化学吸附自组装偶氮苯小分子单层膜及表面浸润性研究

通过化学吸附自组装的方法, 将小分子量的偶氮苯分子自组装到平滑硅基底表面, 其表面接触角为83.7°. 微结构化硅基底表面的偶氮苯单层膜上表现出超疏水的特性, 接触角达到了151.9°. 经过紫外光照射后, 该表面的接触角没有发生明显的降低.     

柱状结构阵列碳纳米管膜的超疏水性研究

浸润性是固体表面的重要性质之一 .决定固体表面的浸润性的两个主要因素中 ,化学性质是内因 ,而几何结构形貌也是不可缺少的重要因素 .通过改变固体表面的粗糙度可以改变其浸润性 [1～ 5] .通常 ,人们用水接触角的大小来衡量固体表面水的浸润性 ,水与固体表面的接触角大于 1 5     

氧化锌薄膜的可控浸润性研究

采用一步电沉积的方法在导电玻璃基底上制备了具有粗糙表面的氧 化锌薄膜．用SEM和XPS表征了薄膜的表面形貌和化学组成,用接触角测定仪 测定接触角以评估薄膜的浸润性．结果显示,薄膜表面布满了无序生长的花瓣状 的微晶,形成疏松的结构．薄膜与水的接触角为133．2°,呈现了疏水的性质．通 过紫外光照射的方法可以使其由疏水性薄膜转化为亲水性薄膜,接触角降低到 4．8°。     

超疏水多孔阵列碳纳米管薄膜

碳纳米管由于具有特异的力学[1] 、光学[2 ] 、电学[3,4 ] 和磁学性质[5] ,使其在锂离子电池[6 ] 和平板展示器[7] 等方面呈现出广泛的应用前景 .Ebbesen等[8] 对无序碳纳米管材料的浸润性进行了详细研究 ,发现其很容易被水润湿 .然而 ,阵列碳纳米管膜的浸润性研究尚未见报道 .固体表面的浸润性主要由表面化学组分和几何结构两方面控制 .通常 ,加大表面粗糙度可以增强其浸润性 [9～ 16 ] .近来 ,超疏水表面 (即与水的接触角大于 1 5 0°的表面 )的研究显示了广泛的应用背景[13～ 16 ] .这种表面通常可由增加表面粗糙度和降低表面能来制备[1…     

超疏水二氧化钛薄膜的制备及其经紫外光照射引发的超亲水性研究

通过水热反应,在玻璃基底上沉积生成TiO₂薄膜,TiO₂薄膜呈花朵状,具有微纳米级的复合结构,在其表面有大量的乳状突起,经辛基三甲氧基硅烷表面修饰后表现出良好的超疏水性,静态接触角为164°,滚动角为4°。经紫外光照射4~6 h后,其表面变为超亲水性,接触角接近0°。用红外光谱,X射线光电子能谱(XPS)对其表面物质及元素进行表征,最后用Cassie理论对膜的润湿性进行了分析。     

多孔二氧化钛薄膜涂层的制备和双亲性质研究

二氧化钛因其具有光催化等性能而备受关注 [1] .其薄膜材料在紫外光的照射下 ,能产生活泼自由基 ,自由基能分解有机化合物 ,具有杀菌和自清洁作用 ;同时在紫外光照射时也能诱导材料产生超双亲特性 (油或水在其表面的接触角为 0°) ,赋予材料许多重要的应用 [2～ 4 ] .但二氧化钛薄膜材料表面的超双亲特性在停止紫外光照射后逐渐变弱 ,接触角也随放置时间的增加而增加 [5] .因此需要制备一种不需紫外光照射就具有永久双亲性能的薄膜涂层 .近期的研究表明 ,一些具有孔结构的薄膜涂层具有永久的双亲性能 ,该性能是由涂层本身的多孔性和平均孔尺…     

阵列聚合物纳米柱膜的超疏水性研究

浸润性(又称润湿性,Wettability)是固体表面的一个重要特征,它主要由表面化学组成和表面的几何结构两方面控制^[1～5].近年来,超疏水性固体表面由于在防雪、防污染、抗氧化以及防止电流等方面都有非常广阔的应用前景,引起了人们的极大关注[6～11].     

