Residual Stress And Deformation Analysis Of Anodic Bonded Multi-Layer Of Glass And Aluminum

The bonding of glass wafer to aluminum foils in multi-layer assemblies was made by the common anodic bonding process. The bonding was performed at temperatures in the range 350-450 degrees C and with an applied voltage in the range 400-700 V under a pressure of 0.05 MPa. Residual stress and deformation in samples of two-layer (aluminum/glass) and three-layer (glass/aluminum/glass) were analyzed by nonlinear finite element simulation software MARC. The stress and strain varying with cooling time were obtained. The analyzed results show that deformation of the three-layer sample is significantly smaller than that of the two-layer sample, because of the symmetric structure of the three-layer sample. This has an important advantage in MEMS fabrication. The maximum equivalent stresses locate in the transition layer in both samples, which will become weakness in bonded sample.

Nematic ordering pattern formation in the process of self-organization of microtubules in a gravitational field

Papaseit et al. (Proc. Nati. Acad. Sci. U.S.A. 97, 8364, 2000) showed the decisive role of gravity in the formation of patterns by assemblies of microtubules in vitro. By virtue of a functional scaling, the free energy for MT systems in a gravitational field was constructed. The influence of the gravitational field on MT's self-organization process, that can lead to the isotropic to nematic phase transition, is the focus of this paper. A coupling of a concentration gradient with orientational order characteristic of nernatic ordering pattern formation is the new feature emerging in the presence of gravity. The concentration range corresponding to a phase coexistence region increases with increasing g or NIT concentration. Gravity facilitates the isotropic to nernatic phase transition leading to a significantly broader transition region. The phase transition represents the interplay between the growth in the isotropic phase and the precipitation into the nematic phase. We also present and discuss the numerical results obtained for local NIT concentration change with the height of the vessel, order parameter and phase transition properties.

A microelectrode drive for long term recording of neurons in freely moving and chaired monkeys

An electrode drive is described for recordings of neurons in freely moving and chaired monkeys during the performance of behavioural tasks. The electrode drives are implanted for periods of up to 6 months, and can advance up to 42 electrodes using 14 independent drive mechanisms. The drive samples 288 points within a 12 mm x 12 min region, with 15 min of electrode travel. Major advantages are that recordings are made in freely moving monkeys, and these recordings can be compared with those in chaired experiments; waveforms of single neurons are stable, enabling prolonged recordings of the same neurons across periods of days; recordings can be made throughout the brain, including the dorsolateral prefrontal cortex and hippocampus; the drive accommodates both sharp microelectrodes and fine wire assemblies such as tetrodes. (C) 2003 Elsevier Science B.V; All rights reserved.

Al2O3 : Cr3+ nanotubes synthesized via homogenization precipitation followed by heat treatment

Cr3+-doped NH4Al(OH)(2)CO3 nanotubes, templated by surfactant assemblies, were successfully synthesized via the homogenization precipitation method, and various crystallographic phase Al2O3:Cr3+ nanotubes were also obtained by postannealing at different temperatures. The characteristic R-1, R-2 doublet line transitions of ruby can be observed in the high crystalline alpha-Al2O3 nanotubes calcined at temperatures higher than 1200 degrees C. The results also indicate that the formation mechanism of the tubular nanostructures should result from the self-rolling action of layered compound NH4Al(OH)(2)CO3 under the assistance of the surfactant soft-template. The convenient synthetic procedure, excellent reproducibility, clean reactions, high yield, and fine quality of products in this work make the present route attractive and significant. Aluminum oxide nanotubes with high specific surface area could be used as fabricating nanosized optical devices doped with different elements and stable catalyst supports of metal clusters.

