Hydrothermal synthesis and characterization of Bi2O3 nanowires

An alternative two-step method has been proposed for the synthesis of Bi₂O₃ nanowires with a diameter of about 40 nm from common and cost-effective Bi(NO₃)₃·5H₂O, Na₂SO₄, and NaOH. That is, first, Bi₂O(OH)SO₄ nanowires were prepared through the precipitation reaction of Bi(NO₃)₃·5H₂O and Na₂SO₄ in distilled water under the ambient condition and second, monoclinic phase Bi₂O₃ nanowires were prepared via the hydrothermal reaction of Bi₂O(OH)SO₄ and NaOH at 120 °C for 12 h. The resultant products were characterized by X-ray diffraction, field emission scanning electron microscope, and high resolution transmission electron microscopy. In addition, the photocatalytic studies indicated that the as-synthesized Bi₂O₃ nanowires were a kind of promising photocatalyst in remediation of water polluted by some chemically stable azo dyes.     

Green hydrothermal synthesis and optical absorption properties of ZnO2 nanocrystals and ZnO nanorods

A green hydrothermal method was proposed for the controllable synthesis of ZnO₂ nanocrystals and ZnO nanorods, using the common and cost-effective 2ZnCO₃·3Zn(OH)₂ powder and 30 mass% H₂O₂ aqueous solution as the raw materials. The characterization results from X-ray diffraction, high resolution transmission electron microscopy, transmission electron microscopy and energy dispersive X-ray spectroscopy indicated that the products synthesized at 100-120 °C for 6 h or at 170 °C for 0 h were cubic phase ZnO₂ nanocrystals; while those synthesized at 170 °C for 3-6 h were hexagonal phase ZnO nanorods. The UV-vis absorption spectra showed that the as-synthesized ZnO₂ nanocrystals and ZnO nanorods had optical band gaps of about 4.1 and 3.3 eV, respectively.     

Microwave-assisted hydrothermal synthesis and optical property of Co3O4 nanorods

Single crystalline Co₃O₄ nanorods have been successfully synthesized through thermal decomposition of the precursor, which was obtained by the microwave-assisted hydrothermal route. The obtained sample was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectrometer (FT-IR), and X-ray photoelectron spectroscopy (XPS). The results confirm that the resulting oxide was pure single-crystalline Co₃O₄ nanorods. The optical property test indicates that the absorption peak of the nanorods shifts towards short wavelength. And the blue shift phenomenon might be ascribed to the quantum effect.     

Flame spray synthesis of Lu2O3 nanoparticles

We have used a Flame Spray Pyrolysis (FSP) technique to synthesize lutetium oxide (Lu₂O₃) nanoparticles from lutetium nitrate. Optical quality transparent ceramics were prepared via hot pressing of the Lu₂O₃ nanoparticles formed using the FSP technique. We present data demonstrating that the FSP system can be used to control the material phase of the nanoparticles by changing the O₂ dispersion gas flow rate. Different O₂ dispersion gas flow rates affect the particle residence time in the flame resulting in the formation of different nanoparticulate phases. Our work has led to the synthesis of a metastable phase of Lu₂O₃ which has never been reported using the FSP technique. Significantly, the presence of the metastable phase enables the ceramic powders to be hot pressed at lower temperatures resulting in smaller grain sizes, resulting in excellent optical quality Lu₂O₃ windows.     

Solvothermal synthesis and photoluminescence properties of ZnO nanorods and nanorod assemblies from ZnO2 nanoparticles

Without the use of any extra surfactant or template, hexagonal phase ZnO crystallites consisting of individual nanorods or nanorod assemblies were synthesized simply by solvothermal treatment of several nanometer ZnO₂ nanoparticles in three different solvents (including ethanol, 80 wt.% hydrazine hydrate aqueous solution and ethylenediamine) at 150 °C for 24 h. The structures and optical properties of the resultant products were characterized by means of X-ray powder diffraction (XRD), scanning electron microscope (SEM), and room temperature photoluminescence (RTPL) spectra. The RTPL spectra of the resultant products all showed a much stronger ultraviolet bandgap emission peaking at around 387 nm and a weaker emission associated with the defect level. The as-synthesized ZnO crystallites are promising materials for the optoelectronic devices due to their excellent UV emission properties.     

