Saccharide formation by sustainable formose reaction using heterogeneous zeolite catalysts.

The formose reaction is a unique chemical reaction for the preparation of saccharides from formaldehyde, a single carbon compound. We applied zeolite materials as heterogeneous catalysts to the formose reaction. The simple addition of Linde type A zeolite containing calcium ions (Ca-LTA) to an aqueous solution of formaldehyde and glycolaldehyde produced saccharides at room temperature. A quantitative analysis performed by high-performance liquid chromatography revealed that triose, tetrose, pentose, and hexose saccharides were produced with few byproducts. Ca-LTA was recovered from the reaction mixture by filtration, and the retrieved zeolite was found to be reusable under the same conditions. The catalytic activity of Ca-LTA was higher than those of conventional calcium catalysts and other solid materials such as silica, alumina, and hydroxyapatite. Several other types of zeolites with different crystal structures and alkali/alkali-earth metal ions also showed catalytic activity for saccharide formation. Based on the analytical results obtained by infrared spectroscopy, temperature-programmed desorption profiles and NMR measurements, we propose a reaction mechanism in which C-C bond formation is promoted by the mild basicity of the oxygen atoms and acidity on the metal ions of the aluminosilicate on the zeolite surfaces with low SiO2/Al2O3 ratios.

Construction of an autocatalytic reaction cycle in neutral medium for synthesis of life-sustaining sugars.

Autocatalytic mechanisms in carbon metabolism, such as the Calvin cycle, are responsible for the biological assimilation of CO2 to form organic compounds with complex structures, including sugars. Compounds that form C-C bonds with CO2 are regenerated in these autocatalytic reaction cycles, and the products are concurrently released. The formose reaction in basic aqueous solution has attracted attention as a nonbiological reaction involving an autocatalytic reaction cycle that non-enzymatically synthesizes sugars from the C1 compound formaldehyde. However, formaldehyde and sugars, which are the substrate and products of the formose reaction, respectively, are consumed in Cannizzaro reactions, particularly under basic aqueous conditions, which makes the formose reaction a fragile sugar-production system. Here, we constructed an autocatalytic reaction cycle for sugar synthesis under neutral conditions. We focused on the weak Brønsted basicity of oxometalate anions such as tungstates and molybdates as catalysts, thereby enabling the aldol reaction, retro-aldol reaction, and aldose-ketose transformation, which collectively constitute the autocatalytic reaction cycle. These bases acted on sugar molecules of substrates together with sodium ions of a Lewis acid to promote deprotonation under neutral conditions, which is the initiation step of the reactions forming an autocatalytic cycle, whereas the Cannizzaro reaction was inhibited. The autocatalytic reaction cycle established using this abiotic approach is a robust sugar production system. Furthermore, we found that the synthesized sugars work as energy storage substances that sustain microbial growth despite their absence in nature.

Visualizing Invisible Phase Transitions in Blue Phase Liquid Crystals Using Early Warning Indicators.

Changes in the statistical properties of data as a system approaches a critical transition is studied intensively as early warning signals, but their application to materials science, where phase transitions-a type of critical transition-are of fundamental importance, are limited. Here, a critical transition analysis is applied to time-series data from a microscopic 3D ordered soft material-blue phase liquid crystals (BPLC)-and demonstrates that phase transitions that are invisible under ambient conditions can be visualized through the choice of appropriate early warning indicators. After discussing how a phase transition affects the statistical properties in a system with a Landau-de Gennes type free energy potential, the predicted changes are experimentally observed at the two types of phase transitions that occur in a BPLC: the isotropic to simple cubic, and simple cubic to body-centered cubic transitions. In particular, it is shown that the skewness of the intensity distribution inverts its sign at the phase transition, enabling temporally and spatially resolved mapping of phase transitions. This approach can be easily adapted to a wide variety of material systems and microscopy techniques, providing a powerful tool for studying complex critical transition phenomena.

Positive Feedback Mechanism to Increase the Charging Voltage of Li-O2 Batteries.

