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Zr2-xSnxSyP2O12-δwas prepared using a hydrothermal synthesis method, and its thermal expansion properties were evaluated. The solid solubility limit of Sn was found to be approximately x = 0.6, and the substitution of Sn influenced the formation of defects at S sites. All Sn-substituted Zr2-xSnxSyP2O12-δ samples had smaller coefficients of thermal expansion(αv) than Zr2SP2O12. The lowest αv value obtained was approximately −125 ppm/K for Zr1.8Sn0.2S0.9P2O12‐δ at 373–453 K. Rietveld analysis revealed that the values of polyhedral volume, bond angle variance, and quadratic elongation in the MO6 octahedron of Zr2-xSnxSyP2O12-δ were larger than those of Zr2SP2O12. From these results, it was suggested that the increase in distortion caused by S vacancies can lead to increase in the lattice volume and control of CTEs.

This paper reports on the effect of Ti substitution on the thermal expansion behavior of Zr2-xTixS0.9P2O12-δ. The solid solubility limit of Ti in Zr2-xTixS0.9P2O12-δ was approximately x = 0.7 and could be classified into two types of Zr2-xTixS0.9P2O12-δ: x = 0–0.38 and x = 0.46–0.7. The all-Ti-substituted Zr2-xTixS0.9P2O12-δ had a smaller lattice volume than Zr2S0.9P2O12-δ. Zr2-xTixS0.9P2O12-δ (x = 0–0.38) showed a similar thermal expansion behavior to Zr2S0.9P2O12-δ, but Zr2-xTixS0.9P2O12-δ (x = 0.46–0.70) was less deformable than Zr2-xTixS0.9P2O12-δ (x = 0–0.38). In other words, Ti has two effects: reduction of the lattice constant and inhibition of the phase transition. Zr1.62Ti0.38S0.9P2O12-δ had the smallest lattice volume among the chemical compositions with a dynamic phase transition and had the lowest αv value of −114 ppm/K at 393–453 K.

The demand for the fabrication of nanostructures consisting of metal and dielectric is increasing with the development of new plasmonic optics. Since 1997, the presenter has produced various dielectric nanostructures by the bottom-up method and reported their optical and electrochemical properties such as light propagation in two-dimensional polystyrene colloidal crystals[1], the electron emission of diamond nanorods arrays[2], photochemical micro beakers composed of TiO2[3], etc. The advantages of the bottom-up method are that you can easily try various materials in addition to being able to easily perform experiments at the laboratory level. In this presentation, we will report about the various nanostructures fabricated using thermal dewetting process of metal/dielectric interface[4], focusing on the application to the plasmonic color pigment and microfluid devices. 1 Chem. Commun. 2004, 506. 2 Chem. Lett. 2000, 29, 534. 3 Chem. Lett. 1997, 925. 4 Nanoscale Adv., 2020, 2, 2271.

Titanium-doped hydroxyapatite (Ti-HAp, (Ca10-2x, Tix, hx) (PO4)6(OH)2, h: defect in Ca site) and hydrox- yapatite (HAp, Ca10(PO4)6(OH)2) powders were modified with an ethanol solution of molybdenyl acety- lacetonate (MoO2(C5H8O2)2) using chemisorption calcination cycle (CCC) technique, which provides metal oxide clusters. Their photocatalytic activity under UV illumination was evaluated by the decompo- sition of gaseous 2-propanol. The photocatalytic activity of the Mo-modified Ti-HAp samples increased concomitantly with increasing Mo concentration up to 0.72% against P. The highest photocatalytic activ- ity of Mo-modified Ti-HAp was about 13 times higher than that of Ti-HAp. The signal appearance of Mo (V) in electron spin resonance spectra and the decrease of photoluminescence intensity suggest electron transfer from the Ti-hybridized band to the MoOx cluster, which suppresses recombination of the pho- toinduced electron and hole pairs. The photocatalytic activity of Mo-modified HAp samples was attribu- ted to HOMO–LUMO excitation of MoOx cluster.

