分子筛组装单质半导体碲的拉曼光谱

无机介孔材料MCM41是高有序,直孔道介孔分子筛,具有孔径约4nm的一维均匀孔道,孔壁厚约1nm,介孔体积可达40%,是一种很理想的组装材料主体。半导体碲位于第Ⅵ族,其六方相的晶格排列呈螺旋链状结构。本文采用固相合成反应方法,将单质半导体碲成功地组装在MCM41介孔分子筛中。在组装体中,单质半导体碲保持着六方相的晶体结构,其拉曼晶体振动表现出纳米晶体的结构特征。真空热处理实验表明,组装体具有良好的热稳定性。Te的六方相和所具有的独特的螺旋链状结构使Te分子很容易进入MCM41的直孔道内,同时MCM41均匀而规则的直孔道限制了Te螺旋链的随机排列,因而被组装在直孔道内的Te能螺旋链式生长,形成一维半导体纳米晶体,排列均匀,尺寸单一,具有稳定的空间构型     

罗丹明6G/MCM-41纳米复合物的发光蓝移

介孔分子筛MCM-41具有规则排列的纳米量级的孔道，可以作为宿主封装其他材料。利用这一性质，将激光染料罗丹明6G分子封装在介孔分子筛MCM-41中形成了纳米复合物。用透射电镜、小角度X射线衍射和荧光光谱等方法对纳米复合物的性质进行了分析。用波长为480nm的光对纳米复合物进行激发，得到的发光峰为531nm。与无限稀罗丹明6G乙醇溶液的发光峰相比，这一发光峰有15nm的蓝移和明显的宽化。我们认为当罗丹明6G分子封装在MCM-41的介孔中时，罗丹明6G分子与介孔分子筛孔道表面分子之间存在较强的相互作用(包括氢键、静电吸引等)，导致电子云被局域在具有较强吸引力的分子筛表面原子周围。引起激发态能量升高，发光峰蓝移。     

MD模拟研究含金属离子的MCM41对水的吸附

本文采用MD模拟研究了分别含有Al3 , Cu2 和La3 等金属离子的中孔分子筛MCM41在较大温度范围内对水的吸附情况,通过考察水分子在孔内的局部平均密度分布,发现含有Al3 和La3 的MCM41对水有较好的吸附性能,表现在吸附量提高和脱附温度降低。我们认为其吸附性能提高的主要原因在于引入金属离子导致了壁面极性增加,增加了吸附表面的活性点,改变了壁面分子结构等几个方面。     

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.     

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.     

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。     

有机-无机杂化材料Eu(BA)3-MCM-41的制备及光学性质

将稀土有机配合物Eu(BA)3组装进介孔MCM-41中,得到有机-无机杂化介孔材料Eu(BA)3-MCM-41。采用XRD、IR、激发、发射光谱等测试方法对其结构和性能进行了分析。结果表明,组装体保持了有序的介孔骨架结构,由组装体IR谱图中波数3451cm-1吸收峰的消失及970cm-1吸收峰强度的降低可知,介孔中Eu(BA)3的引入使得配合物自身含有的结晶水、MCM-41中的吸附水和羟基数目减少,由于Eu(BA)3与—OH在介孔孔道中成键使羟基减少,降低了Eu3 的发光猝灭效应,提高了Eu3 的发光效率。组装体中主客体之间存在较强的相互作用,MCM-41的存在使Eu(BA)3对激发光有更强吸收,且使Eu(BA)3-MCM-41的发光强度较Eu(BA)3有显著的提高。     

介孔分子筛Al-MCM-41的合成与催化异构化性能

采用正硅酸乙酯(TEOS)为硅源,九水硝酸铝为铝源,十六烷基三甲基溴化胺(CTMABr)为模板剂,在室温条件下合成了介孔Al-MCM-41分子筛.通过XRD、N2等温吸附、SEM、FTIR等分析测试手段表征了分子筛的介孔结构和表面性质.结果表明所合成的分子筛有良好的介孔结构和较高的有序度,并且有较高的比表面积(达到816 m2·g-1)和窄的孔径分布.采用程序升温的焙烧方式、凝胶Al/Si比最大范围控制在0.06～0.13有利于合成高度有序的介孔Al-MCM-41分子筛.评价结果表明,所合成的Al-MCM-41分子筛对桥式四氢双环戊二烯(endo-TCD)异构化反应合成挂式异构体exo-TCD及金刚烷具有较高的催化活性和极高的选择性.     

