Nowadays, nanotechnology is applied to an increasingly number of industries due to the unique properties of nanomaterials. Carbon nanotubes and carbon nanofibers are some of the most appealing nanomaterials that are commonly employed in electronics, photovoltaic, catalysis, environmental engineering, space engineering, and last but not least in medicine and pharmacy. However, the issue of handling such materials is not yet fully investigated. Without the essential and proper legislations and regulations, widespread use of nanotechnologies in many sectors of society may well be slowed down and could even come to a complete standstill. Thus, it is necessary to develop innovative methods for risk management. The exposure assessment of carbon based nanomaterials presents several challenges. It is easily understood that nanosafety and risk assessment are upon modern research fields. Moreover, it seems critically important to take into perspective the whole life cycle for carbon nanotubes and carbon nanofibers for the risk management. The purpose of this review is to present the current state of knowledge related to the risks of carbon nanotubes and nanofibers as well as to display the current actions in European Union regarding this issue.
We evaluated the crystallization effect of an internal electric field on thaumatin by application of extremely low voltage. A transparent cell used for crystallization comprises two parallel-plate electrodes of indium tin oxide (ITO) films, which enables the observation of the protein crystal growth through the plate electrodes. In suspensions with a precipitant, thaumatin crystal growth was induced by applying a sine-wave voltage of 1.06 V at f=20 Hz for 10 hr. We confirmed that low applied voltage promoted crystallization for thaumatin.
Light emitting diodes (LEDs) can act, not only as a light emitting element, but also as a light receiving element when being irradiated with light beams of an appropriate wavelength range in an appropriate manner. By employing this aspect, a simple demonstration set for optical communication has been prepared, in which LEDs are employed both as a light transmitting element and a light receiving element. In this set, LEDs with different colors can be selected as the light transmitting element and the light receiving element. Audio signals (music) can or cannot be reproduced in accordance with combinations of colors of these two LEDs. Thus, this demonstration set can act as a useful introductory tool for explaining relationships among colors of light (wavelengths or frequencies) from LEDs, their energy levels and band gap energies of semiconductor materials used for light emitting layers of the particular LEDs.
Aqueous dispersions of poly(3,4-ethylenedioxythiophene)/poly(4-styrenesulfonate) (PEDOT/PSS) with various PSS composition ratios (α) were newly synthesized and electromechanical properties of the PEDOT/PSS solid films were investigated for the applications to high-strain electro-active polymer (EAP) actuators. The electrical conductivity showed a maximum of 210 S/cm at α = 3, while the degree of water vapor sorption increased with increasing both α and relative humidity (RH). The EAP actuating behavior of the PEDOT/PSS solid films demonstrated that the film contraction attained as high as 7.8% at α = 15 and 70% RH which was more than three times higher than that of the commercial grade of PEDOT/PSS (2.4% at 50% RH).
Magnetic hyperthermia treatment (MHT) is a new cancer therapy approach that uses the heat generated by magnetic nanoparticles (MNPs) upon the application of an AC magnetic field. To successfully implement the therapy, it is important to estimate the heat dissipation mechanism based on the magnetic properties. Superparamagnetic iron oxide nanoparticles (SPION) for MHT were prepared using the co-precipitation method. The crystal structures were examined by X-ray diffraction. The average particle size of the samples ranged between 10.4 nm and 11.0 nm, depending on the preparation conditions, such as the pH. The heating and magnetic properties were dependent on not only the particle size but also the preparation conditions. To clarify the electronic state of the iron ions and the local structure, X-ray absorption fine structure (XAFS) measurements were performed. We concluded that the valence of the iron ions and local structures, including lattice vacancies, might be important in estimating the heat dissipation.
