity that would achieve the desorption temperature is also revealed where the crystal structure is also found to be a key descriptor. Thus, electronegativity and crystal structures are revealed to be key descriptors that predict the desorption temperature of ammonia borane with a chemical compound. This would essentially lead towards finding the optimal amount of dopants and ideal dopants with a minimum number of experiments.