Sensitized thermal cells (STCs) are a new green power generation system operated by heating without a cooling temperature part. Here, we suggest Ag2S-sensitized thermal cells working at a low temperature (below 200 °C) and have a stylish sheet form. TiO2 was used for the electron transport layer, and ferrocene/ferricinium ions dissolved in dimethyl sulfoxide was selected for the redox couple ions. The Ag2S STCs generated power under light irradiation and at 90 °C in the dark. Electrochemical measurements and ICP-MS (inductively coupled plasma–mass spectrometry) indicated that thermally excited carriers caused the redox reaction and power generation occurred with heating. This result is an example of the first STC where the semiconductor part is less than a micrometer in size, not only improving the volume density of STC but also showing the possibility of STC with design awareness including flexibility.

Titanium-doped hydroxyapatite (Ti-HAp, (Ca10-2x, Tix, □x) (PO4)6(OH)2, □: defect in Ca site) powders were modified with a CaMoO4 aqueous solution. Then their photocatalytic activity under UV illumination was evaluated by the decomposition of gaseous 2-propanol. The crystal structure, morphology, light absorption, and specific surface area were almost unchanged by the modification, but small clusters were deposited onto the Ti-HAp surface. The photocatalytic activity of the Mo-modified samples increased concomitantly with increasing Mo concentration until 0.5% against Ti. The highest photocatalytic activity of Mo-modified Ti-HAp was about nine times higher than that of Ti-HAp. Computer modeling revealed that the contribution of MoO42− doping into the Ti-HAp structure plays no important role in the activity increase. A Mo(V) signal appeared by UV illumination in electron spin resonance spectra of Mo-modified Ti-HAp. The Mo modification decreased the photoluminescence intensity. These results suggest that photoinduced electrons can transfer from the Ti-hybridized band to the cluster, thereby improving the carrier separation efficiency and engendering higher photocatalytic activity.

You can find thermal energy everywhere in the world, including geothermal energy. Here we report an amazing battery that could supply power semi-permanently by simply burying the cell in a heat source and turning the switch on and off. We examined the discharge termination process of a sensitized thermal cell (STC), a new thermal energy conversion system for generating electrical power from heat previously reported by the authors. To observe this termination process, we constructed a new STC system using a narrow-bandgap semiconductor, germanium (Ge), and surprisingly found that the battery characteristics were restored after discharging by placing or burying the battery in a heat source. This discovery should bring us closer to solving global energy problems.

Amorphous precursor was synthesized hydrothermally and heated to 900 °C for 4 h to obtain a single-phase Zr 2 (WO 4 )(PO 4 ) 2 crystal with a specific surface area of approximately 11 m 2 /g. The crystallographic parameters were experimentally estimated and the resulting approximate values used for density-functional-theory calculations. The indirect band-gap energy was calculated to be approximately 3.7 eV, in good agreement with the experimental value. Finally, the photocatalytic activity of Zr 2 (WO 4 )(PO 4 ) 2 was investigated that revealed its high adsorption capacity for 2-propanol, decomposing it into acetone and CO 2 .

Efficient and low-cost thermal energy-harvesting systems are needed to solve the global energy problem. Here, we suggest a new energy conversion system for generating electric power from heat without a cooling element. This device is a sensitized thermal cell (STC) based on a dye-sensitized solar cell. A semiconductor is used instead of the dye, and as a result, this system can work by using heat instead of light. To prove the efficacy of this system, we focused on an organic perovskite. This material has been used in a sensitized solar cell, and recent calculations show that it can generate several thermally excited charges at temperatures over 60 °C. Thus, if this perovskite cell can generate electric power with both light irradiation and thermal excitation, the STC concept would be perfectly proven, and the device succeeds thanks to the careful analysis of the perovskite’s unstableness. This is the dawn of the three-dimensional utilization of heat.

