多酸-介孔分子筛复合材料的制备、表征及光催化活性

采用浸渍法将具有光催化活性的多金属氧酸盐(polyoxometalate,POM)磷钨酸和硅钨酸负载到介孔分子筛MCM-41,制备了H3PW12O40/MCM-41和H4SiW12O40/MCM-41两种复合材料,以红外光谱(FT-IR)、X射线衍射(XRD)、N2吸附、高分辨透射电镜(HRTEM)等分析手段对所合成的多酸-分子筛复合材料进行了表征,并以农药百草枯的光催化降解考察了复合材料的光催化活性。所合成的复合材料同时保留了母体多酸的Keggin特征结构和载体MCM-41分子筛均匀的六方孔道结构,比表面积超过200m2.g-1。用于农药百草枯的光催化降解实验表明,两种复合材料均具有较高的光催化活性。在365nm紫外光辐照下,以H3PW12O40/MCM-41和H4SiW12O40/MCM-41为催化剂催化反应14h后,百草枯(10mg.L-1)的降解转化率分别达到92.0%和87.6%,反应符合一级化学动力学模型,半衰期分别为3.7和4.6h。     

MCM-41负载磷钨酸的制备与表征

以十六烷基三甲基溴化铵(CTAB)为表面活性剂,以正硅酸乙酯(TEOS)为硅源,采用水热合成法制备了介孔分子筛MCM-41,并利用浸渍法将磷钨酸(HPW)负载在MCM-41分子筛上,得到HPW/MCM-41催化剂f采用X射线衍射、傅里叶变换红外光谱、透射电镜等手段对负载型催化剂进行了表征.结果表明,磷钨酸负载到MCM-...     

ZnO/MCM-41复合材料的制备及其光谱性质

以硅酸钠(NaSiO3·9H2O)为硅源,三甲基十六烷基溴化铵(CTAB)为模板剂在碱性条件下水热合成介孔分子筛MCM-41,然后以其为主体,采用锌盐浸渍-灼烧的方法.在介孔分子筛MCM-41上负载了氧化锌(ZnO)纳米微粒,并通过扫描电子显微镜,红外光谱(1R).紫外可见吸收光谱(UV-Vis),N2-吸附脱附和荧光光谱等手段对产品进行了系列表征.结果表明,分子筛平均直径约为1.7μm,对不同温度下灼烧后得到的ZnO/MCM-41组装体的光谱性质进行研究表明介孔分子筛MCM-41的尺寸所限,制备出的ZnO粒子粒径小于2 nm.量子尺寸效应使得ZnO/MCM-41组装体中的ZnO纳米粒子的紫外可见吸收光谱及荧光光谱均发生蓝移.通过红外光谱分析得知ZnO负载到MCM-41上并没有改变介孔分子筛原有的骨架结构.     

HPA/MCM-48对水溶性染料的光催化降解

采用浸渍法制备了MCM-48分子筛负载硅钨酸催化剂(HPA/MCM-48),通过红外光谱的方法对试样进行了表征;以紫外灯为光源,研究了HPA/MCM-48对亚甲基蓝、甲基紫、罗丹明B等3种水溶液的光催化脱色性能;讨论了催化剂用量、反应时间等因素对甲基紫降解效果的影响。实验结果表明HPA/MCM-48对染料的最佳催化条件为,10mg/L染料在紫外灯照射下,催化剂用量1.67g/L,光照时间2h;其对甲基紫的降解效果优于对亚甲基蓝和罗丹明B。     

荧光光谱法研究左氧氟沙星与MCM-41的相互作用

采用微波辅助水热法制备介孔分子筛MCM-41,并用浸渍法将左氧氟沙星(LVFX)组装在MCM-41均一的六方形孔道中,制备出新型载药复合物LVFX/MCM-41。用粉末X射线衍射(XRD)、低温氮吸附、傅里叶变换红外光谱(FTIR)及差热-热重(TGA-DTA)分析对MCM-41以及LVFX/ MCM-41复合物进行表征,合成的介孔分子筛MCM-41的孔径为2.382 nm,比表面积为1 015 m2·g-1。对MCM-41、LVFX/MCM-41、LVFX(固态)及LVFX(溶液)的荧光光谱研究结果显示,LVFX/MCM-41的荧光光谱比组装前发生明显红移,表明MCM-41孔道内表面的羟基和LVFX形成氢键,羟基上的电子云向LVFX分子上的吸电子基团转移;同时MCM-41和LVFX之间形成新环,使电子云能在更大的环上移动,药物分子的共轭体系扩大,荧光光谱峰红移。MCM-41与左氧氟沙星之间强的相互作用为研发以MCM-41为载体的新型释药系统提供了理论依据。     

