High photocatalytic activity over starfish-like La-doped ZnO/SiO_2 photocatalyst for malachite green degradation under visible light

In this work,the unique starlike La-doped ZnO-SiO2 photocatalysts were constructed by an evaporation and calcination method and characterized in detail.UV-vis reflectance and DFT calculation confirm that the doping with La allows to obtain a decrease of band gap of ZnO/SiO_2,which enhances visible light absorbance and oxidizing ability.The photoluminescence intensity reduces greatly,indicating more effective separation of the photo generated carriers of La-doped ZnO-SiO2.Photocatalytic activities of Ladoped ZnO-SiO2 with different doping ratios under simulated visible light irradiation were evaluated with malachite green(MG) as a model pollutant.Under optimized conditions including solution pH of 8,15 mg/L of MG solution and 15 mg of catalyst dosage,0.2% La-ZnO-SiO2 exhibits the best catalytic activity in photodegradations of MG in water.The removal and mineralization efficiency of MG can reach 96.1%and 70.9% in 140 min,respectively.The as-prepared catalysts present superior stability and recyclability after four times reuse.Moreover,selective quenching experiments indicate that hydroxyl radical(·OH),hole(h~+) and superoxide radical(·O_2~-) are the main reactive species responsible for MG degradation.Possible mechanism for photocatalytic elimination of MG over La-doped ZnO/SiO_2 photocatalyst is finally proposed.     

Lanthanum and boron co-doped BiVO4 with enhanced visible light photocatalytic activity for degradation of methyl orange

BiVO4 photocatalysts co-doped with La and B were prepared by sol-gel method using citric acid as chelate.The samples were characterized by X-ray photoelectron spectroscopy(XPS),X-ray diffraction(XRD),scanning electron microscopy(SEM),Brumauer-Emmett-Teller(BET),UV-Vis diffuse reflectance spectra(DRS) and the photocatalytic activity was investigated by photocatalytic degradation of methyl orange(MO).The results showed that boron and lanthanum ions incorporated into the lattice of BiVO4,and co-doping led to more surface oxygen vacancies,high specific surface areas,small crystallite size,narrow band gap and intense light absorbance in visible region.And the doped La(III) ions could help the separation of photogenerated electrons.Compared with BiVO4 and B-BiVO4,the photocatalytic activity of La-B co-doped BiVO4 was remarkably improved due to the synergistic effects of the co-doped ions.The degradation rate of MO in 60 min was 98.4% when La doping content was 0.05 mol.%,which was much higher than that of pure BiVO4(20%) and B-BiVO4(37%).     

Improved luminescence and photocatalytic properties of Sm3+-doped ZnO nanoparticles via modified sol-gel route:A unified experimental and DFT+U approach

In the current study,a modified sol-gel route was used to produce undoped and Sm³⁺ doped(1 mol%,3 mol% and 5 mol%) ZnO nanoparticles(NPs).The study of opto-structural properties of Sm³⁺ doped NPs was carried out both experimentally and theoretically.Complete dissolution of Sm³⁺ ions into the ZnO lattice is obviously seen from X-ray diffraction(XRD) analysis.Morphological evolution with doping was studied using field emission scanning electron microscopy(FESEM) an...     

La-Ce共掺杂制备La3+-Ce3+/ZnO及其对亚甲基蓝的光催化降解

采用溶胶凝胶法制备了La-Ce共掺杂的La3+-Ce3+/ZnO光催化剂,同时用同种方法制备了ZnO、La3+/ZnO和Ce3+/ZnO以作对比.通过X射线衍射仪、透射电镜、紫外可见分光光度计,比表面及孔隙度分析仪等对制备的光催化剂进行了表征.以亚甲基蓝为模型污染物对所制备的光催化剂的光催化特性进行了评价.结果表明,所制备的La3+-Ce3+/ZnO光催化剂基本呈长方柱状,尺寸平均为57.3 nm,La-Ce共掺杂提高了ZnO的结晶度,促进了晶粒的长大.根据光催化实验结果,La-Ce共掺杂能够显著提高ZnO的光催化活性.在光催化降解500 mL的10 mg·L-1亚甲基蓝实验中,La3+-Ce3+/ZnO光催化剂对亚甲基蓝的降解率达93.7%,比纯ZnO、La3+-ZnO和Ce3+-ZnO分别提高了21.4%、19.2%和9.3%.      