The effective utilisation of thermal energy is crucial to a world aiming at sustainable development goals. The sensitised thermal cell (STC) is a new thermal energy conversion technology, which was reported in 2017, for generating electricity via the redox reactions of electrolyte ions with thermally excited carriers The effective utilisation of thermal energy is crucial to a world aiming at sustainable development goals. The sensitised thermal cell (STC) is a new thermal energy conversion technology, which was reported in 2017, for generating electricity via the redox reactions of electrolyte ions with thermally excited carriers in semiconductors. STC is attracting attention as a technology that could affect oil prices globally. Here, we report the successful construction of STC, which discharges and recovers well at room temperature, by studying the interelectrode and ion diffusion distances. The fabricated STC is thinner than 0.5 mm and can be rendered flexible. Further, STCs, which possess a power generation capacity of 0.1 mA, 100 mV per 1 mm2 area, and shall be installed “in” internet-of-things (IoT) devices, drainage pipes, and walls in the future.in semiconductors. STC is attracting attention as a technology that could affect oil prices globally. Here, we report the successful construction of STC, which discharges and recovers well at room temperature, by studying the interelectrode and ion diffusion distances. The fabricated STC is thinner than 0.5 mm and can be rendered flexible. Further, STCs, which possess a power generation capacity of 0.1 mA, 100 mV per 1 mm2 area, and shall be installed “in” internet-of-things (IoT) devices, drainage pipes, and walls in the future.

The effective utilisation of thermal energy is crucial to a world aiming at sustainable development goals. The sensitised thermal cell (STC) is a new thermal energy conversion technology, which was reported in 2017, for generating electricity via the redox reactions of electrolyte ions with thermally excited carriers in semiconductors. STC is attracting attention as a technology that could affect oil prices globally. Here, we report the successful construction of STC, which discharges and recovers well at room temperature, by studying the interelectrode and ion diffusion distances. The fabricated STC is thinner than 0.5 mm and can be rendered flexible. Further, STCs, which possess a power generation capacity of 0.1 mA, 100 mV per 1 mm2 area, and shall be installed “in” internet-of-things (IoT) devices, drainage pipes, and walls in the future.

Graphical abstract, Two cerium molybdates (Ce2Mo3O12 and γ-Ce2Mo3O13) were prepared using either polymerizable complex method or hydrothermal process. The obtained powders were almost single-phase with different cerium valence. Both samples were found to have antiviral activity against bacteriophage Φ6. Especially, γ-Ce2Mo3O13 exhibited high antiviral activity against both bacteriophage Φ6 and SARS-CoV-2 coronavirus, which causes COVID-19. A synergetic effect of Ce and molybdate ion was inferred along with the specific surface area as key factors for antiviral activity.

Efficient and low-cost thermal energy-harvesting systems are needed to solve the global energy problem. Here, we suggest a new energy conversion system for generating electric power from heat without a cooling element. This device is a sensitized thermal cell (STC) based on a dye-sensitized solar cell. A semiconductor is used instead of the dye, and as a result, this system can work by using heat instead of by light. This STC was created that generates electricity by “placing” or “burying” the cell in a heat source. In this invited talk, we will present the latest results of the STC research.

We report a method to modulate spontaneously formed microwrinkle patterns on a metal-capped elastomer surface by introducing lithographic patterns (structures) on the original surface as spatial triggers for directed wrinkling. The lithographic patterns are designed to have approximately the same lateral length scales as the characteristic wavelength of the microwrinkles by utilizing self-assembled two-dimensional microsphere arrays with hexagonal packing as a lithographic mask. When the lateral periodicity of the lithographic pattern is close to the wavelength of wrinkles, a novel directional order originating from the hexagonal packing of microspheres is induced. Otherwise, the wrinkle crests tend to form along the small ridges of the lithographic structure. The compression direction-dependent and reversible ordering of wrinkle patterns by compressive strain is also found for patterns with directional order.

Efficient and low-cost thermal energy-harvesting systems are crucial to solve the global energy problem. A new energy conversion system for the generation of electric power directly from heat energy is described herein. The device is a sensitized thermal cell (STC) based on a dye-sensitized solar cell. In the established system, thermally-excited electrons in a semiconductor were utilized instead of photon-excited electrons in a dye. Consequently, the STC generated electricity by “placing” or “burying” the cell in the heat source. The present study summarized the recent results of the STC and the difference between photo excitation and thermally excitation.

