Nanomaterials has recently been expected as one of promising materials for functional anti-microbial agent, owing to their high activity high stability and low-cost fabrication process. Here, we have clarified the mechanism of destructive interaction of polyoxometalate (POM) clusters with the model cell membrane, by using both liposomes and solid-supported lipid bilayers. Leakage experiment clarified that liposomes are broken by POM cluster above a critical threshold concentration. At these concentrations, a formation of network-like defect in the solid-supported bilayer was found by fluorescence microscope observations. From correlations between results of liposome and supported bilayers, it was concluded that the formation of network-like defects formed above threshold concentration is the origin of destructive activity of POM for the cell membranes.
Photoemission spectroscopy is one of the most reliable and versatile experimental techniques in the field of surface science. The recent improvement of the energy resolution enables us to observe the inelastic scattering process induced by the electron-phonon interaction during laser photoemission process. One example is the appearance of step structures in the laser photoemission spectra（LPES） in addition to the elastic component fitted by Fermi-Dirac distribution. In this article, we investigate the origin of this step structure in the Cu(110) spectra by using ab-initio density functional and density functional perturbation theory. We have found that the subsurface phonon modes scatter the excited electron from Y point to the Γ point around the vacuum level, which leads to this step structure. In addition to clean Cu(110), we also carried out similar analysis on the Cu(110)-(2×1)-O surface. Although the inelastic step structures appeared at the identical position within the experimental uncertainty in the Cu(110) and Cu(110)-(2×1)-O spectra, we found that the phonon modes that corresponds to the inelastic process are different in these two surfaces.
In order to understand relation between surface structure and catalytic activity, we studied the Ni2P (1010) surface using scanning tunneling microscopy (STM). Atomic scale STM images of c(2×4) structure and (1×1) structure were obtained after annealing the sample at 653 K (denoted as surface structure I). The area of c(2×4) structure was decreased by the NO exposure at 573 K. A c(2×4) structure together with c(2×2) structure was obtained after the repeated sputtering-annealing treatments and reactions, which was called as surface structure II. Contrary to the surface structure I, this surface didn't change its structure by the NO exposure at 573 K. Since the (1×1) structure on the surface structure I had exposed Nit (tetrahedral Ni) and Nisp (square pyramid Ni) pairs, NO might be activated and destroy the c(2×4) structure, while c(2×2) structure on the surface structure II had no exposed Nit and Nisp pair so that surface structure II was less reactive. The removal of the surface P atoms is important for the activation of the Ni2P surface.
Networked nanographite (NNG) was grown by using photoemission-assisted plasma enhanced chemical vapor deposition (CVD) on SiO2 (90 nm) /Si substrates and the career gas dependence of electric resistivity, chemical configuration, and grain size was investigated from Raman spectroscopy, SIMS, and four probes method. In this study, CH4/Ar and CH4/H2 gases were used. NNG with the thickness from 2∼60 nm was grown by changing the growth period. Resistivity of thin films showed clearly decreases in CH4/H2 in an order of magnitude nevertheless their grain sizes were almost same at the length of 9 nm. From SIMS measurement, hydrogen concentration of the sample grown by CH4/H2 was 3 times less than that of by CH4/Ar. From these results, it is found that hydrogen termination at grain boundary is the cause of low electric conductivity, and H radicals in CH4/H2 plasma may remove the terminated hydrogen by H abstraction reaction in CVD process.
The electronic band structure of Pt-induced nanowires on Ge(001) (Pt/Ge(001) NWs) has been studied with angle-resolved photoelectron spectroscopy. We have found two metallic bands with s-polarized light. One of the bands shows the straight Fermi lines, indicating that it is an ideal one-dimensional metallic state. On the other hand, a density of state of the band at Fermi level is not suppressed and the spectral shape agrees with a Fermi-Dirac-type distribution function even at 6 K, well below the temperature of the structural phase transition of Pt/Ge(001) NWs. We therefore conclude that the electron in the one-dimensional metallic band behaves not as a Luttinger liquid but as a one-dimensional Fermi gas.
The electronic structures of alkanethiolate self-assembled monolayers (SAMs) associated with their molecular-scale geometry have been evaluated by combining two types of scanning tunneling spectroscopy (STS): current-voltage (I/V) and distance-voltage (z/V) spectroscopy. In the STS spectra, in addition to electronic states originating from alkyl-chain and SAM/Au interface, an image potential state (IPS) formed in a vacuum gap is clearly observed. The result is well consistent with our two-photon photoemission spectroscopy (2PPES) measurements. Furthermore, by using time- and angle-resolved 2PPES, we found that the electron excited into IPS is highly separated from the Au substrate and has an extremely long lifetime of the order of 100 ps owing to the excellent insulating property of SAM. The lifetime can be prolonged by increasing the length of alkyl chain and by lowering the substrate temperature, which indicates that the degree of electron separation can be precisely controlled by designing the molecular layer.
In this paper, we will discuss our recent approaches for the formation of mechanically stable artificial bilayer lipid membranes (BLMs) by combining with silicon (Si) micro-fabrication techniques and their application to recording activities of biological channels. BLMs were prepared across microfabricated pores in thin Si3N4 septa of Si chips. The edge of the pores was smoothly tapered in nanometer range, which was useful for stabilizing the BLMs suspended in the pores. The BLMs showed a membrane lifetime of >40 h, tolerance to a high voltage of ±1 V, and tolerance to repetitive solution exchanges. Application to a platform for recording biological channels has been examined by using the human ether-a-go-go-related gene (hERG) potassium channel as an illustrative example. Such stable BLMs with integrated biological channels have the potential for use in a variety of applications, including high-throughput drug screening for various ion-channel proteins.
Lubrication and tribo-corrosion mechamisms of imidazolium based ionic liquid was explained. Regarding corrosion, molecular behavior of water which mixed with 1-buthyl-3-methylimidazolium trifluoromethanesulfonate ([BMIM] OTf) under corrosion process has been investigated by Fourier Transform Infrared Spectroscopy (FT-IR). It was found that there are two mixture state of water in [BMIM] OTf; one is called free water, the other is called liquid-like water. Liquid-like water associates with corrosion. Then, we will mention the previous research of solid—liquid interface structure of ionic liquid and its contribution on friction. Finally, we will mention our recent results of relation between interfacial structure of adsorbed molecules and friction investigated by sum-frequency generation (SFG) spectroscopy.
We review the recent progress of the study of silicene, which is a honeycomb structure of silicon atoms. Silicene shares many similar properties with graphene but has some extra exciting properties since it is a topological insulator due to its spin-orbit interactions. Silicene has so far been synthesized only on a substrate. The synthesis and the measuring physical properties of silicene are interesting playgrounds of the surface science.