Friction and Wear Studies of Octadecyltrichlorosilane SAM on Silicon

A self-assembled monolayer of octadecyltrichlorosilane (OTS) was prepared on a single-crystal silicon wafer (111) and its tribological properties were examined with a one-way reciprocating tribometer. The worn surfaces and transfer film on the counterface were analyzed by means of scanning electron microscopy and X-ray photoelectron spectroscopy. The results show that, due to the wear of the OTS monolayer and the formation of the transfer film on the counterpart ball, the friction coefficient gradually increases from 0.06 to 0.13 with increasing sliding cycles and then keeps stable at a normal load of 0.5N. The transfer film is characterized by deposition, accumulation, and spalling at extended test duration. Though low friction coefficients of the monolayer in sliding against steel or ceramic counterfaces are recorded, poor load-carrying capacity and antiwear ability are also shown. Moreover, the monolayer itself or the corresponding transfer film on the counterface fails to lubricate even at a normal load of 1.0 N. Thus, the self-assembled monolayer of octadecyltrichlorosilane can be a potential boundary lubricant only at very low loads.

利用自组装单分子层(SAM)研究细胞和表面的相互作用

研究细胞和表面相互作用具有重要意义 ,利用长链的烷硫醇在金表面或烷基硅烷在羟基化表面形成的自组装单分子层及其微格式化的表面允许以分子水平研究并控制细胞和表面的相互作用。我们概述了自组装单分子层及其格式化表面研究细胞和表面相互作用的最新进展

Molecular weight effects on the phase morphology of PS/P4VP blend films on homogeneous SAM and heterogeneous SAM/Au substrates

The effects of the molecular weight of polystyrene (PS) component on the phase separation of PS/poly(4-vinylpyridine) (PS/P4VP) blend films on homogeneous alkanethiol self-assembled monolayer (SAM) and heterogeneous SAM/Au substrates have been investigated by means of atomic force microscopy (AFM). For the PS (22.4k)/P4VP (60k) system, owing to the molecular weight of PS component is relatively small, the well-aligned PS and P4VP stripes with good thermal stability are directed by the patterned SAM/Au surfaces. With the increase of the molecular weight of PS component (for the PS (582k)/P4VP (60k) system), the diffusion of P4VP is hindered by the high viscosity of PS during the fast spin-coating process. The phase separation behavior of PS/P4VP on the SAM/Au patterned substrates is similar to that on the homoueneous SAM and cannot be easily directed by the patterned SAM surfaces even though the characteristic length of the lateral domain morphology is commensurate with the stripe width.

Selective penetration of liquid-phase organic probe molecules into SAM of 2-mercapto-3-n-octylthiophene

An inherently disorganized self-assembled monolayer (SAM) of 2-mercapto-3-n-octylthiophene (MOT) has been formed on a gold bead electrode from its dilute ethanolic solution. The disorganization of the monolayer is attributed to the loose packing of the aliphatic chains of the MOT adsorbates, which results from a large difference in dimension/or cross-sectional area between the head (thiophene thiolate) and the tail (alkane chain) groups. Electrochemical measurements including ac impedance spectroscopy and metal underpotential deposition have shown that the monolayer is almost pinhole free. However, the MOT SAM can be penetrated by an organic probe molecule with affinity for the alkane chain part of the monolayer. Some typical probe molecules with different size and hydrophilicity have been employed to assess the permselectivity of the monolayer. Measurement results demonstrate that the ability of the employed probe molecules to penetrate into the monoalyer is mainly dominated by their hydrophilicity/or hydrophobicity. The results presented here suggest the potential application of MOT monoalyer to effectively modify the electrode surface for several research areas such as electrochemical sensors, electrocatalysis, electroanalysis, and supported hybrid bilayer membranes.