Powders of cerium (Ce)-substituted and tungsten (W)-substituted La2Mo2O9 (LMO) were prepared using polymerizable complex method. Their antiviral and antibacterial performances were then evaluated using bacteriophage Qβ, bacteriophage Φ6, Escherichia coli, and Staphylococcus aureus. The obtained powders, which were almost single-phase, exhibited both antiviral and antibacterial properties. Effects of dissolved ions on their antiviral activity against bacteriophage Qβ were remarkable. A certain contribution of direct contact to the powder surface was also inferred along with the dissolved ion effect for antiviral activity against bacteriophage Φ6. Dissolved ion effects and pH values suggest that both Mo and W are in the form of polyacids. Antiviral activity against bacteriophage Φ6 was improved by substituting Ce for La in LMO. Similarly to LMO, Ce-substituted LMO exhibited hydrophobicity. Inactivation of alkaline phosphatase enzyme proteins was inferred as one mechanism of the antiviral and antibacterial activities of the obtained powders., Graphical abstract Unlabelled Image, Highlights • Ce and W were partially substituted in La2Mo2O9 (LMO). • These powders inactivated E. coli, S. aureus, bacteriophage Qβ, and bacteriophage Φ6. • Inactivation of alkaline phosphatase enzyme proteins on these materials was confirmed. • Antiviral activity against bacteriophage Φ6 of LMO was improved by substituting Ce. • Hydrophobicity and UV shielding performance were also confirmed for this material.

Plasmonic color is an elegant color resulting from light absorption and emission induced by collective oscillation of free electrons in a metal and enables unprecedented new color expression. In particular, Al plasmonic color is highly desirable because of the low cost and high stability of Al. Here, we report a new cost-effective, wide-area fabrication method for an Al metal–insulator–metal (MIM) plasmonic nanostructure using a vapor deposition and sintering process.

This paper proposes Kelvin probe force microscopy (KFM) as a new measurement method of plasmon phenomenon. The surface potential of two arrays, namely, a monomeric array and a tetrameric array, of gold nanodiscs (600 nm diameter) on a silicon substrate fabricated by electron beam lithography was investigated by KFM with the view point of irradiation light wavelength change. In terms of the value of the surface potential, contrasting behaviour, a negative shift in the monomeric disc array and a positive shift in the tetrameric disc array, was observed by light irradiation. This interesting behaviour is thought to be related to a difference in localised plasmons caused by the disc arrangement and was investigated from various viewpoints, including Rayleigh anomalies. Finally, this paper reveals that KFM is powerful not only to investigate the plasmonic behaviour but also to predict the electron transportation.

The relation between surface homogeneity and internal fluidity for a droplet sliding on a surface tilted at acute and obtuse angles was investigated using two hydrophobic fluoroalkylsilane (FAS) coatings with different roughness. The coatings (FAS-smooth and FAS-rough) were prepared on an Si substrate using chemical vapor deposition or soaking methods and were tilted at 35° or 145°. Sliding velocity of water droplets on the surface tilted at 145° was greater than that tilted at 35° for both coatings. For 35° tilting, the dominant mode of the sliding velocity was slipping for FAS-smooth, whereas rolling governed the entire sliding velocity for FAS-rough. The slipping mode was more important than the rolling one for both coatings when they were tilted at 145°. The change of slipping velocity was more remarkable than that of rolling one for both coatings between 35° and 145° tilting. Results show that the difference in gravity direction and contact area of the droplets contributed to this tilt angle dependence of the sliding velocity. When a droplet slid down with acceleration on FAS-smooth surface, the coefficient of the viscous drag force correlated with the velocity ratio (Utotal/Uslip).