The reactivity of Cs and fly ash and the immobilization of Cs in the reaction products were investigated under hydrothermal conditions with NaOH solution. Crystalline phases of reaction products varied with hydrothermal conditions such as reaction temperature, concentration of NaOH solution and reaction time. The amount of immobilized Cs increased with the crystallization of pollucite, but its value decreased with the formation of other phases as Cs0.84Na2.16Al3Si3O12·0.32H2O, hydroxysodalite and hydroxycancrinite. A part of Cs was exchanged to Na on Na-P1 zeolite, which was formed in a dilute NaOH solution at low temperature for a long reaction time. The synthesized pollucite was the solid solution between pollucite and analcime, and the atomic ratio of Cs/(Cs+Na) in obtained products was larger than the initial ratio of Cs and NaOH solution in the system. This result suggests that Cs is more easily immobilized in the structure of synthesized pollucite than Na under hydrothermal treatments.
The hexavalent chromium which is a carcinogen is included in the chromium plating and is harmful to the human body and environment. Due to the environmental influence, substitution of hard chromium plating is required. Therefore, this research is focused on tungsten(W) features, which may improve the physical properties, and to evaluate the hardness and the abrasion resistance of Ni-W alloy plating films.
Some of fresh produces emit ethylene gas, one of plant hormones, which promotes the aging for themselves and accelerates senescence of other agricultural produce. In transportation of some kinds of agricultural produce, reducing ethylene gas in the transportation container is important for keeping freshness of fruits and vegetables. In this study, ethylene gas was decomposed using a dielectric barrier discharge (DBD) plasma reactor. The ethylene gas was diluted with the gas mixture of nitrogen, oxygen and carbon dioxide as simulated gas in the transportation container. The DBD plasma was generated by a pulse switching power supply consisted of MOS-FET switching devices, capacitors and pulse transformers. The mixture gas was contained harmful by-products, ozone and carbon monoxide after DBD plasma treatment. An Ag nanoparticle-loaded zeolite was set in the catalytic reactor to remove the by-products. The catalytic reactions reduced the by-products produced by the plasma treatment. It was confirmed that carbon monoxide diluted with simulated dry air was oxidized to carbon dioxide by the catalyst and DBD plasma.
We have made a SPR(Surface Plasmon Resonance) spectrometer combined with STM(Scanning Tunneling Microscope) to detect the nanoscale signal. The nanoscale signal from SPR measurements should be detected by approaching STM to the surface of the sample film using the effect of the near field due to the presence of STM tip, on the SPR angle, reflectivity and polarization change. To confirm the possibility of SPR in nanoscale, we have carried out the simulation for the detection of local SPR reflectivity for inhomogeneous sample on a nanometer scale. The layer model for STM tip has been employed to the measuring object in layers including prism, sample and air. On the basis of the present simulation, STM Tip effect on SPR reflectivity is less than ～0.7% of incident light intensity(beam size of 50μm) for the sample with homogeneity variation of 10-50%. We have discussed that the nanoscale measurements of SPR combined with STM can be detected by using small size of laser beam less than 50μm and the STM tip positioning in the range from 1nm through 500nm.
Adsorption behavior of fibrinogen was examined in terms of the direct interaction force operating between fibrinogen and surfaces. As model surfaces, well-characterized polymer brush surfaces were systematically prepared by surface-initiated atom transfer radical polymerization method using zwitterionic, cationic, anionic, and hydrophobic monomers. The direct interaction forces between fibrinogen and the polymer brush surfaces were quantitatively evaluated by the force-versus-distance curve measurement of atomic force microscopy using fibrinogen-immobilized probe. Besides, the amount of fibrinogen adsorbed on these polymer brush surfaces was quantified by surface plasmon resonance measurement. The cationic, anionic, and hydrophobic polymer brush surfaces strongly interacted with fibrinogen, and a large amount of fibrinogen adsorbed on them. On the other hand, in the case of the zwitterionic polymer brush surface, direct interaction force with fibrinogen was weak, and fibrinogen adsorption was dramatically suppressed. It was quantitatively indicated that the strength of direct interaction force operating between fibrinogen and surfaces would influence on fibrinogen adsorption on surfaces.