Determination of surface pK(a) of SAM using an electrochemical titration method

A self-assembled monolayer (SAM) of 3-mercaptopropionic acid (HSCH2CH2COOH) was formed on a gold electrode. The effect of the charge of the end group on the electrochemical response of Fe(CN)(6)(3-) at the SAM modified electrode was studied by using cyclic voltammetry. At high pH, when the -COOH groups are dissociated, Fe(CN)(6)(3-) current is suppressed; as the solution pH is lowered, Fe(CN)(6)(3-) current increases. The electrochemical titration curve was obtained by correlating the currents to the different electrolyte pH values, from which the surface pK(a) was obtained to be 5.2+/-0.1. Furthermore, a calculation equation was presented to simulate the electrochemical titration. As comparison, the surface pK(a) was also measured by contact angle titration as 5.6+/-0.1. The surface pK(a) values determined by the two methods in our work are consistent and accurate.

Stiction and Anti-Stiction in Mems and Nems

Stiction in microelectromechanical systems (MEMS) has been a major failure mode ever since the advent of surface micromachining in the 80s of the last century due to large surface-area-to-volume ratio. Even now when solutions to this problem are emerging, such as self-assembled monolayer (SAM) and other measures, stiction remains one of the most catastrophic failure modes in MEMS. A review is presented in this paper on stiction and anti-stiction in MEMS and nanoelectromechanical systems (NEMS). First, some new experimental observations of stiction in radio frequency (RF) MEMS switch and micromachined accelerometers are presented. Second, some criteria for stiction of microstructures in MEMS and NEMS due to surface forces (such as capillary, electrostatic, van der Waals, Casimir forces, etc.) are reviewed. The influence of surface roughness and environmental conditions (relative humidity and temperature) on stiction are also discussed. As hydrophobic films, the self-assembled monolayers (SAMs) turn out able to prevent release-related stiction effectively. The anti-stiction of SAMs in MEMS is reviewed in the last part.

Immunosensor Interface Based on Physical and Chemical Immunogylobulin G Adsorption onto Mixed Self-Assembled Monolayers

An immunosensor interface based on mixed hydrophobic self-assembled monolayers (SAMs) of methyl and carboxylic acid terminated thiols with covalently attached human Immunoglobulin G (hIgG), is investigated. The densely packed and organised SAMs were characterised by contact angle measurements and cyclic voltammetry. The effect of the non-ionic surfactant, Tween 20, in preventing nonspecific adsorption is addressed by ellipsometry during physical and covalent hIgG immobilization on pure and mixed SAMs, respectively. It is clearly demonstrated that nonspecific adsorption due to hydrophobic interactions of hIgG on methyl ended groups is totally inhibited, whereas electrostatic/hydrogen bonding interactions with the exposed carboxylic groups prevail in the presence of surfactant. Results of ellipsometry and Atomic Force Microscopy, reveal that the surface concentration of covalently immobilized hIgG is determined by the ratio of COOH/CH3-terminated thiols in SAM forming solution. Moreover, the ellipsometric data demonstrates that the ratio of bound anti-hIgG/hIgG depends on the density of hIgG on the surface and that the highest ratio is close to three. We also report the selectivity and high sensitivity achieved by chronoamperometry in the detection of adsorbed hIgG and the reaction with its antibody.