Facile synthesis and optical band gap calculation of Mn3O4 nanoparticles

Mn₃O₄ nanoparticles were prepared by a simple solid state decomposition method. Four manganese benzoic acid complexes were synthesized through semi-solid phase reaction method as precursors for the preparation of Mn₃O₄ nanoparticles. The calcination temperature of the precursors was determined from thermal gravimetrical analyses (TGA). The resulting nanoparticles were characterized by XRD, SEM, STM and HRTEM. The obtained particle size is in the range 39–90 nm. HRTEM indicated the formation of spherical nanoparticles. The optical absorption measurements for the obtained nanoparticles showed that the fundamental absorption edge obeys Tauc's relation for the allowed direct transition. It was found that, the optical band gap (E_g) increases with the decrease of the particle size of the Mn₃O₄ nanoparticles.     

Raman optical properties of Cu(OH)2 nanowires

We have for the first time investigated Raman optical properties of polycrystalline Cu(OH)₂ nanowires with an average diameter of ca. 9 nm and lengths of up to hundreds of micrometers that were synthesized by a simple surfactant-free solution-phase route at ambient temperature. The result indicated that the Raman peak of the as-prepared polycrystalline Cu(OH)₂ nanowires was obviously broadened, and red-shifted 16 cm^− 1 compared with that of bulk Cu(OH)₂ crystals. Based on the microstructure analysis and phonon confinement model of a crystal, we have proposed a rational explanation for the red-shift and broadening of Raman peak.     

Raman and photoluminescence properties of α-Al2O3 microcones with hierarchical and repetitive superstructure

Highly ordered α-Al₂O₃ microcones were readily generated by a facile thermal oxidation method. The α-Al₂O₃ superstructured microcones are composed of a large amount of nanocones, indicating a complex form and remarkable repetitive growth patterns of the superstructure microcones. Raman spectrum displays that the Al₂O₃ microcones match better with single crystal than bulk Al₂O₃, revealing a good crystalline nature. The photoluminescence (PL) spectrum reveals a strong red luminescence at 693 nm and three small-shoulder emission bands at 677, 706 and 712 nm, respectively. We deduce that variation in inhomogeneous tensile stress of the microcones that results in differences in local symmetry of the crystal should be responsible for the three unusual emission bands.     

Carbon-nanotube-supported Ag and Cu2O nanoparticles: Dendrimer-mediated synthesis and their broadband optical limiting properties

Multiwalled carbon nanotubes (MWCNTs) were covalently functionalized with fourth-generation poly(amido amine) (PAMAM) dendrimers with a trimesyl core (DT4), and the as-synthesized MWCNT-DT4 was used as the template for in situ growth of Ag and Cu₂O nanoparticles on MWCNTs. Extensive characterizations of the resultant hybrids have been performed using X-ray diffraction, transmission electron microscopy (TEM), high resolution TEM, energy dispersive X-ray spectroscopy, selected area electron diffraction, thermal gravimetric analysis, and X-ray photoelectron spectroscopy. The side-wall of the nanotubes was uniformly coated with the nanoparticles with mean sizes of 7–8 nm. The optical limiting property measurements of the nanoparticle-modified MWCNTs were carried out by the open-aperture z-scan technique. The results demonstrate that the samples suspended in water show broadband OL performance, and their OL behavior is better than that of MWCNT-DT4 in water due to the presence of Ag and Cu₂O nanoparticles.     

Na2Cd2I6L2(H2O)6 [L = Urotropine]: An interesting precursor for synthesizing CdO particles

A coordination polymer, Na₂Cd₂I₆L₂(H₂O)₆ [L = Urotropine] has been employed as sole precursor to synthesize CdO particles. Two different preparation methods viz (i) pyrolysis of the title compound at 700 °C for 2 h and (ii) forming cadmium hydroxide from the title compound followed by pyrolysis at 700 °C for 2 h have been used for the synthesis of nano sized CdO-I and CdO-II, respectively. From powder XRD data the lattice parameters (0.4701 and 0.4696 nm respectively for the two samples) and particle size (~ 77 and 30 nm for CdO-I and CdO-II) have been evaluated. Morphology of the two varieties of CdO is widely different as is evident from their SEM images. The estimated values of the band gap of 2.53 eV and 2.59 eV for CdO-I and CdO-II respectively are obtained from the optical spectral analysis.     