以砂纸为模板制作聚合物超疏水表面

报道了一种聚合物材料超疏水表面的简便制备方法. 以不同型号的金相砂纸为模板, 通过浇注成型或热压成型技术, 在聚合物表面形成不同粗糙度的结构. 接触角实验结果证明, 聚合物表面与水的接触角随着所用砂纸模板粗糙度的增加而加大, 其中粒度号为W7和W5砂纸制作的表面与水的接触角可超过150°, 显示出超疏水性质. 多种聚合物使用砂纸为模均可制备不同粗糙度及超疏水的表面, 本征接触角对复制表面浸润性的影响从Wenzel态到Cassie态而变小. 扫描电镜结果表明, 不规则形状的砂纸磨料颗粒构成了超疏水所需要的微纳米结构的模板.     

浸润性可调的导电聚苯胺/聚丙烯腈同轴纳米纤维

聚苯胺(PANI)因其具有可调的导电性、优异的化学稳定性、简单的制备方法等特点, 在化学电源、抗静电涂层、电磁屏蔽材料、抗腐蚀、传感器等领域具有广泛的应用前景[^1~4]. 由于聚苯胺的刚性分子链使得聚苯胺几乎不溶不熔, 难以加工应用, 因此, 将导电聚合物直接制成纳米纤维一直是合成纤维界所希望的目标之一. 此外, 由于材料尺度的减小, 使纳米材料的表面与界面性质,尤其是表面浸润性变得更为突出.浸润性是固体表面的重要特征之一, 它主要由表面的化学组成和微观结构共同决定^[5,6]. 可调的浸润性在超疏水材料、药物传输、仿生材料和微流体等领域具有重要的应用价值^[7~10] , 引起人们广泛关注.     

含偶氮苯基团的光敏型两亲化合物的合成及光照对其性质的影响

以对甲基苯胺和苯酚为主要原料,通过四步反应合成了一种含偶氮苯的光敏型两亲化合物AS,其结构用~1H NMR进行表征,并利用紫外吸收光谱研究了AS的光异构化,结果表明,在紫外光照射后,AS的结构由反式构型变为顺式构型。测定了化合物AS在水溶液中表面张力,计算相应的物化参数,发现紫外光照射后AS的临界胶束浓度(cmc)增加,最小表面张力(γ_(cmc))增大,饱和吸附量(Г_(max))减小,最小分子横截面积(A_(min))变大。测定了AS溶液在石英表面的接触角,发现紫外光照射后接触角减小,AS对石英的润湿性能增强。利用石英晶体微天平(QCM-D)研究了化合物AS在石英表面的吸附过程,发现紫外光照射后AS在石英表面的吸附量减小,吸附膜厚度降低。     

Photoreversibly switchable superhydrophobic surface with erasable and rewritable pattern

We report the facile fabrication of a functional nanoporous multilayer film with wettability that is reversibly tunable between superhydrophobicity and superhydrophilicity with UV/visible irradiation. Our approach controls surface roughness with an electrostatic self-assembly process and makes use of the photoresponsive molecular switching of fluorinated azobenzene molecules. Selective UV irradiation onto the nanostructured substrate was used to realize substrates with erasable and rewritable patterns of extreme wetting properties. Our findings will open up new avenues for external stimuli-responsive smart surfaces.     

Photoswitched Cell Adhesion on Azobenzene‐Containing Self‐Assembled Films

Stimuli‐responsive surfaces that can regulate and control cell adhesion have attracted much attention for their great potential in diverse biomedical applications. Unlike for pH‐ and temperature‐responsive surfaces, the process of photoswitching requires no additional input of chemicals or thermal energy. In this work, two different photoresponsive azobenzene films are synthesized by chemisorption and electrostatic layer‐by‐layer (LbL) assembly techniques. The LbL film exhibits a relatively loose packing of azobenzene chromophores compared with the chemisorbed film. The changes in trans/cis isomer ratio of the azobenzene moiety and the corresponding wettability of the LbL films are larger than those of the chemisorbed films under UV light irradiation. The tendency for cell adhesion on the LbL films decreases markedly after UV light irradiation, whereas adhesion on the chemisorbed films decreases only slightly, because the azobenzene chromophores stay densely packed. Interestingly, the tendency for cell adhesion can be considerably increased on rough substrates, the roughness being introduced by use of photolithography and inductively coupled plasma deep etching techniques. For the chemisorbed films on rough substrates, the amount of cells that adhere also changes slightly after UV light irradiation, whereas, the amount of cells that adhere to LbL films on rough substrates decreases significantly.     