The large overpotential of nonaqueous Li-O2 batteries when charging causes low round-trip efficiency and decomposition of the electrode materials and electrolyte. The origins of this overpotential have been enthusiastically explored to date; however, a full understanding has not yet been reached because of the complexity of multistep reaction mechanisms. Here, we applied structural and electrochemical analysis techniques to investigate the reaction step that results in the increase of the overpotential when charging. Rietveld refinement of ex situ powder X-ray diffraction showed that a Li-deficient phase of Li2O2, Li2-xO2, formed when discharging and was present over the course of charging. The galvanostatic intermittent titration technique revealed that the rate-determining process in the first step of charging was a solid-solution type of delithiation. The chemical diffusion coefficient of Li+ ions in Li2-xO2, DLi, decreases as the cell voltage increases, which in turn leads to a decrease in the oxidation rate of Li2-xO2. Under galvanostatic conditions, the deceleration of oxidation induces further increase of the cell voltage; therefore, an intrinsic mechanism of positive feedback to increase the cell voltage occurs in the first step. The results demonstrate that the continuity of the first step can be extended by the suppression of changes in any of the elements of the positive feedback loop, i.e., the oxidation rate, cell voltage, or DLi.

Synergistic Effect of Binary Electrolyte on Enhancement of the Energy Density in Li-O2 Batteries.

Enhancement of the discharge capacity of lithium-oxygen batteries (LOBs) while maintaining a high cell voltage is an important challenge to overcome to achieve an ideal energy density. Both the cell voltage and discharge capacity of an LOB could be controlled by employing a binary solvent electrolyte composed of dimethyl sulfoxide (DMSO) and acetonitrile (MeCN), whereby an energy density 3.2 times higher than that of the 100 vol % DMSO electrolyte was obtained with an electrolyte containing 50 vol % of DMSO. The difference in the solvent species that preferentially solvates Li+ and that which controls the adsorption-desorption equilibrium of the discharge reaction intermediate, LiO2, on the cathode/electrolyte interface provides these unique properties of the binary solvent electrolyte. Combined spectroscopic and electrochemical analysis have revealed that the solvated complex of Li+ and the environment of the cathode/electrolyte interface were the determinants of the cell voltage and discharge capacity, respectively.

Negative differential resistance as a critical indicator for the discharge capacity of lithium-oxygene batteries.

In non-aqueous lithium-oxygen batteries, the one-electron reduction of oxygen and subsequent lithium oxide formation both occur during discharge. This lithium oxide can be converted to insulating lithium peroxide via two different pathways: a second reduction at the cathode surface or disproportionation in solution. The latter process is known to be advantageous with regard to increasing the discharge capacity and is promoted by a high donor number electrolyte because of the stability of lithium oxide in media of this type. Herein, we report that the cathodic oxygen reduction reaction during discharge typically exhibits negative differential resistance. Importantly, the magnitude of negative differential resistance, which varies with the system component, and the position of the cathode potential relative to the negative differential resistance determined the reaction pathway and the discharge capacity. This result implies that the stability of lithium oxide on the cathode also contributes to the determination of the reaction pathway.

Publisher Correction: Negative differential resistance as a critical indicator for the discharge capacity of lithium-oxygen batteries.

The original version of this Article contained an error in the title, which was previously incorrectly given as 'Negative differential resistance as a critical indicator for the discharge capacity of lithium-oxygene batteries'. The correct version states 'lithium-oxygen' in place of 'lithium-oxygene'. This has been corrected in both the PDF and HTML versions of the Article.

A highly efficient Li2O2 oxidation system in Li-O2 batteries.

A novel indirect charging system that uses a redox mediator was demonstrated for Li-O2 batteries. 4-Methoxy-2,2,6,6-tetramethylpiperidinyl-1-oxyl (MeO-TEMPO) was applied as a mediator to enable the oxidation of Li2O2, even though Li2O2 is electrochemically isolated. This system promotes the oxidation of Li2O2 without parasitic reactions attributed to electrochemical charging and reduces the charging time.

A highly concentrated catholyte based on a solvate ionic liquid for rechargeable flow batteries.

A redox-active supercooled liquid is obtained by forming a "solvate ionic liquid" from a mixture of a stabilized organic radical and a specific Li salt and stabilizing the mixture further below their melting points. As a catholyte, the addition of an appropriate amount of water helps to enhance the electrochemical advantage while maintaining its supercooled nature and the liquid shows a high energy density of 200 W h L(-1) with reversible charge/discharge.