H_3PW_(12)O_(40)/La-N-TiO_2复合催化剂可见光下光催化降解吡虫啉研究(英文)

制备出H3PW12O40/La-N-TiO2催化剂并采用红外光谱,N2吸附-脱附分析,透射电镜和紫外漫反射进行结构表征。红外光谱检测表明,复合催化剂中H3PW12O40保留了Keggin结构;掺杂La-N之后,复合催化剂的BET比表面积是母体TiO2的两倍;透射电镜检测表明,催化剂由相对均匀的球形颗粒组成,分散性良好;紫外漫反射检测表明,掺杂La和N元素后所制备的复合催化剂对可将光的光响应性能明显提高。对吡虫啉的光催化实验表明,所制备的不同负载量催化剂中30%H3PW12O40/0.3%La-1.0%N-TiO2具有最好的光催化活性(≥400nm),光照3h后吡虫啉降解率为91.57%,光照6h后吡虫啉降解率达98.89%,基本上完全降解。     

Ni_2P/介孔分子筛催化剂的原位漫反射红外光谱研究

以介孔分子筛MCM-41,MCM-48,SBA-15,SBA-16为载体,硝酸镍为镍源,磷酸氢二铵为磷源,通过浸渍法制备了含有磷化镍前体的介孔分子筛样品,然后在氢气气氛中进行程序升温还原,得到了磷化镍/介孔分子筛催化剂.采用原位漫反射红外光谱法,用CO作为探针分子,对样品的吸附特征进行了研究.结果表明,在介孔分子筛表面CO存在着较弱的物理吸附.在Ni2P/MCM-41催化剂样品表面有四种CO的吸附态:(1)在2055cm-1处形成的Ni(CO)4物种的吸附,(2)在2 091cm-1处的配位不饱和Niδ(0<δ<1)物种上的吸附,(3)在2 127 cm-1处的Ni+物种上的吸附,(4)在2 198～2 202 cm-1范围内的P物种上的吸附.在Ni2P/MCM-48,Ni2P/SBA-15,Ni2P/SBAZ-16催化剂样品表面有二种CO的吸附态:在2 051～2 055cm-1处的Ni(CO)4吸附和在2 093～2 096 cm-1处的配位不饱和Niδ+(0<δ<1)物种上的吸附.     

(纳米MCM-41)-CdS主-客体复合材料的制备及光学性质

以水热法制备了纳米微粒MCM-41分子筛，通过离子交换法将Cd(II)交换到分子筛中，然后采用硫代乙酰胺作硫化氢前驱体对(MCM-41)-Cd进行硫化，制备出主-客体复合材料(MCM-41)-CdS．化学分析表明，客体成功地组装到分子筛中．粉末X射线衍射结果表明，组装过程并未破坏所制备的主-客体材料中分子筛的骨架，分子筛骨架完整且结晶度仍然很高．红外光谱表明所制备材料骨架保持完好．低温N2吸附-解吸附研究表明，相对于MCM-41分子筛主体所制备的复合材料孔体积、孔尺寸及比表面积降低，表明客体在分子筛孔道内组装成功．制备的主-客体复合材料固体扩散漫反射吸收光谱相对于CdS体相呈现某些蓝移，说明客体处于分子筛孔道内，也表明分子筛主体对纳米硫化镉客体表现出明显的立体限域效应．(纳米MCM-41)-CdS及(微米MCM-41)-CdS样品呈现明显发光．     

TiO2/5A光催化降解水中CN-的催化活性

采用溶胶-凝胶-浸渍法制备TiO2/5A型催化剂,以其对水样中CN-降解率的大小来评价催化剂的光催化活性,并与P25型纳米TiO2催化效果作比较,从而探讨5A型分子筛负载纳米TiO2的百分含量、催化剂加入量、水样的pH值及CN-初始浓度对TiO2/5A光催化降解水中CN-催化活性的影响.结果表明:5A型分子筛负载纳米TiO2的量为20％、加入量为1.5g/L、pH=10、CN-初始浓度为50mg/L,反应时间为3h时,降解率达88.64％,且优于P25型纳米TiO2的降解效果.     

超声波酸性体系下MCM-41的合成及表征

以十六烷基三甲基溴化铵(CTAB)为模板剂,正硅酸乙酯(TEOS)为硅源,以超声波为辅助手段于酸性介质中制备出了MCM-41介孔分子筛,采用XRD、TEM、FTIR等手段对样品进行了分析表征.结果表明,所合成样品具备MCM-41所特有的六方排列的一维孔道结构和较高的有序度,所合成的MCM-41平均粒径为11nm,孔径约为2.7nm.     

