Surfaces of some compliant materials, whose surface layers are harder than the bulk, sometimes form wrinkles with a stripe pattern. The wrinkles have potential impacts on the nanotechnology because the spatial wavelength can be small as submicron scales. The microwrinkles can rearrange in response to the mechanical perturbation, e.g., compression. Here, we focus on a hysteretic behavior of the microwrinkles under a slow cycle of compression and decompression. The local stripe directions change to the compression direction one after another as compression proceeds. However, the stripe patterns upon compression are different from those upon decompression, showing hysteresis in the pattern. We propose a simple phenomenological model that resembles Ising spin models, to understand the basic mechanism of the hysteretic behavior. The model suggests that the hysteresis in the pattern can be caused by the direct coupling between elements.
The relation between the adsorption (conformation) structure and the work function of N-Acetylglycine (CH3-CO-NH-CH2COOH (AcGl)) on Cu(110) surface, has been investigated as a function of the surface temperature using reflection absorption infrared spectroscopy (IRAS), low energy electron diffraction (LEED), X-ray photoemission spectroscopy (XPS), temperature programmed desorption (TPD) and Kelvin probe. AcGl adsorbed disorderly in two dimension on Cu(110) surface. From room temperature to 350 K, ionized AcGl orients broadly perpendicular to the surface via equivalent oxygen atoms of the carboxylate group (Standing up fashion). Above 400 K, as N atom of the AcGl approaches the surface and lies, then, ionized AcGl orients parallel to the surface (Lying-down fashion) and then decompose at around 550 K. The work function increases by AcGl adsorption. The work function of the lying-down fashion is larger than the standing up fashion. It is understood that the effect of the charge transfer from the surface to molecules are more dominant than the effect of the change in the dipole moment of the conformational change of the molecule. It was experimentally clarified that the work function changed by the differences in the states of adsorption in conformation of AcGl.
Activities of photocatalytic water splitting were improved by control of surface morphologies and loading of new cocatalysts. Doping of Ca, Sr and Ba into NaTaO3 photocatalysts led to formation of fine crystals and control of surface morphologies such as construction of nano-step structure. The photocatalytic activities for water splitting were improved by the doping. Photocatalytic overall water splitting on K4Nb6O17, Sr2Nb2O7, KTaO3, NaTaO3, and NaTaO3 doped with La photocatalysts were promoted by loading of nano-sized gold particles. The nano-sized Au worked as an active site for H2 evolution. An IrO2 cocatalyst which was photodeposited from an aqueous solution containing nitrate ions was also effective for overall water splitting. IrO2 functioned as an active site for O2 evolution.
The influence on the gas-surface inelastic collision processes at the well defined surfaces of molecular structural anisotropy, corrugation of the interaction potential and the center-of-mass position of the impinging molecules has been investigated utilizing a supersonic molecular beam technique in conjunction with the recently developed model calculation based on the simple and pure classical binary-collision. The model calculations are found to reproduce the obtained experimental results in details.
The S-S bond dissociation in an isolated (CH3S)2 molecule and the hopping motion of an isolated CH3S molecule on Cu(111) surface were induced by the injection of tunneling electrons from the tip of a scanning tunneling microscope (STM). From the bias voltage dependence for the S-S bond dissociation probability, it was shown that the vibrational excitations of a C-H stretching mode and a combination mode of C-H stretching and S-S stretching in the molecule are responsible for the dissociation reaction induced by inelastically tunneled electrons, respectively. From the bias voltage dependence for the hopping probability of an isolated CH3S molecule on Cu(111) surface, it was shown that the vibrational excitation of C-S stretching in the molecule is strongly contributed to this motion. In the present study, the projected density of state and molecular orbital were also calculated for each adsorption system. From these results, we propose that the molecular vibration induced by the injection of tunnel electrons can be explained by the resonant mechanism.
The electrodeposition reaction in an acidic solution containing Cu2+ and Sn2+ shows, in the presence of a cationic surfactant, a negative differential resistance (NDR) and a current oscillation in a potential region where SnCu alloy is deposited. Depth profiles obtained by Auger electron spectroscopy (AES) have indicated that alloy films deposited during the oscillation have a structure of nano-period multilayers composed of alloys of different compositions. Detailed investigations have revealed that the NDR arises from adsorption of a cationic surfactant (acting as an inhibitor for diffusion of Cu2+ and Sn2+ ions) on the electrode (alloy) surface and the oscillation comes from coupling of the NDR with the ohmic drop in the electrolyte. A notable point is that the NDR appears in a very narrow region of the potential (of about 5 mV or less). This fact strongly suggests that the NDR (and the oscillation) arise from a sudden structural change in an adsorbed surfactant layer such as a phase transition from a gaseous adsorbed layer to a condensed liquid-like one. This conclusion was supported by the experiments on effects of the concentration and the chain length of the surfactant on the NDR.
We developed a UHV-Polarization dependent Total-Reflection Fluorescence Extended X-ray Absorption Fine Structure System (UHV-PTRF-EXAFS System), which enables us to prepare a clean and well-defined oxide single crystal surface. We have determined the adsorption sites and structures of highly dispersed Ni atoms on α-Al2O3(0001) and TiO2(110) using the system. In both cases, Ni atoms adsorbed at imaginary cation sites, where metal cations in next layer should be located. These results have indicated that Ni atoms selectively interact with oxygen dangling bonds.
We developed a micron-sized reaction chamber array of a few femtoliters that enables us to detect biological reactions at a single molecule level. By encapsulating a single molecules of β-galactosidase in chambers, a fluoregenic enzyme assay at a single enzyme was successively performed. The chamber array was also utilized to determine the mechanochemical coupling efficiency of F1-ATPase, a rotary motor protein. These experiments demonstrate the feasibility of this small reaction chamber array for highly sensitive detection of biological reactions.