Monodispersed VO2-SiO2 nanohybrid particles were obtained by reducing V2O5-SiO2 nanohybrid particles. V2O5-SiO2 nanohybrid particles were prepared by coating a nanolayer of V2O5 onto monodispersed SiO2 particles from modified vanadium alkoxide and monodispersed SiO2 particles mixture sol, followed by the annealing at 350℃ for 2 h in air. As a result, monodispersed SiO2 particles were effectively coated by using acetic acid anhydride as a chelating reagent, and VO2-SiO2 monodispersed nanohybrid particles were successfully prepared by annealing the V2O5-SiO2 nanohybrid particles up to 500℃ for 2h in H2/Ar atmosphere. EPMA analysis also exhibited the uniform vanadium distribution on the monodispersed SiO2 particles, showing the homogeneous coating of VO2 nanolayer onto the monodispersed SiO2 particles.
Purpose: For gene therapy, development of non-viral vectors delivered more efficiently and safely into cell has long been awaited. We have successfully prepared poly (D,L-lactide-glycolide) nanospheres (PLGA NSs) for peptide delivery to improve drug absorption through the mucous membrane by modifying the surface of NSs with chitosan. The aim of this study is to establish the preparation method of pDNA loading PLGA NSs to improve loading efficiency and to enhance their cellular uptake and gene expression.
Methods: pDNA (pCMV-Luciferase) loaded PLGA NSs were prepared by emulsion solvent diffusion method. For the preparation of chitosan coated PLGA NSs (CS-PLGA NSs), chitosan-PVA mixed solution was used as the dispersing phase during evaporation process. Particle size and zeta potential of NSs were measured by a laser scattering method and zeta master (Zetasizer 3000HS, Malvern Inc.). pDNA loading efficiency into NS and release behavior of pDNA from NSs were investigated. In vitro transfection tests were performed with human lung adenocarcinoma cells (A549 cells) by luciferase assay system. In vitro cellular uptake tests of NS were performed with A549 cells by using 6-coumarin labeled NSs.
Results: The particle size of NSs was c.a. 250nm. Plasmid DNA could be dispersed in polymeric organic solution. Loading efficiency into nanosphere was increased by forming ion complex with cationic material (DOTAP or chitosan). CS-PLGA NSs had a positive charge, while PLGA NSs being negatively charged, suggesting that the NSs were coated successfully with chitosan. pDNA loading efficiency was increased by coating with chitosan. CS-PLGA NSs showed higher cellular uptake of NSs with A549 cells than uncoated NSs. The transfection efficiency of CS-PLGA NSs was higher than PLGA NSs. This result might be caused by higher cellular uptake ability of CS-PLGA NSs due to electrostatic interaction.
Recently, it has become easy to obtain medication without regular hospital visits as out-patients or previous hospitalization. This is mainly due to the development of the drug delivery system (DDS). However, to cope with the aging society in Japan, further investigation is necessary to establish a highly effective DDS. Against this background, an important project is to develop new materials which constitute such medication. Mesoporous silicas, which possess uniform pores to incorporate medicines are noted as new materials in a wide range of research fields. In this context, I have studied development of a photo-triggered drug release system with mesoporous silica through photo-decarboxylation.
The effect of particle addition on the de-wetting at a liquid/liquid interface was observed by optical microscopy. Evaporative organic solvent film was coated on an immiscible silicone oil to form two-layer thin liquid coatings. As the solvent evaporates, the solvent film became thinner, spontaneously ruptured and promoted the de-wetting at the solvent/oil interface. The spherical silica particles with a diameter of 5.4 microns were dispersed in the upper solvent layer at a particular range of particle concentrations. The experimental results revealed that the onset time of de-wetting significantly increases as increasing particle concentrations in the upper liquid layer, i.e., the liquid layer was stabilized by the particle addition. In contrast to the suppressed de-wetting in a single dispersion layer (Barnes, 2000), the suppression in our two liquid layers was induced by slower growth of fluctuation at the liquid/liquid interface, rather than the meniscus self-pinning at particle/liquid/solid interface.