Photoresponsive ion gating function of an azobenzene polyelectrolyte multilayer spin-self-assembled on a nanoporous support

The fabrication of a polyelectrolyte multilayer (PEM) on a porous membrane was successfully improved by using spin-coating electrostatic self-assembly. Surprisingly, the quality of the PEM film obtained on the nanoporous alumina substrate (i.e., its thickness and surface morphology) was comparable to that of a film deposited on silicon. An optical molecular switch that acts as an ion-gating channel was realized using a PEM membrane deposited layer-by-layer on an alumina support. One of the layer components of this device was a poly(acrylamide) copolymer containing an azobenzene chromophore, which is known to reveal strong voluminous expansion and contraction during light-induced reversible cis/trans isomerizations. The permeability of the bulk SO4(2-) ions was found to be sensitive to the changed channel sizes; for instance, the ion-permeation rate of SO4(2-) increased about 1.6 times after UV irradiation of the PEM, whereas that of the Cl- ion increased only 1.2 times. In the study, it was successfully demonstrated that the ion flow through the PEM membrane could be reversibly switched on and off over several azobenzene isomerization cycles.     

Azobenzene-containing monolayer with photoswitchable wettability

A compact monolayer containing azobenzene has been prepared on silicon substrates. The elaboration route consisted of covalent grafting of freshly synthesized azobenzene moieties onto an isocyanate-functionalized self-assembled monolayer (SAM). The highly packed and ordered isocyanate-functionalized SAM and the azobenzene-functionalized SAM were monitored and characterized by contact angle measurements and X-ray reflectivity (XR). Photoswitching of the wettability of the film induced by the reversible cis-trans isomerization of the azobenzene chromophores is experimentally shown from water and olive oil contact angle measurements.     

A Novel pH/Light‐Triggered Surface for DNA Adsorption and Release

A simple strategy for the immobilization of Cy3‐labeled single strand DNA (Cy3‐ssDNA) on a Si(001) surface and its release under control of both light and pH stimuli is presented. In order to prepare a dual pH/light‐triggered surface, positively chargeable azobenzene molecules are self‐assembled on the Si(001) surface. The surface wettability of this substrate can be changed under influence of both light and pH conditions. The substrates can be positively charged under mildly acidic conditions. The pH‐sensitive behavior of the film allows binding of Cy3‐ssDNA on the functionalized Si(001) surface through e?ective electrostatic interactions with the negatively charged polynucleotide backbone. Moreover, irradiation of the film with UVA light induces trans–cis isomerization of the azobenzene units on the surface. As a result, the binding a?nity for DNA decreases due to the changing surface hydrophilicity. In order to understand and control the reversible photoswitchable mechanism of this surface, water contact angles are measured after UVA and visible light irradiation. The release of DNA from a dual pH/light‐sensitive sample is performed using fluorescence microscopy. The results show that irradiation of the film with UVA light induces trans–cis isomerization of the photoresponsive azobenzene units; this leads to significant changes in the surface hydrophilicity and reduces the binding affinity for DNA.     

Reversible wettability of optothermal responsively perfluoroalkyl azobenzene self-assembled monolayers

In this study, two perfluoroalkyl azobenzene trichlorosilanes were synthesized and then characterized by Fourier transform infrared spectroscopy (FT-IR), ¹H NMR, and ¹⁹F NMR. Subsequently, these fluorine containing trichlorosilanes were applied to form self-assembled monolayers (SAMs) on silicon substrates by the method of chemical deposition in liquid phase. The optothermal responsively isomerization of the azobenzene was achieved via UV irradiation and heat treatment. The surface structures of the SAMs were investigated by X-ray photoelectron spectroscopy (XPS), energy dispersive X-ray spectroscopy (EDS), and atomic force microscopy (AFM). The results showed that the thermal migration of the terminal fluoroalkyl groups promoted the isomerization of the azo-groups. Moreover, the reversible contact angles of the SAMs demonstrated a good reversibility of surface wettability, which was consistent with the optothermal responsive isomerization of the azo-groups.     