Effect of Gd~(3+)-,Pr~(3+)-or Sm~(3+)-substituted cobalt-zinc ferrite on photodegradation of methyl orange and cytotoxicity tests

Gd~(3+)-,Pr~(3+)-or Sm~(3+)-doped Co-Zn(Co_(0.5)Zn_(0.5)Fe_2 O_4) magnetic ferrites(i.e.,Co_(0.5)Zn_(0.5)Gd_(0.1)Fe_(1.9)O_4,Co_(0.5)Zn_(0.5)Pr_(0.1)Fe_(1.9)O_4 and Co_(0.5)Zn_(0.5)Sm_(0.1)Fe_(1.9)O_4) were prepared using a facile sol-gel approach,and the structure,surface morphology and chemical composition of the products were studied by means of scanning electron microscopy(SEM),energy dispersive X-ray analysis(EDX),X-ray diffraction(XRD),UVvisible diffuse reflectance spectroscopy(DRS),photoluminescence(PL) spectroscopy,Fourier transform infrared spectroscopy(FT-IR) and vibrating sample magnetometer(VSM) spectroscopy.XRD patterns show the Co-Zn product is composed of cubic spinel phases with few impurities or secondary phases,and the average crystallite sizes of the samples are determined to be approximately～51—80,～99—181,～68—103 and～83—133 nm.Also the coercivity and remnant and saturation magnetizations,evaluated by vibrating sample magnetometer(VSM),are found to increase linearly with the incorporation of Gd3+,Pr3+and Sm3+in the product formulation.The CO_(1-x)Zn_xFe_(2-y)R_yO_4 photocatalyst sample is found to display a red shift in its absorption,and exhibits outstanding photocatalytic effects in the degradation of MO under ultraviolet(UV) light.This is attributed to the reduction of the band gap of cobalt-zinc ferrite due to the presence of rare earth ions.Further in vitro evaluations of the cytotoxic effects of the synthesized nanoparticles were performed on a HeLa cell line.     

Synthesis,Characterization and Photocatalytic Studies of La,Dy-doped ZnO nanoparticles

Rare earth La Dy co-doped ZnO nanoparticles (Zn_0.98La_0.01Dy_0.01O, Zn_0.96La_0.02Dy_0.02O, Zn_0.94La_0.03Dy_0.03O, and Zn_0.92La_0.04Dy_0.04O) were synthesized by co-precipitation method at temperature of 500 °C for 2 h in air. The synthesized samples were characterized by powder X-ray diffraction (XRD), FE-SEM/EDS and UV–Visible spectrophotometer. The prepared nanoparticles exhibit a hexagonal wurtzite structure as observed from XRD measurements. It was observed that the La Dy co- doped ZnO nanoparticles (Zn_0.98La_0.01Dy_0.01O, Zn_0.96La_0.02Dy_0.02O, Zn_0.94La_0.03Dy_0.03O, and Zn_0.92La_0.04Dy_0.04O) exhibit higher optical absorbance spectrum at 400 nm to 800 nm wavelength due to its smaller crystal size (12.2 nm) as compared to the un- doped ZnO nanoparticles (253.1 nm). The photocatalytic activity of rare earth La Dy co- doped ZnO nanoparticles were studied by performing the decomposition of methylene blue dye solution under UV light irradiation within 0–4 h. The methylene blue dye solution was considerably photodegraded by Zn_0.92La_0.04Dy_0.04O photocatalyst under UV light irradiation within 2–4 h to the efficiency of 96 %. The pseudo first order rate constant of the degradation was found to be 0.0264 S^?1. The degradation mechanisms are discussed in this work.     