Optical properties and electrical bistability of CdS nanoparticles synthesized in dodecanethiol

We reported the synthesis of CdS semiconductor nanoparticles using a simple one-pot reaction by thermolysis of cadmium acetylacetonate in dodecanethiol. Optical measurements of the as-obtained CdS nanoparticles revealed that their optical properties were closely related to surface effects. Based upon the cocktail of poly (N-vinylcarbazole) (PVK) and CdS nanoparticles, a bistable device was fabricated by a simple solution processing technique. Such a device exhibited a remarkable electrical bistability, which was attributed to the electric field-assisted charge transfer between PVK and the CdS nanoparticles capped by dodecaethiol. The conduction mechanism changed from an injection-controlled current to a bulk-controlled one during switching from OFF-state to ON-state.

可生物降解的两亲性嵌段共聚物的自聚集行为研究

可生物降解的两亲性嵌段共聚物PLA-PEG飞所制备的胶束或纳术粒子，作为潜在的药物控制释放体系弓！起人们广泛的兴趣。，方们授有寿比山于PEG链的空间位阴．效应可以避免单核噬菌体的吞噬，、并且可以通过控制可降解部分的降解行为实现药物的持续释放，使在微载体内所包载的药物分子持续释放出来。尽管高聚物的胶束和纳米粒子作为药物的胶体载体已作厂泛研究，但是对其本身物理化学性质与应用之间的联系研究甚少。因此本文对一系列PLLA和PEG两嵌段和三嵌段共聚物的自聚集行为进行了细致研究，得到了以卜结论：1．以花为"模型药物"，通过荧光探针技术对一系列两亲性共聚物在水呀招夜和NaCI溶液种的胶束化行为进行了研究。这些共聚物是由一种新型氨钙催化利，以人分J，的聚乙二醇（PEG）为引发剂，引发丙交酷开环聚合得到，，其中囚定长度阴 PEG段分剐为44，104和113环氧乙烷早兀，PLLA的长没在15-280乳酸中元之间。由于氨钙准活性的特点，这些共聚物的分散度较低，均在1.1-1.3之间。其临界胶束浓度cmc发现随PLLA的含量增加I荆氏。具有同一PEG长度的两嵌段和三嵌段共聚物cmc值的截然差别为它们胶束的构型不同提供了证据。同时也发现了NaCI的加入对丫EG段和争LLA段较短洪聚物的cmc的降低有明掀笋作用，而对具有较长PEG段或较长PLLA段的共聚物的cmc基本上没有什么影响。2．通过荧光探余十技术测定花在这一系列共聚物胶束溶液锄勺配分系数在0.2*10~5至1.9*10~5之间，对于同-PEG段的共聚物，花在其胶柬相中的配分系数随PLLA的含量的增加而增加。另外发现NaCl的加入能够促进花在胶束相中的配分。3．通过透射电子显微镜研究了两嵌段共聚物水溶液胶束的形貌，发现胶束的粒径和分散度均随PLLA段的增加而增加：通过原子力显微镜研究"这些纳米粒子退火前后的形貌变化，发现退火后纳米粒子重新自聚集为类似于神经网络红脚乏的"纳米条带"结构，其中心为类似"神经元"的团簇结构，而周困为支化的车由突"分支结构，这与文献上提到的只有三嵌段共聚物能够形成支化的"纳米条带"结构截然不同，其自聚集机理在进，步研究之中。4．以亲水性的荧光素为荧光探针研究了两嵌段共聚物在甲苯中的胶束化行为，发现其clnc值随PLLA段的含量增加而降低，相对于PEG段，PLLA段在其胶宋化过程中起主要作用。通过1HNMR证明两嵌段共聚物在甲苯中的胶束具伯以PLLA段为"核"、PEG段为"壳"的"核-壳"结构，这种胶柬化行为通过溶解度参数的差异进行了解释。5.通过原子力显微镜发现，当这些胶束滴加在云母表面上经过热处理后，这些胶束重新自聚集成为规则的具有平缓隆起的纳米结构，这与由水中得到的胶柬热处理后的形貌截然不同，并对此进行了进一步解释。由XPS分析认为主要是PEG段覆盖在PLLA段表面。