Optical spectroscopy of Ca3Sc2Si3O12, Ca3Y2Si3O12 and Ca3Lu2Si3O12 doped with Pr

The silicates Ca₃Sc₂Si₃O₁₂, Ca₃Y₂Si₃O₁₂ and Ca₃Lu₂Si₃O₁₂, both undoped and doped with Pr³⁺ ions, have been synthesized by solid-state reaction at high temperature. The luminescence spectroscopy and the excited state dynamics of the materials have been studied upon VUV and X-ray excitation using synchrotron radiation. All doped samples have shown efficient 5d-4f emission upon direct VUV excitation of 5d levels, but only Ca₃Sc₂Si₃O₁₂:Pr³⁺ shows luminescence upon interband VUV or X-ray excitation. The VUV excited emission spectra of Ca₃Y₂Si₃O₁₂:Pr³⁺ and Ca₃Lu₂Si₃O₁₂:Pr³⁺ show features attributed to emission from two distinct sites accommodating the Pr³⁺ dopant. The decay kinetics of the Pr³⁺ 5d-4f emission in Ca₃Sc₂Si₃O₁₂:Pr³⁺ upon VUV excitation across the band gap are characterized by decay times in the range 25-28 ns with no significant rise after the excitation pulse. They appear to be faster upon X-ray irradiation than for VUV excitation. Weak afterglow components are attributed to defect luminescence.     

合成反铁磁Ni81Fe19/Co90Fe10/Ru/Co90Fe10/Ni81Fe19的研究

采用直流磁控溅射方法制备了一系列的合成反铁磁及以其为自由层的自旋阀.研究发现,在Ni₈₁Fe₁₉与Ru层之间插入适当厚度的Co₉₀Fe₁₀层后,可有效地提高合成反铁磁两磁性层间的反铁磁耦合强度,得到具有饱和场H_s更高、饱和磁化强度M_s更低、热稳定性更好的合成反铁磁.另外,以这种合成反铁磁作自旋阀的自由层时,可有效提高自旋阀的稳定性. 关键词： 合成反铁磁 退火 自旋阀     

La0.67Ca0.33MnO3薄膜皮秒光电效应

在1064 nm波长脉冲激光（脉宽25 ps）的照射下，钙钛矿氧化物薄膜La0.67Ca0.33MnO3/SrTiO3具有超快光电效应，对激光脉冲显示ps量级的响应时间，上升沿响应时间300 ps，半高宽700 ps，同时，对激光能量的响应灵敏度为500 mV/mJ。     

X-ray study of phase transitions in the system of solid solutions K2Pb4Nb10O30-Na2Pb4Nb10O30-K6W4Nb6O30

Boundaries of morphotropic phase transitions region in the system of solid solutions K₂Pb₄Nb₁₀O₃₀-Na₂Pb₄Nb₁₀O₃₀-K₆W₄Nb₆O₃₀ with the structure of the tetragonal tungsten bronze have been specified. Presence of the second morphotropic phase transition, perpendicular to the first one has been revealed. The temperature dependences of the structural parameters of some compounds have been investigated. The compounds with high values of Curie temperatures and working temperatures have been obtained.     

Study of dielectric and magnetic properties of PbZr0.52Ti0.48O3-Mn0.3Co0.6Zn0.4Fe1.7O4 composite

Results of detailed structural, dielectric, magnetic and magnetoelectric studies of (x)PbZr_0.52Ti_0.48O₃-(1−x)Mn_0.3Co_0.6Zn_0.4Fe_1.7O₄ composites where x=65, 70, 75 and 80 are shown in this work. Manganese substituted cobalt ferrites are known to exhibit large strain derivative (dx/dH) and on the other hand substitution of Zn in pure cobalt ferrite is known to enhance its permeability μ and permittivity ε. The choice of ferrite as Mn, Zn simultaneously substituted cobalt ferrite (MCZFO) is made keeping in view that for good magnetoelectric (ME) voltage coefficient the magnetostrictive constituent phase of the composite should have large strain derivative (dx/dH) along with large permittivity and permeability. It is shown here that although the dielectric transition temperature changes significantly with change in the mole ratio of the two component phases, magnetic transition temperature (much less compared to the bulk cobalt ferrite) is relatively non-responsive to the changing molar ratio of the two component phases. In the vicinity of the magnetic transition temperature we observed an anomaly in tan δ vs. T plots, which indicates a possible magnetoelectric coupling in the samples. Magnetoelectric voltage coefficient (α_E) has been measured using static magnetoelectric method. Highest magnetoelectric voltage coefficient (α_E=0.312 mV/cmOe) is obtained for sample 80:20 at H_DC=1000 Oe.     

