铈对纳米铁氧体粉末电磁学性质影响的研究

采用固相反应制备的Ce0 .2 5FeNiO3,FeNiO5,Fe3O4 ,Fe2 O34种纳米粉体 ,在 1～ 2 0 0 0MHz范围内进行了电磁学性质 (μ′,μ″ ,ε′,ε″)及吸波特性的比较研究。发现 4种纳米粉体的 μ′数据大小顺序为Ce0 .2 5FeNiO3>FeNiO5>Fe3O4 >Fe2 O3,μ″的变化幅度为Ce0 .2 5FeNiO3>Fe3O4 >FeNiO5>Fe2 O3。Ce0 .2 5FeNiO3的ε′和ε″的变化幅度大于其他几种纳米粉体。结果表明 ,加入稀土铈的铁氧体纳米粉体性能优于其他几种材料     

Synthesis and Characterization of CeO2 Nanoparticles via Solution Combustion Method for Photocatalytic and Antibacterial Activity Studies

CeO₂ nanoparticles have been proven to be competent photocatalysts for environmental applications because of their strong redox ability, nontoxicity, long-term stability, and low cost. We have synthesized CeO₂ nanoparticles via solution combustion method using ceric ammonium nitrate as an oxidizer and ethylenediaminetetraacetic acid (EDTA) as fuel at 450 °C. These nanoparticles exhibit good photocatalytic degradation and antibacterial activity. The obtained product was characterized by various techniques. X-ray diffraction data confirms a cerianite structure: a cubic phase CeO₂ having crystallite size of 35 nm. The infrared spectrum shows a strong band below 700 cm⁻¹ due to the Ce−O−Ce stretching vibrations. The UV/Vis spectrum shows maximum absorption at 302 nm. The photoluminescence spectrum shows characteristic peaks of CeO₂ nanoparticles. Scanning electron microscopy (SEM) images clearly show the presence of a porous network with a lot of voids. From transmission electron microscopy (TEM) images, it is clear that the particles are almost spherical, and the average size of the nanoparticles is found to be 42 nm. CeO₂ nanoparticles exhibit photocatalytic activity against trypan blue at pH 10 in UV light, and the reaction follows pseudo first-order kinetics. Finally, CeO₂ nanoparticles also reduce Cr^VI to Cr^III and show antibacterial activity against Pseudomonas aeruginosa.     

Magnetic Relaxation in Single‐Electron Single‐Ion Cerium(III) Magnets: Insights from Ab Initio Calculations

Detailed ab initio calculations were performed on two structurally different cerium(III) single‐molecule magnets (SMMs) to probe the origin of magnetic anisotropy and to understand the mechanism of magnetic relaxations. The complexes [Ce^III{Zn^II(L)}₂(MeOH)]BPh₄ ( 1 ) and [Li(dme)₃][Ce^III(cot′′)₂] ( 1 ; L=N,N,O,O‐tetradentate Schiff base ligand; 2 ; DME=dimethoxyethane, COT′′=1,4‐bis(trimethylsilyl)cyclooctatetraenyldianion), which are reported to be zero‐field and field‐induced SMMs with effective barrier heights of 21.2 and 30 K respectively, were chosen as examples. CASSCF+RASSI/SINGLE_ANISO calculations unequivocally suggest that m_J|±5/2〉 and |±1/2〉 are the ground states for complexes 1 and 2 , respectively. The origin of these differences is rooted back to the nature of the ligand field and the symmetry around the cerium(III) ions. Ab initio magnetisation blockade barriers constructed for complexes 1 and 2 expose a contrasting energy‐level pattern with significant quantum tunnelling of magnetisation between the ground state Kramers doublet in complex 2 . Calculations performed on several model complexes stress the need for a suitable ligand environment and high symmetry around the cerium(III) ions to obtain a large effective barrier.     

