Shinobu Ohki

Achievement of 1020 MHz NMR

We have successfully developed a 1020MHz (24.0T) NMR magnet, establishing the worlds highest magnetic field in high resolution NMR superconducting magnets. The magnet is a series connection of LTS (low-Tc superconductors NbTi and Nb3Sn) outer coils and an HTS (high-Tc superconductor, Bi-2223) innermost coil, being operated at superfluid liquid helium temperature such as around 1.8K and in a driven-mode by an external DC power supply. The drift of the magnetic field was initially ±0.8ppm/10h without the (2)H lock operation; it was then stabilized to be less than 1ppb/10h by using an NMR internal lock operation. The full-width at half maximum of a (1)H spectrum taken for 1% CHCl3 in acetone-d6 was as low as 0.7Hz (0.7ppb), which was sufficient for solution NMR. On the contrary, the temporal field stability under the external lock operation for solid-state NMR was 170ppb/10h, sufficient for NMR measurements for quadrupolar nuclei such as (17)O; a (17)O NMR measurement for labeled tri-peptide clearly demonstrated the effect of high magnetic field on solid-state NMR spectra.

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.

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.

1020 MHz single-channel proton fast magic angle spinning solid-state NMR spectroscopy

This study reports a first successful demonstration of a single channel proton 3D and 2D high-throughput ultrafast magic angle spinning (MAS) solid-state NMR techniques in an ultra-high magnetic field (1020MHz) NMR spectrometer comprised of HTS/LTS magnet. High spectral resolution is well demonstrated.

Optical pumping NMR in the compensated semiconductor InP:Fe

The optical pumping nuclear-magnetic-resonance effect in the compensated semiconductor InP:Fe has been investigated in terms of the dependences of photon energy E p , helicity σ ′ , and exposure time τ L of infrared lights.The 3 1 P and 1 5 In signal enhancements show large σ ′ asymmetries and anomalous oscillations as a function of E p . We find that (i) the oscillation period as a function of E p is similar for 3 1 P and 1 1 5 In and almost field independent in spite of significant reduction of the enhancement in higher fields. (ii) A characteristic time for buildup of the 3 1 P polarization under the light exposure shows strong E p dependence, but is almost independent of σ ′ . (iii) The buildup times for 3 1 P and 1 1 5 In are of the same order (10 3 s), although the spin-lattice relaxation times T 1 are different by more than three orders of magnitude between them. The results are discussed in terms of (1) discrete energy spectra due to donor-acceptor pairs in compensated semiconductors and (2) interplay between 3 1 P and dipolar ordered indium nuclei, which are optically induced.

High-Field NMR up to 30 T with a Hybrid Magnet

NMR measurements up to 30 T were performed with the hybrid magnet installed in the National Institute for Materials Science (NIMS). The field profile and stability of superconducting, resistive and their hybrid magnets were measured using 63Cu NMR of a Cu metal. The field homogeneity of the hybrid magnet at 30 T is 186±4 ppm in the region ±5 mm from the field center along the z-axis. The magnetic field fluctuates with a total amplitude of about 30 G at 30 T (100 ppm). The present status of the hybrid magnet for high-resolution solid-state NMR measurements is discussed.

Decoupling-free NMR quantum computer on a quantum spin chain

A method of switching a controlled-NOT gate in a solid-stae NMR quantum computer is presented. Qubits of I = 1/2 nuclear spins are placed periodically along a quantum spin chain (1-D antiferromagnet) having a singlet ground state with a finite spin gap to the lowest excited state caused by some quantum effect. Irradiation of a microwave tuned to the spin gap energy excites a packet of triplet magnons at a specific part of the chain where control and target qubits are involved. The packet switches on the Suhl-Nakamura interaction between the qubits, which serves as a controlled NOT gate. The qubit initialization is achieved by a qubit initializer consisting of semiconducting sheets attached to the spin chain, where spin polarizations created by the optical pumping method in the semiconductors are transferred to the spin chain. The scheme allows us to separate the initialization process from the computation, so that one can optimize the computation part without being restricted by the initialization scheme, which provides us with a wide selection of materials for a quantum computer.

Successful Upgrading of 920-MHz NMR Superconducting Magnet to 1020 MHz Using Bi-2223 Innermost Coil

We succeeded in upgrading the 920-MHz nuclear magnetic resonance (NMR) superconducting magnet (21.6 T) to 1020 MHz (24.0 T) by replacing the innermost Nb3Sn coil with a (Bi,Pb)2Sr2Ca2Cu3O10 (Bi-2223) coil. The 920-MHz NMR spectrometer had been installed in the National Institute for Materials Science, Tsukuba, Japan, in 2001. It has been operated in the persistent mode for six years. The upgrading project started in 2006. A Bi-2223 coil was developed as the innermost coil instead of the Nb3Sn one. The newly installed Bi-2223 innermost coil is connected to Nb3Sn and NbTi coils in series. The upgraded NMR magnet was seriously damaged by the Great East Japan Earthquake in March 2011. After more than two years of restoration and additional improvements of current leads and the power supply system, the magnet was cooled down to below 1.8 K in August 2014. The magnet successfully generated 24.0 T, corresponding to 1020 MHz, in October 2014. To achieve the required homogeneity and stability of the magnetic field, not only superconducting and room-temperature shim coils but also ferromagnetic shims were used. The 1020-MHz superconducting NMR magnet has been operated in a power-supply-driven mode for six months.

Competition of Thermodynamic and Dynamic Factors During Formation of Multicomponent Particles via Spray Drying

As psicose cannot be spray dried because of its low glass transition temperature (T(g)), additives have been used to manufacture spray-dried particles. Its thermodynamic miscibility with each additive was evaluated by thermal analysis and C solid-state nuclear magnetic resonance. Aspartame was miscible with psicose at all ratios, and spray-dried particles were obtained when T(g) of the mixture was higher than the outlet temperature of the spray dryer, where 30 wt % of psicose was loaded. poly(vinylpyrrolidone) and cluster dextrin were partially miscible with psicose, with a maximum loading of 40 wt %. When polymeric excipients were used, their mixing behavior with psicose was affected by the dynamic factor during the spray drying, that is, enhanced phase separation due to the molecular-weight difference. The T(g) value of the polymer-rich phases, which were likely to form shell layers on the surfaces, played an important role in determining availability of the spray-dried particles. Hydroxypropyl methylcellulose (HPMC) offered a very effective loading capacity of 80 wt %, due to distinct phase separation to form shell phase with a very high T(g). Because molecular weight of HPMC was the smallest among the polymeric excipients, the thermodynamic miscibility seemed to affect the dynamic phase separation. These results provide useful information for preparing multicomponent spray-dried particles.