The recent explosion in the field of nanotechnology provides promising application of manufactured nanomaterials in a variety of areas. On the other hand, it has been demonstrated that the relative surface area of ultrafine carbon black or metal oxide nanoparticles correlates with the degree of their toxicity. However, due to the lack of standardized methods to determine the physicochemical behavior of nanomaterials in biological systems, the mechanisms and nature of acute or chronic toxicity of engineered nanomaterials are not fully understood. Some nanomaterials are known to generate reactive oxidant species, resulting in induction of oxidative stress and inflammation. Oxidative stress is involved in the pathogenesis of cardiovascular diseases, such as hypertension and atherosclerosis. Therefore, there is concern that nanomaterials could have a major impact on the cardiovascular system, although the effects of exposure to newly developed nanomaterials on the cardiovascular system remain elusive. This review raises issues to consider for the assessment of cardiovascular toxicity of nanomaterials, and discusses recent in vitro or in vivo toxicity studies of nanomaterials.
We have developed self-standing bio-friendly nanosheets for biomedical applications. These nanosheets were fabricated by simple processes of spin-coating and a novel peeling technique from the substrate. Centimeter-sized nanosheets have unique properties such as amazingly flexibility and high adhesiveness. They could act as a novel wound dressing instead of conventional suturing in surgery. By contrast, fragmented submillimeter-sized nanosheets could act as aqueous surface modifiers to coat even uneven and irregular surfaces in addition to flat surfaces. In fact, such fragmented nanosheets exhibited a high potential to protect burned skin from bacterial infection and to provide blood compatibility to several surfaces. These nanobiomaterials therefore constitute a promising alternative to conventional therapies and coatings in biomedical fields.
It is well known that ferroelectric and antiferroelectric liquid crystals and liquid crystalline polymers are interesting candidates for their exclusive physical properties and industrial applications. For this reason, a wide variety of ferroelectric and antiferroelectric liquid crystals and liquid crystalline and polymers have been examined already and many are on the growing stage of investigation. The study of complex dielectric constant provides important evidences for understanding the interesting static and dynamic properties of these materials. In this review, we attempt to describe in detail about the collective and molecular dynamics of ferroelectric and antiferroelectric liquid crystals using broadband dielectric spectroscopy. Here, we have shown the dielectric properties of ferroelectric and antiferroelectric liquid crystals and polymers by varying the physical parameters, such as, temperature, frequency, bias field and the thickness of the liquid crystal films.
A quorum sensing (QS) as one of the intercellular bacterial communication systems could be successfully suppressed by enzymatic degradation of QS signals, N-acylhomoserine lactones (AHLs), inside polymer microcapsules. It is expected to isolate novel AHL-degrading bacteria and determine their AHL-degrading activity because the QS system dominates various bacterial functions including virulence expression and biofilm formation. As the QS activation index, producing red pigment prodigiosin which depends on the AHL-mediated QS in Serratia marcescens could be conveniently determined within 1-2 s by refractive spectrometer. Co-culture system of S. marcescens and model AHL-degrading Escherichia coli DH5α (pMAL-aiiA) which is genetically engineered to produce AHL-lactonase, AiiA, could successfully determine the AHL-degrading activity by measuring color change of the culture broth. To prepare the microcapsules embedded with the AHL-producer and AHL-degrader, calcium alginate microgel beads could be rapidly fabricated by coaxial microfluidic device, followed by forming polyion complex with ε-polylysine and removing Ca2+ ions in sodium citrate solution. This microcapsule co-culture model could follow the AHL degradation by the AHL-lactonase reaction because the a* as the red chroma index kept negative value even after 18 h co-culture. This paper suggests encapsulation of the co-culture system inside hollow microcapsules which enable simultaneous evaluation of the AHL-degrading average activity for approximately 100 samples within 1-2 s.
In this study, we have attempted to prepare novel aromatic polyamides containing indolo[3,2-b]carbazole (INC) moiety in the main chain. For this purpose, the synthesis of an aromatic dicarboxyl compound containing INC moiety was carried out. Novel aromatic polyamides containing INC moiety in the main chain were prepared by the polycondensation of the dicarboxyl INC monomer with the four kinds of diamine monomers. The obtained polymers were soluble in aprotic polar solvents such as N,N-dimethyl acetamide and N-methyl-2-pyrrolidone. According to the thermal gravimetric analysis, the obtained polyamides exhibited the relatively high thermal stability and the high char yield nearly 50 % at 1000 °C in the thermal degradation. Furthermore, it was found from the evaluation of the photonic property that the UV-Vis absorption and fluorescence spectra of these polyamides showed the similar tendency of the photonic property of INC.