光学蛋白质芯片关键技术研究及生物医学应用

蛋白质芯片，又称蛋白质微阵列，是继基因芯片之后又一对生物医学研究乃至人类健康具有重大应用价值的生物芯片。目前，蛋白质芯片的发展还处于初级阶段，还没有真正走出基因芯片的阴影，在蛋白质芯片的制作和检测中借用了很多基因芯片技术。许多在基因芯片上没有解决的问题，如低丰度信号的检测、不同的点样质量带来的干扰和基于标记方法的检测技术问题，也同样在蛋白质芯片上出现，并表现得更为突出，主要原因在于蛋白质分子与DNA分子之间的巨大差异。基于椭偏光学成像技术的无标记光学蛋白质芯片技术的提出正是为了解决目前蛋白质芯片发展中存在的一些问题。椭偏光学成像技术是近来发展起来的一种新型的光学检测技术，目前国际上尚未发展出适合于其检测特点的蛋白质芯片技术。本文研究的无标记光学蛋白质芯片是多学科高度交叉的生物技术，它主要包含五方面的内容：（1）芯片设计；（2）配基装配；（3）芯片反应器；（4）芯片信号采样和处理；（5）芯片数据库。本文的研究工作集中在前三部分内容，创新性主要表现在以下几方面：研制了微流道蛋白质芯片系统；建立了高通量蛋白质芯片制备方法；发展了多种芯片表面改性和配基固定方法；开展了无标记光学蛋白质芯片在生物医学领域的应用。本文研制了微流道蛋白质芯片系统，建立了化学格式化法高通量蛋白质芯片制备方法。通过这两种方法制备的蛋白质芯片能够满足椭偏光学成像技术定量检测的要求，而且这两种蛋白质芯片与本实验室早期发展的生物活性探针和多元蛋白质芯片结合在一起形成了较为完整的无标记光学蛋白质芯片系列，使之不但能够简单方便地进行低通量蛋白质检测，而且也具有了高通量蛋白质分析的能力。本文建立的微流道蛋白质芯片系统把微流控芯片和微阵列芯片二者的优势结合在一起，以微型流动控制见长的微流控芯片被设计成微阵列芯片的微型点样仪与微型高效率反应器，而以并行分析见长的微阵列芯片成为微流道系统的专用传感器件，并且实现了在同一微型分析系统中进行蛋白质芯片的制备与检测。微流道蛋白质芯片系统改变了阵列式生物芯片整体反应模式，使得芯片的使用更加灵活方便。通过微流道蛋白质芯片系统进行蛋白质芯片制备与检测，显著降低了试剂和样品的消耗，缩短了检测时间，把检测灵敏度提高到了纳克／毫升量级。能够多次重复使用的微流道蛋白质芯片系统，使得蛋白质芯片的使用成本大幅度降低。本文针对椭偏光学成像技术的检测特点、不同的芯片设计和配基发展了多种表面改性及配基固定技术，实现了配基分子共价连接、抗体分子定向固定、混合硅烷膜层对硅基底的表面改性以及混合烷硫醇SAM对金基底的表面改性。这些技术的使用明显提高了配基分子在蛋白质芯片表面上的稳定性，较好地保持了配基分子的生物活性，从而大幅度提高了无标记光学蛋白质芯片的检测灵敏度。本文在上述关键技术发展的基础上，还成功地开展了无标记蛋白质芯片在生物医学领域的应用。实现了在一块蛋白质芯片上进行乙肝五项指标同时检测；通过蛋白质芯片对病毒一噬菌体进行了直接检测；乙肝表面抗原检测和乳腺癌标志物定量检测已经能够达到临床免疫检测的水平；还通过无标记蛋白质芯片技术同时研究了多对生物分子之间的相互作用，并通过模型化分析获得了相互作用动力学常数。

Bicaudal-C基因的分子特征和生物学功能

某些蛋白翻译水平的激活和抑制对胚胎发育过程中基因表达起到重要的时空调节作用.在果蝇中,Bicaudal-c(dBic-C)基因产物被认为是一种能与RNA结合的蛋白质分子,并对转录后水平具有重要的调节作用.dBic-C基因的突变会导致果蝇缺失头部结构和重复的尾部结构,故而命名为双尾-C基因.后来又在多个不同物种(如线虫、爪蟾、小鼠)中发现dBic-C的同源基因,并且这些同源基因的蛋白质产物高度保守.小鼠的Bicaudal-C基因(Biccl)定位于10号染色体的C1区域,其蛋白质N端含有KH结构域,用于介导蛋白质与RNA的相瓦作用;C端的SAM结构域则在蛋白质与蛋白质相互结合中发挥作用.目前已发现3种与Biccl基因相关的小鼠突变体模型jcpk、bpk和67Gso,这些小鼠突变体中Biccl基因在不同位点发生突变,产生异常的蛋白质产物,结果导致小鼠肾脏发生胞囊化,并且影响身体其他器官的正常形态及功能,病理表型特征与人类的多囊肾病(polycystic kidney disease,PKD)极为相似.本文通过总结和同顾Bicaudal-C基因研究的成果和进展,揭示该基因在生物体发育和器官形成中的作用,为深入研究这一基因的生物学功能奠定基础.

