硅基底上图形化自组装膜的构筑

为在硅基底上得到不同化学基团修饰的图形,采用传统的光刻技术与自组装相结合的方法,成功地制备了由甲基与氨基末端官能团组成的图形化自组装膜。将图形化自组装膜泡入碳纳米管DMF(N,N-二甲基甲酰胺)分散液中,图形化自组装膜的氨基区域能均匀吸附一层分散液中碳纳米管,而甲基没有,表明图形化自组装膜的不同自组装膜区域的不同表面性质,证实了该方法的可行性。     

自组装C60分子膜的微观摩擦行为

利用端基带－NH2的氨基酸自组装单分子膜与C60烯键反应形成共价键制成C60自组装膜，用原子力显微镜（AFM）研究了膜的微观摩擦学性能，结果表明，长链羟酸／C60分子膜的摩擦学性能优于短链羧酸分子膜；羧酸／C60分子膜的碳链中极性基团如羧基的存在，可以提高膜的平整度，改善膜的摩擦学性能。     

硅表面自组装膜的构建及其摩擦学性能研究进展

总结了目前在单晶硅表面构建的几类典型的分子自组装膜,并着重介绍了近十几年里各类自组装膜在摩擦学性能研究方面所取得的进展.单层膜能够有效降低硅基底的摩擦系数,但是其承载能力和抗磨损性能较差,其中较为典型的是OTS(十八烷基三氯硅烷)自组装膜;有机双层膜和多层膜的出现,一定程度上改善了单层膜的承载能力和耐磨性,但膜的有序性和稳定性还有待于进一步的提高;近年来,有机/无机复合膜的研究为改善硅表面的摩擦学性能提供了一条新的途径,有望成为今后该领域研究的一个重要方向.     

基于激光加工和自组装技术硅基底超疏水表面的制备

利用激光在硅基底上加工具有规则点阵结构的表面纹理,采用自组装技术在此硅表面制备全氟辛烷基三氯硅烷自组装分子膜。采用扫描电子显微镜和表面形貌仪对硅试样表面进行形貌分析,采用接触角测量仪测量试样的接触角。结果表明,激光加工后的硅试样表面纹理深度和表面粗糙度均随激光加工间距的增加而逐渐变大,试样表面的去除量随光照时间的增加而增大。通过激光加工和沉积自组装分子膜,硅试样表面的水接触角显著增大,最大可达到156°,且试样的水接触角随激光加工间距的减少而增大。试样接触角测量值与Cassie模型预测值相一致,当点阵直径与加工间距比0.510时,硅试样表面为超疏水表面。     

磁头表面含氟三氯硅烷自组装膜的生长机理

在磁头表面制备了1H,1H,2H,2H-四氢全氟辛烷基三氯硅烷（FOTS）自组装膜,采用X射线光电子能谱仪（XPS）、时间飞行二次离子质谱仪（TOF-SIMS）、接触角测量仪和原子力显微镜（AFM）对FOTS自组装膜进行表征,研究了自组装膜的生长机理．结果表明,FOTS自组装膜的生长经过了亚单层膜的低等覆盖,亚单层膜的中等覆盖、团聚和聚结四个阶段．其中第一层和第二层自组装膜的亚单层膜形态和生长方式不同,第一层的亚单层膜呈岛状,岛的生长是自身向外扩展;第二层的亚单层膜呈簇状,簇通过效量增加来实现生长．超薄完整的单层FOTS自组装膜（膜厚为0．8nm、Ra为0．125nm）能使磁头表面的接触角值增加,疏水性能提高．     

可反应表面修饰银纳米微粒的制备及组装

合成了功能化的修饰剂双11-十一烯基二硫代磷酸,以此为修饰剂,NaBH4还原可溶性银盐的水溶液制得了功能化的银纳米微粒,并通过氢化硅氢化反应组装银纳米颗粒薄膜。采用透射电子显微镜（TEM）、紫外-可见吸收光谱（UV-Vis）、傅立叶红外吸收光谱（FT-IR）、原子力显微镜（AFM）和X-光电子能谱（XPS）对所制的纳米微粒及组装的薄膜进行形态和结构表征,结果表明：银纳米颗粒为球形,无团聚现象,纳米微粒表面带有可反应的C=C双键不饱和官能团;组装后纳米微粒团聚长大,是通过Si-C键与基底结合。     