Oscillatory zoning of solid solution of (Ba,Sr)SO4 was investigated in gelatin. Then, Ba2+ and Sr2+ diffused into gelatin, and SO42- also diffused from opposite side. Periodic change of molar ratio Ba2+/Sr2+, which was firstly found out by Putnis et al. (1992) in silica gel, was well reproduced. However, we were able to obtain fine-structured particles which are quite different from those in silica gel. We investigated effects of gelation time and gelatin concentration on the structure and chemical inhomogeneity of particles. Experiments with 16% and 24%-gelatin gave results that core portion of solid solution was composed of BaSO4, which was different from the results in silica gel. Furthermore, we were able to make various kinds of particles with novel structures by controlling gelation time and gelatin concentration. For example, different structures of particles were successfully formed in separated zone in gelatin. As another, white turbid zones containing particles were clearly separated by a transparent gel. These particles were formed spontaneously without special operations. This was achieved by a reaction-diffusion mechanism. Gelation time and gelatin concentration controlled the diffusion rate mainly, which induced dramatic change in particle growth process in gel. On the basis of these findings, we discussed the mechanism of particle growth in this system.
γ-NaxCo2O4 is well known as a candidate of high performance thermoelectric materials. γ-NaxCo2O4-Ag composite was obtained by sintering the powders prepared by the citric acid complex (CAC) method. The observation by the scanning electron microscope (SEM) indicated that in this composite fine Ag particles were dispersed in NaxCo2O4 matrix. The addition of Ag was effective for the reduction of the electrical resistivity (ρ) of γ-NaxCo2O4. The composite with small amounts of Ag shows moderate Seebeck coefficient(S)and thermal conductivity (κ), but with increasing Ag content they became unfavorable values to the thermoelectric performance. The maximum ZT(=S2T/(ρ×κ)) of 1.22 was obtained at 950K in the sample with 10 wt.% Ag. We have also consolidated NaxCo2O4 powders by the hydrothermal hot-pressing (HHP) technique. The measurement by the X-ray diffraction and the observation by SEM indicated that the sintered NaxCo2O4 ceramics with the plate-like grains aligned along the pressed plane can be obtained, and the larger pressing pressure and higher treating temperature in the HHP process are favorable to obtaining the samples with high orientation. The relative density of the samples also increases with increasing pressure and temperature in the HHP process. The Seebeck coefficient and electrical resistivity of the samples treated by HHP are generally smaller than those of the sample untreated by HHP. As a result, the power factor (S2/ρ) of the sample treated by HHP under 523K and 200MPa is slightly larger than that of the sample untreated by HHP.
While the wettability of solid surfaces and pores (adsorption and capillary condensation) is relatively well understood, the force between wetted bodies is still largely elusive. Detailed understanding and exact description of the force between solid surfaces both in vacuum or dry air and in capillary condensed fluids have been a central subject not only in colloid and interface science, but also particle technology and tribology. Deep knowledge of the adhesion phenomena is important, from an industrial point of view, in the process of particulate products such as ceramics, catalysis, and pharmaceuticals, in the manipulation of microdevices and micromachines, and in many operations (e.g., particle filter, fluidized bed, and painting and particulate coating).
In this study, the wettability of solid surfaces and the surface force were investigated computationally by Monte Carlo (MC) and Lattice Boltzmann (LB) simulations and experimentally by atomic force microscopy (AFM).
Phase transformation processes and thermal stability of nanocrystalline microstructures in TiAlbased alloy powders have been studied. Ti50Al45Mo5(at.%) alloy powders prepared by a plasma rotating electrode process were ball-milled for 96 h. The as-milled powders are composed of nanocrystalline grains of α(hcp-A3) or β(bcc-A2) phase smaller than 50 nm in diameter. In very early stages of annealing at 873-1373 K, the milled powders transform into an equilibrium three-phase state of α2(D019)+ β2(B2)+γ(L10), followed by the formation of the γ phase from the α (or α2) phase. The annealed powders have an equiaxed grain structure and exhibit a small increase in grain size after the heat treatment. This result indicates that the coexistence of fine α2, β2 and γ grains with the different crystal structures and compositions significantly retards the grain coarsening in the annealing processes.
