Masataka Tansho

Lithium ion conduction in LiTi2(PO4)3

Abstract Li + ion conduction was examined for a mixture of LiTi 2 (PO 4 ) 3 (LTP) and a glassy electrolyte, 0.01Li 3 PO 4 –0.63Li 2 S–0.36SiS 2 . The addition of LTP with 10 wt.% resulted in a significant decrease in activation energy for conduction and little influence on the Li + ion conductivity, although it reduced the conduction path in the glass. The 7 Li NMR spectra of LTP was quite similar to that of Li 1.3 Al 0.3 Ti 1.7 (PO 4 ) 3 (LATP) with a high conductivity of 10 −3 S cm −1 . These results suggest that Li + ion conduction in LTP is as high as that in the glassy electrolyte and LATP.

Molecular Dynamics of Regioregular Poly(3-hexylthiophene) Investigated by NMR Relaxation and an Interpretation of Temperature Dependent Optical Absorption

The molecular structure and dynamics of regioregulated poly(3-hexylthiophene) (P3HT) were investigated using high-resolution solid-state (13)C nuclear magnetic resonance (NMR) and optical absorption spectroscopies. A crystal (C)-plastic crystal (PC) transition induced by the molecular motion of the aliphatic side group was observed for P3HT in the temperature dependence analysis of (13)C NMR spectra and spin-lattice relaxation time (T(1C)). The aliphatic side group motion in the crystalline state weakened intermolecular pi-pi interaction, resulting in the blue shift of the characteristic absorption of the interchain exciton. Above the transition temperature, the thiophene twisting motion induces not only further collapsing of the intermolecular interaction but also localizing of the intrachain exciton, leading to the blue shift of the absorption of both the inter- and intrachain exciton.

Conformational and microstructural characteristics of poly(L-lactide) during glass transition and physical aging.

The glass transition and physical aging processes of poly(L-lactide) (PLLA) were studied by variable-temperature Fourier transform infrared (FTIR) spectroscopy and (13)C solid-state NMR spectroscopy. The glass transition temperature (T(g)) of PLLA can be well determined from the temperature-dependent FTIR intensity. Nearby T(g), a distinct change in the slope of spectral intensity versus temperature plot is detected. FTIR results suggest that the energy-favorable gauche-trans (gt) conformers rearrange into the less energy-favorable gauche-gauche (gg) counterparts with heating over the glass transition region, which becomes more distinct at temperature above T(g). Besides, the 1267 cm(-1) band, which shows different trends of variation from the other bands upon heating, was assigned to be more sensitive to the nu(as)(C-O-C)+delta(CH) vibration mode of the less energy-favorable gg conformers in PLLA. By comparing the FTIR spectra of the aged and deaged PLLA, it was demonstrated that the rearrangement from the high- to low-energy conformers, i.e., gg to gt, occurs with physical aging. (13)C spin-lattice relaxation measurements indicate that the relaxation rate distribution broadens with aging, which agrees with the previous suggestion that the locally ordered domains are formed during physical aging. Because of the larger variation in the conformational state and microstructure, the FTIR intensities vary much more abruptly for the aged sample with heating to nearby T(g).

Naked-eye discrimination of methanol from ethanol using composite film of oxoporphyrinogen and layered double hydroxide.

Methanol is a highly toxic substance, but it is unfortunately very difficult to differentiate from other alcohols (especially ethanol) without performing chemical analyses. Here we report that a composite film prepared from oxoporphyrinogen (OxP) and a layered double hydroxide (LDH) undergoes a visible color change (from magenta to purple) when exposed to methanol, a change that does not occur upon exposure to ethanol. Interestingly, methanol-induced color variation of the OxP-LDH composite film is retained even after removal of methanol under reduced pressure, a condition that does not occur in the case of conventional solvatochromic dyes. The original state of the OxP-LDH composite film could be recovered by rinsing it with tetrahydrofuran (THF), enabling repeated usage of the composite film. The mechanism of color variation, based on solid-state (13)C-CP/MAS NMR and solution-state (13)C NMR studies, is proposed to be anion transfer from LDH to OxP triggered by methanol exposure.

Dynamic Breathing of CO2 by Hydrotalcite

The carbon cycle of carbonate solids (e.g., limestone) involves weathering and metamorphic events, which usually occur over millions of years. Here we show that carbonate anion intercalated layered double hydroxide (LDH), a class of hydrotalcite, undergoes an ultrarapid carbon cycle with uptake of atmospheric CO2 under ambient conditions. The use of (13)C-labeling enabled monitoring by IR spectroscopy of the dynamic exchange between initially intercalated (13)C-labeled carbonate anions and carbonate anions derived from atmospheric CO2. Exchange is promoted by conditions of low humidity with a half-life of exchange of ~24 h. Since hydrotalcite-like clay minerals exist in Nature, our finding implies that the global carbon cycle involving exchange between lithosphere and atmosphere is much more dynamic than previously thought.

