Reduction and oxidation of perovskite-structure transition-metal oxide thin films are highlighted. Oxygen ions are released from and incorporated into the perovskite-structure framework during the reduction and oxidation. Low-temperature topochemical reduction reaction with CaH2 enables us to prepare infinite-layer structure oxide thin films containing Fe and Ni. With the epitaxially grown thin film samples, anisotropic rearrangement and transfer of oxygen ions in the structures have been revealed. Selective reduction of layers in artificial superlattices was also found, and the observed behavior suggests that the oxygen-ion mobility in the artificial superlattices was confined within the two-dimensional brownmillerite layer. Specific structural features play important roles in the oxygen-ion transfer in solids at low temperatures. The obtained results would be a key to develop technologies related to energy and the environment.
Reduction and oxidation of perovskite-structure transition-metal oxide thin films including artificial superlattices are highlighted. With the epitaxially grown thin film samples, anisotropic rearrangement and transfer of oxygen ions in the structures have been revealed.
In 2008, we reported a new class of macrocyclic hosts called “pillararenes.” They combine the advantages and aspects of traditional hosts and have a composition similar to those of typical calixarenes. Pillararenes have repeating units connected by methylene bridges at the para-position of benzene moieties, and thus they have a unique symmetric pillar architecture differing from the basket-shaped structure of calixarenes bridged at the meta-position of benzene moieties. Pillararenes show high functionality similar to cyclodextrins and can capture electron-accepting guest molecules within their cavity similarly to cucurbiturils. In this account, the synthesis, structure, and host–guest properties are discussed, along with pillararene-based supramolecular architectures.
In 2008, we reported a new class of macrocyclic hosts we named “Pillararenes.” In this account, the synthesis, structure, rotation, host–guest properties, planar chirality and functionality of pillararenes are discussed, along with pillararene-based supramolecular architectures.
Graphene oxide (GO), one of the best transparent substrates for electron microscopy of biological substances, is known to be not very stable to exposure to electron beams (e-beams). We present a method of the preparation of GO film highly resistive to e-beams by controlling layer-by-layer thickness and quantitatively examined the stability of GO film thus prepared. Scanning transmission electron microscopic measurements were engaged in these films with 10-kV acceleration-voltage. A simple method is proposed to classify the layer structure of GO. As an application of the method, we determined the electron attenuation length through GO film in nm scale.
Stable multilayer graphene oxide film toward electron beam irradiation was successfully prepared and examined by STEM, giving layer-by-layer electron attenuation profile after a contrast analysis.
Crystal structures of E13K [Glu13 with negative charge in wild type (WT) was replaced by Lys with positive charge] and E13R (Glu13 was replaced by Arg with positive charge) of flavin mononucleotide-binding protein (FMN-bp) from Desulfovibrio vulgaris (Miyazaki F) were determined by X-ray diffraction method. Ultrafast fluorescence dynamics of FMN in these proteins were measured by fluorescence up-conversion. The average lifetimes of E13K and E13R were 0.198 and 0.186 ps, which are compared to the reported lifetimes of WT, E13T (Glu13 was replaced by Thr with neutral charge) and E13Q (Glu13 was replaced by Gln with neutral charge) FMN-bp, 0.220, 0.872, and 1.10 ps, respectively. These ultrashort lifetimes are ascribed to photoinduced electron transfer (ET) from Trp32, Tyr35, and Trp106 to the excited isoalloxazine. The observed lifetimes of the five FMN-bp isoforms were simultaneously analyzed with both Marcus and Hush, and Kakitani and Mataga ET theories, in order to characterize the ET mechanisms. It was concluded that the electrostatic (ES) energy between the photoproducts and ionic charges inside the proteins is a key factor for the ET rate in the flavoproteins.
The crystal structure analysis of glycerol was revisited and the hydrogen atoms of three hydroxy groups were observed. A hydrogen-bonded 3D network structure of glycerol was created by the formation of a wave-like sheet structure and its assembly through hydrogen bonding.
