Preparation and characterization of optical spectroscopy of Lu2O3:Eu nanocrystals

Nanoscale Lu₂O₃:Eu powders were prepared by solution combustion synthesis. X-ray diffraction (XRD), high-resolution electronic microscope (HREM), Fourier transform infrared spectroscopy (FT-IR), excitation and emission spectra, as well as fluorescent decay curves were measured to characterize the structure and luminescent properties of the samples. The results show that the compound of composition Lu₂O₃ crystallizes in pure cubic structure. By changing the ratio of glycine to nitrate in the combustion process, the particle size varies from 40 nm to less than 5 nm. The emission and excitation spectra strongly depend on the particle size of the samples. Novel emission band, red-shift of charge transfer band (CTB) and shortening of lifetime were observed in nanoscale samples.     

Preparation of Mn3O4 nanocrystallites by low-temperature solvothermal treatment of γ-MnOOH nanowires

The preparation of trimanganese tetroxide (Mn₃O₄) nanocrystallites from γ-MnOOH nanowires under mild conditions has been achieved by two steps: first, γ-MnOOH nanowires with a mean diameter of about 12 nm and lengths of up to several micrometers were directly prepared via hydrothermal reaction between KMnO₄ and toluene in water at 180°C for 24 h; then, pure Mn₃O₄ nanocrystallites could be obtained by solvothermal treatment of the γ-MnOOH nanowires in ethylenediamine (EDA) and ethylene glycol (EG) at 150°C for 24 h. It was found that the Mn₃O₄ product obtained in EDA comprised well-defined nanocrystallites with the size in the range of 15-35 nm, while the one obtained in EG consisted of aggregated nanoparticles with the size of less than 18 nm.The possible formation mechanism of nanocrystalline Mn₃O₄ in EDA and EG and reasons for the different effects of various solvents on the products were also proposed.     

CaF2对CaO-CaF2-B2O3-SiO2：Sm2O3玻璃的光致发光增强效应

用高温熔融法制备了掺杂Sm₂O₃的CaO-CaF₂-B₂O₃-SiO₂(CFBS:Sm)发光玻璃材料, 并借助X射线衍射(XRD)谱、傅里叶变换红外(FTIR)光谱以及光致发光(PL)光谱等分析手段研究了玻璃基体中CaF₂的摩尔分数及其结构、红外透过性能以及荧光性能的关系. XRD和FTIR测试表明, 玻璃基体中引入CaF₂并未引起非晶结构的变化但其红外透过峰发生移动. 光谱学测试表明, CFBS:Sm发光玻璃在404 nm波长激发下出现对应于Sm³⁺离子位于566、603和650 nm的特征荧光峰, 其发光颜色为橙红色(x=0.531, y=0.371). 此外, 随着玻璃基体中CaF₂摩尔分数的增加, CFBS:Sm发光玻璃的荧光发射强度、荧光寿命(Sm³⁺的⁴G_5/2能级)和荧光量子效率也表现出增大的趋势. 这种CFBS:Sm发光玻璃中荧光发射强度和荧光寿命的提高主要是由于玻璃基体中的CaF₂替代CaO引起基体相互作用和声子能量降低、无辐射跃迁减弱造成的.     

Solvothermal synthesis and luminescence properties of monodisperse Gd2O3:Eu and Gd2O3:Eu@SiO2 nanospheres

A series of uniform, monodispersed Gd(OH)³:Eu³⁺ nanospheres less than 100 nm were successfully synthesized with iron ions as catalyst and DMF as solvent under the solvothermal condition. Cetyltrimethyl ammonium bromide (CTAB) and Polyvinylpyrrolidone (PVP) were performed as co-surfactant during this facile procedure should be changed as A series of uniform, monodisperse Gd(OH)³:Eu³⁺ nanospheres less than 100 nm in diameter were successfully synthesized with solvothermal method. Iron ion was used as catalyst and Dimethylformamide (DMF) as solvent, Cetyltrimethyl Ammonium Bromide (CTAB) and Polyvinylpyrrolidone (PVP) were performed as surfactants. Further calcination process was applied to prepare Gd₂O₃:Eu³⁺ nanoshpheres during this facile procedure.     