The preparations of segmented polyurethanes containing phosphorylcholine (PC) group and polycarbonate segment were carried out by polyaddition of PC-containing diol monomer, 2-(3,5-bis(2-hydroloxyethoxy)benzoyloxy)ethyl phosphorylcholine, and polycarbonate diol with 4,4’-diphenylmethane diisocyanate. Then, the solubility, the surface property, the blood compatibility and the mechanical strength of the obtained polyurethanes were investigated to reveal the effect of the PC content on the physical and biological properties of polymer films. As a result, the obtained polyurethanes showed the high thermal stability and the elastic property. On the other hand, ultra-thin films (nanosheets) obtained from segmented polyurethanes showed a high adhesive strength and a tendency of shrinking. Furthermore, it was found that the nanosheets-coated surface prevented the adhesion and the activation of platelets.
The LiMn2O4 thin films for Li secondary batteries have been prepared by a RF magnetron sputtering method. In this research, we have prepared LiMn2O4 films under various preparation conditions. The charge-discharge characteristics of these films were evaluated. Several films showed good charge-discharge curve and good voltage, but charge-discharge efficiency was not so good. It was shown that the capacity of a film was approximately half of the theoretical value.
New red phosphors with nominal composition of Ca14(Al10-xMnx)Zn6O35 were synthesized successfully. The composition x at which the highest fluorescent intensity was obtained was found to be 0.09. The manganese ions were determined to be tetravalent and six-coordinated in the samples by analyses of optical absorption spectra and fluorescence spectra. These samples emit red fluorescence without most changes in chromaticity up to 200 °C with increasing temperature, though the fluorescence intensity decreased.
Tungsten oxide (WO3) hydrate nanorods were synthesized by solvothermal process under different condition (170-210ºC, acetic acid (0-10 ml). The morphologies of synthesized WO3 hydrate nanorods were investigated by scanning electron microscopy (SEM) and X-ray diffraction (XRD). As the result, we found the optimal synthesis condition of WO3 hydrate nanorods. In this optimal condition, the treatment temperature was 190ºC with no acetic acid in the reactive solution. The length and diameter of observed nanorods were approximately 1-20 μm and 50-1000 nm, respectively. The XRD analysis revealed that the crystal structure of WO3 hydrate (WO3 (H2O)0.33) nanorods has orthorhombic phase (Fmm2) with high crystallinity.
The objective of this study is to manufacture novel magnetic polymer nanoparticles with phospholipid polymer brush layers and functional groups to regulate the interactions with intercellular biomolecules or cells. The combination of the magnetic polymer nanoparticles and polymerase chain reaction technique would lead to the understanding of intracellular molecular reactions. In this study, we designed the polymer nanoparticles possessing a remote controllability and biomolecules-binding ability. Remote controllability was accomplished by encapsulating magnetic nanoparticles in the polymer nanoparticles via miniemulsion polymerization of styrene with Fe3O4 nanoparticles. To prevent the non-specific interaction with intracellular biomolecules, poly(2-methacryloyloxyethyl phosphorylcholine (MPC)) brush layer was constructed on the nanoparticles by surface-initiated atom radical polymerization. The magnetic polymer nanoparticles were specifically transferred into cells by immobilizing cell-penetrating peptide at the end of poly(MPC) chains. In particular, the applied external magnetic field enhanced cellular uptake.
Bismuth vanadate (BiVO4) powder was prepared by the sol–gel method using bismuth nitrate and ammonium vanadate as the starting precursors with mole ratio of 1:1 in ethanol media at 70ºC for 1h and calcined at 400–600°C for 2h. The phase structure of BiVO4 powder was characterized by X–ray diffractrometer (XRD). Single phase monoclinic of BiVO4 powder was obtained. The morphology of BiVO4 powder was characterized by scanning electron microscope (SEM). BiVO4 powder was irregular in shape with the particles’ size range of 100–300 nm. The functional groups of BiVO4 powder was identified by Fourier transform infrared spectrophotometer (FT–IR). The symmetric and asymmetric stretching of VO43- was showed at 826–829 and 737–741 cm-1, respectively. The surface area of BiVO4 powder was determined by surface area analyzer (BET) and shown in the range of 2.20–2.75 m2g-1. The photocatalytic degradation of 2,4-dichlorophenol was investigated by high performance liquid chromatograph (HPLC). The percentage of degradation of 2,4-dichlorophenol using BiVO4 powder after calcination at 500°C for 2h was 55.42%.
