New Approach To Understanding the Experimental 133Cs NMR Chemical Shift of Clay Minerals via Machine Learning and DFT-GIPAW Calculations.

Structural determination of adsorbed atoms on layered structures such as clay minerals is a complex subject. Radioactive cesium (Cs) is an important element for environmental conservation, so it is vital to understand its adsorption structure on clay. The nuclear magnetic resonance (NMR) parameters of 133Cs, which can be determined from solid-state NMR experiments, are sensitive to the local neighboring structures of adsorbed Cs. However, determining the Cs positions from NMR data alone is difficult. This paper describes an approach for identifying the expected atomic positions on clay minerals by combining machine learning (ML) with experimentally observed chemical shifts. A linear ridge regression model for ML is constructed from the smooth overlap of atomic position descriptor and gauge-including projector augmented wave (GIPAW) ab initio data. The constructed ML model predicts the GIPAW data to within a 3 ppm root-mean-squared error. At this stage, the 133Cs chemical shifts can be instantaneously calculated from the Cs positions on any clay layers using ML. The inverse analysis, which derives the atomic positions from experimentally observed chemical shifts, is developed from the ML model. The input data for the inverse analysis are the layer structure and the experimentally observed chemical shifts. The Cs positions for the targeted chemical shifts are then output. Inverse analysis is applied to montmorillonite, and the resultant Cs positions are found to be consistent with previous results (Ohkubo, T.; et al. J. Phys. Chem. A 2018, 122, 9326-9337). The Cs positions on saponite clay are also clarified from experimentally observed chemical shifts and inverse analysis.

Solution and solid-state 33 S NMR studies of 33 S-labeled taurine.

Sulfur-33(33 S) stable-isotope labeled taurine, 2-aminoethanesulfonic acid, has been synthesized, and a series of solution and solid-state 33 S nuclear magnetic resonance (NMR) experiments at 14.1 and 18.8 T, respectively, have been carried out at room temperature. The single peak of a solution 33 S NMR spectrum in 0.1-mM [33 S]-taurine in D2 O can be observed with the signal-to-noise (S/N) ratio of 9 in 40,000 scans, which paves the way toward in vivo analysis of pharmacokinetics and metabolism of 33 S-labeled taurine. Undistorted magic-angle-spinning (MAS) and static 33 S NMR spectra of polycrystalline [33 S]-taurine are observed with sufficient S/N ratios for analysis, and the magnitudes of 33 S EFG and CS tensors can be obtained.

Disposable Nitric Oxide Generator Based on a Structurally Deformed Nitrite-Type Layered Double Hydroxide.

The inhalation of nitric oxide (NO), which acts as a selective vasodilator of pulmonary blood vessels, is an established medical treatment. However, its wide adoption has been limited by the lack of a convenient delivery technique of this unstable gas. Here we report that a solid mixture of FeIISO4·7H2O and a layered double hydroxide (LDH) containing nitrite (NO2-) in the interlayer spaces (NLDH) stably generates NO at a therapeutic level (∼40 ppm over 12 h from freshly mixed solids; ∼80 ppm for 5-10 h from premixed solids) under air flow (0.25 L min-1) if the NLDH has been prepared by using a reconstruction method. Mg/Al-type LDH was calcined at 550 °C to remove interlayer CO32- and then treated with NaNO2 in water to reconstruct the NLDH. This one-pot, organic solvent-free process can be performed at large scales and is suitable for mass production. Humid air promotes anion exchange between NO2- and SO42- in the solid mixture, resulting in persistent interactions of NO2- and Fe2+, generating NO. In contrast to the previously reported NLDH prepared using an anion-exchange method, the reconstructed NLDH exhibits stable and persistent generation of NO because of partial deformation of the layered structures (e.g., particle aggregation, reduced crystallinity, and enhanced basicity). Degradation of the solid mixture is suppressed under dry conditions, so that a portable cartridge column that is readily available as an NO source for emergency situations can be prepared. This work demonstrates that the interlayer nanospace of LDH serves as a reaction mediator for excellent controllability of solid-state reactions. This inexpensive and disposable NO generator will facilitate NO inhalation therapy in developing countries and nonhospital locations.