Micro molding in capillaries (MIMIC) is promising a bottom up approach to fabricate micropattern using nano-sized ceramic particles. In this report, we have recently achieved two techniques for MIMIC process. One is a replication of PDMS micro-mold without using a master mold made of silicone wafer. The technique provides cost effective PDMS molds using duplicated from polymer master molds. The other is a new MIMIC technique to fabricate ceramic striped pattern with nano particles assisted by infiltrative liquid. For example, striped patterns with lines of 10μm in width were constructed using about 30 nm SnO2. The line length of the patters reached up to 2 mm by infiltrating the step of 5 times repeat. This new idea improved the issues in fabricating ceramic patterns with long length in conventional MIMIC process. At the moment, we are making master molds made of silicone wafer using lithography technique. We will promote the investigation on MIMIC process for nano-sized particles suspension in a comprehensive and systematic fashion.
Solid lubricants, such as molybdenum disulfide (MoS2), gold, silver or polytetrafluoroethylene (PTFE) are often used on the sliding parts exposed in the space environment. When MoS2 powder is mixed in the working oil, MoS2 layer can be deposited on stainless steel during the finishing electrical discharge machining (EDM) process. The deposition process must be clear to improve the endurance of the lubricant layer. When the electric field was applied between the electrodes, MoS2 powder reciprocated. Eventually, the powder was concentrated on the positive electrode side. Therefore, the positive polarity is preferable for the tool electrode. Then, the influence of the working oil flow was investigated by rotating a copper disk electrode. MoS2 was observed on steel under all conditions. The reciprocating friction test in air was carried out to investigate the influence of machining time and measured point of the deposited layer. The lubrication duration was decreased with an increase of the rotation speed of the electrode. Because the lubrication duration was saturated over 30 min, the deposited MoS2 was removed during deposition in the case of machining for a long time. The influence of the thermal properties of the specimen was also investigated. MoS2 could be deposited on the metals with lower melting point than MoS2.
The technology to assemble particles as a method of the technique for making material in recent years attracts attention. The particle assembly technology is the technique to fabricate a new functional material and device by assembling two or three dimensional periodic structures with particles such as metals, oxides, and polymers.
It is expected that the material which has a multifunction and an intelligent function in the future can be made by assembling the particle with various functions arbitrarily.
The purpose of this study is a new technical development of the particle array with the capillary electro-osmosis used for the microanalysis method. We would like to apply the capillary electroosmosis, which is actively researched in the field of chemical analysis, as a new technology for making materials. The under mentioned merit exists when this method is applied to the material processing. An indispensable device is only a power supply. It is easy to control a quantitative particle transport which uses the electro-osmotic flow by setting an electric experiment condition. The particle can also be arranged to the non-conducting material because the electro-osmotic flow is used. The composition of the cathode or anode side solution can be changed arbitrarily and independently. This is one of methods with which the contradicted requirement of dispersion and the flocculation is satisfied at the same time. Chemical or physical condition that the particle coheres can be set on the solution side which the particle extracts. On the other hand, the condition of dispersing particles can be set on the solution side where the particle is supplied. In this paper, the particle was arranged at an arbitrary position on the substrate by using the advantages of the capillary electroosmotic methods; especially an indispensable condition to achieve a minute array was investigated.
A newly-developed method permits an electric plasma discharge to occur with relatively low electric power in insulating organic solutions due to the presence of an ultrasonic cavitation. A stable electric plasma could be generated in an ultrasonic cavitation field containing a thousand tiny activated bubbles, in which the electric conductivity could be improved due to formed radicals and free electrons, using copper electrodes and a titanium ultrasonic horn. This method allowed us to synthesize pyrolytic amorphous carbon nanoparticles smaller than about 30 nm in diameter from benzene liquid. In addition, we synthesized TiC nanoparticles about 50‒150 nm in size, and copper nanoparticles smaller than 10 nm, which were encapsulated in multilayered graphite cages. Finally, we used GC‒MS and MALDI-TOF-MS to observe and analyze the polymerized compounds and the degree of polymerization of the benzene liquid after the plasma treatment.
We have developed a new production process for food-starch granules structured with surface coating. This process consists of two ideas, modifying with food materials and under the dry condition keeping with starch powder. We investigated the utilization of gellan-gum as a food material and the application of Agro Master (manufactured by Hosokawa Micron Corporation) as a dry-modifying machine. The surface microstructures of the modified starches were observed under an atomic force microscopy (AFM) to analyze the coating of starch granules. The starch surface treated with gellan-gum was a smooth structure and not the same as native starch surface, which showed a rough protruding structure, 5-20 nm height and 50̶150 nm diameter. The gelatinization properties of the starch treated with gellan-gum and then Ca-cation were analyzed. The swelling power and the soluble-sugar value were decreased with modifying combination of gellan-gum and then Ca-cation. These results indicate that the starch modified by structuring with surface coating shows the lower swelling and solubility of the granule during gelatinization.
