[en] Highlights: • Red-emitting BaWO_4:Eu phosphors were prepared in hexane-water bilayer system. • The hydrophobic nanometer-sized BaWO_4:Eu phosphors were obtained in hexane. • The hydrophilic micrometer-sized BaWO_4:Eu dendrites were obtained in water. - Abstract: BaWO_4:Eu phosphors were prepared by performing a solvothermal reaction in a water–hexane bilayer system. A barium oleate (and europium oleate) complex was obtained in hexane via a phase transfer reaction involving Ba"2"+ (and Eu"3"+) ions in an aqueous solution of sodium oleate. The outer surfaces of the nanometer-sized BaWO_4:Eu phosphors were capped by the long alkyl chain of oleate; therefore, the hydrophobic nanometer-sized BaWO_4:Eu phosphors preferentially dissolved in the hexane layer. The micrometer-sized BaWO_4:Eu phosphors were obtained in the water layer. The BaWO_4:Eu phosphors prepared in hexane and water yielded sharp strong absorption and emission peaks at 464 and 615 nm, respectively, due to the "7F_0 → "5D_2 and the "5D_0 →"7 F_2 transitions of the Eu"3"+ ions. The BaWO_4:Eu phosphors are good candidate red-emitting phosphors for use in InGaN blue-emitting diodes, which have an emission wavelength of 465 nm.

[en] We have developed a simple method for tuning the morphologies of Cu_2O microcrystals. Cu_2O microcrystals were prepared by precipitation at room temperature from a mixture of Cu(CH_3COO)_2·H_2O, N,N,N',N'- tetramethyl ethylenediamine (TMEDA), ascorbic acid, and polyethylene glycol (PEG). TMEDA was used to promote the formation of copper-TMEDA complexes. A variety of Cu_2O microcrystal morphologies were obtained simply by varying the concentrations of TMEDA and ascorbic acid. Aggregated Cu_2O microspheres are formed at higher concentrations of ascorbic acid in the absence of TMEDA. Aggregated Cu_2O microcubes are formed at lower concentrations of ascorbic acid and higher concentrations of TMEDA. The crystal growth mechanism of these Cu_2O morphologies is explained

[en] Well-crystallized SrMoO₄ products with various shapes were synthesized by a simple method of precipitation and microemulsion using an anionic surfactant AOT microemulsion. The resulting SrMoO₄ crystals exhibited wire-, haystack-, peanut-, dumbbell-, and notched sphere-like shapes. With increasing AOT concentration, the morphology of the SrMoO₄ crystals evolved from wires, through haystacks and dumbbells, to notched spheres with higher hierarchy, and from rod- and peanut-like shapes to notched spheres with increasing Sr²⁺ and MoO₄^2- ion concentrations, in a simple precipitation reaction. This morphological evolution of the SrMoO₄ crystals was attributed to an oriented attachment. The fabrication of hierarchical inorganic microstructures has attracted great interest because of their unique, shape-dependent properties and applications. In general, hierarchical microstructures have been synthesized by using template precursors such as surfactant micelles, copolymer aggregates, and microemulsion droplets. SrMoO₄ is an important optical material that is widely used in Raman converters and solid-state lasers. However, only a few groups have examined synthetic methods for the fabrication of assembled SrMoO₄ structures. SrMoO₄ nanorods were synthesized via a hydrothermal reaction.12 Various shapes of SrMoO₄ were prepared by a simple alkaline aqueous mineralization method. Hierarchical, three-dimensional structures of SrMoO₄ have been prepared with microemulsion methods. In this paper, we report the morphological evolution of SrMoO₄ crystals obtained using reverse microemulsion with sodium bis(2-ethylhexyl) sulfosuccinate (NaAOT) surfactant. The morphological evolution of the SrMoO₄ crystals obtained by a simple precipitation method without any surfactants or templates was also examined