Field-stepwise-swept QCPMG solid-state 115In NMR of indium oxide.

Experimental and theoretical investigations of indium-115 electric-field-gradient (EFG) tensors of indium(III) oxide, In2O3, have been presented. Field-stepwise-swept QCPMG solid-state 115In NMR experiments are carried out at T â€‹= â€‹120 â€‹K, observed at 52.695 â€‹MHz, and in the range of external magnetic fields between 4.0 and 6.5 â€‹T. The spectral simulations yield the quadrupolar coupling constant, CQ value, of 183(2) MHz and the asymmetry parameter, ηQ, of 0.05(5), for In(1), and that of 126(2) MHz and ηQ of 0.86(5) for In(2). Quantum chemical calculations are carried out to provide 115In EFG tensor orientations with respect to the molecular structure. A relationship between operative frequencies and variable ranges of external magnetic fields is briefly discussed for field-swept solid-state 115In NMR.

Why Do Carbonate Anions Have Extremely High Stability in the Interlayer Space of Layered Double Hydroxides? Case Study of Layered Double Hydroxide Consisting of Mg and Al (Mg/Al = 2).

Layered double hydroxides (LDHs) are promising compounds in a wide range of fields. However, exchange of CO32- anions with other anions is necessary, because the CO32- anions are strongly affixed in the LDH interlayer space. To elucidate the reason for the extremely high stability of CO32- anions intercalated in LDHs, we investigated in detail the chemical states of CO32- anions and hydrated water molecules in the LDH interlayer space by synchrotron radiation X-ray diffraction, solid-state NMR spectroscopy, and Raman spectroscopy. We found the rigidity of the network structure formed between the CO32- anions, hydrated water molecules, and the hydroxyl groups on the metal hydroxide layer surface to be a crucial factor underlying the stability of CO32- anions in the LDH interlayer space.

New Insights into the Cs Adsorption on Montmorillonite Clay from 133Cs Solid-State NMR and Density Functional Theory Calculations.

The adsorption sites of Cs on montmorillonite clays were investigated by theoretical 133Cs chemical shift calculations, 133Cs magic-angle-spinning nuclear magnetic resonance (MAS NMR) spectroscopy, and X-ray diffraction under controlled relative humidity. The theoretical calculations were carried out for structures with three stacking variations in the clay layers, where hexagonal cavities formed with Si-O bonds in the tetrahedral layers were aligned as monoclinic, parallel, alternated; with various d-spacings. After structural optimization, all Cs atoms were positioned around the center of hexagonal cavities in the upper or lower tetrahedral sheets. The calculated 133Cs chemical shifts were highly sensitive to the tetrahedral Al (AlT)-Cs distance and d-spacing, rather than to the Cs coordination number. Accordingly, three peaks observed in our theoretical spectra were interpreted to be adsorbed Cs around the center of hexagonal cavity with or without AlT and on the surface in the open nanospace. In a series of 133Cs MAS NMR spectral changes for partial Cs substituted samples, the Cs atoms are preferentially adsorbed at sites near AlT for low Cs substituted montmorillonites. The presence of nonhydrated Cs was also confirmed in partially Cs substituted samples, even after being hydrated under high relative humidity.

Investigation of the effects of sintering and indium-doping of zinc oxide using 67Zn magic angle spinning NMR analysis.

Indium-doped zinc oxide, a potential alternative material to indium tin oxide, was analyzed in powder form via 67Zn magic angle spinning nuclear magnetic resonance (MAS NMR). The 67Zn MAS NMR results show that the line shapes of zinc oxide were broadened by sintering, which was also observed for indium-doped zinc oxide, in which the broadening also depended on the sintering time. Furthermore, the line shapes of indium-doped zinc oxide were significantly broader than those of the corresponding zinc oxide, and were independent of the degree of indium doping. This indicates that indium atoms are associated into cluster-like structures in this compound.

Rare-Earth-Metal-Free Solid-State Fluorescent Carbonized-Polymer Microspheres for Unclonable Anti-Counterfeit Whispering-Gallery Emissions from Red to Near-Infrared Wavelengths.