Wastewater treatment using Fe-doped perovskite manganites by photocatalytic degradation of methyl orange,crystal violet and indigo carmine dyes in tungsten bulb/sunlight

We documented(ⅰ) the decolorization of wastewater in visible light,which contains methyl orange,crystal violet and indigo carmine dyes,using La_0.7Sr_0.3Mn_1-xFe_xO₃(x=0.0,0.05,0.1 and 0.5) manganites and(ⅱ) efficient separation of photocatalysts from water using magnetic field.These ceramic photocatalysts were sintered at 1050℃ for 12 h.Ceramics were characterized by X-ray diffraction(XRD),soft X-ray absorption spectroscopy(SXAS),Fourier transf...     

Thermally stable photoluminescence and long persistent luminescence of Ca3Ga4O9:Tb3+/Zn2+

A green long persistent luminescence (LPL) phosphor Ca₃Ga₄O₉:Tb³⁺/Zn²⁺ was prepared. Ca₃Ga₄O₉ matrix exhibits blue self-activated LPL due to the creation of intrinsic traps. When Tb³⁺ is doped, the photoluminescence (PL) and LPL colors change from blue to green with their intensities significantly enhanced. The doping of Zn²⁺ evidently improves the PL and LPL performances of the Ca₃Ga₄O₉ matrix and Ca₃Ga₄O₉:Tb³⁺. The thermoluminescence (TL) spectra show that a successive trap distribution is formed by multiple intrinsic traps with different depths in the Ca₃Ga₄O₉ matrix, and the incorporation of Tb³⁺ and Zn²⁺ effectively increases the densities of these intrinsic traps. The existence of a successive trap distribution makes the Ca₃Ga₄O₉:Tb³⁺/Zn²⁺ phosphor exhibit thermally stable PL and LPL. It is indicated that this phosphor shows great promise for the application such as high-temperature LPL phosphor.     

Investigation of the phase composition of accretions formed into WHB under flash smelting of copper concentrate

The phase composition of the depositions formed in the radiation section of the waste heat boiler utilizer (RS of WHB) after injecting sulphatizing flow in the volume of the off-gases from the uptake of flash smelting furnace for copper sulphide concentrate smelting was studied. With the help of X-ray diffraction (XRD), Reflected-light microscopy and Electron probe microanalysis (EPMA) of samples from the accretions, it was established that the main crystalline phases in the accretions were spinel, delafossite, cuprite and tenorite. The results from EPMA have shown that the spinel phase is with variable composition from cuprospinel to solid solution into the system Fe₃O₄-CuFe₂O₄-ZnFe₂O₄ (magnetite-cuprospinel-franklinite). Calculated on the basis of XRD and EPMA approximate formulae for the phases, identified in the samples from the accretions were the following: of the cuprospinel-(Cu_0.85²⁺Zn_0.09²⁺Fe_0.06²⁺)(Fe_1.87³⁺Al_0.10³⁺Si_0.03⁴⁺)O₄; of the spinel solid solution—(Cu_0.32²⁺Zn_0.36²⁺Fe_0.32²⁺)(Fe_1.81³⁺Al_0.19³⁺)O₄; Delafossite—Cu_1.07Fe_0.93O₂; cuprite—Cu_1.99Fe_0.02Si_0.01O and tenorite—Cu_0.993Fe_0.008O. The influence of the temperature on the sulphate formation processes of copper and iron oxides in the dust-gas flow was evaluated, based on experimental data and thermodynamic analysis of phase equilibriums in the systems Cu-S-O and Fe-S-O for the conditions, typical of the radiation section of the waste heat boiler (RS of WHB).     