Impact of Eu3+ Ions on Physical and Optical Properties of Li2O-Na2O-B2O3 Glass

The lithium sodium borate glasses doped with Eu³⁺ ion are prepared using melt quenching technique, their structural and optical properties have been evaluated. The density of prepared glasses exhibits an inverse behavior to the molar volume ranging from 2.26 g/cm³ to 2.43 g/cm³ and 26.95 cm³ /mol to 26.20 cm³ /mol, respectively. The absence of sharp peaks in XRD patterns confirms the amorphous nature of the prepared glasses. The absorption spectra yield four transitions centered at 391 nm (⁷F₀→⁵L₆), 463 nm (⁷F₀→⁵D₂), 531 nm (⁷F₀→⁵D₁), and 582 nm (⁷F₀→⁵D₀). The most intense red luminescence is observed at 612 nm corresponding to ⁵D₀→⁷F₂ transition under 390 nm laser excitations.     

Indirect radiotracer study of the adsorption of chromate ions on γ-Al2O3 and direct study of the adsorption of sulfate ions on Cr2O3 using 35S-labelled H2SO4

The specific adsorption of sulfate ions on Cr₂O₃ was studied by a radiotracer technique using ³⁵S-labelled sulfuric acid in low concentrations (c<10^–3 mol dm^–3) in the presence of a large excess of perchlorate supporting electrolyte. The pH and concentration dependence were determined. It was found that the extent of adsorption is determined by the protonation of the surface sites, similar to other oxides studied previously. A comparison of Cr₂O₃ and Al₂O₃ in this respect shows that the protonation of the former takes place at significantly lower pH values than that of the latter. The indirect radiotracer study of the adsorption of chromate on Al₂O₃ was carried out using labelled sulfate ions as indicator species. The results obtained show that the adsorption strength of chromate species is very low in comparison to sulfate ions and a regular Langmuir-like adsorption behaviour can be observed. It is believed that the observations presented may contribute to a better understanding of the behaviour of surface layers with a mixed oxide content. Electronic Publication     

Growth Mechanism and Characterization of Single-crystalline Ga-doped SnO2 Nanowires and Self-organized SnO2/Ga2O3 Heterogeneous Microcomb Structures

Single-crystalline Ga-doped SnO2 nanowires and SnO2:Ga2O3 heterogeneous microcombs were synthesized by a simple one-step thermal evaporation and condensation method. They were characterized by means of X-ray powder diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectroscopy (EDS), transmission electron microscopy (TEM) and selected-area electron diffraction (SAED). FE-SEM images showed that the products consisted of nanowires and microcombs that represent a novel morphology. XRD, SAED and EDS indicated that they were single-crystalline tetragonal SnO2. The influence of experimental conditions on the morphologies of the products is discussed. The morphology of the product showed a ribbon-like stem and nanoribbon array aligned evenly along one or both side of the nanoribbon. It was found that many Ga2O3 nanoparticles deposited on the surface of the microcombs. The major core nanoribbon grew mainly along the 110 direction and the self-organized branching nanoribbons grew epitaxially along 1110 or 1110 orientation from the (110) plane of the stem. A growth process was proposed for interpreting the growth of these remarkable SnO2:Ga2O3 heterogeneous microcombs. Due to the heavy doping of Ga, the emission peak in photoluminescence spectra has red-shifted as well as broadened significantly.     

Synthesis and crystal structure of the palladium oxides NaPd3O4, Na2PdO3 and K3Pd2O4