Colloidal carbon dots (CDs) have garnered much attention as metal-free photoluminescent nanomaterials, yet creation of solid-state fluorescent (SSF) materials emitting in the deep red (DR) to near-infrared (NIR) range poses a significant challenge with practical implications. To address this challenge and to engineer photonic functionalities, a micro-resonator architecture is developed using carbonized polymer microspheres (CPMs), evolved from conventional colloidal nanodots. Gram-scale production of CPMs utilizes controlled microscopic phase separation facilitated by natural peptide cross-linking during hydrothermal processing. The resulting microstructure effectively suppresses aggregation-induced quenching (AIQ), enabling strong solid-state light emission. Both experimental and theoretical analysis support a role for extended π-conjugated polycyclic aromatic hydrocarbons (PAHs) trapped within these microstructures, which exhibit a progressive red shift in light absorption/emission toward the NIR range. Moreover, the highly spherical shape of CPMs endows them with innate photonic functionalities in combination with their intrinsic CD-based attributes. Harnessing their excitation wavelength-dependent photoluminescent (PL) property, a single CPM exhibits whispering-gallery modes (WGMs) that are emission-tunable from the DR to the NIR. This type of newly developed microresonator can serve as, for example, unclonable anti-counterfeiting labels. This innovative cross-cutting approach, combining photonics and chemistry, offers robust, bottom-up, built-in photonic functionality with diverse NIR applications.

Bioinspired Carbonized Polymer Microspheres for Full-Color Whispering Gallery Mode Emission for White Light Emission, Unclonable Anticounterfeiting, and Chemical Sensing Applications.

Light-element-based fluorescent materials, colloidal graphene quantum dots, and carbon dots (CDs) have sparked an immense amount of scientific interest in the past decade. However, a significant challenge in practical applications has emerged concerning the development of solid-state fluorescence (SSF) materials. This study addresses this knowledge gap by exploring the unexplored photonic facets of C-based solid-state microphotonic emitters. The proposed synthesis approach focuses on carbonized polymer microspheres (CPMs) instead of conventional nanodots. These microspheres exhibit remarkable SSF spanning the entire visible spectrum from blue to red. The highly spherical shape of CPMs imparts built-in photonic properties in addition to its intrinsic CD-based attributes. Leveraging their excitation-dependent photoluminescence property, these microspheres exhibit amplified spontaneous emission, assisted by the whispering gallery mode resonance across the visible spectral region. Remarkably, unlike conventional semiconductor quantum dots or dye-doped microresonators, this single microstructure showcases adaptable resonant emission without structural/chemical modifications. This distinctive attribute enables a plethora of applications, including microcavity-assisted energy transfer for white light emission, highly sensitive chemical sensing, and secure encrypted anticounterfeiting measures. This interdisciplinary approach, integrating photonics and chemistry, provides a robust solution for light-element-based SSF with inherent photonic functionality and wide-ranging applications.

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.

Synthesis of polyaniline with low polydispersity by using a supramolecular ionic assembly as the reaction medium.

A supramolecular ionic assembly comprised of an anionic oligo(phenylene ethynylene) and anilinium cations provides a unique reaction medium in which anilinum cations are concentrated and aligned. The oxidative polymerization (see figure) of aniline using the supramolecular ionic assembly (gray) yielded polyaniline (green/blue) with a number-average molar mass of 20,500 and polydispersity of 1.3.

Highly swellable hydrogel of regioselectively aminated (1→3)-α-d-glucan crosslinked with ethylene glycol diglycidyl ether.

(1→3)-α-d-glucan synthesized by glucosyltransferase J (GtfJ) cloned from Streptococcus salivarius was regioselectively aminated as 6-amino-6-deoxy-(1→3)-α-d-glucan (aminoglucan) through three steps: bromination, azidation, and reduction. The degree of substitution of the amino group was determined by elemental analysis to be 0.97 and the molecular weight was 3.74×104 as measured by size exclusion chromatography. The regioselective amination at the C6 position of every pyranose ring was confirmed by 1H/13C NMR and solid state 15N cross polarization/magic angle spinning NMR spectroscopy. Aminoglucan was characterized by FT-IR, X-ray diffraction and thermogravimetric analysis. Solubility of aminoglucan in various solvents was investigated and confirmed in aqueous solution at pH ≤ 11. Therefore, aminoglucan was crosslinked with ethylene glycol diglycidyl ether (EGDE) by an epoxy-ring opening reaction under alkaline conditions. The obtained EGDE-crosslinked aminoglucan hydrogels were highly swellable in water owing to a strong water-holding ability and no water was released on compression and breaking of the gels.