Photocatalytic degradation of imidacloprid by composite catalysts H3PW12O40/La-TiO2

A series of La-doped TiO2 with different mass fractions were prepared by sol-gel method. Composite catalysts H3PW12O40/La-TiO2 with different loading levels were synthesized using impregnation method. The prepared samples were characterized by fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), scanning electron microscopy (SEM), UV-vis diffuse reflectance spectroscopy (DRS) and nitrogen adsorption-desorption analysis. The Keggin structure of H3PW12O40 (HPW) remained intact on the surface of the composites, they had relatively uniform spherical grains of diameter less than 20 nm. The visible light activity of prepared composites were improved by loading HPW and doping La. The prepared composites were used as photocatalysts in degradation of pesticide imidacloprid. Results revealed that 20%H3PW12O40/0.3%La-TiO2 possessed the best photocatalytic activity. Thus, the degradation conversion of imidacloprid reached 98.17% after 60 min irradiation when 20%H3PW12O40/0.3% La-TiO2 was used as catalysts. The degradation of imidacloprid corresponded with first-order kinetic reaction, and the half life of the degradation of imidacloprid was 9.35 min in the optimal conditions.     

Study on photodegradation of Azo dye by polyoxometalates/polyvinyl alcohol

A series of photocatalysts, K11[Ln(PW11O39)2]/PVA (Ln=La, Ce, Pr, Nd, Sm) were prepared by K11[Ln(PW11O39)2] (Ln=La, Ce, Pr,Nd, Sm) containing five kinds of lanthanides and polyvinyl alcohol as the support. The catalysts obtained were characterized by Fourier trans-form infrared spectra, UV-vis spectra, powder X-ray diffraction, and scanning electron microscopy, indicating that the structure of K11[Ln(PW11O39)2] and polyvinyl alcohol remained intact, respectively. The photocatalysts exhibited efficient catalytic activity to degrade methyl orange, Congo Red, Ponceau 2R. The maximal degradation conversions of the three kinds of dyes were 99.58%, 47.61%, 72.42%, respectively.     

Removal of organic pollutants by lanthanide-doped MIL-53(Fe) metal-organic frameworks:Effect of dopant type in magnetite precursor

A series of undoped and lanthanide doped MIL-53(Fe)/Ln-Fe₃O₄(Ln=La,Nd,or Gd) metal-organic frameworks(MOFs) were prepared by the solvothermal method.All prepared samples were characterized by X-ray diffraction(XRD),Fourier transform infrared spectroscopy(FT-IR),Brunauer-Emmett-Teller(BET) measurements,scanning electron microscopy(SEM),and thermal analysis.XRD and FT-IR results ascertain the successful MOF formation for all prepared samples.MIL-53(Fe)/La-Fe₃O_...     

Sol-gel preparation of La-doped bismuth ferrite thin film and its low-temperature ferromagnetic and ferroelectric properties

Bi0.85La0.15FeO3 thin film was prepared on ATO glass substrates by sol-gel technique. The effect of La doping on phase structure, film surface quality, ion valence, and ferroelectric/magnetic properties of Bi0.85La0.15FeO3 film were investigated. La dop-ing suppressed the formation of impurity phases and the transition of Fe3+ to Fe2+ ions at room temperature. Compared with the un-doped BiFeO3, La-doping also increased the average grain size and the film density, which resulted in the decrease of film leakage current density. The remanent polarization and saturation magnetization were enhanced significantly by La doping. The remanent polarization of Bi0.85La0.15FeO3 films gradually decreased while saturation magnetization increased with the decrease of measuring temperature within a range from 50 to 300 K.     

Experimental study of phase equilibria in the “FeO”-ZnO-(CaO + SiO2) system with CaO/SiO2 weight ratios of 0.33, 0.93, and 1.2 in equilibrium with metallic iron

The pseudoternary sections “FeO”-ZnO-(CaO + SiO₂) with CaO/SiO₂ weight ratios of 0.33, 0.93, and 1.2 in equilibrium with metallic iron have been experimentally investigated in the temperature range from 1000 °C to 1300 °C (1273 to 1573 K). The liquidus surfaces in these pseudoternary sections have been experimentally determined in the composition range from 0 to 33 wt pct ZnO and 30 to 70 wt pct (CaO + SiO₂). The sections contain primary-phase fields of wustite (Fe _x Zn_1−x O_1+y ), zincite (Zn _z Fe_1−z O), fayalite (Fe _w Zn_2−w SiO₄), melilite (Ca₂Zn _u Fe_1−u Si₂O₇), willemite (Zn _v Fe_2−v SiO₄), dicalcium silicate (Ca₂SiO₄), pseudowollastonite and wollastonite (CaSiO₃), and tridymite (SiO₂). The phase equilibria involving the liquid phase and the solid solutions have also been measured.     