Catalytic Cycle Employing a TEMPO-Anion Complex to Obtain a Secondary Mg-O2 Battery.

Nonaqueous Mg-O2 batteries are suitable only as primary cells because MgO precipitates formed during discharging are not decomposed electrochemically at ambient temperatures. To address this problem, the present study examined the ability of the 2,2,6,6-tetramethylpiperidine-oxyl (TEMPO)-anion complex to catalyze the decomposition of MgO. It was determined that this complex was capable of chemically decomposing MgO at 60 °C. A catalytic cycle for the realization of a rechargeable Mg-O2 electrode was designed by combining the decomposition of MgO via the TEMPO-anion complex and the TEMPO-redox couple. This work also demonstrates that a nonaqueous Mg-O2 battery incorporating acrylate polymer having TEMPO side units in the cathode shows evidence of being rechargeable.

Quantitation of Li2O2 stored in Li-O2 batteries based on its reaction with an oxoammonium salt.

Precise knowledge of the discharge and charge reactions within Li-O2 batteries is an important aspect of developing highly efficient, rechargeable Li-O2 cells. We describe an analytical method capable of determining the quantity of Li2O2 in the cathode on the basis of the reaction of Li2O2 with an oxoammonium salt.

A rechargeable non-aqueous Mg-O2 battery.

We propose a catalytic cycle using the iodine-dimethylsulfoxide (I2-DMSO) complex for the realization of secondary Mg-O2 batteries. We have demonstrated that the Mg-O2 battery incorporating an I2-DMSO complex electrolyte showed evidence of being rechargeable.

Mechanism of helix induction in poly(4-carboxyphenyl isocyanide) with chiral amines and memory of the macromolecular helicity and its helical structures.

An optically inactive poly(4-carboxyphenyl isocyanide) (poly-1-H) changed its structure into the prevailing, one-handed helical structure upon complexation with optically active amines in dimethylsulfoxide (DMSO) and water, and the complexes show a characteristic induced circular dichroism in the polymer backbone region. Moreover, the macromolecular helicity induced in water and aqueous organic solutions containing more than 50 vol % water could be "memorized" even after complete removal of the chiral amines (h-poly-1b-H), while that induced in DMSO and DMSO-water mixtures containing less than 30 vol % water could not maintain the optical activity after removal of the chiral amines (poly-1a-H). We now report fully detailed studies of the helix induction mechanism with chiral amines and the memory of the macromolecular helicity in water and a DMSO-water mixture by various spectroscopic measurements, theoretical calculations, and persistence length measurements together with X-ray diffraction (XRD) measurements. From the spectroscopic results, such as circular dichroism (CD), absorption, IR, vibrational CD, and NMR of poly-1a-H, h-poly-1b-H, and original poly-1-H, we concluded that the specific configurational isomerization around the C horizontal lineN double bonds occurs during the helicity induction process in each solvent. In order to obtain the structural information, XRD measurements were done on the uniaxially oriented films of the corresponding methyl esters (poly-1-Me, poly-1a-Me, and h-poly-1b-Me) prepared from their liquid crystalline polymer solutions. On the basis of the XRD analyses, the most plausible helical structure of poly-1a-Me was proposed to be a 9-unit/5-turn helix with two monomer units as a repeating unit, and that of h-poly-1b-Me was proposed to be a 10-unit/3-turn helix consisting of one repeating monomer unit. The density functional theory calculations of poly(phenyl isocyanide), a model polymer of h-poly-1b-Me, afforded a 7-unit/2-turn helix as the most possible helical structure, which is in good agreement with the XRD results. Furthermore, the persistence length measurements revealed that these structural changes accompany a significant change in the main-chain stiffness. The mechanism of helix induction in poly-1-H and the memory of the macromolecular helicity are discussed on the basis of these results.

Synthesis of functional poly(phenyl isocyanide)s with macromolecular helicity memory and their use as asymmetric organocatalysts.