[en] The InOOH and In(OH)₃ products were selectively synthesized through a hydrothermal reaction while adjusting the amount of water. h-In₂O₃ and c-In₂O₃ products were selectively prepared through the thermal oxidation of the InOOH and In(OH)₃ products, respectively, as precursors. The morphology of the InOOH, In(OH)₃, h-In₂O₃, and c-In₂O₃ products were examined. The photocatalytic activities of h-In₂O₃ and c-In₂O₃ were better than commercial In₂O₃. Deethylation was observed during the photodegradation of RhB in the presence of h-In₂O₃ or c-In₂O₃. Indium oxide (In₂O₃) is an important semiconductor with a wide band-gap of 3.6 eV that has been widely used in solar cells, gas sensors, optoelectronics, and photocatalysis. Many efforts have been devoted to the synthesis of In₂O₃ with various morphologies, such as nanocubes, nanotubes, nanotowers, nano-rods, and hollow spheres. In₂O₃ has two phases of hexagonal In₂O₃ (h-In₂O₃) and cubic In₂O₃ (c-In₂O₃).14,15 Most of the synthetic methods have focused on preparing one of the two In₂O₃ phases. However, relatively little is known about the controlled synthetic method for the two specific phases of In₂O₃ that is carried out by adjusting the synthetic conditions. In this study, simple methods were reported for the production of InOOH and In(OH)₃ using hydrothermal reactions in aqueous solutions containing InCl₃, ethylenediamine (EDA), and N,N,N',N'-tetra-ethylethylenediamine (TEEDA). The selective formation of InOOH or In(OH)₃ was controlled by varying the amount of water. h-In₂O₃ and c-In₂O₃ were also selectively synthesized through the thermal oxidation of the InOOH and In(OH)₃ products, respectively as precursors. The photocatalytic properties of the h-In₂O₃ and c-In₂O₃ products that were fabricated this work were also examined

[en] Sr_1_-_xCa_xS:Eu (x = 0, 0.2, 0.4, 0.6, 0.8, 1) phosphors were prepared from CaS, SrS, and EuS via a solid-state reaction in air. The cathodoluminescence (CL) spectra of the Sr_1_-_xCa_xS:Eu phosph ors for the moderate voltage ranging from 4 to 10 kV were obtained to test their usefulness in field emission displays (FEDs). The maximum wavelength of the CL spectra of the Sr_1_-_xCa_xS:Eu phosphors increases from 629 to 668 nm as the mole fraction of calcium increases up to x = 0.8, and then decreases to 663 nm at x = 1. The relationship between the CL spectra and crystal structures of the Sr_1_-_xCa_xS:Eu phosphors was determined.

[en] Commercial micron-sized MVO₄:Eu phosphors are generally prepared by high-temperature solid-state reactions. However, these micron-sized phosphors cannot be used in flexible and transparent displays due to their high scattering. Because nano-sized materials do not show any scattering in the visible region, inorganic nanophosphors have received much attention for their applicability in flexible and transparent display devices. MVO₄:Eu nanophosphors have been prepared by soft reactions, such as hydrothermal, solvothermal, sonochemical, microemulsion, and polymer-assisted methods. Despite there have been numerous studies of the synthesis of MVO₄:Eu nanophosphors, most attention has focused on the synthesis of powder-type MVO₄:Eu phosphors. Monodispersed nanophosphors prepared by soft reactions can easily agglomerate in organic solvents. Transparent suspensions of nanophosphors without an agglomeration in organic solvents are needed for these phosphors to be used in flexible and transparent displays. However, there are few reports of preparing transparent suspensions of nanophosphors. Transparent suspensions of small amounts of YVO₄:Eu nanophosphors in hexane have been prepared using surfactant-assisted hydrothermal reactions in a water-hexane bilayer system. In this system, most of the YVO₄:Eu nanophosphors aggregated in the water phase that is not adequate for the flexible and transparent displays. New methods for the large-scale synthesis of nanophosphors are required that can prepare phosphors in single organic solvent phase. This work reports the first simple method of preparing transparent suspensions of GdVO₄:Eu nanopho-sphors in toluene. The optimal conditions for the phosphors' bright emission were also examined