偶氮苯聚合物的光控图案化

将自组装得到的聚苯乙烯胶体晶体,利用反应离子刻蚀和软刻蚀法复形到偶氮苯聚合物膜表面,获得六方非紧密排列的偶氮苯聚合物半球状阵列微图案膜。采用场发射扫描电子显微镜(FESEM)、原子力显微镜(AFM)和接触角测量仪等对膜的微阵列结构和表面润湿性能进行了表征。研究了光照对膜微图案结构和润湿性能的影响。结果表明:基于偶氮苯基团的光致取向特性,偶氮苯聚合物膜的微图案在偏振光照射下,可由初始的半球状阵列微结构形变成纺锤状和椭球状等结构,这种微结构的改变可以改变膜表面润湿性,实现偶氮苯聚合物膜表面不同微图案和润湿性能的光照调控。     

Lithium insertion into silicon films produced by magnetron sputtering

Using the method of magnetron-plasma sputtering of polycrystalline silicon target, amorphous silicon films 32–214 nm thick were produced on various (copper and titanium, polished and rough) substrates. A study of their charge-discharge characteristics under the galvanostatic conditions showed that all thin-filmed electrodes are capable of reversible lithium insertion. The amount of lithium inserted in the first cycles is close to the theoretical one. An analysis of composition and morphology of surface layer and also the behavior of reversible and irreversible capacities during cycling showed that the degradation of capacity is caused by the exfoliation of films from the substrate (the effect is more pronounced for the specimens with polished substrates) and somewhat breaking (cracking) of films. The thicker are the films, the severer is the disruption of silicon films in the cycling. The adhesion of films to the substrate surface is favored by the film roughness. At sufficiently high adhesion of films, their electrochemical properties only slightly depend on the nature (copper or titanium) of substrate.     

Partial dewetting of polyethylene thin films on rough silicon dioxide surfaces

The effect of roughness on the dewetting behavior of polyethylene thin films on silicon dioxide substrates is presented. Smooth and rough silicon dioxide substrates of 0.3 and 3.2-3.9 nm root-mean-square roughness were prepared by thermal oxidation of silicon wafers and plasma-enhanced chemical vapor deposition on silicon wafers, respectively. Polymer thin films of approximately 80 nm thickness were deposited by spin-coating on these substrates. Subsequent dewetting and crystallization of the polyethylene were observed by hot-stage optical microscopy in reflection mode. During heating, the polymer films melt and dewet on both substrates. Further observations after cooling indicate that, whereas complete dewetting occurs on the smooth substrate surface, partial dewetting occurs for the polymer film on the rough surface. The average thickness of the residual film on the rough surface was determined by ellipsometry to be a few nanometers, and the spatial distribution of the polymer in the cavities of the rough surface could be obtained by X-ray reflectometry. The residual film originates from the impregnation of the porous surface by the polymer fluid, leading to the observed partial dewetting behavior. This new type of partial dewetting should have important practical consequences, as most real surfaces exhibit significant roughness.     

Modulating the pattern quality of micropatterned multilayer films prepared by layer-by-layer self-assembly

Patterned multilayer films composed of poly(allylamine hydrochloride) (PAH) and poly(sodium 4-styrenesulfonate) (PSS) were prepared using dip and spin self-assembly (SA) methods. A silicon substrate was patterned with a photoresist thin film using conventional photolithography, and PAH/PSS multilayers were then deposited onto the substrate surface using dip or spin SA. For spin SA, the photoresist on the substrate was retained, despite the high centrifugal forces involved in depositing the polyelectrolytes (PEs). The patterned multilayer films were formed by immersing the PE-coated substrates in acetone for 10 min. The effect of ionic strength on the pattern quality in dip and spin multilayer patterns (line-edge definition and surface roughness of the patterned region) was investigated by increasing the salt concentration in the PE solution (range 0-1 M). In dip multilayer patterns, the presence of salt increased the film surface roughness and pattern thickness without any deformation of pattern shape. The spin multilayer patterns formed without salt induced a height profile of about 130 nm at the pattern edge, whereas the patterns formed with high salt content (1 M) were extensively washed off the substrates. Well-defined pattern shapes of spin SA multilayers were obtained at an ionic strength of 0.4 M NaCl. Multilayer patterns prepared using spin SA and lift-off methods at the same ionic strength had a surface roughness of about 2 nm, and those prepared using the dip SA and lift-off method had a surface roughness of about 5 nm. The same process was used to prepare well-defined patterns of organic/metallic multilayer films consisting of PE and gold nanoparticles. The spin SA process yielded patterned multilayer films with various lengths and shapes.