钛金属薄膜上两种短链自组装分子膜的制备与摩擦特性

采用自组装技术在钛金属薄膜上制备了两种分子链长相同、官能团不同的自组装分子膜,并对其进行了不同时间的紫外照射,对钛金属薄膜和自组装分子膜进行了表征和摩擦特性测试,研究了紫外照射、官能团、滑动速度和载荷对自组装分子膜摩擦特性的影响,结果表明:通过紫外照射钛金属薄膜表面羟基化、自组装分子水解及自组装分子缩合可在钛金属薄膜上制备结构致密的自组装分子膜,制备的两种短链自组装分子膜可降低钛金属薄膜的摩擦特性,APS自组装分子膜的摩擦特性优于MPS自组装分子膜的摩擦特性,紫外照射5 min的自组装分子膜表面吸附的有机杂质被蒸发掉,对针尖的黏着力减小,从而导致针尖的变形减小,摩擦力最低,而紫外照射15 min的自组装分子膜致密的网状结构被破坏,减弱了自组装分子膜的润滑效应,两种自组装分子膜的摩擦力随着滑动速度的增加略呈上升趋势,随着载荷的增加略呈下降趋势,但是变化不大.     

疏水性硅烷复合膜修饰的铜合金表面的防腐性能

采用自组装方法,在铜合金表面首先制备了6-（3-三乙氧基硅基丙基）氨-1,3,5-三嗪-2,4-二硫醇单钠盐（TES）自组装薄膜,然后用正辛基三甲氧基硅烷（OTES）或十六烷基三甲氧基硅烷（HDTMS）对TES修饰的铜合金表面进行硅烷化处理,得到了具有疏水功能的复合自组装薄膜。通过傅里叶变换红外光谱（FT—IR）、接触角、循环伏安、极化曲线和扫描电子显微镜（SEM）对铜合金表面的自组装薄膜进行了表征。结果表明,与未处理的铜合金相比,经复合自组装薄膜修饰的铜合金表面接触角由89．4°上升到123．7°,提高了铜合金表面的疏水性;FT—IR表明了复合自组装薄膜在铜合金表面的形成;SEM测定结果表明该方法成功地在铜合金表面获得均匀致密的有机硅烷复合膜;循环伏安及极化曲线测试均表明了该复合膜有效地提高了铜合金的耐腐蚀能力。     

铁离子敏感膜的自组装制备及光学性能测试

根据静电自组装原理,采用聚二烯丙基二甲基氯化铵(PDDA)和聚4-苯乙烯基磺酸钠(PSS)制备了自组装膜,考察了膜层自组装过程中的吸光度变化。并通过添加Fe3+指示剂磺基水杨酸的方法,利用PDDA、PSS自组装体系,制备了具有铁离子敏感性的自组装膜。试验结果表明,所制备的敏感膜完整、均匀。光学性能测试表明,所制备的敏感膜在不同浓度铁离子溶液中的吸光度变化与铁离子浓度具有较好的对应关系。     

氨基硅油和羧基硅油自组装超分子膜形貌及成膜性

以氨基硅油（ASO）和羧基硅油（CAS）为构筑基元,在乙酸乙酯溶液中自组装形成超分子聚集体ASO/CAS。以单晶硅和棉纤维织物作载膜基质,用原子力显微镜（AFM）、场发射扫描电镜（FESEM）和X射线光电子能谱（XPS）等对ASO/CAS的成膜性及膜形貌进行研究。结果表明,ASO/CAS在单晶硅上形成的膜微观形貌呈规则...     

Preparation and tribological studies of self-assembled triple-layer films

A self-assembled triple-layer film was grafted onto a silicon surface with a simple three-step method. Firstly, 3-glycidoxypropyltrimethoxysilane molecules were self-assembled on silicon surfaces, then coupled to 3-aminopropyltriethoxysilane through a surface ring-opening reaction, and finally octadecyltrichlorosilane (OTS) molecules were attached to the resultant alkoxysilane-terminated surface via Si-O-Si bonds. The structure and morphology of this triple-layer film were characterized with various techniques, such as contact angle measurement, ellipsometry, X-ray photoelectron spectroscopy, and atomic force microscopy (AFM). The influence of different surface chemical groups on surface adhesion properties was identified using the AFM force-volume technique. The micro- and macro-tribological properties of the triple-layer film were evaluated by friction force microscopy and a ball-on-plate tribometer. The triple-layer film shows good adhesive resistance and can greatly reduce the micro- and macro-friction force. Moreover, compared to self-assembled monolayer of OTS, this triple-layer film exhibited much better wear-resistance. This improvement was mainly ascribed to the network structure of a lateral cross-linked polysiloxane layer formed within the film which can enhance the stability of the film.     