NaPd₃O₄, Na₂PdO₃ and K₃Pd₂O₄ have been prepared by solid-state reaction of Na₂O₂ or KO₂ and PdO in sealed silica tubes. Crystal structures of the synthesized phases were refined by the Rietveld method from X-ray powder diffraction data. NaPd₃O₄ (space group Pm3¯n, a=5.64979(6) Å, Z=2) is isostructural to NaPt₃O₄. It consists of NaO₈ cubes and PdO₄ squares, corner linked into a three-dimensional framework where the planes of neighboring PdO₄ squares are perpendicular to each other. Na₂PdO₃ (space group C2/c, a=5.3857(1) Å, b=9.3297(1) Å, c=10.8136(2) Å, β=99.437(2)°, Z=8) belongs to the Li₂RuO₃-structure type, being the layered variant of the NaCl structure, where the layers of octahedral interstices filled with Na⁺ and Pd⁴⁺ cations alternate with Na₃ layers along the c-axis. Na₂PdO₃ exhibits a stacking disorder, detected by electron diffraction and Rietveld refinement. K₃Pd₂O₄, prepared for the first time, crystallizes in the orthorhombic space group Cmcm (a=6.1751(6) Å, b=9.1772(12) Å, c=11.3402(12) Å, Z=4). Its structure is composed of planar PdO₄ units connected via common edges to form parallel staggered PdO₂ strips, where potassium atoms are located between them. Magnetic susceptibility measurements of K₃Pd₂O₄ reveal a Curie-Weiss behavior in the temperature range above 80 K.     

TiO2-Al2O3载体的制备方法对其负载的磷化镍催化剂加氢脱氮反应性能的影响

采用共沉淀法和原位溶胶-凝胶法制备了TiO₂-Al₂O₃复合载体,其负载的磷化镍催化剂采用等体积浸渍法和H₂原位还原法制备. 通过N₂吸附（BET）、X射线衍射（XRD）、透射电镜（TEM）、程序升温还原（TPR）,X射线光电子能谱（XPS）和等离子体发射光谱（ICP-AES）表征技术对催化剂进行了表征,并通过喹啉的加氢脱氮反应评价了催化剂的加氢脱氮性能. 结果表明,原位溶胶-凝胶法制成的复合载体基本保留了原有的γ-Al₂O₃的孔特征,具有较大的比表面积和较宽的孔分布,TiO₂主要以表面富集的形式分散在管状的γ-Al₂O₃表面,其负载的磷化镍催化剂还原后所形成的活性相为Ni₂P和Ni₁₂P₅;而共沉淀法制成的复合载体比表面积较小,孔径分布更加集中,TiO₂趋于在块状的Al₂O₃表面均匀分散,其负载的磷化镍催化剂具有更好的可还原性,还原后所形成的活性相为Ni₂P. 不同的载体制备方法和不同的钛铝比对催化剂加氢脱氮性能影响较大,当n（Ti）/n（Al）=1/8时,共沉淀法载体负载的催化剂表现出最佳的加氢脱氮性能,在340 ℃,3 MPa,氢油体积比500,液时空速3 h^-1的反应条件下,喹啉的脱氮率可以达到91.3%.     

Epoxide assisted sol-gel synthesis of rutile NixTi1-3xSb2xO2 solid solution nanoparticles

Rutile Ni _x Ti_1-3x Sb_2x O₂ solid solution nanoparticles were synthesized by a sol-gel route using propylene oxide as a gelation agent. Titanium oxide nanopowder and 12% TiCl₃ solution were used as the source for titanium to investigate the influence of the titanium precursors on the formation of the target materials. It was found that the nanoparticles prepared using 12% TiCl₃ solution showed a much lower phase formation temperature (700°C) as compared to those prepared from TiO₂ nanoparticles (1000°C). This lower phase formation temperature allowed a substantial reduction of the aggregation of the particles during calcination leading to the formation of nearly mono-dispersed nanoparticles of about 20 nm. The results of this work show that the epoxide assisted sol-gel method is capable to produce titanium-based ternary oxide solid solution nanoparticles, owing to the formation of a highly homogeneous precursor gel intermediate.     

Selective Catalytic Reduction of NO with Propene over Au/Fe2O3/Al2O3 Catalysts

A series of Au/Fe₂O₃/Al₂O₃ catalysts were prepared by the homogeneous deposition-precipitation method. The catalytic activity of the catalyst samples for selective catalytic reduction of NO by propene under oxygen-rich atmosphere was evaluated. The results showed that 2%Au/10%Fe₂O₃/Al₂O₃ exhibited good low-temperature activity. The maximum of NO conversion reached 43% at 300 °C, while it was only 21% over the 2%Au/Al₂O₃ catalyst at the same temperature. The addition of 2% steam to the feed gas had little effect on the catalytic activity. X-ray diffraction results indicated that both Au and Fe₂O₃ particles were highly dispersed over Al₂O₃. H₂-temperature-programmed reduction results indicated that there was strong interaction between Au and Fe₂O₃, which made the reduction of Fe₂O₃ easy. The synergistic effect between Au and Fe₂O₃ was probably responsible for the good catalytic performance of the Au/Fe₂O₃/Al₂O₃ catalyst at low temperature.     

