Y. Mita

Highly controlled acetylene accommodation in a metal-organic microporous material.

Metal–organic microporous materials (MOMs) have attracted wide scientific attention owing to their unusual structure and properties, as well as commercial interest due to their potential applications in storage, separation and heterogeneous catalysis. One of the advantages of MOMs compared to other microporous materials, such as activated carbons, is their ability to exhibit a variety of pore surface properties such as hydrophilicity and chirality, as a result of the controlled incorporation of organic functional groups into the pore walls. This capability means that the pore surfaces of MOMs could be designed to adsorb specific molecules; but few design strategies for the adsorption of small molecules have been established so far. Here we report high levels of selective sorption of acetylene molecules as compared to a very similar molecule, carbon dioxide, onto the functionalized surface of a MOM. The acetylene molecules are held at a periodic distance from one another by hydrogen bonding between two non-coordinated oxygen atoms in the nanoscale pore wall of the MOM and the two hydrogen atoms of the acetylene molecule. This permits the stable storage of acetylene at a density 200 times the safe compression limit of free acetylene at room temperature.

Selective sorption of oxygen and nitric oxide by an electron-donating flexible porous coordination polymer

Porous coordination polymers are materials formed from metal ions that are bridged together by organic linkers and that can combine two seemingly contradictory properties—crystallinity and flexibility. Porous coordination polymers can therefore create highly regular yet dynamic nanoporous domains that are particularly promising for sorption applications. Here, we describe the effective selective sorption of dioxygen and nitric oxide by a structurally and electronically dynamic porous coordination polymer built from zinc centres and tetracyanoquinodimethane (TCNQ) as a linker. In contrast to a variety of other gas molecules (C2H2, Ar, CO2, N2 and CO), O2 and NO are accommodated in its pores. This unprecedented preference arises from the concerted effect of the charge-transfer interaction between TCNQ and these guests, and the switchable gate opening and closing of the pores of the framework. This system provides further insight into the efficient recognition of small gas molecules. Porous coordination polymers can form materials that are both crystalline and flexible, creating regular yet dynamic channels that are promising for guest sorption. Guest selectivity is difficult to achieve, however, and typically relies on size- or shape-recognition. A framework has now been assembled that combines charge-transfer interactions and structural flexibility to only accommodate O2 and NO.

Optical Study of MnO under High Pressure

Raman and optical absorption studies of the antiferromagnetic insulator MnO were performed at several temperatures under high pressure. In Raman scattering at 2 K, it was observed that the two-magnon peak shifts to higher energy with increasing pressure and then disappears at around 20 GPa. This suggests that a change in spin arrangement occurs at that pressure. At 77 K the peak-vanishing pressure increases to 25 GPa. At room temperature, a jump of the Raman peak position was observed at 30 GPa and the peak vanishes at 89 GPa. These results are consistent with previous X-ray diffraction studies which showed phase transitions at 30 and 90 GPa. The vanishing of the Raman peak suggests a metallization transition. The pressure dependence of the Mn2+ d–d transition observed in optical absorptions was consistent with the crystal field theory up to around 25 GPa at room temperature.

Pressure effects on first-order magnetic Raman scattering in NiO

The pressure dependence of first-order magnetic Raman peak of NiO single crystal was studied up to 20 GPa at room temperature. At ambient pressure, an unknown peak is also observed at nearly the same position as the one-magnon one and their separation becomes remarkable with increasing pressure. Pressure coefficients of the one-magnon peak and the other peak are obtained as 0.4 and 1.5 cm−1 GPa−1, respectively. The next-nearest-neighbour antiferromagnetic exchange constant J2 is obtained as a function of the lattice constant.

Temperature and pressure studies of Raman peaks related to hydrogen modes in KDP

Raman scattering spectra of a KH2PO4 (KDP) single crystal have been obtained under various temperature and pressure conditions. It was observed that (i) the peak around 1310 cm−1 is not a single peak as reported previously but consists of two components and (ii) in the ferroelectric phase the 1013, 1306 and 1315 cm−1 peaks become obscure near the ferroelectric–paraelectric phase boundary. Furthermore, they show positive pressure shifts and the pressure coefficients are obtained. An interpretation is proposed for the origins of these Raman peaks.

Hole-burning effect and photochromism of color centers in synthetic diamonds

Using highpressure synthetic diamonds of type Tb NV or 112 center is introduced dominantly by controlling the dose and the annealing temperature. Some optical properties are studied to explore a possibility for application to optoelectronics. For NV center the holeburning effect of the zerophonon line has been examined on the following aspects: the distribution for the magnitude of internal strain the burning and erasing processes of a hole and the temperature dependence of the hole width. For 112 it has been found that photochromism occurs by illumination of light shorter than 600nm wavelength. A tentative model is proposed on the basis of the experimental results. _i .

Magneto-optical studies of quaternary semimagnetic semiconductor alloys Hg1−x−yCdxMnyTe

The quaternary alloy single crystals of Hg1−x−yCdxMnyTe, which exhibit high purity and sufficient homogeneity, have been prepared by means of a modified zone melting method. The far-infrared interband, Γ8 → Γ8, and intraband magneto-absorptions have been studied in several specimens of the narrow gap region using optically pumped lasers. We assign these observed lines as the cyclotron resonance, the spin resonance, the combined resonance and some interband transitions.

Pressure Induced Destruction Of The Mott‐Hubbard Insulating State In Manganese Monochalcogenides With NaCl Structure

The infrared reflection measurements of NaCl type manganese monochalcogenides MnO and α‐MnS were performed under high pressure at room temperature. In both case, drastic increase in reflectivity was observed from 94 and 23 GPa and it becomes pressure‐insensitive around 127 and 29 GPa, respectively. These results strongly suggest that the metallic transitions occur around the pressure regions, which are consistent with the result of recent X‐ray studies.