Tribological characteristics of self-assembled nanometer film deposited on phosphorylated 3-aminopropyltriethoxysilane

Thin films deposited on the phosphonate 3-aminopropyltriethoxysilane (APTES) self-assembled monolayer (SAM) were prepared on the hydroxylated silicon substrate by a self-assembling process from specially formulated solution. Chemical compositions of the films and chemical state of the elements were detected by X-ray photoelectron spectrometry (XPS). The thickness of the films was determined with an ellipsometer, while the morphologies and nanotribological properties of the samples were analyzed by means of atomic force microscopy (AFM). As the results, the target film was obtained and reaction might have taken place between the thin films and the silicon substrate. It was also found that the thin films showed the lowest friction and adhesion followed by APTES-SAM and phosphorylated APTES-SAM, whereas silicon substrate showed high friction and adhesion. Microscale scratch/wear studies clearly showed that thin films were much more scratch/wear-resistant than the other samples. The superior friction reduction and scratch/wear resistance of thin films may be attributed to low work of adhesion of nonpolar terminal groups and the strong bonding strength between the films and the substrate.     

Determination of the ionization state of 11-thioundecyl-1-phosphonic acid in self-assembled monolayers by chemical force microscopy

The present article describes the preparation and preliminary characterization of a novel phosphate-functionalized self-assembled monolayer (SAM) and the determination of the surface ionization states of the phosphate headgroup in aqueous solutions by chemical force microscopy (CFM). The phosphate headgroup used was PO(OH)2, a diprotic acid. The adhesion force between an AFM probe and a flat substrate, both of which were chemically modified with the same phosphate SAM, was also measured as a function of pH and ionic strength. At low ionic strength (10(-4) M), two peaks were observed in the force titration curve (adhesion force versus pH) at pH 4.5 and 8.4. The two peaks are positioned 2.4 and 1.2 pH units higher, respectively, than the acid dissociation constants obtained for the phosphate group free in aqueous solution. At high ionic strength (10(-1) M), the adhesion forces were reduced by 1 order of magnitude and the peaks were replaced by shoulders similar to those previously reported for acid force titrations. On the basis of JKR theory, the surface pKa values of the phosphate group in high ionic strength solutions were found to be 4.5 and 7.7, respectively. However, in light of the effects of ionic strength on the force titration curves, we discuss the applicability of JKR theory to nanoscopic measurements of adhesion force and surface pKa.     

Optical properties of an octadecylphosphonic acid self-assembled monolayer on a silicon wafer

We report a study of a full-coverage octadecylphosphonic acid (OPA or ODPA) self-assembled monolayer (SAM) spin-coated on the native oxide layer (SiO₂) of a single crystalline silicon (c-Si) wafer using spectroscopic ellipsometry (SE) and reflectometry (SR). The OPA SAM showed characteristics of being a dielectric film in visible range and becoming absorbing in deep-UV range. By assuming an optical stack model of OPA/SiO₂/c-Si for the OPA monolayer system and adopting the parameterized Tauc-Lorentz dispersion model, we obtained an excellent fit of the model to the SE and SR data, from which dispersion of optical functions as well as thickness of the OPA film were deduced. The OPA film thickness measured by atomic force microscopy (AFM) on partial coverage OPA samples was used as the initial trial film thickness in the fitting processes. The deduced OPA film thickness from SE and SR data fitting was in good agreement with that obtained by AFM.     

In-situ examination of the selective etching of an alkanethiol monolayer covered Au{111} surface

An examination of the selective etching mechanism of a 1-alkanethiol self-assembled monolayer (SAM) covered Au{111} surface using in-situ atomic force microscopy (AFM) and molecular resolution scanning tunnelling microscopy (STM) is presented. The monolayer self-assembles on a smooth Au{111} surface and typically contains nanoscale non-uniformities such as pinholes, domain boundaries and monatomic depressions. During etching in a ferri/ferrocyanide water-based etchant, selective and preferential etching occurs at SAM covered Au(111) terrace and step edges where a lower SAM packing density is observed, resulting in triangular islands being relieved. The triangular islands are commensurate with the Au(111) lattice with their long edges parallel to its [11¯0] direction. Thus, SAM etching is selective and preferential attack is localized to defects and step edges at sites of high molecular density contrast.     

Silicon micro/nanofabrication using metastable helium atom beam lithography

We utilize metastable helium (He*) atom beam lithography to pattern silicon substrates by using self-assembled monolayer (SAM) of octadecyltrichlorosilane (OTS) grown directly on silicon surface as resist. An improved wet-chemical etching method was used to transfer the resist pattern into silicon substrate. Negative and positive pattern formations with well-defined edges were observed for silicon(100) substrate with SAM after exposure to the He* atom beam followed by the etching. Results indicate a clear transition from positive to negative patterns relies on the He* dosage. The pattern sizes on silicon were successfully decreased to the order of 100 nm, even less than 50 nm.     