Two-dimensionally dispersed L10-FePt nanoparticles as small as 12nm with orientation was fabricated by electron-beam evaporation and post-deposition annealing at 873K. After a prolonged annealing at 873K for 86.4ks, the increase of coercivity was almost saturated and coercivity reached 5.5kOe at 300K, which is very small compared to the values reported on FePt nanoparticles with larger particle sizes. Long-range order parameter of the fabricated nanoparticles was determined by electron diffraction at 200kV taking the multiple scattering into consideration. Obtained order parameter remained 0.55 for the nanoparticles with an axial ratio c/a of 0.961 ± 0.003. The low degree of order is thought to be responsible for the small coercivity in spite of the long-time annealing as high a temperature as 873 K. In order to enhance the L10 phase formation under the lower annealing temperature, effect of Cu addition on the atomic ordering of FePt nanoparticles were examined. As a result, a low temperature synthesis of isolated and oriented L10-FePtCu nanoparticles with high-density dispersion has been achieved by conventional rf-magnetron sputtering technique with a single crystal NaCl substrate. Hard magnetic L10-type ordered phase with a coercivity of about 1.4 kOe was directly formed at low substrate temperature as low as 613 K without any post-deposition annealing. Hard magnetic properties were sensitive to Pt concentration. It is considered that additive Cu replaces the Fe-site in the L10-FePtCu phase.
Strong electron localization in ionic crystal has hindered their application to the electrochemical devices as lithium batteries. However, recent advances in nano-composite formation with conductive phase have opened the door to examine hitherto-unexplored materials as electrode applications. Lithium iron phosphate, LiFePO4 is a good example of this. As a result of some screening of fluolides, oxyfluolides, and silicates, Li2MnSiO4 and Li2CoSiO4 were found to show electrochemical activities for reversible lithium intercalation.
Preparation of monodisperse inorganic-organic hybrid particles and their periodic arrangement on substrates are very attractive research topics in recent years. In this study, phenylsilsesquioxane (PhSiO3/2) and phenylsilsesquioxane-titania (PhSiO3/2-TiO2) particles were synthesized by the solgel process from phenyltriethoxysilane and titanium tetra-n-butoxide. Monodisperse, spherical PhSiO3/2 and PhSiO3/2-TiO2 particles were obtainable by varying the mole ratios of ethanol as solivent, hydrochloric acid for hydrolysis and ammonia water for polycondensation. PhSiO3/2 particles softened and sintered by a heat treatment at higher temperatures than the glass transition temperature at around 150℃ . FT-IR spectra showed that PhSiO3/2 and TiO2 components were homogeneously hybridized in the PhSiO3/2-TiO2 particles through Si-O-Ti bonds. The refractive index of the particles was monotonically increased from 1.57 to 1.62 with an increase in TiO2 content. The PhSiO3/2-TiO2 particles were electrophoretically deposited on indium tin oxide (ITO)-coated glass substrates to form opaque, thick films. The deposited 95PhSiO3/2·5TiO2 films became transparent with a heat treatment at 400℃ because of the thermal sintering of the particles.
Pregrooved substrates were useful to linearly array the monodisperse particles on the pregrooves in a short time, which was achieved by the ascending liquid flow on the substrate and the attractive capillary force between the particles. SiO2 microparticles were successfully closed-packed by sandwiching the colloidal suspension between the barriers using a newly developed setup for particle arrangement. PhSiO3/2 particles were selectively deposited onto the hydrophilic areas of the hydrophobic-hydrophilic patterned ITO substrates by electrophoresis. The films composed of aggregates of PhSiO3/2 particles became transparent with morphological changes from aggregates of particles to a continuous phase after a heat treatment. After the heat treatment at 200℃ , convexly shaped PhSiO3/2 micropatterns were formed on the hydrophilic region of the pattern. These patterning techniques have a wide variety of applications such as fabrication of micro-optical components.