The transformation of Eu→Eu in SiO2-Al2O3-NaF-YF3: Eu glasses and glass ceramics

Transparent glasses and glass ceramics of SiO₂-Al₂O₃-NaF-YF₃: Eu³⁺ containing the YF₃ nano-crystals were prepared in air atmosphere and their spectroscopic properties are presented. The blue emission peaked at 433 nm shown in the spectra indicate the existence of Eu²⁺.The transformation of Eu³⁺→Eu²⁺ is related with the existence of F⁻, which is the key trigger for the transformation in air atmosphere. In addition, the emission intensities of Eu³⁺ and Eu²⁺ were also related with the concentrations of Eu³⁺. The emission intensities increased heavily with the increasing dopant of EuF₃ in both glasses and glass ceramics_. When the doped concentration of EuF₃ was higher than 0.5 mol.%, the concentration quenching effect occurred.     

Flower-like microparticles and novel superparamagnetic properties of new binary Co1/2Fe1/2(H2PO4)2·2H2O obtained by a rapid solid state route at ambient temperature

A new binary Co_1/2Fe_1/2(H₂PO₄)₂·2H₂O was synthesized by a simple, rapid and cost-effective method using CoCO₃-Fe(c)-H₃PO₄ system at ambient temperature. Thermal treatment of the obtained Co_1/2Fe_1/2(H₂PO₄)₂·2H₂O at 600 °C yielded as a binary cobalt iron cyclotetraphosphate CoFeP₄O₁₂. The FTIR and XRD results of the synthesized Co_1/2Fe_1/2(H₂PO₄)₂·2H₂O and its final decomposed product CoFeP₄O₁₂ indicate the monoclinic phases with space group P2₁/n and C2/c, respectively. The particle morphologies of both binary metal compounds appear the flower-like microparticle shapes. Room temperature magnetization results show novel superparamagnetic behaviors of the Co_1/2Fe_1/2(H₂PO₄)₂·2H₂O and its final decomposed product CoFeP₄O₁₂, having no hysteresis loops in the range of ±10,000 Oe with the specific magnetization values of 0.045 and 12.502 emu/g at 10 kOe, respectively. The dominant physical properties of the obtained binary metal compounds (Co_1/2Fe_1/2(H₂PO₄)₂·2H₂O and CoFeP₄O₁₂) are compared with the single compounds (M(H₂PO₄)₂·2H₂O and M₂P₄O₁₂; where M = Co, Fe), indicating the presence of Co ions in substitution position of Fe ions.     

Structural, electrical and optical properties of TiO2-WO3 polycrystalline ceramics

Mixed oxides from the TiO₂-WO₃ system were prepared as polycrystalline materials. Their phase composition and electrical conductivity were investigated using X-ray diffraction (XRD) and dc electrical measurements. The energy gap, evaluated on the basis of optical measurements, was presented as a function of W concentration. The influence of chemical composition on structural, semiconducting and optical properties of the TiO₂-WO₃ polycrystalline ceramics was discussed.     

Larger Ba(NO3)2/Sr(NO3)2 crystal growth and solubility determination

The solubility of Ba(NO₃)₂ and Sr(NO₃)₂ crystals in aqueous solution from 25 to 65 °C has been determined by both an optical interferometer and a weight technique. A Mach-Zehnder interferometer was used for measuring the concentration distribution of Ba(NO₃)₂ and Sr(NO₃)₂ near the solid/liquid interface during crystal growth and dissolution. A fringe carrier technique was introduced to visualize more clearly the boundary layer and to solve the concentration distribution. Crystals were successfully grown with sizes larger than  mm by a temperature cooling method. The Ba_xSr_1−x(NO₃)₂ crystal was also nucleated and grown. The Raman spectra of Ba_xSr_1−x(NO₃)₂ indicate that the barium ions probably degrade the properties of Sr(NO₃)₂.     

Hydrothermal synthesis of Cu3V2O7(OH)2·2H2O hierarchical microspheres and their electrochemical properties

Uniform Cu₃(OH)₂V₂O₇·2H₂O microspheres assembled by nanorods have been fabricated through a simple hydrothermal method for the first time employing copper hydroxide carbonate (Cu₂(OH)₂CO₃) as copper source without the assistance of any template or surfactant. The formation mechanism was proposed based on the evolution of this morphology as a function of hydrothermal time. The Electrochemical measurements revealed that the Cu₃(OH)₂V₂O₇·2H₂O microspheres displayed a high discharge capacity, which indicates that the Cu₃(OH)₂V₂O₇·2H₂O microspheres are promising cathode candidates for primary lithium batteries used in long term implantable cardioverter defibrillators (ICD).     