Zinc oxide nanorods (ZnO-NR) were prepared on Zn plates with a ratchet structure by hydrothermal processing. Then the Leidenfrost phenomenon of the sample was evaluated after coating with fluoroalkyl silane. After formation of the ZnO-NR, the Leidenfrost temperature of Zn plates decreased by approximately 20 °C. The terminal velocity of self-propelled droplets on the plates depended on the temperature. The dominant mechanism for the self-propulsion of water droplets on Zn plates without ZnO-NR at 160–200 °C was nucleate boiling and resultant volume expansion, but it switched to gravity at temperatures higher than 200 °C. Because of suppressed adhesion of droplets onto the ratchet wall and because gravity appeared to be the dominant mechanism for droplet self-propulsion on the sample at all temperatures, both the temperature for self-propulsion and the self-propelled droplet velocity were lower after ZnO-NR modification onto the Zn plate surface. However, when ZnO-NR was formed onto every other ratchet, the self-propelled droplet velocity increased with lowered temperatures for self-propulsion. The estimated terminal velocity for the sample at 160 °C exceeded that for the Zn plate without ZnO-NR.

Plasmonic colour from metals has been recently attracting attention because it is less likely to deteriorate due to environmental change. However, metals such as silver easily react chemically with the atmosphere. Although plasmonic colour in various materials and structures has been assessed, the effects of chemical changes on plasmonic properties have not been deeply investigated. In this paper, we have evaluated the changes in optical properties and structure of silver plasmonic colour from the viewpoint of a phase diagram. As a result, we report remarkable colour changes and the formation of nanorings with a diameter of approximately 100 nm by vacuum ultraviolet light irradiation and heat annealing.

First-principles calculations predict that the cubic phase of methylammonium lead iodide (CH3NH3PbI3), a well-known perovskite material containing no rare metals, will show thermoelectric p...

Fibrous TiO2 layer was formed on a metal Ti plate by soaking it in a KOH solution and subsequently firing it in air at 600 °C for 2 h. Hydrophobic solid–liquid bulk composite (SLBC) was prepared by impregnation of a commercial silicone-based oil into the fibrous TiO2 layer after coating with fluoroalkylsilane. Based on the spreading coefficients from interface energies, the topmost solid surface of the SLBC was covered by the oil film when a water–glycerin mixture droplet was placed on the surface. The mixture droplets slid down the SLBC with acceleration. Particle image velocimetry (PIV) analysis revealed rolling and slipping modes in the sliding of the mixture droplets on the SLBC surface. During sliding, the coefficient of the viscous drag force was correlated with the velocity ratio (U total/U slip). Results suggest that the estimation of the internal fluidity of the liquid droplet was feasible to some degree by evaluating the coefficient during droplet sliding with constant acceleration on the SLBC surface.

This study introduces a new type of system for the conversion of heat into electric power that does not require a temperature difference. This system does not rely on the Seebeck effect, and it has a simple layer-by-layer design. It is a sensitized thermal cell based on a dye-sensitized solar cell. This cell uses phonons, which are quantum expressions of heat, instead of photons. The open voltage and short-circuit current of the prototype cell, which is composed of β-FeSi2 as a semiconductor material and a solid copper ion conductor, were confirmed above 300 °C. The acquisition voltage was increased for 5 hours and continuously maintained at this value for at least 35 h, which suggests that this system functioned successfully. These generators enable all semiconductor materials to be applied three-dimensionally as heat sources, for example, in geothermal power plants, by burying the generator in a geothermal source.

This study presents a synthetic method for preparing Zr2MoP2O12 powder and its sintered body using a solid-state reaction and a pressureless sintering method, respectively. The optimum heating sequence required to synthesize Zr2MoP2O12 was 873 K for 4 h, 1173 K for 2 h and 1323 K for 30 min. The specific surface area of the obtained powder was 4.2 m2/g. Several sintering additives were evaluated to obtain the Zr2MoP2O12 sintered body, and the most stable additive was 2 mass% ZnO, which yielded a relative density of >90% following sintering at 1173 K for 2 h. Young's modulus, Poisson's ratio, Vickers micro-hardness and fracture toughness of Zr2MoP2O12 sintered with 2 mass% ZnO were 81 GPa, 0.26, 3.1 GPa and 0.6 MPa · m1/2, respectively. Keywords: Ceramics, Oxides, Chemical synthesis, Mechanical properties, Thermal expansion

The new concept of thermally power generation system, a sensitized thermal cell (STC) based on a dye-sensitized solar cell, had been suggested. In this STC, thermally excited charge carriers in a semiconductor were used instead of photon excited charge carriers in a dye. In the previous repot, the β-FeSi2 used as the semiconductor included impurities and the battery characteristics was low. Here, to obtain high purity β-FeSi2, the combination method of arc melting and drop cast was used. As a result, the battery characteristics was improved. The present results show that the properties of the semiconductor contribute to the performance of the STC.