固体表面的分子组装体和纳米结构

本文评叙了分子组装体和纳米结构在固体表面的自组装及其应用，并对控制其自组装过程中的分子间作用力和表面力进行了介绍．采用扫描探针显微学结合电化学的方法对自组装膜（SAMs）、仿生膜（biomimetic mebane），金属和聚合物纳米颗粒（nanoparticles）等分子组装体系进行了研究。主要结果如下：(l)我们研究了2-巯基，-3-烷基唾吩（MOT）在金电极表面的自组装行为。测量了MOT膜的电容，结果表面MOT膜能够选择性的透过溶液中的探针物种。交流阻抗和欠电位沉积研究表明湘T膜的覆盖度达99.9%以上。在硫酸溶液中评价了MOT膜的稳定性，MOT膜的电位窗阳极极限为1.2V。次外，我们还研究了一系列有机小分子在MOT膜上的通透行为，实验结果显示于MOT膜的选择性透过能力最密切相关的是探针分子的溶剂化程度，溶剂化程度约高通过能力越差。我们进一步研究呢MOT膜与表面活性剂的相互作用，发现表面活性剂分子能够在MOT膜表面强烈的吸附，并使MOT膜对电极的封闭作用大大地增强。（2）我们在基于MOT的单组分和电活性多组分的自组膜上进一步构筑了杂化:仿生双层膜，并且研究了双层膜的形成对其中电活性物质的氧化还原反应热力学的影响。跟踪了该双层的形成动力学并研究了其界面属性。得到交叉构象的双层膜．研究了重组其中的HRP的电活性以及磷脂酶A2对该膜的水解动力学。证明我们得到的双层膜比基于烷基硫醇的双层膜有更好的稳定性，而且在仿生膜基础研究和生物传感器应用的有很好的应用前景。（3）我们在MOT和C10SH自组膜上利用表面力，憎水力和电泳力协同作用组装了电活性金纳米粒子。用伏安法跟踪了纳米粒子在界面成膜的过程。用扫描探针显微术对表面得到的纳米结构经行了研究。结果表面这些弱相互作用力协同作用可形成二维纳米结构的表面。(4)我们在单晶Au（111）表面制备了分子导线和长链烷基硫醇的混合自组装膜。以该自组装膜为模板，我们在其表面选择性的生长了聚苯胺纳米结构，这些纳米结构可以作为为阵列电极，而且具有开关特性；同时这些结构为研究分子导线的导电性质提供了一个理想平台。