The purpose of the present study is to investigate the changes in the internode length and cellulose crystallinity of moso bamboo (Phyllostachys pubescens Mazel) cell walls during the growth process of bamboo, including a few days growth young bamboo shoots. Specimens were prepared from bamboo culms that either continually grew throughout the growth period or stopped elongation growth in the course of growing. Cellulose crystallinity showed clear differences between above two types of bamboo culm regardless of growth period, while no significant changes were observed in internode length in each growth periods of bamboo culms. Crystallinity of continually growing bamboo culms increased from lower to higher internodes with the progress of growth. On the other hand, crystallinity of culms that stopped elongation growth remained relatively lower values compared to the former type even though the growth period was same. These microscopic features of bamboo cell walls may helpful to predict whether bamboo culms will stop their elongation growth.
Marimo carbon is a fibrous carbon material that has attracted attention in many fields, such as for its use in electronic devices and capacitors. It has diamond particles in its core, with carbon nanofilaments radiating outward from diamond core. In this study, we synthesized marimo carbon using an oxidized diamond-supported catalyst by fluidized bed chemical vapor deposition (CVD) and rotary fluidized bed CVD. This demonstrated that fluidized bed technology can be used for the cost-efficient, large-scale production of uniform marimo carbon.
The authors have investigated a new utilization of the rice hull, which is one of the agricultural wastes in Japan. This utilization is required from a viewpoint of the recycling. The rice hull silica carbon material (RHSC) is manufactured by mixing the rice hull particles with a phenol resin, pressure forming, drying, and then by carbonizing in nitrogen gas atmosphere at high temperatures. Since the rice hull has a natural porous structure, the RHS carbon is manufactured as a porous carbon material. The inorganic component in the rice hull is almost Si. Therefore, the RHSC was expected as the sliding materials such as the linear motion bearing, because it has excellent water resistance and abrasion resistance under unlubricating conditions. In this study, the compressive strength by atmospheric exposure test was examined and discussed of the RHSC. The atmospheric test was carried out referring to the Japanese Industrial Standards of JIS-Z 2381. Through one year, deterioration of the compressive strength on RHSC was not observed. RHSC is expected to be applied to the bearing in outdoor environment and linear motion bearing.
ZnO nanoparticles were prepared by a solution method and a film of these nanoparticles was prepared by the Langmuir-Blodgett (LB) method. To prepare the LB film, the dispersibilities of ZnO nanoparticles in water and organic solvents were examined. The surface of the ZnO nanoparticles was modified by a surfactant, cetyltrimethylammonium bromide (CTAB), to improve their dispersibility. Using water as a solvent, dispersibility was improved by changing the CTAB concentration. However, aggregation of the nanoparticles occurred when they were transferred to chloroform to spread on water for fabrication of the LB film. With an organic solvent, aggregation of the ZnO nanoparticles in the LB film was improved when chloroform was used.
Ferrocene-doped C60 nanosheets consisting of alternating C60 and ferrocene layers were grown by liquid-liquid interfacial precipitation method, and their pressure-induced transformation at room temperature was investigated by means of Raman spectroscopy. The charge transfer and polymerization of C60 occur with increasing pressure even at room temperature, while the transition pressures are low compared with those of the same kind of sample reported previously. The discrepancy in the transition pressures can be attributed to the crystal quality. In addition, it should be noted that the structure of the sample recovered after decompression is found to be amorphous C60, although the Raman spectrum almost completely returns to the starting one of isolated C60. Such depolymerization of C60 would be due to the effect of ferrocene layers which stabilize the initial isolated C60 at ambient temperature and pressure.
A stochastic delay-derivative element (SDDE) using an immiscible polymer binary mixture of poly(L-lactic acid) with poly(ε-caprolactone) is fabricated, which is useful for a basic electronic component in a novel bioinspired signal/information processing device. Noise power spectral density(PSD) that is a Fourier transform of temporal correlation function of electric current fluctuations for SDDEs is investigated and the correlation between morphology of the binary mixture and PSD is explored. The PSD is varied with depended on the fabrication processes of SDDE and cooling procedure after the isothermal crystallization of PLLA.