Hydrophobic porous glass plates were prepared by coating a fluorosilane (FAS17) onto a commercial porous glass (average pore size, approx. 1 μm). Based on the spreading coefficients from interface energies, we prepared solid–liquid bulk composites (SLBC) without direct contact between the solid surface and liquid droplet by impregnation of silicone oil into the silane-coated porous glass. Impregnating the oil into the porous glass decreased both the sliding angle (ca. 20° → ca. 5°) and contact angle (ca. 135° → ca. 100°). The sliding velocity of the liquid droplets on the SLBC decreased when the droplet viscosity was increased using a water–glycerin mixture. Analysis by particle image velocimetry revealed that increasing the viscosity remarkably decreases the slipping motion and increases the contribution of rolling. Results suggest that the practical internal fluidity of the droplets during sliding on the SLBC is governed by the combination of the droplet liquid and the oil impregnated into the porous media.

A tungsten-molybdenum solid solution oxide ((Mo,W)O3) powder was prepared using hydrothermal processing. The crystal structure of the obtained powder was orthorhombic WO3 type with 0.22 M H2O per unit chemical formula weight. This powder was dehydrated and transformed into monoclinic WO3 type structure by heat treatment at 500 °C in air. When uncalcined powder was modified with Cu by impregnation with a CuCl2 solution and subsequent firing at 500 °C in air, photocatalytic decomposition activity against gaseous 2-propanol (IPA) was achieved under visible light illumination. Results suggest that Cu(W1−xMox)O4 was formed on the (Mo,W)O3 powder surface by the Hedvall effect during its phase transition, and that the Z-scheme became feasible between (Mo,W)O3 and Cu(W1−xMox)O4.

Efficient and low-cost thermal energy-harvesting systems are crucial to solve the global energy problem. A new energy conversion system for the generation of electric power directly from heat energy is described herein. The device is a sensitized thermal cell (STC) based on a dye-sensitized solar cell. In the established system, thermally-excited electrons in a semiconductor were utilized instead of photon-excited electrons in a dye. Consequently, the STC generated electricity by “placing” or “burying” the cell in the heat source. To prove the concept, first, we examined the redox ability of thermally excited electrons (Mater. Horiz., 2017, 4, 649–656.). Next, we demonstrated that the semiconductor-sensitized solar cell can generate electric power by thermally excitation (ACS Applied Energy Materials, 2019, 2, 13–18.; J. Phys. Chem. C, 123, 2019, 12135-12141.). Lastly, we performed the long-time power generation at 80 degree using STC and observed the end; and surprisingly found that the battery characteristics were restored after discharging by placing or burying the battery in a heat source ( J. Mater. Chem. A, 2019, 7, 18249-18256.). Additinally, we show that the open circuit voltage of STC has the Fermi level dependnce of the semiconductor electrode (Chem. Lett. in press). In the presentation, these recent results were summarized and the difference between photo excitation and thermally excitation will be discussed..

Plasmon resonance endows gold (Au) nanostructure with extraordinary optical and thermal properties, which can be utilized in a wide range of areas. We determined that an Au film on simple SiO2 colloidal crystals can easily generate plasmonic photothermal synthesis. To demonstrate this, ZnO local synthesis was performed. This plasmonic photothermal synthesis of ZnO is safe, simple, and environmental friendly compared to the traditional synthesis of ZnO, which requires particular conditions and complex procedures. This method shows high synthesis controllability and flexibility, which provides a potential approach for microfabrication and modification.