两亲性三嵌段共聚物在选择性稀溶液中的自组装及应用

本论文主要研究了ABA和ABC型两亲性三嵌段共聚物在选择性稀溶液中的自组装行为，得到了多种形态新颖、结构复杂多样的胶束，研究了这些复杂胶束的形成过程，探讨了影响胶束形态的各种因素并通过适当的方法对胶束形态进行调控。研究了聚乙烯基毗陡（P4VP）／聚苯乙烯（PS）三嵌段共聚物P4VP-b-PS-b-P4VP在二氧六环／水中的自组装行为，成功得到了嵌段共聚物环状胶束，并通过实验研究了环状胶束的形成过程。结果表明，胶束形态依赖于退火时间的长短。随着退火时间的延长，胶束结构从棒状过渡到环形结构。以实验结果为基础提出了环状胶束形成的新的机理，即囊泡塌陷形成环。同时，通过改变实验条件还得到了一些新型的环状复合结构，如环套环形、鸟状、哑铃形、戒指形、网络状等结构，并得到了与计算机模拟一致的结果。通过不同的方法对ABA型三嵌段共聚物（P4VP-b-PS-b-P4VP）在选择性溶液中的自组装胶束形态进行调控：首先，详细研究了P4VP-b-PS-b-P4VP在不同的共溶剂中的自组装行为。结果表明通过单纯改变共溶剂的性质可以很方便地调节胶束的形态，得到了球、棒、囊泡等结构。并用混合溶剂的方法得到了长度和直径可控的纳米线胶束。同时，通过加入第二种选择性溶剂（核层嵌段PS的选择性溶剂甲苯）的方法使形成胶束的核层嵌段在胶核中的伸展程度增加，从而使胶束形态发生转变。其次，研究了加入表面活性剂十五烷基苯酚（PDP）以构建分子间氢键来调节P4VP-b-PS-b-P4VP的胶束形态。结果表明，通过调节PDP的加入量可以使胶束形态发生从球到棒，到网络状、再到囊泡结构的转变。通过实验对比系统地研究了PDP的加入对胶束形态转变的影响，提出了相应的形态转变机理。再次，研究了不同分子量的嵌段共聚物之间共混及共聚物与均聚物共混对胶束形态的影响。结果表明加入亲油嵌段的均聚物对共聚物胶束形态影响非常明显，胶束形态与加入的均聚物的分子量及加入量直接相关。同时得到了一些新形态的胶束，如海绵状、笼子状等。共聚物共混的研究结果表明：通过两种不同分子量的共聚物共混可以得到这两种共聚物胶束的过渡态结构。用共聚物混合的方法还可以得到一些具有生物模拟性的胶束结构，如乌贼状、章鱼状等。这加深了人们对囊泡的形成机理及各种胶束形态之间形态转变的认识。P4VP-b-PS-b-P4VP通过在二氧六环／水中的自组装形成了囊泡，结果表明囊泡的尺寸依赖于初始状态下共聚物在共溶剂中的浓度及退火时间。除得到常规的球形囊泡外，还得到一些非球形囊泡，如长条形、三角形、项链形等囊泡结构。结合计算机模拟的方法研究了囊泡的形成机理，发现这些不同结构的囊泡的形成是由于初始状态下密度涨落所引起的。研究了实验中经常出现的各种胶束形态共存现象的原因，发现体系中亚稳态的存在是多形态共存的重要原因之一。通过聚苯乙烯一左聚乙烯基毗睫一左聚氧乙烯（PS一b一PZVP一b一PEO）在THF／水中的二次自组装首次得到了一种具有生物模拟性的巨大的节状蠕虫胶束（SWM）。研究发现，SWM是由重复单元盘状结构和丝状结构相连组成的。最令人吃惊的是这种SWM与自然界中的一些生命体如蛆叫、蛹、昆虫类的幼虫结构非常相似。通过对SWM形成过程中的中间态胶束结构的深入研究发现SWM是由球形胶束通过二次自组装形成的。SWM的形成过程可以分为三个阶段：ABC三嵌段共聚物先组装形成球形结构；这些球型结构粘连在一起形成梭形的中间结构；这些梭状中间结构中的球经过重组和重新调整各嵌段的排布最终形成SWM。用所得到的嵌段共聚物胶束为模板，采用无电沉积的方法成功制备了各种形态的金属一有机高分子纳米复合材料。用简单的方法还得到了导电金属金一银的双金属纳米结构材料。这些纳米结构材料在微电子器件等领域有潜在应用价值。以上研究结果丰富了人们对嵌段共聚物在选择性介质中自组装行为的理解，为人们提供了对生物材料自组装本质的理解的依据。这在两亲性分子在溶液中自组装的基础研究方面以及基于这些自组装形态而构建结构及功能更复杂的纳米结构材料等方面都有一定的意义。

Fabrication of silicon-on-reflector for Si-based resonant-cavity-enhanced photodetectors

A novel silicon-on-reflector substrate for Si-based resonant-cavity-enhanced photodetectors has been fabricated by using Si-based sol-gel and smart-cut techniques. The Si/SiO2 Bragg reflector is controlled in situ by electron beam evaporation and the thickness can be adjusted to get high reflectivity. The reflectance spectra of the silicon-on-reflector substrate with five pairs of Si/SiO2 reflector have been measured and simulated by transfer matrix model. The reflectivity at operating wavelength is close to 100%. Based on the silicon-on-reflector substrate, SiGe/Si multiple quantum wells resonant-cavity-enhanced photodetectors for 1.3 mu m wavelength have been designed and simulated. Ten-fold enhancement of the quantum efficiency of resonant-cavity-enhanced photodetectors compared with conventional photodetectors is predicted.

