We previously reported that 2-aminotryptanthrin (T2NH2) possesses excellent photophysical properties such as wide-wavelength absorption and emission in the visible region and a high fluorescence quantum yield. It also exhibits large positive fluorescent solvatochromism. In this study, we synthesized 2-(N,N-dimethylamino)tryptanthrin (T2NMe2), from which we expected a substantial bathochromic shift of the emission band to the near-infrared (NIR) region by acceleration of intramolecular charge transfer. As such, the emission maxima (λf, max) of T2NMe2 in some solvents were observed in the NIR region.
Nanoscale investigations of the condensed states of colloidal particles in confined regions provide useful results for both theoretical and experimental materials research. In particular, colloidal particles encapsulated in giant vesicles (GVs) have attracted much attention for the investigation of entropy effects in statistical physics and soft matter science. GVs with encapsulated colloidal particles undergo shape changes due to entropic interaction. In this paper, polyhedral configurations of GVs were observed for the first time using confocal laser scanning fluorescence microscopy. This characteristic configuration was associated with the coexistence of crystallized and disordered phases of colloidal particles in the GVs. Several triangular faces of crystals for colloidal particles formed on the GV membrane were identified. The characteristic patterns of colloidal particles observed in such faces corresponded to close-packing structures and suggest an orderly array of particles. However, the disordered phase was retained at the central part of the GV. For material research, it should be stressed that colloidal particles encapsulated GVs are useful for the investigation of condensed states appearing in the neighborhood of boundary composed of soft matters.
A highly π-conjugated helical compound, 11-oxahelicene (O9H), and its derivative 9-diethyleneglycoxy-11-oxahelicene (2EO9H) were used to prepare thin films by the Langmuir technique, and their structures and photoelectrochemical properties were evaluated. Brewster angle microscopic (BAM) observation implied that 2EO9H molecules formed a homogeneous, flat monolayer but O9H molecules three-dimensionally aggregated at the air-water interface. The same morphological features were also observed for films deposited on silicon wafers using atomic force microscopy (AFM). The film structures on solid supports were estimated by X-ray reflectivity (XR) measurements. The XR fitting analysis and theoretical calculation suggested that in the 2EO9H monolayer the hydrophobic aromatic planes of helicene moiety oriented perpendicularly to the monolayer plane and the hydrophilic diethyleneglycoxy group (DEG) was bended/twisted. It was also indicated that optical band gaps estimated from UV-visible spectra are not much changed due to introduction of DEG chain to the O9H moiety, but the 2EO9H monolayer showed larger photocurrent densities.
A 6H-SiC substrate with femtosecond-laser-induced periodic nanostructures was used as an underlayer for GaN growth. GaN nuclei were formed on the periodic nanostructure selectively. The in-plane direction of GaN was dependent on the in-plane direction of the SiC substrate, and no dependent on the direction of the periodic nanostructures or laser scanning. We suggest that the fine structure and high wettability at the region of the periodic nanostructure enhanced the adsorption of GaN nuclei preferentially. This technique will enable selective growth without masks or solution exposure.
In the current study, we investigated the effect of alloy composition and heat treatment on the microstructure, thermal properties, and hardness of near-equiatomic Zr-Cu alloys. Zr-Cu alloys with near-equiatomic compositions were fabricated by an arc-melting method. Furthermore, some samples were heated at 800 ℃ for 1 hour an electric furnace, and then quenched in water. The samples, both before and after quenching, were analyzed by X-ray diffraction (XRD), differential scanning calorimetry (DSC), and Vickers hardness testing. It was confirmed that the Zr-Cu alloys consisted of three intermetallic compounds, ZrCu, Zr2Cu and Zr7Cu10. The volume fractions of these intermetallic compounds were affected by the alloy composition and quenching. Furthermore, it was confirmed that the fabricated Zr-Cu alloys exhibit martensitic and reverse martensitic transformation with cooling and heating processes, respectively. However, the martensitic and reverse martensitic transformation temperatures showed very little change with varying alloy composition and quenching. In contrast, it was found that the Vickers hardness does change varying alloy composition and quenching.