Model studies under biomimetic nondilute conditions are important to understand the effects of a cellular environment on nucleic acid molecules. Hydrogels forming a network structure have been used as a model for investigating the effect of a confined molecular environment on proteins but not on nucleic acids. The present study developed a method for preparing agarose and polyacrylamide gels for measuring the thermal stability of a double-stranded DNA polymer poly(dA)/poly(dT) in a confined environment. Gel materials were prepared by the addition of DNA before the formation of the gel network, but experiments for the analysis of DNA melting curves had several limitations. The shape and extent of hyperchromicity of the melting curve of poly(dA)/poly(dT) embedded in the agarose gel were similar to those obtained with the buffer solution. On the other hand, the UV absorbance of the polyacrylamide gel largely increased after heating, and thermal melting of poly(dA)/poly(dT) in the polyacrylamide gel started at a high absorbance, giving ambiguous results. Hydrogels prepared according to the procedure developed in this study would be useful for developing new strategies for studying the effects of confinement on nucleic acid molecules.
A low-bandgap small molecule, 7,7’-(4,4-bis(2-ethylhexyl)-4H-silolo[3,2-b:4,5-b’]dithiophene-2,6-diyl)bis(6-fluoro-4-(5’-hexyl-[2,2’-bithiophen]-5-yl)benzo[c][1,2,5]thiadiazole), (p-DTS(FBTTh2)2) has been incorporated into polymer solar cells based on blend of poly(3-hexylthiophene) (P3HT) and a fullerene derivative (PCBM) to improve the light-harvesting efficiency in the near-infrared (near-IR) range. With addition of a low concentration of p-DTS(FBTTh2)2, the short-circuit current density (JSC) increased significantly and hence the power conversion efficiency (PCE) was improved by more than 20% relative to that of the control device of P3HT/PCBM binary blend. This is due to the improvements in the external quantum efficiency (EQE) not only at the absorption band of p-DTS(FBTTh2)2 in the near-IR range but also at the P3HT absorption band in the visible range. Furthermore, the photoluminescence (PL) quenching efficiency of P3HT was much higher in the ternary blends than in the binary blend. These findings indicate that P3HT excitons can be dissociated into free charge carriers more efficiently in the presence of p-DTS(FBTTh2)2.
To analyze carrier behaviors leading to electroluminescence (EL) of double-layer organic light-emitting diodes (OLEDs), we used a novel microscopic electric-field-induced optical second-harmonic generation measurement system equipped with a radially polarized pulsed laser beam, which can probe two-dimensional electric field distributions in OLEDs. We showed a relationship between EL emission distribution and interfacial accumulated charge distribution.
Alpinia zerumbet (Pers.) B.L. Burtt & R.M. Smith is an aromatic plant, distributed widely in the Ryukyu Islands, Japan. It has been extensively studied because its essential oil has a variety of biological functionalities. Underwater shock waves consist of instantaneous high pressures that penetrate entire plant cells and selectively destroy the cell walls of leaves and stems by spalling destruction. Therefore, it is expected that exposing leaves to shock waves as a preprocessing step draws more effective extraction of essential oil by subsequent steam distillation. In this study, we prepared A. zerumbet materials that were subjected to underwater shock wave pretreatment, and evaluated its effect on the leaves for steam distillation. With shock wave loading, multiple cracks in the cell walls were observed by scanning electron microscopy. Moreover, the extracted volume of volatile compounds increased with the number of shock wave processing. In particular, the concentrations of camphor and p-cymene in the vapor phase increased more than four times compared with these of untreated leaves. Underwater shock wave processing selectively and effectively destroyed the fiber and/or cell structures. The headspace gas chromatography/mass spectrometry indicated that the volatile components within the structures were easily volatilized.