N-(Fluoren-9-ylmethoxy-carbon-yl)-l-isoleucine.

In the crystal structure of the title compound [systematic name fluoren-9-ylmethyl N-(1-carb-oxy-2-methyl-butyl)carbamate], C(21)H(23)NO(4), the mol-ecular plane of the O=C-NH-C(α) unit is slightly pyramidalized. The N atom deviates from the basal plane by 0.2086 (12) Å. The O=C-N-C(α) torsion angle is -17.2 (2)°, and the C-N and O=C bond lengths are 1.3675 (17) and 1.2122 (17) Å, respectively. Apparently the character of the sp(2) hybrids of the mol-ecular plane is, to some extent, reduced. The crystal structure exhibits two inter-molecular hydrogen bonds (O-H⋯O and N-H⋯O), in which the hydr-oxy O atom acts as a donor to the carbonyl group and an acceptor of the amide group, respectively.

Reduction Mechanisms of Cu2+-Doped Na2O-Al2O3-SiO2 Glasses during Heating in H2 Gas.

Controlling valence state of metal ions that are doped in materials has been widely applied for turning optical properties. Even though hydrogen has been proven effective to reduce metal ions because of its strong reducing capability, few comprehensive studies focus on practical applications because of the low diffusion rate of hydrogen in solids and the limited reaction near sample surfaces. Here, we investigated the reactions of hydrogen with Cu2+-doped Na2O-Al2O3-SiO2 glass and found that a completely different reduction from results reported so far occurs, which is dominated by the Al/Na concentration ratio. For Al/Na < 1, Cu2+ ions were reduced via hydrogen to metallic Cu, distributing in glass body. For Al/Na > 1, on the other hand, the reduction of Cu2+ ions occurred simultaneously with the formation of OH bonds, whereas the reduced Cu metal moved outward and formed a metallic film on glass surface. The NMR and Fourier transform infrared results indicated that the Cu2+ ions were surrounded by Al3+ ions that formed AlO4, distorted AlO4, and AlO5 units. The diffused H2 gas reacted with the Al-O-···Cu+ units, forming Al-OH and metallic Cu, the latter of which moved freely toward glass surface and in return enhanced H2 diffusion.

Ce-Doped La3Si6.5Al1.5N9.5O5.5, a Rare Highly Efficient Blue-Emitting Phosphor at Short Wavelength toward High Color Rendering White LED Application.

Phase pure nondoped and Ce doped La3Si6.5Al1.5N9.5O5.5 (Al containing La N-phase) samples have been obtained by solid-state reaction synthesis for the first time. 1% Ce-doped La3Si6.5Al1.5N9.5O5.5 phosphor displays a broad excitation band ranging from UV to 410 nm, with a maximum at 355 nm. UV light excitation results in a narrow Ce3+ 5d-4f emission band (fwhm = 68 nm) centered at 418 nm. The emission can be tuned from 417 nm at 0.5% Ce to 450 nm at 50% Ce. A high internal quantum efficiency up to 84% is achieved for a 1% Ce doped sample, which has CIE chromaticity coordinates of x = 0.157 and y = 0.069, close to the NTSC blue standard (x = 0.155; y = 0.070). Compared to La3Si8O4N11:Ce phosphor, the quantum efficiency and thermal stability have been enhanced for La3Si6.5Al1.5N9.5O5.5:Ce phosphor without shifting the emission peak wavelength. La3Si6.5Al1.5N9.5O5.5:Ce shows less thermal quenching than La3Si8O4N11:Ce and no shift or change in the shape of emission spectra with increasing the temperature from 4 to 573 K. These results show that La3Si6.5Al1.5N9.5O5.5:Ce is more efficient than any other (oxy-)nitride phosphor with an emission in the short wavelength blue region (400-450 nm). A white LED was fabricated using the La3Si6.5Al1.5N9.5O5.5:5%Ce as a blue phosphor. The high color rendering index (Ra = 93.2, R9 = 91.4, and R12 = 89.5) obtained shows that the phosphor is a very promising conversion phosphor for white LEDs.