[en] Zn_(_1_-_x_)Ga_2S_4:xEu (x = 0.03, 0.06, 0.09, 0.12, 0.15, 0.25, 0.50, 0.75, 1.0) phosphors were synthesized by performing a solid-state reaction. ZnGa_2S_4:Eu and EuGa_2S_4 crystal structures were confirmed by the XRD data. The photoluminescence (PL) spectra of the Zn_(_1_-_x_)Ga_2S_4:xEu phosphors were examined. Zn_(_1_-_x_)Ga_2S_4:xEu phosphor had a strong absorption near 465 nm, which was equal to the emission wavelength of the commercial blue-emitting diode. Zn_(_1_-_x_)Ga_2S_4:xEu phosphor produced a single emission band between 520 and 580 nm. The feasibility of Zn_(_1_-_x_)Ga_2S_4:xEu as a green-emitting phosphor pumped by the blue-emitting diode was investigated. A three-band white emission was obtained by coating a mixture of Zn_(_1_-_x_)Ga_2S_4:xEu and CaS:Eu phosphors onto the surface of a blue-emitting diode

[en] Morphology-controlled synthesis of cuprous oxide (Cu_2O) microcrystal was achieved using a solvothermal method. The morphologies of the Cu_2O microcrystals, namely octahedral, truncated octahedral, truncated rhombic dodecahedral, and rhombic dodecahedral, were fine-tuned by varying the oleylamine and sodium oleate concentrations. Only the {111} and {110} facets of the Cu_2O microcrystals were involved in this morphological transition. Octahedral Cu_2O microcrystals were obtained in the absence of oleylamine and at the highest sodium oleate concentration. Rhombic dodecahedral Cu_2O microcrystals were obtained at the highest oleylamine concentration or at the lowest sodium oleate concentration. The rhombic dodecahedron, which exposed only the {110} facets, exhibited better antibacterial activities against Escherichia coli compared to the octahedron, which exposed only the {111} facets

[en] We report the laser-induced formation of peanut-shaped gold nanoparticles (Au nanopeanuts) and gold nanowires (AuNWs), and their morphological properties. Pulsed laser irradiation of citrate-capped gold nanoparticles at 532 nm induces fragmentation, spherical growth, the formation of Au nanopeanuts, and the formation of AuNWs, sequentially. High-resolution transmission electron microscopy images reveal that the Au nanopeanuts are formed by instantaneous fusion of spherical nanoparticles in random orientation by laser heating. Furthermore, Au nanopeanuts are bridged in a linear direction to form AuNWs by an amorphous accumulation of gold atoms in the junction. The laser-produced Au nanopeanuts and AuNWs slowly disintegrate, restoring the spherical shape of the original Au nanoparticles when the laser irradiation is stopped. The addition of citrate effectively prevents them from transforming back to the nanospheres

[en] Highlights: • Sr_1-xCa_xS:Mn²⁺ phosphors were synthesized by performing a solid-state reaction. • CL spectra were examined under electron excitation from 4 to 10 kV. • The ability to tune the color from greenish yellow to red was observed. • Sr_1-xCa_xS:Mn²⁺ phosphors revealed the promise for the use in CNT-FEDs. Sr_1-xCa_xS:Mn²⁺ phosphors with calcium ion mole fraction (x) values of 0, 0.2, 0.4, 0.6, 0.8, and 1 were synthesized from CaS, SrS, and MnS by carrying out solid-state reactions. Cathodoluminescence (CL) spectra of these phosphors were acquired using moderate voltages in the range 4–10 kV in order to assess their applicability to carbon nanotube field emission displays (CNT-FEDs). The wavelength at the maximum intensity of the CL spectra of the phosphors increases gradually from 549 to 602 nm, and then slightly decreases to 599 nm, as x is increased. This increase can be interpreted in terms of the crystal structures of the phosphors. The ability to tune the color of light emitted from the Sr_1-xCa_xS:Mn²⁺ phosphors from greenish yellow to red confirms the promise of these phosphors for use in CNT-FEDs.