Highly dispersed and homogeneous titanium dioxide (TiO2) nanoparticles were synthesized by a solvothermal method with polymer gel. Polymer gel is essential for the highly dispersed and homogeneous nanoparticles. First, polyvinyl alcohol (PVA) was dissolved in water at 70°C and cooled to room temperature. Ammonium citratoperoxotitanate(IV) [(NH4)8[Ti4(C6H4O7)4(O2)4]・8H2O] was subsequently added and dissolved in the PVA solution. Next, water was evaporated from the PVA gel using a microwave. This polymer gel and ethanol as a reaction medium were placed into the Teflon reactor of a stainless-steel autoclave with an internal volume of 100 ml. Thereafter, the autoclave was sealed and kept at 230°C for 18 h. After solvothermal synthesis, the polymer gel was collected and dissolved in water at 50°C-70°C. X-ray diffraction (XRD) measurement, scanning electron microscope (SEM), and transmission electron microscope (TEM) observations were performed for the remaining unresolved polymer gel. XRD confirmed the presence of anatase TiO2. The crystallite particle size was estimated as 6.4 nm (D101) from the XRD 101 peak using the Scherrer’s equation. Highly dispersed and homogeneous TiO2 nanoparticles were obtained from TEM observation with a particle distribution of 5.6 ± 1.2 nm.
Nb-related perovskite oxides, such as NaNbO3, KNbO3, and AgNbO3, are the end members of novel ferroelectric materials. Although they have NbO6 octahedron, the phase transition mechanism changes depending on A-site ion. NaNbO3 and KNbO3 have rhombohedral structure at low temperature, and after the structural phase transition, orthorhombic structure appears. On the other hand, the monoclinic structure of AgNbO3 appeared as a disordered phase of rhombohedral structure. The rhombohedral structure is a highly ordered average structure, and the rhombohedral structure also tends to be subject to the influence of local randomness. We performed local structure analysis by using atomic pair-distribution function (PDF) and X-ray absorption fine structure (XAFS). Although these three materials have perovskite structures in which Nb occupies to B-site, local structures differ greatly. The Nb-O bond distribution appeared clearly in NaNbO3, but broaden in AgNbO3. The difference of local structures causes various phase transitions of Nb-related perovskite materials.
Polyethylene (PE) and Ti surfaces were irradiated with oxygen cluster ions. For PE surfaces, the sputtered depth increased with an increase in acceleration voltage, and the sputtering yield was approximately 243 molecules per ion at an acceleration voltage of 9 kV. Atomic force microscopy showed that surface roughness increased with an increase in acceleration voltage. The contact angle was between 70° and 80°, which was smaller than that for the unirradiated surface. Adhesion of mesenchymal stem cells (MSCs) could be obtained by adjusting acceleration voltage, although cell adhesion was not observed on the unirradiated surfaces. For Ti surfaces, the surface roughness did not change with cluster ion irradiation. However, the contact angle decreased with an increase in acceleration voltage, and it was 46° at an acceleration voltage of 9 kV. Furthermore, after ultraviolet light irradiation for 30 min, the contact angle decreased to 28°. With regard to cell adhesion, the number of MSCs attached to the Ti surface increased after oxygen cluster ion irradiation.
Photocatalytic properties of titanium dioxide layer deposited on silica glass (SG) including silver nanoparticles at a shallow depth were studied from an aspect of utilization of surface plasmon resonance (SPR) by nanoparticles. In order to adjust resonant photon energy of surface plasmon to the activation energies of 3.0 and 3.2 eV depending on crystallinity of TiO2, Ag nanoparticles were formed in SG at a shallow depth by silver negative-ion implantation and post annealing. Then, TiO2 layer was formed on it at temperatures of 200 and 500°C by rf magnetron sputter deposition. Ag nanoparticles were confirmed from optical absorption by the SPR at 3.0-3.1 eV. The deposited TiO2 film at substrate temperature of 200°C was found to have anatase-type nano-crystals from results of XRD and optically measured bandgap. Photocatalytic properties of TiO2 layer deposited on Ag-implanted silica glass at 200°C were evaluated by decolorization of methylene blue solution and compared with that of the TiO2 film deposited on unimplanted SG at the same conditions. As a result, the TiO2 layers deposited on Ag-implanted SG after annealing at 700°C were showed an enhancement in photocatalysis of factor 3.26.
We have realized element-specific pump-probe time-resolved hard X-ray photoelectron spectroscopy (TR-HAXPES) for the study of ultrafast electron dynamics in condensed matter. TR-HAXPES has been applied for the first time to determine the temporal evolution of space-charge effects on Ti 1s core-level photoelectron spectra of SrTiO3 at the SACLA X-ray free electron laser facility. We found that the temporal evolution of Ti 1s kinetic energy shifts can be well explained by a mean-field model for the electron propagation in the vacuum. We also report preliminary results of a real-time laser-assisted valence-transition in YbInCu4, observed by measuring Yb 3d5/2 core-level HAXPES spectra at BL19LXU of SPring-8, under ON/OFF conditions of an optical pump-laser. We observed drastic changes in intensities of the Yb2+ and Yb3+ spectral components induced by pump-laser irradiation.