24 T High-Resolution and -Sensitivity Solid-State NMR Measurements of Low-Gamma Half-Integer Quadrupolar Nuclei 35Cl and 37Cl.

Solid-state NMR observations of low-gamma half-integer quadrupolar nuclei, 35Cl and 37Cl, were demonstrated using a 24 T hybrid magnet (1H resonance frequency of 1.02 GHz) comprised of the high-temperature (HTS) and low-temperature (LTS) superconductors, and compared with results using a 14.1 T standard NMR magnet. While at 24 T the linewidth is 1.7 times narrower than that at 14.1 T, the gain in the sensitivity is 7.0 times because of enhanced polarization, reduced linewidth, and the use of larger rotor. A simple theoretical model was used to rationalize the sensitivity enhancements. The ratio of 35Cl and 37Cl quadrupolar couplings agrees well with the ratio of quadrupolar moments, and no isotope-dependent chemical shift has been observed. In addition, the 3QMAS spectrum of 35Cl is shown to demonstrate the high sensitivity rendered by the 24 T spectrometer.

Single-crystal NMR approach for determining chemical shift tensors from powder samples via magnetically oriented microcrystal arrays.

The single-crystal rotation technique was applied to magnetically oriented microcrystal arrays (MOMAs) of cellobiose (monoclinic) to determine the principal values and principal axes of the chemical shift tensors of C1 and C1' carbons. Rotations were performed about the magnetic χ1, χ2, and χ3 axes of MOMA, and the measurements were taken at six different orientations with respect to the applied magnetic field. Under these rotations, crowded peaks were reduced and the peaks for the C1 and C1' carbons were identified by comparing with simulation results. Six components of the chemical shift tensor expressed with respect to the magnetic χ1χ2χ3-frame were determined. The tensors thus obtained were transformed into those relative to the molecular frame.

Synthesis of a large-sized mesoporous phosphosilicate thin film through evaporation-induced polymeric micelle assembly.

A triblock copolymer, poly(styrene-b-2-vinyl pyridine-b-ethylene oxide) (PS-b-P2VP-b-PEO) was used as a soft template to synthesize large-sized mesoporous phosphosilicate thin films. The kinetically frozen PS core stabilizes the micelles. The strong interaction of the inorganic precursors with the P2VP shell enables the fabrication of highly robust walls of phosphosilicate and the PEO helps orderly packing of the micelles during solvent evaporation. The molar ratio of phosphoric acid and tetraethyl orthosilicate is crucial to achieve the final mesostructure. The insertion of phosphorus species into the siloxane network is studied by (29) Si and (31) P MAS NMR spectra. The mesoporous phosphosilicate films exhibit steady cell adhesion properties and show great promise as excellent materials in bone-growth engineering applications.

Manipulation of shell morphology of silicate spheres from structural evolution in a purely inorganic system.

We have investigated the structural transformation of solid silica spheres into various more complex spherical structures including flower-like, thick or thin nanosheet-shelled and porous shelled spheres. In the absence of organic additives, sodium salts contained in this inorganic reaction system apparently direct the silica dissolution and regrowth of dissolved silicate at the nanometer-scale, leading to the formation of a nanosheet network rather than solid aggregates. Subsequent removal of the salts by simple water washing results in voids in the siloxane network and a significant availability of surface silanol groups so that the resulting nanosheets and spheres composed of them possess large surface areas, pore volumes, and morphological flexibility, which can be varied by an applied stimulus. The results represent a rare example of the transformation of a simple silicate structure into a much more complex spherical structure involving a purely inorganic reaction system.

Achievement of 1020MHz NMR.

We have successfully developed a 1020MHz (24.0T) NMR magnet, establishing the world's 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.