Appearance of an inhomogeneous superconducting state in La0.67Sr0.33MnO3-YBa2Cu3O7-La0.67Sr0.33MnO3 trilayers

An experimental study of proximity effect in La_0.67Sr_0.33MnO₃-YBa₂CU₃O₇-La_0.67Sr_0.33MnO₃ trilayers is reported. Transport measurements on these samples show clear oscillations in critical current (I _c) as the thickness of La_0.67Sr_0.33MnO₃ layers (d _F) is scanned from ∼50 ? to ∼ 1100 ?. In the light of existing theories of ferromagnet-superconductor (FM-SC) heterostructures, this observation suggests a long range proximity effect in the manganite, modulated by its weak exchange energy (∼2 meV). The observed modulation of the magnetic coupling between the ferromagnetic LSMO layers as a function of d _F, also suggests an oscillatory behavior of the SC order parameter near the FM-SC interface.      

Phase formation and characterization of Sr3Y2Ge3O12, Sr3In2Ge3O12, and Ca3Ga2Ge3O12 doped by trivalent europium

This work reports on the phase formation during a solid-state reaction of Eu³⁺-doped garnets with the general formula A₃B₂Ge₃O₁₂ (A=Ca, Sr and B=Ga, In, Y) and their luminescent properties. It is shown by XRD and DTA/TG experiments that the garnet-phase formation is completed at 1100-1200 °C. Moreover, it turned out that the position of the oxygen to europium charge-transfer band and the intensity of the forbidden 4f-4f transitions of Eu³⁺ is dependent on the covalent interaction between the Eu³⁺ activator and the surrounding oxygen anions. The investigated red-emitting luminescent materials show high lumen equivalents and deep red emission at the same time, which makes them attractive for the application in LEDs (light emitting diodes), in particular for near UV-emitting LEDs.     

Magnetotransport properties of La0.67Ca0.33MnO3//La0.67Sr0.33MnO3 bilayers

The perovskite bilayers La0.67Ca0.33MnO3 （LCMO） （100 nm） / La0.67Sr0.33MnO3（LSMO） （100 nm） and LSMO （100 nm） / LCMO （100 nm） are fabricated by a facing-target sputtering technique. Their transport and magnetic properties are investigated. It is found that the transport properties between them are different obviously due to distinguishable structures, and the different lattice strains in both films result in the difference of metal-to-insulator transition. Only single-step magnetization loop appears in our bilayers from 5K to 320K, and the coercive force of LSMO/LCMO varies irregularly with a minimum ～ 2387A/m which is lower than that of LCMO and LSMO single layer films. The behaviour is explained by some magnetic coupling.     

Analysis of FTIR spectra of CH2BrCl; the ν4 and ν5 fundamentals and their hot-bands ν4+ν6−ν6 and ν5+ν6−ν6

The infrared spectrum of isotopically pure CH₂⁷⁹BrCl has been recorded at a resolution of 0.0023 cm⁻¹ (FWHM) in the range 550-800 cm⁻¹ with a Bruker IFS 120 HR Fourier transform spectrometer in Wuppertal. Here we report the full rotational analysis of the ν₄ and ν₅ fundamentals and of the hot-bands ν₄+ν₆−ν₆ and ν₅+ν₆−ν₆. Ground state combination differences were constructed for all bands, yielding improved ground state constants, up to quartic terms, as well as reliable rotational constants for the ν₄, ν₅, and ν₆ states.     

Curie temperatures of Y3Fe5O12/Gd3Fe5O12 superlattices

The magneto-optical Kerr effects (MOKE) of epitaxial Y₃Fe₅O₁₂/Gd₃Ga₅O₁₂ (YIG/GGG) garnet superlattices grown on (1 1 1)GGG previously by pulsed laser deposition (PLD) were measured. A series of superlattices were investigated with the thickness of the ferrimagnetic YIG layer varied from six unit cells to only one unit cell while keeping the Curie paramagnetic GGG fixed at one unit cell. It was demonstrated that the ellipsometric technique employing photoelastic modulators (PEM) is sensitive enough to measure the MOKE signals of these ultrathin oxide samples. The Curie temperatures, determined by MOKE, are fit with a power law, yielding a shift exponent λ = 3.1 ± 1.2.