Carbon nanotubes (CNTs) and carbon nanofilaments (CNFs) have attracted considerable interest in industry and many other fields such as for their use in electronic devices. In this study, CNFs were synthesized by decomposition of ethylene over Pd- and Ni-loaded oxidized diamond catalysts using a fluidized- bed reactor. We examined the effects of various internal structures on Li-ion battery anode properties. Electrochemical measurements indicated that CNF anodes displayed near the theoretical discharge capacity of graphite intercalation compounds (372 mAh/g) as well as high cycle retention. CNF anodes were thus found to be appropriate materials for the use in Li-ion batteries.
Barium magnesium silicate, BaMgSiO4, sintered together with H3BO3 in a reducing atmosphere is known to show photochromism, with the generation of a pink color following UV irradiation. It is thought that this photochromism originates from oxygen vacancies in the silicate. In this work, we investigated the nominal Ba-deficient composition Ba1-xMgSiO4-x (0 ≤ x ≤ 0.05) in an attempt to effectively generate oxygen vacancies in the silicate. BaMgSiO4 phases were obtained from a combination of BaCO3, MgO and SiO2, without the addition of H3BO3, by sintering in a reducing atmosphere. All samples were pink-colored after UV irradiation and this photochromism was confirmed to be an intrinsic property of BaMgSiO4. The color densities of our samples were inferior to that of a previously reported sample sintered with the addition of H3BO3, and the addition of H3BO3 is believed to improve the photochromism color density. A tendency for the color density to decrease with increasing Ba-deficiency was found among our samples. The observed degradation of the photochromism is discussed based on nonstoichiometry in the BaMgSiO4 phase.
A micro/sub-micrometer-sized potassium-sensitive electrode was fabricated and used as a probe for shear force-based scanning electrochemical microscopy (SECM) in standing approach mode, and the pores of a membrane filter were imaged as a model of living cells. In general, the electrode was prepared by silanizing the walls of a capillary with octadecyltriethoxysilane (ODS) to prevent penetration of aqueous solution into the capillary, and then filling with a solution of an ionophore. When this electrode approached the surface, the ionophore solution slightly protruded from the tip and contacted the sample surface. Therefore, the hydrophobic layer, at the tip of the capillary only, was removed. Because of this treatment, a very small amount of the aqueous solution penetrated the tip of the capillary when the electrode was immersed in aqueous solution. Using this capillary, SECM and topographic images of a polycarbonate membrane filter having 5 μm pores were successfully obtained.
The photovoltaic properties of dye sensitized solar cells fabricated by employing semiconducting porous films of amorphous ZnSnO3 as photoelectrodes were investigated. ZnSn(OH)6 nanoparticles were synthesized by mixing aqueous solutions of ZnSO4 and Na2SnO3, and amorphous ZnSnO3 films were formed on conductive glass plates by applying a paste containing the nanoparticles followed by heating at various temperatures. The photovoltaic properties of these devices were varied by modifying the heating temperature. The solar cell exhibiting the best performance employed an amorphous, porous ZnSnO3 film heated at 372 °C and was able to convert energy from a xenon light source to electric power. The relationships between the photovoltaic properties and the heating temperature are discussed according to an analysis of the internal resistance of the fabricated solar cells.
Applications in high-efficiency Si/β-FeSi2 heterojunction solar cells require the preparation of crack-free β-FeSi2 films on silicon. In a previous study, we obtained crack-free β-FeSi2 films on silicon(100) just substrate by substrate heating during RF-sputtering even though we annealed the films at temperatures as high as 900°C after deposition. However, these films contained a numerous silicon crystalline grains because of substrate heating. Moreover, this process required more energy for substrate heating during deposition. In this study, FeSix films were deposited on silicon(100) substrate 4° off the  direction at room temperature through the RF sputtering method using an FeSi3 target. The film annealed at 900°C also contained a large amount of silicon. Different from the films on silicon(100) just substrate, however, the film developed cracks on its surface.