Cubic Si6−zAlzOzN8−z (z=1.8 and 2.8) spinels formed by shock compression

Abstract We present the formation of cubic Si6−zAlzOzN8−z (z=1.8 and 2.8) spinels by shock compressions from the corresponding β-sialon. Formed sialon spinels coexist with considerable amounts of the amorphous phase. The amorphization is considered to be a solid–solid reaction due to the sluggish phase transition under shock compression. The lattice parameter of the spinel increases and the density decreases with increasing z parameter. Shock-synthesized sialon spinels are nanocrystals with most grain sizes less than 30 nm and consist of main units of SiN4, SiN6 and AlO6.

Rapid Exchange between Atmospheric CO2 and Carbonate Anion Intercalated within Magnesium Rich Layered Double Hydroxide

The carbon cycle, by which carbon atoms circulate between atmosphere, oceans, lithosphere, and the biosphere of Earth, is a current hot research topic. The carbon cycle occurring in the lithosphere (e.g., sedimentary carbonates) is based on weathering and metamorphic events so that its processes are considered to occur on the geological time scale (i.e., over millions of years). In contrast, we have recently reported that carbonate anions intercalated within a hydrotalcite (Mg0.75Al0.25(OH)2(CO3)0.125·yH2O), a class of a layered double hydroxide (LDH), are dynamically exchanging on time scale of hours with atmospheric CO2 under ambient conditions. (Ishihara et al., J. Am. Chem. Soc. 2013, 135, 18040-18043). The use of (13)C-labeling enabled monitoring by infrared spectroscopy of the dynamic exchange between the initially intercalated (13)C-labeled carbonate anions and carbonate anions derived from atmospheric CO2. In this article, we report the significant influence of Mg/Al ratio of LDH on the carbonate anion exchange dynamics. Of three LDHs of various Mg/Al ratios of 2, 3, or 4, magnesium-rich LDH (i.e., Mg/Al ratio = 4) underwent extremely rapid exchange of carbonate anions, and most of the initially intercalated carbonate anions were replaced with carbonate anions derived from atmospheric CO2 within 30 min. Detailed investigations by using infrared spectroscopy, scanning electron microscopy, powder X-ray diffraction, elemental analysis, adsorption, thermogravimetric analysis, and solid-state NMR revealed that magnesium rich LDH has chemical and structural features that promote the exchange of carbonate anions. Our results indicate that the unique interactions between LDH and CO2 can be optimized simply by varying the chemical composition of LDH, implying that LDH is a promising material for CO2 storage and/or separation.

Intra- and Intermolecular Effects on 1H Chemical Shifts in a Silk Model Peptide Determined by High-Field Solid State 1H NMR and Empirical Calculations

A combination of solid state 1H NMR chemical shift measurements and empirical chemical shift calculations has been used to interpret 1H solid state chemical shifts of a model peptide (Ala-Gly)15 for the crystalline domain of Bombyx mori silk fibroin in silk I and silk II structures, including a treatment of both intra- and intermolecular arrangements. Silk I and silk II are the structures of silk fibroin before and after spinning, respectively. Two peaks with equal intensity were observed for the amide protons of (AG)15 in silk I, whereas only one broad peak was observed for silk II, reflecting a difference of 1.1 ppm in Ala HN shift between silk I and silk II, but a difference of only 0.2 ppm in Gly HN shift. Chemical shift calculations predicted chemical shifts that are in good agreement with the experimental observations and showed that the origin of these chemical shift differences was predominantly the magnetic anisotropy effect from the C=O bond that hydrogen bonds with HN, which has a more favorable geometry for Ala HN in silk II than for the other HN. This result shows that we could distinguish between proton chemical shift effects arising from intermolecular interactions and those from intramolecular interactions by combining observation of the solid state 1H NMR chemical shift and empirical chemical shift calculation.

Preparation, crystal structure and silver ionic conductivity of the new compound Ag8TiS6

Abstract The new compound Ag 8 TiS 6 has been prepared by solid state reaction. The crystal structure, phase transition and transport properties have been studied using X-ray diffraction, Raman spectra, ionic conductivity measurement and the e.m.f method. The dc conductivities of silver ion of Ag 8 TiS 8 reach values around 10 −3 Ω −1 cm −1 at ambient temperatures. The transference numbers of silver ion are found to be close to unity.

Molecular dynamics of a polyaniline/β-cyclodextrin complex investigated by 13C solid-state NMR.

The molecular dynamics of a polyaniline/β-cyclodextrin inclusion complex (PANI/β-CD IC) and its relation with optical properties were investigated using high-resolution solid-state (13)C nuclear magnetic resonance (NMR) and optical absorption spectroscopies. UV-vis measurements revealed a π-π* absorption peak of a PANI film that had a 10 nm blue-shift by inclusion of β-CD, indicating that π-conjugation of PANI was shortened in the IC. Temperature dependent analysis of (13)C NMR spectra and spin-lattice relaxation times (T(1C)) revealed that the inclusion induced acceleration of the twisting motion of the PANI chain. Moreover, two twisting motions attributed to different torsional angle modes were observed following Arrhenius plots of T(1C) measurements, and the twisting frequency and angle increased above -25 °C. These results suggest that the β-CD inclusion weakens the intermolecular π-π interaction and enhances the accompanying twisting motion, consequently leading to a blue-shift of UV-vis absorption.