Experimental study of phase equilibria in the “FeO”-ZnO-(CaO + SiO2) system with the CaO/SiO2 weight ratio of 0.71 at metallic iron saturation

The pseudoternary section “FeO”-ZnO-(CaO + SiO₂) with a CaO/SiO₂ weight ratio of 0.71 in equilibrium with metallic iron has been experimentally investigated in the temperature range from 1000 °C to 1300 °C (1273 to 1573 K). The liquidus surface in this pseudoternary section has been determined in the composition range of 0 to 33 wt pct ZnO and 30 to 70 wt pct (CaO + SiO₂). The system contains primary-phase fields of wustite (Fe _x Zn_1−x O_1−y ), zincite (Zn _z Fe_1−z O), fayalite (Fe _w Zn_2−w SiO₄), melilite (Ca₂Zn _u Fe_1−u Si₂O₇), and pseudowollastonite (CaSiO₃). The phase equilibria involving the liquid phase and the solid solutions have also been measured.     

Preparation,structure, luminescence properties of europium doped zinc spinel structure green-emitting phosphor ZnAl2O4:Eu2+

The Zn_(1-x)Al_2 O_4:xEu~(2+) phosphor powders were synthesized by the solid-state reaction method.The synthesis temperature for ZnAl_2 O_4 was optimized,whereas the phase structure,TEM images,photoluminescence(PL) properties,the concentration quenching mechanism,the fluorescence decay curves,as well as the CIE chromaticity coordinates of the samples were investigated in details.Under the excitation at 379 nm,the phosphor exhibits an asymmetric broad-band green emission with a peak at 532 nm,which is ascribed to the 5 d-4 f transition of Eu2+.When the doping concentration of Eu2+ ions is 0.01,the luminescence intensity of the sample reaches the maximum value.It is further proved that the exchange interaction results in the concentration quenching of Eu2+ in the Zn_(1-x)Al_2 O_4:xEu~(2+) phosphor powders.The thermal quenching property of ZnAl_2 O_4:Eu~(2+)phosphor was investigated and the quantum efficiency(QE) values of the selected Zn_(0.99)Al_2 O_4:0.01 Eu~(2+) phosphor was measured and determined as 54.85%.The lifetime of the optimized sample Zn_(0.99)Al_2 O_4:0.01 Eu~(2+) is 3.0852 μs and the CIE coordinate of the sample was calculated as(0.3323,0.5538) with high-color-purity green emission.All properties indicate that the green-emitting ZnAl_2 O_4:Eu~(2+) phosphor powder has potential application in white LEDs.     

水热法合成Ag2CO3/ZnO异质结复合光催化剂及其光催化性能

采用水热法合成了一系列不同Ag₂CO₃含量的新型Ag₂CO₃/ZnO异质结复合光催化剂, 运用X射线粉末衍射(XRD)、扫描电镜(SEM)、X射线光电子能谱(XPS)、傅里叶变换红外光谱(FT-IR)、紫外-可见漫反射吸收光谱(UV-vis DRS)等系列手段对所制备的光催化剂进行了表征, 并以紫外光(254 nm)为光源, 评价了催化剂光催化降解甲基橙的活性, 考察了不同Ag₂CO₃复合量、不同水热温度对ZnO复合光催化剂反应活性的影响.结果表明, 当Ag₂CO₃含量为2 %、水热温度为140 ℃, 复合光催化剂具有最大的光催化活性, 降解率达到86.31 %.Ag₂CO₃/ZnO异质结复合光催化剂具有更高的光催化活性主要原因是复合光催化剂对紫外光有很强的吸收能力, 适量Ag₂CO₃能提高光生电子-空穴对的分离效率, 并改善催化剂的物理性能.      