Thermoelectric properties of In2-xMxO3 system doped with tetravalent metal (M) ions (Si4+, Ti4+, Ge4+, Sn4+, Te4+, and Ce4+) were investigated at temperatures up to 1273 K. For the Ge-substituted system, the power factor P takes a maximum of 9.5 × 10-4 W/K2m around 1150 K and dimensionless thermoelectric figure of merit ZT shows a maximum of 0.18 at 1000 K for the x=0.025 sample, which is the solubility limit of Ge. The maximum ZT of the In1.9M0.1O3 series was about 0.13 around 1000 K for the Si4+, Ge4+ and Sn4+ doped samples. We also investigated the thermoelectric properties of the In2O3-SnO2 system doped with pentavalent Sb element to replace the expensive In2O3 to the plentiful SnO2. The Sb atom was preferentially substituted for the In-site and the thermoelectric properties do not exceed those of pure In2O3. The potential of the thermoelectric properties in the doped In2O3-SnO2 system was discussed.
The far-infrared reflectance spectra of layered iron oxide LuFe2O4 have been investigated at external pressure up to 8 GPa. The observed phonon modes continuously shift to the higher energy side with increasing pressure below 6 GPa. However, it is found that the spectral profile of the phonon modes drastically changes around 6 GPa. From the analysis of the phonon modes using a Lorentz oscillator model, it is shown that the spectral changes correspond to a structural phase transition that occurs at 6 GPa.
The active control of cellular events is the key technology for progress in cell engineering. In this regard, the quantitative analysis of intracellular reactions and environments is important. Therefore, we designed an external force-responsive device with a cytocompatible surface structure, which consists of Fe3O4-encapsulated polymer nanoparticles covered with phospholipid polymer brush layers. In this paper, we report a method of fabricating Fe3O4-encapsulated core nanoparticles by a soap-free polymerization technique and present a suitable surface modification method to endow the nanoparticles with both cytocompatibility and cell internalization abilities. A delay time of 30 minutes between addition of the ionic monomer and addition of the Fe3O4 nanoparticle suspension is important for the encapsulation of the Fe3O4 nanoparticles into the polystyrene core nanoparticles. The poly(2-methacryoyloxylethyl trimethylammonium chloride (TMAEMA)-block-2-methacryloyloxyethyl phosphorylcholine (MPC)) (PTbM) brush layers on the magnetic core nanoparticles, fabricated by surface-initiated atom transfer radical polymerization, conferred cytocompatibility and cell internalization properties. The magnetic nanoparticles with PTbM chains showed cellular uptake but did not influence cell proliferation.
Rice hull, which is one of the agricultural wastes in Japan, is required to be reused as an industrial material. The rice hull silica carbon powder (RHSC powder), made from rice hull, is manufactured by mixing rice hull particles with phenol resin, and then carbonizing the mixture in nitrogen gas atmosphere at high temperatures. The RHSC powder is constituted by C and SiO2. Therefore, it has excellent water resistance and corrosion resistance. In addition, the RHSC powder has a porous structure unique to rice hull. One of the effective ways to utilize of the RHSC powder is the use as a filler for polymers and rubbers to improve the mechanical strength and electrical conductivity. In this study, focusing on the porous structure of the RHSC powder, improvement of adhesive strength was investigated by blending the adhesive with RHSC powder. By blending with the RHSC powder as the filler, adhesive strength was improved by an anchor effect. In addition, the experiments were carried out by changing the test conditions such as particle size and blending ratio of the adhesive. Since the improvement effect to destruction was elucidated, a wide range of applications to the wooden adhesive products are expected.
Recent studies by the authors have been intended to develop sintering additives that can make alumina sintered at low temperature with a small quantity. In the case of use of CuO-TiO2-Nb2O5-Ag2O type additives, high-density alumina was obtained by firing at a temperature of 900℃ or below, even though additives content was only 5mass%. In this study, co-firing of above materials with Ag-electrodes at 900℃ or below was examined in order to clarify the relationship between chemical compositions and their reactivity. The results showed that reactivity was highly affected by the Ag2O content in the sintering additives. When the content of Ag2O was higher, any disappearance of Ag-electrodes was not found and electric properties were almost the same as those of conventional LTCC materials. Finally, these results indicated the obtained materials had possibility to be applied to LTCC modules having high thermal conductivity.