Photonic crystals having a three dimensional periodic structure have attracted much attention from both fundamental and practical points of view, because of their unique properties in controlling the propagation of light. One of the promising techniques for fabricating three-dimensional photonic crystals is preparation of self-assembled colloidal crystal. In this study, we prepared two kinds of colloidal crystalline systems having photochemically patterning ability and investigated their patterning properties: one is colloidal spheres containing cinnamic moieties, and the other is silica colloidal crystals containing photocurable resin. The photochemically patterning ability was identified for both systems.
A powder-supplying device using the bending vibration mode of a piezoelectric disk with a twostep cylindrical projection at its center is described. The device has simple structure by which powder on the surface of the vibrator flows out the tip of the projection. Two degeneration modes of B11 vibration of the disk were considered.
The structure of the vibrator and the vibration mode by FEM are shown. Two kinds of powder were tested in the study, one is fly-ash (Dp50=15μm), the others are several kinds of white fused alumina and their powder-supplying characteristics were measured. The results show that the device can supply the powder composed of its particle size smaller than the size of 10 μm at flow rate of less than 1mg/s.
Hybrid nanoassemblies with metal nanoparticle monolayer and polymer nanosheets containing ruthenium (II) tris(2,2’-bipyridine) derivative (Ru(bpy)32+) were fabricated by the Langmuir-Blodgett technique and immersion method. Metal nanoparticles, gold and silver nanoparticles, were immobilized onto polymer Langmuir-Blodgett films containing amino end group (p(DDA/DADOO)) through immersion into a metal nanoparticle aqueous solution. This allows monolayer formation of metal nanoparticles which were uniformly distributed on polymer LB films. Emission intensity from the ruthenium complex was enhanced approximately four-fold in the presence of silver nanoparticles. Besides effective photocurrent generation was achieved by p(DDA/Ru)-Ag hybrid assembly system. Localized surface plasmon of the silver nanoparticle effectively excites ruthenium complex, while the excited ruthenium complexes were quenched by gold nanoparticles. This is due to the spectroscopic properties of metal nanoparticles immobilized on the polymer LB films; strong absorption band of silver nanoparticle arrays were overlapped with absorption band of ruthenium complex, and that of gold nanoparticle arrays were superimposed on the emission band of ruthenium complex. These findings suggest that spectroscopic optimization for the combination of photo- and electro-functional molecules and metal nanoparticles are of important in order to utilize localized surface plasmon electromagnetic field more efficiently.
We prepared nano-crystalline Zn-containing hydroxyapatite (ZnHAp) by the wet-chemical method and examined the selective adsorption of essential proteins, taking bovine serum albumin (BSA) and pathogenic protein such as β2-microglobulin ( β2-MG) as model proteins. Transmission electron microscopy observation and X-Ray diffraction analysis indicated that the increase of Zn content led to smaller crystallites and their specific surface area of ZnHAps increased with increasing the Zn content. Furthermore, the amounts of BSA adsorption on ZnHAp particles decreased with increasing the Zn content in spite of the increase in the specific surface area. It is thus concluded that nano-crystalline ZnHAps had a high selective adsorption property in regard to β2-MG.
A new SiC coating method on multi-walled carbon nanotubes has been developed by using the reaction between SiO vapor and carbon at 1250℃～ 1450℃ in vacuum. The growth mechanism of SiC layer was clarified. The SiC coating improved significantly the oxidation resistance of carbon nanotubes. SiC-coated carbon nanotubes were applied as reinforcements to wear resistant materials. Dense SiC-coated carbon nanotubes reinforced SiC composites were successfully fabricated by spark plasma sintering. These composites showed superior mechanical properties.
In order to fabricate dense yttria-stabilized zirconia (YSZ) electrolyte films supported by NiO-YSZ anode substrates, electrophoretic deposition (EPD) was used. For the EPD, graphite films with thickness below 1μm were pre-coated on the surface of a non-conducting porous NiO-YSZ composite substrate. YSZ green films were formed in quality on the reverse sides, which did not have the graphite layers. The green films were transformed into dense bodies with thickness of 5-10μm after being co-fired with the substrates. A single cell was constructed on the ca. 5μm thick dense YSZ films supported on the anode substrates. In the single cell, La(Sr)Co(Fe)O3 was used as the cathode. It was observed that maximum output densities of ～0.19, ～0.61 and ～1.02 W/cm2 were attained at 600, 700 and 800 ℃ , respectively.