Highly dispersed CeO2–x nanoparticles with rich oxygen vacancies enhance photocatalytic performance of g-C3N4 toward methyl orange degradation under visible light irradiation

CeO₂/g-C₃N₄ photocatalysts have attracted tremendous attention in the photocatalytic degradation of organic pollutants. The design and construction of highly active CeO₂/g-C₃N₄ photocatalysts without harsh conditions are still challenging. Herein, highly dispersed CeO_2–x nanoparticles with rich oxygen vacancies were successfully precipitated on the surface of g-C₃N₄ under mild conditions. The fabricated CeO_2–x/g-C₃N₄ exhibits remarkable activity and stability for photocatalytic degradation of MO pollutant. The optimal rate constant of MO degradation over CeO_2–x/g-C₃N₄ is about 0.031 min^?1, which is three times higher than that of g-C₃N₄. A negligible activity decrease is observed after three cycling runs. The enhanced catalytic performance can be ascribed to the excellent dispersion of CeO_2–x with rich oxygen vacancies that benefit O₂ adsorption and visible light absorption. In addition, the proper band alignment between CeO_2–x and g-C₃N₄ is conducive to the highly efficient separation of photogenerated electron–hole pairs.     

Synthesis of yttrium and cerium doped ZnO nanoparticles as highly inexpensive and stable photocatalysts for hydrogen evolution

Yttrium and cerium co-doped ZnO nanoparticles were synthesized by combustion route and characterized using X-ray diffraction(XRD),scanning electron microscopy(SEM),Brunauer-Emmett-Teller(BET),energy dispersive spectroscopy(EDS),X-ray photoelectron spectroscopy(XPS),UV-visible diffuse reflectance spectroscopy(UV-vis DRS),photoluminescence(PL)and electrochemical impedance spectroscopy(EIS)techniques.The introduction of yttrium ions has efficiently increased the relative percentage of Ce³⁺ions in ZnO.Yttrium and cerium co-doped ZnO shows efficient photo activity for hydrogen evolution(10.61 mmol/((g·h))higher than previously reported optimal value for rare earth codoped ZnO photocatalysts.This remarkably increased hydrogen evolution can be ascribed to the synergy between electronic anchoring effect of Y³⁺/Y²⁺and Ce⁴⁺/Ce³⁺redox couples.This report presents new idea for the synthesis of efficient photocatalyst using economical route and ion anchoring effect.The hydrogen evolution was also tested using Na₂S and Na₂SO₃as electron donors under visible light illumination.The synthesized photocatalysts also exhibit high stability.     

Variation of Fe3+/Fe2+ and Cu2+/Cu+ equilibrium with basicity of oxide melts

Oxidation-reduction equilibrium experiments were conducted with Li₂O-CaO-Al₂O₃-ZnO-SiO₂-B₂O₃ melts containing small concentrations of either copper oxide or iron oxide. The results indicated that, for oxide melts containing relatively large proportions of amphoteric oxides, i.e., Al₂O₃ and ZnO, the ratios lcub;(Cu²⁺)/(Cu⁺)P _{O 2} ^1/4rcub; and lcub;(Fe³⁺)/(Fe²⁺)P _{O 2} ^1/4rcub; decreased with an increase in basicity. With further increase in basicity, however, these ratios became independent of basicity. For very basic melts, the ratios increased with an increase in basicity. These variations of lcub;(Cu²⁺)/(Cu⁺)P _{O 2} ^1/4rcub; and lcub;(Fe³⁺)/(Fe²⁺)P _{O 2} ^1/4rcub; can be interpreted in terms of the optical basicity of the oxide melts and are consistent with the following general expressions for the red-ox equilibria within acidic and relatively basic melts, respectively: M ⁿ⁺+(1/4)O₂=M⁽ⁿ⁺¹⁾⁺+(1/2)O²⁻ M ⁿ⁺+(1/4)O₂+(3/2)O²⁻=MO₂ ⁽³⁻ⁿ⁾ and M ⁿ⁺+(1/4)O₂=(3/4)M⁽ⁿ⁺¹⁾⁺+(1/4)MO₂ ⁽³⁻ⁿ⁾