Cu3B2O6/CuB2O4单晶的制备及其可见光催化降解亚甲基蓝

以醋酸铜/硝酸铜和硼酸为原料,柠檬酸作发泡剂,采用溶胶-凝胶法制得了高纯度的单晶结构硼酸铜（Cu₃B₂O₆/CuB₂O₄）. 利用X射线衍射（XRD）、扫描电镜（SEM）、高分辨率透射电镜（HRTEM）、热重-差热分析（TGDTA）等对样品进行了表征,并考察了Cu₃B₂O₆/CuB₂O₄在可见光（400 nm<λ<1100 nm）下对亚甲基蓝（MB）溶液的催化降解性能. 结果表明,两种结构的硼酸铜都具有良好的光催化性能. 当亚甲基蓝的初始浓度为50 mg·L^-1,催化剂用量为1 g·L^-1,光照6 h后,CuB₂O₄对亚甲基蓝的光催化降解率为63.36%,Cu₃B₂O₆对亚甲基蓝的光催化降解率为99.52%. 紫外-可见漫反射光谱（UV-Vis DRS）结果表明,Cu₃B₂O₆的中间能态宽度为1.78 eV,小于CuB₂O₄的中间能态宽度（1.95 eV）,且Cu₃B₂O₆的禁带宽度较窄（E_g=2.34 eV）,不仅可以发生价带顶与中间能态的电子跃迁,同时可以发生禁带间的电子跃迁,所以Cu₃B₂O₆比CuB₂O₄具有更高的可见光催化性能.     

WO3/TiO2 catalysts: Morphological and structural properties

Titania-supported tungsten oxide catalysts with different W loadings up to 9 wt. % and calcined at different temperatures have been prepared and characterized. It is found that W hinders the initial sintering of anatase, providing thermal stability. The interaction of W with TiO₂ and the amount of hydroxy groups present on the surface can limit diffusion, thus reducing the sintering rate.     

Controlled synthesis of bismuth oxo nanoscale crystals (BiOCl, Bi12O17Cl2, α-Bi2O3, and (BiO)2CO3) by solution-phase methods

We present the controlled solution-phase synthesis of several sheet- or rod-like bismuth oxides, BiOCl, Bi₁₂O₁₇Cl₂, α-Bi₂O₃ and (BiO)₂CO₃, by adjusting growth parameters such as reaction temperature, mole ratios of reactants, and the base used. BiOCl, Bi₁₂O₁₇Cl₂, and α-Bi₂O₃ could be prepared from BiCl₃ and NaOH, whereas (BiO)₂CO₃ was prepared from BiCl₃ and urea. BiOCl and Bi₁₂O₁₇Cl₂ could also be prepared from BiCl₃ and ammonia. The α-Bi₂O₃ sample exhibited strong emission at room temperature.     

A novel nonaqueous route to V2O3 and Nb2O5 nanocrystals

The reaction between transition metal alkoxides and benzyl alcohol provides a novel soft chemistry route to metal oxide nanoparticles. The method allows the preparation of nanocrystals of two important transition metal oxides, namely V₂O₃ and Nb₂O₅. Although the reaction temperatures of 200–220 °C are comparably low, the obtained particles are highly crystalline. According to TEM investigations, the V₂O₃ crystals exhibit particle sizes between 20 and 50 nm, and the Nb₂O₅ crystals display platelet-like particle shapes with sizes of 50–80 nm, without any indications of amorphous character.     

Tartaric acid-assisted co-precipitation synthesis of Er3+-doped Lu2O3 nanopowders

Erbium-doped lutetia nanopowders were synthesized by a novel co-precipitation method using tartaric acid as precipitant.The properties of the samples were investigated by Fourier transform infrared spectroscopy（FTIR）,X-ray diffraction（XRD）,TG-DSC, field emission scanning electron microscopy（FE-SEM）,and upconversion luminescence analysis.Pure cubic Lu₂O₃ nanopowders were directly obtained when the precursor was calcined at 800℃for 2 h,the samples showed strong upconversion luminescence under excitation of 980 nm laser diode.     