To develop a novel polymer-based asymmetric organocatalyst, a series of helical poly(phenyl isocyanide)s with functional pendant groups were prepared by modifying the side groups of the optically active helical poly(4-carboxyphenyl isocyanide) with a macromolecular helicity memory. Helical polyisocyanides partially modified with achiral amines, such as piperazine, maintained their chiral memory and enantioselectively catalyzed a direct aldol reaction. Although the enantioselectivity was low, the original helical poly(4-carboxyphenyl isocyanide) showed no catalytic activity. These results indicated that the macromolecular helicity of the modified polyisocyanides together with bifunctional amino and carboxy acid pendant residues arranged in a helical array along the polymer backbones plays an important role in the enantioselectivity.

[Approach to easing occupational stress for high-stress workers: applying the brief job stress questionnaire to workplace mental health promotion].

We investigated job stress among 442 employees from 19 divisions in a Japanese company using the Brief Job Stress Questionnaire. Job stress of the employees was estimated by the score for total health risk. Among the 19 divisions, two divisions showed over 120 points of mean total health risk score. Intervention with a stress-reduction program was carried out in these 2 divisions. First, to assess the job stress, health care staff interviewed all workers in the 2 divisions. Second, the results of the interviews were reported to the divisions' managers. Third, the managers applied the best remedy for job stress in their workplaces. In addition, occupational health staff conducted mental health education as well as individual interviews for the workers from the 2 divisions. At reevaluation one year later, both divisions showed a decreased general health risk (under 120 points). No sick leaves for depression occurred within the 2 divisions during the intervention. The results of the present study suggest that the intervention was effective in easing occupational stress for high-stress workers. The stress reduction program also seemed to have helped managers to change their recognition of occupational mental health and enabled close cooperation with occupational health staff, which may improve mental health in the workplace.

Unexpected thermally stable, cholesteric liquid-crystalline helical polyisocyanides with memory of macromolecular helicity.

The achiral sodium salt of poly(4-carboxyphenyl isocyanide) (poly-1-Na) folds into a one-handed helix induced by optically active amines in water. The induced helicity remains when the optically active amines are completely removed, and further modification of the side groups to amide residues is possible without loss of memory of macromolecular helicity. Although the helical poly-1-Na loses its chiral memory at high temperature, helical polyisocyanides modified with achiral primary amines, which no longer have any chiral components, keep their memory perfectly even at 100 degrees C in N,N-dimethylformamide in some cases and exhibit cholesteric liquid-crystalline phases, thus providing a robust scaffold with heat resistance to which a variety of functional groups can be introduced.

Ligand effects on ESR and optical properties of gold atoms in gamma irradiated organic solid solutions at 77 K.

Ligand effects on ESR and optical properties of Au0 atoms produced at 77 K in gamma irradiated solid solutions of AuCl/MTHF and AuCl/EtOH with and without HCl were investigated. Four groups of ESR lines were observed at 73 K more clearly around the magnetic fields at about 250, 280, 340, and 400 mT for both gamma irradiated MTHF and EtOH solid solutions with HCl than those without HCl. The values of a and g(J) calculated by Breit-Rabi analysis showed a remarkable dependence on the solvent polarity. It was confirmed that the signals were the hyperfine quartet corresponding to the transitions between the Zeeman levels of Au0 atoms with nuclear spin of 3/2 in the ground state, 2S(1/2). It was also confirmed that Au0 atoms produced after gamma irradiation were located in the nuclear environment of isotropic interaction with surrounding ligand molecules. Delocalization of the unpaired spin density of Au0 onto ligands is found to be as large as one in the case of Cu0 atoms. Our previous hypothesis of the occurrence of configuration mixing of d valence orbital into the wave function of the atom in its 2S(1/2) was strongly supported. The dependence of the ESR, optical absorption, and the steady-state emission and excitation characteristics on solvent polarity was cleared in this study. We observed two kinds of emissions i.e., a band at 385 nm and a set of emission bands at 456, 482, 484, and 520 nm. These correspond to two bands out of the six kinds of emissions observed previously. The bands were attributed to exciplex (Au0 x Ln...Au+)* and the excited Au0 atoms trapped in a large cavity, respectively. The negative counterion of Au+ of the gold compound plays an important role for the formation of the exciplexes.