四川美姑、汉源黑颈鹤迁徙停歇地环境调查

Eight Black-necked Cranes(Grus nigricollis)were banded with satellite transmitters in the spring of 2005 and 2006 at Dashanbao in Yunnan and Caohai in Guizhou.Six of the banded cranes completed at least one migration between their wintering and breeding grounds.Townships where these birds stopped over include:Wusihe,Henan,Nimei,Liyuan,Yidong,Sanjiaoping,and Huangmu in Hanyuan County,and Liuhong,Yiguojie,Nongzuo,Lamuajue,Bingtu,Wagu,Equgulongmen,and Niha in Meigu County.We surveyed stop-over sites in Hanyuan...

High average power and short pulse duration continuous wave mode-locked Nd : GdVO4 laser with a semiconductor absorber mirror

Passive mode locking of a solid-state Nd:GdVO4 laser is demonstrated. The laser is mode locked by use of a semiconductor absorber mirror (SAM). A low Nd3+ doped Nd:GdVO4 crystal is used to mitigate the thermal lens effect of the laser crystal at a high pump power. The maximum average output power is up to 6.5 W, and the pulse duration is as short as 6.2 ps. The optic-to-optic conversion efficiency is 32.5% and the repetition rate is about 110 MHz.

High-average-power and high-conversion-efficiency continuous wave mode-locked Nd : YVO4 laser with a semiconductor absorber mirror

A high-power continuous wave (cw) mode-locked Nd:YVO4 solid-state laser was demonstrated by use of a semiconductor absorber mirror (SAM). The maximum average output power was 8.1 W and the optic-to-optic conversion efficiency was about 41 %. At the maximum incident pump power, the pulse width was about 8.6 ps and the repetition rate was 130 MHz. Experimental results indicated that this absorber was suitable for high power mode-locked solid-state lasers. (C) 2006 Elsevier Ltd. All rights reserved.

多金属氧酸盐的分子材料——多金属氧酸盐及其相关氧化物的薄膜和超薄膜

具有特殊的物理性质(尤其是具有光、电、磁性质)的分子材料(如分子金属、分子铁磁体)是材料化学的一个新兴的领域，这些分子材料所显示出来的协同性质使其在超导体、磁性材料以及非线性光学材料等方面极具开发性质。自从1826年Berzelius合成了第一个杂多酸12-钼磷酸铵(NH_4)_3PMo_(12)O_(40)·nH_2O，多金属氧酸盐化学至今已有一百多年的历史，它是无机化学中的一个重要研究领域。古老的多金属氧酸盐化学，经历百余年的变化、发展，现已进入了一个崭新的时代：多金属氧酸盐化学的理论研究方面取得了重要的进展，由于X-射线结晶学的硬件和软件及ESR、NMR等表面分析谱学手段的发展和精细的电化学方法的应用，对多酸的溶液、固体及表面化学性质方面有了进一步的认识，金属-氧簇(Metal-Oxygen cluster)、多金属氧酸盐化学(polyoxometalate chemistry)被更多的人们研究和采用的研究；多金属氧酸盐的合成己进入了分子剪裁和组装，从对稳定氧化态物质的合成、研究进入亚稳态和变价化合物及超分子化合物的研究，纳米结构和高聚合度多金属氧酸阴离子、夹心式多金属氧酸多阴离子、链式有机金属多金属氧酸盐及具有空半球结构的多金属氧酸阴离子的研究正方兴未艾；多金属氧酸盐化学的应用除催化领域外，现己跻身于材料科学和药物化学等领域，它的发展无疑会为人类提供一类新的、具有光、电、磁功能材料和一系列抗艾滋病、抗肿瘤、抗病毒药物。多金属氧酸盐是一类金属-氧簇化合物，一般呈笼型结构，是一类优良的受体分子，它可以与无机、有机分子、离子等结合成超分子化合物，因而很适合作为上述有机．无机复合材料中的无机组分。多金属氧酸盐的有机-无机复合材料是八十年代末，九十年代初国际上刚刚起步的工作，作为一类新型的电。磁、非线性光学材料极具开发性质。本论文以多金属氧酸盐的分子材料的制备这一前沿领域为主要研究方向，具体地研究了多金属氧酸盐的有序的有机／无机复合膜及其相关氧化物薄膜材料的制备，联用多种技术(特别是电化学技术，也包括扫描探针显微镜等在内的表面分析技术)系统深入地表征了下述薄膜材料。1.多金属氧酸阴离子一硫醇自组膜(SAM)复合膜的制备与表征。2．多金属氧酸盐LB膜的制备与表征。3．三维有序的硅钨阴离子的单层膜和多层膜的制备与表征。4．非化学计量混合价态氧化钼膜(VI，V)的制备与表征。5．过渡金属取代的多金属氧酸盐的电化学和电催化性质。