Sm2O3Ga2O3 and Gd2O3Ga2O3 phase diagrams

Four definite compounds exist in the Sm₂O₃Ga₂O₃ binary phase diagram, namely: Sm₃GaO₆, Sm₄Ga₂O₉, SmGaO₃, and Sm₃Ga₅O₁₂. The $\text{3}\text{1}$ compound is orthorhombic (space group Pnna - Z.4) with the cell parameters: a = 11.40₀Å, b = 5.51₅Å, c = 9.07Å and belongs to the oxysel family. Sm₃GaO₆ and SmGaO₃ melt incongruently at 1715 and 1565°C; Sm₄Ga₂O₉ and Sm₃Ga₅O₁₂ have a congruent melting point at 1710 and 1655°C. With regard to the Gd₂O₃Ga₂O₃ system three definite compounds have been identified: Gd₃GaO₆, Gd₄Ga₂O₉, and Gd₃Ga₅O₁₂. Only the garnet melts congruently at 1740°C with the following composition: Gd_3.12Ga_4.88O₁₂. Gd₃GaO₆, and Gd₄Ga₂O₉ melt incongruently at 1760 and 1700°C. GdGaO₃ is only obtained by melt overheating which may yield an equilibrium or a metastable phase diagram.     

Photoluminescence dependence on imposing bias for ZnGa2O4 and ZnGa2O4 activated with Mn or Cr n-type semiconductor electrodes

Photoluminescence (PL) dependence was investigated by imposing cathodic and anodic bias for ZnGa₂O₄, ZnGa₂O₄:Mn and ZnGa₂O₄:Cr n-type semiconductor electrodes. Under the cathodic bias PL intensity was weak at about 1/3 times compared with imposing no bias, while under the anodic bias the intensity was strong at about 2 times maximally by using the ZnGa₂O₄:Mn and ZnGa₂O₄:Cr electrodes although no change about the intensity was observed by using the ZnGa₂O₄ electrode. These results suggest that the emission attributed to recombination between electrons and holes is decreased by flow of cathodic current under the cathodic bias while the emission is increased to decrease at non-radiative transition rates under the anodic bias when the energy relaxation occurs.     

Photoluminescence properties of a novel phosphor, Na3La9O3(BO3)8:RE(RE=Eu,Tb)

The new oxyborate phosphors, Na₃La₉O₃(BO₃)₈:Eu³⁺ (NLBO:Eu) and Na₃La₉O₃(BO₃)₈:Tb³⁺ (NLBO:Tb) were prepared by solid-state reactions. The photoluminescence characteristics under UV excitation were investigated. The dominated emission of Eu³⁺ corresponding to the electric dipole transition ⁵D₀→⁷F₂ is located at 613 nm and bright green luminescence of NLBO:Tb attributed to the transition ⁵D₄→⁷F₅ is centered at 544 nm. The concentration dependence of the emission intensity showed that the optimum doping concentration of Eu and Tb is 30% and 10%, respectively.     

Effect of sol-gel derived Al2O3-ZrO2 and Al2O3-TiO2 oxides on the selectivity of NO reduction by CO under oxidizing conditions

The role of Al₂O₃-ZrO₂ and Al₂O₃-TiO₂ sol-gel prepared supports in the activity of platinum for the NO reduction by CO under oxidizing conditions has been studied. ²⁷Al MAS-NMR spectra have shown the formation of pentacoordinate Al^V in alumina-zirconia support. ZrO₂ or TiO₂ crystalline phases cannot be identified by XRD diffraction, suggesting the formation of nanosized structures supported on alumina. When the reaction was carried out in presence of oxygen, large amounts of NO₂ were observed on Pt/Al₂O₃-ZrO₂catalyst, while the formation of N₂O is more prononced on Pt/Al₂O₃-TiO₂ catalyst. The effect of water during NO reduction is discussed. This revised version was published online in June 2006 with corrections to the Cover Date.