光响应性超疏水偶氮苯自组装多层膜的制备及性质研究

近年来,偶氮苯类化合物的光学顺反异构现象已引起人们的广泛关注[1~7].在紫外光照射下,偶氮苯由反式结构转变为顺式结构,引起分子的偶极矩发生变化,导致分子的吸收光谱、尺寸及表面能等均发生变化[7].偶氮苯表面能的改变可引起其表面浸润性发生变化.据文献[1~4]报道,偶氮苯膜在紫外光照射前后接触角最大改变了11°.浸润性是固体表面的一个重要特性,主要受固体表面的化学组成和微观几何结构(粗糙度)影响[8~11].通常,与水的接触角大于150°的表面称为超疏水表面;而与水的接触角小于5°的表面称为超亲水表面.本文以2-(4-偶氮苯基苯氧基)丙烯酸…     

Ti(SO4)2沸腾水解法制备纳米TiO2及光催化研究

纳米二氧化钛是一种新型的无机功能材料,它具有许多独特的性质,如化学活性高、可见光透过性好、吸收紫外光性能强、具有超亲水性等[1-2],可用于制造电介质材料、光催化薄膜、化学传感器等[3]。TiO2作为光催化剂几乎能氧化降解水体和空气中的绝大多数有机污染物。制备纳米TiO2的     

微乳-水热法制备具有自清洁功能的TiO2薄膜

采用热陈化微乳液及浸渍-提拉技术,制备了具有自清洁功能的TiO2薄膜。 考察了微乳液中表面活性剂十二烷基苯磺酸（DBS）的用量对TiO2薄膜的表面形态和微观结构的影响。 进而对合成的TiO2薄膜的光催化活性、光致亲水性能及实际环境中的自清洁效果进行了测试评价。 随着表面活性剂DBS用量的增加,微乳液中的分散质点尺寸减小,但热陈化后所获得的TiO2粒子表现出凝集现象。 在DBS用量为0及58 mg/L时,所获得薄膜表面较为平整,由15~20 nm大小的TiO2粒子组成。 这些薄膜在无紫外光照射时,水接触角增大的速度较慢,并且在紫外光照射下能迅速恢复其超亲水性能。 将薄膜置于室外25 d后其表面无灰尘粘结,水接触角由原来的0°增大至14°~18°。 当DBS用量为580 mg/L以上时,薄膜表面起伏不平,粗糙度过大,对应TiO2薄膜光致亲水性能较差,室外放置25 d后,水接触角由原来的0°增大至46°~48°。     

TiO_2纳米薄膜油下超疏水/超亲水性的可逆调控

采用简单的提拉镀膜法制备了一种TiO_2纳米薄膜,在油相介质中,水滴在其表面的接触角约为160°,呈现出油下超疏水状态.当在湿度为20%的空气环境下对TiO_2纳米薄膜进行紫外光照射(60 min)后,该薄膜由油下超疏水状态转变为油下超亲水状态.对紫外光照射后的TiO_2纳米薄膜在100℃下热处理70min后,该薄膜又恢复到了初始的油下超疏水状态.因此,通过紫外光照射和热处理可实现TiO_2纳米薄膜油下超疏水性与油下超亲水性的可逆调控. TiO_2纳米薄膜油下水超浸润性可逆调控主要归因于薄膜表面的微纳米结构和化学组成变化的协同作用.     

可粘贴超疏水薄膜的制备

通过聚二甲基硅氧烷(PDMS)与碳纤维织物复合, 采用模板法在PDMS聚合物表面构筑微阵列结构, 制备了一种具有可重复粘贴性的超疏水薄膜. 研究结果表明, 该薄膜微结构表面的接触角为154°, 滚动角为14°, 具有低黏附的超疏水特性. 而PDMS与碳纤维织物的紧密结合, 赋予了超疏水薄膜较高的黏接力和力学性能, 断裂强度达到116.96 MPa. 所制备的超疏水薄膜可粘贴于多种材料表面, 同时经过30 d的长时间粘贴以及50次的循环粘贴后, 该薄膜依然保持着较高的黏附性能及超疏水特征, 表明超疏水薄膜具有良好的力学稳定性及耐久性, 满足长时间可重复使用的要求, 可应用于对破损超疏水涂层的快速、 大面积粘贴修复.     