纳米功能界面的电化学和扫描探针显微镜（SPM）研究

本文简要评述了扫描探针显微学研究的发展过程、目前状况及发展方向，着重介绍了扫描探针显微学(SPM)在分子组装体研究中的一些应用。采用扫描探针显微学结合电化学的方法对自组装膜(SAMs)、纳米颗粒(nanoparticles)、有机无机纳米复合材料(composite material)体系进行了研究，并结合XPS、SEC等多种手段对分子组装体在电极表面的形态和结构进行了探讨。主要结果如下：1．STM研究金属纳米颗粒的隧道成像机理利用柠檬酸三钠还原高氯酸金的反应制备了金的溶胶纳米粒子。将对氨基硫酚自组于金单晶面(Au(111))上形成致密有序的单层；并以此为基底进一步将金溶胶纳米粒子组装于自组膜表面，得到固定化纳米粒子的次单层。用扫描隧道显微镜进行了表征，对金溶胶纳米粒子隧道成像的微观机理作了探讨，提出双势垒隧穿的电子传输界面模型。对扫描隧道显微镜下金溶胶纳米粒子的图像失真作解释。2．共轭有机小分子的导电性的研究利用保护和去保护的方法对带巯基的共轭有机小分子进行了合理地操纵，使其稳定性在我们构筑电化学界面的过程中得到了保证。我们用自组装(SAM)技术将这种共轭有机小分子首先吸附于金电表面，然后用稀氨水将其水解得到致密的共轭有机小分子的单层。在金/SAM二次基底的基础上利用巯基于金的强烈的化学键合力用电化学沉积的方法和湿化学还原的方法得到的金纳米粒子组装于电极表面，得到了金/有机分子层/金的夹心结构，并对构筑这种夹心结构的每一步骤用扫描探针显微镜(SPM)和电化学循环伏安法(CV)进行了表征，实验结果表明，此种共轭有机小分子利用巯基化学键合金属金时，电子能够快速通过这种夹心结构，为分子电子学中之基本问题“分子导线”连接纳米级的分子器件时电子能否在其间传导给出了直接的电化学证明。3．纳米复合材料的合成与表征我们用相转移方法合成了表面功能化的纳米粒子。首先，根据将HAuCl_4溶解于水相中，将Bu_4NClO_4作为相转移试剂、带巯基的有机小分子作为表面修饰剂，NaBH_4和柠檬蒜三钠作为还原剂溶解于硝基苯有机相中。将两相剧烈混合，在混合过程中HAuCl_4在水/硝基苯界面处被有机相中的还原剂还原成金属纳米粒子，刚生成的纳米粒子由于强烈的金硫键合作用而被带巯基的有机小分子表面功能化，而且能在有机溶剂中稳定存在。于是得到的表面功能化的纳米粒子在有机溶剂中的稳定胶体溶液。我们合成了表面被12烷基硫醇和巯基噻酚修饰的金纳米粒子。基于这些表面功能化且带有电化学反应性功能基团的纳米粒子，我们在电化学合成聚噻酚的系统中加入这种具有表面反应性的纳米粒子得到了有机/无机纳米复合材料。对这种复合材料我们用扫描探针显微镜(SPM)、电化学交流阻抗谱(ElS)、X-射线光电子能谱(XPS)进行了表征，结果表面纳米粒子能稳定存在于聚合物基体中，而且这种复合材料的电子传输性能远远大于同等条件下的聚合物膜。