苯乙酮、氨甲酸酯参与的直接Mannich反应

Mannich反应是有机化学中最重要的碳-碳键形成反应，其产物是合成手性胺的通用中间体。间接Mannich反应使用不稳定的预制烯醇等当体，以未修饰的酮为给体的直接方法将增强Mannich反应的效率。针对低活性苯乙酮、氨甲酸酯参与的直接Mannich反应，研究工作将更具挑战性。 在前期实验中，我们发现Lewis酸-NbCl5可高效催化苯乙酮、芳香醛、芳香胺三组分直接Mannich反应，反应在环境温度下进行，高收率获得Mannich碱。这是以苯乙酮参与的Mannich反应中，实现催化量Lewis酸催化的首次报道。该方法高效且操作简单。但就底物而言，对易去保护、低活性的氨甲酸酯类底物收率较低。我们设想Brønst酸可解决此类底物问题。令人高兴的是，杂多酸可高效催化芳香酮、芳香醛、氨甲酸酯三组分直接Mannich反应，反应在环境温度下进行，高收率获得N-保护的β-氨基酮。该方法底物范围广泛，普适性强且催化剂便宜。 基于杂多酸在苯乙酮、氨甲酸酯为底物直接Mannich反应中的高效性，我们设想杂多酸与功能化的手性有机小分子-手性伯胺组装可解决催化剂回收问题，同时实现不对称催化。实验结果表明，非共价键固载手性伯胺不能有效催化苯乙酮为底物的直接Mannich反应，无论是对映选择性还是收率均较低。随后，我们以丙二酸酯及α-氨基砜为底物，以增强底物活性，同时绕开亚胺的不稳定性。辛可宁伯胺以氢键双活化底物，有效催化原位产生氨甲酸酯类亚胺与丙二酸酯的Mannich反应，高收率获得Mannich碱，ee值中等。 我们采用逐步解决问题的策略解决Mannich反应中的部分问题并在Lewis酸催化、Brønst酸催化、非共价键固载手性伯胺催化及手性伯胺氢键催化的直接Mannich反应中做出了有益探索。 The Mannich reactions are among the most fundamental carbon-carbon bond forming reactions in organic chemistry, and the reaction products are versatile intermediates in the synthesis of chiral amines. The indirect Mannich reaction uses preformed enolate equivalents. However the preformed enolates are unstable. Thus, a direct methodology based on unmodified ketone donors would enhance the efficiency of the Mannich reaction. Especially researches for the directed Mannich reactions of acetophenone, carbamate, which own lower activities, will be more challengeable. In the initial experiments, we found an efficient Lewis acid-NbCl5 which could catalyze three-component Mannich-type reaction of acetophenone, aromatic aldehydes and aromatic amines at ambient temperature in high yields. This is the first report that use catalytic amount of Lewis acid in the Mannich reactions of .acetophenone. The method reported is not only simple to operate but also efficient. However, as far as amines are concerned, the substrates of carbamates which can be deprotected more easily and less reactive than amines give low yields. We envisaged that Brønsted acid would resolve this problem. Pleasingly, heteropoly acids (HPA) efficiently catalyzed one-pot three-component Mannich reactions of aryl aldehydes, aryl ketones, and carbamates at ambient temperature and afforded the corresponding N-protected β-amino ketones in good to excellent yields. This method provides a novel and improved modification of three-component Mannich reactions in terms of a wide scope of aldehydes, ketones and carbamates, economic viability. Based on the high efficiency of heteropoly acids in the Mannich reaction of acetophenone and carbamates, we envisaged that if HPA were combined with functionalized chiral organocatalysts–chiral primary amines the assemblies may be able to act as recoverable asymmetric organocatalysts. The results of exprimentals showed that noncovalently supported heterogeneous chiral primary amine couldn’t effectively catalyze the Mannich reactions which own two the substrate of acetophenone regardless of enantioselectivity and yield. Then, we employed malonates and α-amido sulfones as substrates to enhance reactivity of substrates and circumvent the instability of imines. A moderately enantioselective and highly yield Mannich reaction with in situ generation of carbamate-protected imines from stable α-amido sulfones catalyzed by cinchonine primary amine catalyst was developed. It is noteworthy that cinchonine primary amine can dual activate substrates through H-bond activation and thus promote the reaction. We applied step-by-step-strategy to resolve some problems in the Mannich reactions and did some instructive explorations in Lewis acid catalysis, Brønst acid catalysis, noncovalently supported heterogeneous chiral primary amine catalysis and chiral primary amine as hydrogen-bond catalysis.