纳米氧化铈在催化氧化木质素制备芳香化合物中的应用研究

木质素是自然界中唯一大规模可再生的含芳环聚合物.通过催化氧化的方法,定向解聚木质素得到芳香类化合物,具有非常重要的价值.近年来,氧化铈作为载体在木质素的多相催化氧化反应中表现较好性能.然而,对于氧化铈直接作为催化剂,并探讨其纳米结构与性能之间的研究未见报道.研究结果表明:纳米氧化铈直接作为催化剂时,对于木质素的催化氧化反应具有较好的性能,顺序为氧化铈纳米八面体纳米四方体纳米球纳米棒.纳米八面体表现出最优的催化性能,以其作为催化剂,对乙醇木质素进行催化氧化,得到了大量芳香酸及其酯类化合物.     

Electronic and adsorption properties of Ce‐Ag layers

Silver has rarely been considered as the catalyst for CO oxidation, although it has been recognized to be very active in several partial oxidation reactions such as ethylene epoxidation and formaldehyde synthesis. It is generally believed that a metal support interaction plays an important role in catalytic processes. Therefore in our study, we examined electronic and adsorption properties of cerium deposited onto a polycrystalline silver substrate. Layers of approximately one monolayer of cerium deposited on a clean silver substrate were examined in situ using surface‐sensitive techniques—by XPS, ultraviolet photoelectron spectroscopy (UPS) and low energy ion scattering (LEIS). CO molecular adsorption was observed by UPS and LEIS; experimental results exhibited CO adsorption on Ce atoms sites. Oxygen adsorption on deposited layers led to a strong oxidation; stoichiometry of oxidized layers was given by amount of adsorbed oxygen and by temperature. Copyright © 2011 John Wiley & Sons, Ltd.     

改性ZrO2-MnO2基整体式催化剂上NH3选择性催化还原NO

采用共沉淀法制备了ZrO2-MnO2催化剂,考察了CeO2,MoO3和WO3的添加对ZrO2-MnO2整体式催化剂上NH3选择性催化还原(NH3-SCR)NOx的影响,并利用低温N2吸附-脱附、X射线衍射、X射线光电子能谱、NH3和NO程序升温脱附等方法对催化剂进行了表征,结果表明催化剂物相为Mn0.2Zr0.8O1....     

Synergistic effects of cerium phosphate and intumescent flame retardant on EPDM/PP composites

An intumescent flame retardant system composed of ammonium polyphosphate (APP) and pentaerythritol (PER) was used for flame retarding ethylene–propylene–diene‐modified elastomer (EPDM)/polypropylene (PP) blends. Cerium phosphate (CeP) was synthesized and the effect on flame retardancy and thermal stability of EPDM/PP composites based on intumescent flame retardant (IFR) were studied by limiting oxygen index (LOI), UL‐94, and thermogravimetic analysis (TGA), respectively. Scanning electron microscopy (SEM) and Fourier transform infrared spectrometry (FTIR) were used to analyze the morphological structure and the component of the residue chars formed from the EPDM/PP composites, and the mechanical properties of the materials were also studied. The addition of CeP to the EPDM/PP/APP/PER composites gives better flame retardancy than that of EPDM/PP/APP/PER composites. TGA and RT‐FTIR studies indicated that an interaction occurs among APP, PER, and EPDM/PP. The incorporation of CeP improved the mechanical properties of the materials. Copyright © 2010 John Wiley & Sons, Ltd.     

Manipulation of Single‐Stranded DNA by Using an Artificial Site‐Selective DNA Cutter Composed of Cerium(IV)/EDTA and Phosphonate–Oligonucleotide Conjugates

An artificial site‐selective DNA cutter to hydrolyze single‐stranded DNA at a desired site was prepared from Ce^IV/ethylenediamintetraacetic acid (EDTA) and two ethylenediamine‐N,N,N′,N′‐tetrakis(methylenephosphonic acid)–oligonucleotide conjugates. By using this cutter, the sense strand of a blue fluorescent protein (BFP) gene was selectively cut at a predetermined site in the chromophore‐coding region. The upstream fragment obtained by the site‐selective scission was ligated with the downstream fragment of the closely related green fluorescent protein (GFP) gene so that the 5′‐ and 3′‐end portions of the chromophore came from the BFP fragment and the GFP fragment, respectively. The recombinant gene was successfully expressed in E. coli and the chimeric chromophore emitted green fluorescence as expected.