Crystal Structure of (H3O)2[(UO2)2(SeO4)3(H2O)2](H2O)3.5

Crystals of (H₃O)₂[(UO₂)₂(SeO₄)₃(H₂O)₂](H₂O)_3.5 were prepared from aqueous solutions by evaporation. The crystal structure [monoclinic system, space group P2₁/m, a = 11.9402(11), b = 13.6452(14), c = 13.7271(12) Å, β = 109.436(7)°, V = 2109.1(3) ų] was solved by the direct method and refined to R ₁ = 0. 048 (wR ₂ = 0. 082) for 3677 reflections with |F _hkl |F _hkl |. The structure consists of [(UO₂)₂(SeO₄)₃(H₂O)₂]₂₋ layers arranged parallel to the (010) plane. The layers are formed by uranium and selenium coordination polyhedra sharing common vertices and are linked with each other by hydrogen bonds through the H₂O and H₃O⁺ groups arranged between the layers. __________ Translated from Radiokhimiya, Vol. 47, No. 5, 2005, pp. 412–414. Original Russian Text Copyright ? 2005 by Krivovichev, Kahlenberg.     

Synthesis and photoluminescence of In2O3 nanocrystals and submicron crystals from InCl3•4H2O and thiourea

Two routes have been proposed for the synthesis of In₂O₃ powders from InCl₃•4H₂O and thiourea. One route involved a two-step procedure (that is, firstly, In₂S₃ clusters constructed with mainly nanoflakes were synthesized by heating the mixture of InCl₃•4H₂O and thiourea in air from room temperature to 200 °C, coupled with a subsequent washing treatment; secondly, In₂O₃ was obtained by calcining the In₂S₃ clusters in air at 600 °C for 6 h), and the other route was a one-step procedure (that is, In₂O₃ was synthesized directly by calcining the mixture of InCl₃•4H₂O and thiourea in air at 600 °C for 6 h). The resultant products were characterized by X-ray diffraction, energy dispersive X-ray spectroscopy, scanning electronic microscope and room temperature photoluminescence (RT-PL) spectra. It was observed that the In₂O₃ nanocrystals obtained via the two-step procedure exhibited PL peaks at about 453 and 471 nm, corresponding to the defeat-related emission; while the In₂O₃ submicron polyhedral crystals obtained via the one-step procedure and In₂O₃ pyramids obtained by calcining the only InCl₃•4H₂O in air at 600 °C for 6 h displayed a PL band centered at around 338 nm, corresponding to the band edge emission.     

Microemulsion-assisted solvothermal synthesis of Nd2(CO3)3·8H2O microstructures

Microstructures of Nd₂(CO₃)₃·8H₂O with various morphological structures and sizes were successfully synthesized using the microemulsion-assisted solvothermal method. The obtained products were characterized by X-ray diffraction (XRD), differential scanning calorimetry and thermal gravimetric analysis (DSC-TGA), scanning electron microscope (SEM), transmission electron microscope (TEM) and electron diffraction (ED). The results showed that pyramid-like and spherical Nd₂(CO₃)₃·8H₂O microstructures were synthesized depending on the reaction time and reaction temperature. Moreover, the reaction time and temperature also played important roles in controlling the morphologies and sizes of the resulting Nd₂(CO₃)₃·8H₂O microstructures.     

Growth and optical properties of Er,Yb:YAl3(BO3)4 crystal

Single crystal of erbium, ytterbium-codoped yttrium aluminum tetraborate Er,Yb:YAl₃(BO₃)₄(Er,Yb:YAB) has been grown by the flux method. The absorption spectrum in the visible and NIR regions of Er,Yb:YAl₃(BO₃)₄ crystal are measured at room temperature and fluorescence spectrum of Er,Yb:YAl₃(BO₃)₄ crystal are also measured at room temperature, excited by 976 nm laser. Not only the strong NIR emission peaks located at 1548 nm was observed, but also the visible up-conversion luminescence has been found. The specific heat of the Er/Yb:YAB crystal at room temperature is 0.81 J/g °C.     

Crystal growth and spectral properties of Pr:La2(WO4)3

Pr³⁺-doped La₂(WO₄)₃ single crystal with dimensions up to Ø 20 mm × 35 mm has been grown by the Czochralski method. The structure of the Pr³⁺:La₂(WO₄)₃ crystal was determined by the X-ray powder diffraction and the Pr³⁺ concentration in this crystal was determined. The absorption and fluorescence spectra of Pr³⁺:La₂(WO₄)₃ crystal were measured at room temperature, and the fluorescence lifetime of main emission multiplets were estimated from the recorded decay curves. The spectral properties related to laser performance of the crystal were evaluated.