(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．     

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-...     

多芯片组件技术在航天光学遥感器中的应用

目前我国的光学遥感器的总体技术指标与国际先进水平还有较大差距,遥感图像的质量还比较低,大大制约了卫星遥感图像的应用发展。介绍了Multi-chip Module多芯片组件(MCM),它是20世纪90年代以来发展较快的一种先进混合集成电路技术,是实现电子装备小型化轻量化高速度高可靠低成本电路集成不可缺少的关键技术,此项技术在航天光学遥感器上的应用必将使中国的航天光学遥感器的研制水平提高到一个更高层次,使我国的航天遥感技术进入国际先进行列。     

pH‐induced reorientation of microperoxidase‐11 in mesoporous molecular sieves

The resonance Raman spectra of microperoxidase‐11 loaded into the siliceous materials MCM‐41 and SBA‐15 demonstrate a pH dependence indicative of a protonation event on the substrate. An unusual change in relative Raman intensities without a shift in wavenumbers is observed upon lowering the system pH. Protonation of the silica surface is suggested to induce a reorientation of the MP‐11 fragments within the silica framework. Copyright © 2006 John Wiley & Sons, Ltd.     

Method of the magnetic field synthesis on the axis of cylinder solenoid

The paper presents the magnetic field synthesis on a solenoid axis for the case the problem is described a Fredholm integral equation of the first kind. Solution of the problem, which is ill-posed according to Hadamard, was obtained by means of the regularization method.     

Synthesis and characterization of Ni magnetic nanoparticles in AlMCM41 host

Superparamagnetic nickel nanoparticles were prepared by incorporating nickel ion into AlMCM41 as a nanoreactor and then reduced with sodium borohydride or H₂ gas. Products were characterized by elemental analysis, transmission electron microscopy, X-ray powder diffraction, and magnetic susceptibility. The nickel particle size and blocking temperature depend on the reduction method.     

On the contactless suspension of objects by electric and magnetic fields

In connection with the contactless suspension of objects by electric and magnetic fields, an electrodynamical version of Kapitza's theorem on the stabilizing influence of a rapidly oscillating field is deduced.     

On the theory of electron motion due to superposed em waves and its application to the free-electron laser with linear polarization

The relativistic motion of a charged particle in an electromagnetic field depending only on one coordinate is shown to be exactly equivalent to the unidimensional motion of a particle having a time and space-varying mass. By means of the averaged Lagrangian method an approximate solution is obtained for the relativistic electron motion in two oppositely moving waves of any polarization, one of them being weaker than the other one, thus generalizing the results previously obtained for circular polarization. A comparison with numerical calculations shows a good agreement. A pendulum-like motion in an effective periodic potential is shown to exist not only for two waves of the same frequency, but more generally when the frequency of the weaker wave is an odd harmonic of the frequency of the stronger one.This research was supported in part by CNR and the Italian Ministry of Education     

Scattering and absorption by a thin,finite dielectric cylinder

This work investigates and interprets the volume and surface integral equation formulations relevant to the scattering and absorption of electromagnetic waves by thin, finite and lossy dielectric cylinders. Computational data are presented, describing the effective current distributions and the scattered and absorbed power for widely varying electromagnetic and geometrical parameters.     

The influence of surface and volume effects on the light diffraction by SAW at parallel interfaces

The paper deals with the results of numerical calculations and experiments concerned with the contribution, due to the surface rippling and fluctuations of the refractive index in the layer closest to the surface, to the light diffraction by surface acoustic waves (SAW). The analysis includes all basic types and geometries of parallel interaction taking as an example DADP crystals.