This letter discusses the reason for the tunneling behavior of zinc based oxide semiconductor thin film transistors (TFTs). The device was fabricated using SiOC as a gate dielectric, which decreased polarities depending on the combinations of oxygen and carbon ions as opposite polar sites. The threshold voltage shifts in a zinc based oxide semiconductor are presented using the metal oxide semiconductor (MOS) structure analysis of Ohmic/Schottky and Poole-Frenkel (PF) contacts based on the drain-source current (IDS) and drain-source voltage (VDS) with change of gate voltage. The transfer characteristic of TFTs and stability were influenced by the polarities of the SiOC gate insulator. The threshold voltage shift effect was explained by a slow trapping of excess carriers in defects located at the SiOC interface. A stable TFT prepared on non-polar SiOC was achieved from PF contact due to the very high height of Schottky barrier. The IDS-VDS curve including the Ohmic contact at VG=0V and Schottky barrier with increase of gate voltage exhibited a tunneling behavior induced by diffusion currents. However, for the TFTs on polar SiOC with the trap charge, it was observed the trapping phenomenon transited from the localized state to band through the low potential barrier SB. The excess charge carriers in a localized trap state caused the threshold voltage shifts.
Fluorescence enhancement of CdTe nanocrystals through energy transfer to Ag nanocrystals is described, enabling us to fabricate highly luminescent quartz substrate. By immobilization of CdTe nanocrystals on Ag nanocrystals linked by dithiol molecules, fluorescence of CdTe nanocrystals is enhanced as compared to that of only CdTe nanocrystals. For example, the CdTe/Ag nanocrystals film linked by 1,5-pentanedithiol molecules exhibits ca. 3-fold fluorescence intensity of CdTe nanocrystals without Ag nanocrystals. Importantly, the fluorescence lifetime of this film decreased by complexation with Ag nanocrystals, indicating that the mechanism of fluorescence enhancement may be caused by energy transfer from CdTe to Ag nanocrystals. This effect depends on both distance between CdTe and Ag nanocrystals and types of metal nanocrystals. Fundamental understanding of enhancement effect by plasmonic nanocrystals paves the way toward the development of light-emitting devices, sensors, and energy conversion devices.
We investigated the hydrodistillation (HD) and supercritical fluid extraction (SFE) methods for the extraction of essential oils with antibacterial actions from lavender for use in aromatherapy and cosmetics. Extracts were analyzed by flame ionization detector-gas chromatography and mass spectrometer-gas chromatography. The HD method extracted 66 compounds, while SFE extracted 46. The principal components of the oils extracted by HD were linalyl acetate (25.3%), terpinen-4-ol (16.4%), and linalool (13.0%). The principal components extracted by SFE were linalyl acetate (30.6%), terpinen-4-ol (14.1%), and lavandulyl acetate (8.4%). The extraction rate of essential oil for the SFE method was at least 10 times that for the HD method. We also clarified that SFE is suitable for obtaining compounds that are unstable at relatively high temperatures and that HD is suitable for compounds with high volatility.
Bamboo powder was analytically pyrolyzed using pyrolysis-gas chromatography (Py-GC), and the effects of fast pyrolysis conditions on the product distribution of bio-oil were evaluated. 4-Vinylphenol (4VP) was identified as a major product of bamboo fast pyrolysis by 1H-NMR and 13C-NMR spectrometry. The formation pathway of 4VP demonstrated that p-coumarate esters are present in bamboo lignin, and 4VP is likely to be derived from these p-coumarate structures. The evaluation of the effect of fast pyrolysis temperature on the product distribution of bio-oil revealed that increasing pyrolysis temperature resulted in high yields of compounds containing a furan structure and reduced yields of phenolic compounds, except catechol. The fast pyrolysis of Klason lignin produced 4VP in lower yield than that from bamboo powder, even though the yield of 4-vinylguaiacol from acid lignin was greater than that from bamboo powder. In comparison with fast pyrolysis, slow pyrolysis of bamboo produced simple phenols, such as phenol, guaiacol, methyl guaiacol, syringol, and methyl syringol, in higher yields, whereas the yield of 4VP was lower than that from fast pyrolysis. The chemical characteristics of bio-oil depend on the biomass source, pyrolysis conditions, and the type of pyrolyzer.