Effective suppression of a bacterial quorum sensing (QS) could be achieved by adding A-B-A tri-block copolymer, poloxamer 84 or 407 into a culture broth, resulting in decrease of the QS-mediated phenazine production in Pseudomonas chlororaphis subsp. aurantiaca StFRB508. Dynamic light scattering measurements suggested to form self-associated micelles of respective poloxamer, because a single peak in the size distribution was observed under the same concentration (1 wt%) and temperature (30℃) for the QS suppressive test. The phenazine production in StFRB508 strain was known to be induced by N-hexanoylhomoserine lactone (C6HSL) and 3-hydroxy-hexanoylhomoserine lactone (3OH-C6HSL) as QS signaling molecules which can activate an expression of phenazine-related gene after sufficient increase of cell density. The micelles of poloxamer 84 and 407 could suppress the induced phenazine amounts to 55 and 60%, respectively. An N-acylhomoserine lactone (AHL) bioassay with Chromobacterium violaceum CV026 suggested effective trap of AHL derivatives to poloxamer micelles because the AHL concentration in the culture broth was obviously reduced in the presence of poloxamers.
We have successfully demonstrated a slight Bi deficiency makes the rhombohedral-tetragonal morphotropic phase boundary (MPB) much more dramatically shift to a lower Ba content in the (Na0.50Bi0.50)1-xBaxTi0.99Ce0.01O3 [(Ba, Ce)-co-substituted NBT] system than the (Na0.50Bi0.50)1-xBaxTiO3 [Ba-substituted NBT] system. Rietveld analysis of (Ba, Ce)-co-substituted NBT revealed that the composition giving the MPB was located at x = 0.44 in restraint of evaporation of sodium and bismuth using the polymerizable complex method, while it was x = 0.12 in the samples of (Na0.50Bi0.50-z)1-xBaxTi0.99Ce0.01O3-δ with a Bi deficiency of z = 0.03.
Membrane electrode assembly with SiO2 nano particles was prepared. And direct ethanol fuel cells (DEFCs) were constructed. The DEFCs were operated under both oxygen gas flow and normal air atmosphere conditions on the cathode electrode. In addition to the current density, the concentrations of acetaldehyde and acetic acid (intermediate reaction products) were determined as a function of operation time. For normal air atmosphere condition, the concentration of acetaldehyde decreased at the condition of high current, and the fuel cell current also decreased as the operation time increased. On the other hand, under the oxygen gas flow condition, the amount of acetaldehyde, which was the result of proton production, increased as operation time increased. The concentration of acetic acid increased for the oxygen gas flow measurements. The balance between anode and cathode chemical reaction must have the essential importance in DEFCs.
The decomposition of proteins on a surface was investigated using a low-temperature microwave plasma torch sterilization method. Albumin and keratin, used as model proteins, were irradiated with reactive species produced by an air microwave discharge plasma and their decomposition rates were approximately 0.1 mg/cm2 per 30 min. All chemical bonds in the proteins, including those involved in forming secondary structures, are decomposed by the reactive species. These findings suggest that the microwave plasma torch method could be useful for removing prion proteins from the surfaces of medical devices.
We have investigated water purifications by a discharge propagating in a bubble in water containing two organic compounds, phenol and sodium formate. In order to evaluate decomposition rate of phenol and sodium formate, the mixed solution of them were employed. Oxygen gas was injected into the water through a vertically positioned glass tube, in which the high-voltage wire electrode was placed to generate plasmas at low applied voltage. The phenol in the mixed solution was easier to decompose than the phenol in the single ingredient solution. The pH value of the solution after the discharge treatment increased with increasing initial concentration of the sodium formate, which enhanced the decomposition of phenol in mixed solution. The amount of decomposed sodium formate decreased with increasing initial concentration of the phenol.
Poly(acryl amide)s containing INC moiety in the side chain were prepared by radical polymerization using 6-(4-acryloylaminobenzoylamino)-1,7-dioctylindolo[3,2-b]carbazole (AAINC) as a novel monomer. The obtained polymers exhibited the good solubility and the high thermal stability, where Tg and Td5 of the homopolymer of AAINC were over 200℃ and 400℃, respectively. In addition, Tg of copolymers of AAINC with N-(p-tolyl)acrylamide increased as the INC content increased. It was found that the HOMO, LUMO levels and the energy gap of AAINC and polymers showed the similar values as those of INC, and the UV-Vis absorption and fluorescence spectra of these polymers were also similar to the tendency of photonic property of INC. Furthermore, the fluorescence intensity of these polymers was higher than that of the monomer, AAINC. Especially, the copolymer having 5% INC content showed the higher fluorescence intensity than the copolymers having the higher INC content.
