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The modification of a polyimide surface containing a 30% fraction of steroidal structure was studied as a function of storage time by vibrational sum frequency generation (SFG) spectroscopy and optical second-harmonic generation (SHG). The variation of the symmetric and anti-symmetric stretching modes of the CH3 isopropyl group at the end of the side chain of the rubbed polyimide was detected in the SFG spectra after a 3-month storage time in a practical environment. It suggests that the isopropyl group might be reoriented. On the other hand, the SHG response of the same sample showed an insignificant storage-time dependence. As a result, the phenyl rings of the polyimide are judged to be unmodified after long-term storage time. The change is suggested to occur for two main reasons. One is the interaction between the polyimide polymers and the ambient water molecules. The other is the adsorption of unknown organic molecules on the polyimide surface.

The molecular orientation of steroidal side chains at rubbed polyimide (PI) surfaces is studied by sum frequency generation (SFG) vibrational spectroscopy. The main objective is to find a correlation between the molecular structure of the PI film and the liquid crystal alignment on the polymer. Analysis of the SFG spectra shows that rubbing of the polymer film appears to cause conformational changes in the methyl group of the polymer side chain near the steroidal structure. However, rubbing does not significantly influence the orientation of the isopropyl group at the end of the polymer side chain. This shows that the liquid crystal alignment is not correlated with the orientation of the isopropyl group., identifier:https://dspace.jaist.ac.jp/dspace/handle/10119/18070

It is known that one of starch branching enzyme (BE) isoforms, BEIIb, plays a specific role not only in the synthesis of distinct amylopectin cluster structure, but also in the formation of the internal structure of starch granules in rice endosperm because in its absence the starch crystalline polymorph changes to the B-type from the typical A-type found in the wild-type (WT) cereal endosperm starch granules. In the present study, to examine the contribution of BEIIb to the amylopectin cluster structure, the chain-length distributions of amylopectin and its phosphorylase-limit dextrins (Φ-LD) from endosperm and culm of a null be2b mutant called amylose-extender (ae) mutant line, EM10, were compared with those of its WT cultivar, Kinmaze, of japonica rice. The results strongly suggest that BEIIb specifically formed new short chains whose branch points were localized in the basal part of the crystalline lamellae and presumably in the intermediate between the crystalline and amorphous lamellae of amylopectin clusters in the WT endosperm, whereas in its absence branch points which were mainly formed by BEI were only located in the amorphous lamellae of amylopectin. These differences in the cluster structure of amylopectin between Kinmaze and EM10 endosperm were considered to be responsible for the differences in the A-type and B-type crystalline structures of starch granules between Kinmaze and EM10, respectively. The changes in internal structure of starch granules caused by BEIIb were analyzed by wide angle X-ray diffraction, small-angle X-ray scattering, solid state ^<13>C NMR, and optical sum frequency generation spectroscopy. It was noted that the size the amylopectin cluster in ae endosperm (approximately 8.24 nm) was significantly smaller than that in WT endosperm (approximately 8.81 nm). Based on the present results, we proposed a model for the cluster structure of amylopectin in WT and ae mutant of rice endosperm. We also hypothesized the role of BEIIa in amyl

Contribution of main chains and side chains of unrubbed polyimide films with steroidal structure side chains to second harmonic generation (SHG) response was studied by varying their molar fraction of side-chain diamine. The SHG intensity in P_/P_ polarization (P-polarization input and P-polarization output) configuration does not depend strongly on the molar fraction. This indicates that both the main chains and side chains at the surface contribute similarly to the SHG intensity. The SHG intensity in S_/P_ polarization configuration normalized by that of P_/P_ polarization configuration was the smallest for the molar fraction of side-chain diamine of 0%. This fact indicates that the microscopic nonlinear dipoles are standing nearly upright at the surface of the film consisting only of the main chains, while their orientational spread is wider when the side chains are involved., identifier:https://dspace.jaist.ac.jp/dspace/handle/10119/16247

We used sum frequency generation (SFG) spectroscopy to study the desorption of hydrogen on the stepped Si(111) surface with a miscut angle of 9.5° toward the [112] direction in ultra-high vacuum. The terrace peak was observed at 2085 cm^<−1> and the vertical step mode of dihydride was observed at 2098 cm^<−1> for the ssp-polarization (s-polarized SFG, s-polarized visible, and p-polarized infrared light) combination. The intensity reduction of these two peaks was monitored directly as a function of time at sample temperatures of 593 K. The rate of reduction was faster for the step dihydride peak than for the terrace monohydride peak.

To clarify the mechanism by which the optical properties of Sb_2Te_3 change because of its solid-liquid phase transition, we carried out ab initio calculations of the electronic and optical properties of Sb_2Te_3 in both the crystalline and liquid states. The calculated results indicate that the density of states around the Fermi level increases because of melting and that the energy bandgap observed in the crystalline state consequently disappears. The imaginary part of optical dielectric functions of crystalline Sb_2Te_3 has a large peak at a photon energy of ħω = 1.5 eV. When Sb_2Te_3 melts, it exhibits somewhat metallic optical properties and its optical absorption at ħω = 3.06 eV, which is used in Blu-ray Disc systems, decreases. This decrease in optical absorption is proposed to result from a large reduction of the optical transition strength at ħω ≈ 1.5 eV.

Here I review a recent work in our group on Pd nanowire fabrication on MgO(210) facetted templates by shadow deposition. The facetted template was prepared by homoepitaxial deposition of MgO of 150 nm thickness on MgO(210) substrate. Pd was deposited by electron bombardment with a glancing angle of 25 deg on the wider (100) terrace of the template. Moiré patterns of transmission electron microscopy (TEM) images of the samples show that the nanowires are highly crystalline on MgO(210) facetted template. Such effect was not observed on MgO(110) facetted template. I discuss the mechanism of the formation of the well-crystalline structure in the Pd nanowires. One candidate origin is nucleation of the Pd atoms at the step-like defects running perpendicular to the facet edges of the MgO template.