Yukihisa Watanabe

Catalytic activity of a Ag thin film activated by surface acoustic waves generated on different ferroelectric substrates

Abstract Poled ferroelectric single crystals of 128° Y -cut X -propagation LiNbO 3 , 36° Y -cut X -propagation LiNbO 3 , and 41° Y -cut X -propagation LiTaO 3 with different electromechanical coupling coefficients were employed as a catalyst substrate for Rayleigh and shear-horizontal leaky surface acoustic waves (SAWs). Application of the SAWs caused considerable increases in the catalytic activities for ethanol oxidation of 1.5–50 nm thin film Ag catalysts deposited on the SAW propagation path, and higher activation of the catalyst was brought about by ferroelectric crystals with a higher mechanical coupling coefficient.

Anomalous enhancement of catalytic activity over a Pd thin film by the effects of resonance oscillation generated on a ferroelectric substrate

Abstract A poled ferroelectric lithium niobate single crystal ( z -cut) was employed as a substrate, on the planes of which either a catalytically active Pd or an inactive Al metal was deposited at a thickness of 100 nm. Resonance characteristics were measured, and the effects of resonance oscillation on the catalytic activity for ethanol oxidation were examined. For the Al metal, a negligibly small enhancement of the activity occurred at 343 K, whereas, for the Pd metal, the activity increased dramatically with increasing power at a resonance frequency of 3.4 MHz and amounted to 1880 times larger activity at 3 W. The activation energy of the reaction decreased from 156 to 12 kJ mol −1 with power-on. No activity increase was observed at non-resonance frequency. The effects of resonance oscillation on catalytic activity are discussed.

Activation of a thin film Pd catalyst for CO and ethanol oxidation by surface acoustic waves

Abstract The effects of surface acoustic waves (SAW) on the activity of an oxidized and reduced Pd thin film catalyst, deposited as a thin film on the propagation path, were examined for CO and ethanol oxidation. A 19.4 MHz Rayleigh SAW generated on a 128° Y-cut LiNbO 3 single crystal caused not only higher activity enhancement but also larger changes in the activation energy and reaction orders for CO oxidation over the oxidized than over the reduced Pd surface. The larger SAW effects on the oxidized Pd surface were also observed for ethanol oxidation. The SAW has been shown to have a significant effect on the strongly adsorbed species. The difference in the SAW effects between the oxidized and reduced Pd is explained on the basis of the difference in the contribution of SAW-induced lattice displacement, an electric field and a sonic wave-electron interaction.

Generation of a flexible loop structural ensemble and its application to induced-fit structural changes following ligand binding

Molecular recognition is often mediated by flexible loops that have widely fluctuating structures and are sometimes disordered, but that form particular complex structures following ligand binding. In fact, many loop structures found in the PDB database are too flexible to be determined precisely. A new loop modeling method was therefore developed using force-biased multicanonical molecular dynamics with the implicit solvent model to generate an ensemble of putative loop structures with low free energy values. The method was then used to create ensembles for several flexible loops that were compared with the corresponding NMR and X-ray structures. The induced-fit structural change of dihydrofolate reductase (DHFR) was also predicted from a structural ensemble of ligand-free M20 loop conformations and successive docking simulations.