We prepared transparent solid–liquid bulk composites by hybridizing porous silica with either an ionic liquid or a silicone oil, and investigated the reasons underlying the characteristic wetting behavior of the composite with the ionic liquid. The composite with the ionic liquid was hydrophilic, but it was immiscible in water, probably because of the hydrophobic effect. The contribution from the hydrogen bond component of the ionic liquid to the hydrophilicity was inferred from the division of surface energy components. The composite with the silicone oil was hydrophobic. Both composites exhibited small sliding angles and contact angle hysteresis on a water droplet. Spreading coefficients suggest that ionic liquid spreads at the water–solid interface in the composite. These properties simultaneously provide a water-shedding property and hydrophilicity on the composite with the ionic liquid. Both composites exhibited re-connection performance of the broken part with retention of their water shedding property.

Sensitized thermal cell (STC) is a new method for converting heat directly into electric power; STC mimics a dye-sensitized solar cell. Up to now, the power generation by STC has been reported for β-FeSi2, Ge, and Ag2S; however, these materials are relatively expensive. In this study, CuFeS2, which is abundant on the Earth, was examined as the STC material.

Titanium-substituted hydroxyapatite (Ti-HAp) is a potential photocatalyst with high adsorption capability for organic compounds. As described herein, the surface of Ti-HAp was modified by WOx. Photocatalytic decomposition activity on gaseous 2-propanol was increased by seven times by the modification. Little difference was obtained in the crystalline phase, specific surface area, and the light absorption edge between before and after the modification. However, photoluminescence emission intensity by UV irradiation was decreased by the modification. Results show that UV irradiation changed the valence number ratio of W cations under N2 atmosphere. Furthermore, first-principles simulations of molecular dynamics and electronic structure suggest that carrier separation is promoted by WOx clusters acting as a co-catalyst and suggest that those photoexcited electrons can be consumed by atmospheric oxygen. These experimental and theoretical investigations have demonstrated clearly that the photoexcited electrons can transfer from a Ti-hybridized band in Ti-HAp to WOx, thereby promoting charge separation.

It has been widely known that colloidal particles and their arrayed structures play a critical role in various fields because of their versatility. Based on an expectation that quadrupole microstructures would display unique optical characteristics, we focused on the fabrication process for quadrupole structures composed of colloidal particles. The quadrupole structures consisted of polystyrene particles (PSt) with a 1.0 μm diameter were formed by applying the integrated approach with a top-down method and a bottom-up method (i.e., template-assisted self-assembly). Microhole arrays with two different shapes—circular holes and square holes—were fabricated on a Si substrate by using electron beam lithography and reactive ion etching. These top-down processes were followed by a bottom-up process that the Si substrate with fabricated microhole arrays was withdrawn from a PSt aqueous solution. With the microhole arrays as a guide, the PSt particles were forced to array the specific structures in the microholes due to the capillary force and Van der Waals force acting on the particles and substrate. By controlling the solvent drying process, the yield of quadrupole structure was reached approximately 80% in over 300 microholes. Additionally, the distance between two neighboring particles consisting of quadrupole structures could be controlled by the sizes of the microholes, and the obtained particle configurations could be removed onto an adhesive tape.

Photoelectrochemical applications of photonic crystals are gathering great interests both from physicists and chemists. Here, we theoretically and experimentally present two-dimensional photonic bandgap (2D-PBG) structures based on rutile titanium dioxide (TiO2) single crystal that is a famous material because of the photoelectrochemical ability. The structures were the arrays of hollow hexagonal rutile TiO2 pillars in contact with air or a typical nonaqueous electrolyte solution, acetonitrile. Since the TiO2 refractive indices exhibit a strong dispersive behavior, the bandgap width was discussed from the viewpoint of the refractive index map that would be helpful for the real application of this structure. The 2D-PBG structures for both infrared light and visible light were fabricated by our established lithography technique for rutile TiO2 with and without Nb doping, i.e., photocatalytic TiO2 and high electron conductive TiO2, respectively. These structures show characteristic absorbance peaks or reflectance dips at wavelengths predicted by our theoretical calculations.