ZnO/SnS heterostructures were fabricated by electrochemical deposition (ECD) for application to solar cells. SnS was deposited by three-step pulse ECD from a solution containing 100 mM Na2S2O3 and 30 mM SnSO4. To improve the film properties, tartaric acid (C4H6O6) was introduced as a complexing agent into the SnS deposition solution. The deposition with 100 mM tartaric acid resulted in larger optical transmittance and smaller oxygen content. ZnO was deposited on SnS by two steps pulse ECD from a solution containing Zn(NO3)2. Both the heterostructures fabricated with/without tartaric acid showed clear rectifying properties. However, photovoltaic properties were not improved by the addition of tartaric acid.
The potential lead-free piezoelectric bismuth sodium titanate, Bi0.5Na0.5TiO3 (BNT) solid solution, was investigated by means of an atomic pair-distribution function (PDF) method. BNT has been presumed thus far to exhibit the rhombohedral space group R3c at room temperature. The A site in BNT with an ABO3 perovskite structure was modified by Li and Ba atoms. Although average structures of the obtained Bi0.5Na0.4Li0.1TiO3 (BNLT) and 0.95Bi0.5Na0.5TiO3⋅0.05BaMn1/3V2/3O3 (0.95BNT⋅0.05BMV) solid solutions were similar to that of pure BNT, the local structures of these BNT-based compounds were slightly changed. In pure BNT, Bi atoms were shifted from the lattice point of the average structure. The bonds between Bi and O split in two PDF peaks owing to the off-center shift of Bi atoms. The modification of the A-site atoms in BNLT and 0.95BNT⋅0.05BMV to the BNT structure produces an apparent change in their local structures around Bi atoms.
Photovoltaic properties of BiFeO3 (BFO) and 10 % Mn-doped BFO (BFMO) epitaxial thin-film capacitors using SrRuO3 (SRO) electrodes are investigated. We found that the photovoltaic properties of the BFO capacitors are markedly degraded by the Mn-doping. Incident photon energy dependence of the photovoltaic properties shows that the BFO capacitors exhibit an apparent photovoltaic response even when the incident photon energy is lower than the band gap energy of BFO. This phenomenon is considered to be due to an internal photoemission (IPE) effect, that is, a photoinduced carrier injection from the SRO electrode to the BFO film. The utilization of the IPE effect is suggested to be an effective approach to enhance the photovoltaic properties of the ferroelectric capacitors under visible light illumination.
PLA plasma sterilization of yeast fungus and spore-forming bacteria was performed using Ti and TiO2 target. The experimental results suggested that both the yeast fungus and spore-forming bacteria could be sterilized by plasma irradiation generated by pulsed laser ablation method. The effect using pure Ti target slightly stronger than that of the TiO2 target. This results suggests that the main sterilization factors were considered to be high energy metal atoms and/or ions in this system.
Cobalt ions with the energy of 380 keV were implanted in pure copper. Changes in magnetic properties and local atomic structure around cobalt atoms which were induced by the implantation and the subsequent annealing at 873 K were investigated by using the SQUID and XAFS measurements, respectively. Just after the implantation, cobalt atoms replaced the regular copper atom sites in copper-fcc structure, and the magnetic state of cobalt atoms was nearly the paramagnetic state. By the subsequent annealing at 873 K for 1 hour, cobalt clusters which had the hexagonal close-pack (hcp) structure were produced, and the superparamagnetic state appeared. By the annealing for 24 hours, as each cobalt cluster grew to a larger size, and magnetic domain structures were produced in each cobalt cluster, the ferromagnetic state appeared.
In classical systems, our recent theoretical study provides new insight into how spatial constraint on the system connects with macroscopic properties, which lead to universal representation of equilibrium macroscopic physical property and structure in disordered states. These important characteristics rely on the fact that statistical interdependence for density of microscopic states (DOMS) in configuration space appears numerically vanished at thermodynamic limit for a wide class of spatial constraints, while such behavior of the DOMS is not quantitatively well-understood so far. The present study theoretically address this problem based on the Random Matrix with Gaussian Orthogonal Ensemble, where corresponding statistical independence is mathematically guaranteed. Using the generalized Ising model, we confirm that lower-order moment of density of eigenstates (DOE) of covariance matrix of DOMS shows asymptotic behavior to those for Random Matrix with increase of system size. This result supports our developed theoretical approach, where equilibrium macroscopic property in disordered states can be decomposed into individual contribution from each generalized coordinate with the sufficiently high number of constituents in the given system, leading to representing equilibrium macroscopic properties by a few special microscopic states.