Self-assembled adlayers of a series of anthraquinone derivatives, 2-alkoxyanthraquinone (n-ant, n = 14, 15, 16, 17, 18, 20, and 22) where n stands for the alkyl (CnH2n+1) chain length, on highly oriented pyrolytic graphite (HOPG) surface are investigated by scanning tunneling microscope (STM). Anthraquinone derivatives are found to form C–H···O hydrogen-bonded dimers. However, the self-assembled 2D pattern of monolayer depends on the parity (odd/even) of carbon atoms and the length of the alkyl chains. When n is even in number, the aggregating structure in the monolayer is interdigitated lamellar structure. The specific feature of these lamellae is the propagation of dislocations. The frequency of dislocation increased as the alkyl chain elongated. However, when n is odd in number, molecules adopt different conformation (type B) and the aggregating structure changes drastically. This indicates that the orientation of the terminal methyl of the alkyl group induces the surface structural change, i.e., the odd–even effect.
We report the preparation of a sodalite (SOD) layer on a cordierite substrate as a protective barrier against the potassium species using an in situ hydrothermal method. The performance of the potassium carbonate-loaded layer was characterized by scanning electron microscopy–energy-dispersive X-ray (SEM-EDX) measurements before and after thermal treatment at 1073 K for 5 and 50 h. A low potassium content detected at the layer–substrate interface of the samples before and after heating for 5 h indicates that the cordierite substrate was protected against potassium species by the generated SOD layer, whereas heating for the longer period of 50 h resulted in further migration of potassium species. The mobility of the potassium species is likely to be principally governed by diffusion along the defects of the material that appear during thermal treatment. It is suggested that migration of the potassium species might be prevented by the formation of a defect-free layer.
Sulfated anatase-titania (TiO2–SO42−) has been used as a solid acid catalyst for the synthesis of substituted pyrroles from γ-diketone and aromatic/aliphatic (acyclic and cyclic) primary amines by simple physical grinding. This sulfated titania gives an excellent yield with less reaction time and is an inexpensive, easily recyclable nanocatalytic material for this reaction. Higher catalytic activity of TiO2–SO42− is due to its increased Brønsted acidity.
As both iron and vanadium sources, the spherical amorphous FeVO4·xH2O powders are synthesized through an aqueous precipitation method by using Fe(NO3)3, NH4VO3, and ammonia water as starting materials. The effects of pH value of precursor solution on the Fe/V molar ratio is studied, it is found that when the pH is 4, the Fe/V molar ration is 1.004, it is close to 1. The FeVO4·xH2O powders are preheat treated at 600 °C for 12 h in air to obtain triclinic FeVO4. The FeVO4 powders are homogeneously mixed with Li2CO3, NH4H2PO4, and oxalic acid with stoichiometric ratio, and then sinter at 750 °C for 12 h in argon atmosphere to obtain LiFePO4–Li3V2(PO4)3 composite material. The structural properties, particle morphology, and electrochemical performance of composite cathode material LiFePO4–Li3V2(PO4)3 were studied. The FeVO4 not only plays as the main reactant to form LiFePO4 and Li3V2(PO4)3, but also as the dopants doping LiFePO4–Li3V2(PO4)3. The LiFePO4–Li3V2(PO4)3 composite cathode shows good electrochemical performance, and its discharge capacity is about 138.7 mA h g−1 at 1 C rate after 100 cycles, which retains 93.3% of it’s theoretical capacity (148.6 mA h g−1) for composite cathode material LiFePO4–Li3V2(PO4)3 in the voltage range of 2.5–4.5 V.
The photocatalytic H2 evolution by Pt-loaded TiO2 was examined using sacrificial agents such as 1,2-ethanediol, glycerol, erythritol, and arabitol, the carbons of which all have hydroxy groups. In these cases, almost complete decomposition of sacrificial agents into CO2 and H2O occurred. Moreover, the H2 evolution reached the maximum values estimated by their potentially electron-donating ability. On the other hand, smaller amounts of CO2 and H2 were evolved from 1,2,3-butanetriol, 1,2,4-butanetriol, and 1,2-butanediol, which had both continuous hydroxylated carbons and one or two non-hydroxy-substituted carbons, the inner continuous 2,3-butanediol, and the discontinuous 1,3- and 1,4-butanediols. In the cases of monools such as 2-butanol and 2-propanol, CO2 was not evolved at all. Thus, we found that the structure of sacrificial agents, more so than the potential electron-donating ability, is an important factor to evolve H2 efficiently.
Polymeric vinyl cinnamate (VC)–silver hybrid nanoparticles were synthesized by near-UV irradiation of VC vapor containing silver nanoparticles. The size increase of treated silver nanoparticles was observed using a differential mobility analyzer. The mass spectra of the nanoparticles suggested the presence of photopolymerization products.