Disinfecting effect on plasma generated by an atmospheric pressure dielectric barrier discharge, APDBD, was investigated to inactivate green mold spore, Penicillium digitatum, surviving on citrus fruit in an open environment. Aluminium electrode covered by dielectric silicon sheet from 0.05 mm to 5.0 mm in thickness was prepared as APDBD electrode, and plasma was generated on the surface of Citrus unshiu. As an optical emission of plasma, N2 second positive band indicates high intensity, and also O radical at 777 nm were observed as a dominant for the inactivation of P. digitatum spore. The green mold spore was inactivated sufficiently by APDBD plasma exposure in a few seconds without any damage on the surface of citrus, though thermal damage of citrus surface occurs when surface temperature increased over 65 degrees C after tens of seconds in irradiation period.
Naphthalene ring-fused 2-aminotryptanthrin (Naph-T2NH2) was synthesized as a fluorescent chemosensor for Al3+. We investigated the metal-ion recognition of Naph-T2NH2 through individual addition of Mg2+, Ca2+, Ba2+, Fe2+, Fe3+, Co2+, Ni2+, Cu2+, Ag+, Zn2+, Cd2+, Hg2+, Al3+, and Pb2+ in an acetonitrile solution. When Mg2+, Ca2+, Ba2+, Co2+, Ag+, Zn2+, and Cd2+ were individually added to the solution, the shape and intensity of the fluorescence spectra did not change. Conversely, when Fe2+, Fe3+, Ni2+, Cu2+, Hg2+, and Pb2+ were individually added to the solution, the fluorescence at 604 nm was quenched. However, the fluorescence at 494 nm increased significantly upon addition of Al3+. Thus, Naph-T2NH2 is well suited for use as a fluorescent chemosensor for Al3+.
The purpose of this study is to investigate the effects of the fiber unbundling on the mechanical properties of carbon fiber reinforced thermoplastic (CFRTP) fabricated using discontinuous carbon fibers and polypropylene. Tensile test and puncture impact test were performed using CFRTP of which the volume fractions (Vf) were 10, 20, and 30 %. The wet type of unbundling treatments, which applied the water flow with shearing forces, were given to carbon fiber bundles with 5 and 10 mm lengths. Tensile strength and puncture energy of CFRTP were improved by the effects of fiber unbundling in spite of the same Vf. The amount of strain at the maximum tensile stress also increased with the progress of fiber unbundling. The effects of fibers unbundling on mechanical properties were obtained even in the small-scale of unbundling treatments which still remained a certain amount of fiber bundles in CFRTP. However, it was difficult to obtain the effects of improving mechanical properties in the condition of high Vf using long fibers (10 mm) due to the occurrence of the deviation of fiber direction.
We report the effect of iron vacancies on the magnetic property of spin and charge ordered system YbFe2O4 single crystals. The excess amount of iron compensates for the evaporation of iron during crystal growth. We concluded that samples grown with the standard method contain iron vacancies of more than 10%. It is considered that increasing the iron in the starting material recovers the iron stoichiometry, and the proper magnetic property appears. With recovery of the chemical stoichiometry, the magnetic hysteresis loop changes from a double loop to a single loop, which indicates the development of spin coherence and the appearance of a large ferrimagnetic domain. The anomaly found in the thermomagnetization curve at approximately 150 K, the so-called TLT transition, disappears with better stoichiometry. This fact indicates that TLT is not a kind of phase transition but an effect of iron vacancy. Our discovery demonstrates that most of the crystals used in RFe2O4 research might contain many iron vacancies. The confused discussions on this material about the spin order model, the charge order model, and so on might reconsider such chemical stoichiometry, including iron vacancies.