Fabrication of a miniature twin-fuel-cell on silicon wafer

The fabrication and performance evaluation of a miniature twin-fuel-cell on silicon wafers are presented in this paper. The miniature twin-fuel-cell was fabricated in series using two membrane-electrode-assemblies sandwiched between two silicon substrates in which electric current, reactant, and product flow. The novel structure of the miniature twin-fuel-cell is that the electricity interconnect from the cathode of one cell to the anode of another cell is made on the same plane. The interconnect was fabricated by sputtering a layer of copper over a layer of gold on the top of the silicon wafer. Silicon dioxide was deposited on the silicon wafer adjacent to the copper layer to prevent short-circuiting between the twin cells. The feed holes and channels in the silicon wafers were prepared by anisotropic silicon etching from the back and front of the wafer with silicon dioxide acting as intrinsic etch-stop layer. Operating on dry H-2/O-2 at 25 degreesC and atmospheric pressure, the measured peak power density was 190.4 mW/cm(2) at 270 mA/cm(2) for the miniature twin-fuel-cell using a Nafion 112 membrane. Based on the polarization curves of the twin-fuel-cell and the two single cells, the interconnect resistance between the twin cells was calculated to be in the range from 0.0113 Omega (at 10 mA/cm(2)) to 0.0150 Omega (at 300 mA/cm(2)), which is relatively low. (C) 2003 Elsevier Science Ltd. All rights reserved.

Synthesis and luminescence properties of hybrid organic-inorganic transparent titania thin film activated by in-situ formed lanthanide complexes

Stable transparent titania thin films were fabricated at room temperature by combining thenoyltrifluoroacetone (TTFA)-modified titanium precursors with amphiphilic triblock poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (PEO-PPO-PEO, P123) copolymers. The obtained transparent titania thin films were systematically investigated by IR spectroscopy, PL emission and excitation spectroscopy and transmission electron microscopy. IR spectroscopy indicates that TTFA coordinates the titanium center during the process of hydrolysis and condensation. Luminescence spectroscopy confirms the in-situ formation of lanthanide complexes in the transparent titania thin film.

Synthesis and micellization of star-like hyperbranched polymer with poly(ethylene oxide) and Poly(epsilon-caprolactone) arms

Novel star-like hyperbranched polymers with amphiphilic arms were synthesized via three steps. Hyperbranched poly(amido amine)s containing secondary amine and hydroxyl groups were successfully synthesized via Michael addition polymerization of triacrylamide (TT) and 3-amino-1,2-propanediol (APD) with feed molar ratio of 1:2. H-1, C-13, and HSQC NMR techniques were used to clarify polymerization mechanism and the structures of the resultant hyperbranched polymers