Yasuhiro Niwa

  • Citations Per Year
Learn More
R. M. Law, W. Peters, C. Rödenbeck, C. Aulagnier, I. Baker, D. J. Bergmann, P. Bousquet, J. Brandt, L. Bruhwiler, P. J. Cameron-Smith, J. H. Christensen, F. Delage, A. S. Denning, S. Fan, C. Geels, S. Houweling, R. Imasu, U. Karstens, S. R. Kawa, J. Kleist, M. C. Krol, S.-J. Lin, R. Lokupitiya, T. Maki, S. Maksyutov, Y. Niwa, R. Onishi, N. Parazoo, P. K.(More)
Understanding the initial nucleation mechanism of monodisperse nanocrystals (NCs) during synthesis process is an important prerequisite to control the desired sizes and to manipulate the properties of nanoscale materials. The acquisition of information for the small nanocluster nucleation process, however, still remains challenging. Here, using a(More)
P. K. Patra, R. M. Law, W. Peters, C. Rödenbeck, M. Takigawa, C. Aulagnier, I. Baker, D. J. Bergmann, P. Bousquet, J. Brandt, L. Bruhwiler, P. J. Cameron-Smith, J. H. Christensen, F. Delage, A. S. Denning, S. Fan, C. Geels, S. Houweling, R. Imasu, U. Karstens, S. R. Kawa, J. Kleist, M. C. Krol, S.-J. Lin, R. Lokupitiya, T. Maki, S. Maksyutov, Y. Niwa, R.(More)
The dynamics of the local electronic and geometric structures of WO3 following photoexcitation were studied by femtosecond time-resolved X-ray absorption fine structure (XAFS) spectroscopy using an X-ray free electron laser (XFEL). We found that the electronic state was the first to change followed by the local structure, which was affected within 200 ps of(More)
Of late, battery-driven high-performance gas sensors have gained acceptability in practical usage, whose atomic-scale structure has been revealed by μ-fluorescence X-ray absorption fine structure analysis. We studied the chemical distribution of Pd species in the Pd/Al2O3 catalyst overlayer in the real gas sensor at various degrees of deterioration. In a(More)
Ultrafast excitation of photocatalytically active BiVO4 was characterized by femto- and picosecond transient X-ray absorption fine structure spectroscopy. An initial photoexcited state (≪500 fs) changed to a metastable state accompanied by a structural change with a time constant of ∼14 ps. The structural change might stabilize holes on oxygen atoms since(More)
Formation and oxidation processes of PdZn nanoparticles on ZnO were successfully observed by means of in situ time-resolved X-ray absorption fine structure spectroscopy (XAFS), and the analysis of data on near-edge (XANES) and extended (EXAFS) structures revealed detailed changes in Pd during both processes. PdZn nanoparticles were formed on ZnO through a(More)
We measured the in situ polarization-dependent X-ray absorption fine structure of platinum nanoparticles (PtNPs) deposited on a flat highly oriented pyrolytic graphite (HOPG) substrate under electrochemical conditions using a back-side illumination method. In this method, the thin HOPG substrate with PtNPs deposited on one side was used as a window for(More)
Synchrotron X-ray-induced reduction of Au ions in an aqueous solution with or without support materials is reported. To clarify the process of radiation-induced reduction of metal ions in aqueous solutions in the presence of carbon particles as support materials, in situ time-resolved XANES measurements of Au ions were performed under synchrotron X-ray(More)