Functionalization of silicon dioxide surface with 3-aminopropyltrimethoxysilane for fullerene C60 immobilization

Formation of self-assembled monolayers (SAM) of 3-aminopropyltrimethoxysilane (APTMS), chemically bonded to silicon dioxide surface, using a new solvent free process, has been studied by contact angle measurements, ellipsometry, ATR-FTIR spectroscopy and AFM imaging. The possibility of using as-obtained APTMS SAMs for anchoring functional molecular moieties is then studied with fullerene C60. In a first part we have analyzed the grafting kinetics of APTMS SAMs in order to control the formation of a single monolayer. Results show that about four hours are needed to obtain a complete APTMS single monolayer. In parallel, the ordering kinetics of the SAM has been monitored by ATR-FTIR spectroscopy, showing that the monolayer reaches its final order before grafting. We show that those APTMS SAMs can be used to graft C60 molecules deposited from a solution and forming about one monolayer anchored on amine terminal moieties. Such results could help paving the way to the preparation of hybrid C60-based molecular devices on silicon through a bottom-up approach.     

Characterization of nanostructured surfaces generated by reconstitution of the porin MspA from Mycobacterium smegmatis

Nanostructures with long-term stability at the surface of gold electrodes are generated by reconstituting the porin MspA from Mycobacterium smegmatis into a specially designed monolayer of long-chain lipid surfactant on gold. Tailored surface coverage of gold electrodes with long-chain surfactants is achieved by electrochemically assisted deposition of organic thiosulfates (Bunte salts). The subsequent reconstitution of the octameric-pore MspA is guided by its extraordinary self-assembling properties. Importantly, electrochemical reduction of copper(II) yields copper nanoparticles within the MspA nanopores. Electrochemical impedance spectroscopy, reflection electron microscopy, and atomic force microscopy (AFM) show that: 1) the MspA pores within the self-assembled monolayer (SAM) are monodisperse and electrochemically active, 2) MspA reconstitutes in SAMs and with a 10-nm thickness, 3) AFM is a suitable method to detect pores within SAMs, and 4) the electrochemical reduction of Cu2+ to Cu0 under overpotential conditions starts within the MspA pores.     

A three-layer model of self-assembly induced surface-energy variation experimentally extracted by using nanomechanically sensitive cantilevers

This research is aimed at elucidating surface-energy (or interfacial energy) variation during the process of molecule-layer self-assembly on a solid surface. A quasi-quantitative plotting model is proposed and established to distinguish the surface-energy variation contributed by the three characteristic layers of a thiol-on-gold self-assembled monolayer (SAM), namely the assembly-medium correlative gold/head-group layer, the chain/chain interaction layer and the tail/medium layer, respectively. The data for building the model are experimentally extracted from a set of correlative thiol self-assemblies in different media. The variation in surface-energy during self-assembly is obtained by in situ recording of the self-assembly induced nanomechanical surface-stress using integrated micro-cantilever sensors. Based on the correlative self-assembly experiment, and by using the nanomechanically sensitive self-sensing cantilevers to monitor the self-assembly induced surface-stressin situ, the experimentally extracted separate contributions of the three layers to the overall surface-energy change aid a comprehensive understanding of the self-assembly mechanism. Moreover, the quasi-quantitative modeling method is helpful for optimal design, molecule synthesis and performance evaluation of molecule self-assembly for application-specific surface functionalization.     

Nano-tribological characteristics of TiO<Subscript>2</Subscript> films on 3-mercaptopropyl trimethoxysilane sulfonated self-assembled monolayer

Silane coupling reagent (3-mercaptopropyl trimethoxysilane (MPTS)) was used to prepare twodimensional self-assembled monolayer (SAM) on silicon substrate. The terminal -SH group was in situ oxidized to −SO₃H group to endow the film with good chemisorption ability. Then TiO₂ thin films were deposited on the oxidized MPTS-SAM to form composite thin films, making use of the chemisorption ability of the −SO₃H group. Atomic force microscope (AFM) and contact angle measurements were used to characterize TiO₂ films. Adhesive force and friction force of TiO₂ thin films and silicon substrate were measured under various applied normal loads and scanning speed of AFM tip. Results showed that the friction force increased with applied normal loads and scanning speed of AFM tip. In order to study the effect of capillary force, tests were performed in various relative humidities. Results showed that the adhesive force of silicon substrate increases with relative humidities and the adhesive force of TiO₂ thin films only increases slightly with relative humidity. Research showed that surfaces with more hydrophobic property revealed the lower adhesive and friction forces.