超亲水TiO2和TiO2-SiO2表面的动态润湿性

1997年, Fujishima研究组[1]发现TiO2表面经UV光照射能产生较强的亲水性, 同时具有较高的亲油性, 即经UV光照射后的TiO2表面具有超双亲的性质. 这种防雾和自清洁性在工业上应用广泛, 已引起了人们的极大兴趣[2～5]. 进一步的研究发现, 超亲水的TiO2表面在暗处放置会变为疏水表面. 对于这个问题, 除了可以通过UV光照[6]、氩离子或电子束溅射[6]和高温热处理[5]等恢复其超亲水性外, 还可以通过添加摩尔分数为10%～30%的SiO2有效地降低TiO2表面的接触角, 提高UV光诱导的超亲水表面在暗处的稳定性能[3]. 另外, 诱导TiO2的亲水性需要较强的UV线强度(如太阳光), 使它在室内应用受到限制. 为了在室内实现TiO2的自清洁功能, Watanabe等[4]发现在TiO2中添加WO3可使TiO2在室内的照明光下也能实现亲水性转变. 以上这些研究成果为TiO2在工业和生活上的实际应用提供了重要的科学依据. 然而, TiO2的防雾和自清洁功能的实现同时也受其动力学性质的制约.     

TiO2光致亲水性及其在免处理版材中的应用研究

用溶胶-凝胶法制备了SiO₂和TiO₂薄膜,并涂覆于玻璃基片上,研究了TiO₂薄膜在紫外光照射下其超亲水性能的变化与光照时间的关系,分析了SiO₂薄膜对覆于其上的TiO₂薄膜的耐摩擦性能的影响.结果表明:TiO₂薄膜经紫外光照射后,疏水性急剧降低,显示亲水性能,与水的接触角可达到5°以下;当其覆膜于载玻片上后,具有良好的耐摩擦性和耐候性;TiO₂薄膜的超亲水性使其有望成为一种新型的环保可重复利用的印刷版材.     

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.     

透明抗静电多功能超疏水薄膜的制备

采用提拉法在聚酰亚胺薄膜表面分步涂覆了银纳米线及疏水纳米二氧化硅, 分别构筑了导电网络及超疏水涂层, 制备了超疏水抗静电透明薄膜. 研究结果表明, 超疏水抗静电透明薄膜保持了较高的透光性, 其透光率高于90%. 同时, 银纳米线网络的构筑有效增加了超疏水抗静电透明薄膜的导电性, 使其表面电阻介于10⁶~10¹⁰ Ω之间, 达到了抗静电要求. 水滴在该薄膜表面静态接触角高达156.4°, 滚动角小于1°, 展现了优异的超疏水特性. 通过导电网络及疏水涂层的构筑, 实现了透明及抗静电超疏水多功能的统一.     

聚苯硫醚超疏水复合涂层的制备与性能

利用工业原料聚苯硫醚微粉和疏水性二氧化硅纳米粉末,采用喷涂法在瓷砖表面制备了疏水复合涂层.研究了热处理温度、组分配比对涂层表面形貌、粗糙度和接触角的影响,发现随着热处理温度升高,涂层表面粗糙度增大,随着疏水性二氧化硅含量的增加,由于表面聚集的疏水性二氧化硅增多,涂层疏水性增强,在热处理温度为280℃、疏水性二氧化硅与聚苯硫醚质量比为1∶1时,可获得超疏水涂层,涂层的接触角大于150°,滚落角小于4°,pH值为1～14的水溶液在其表面都具有很高的接触角.超疏水涂层具有良好的自清洁效果,并且经落沙法实验测定,超疏水涂层耐刮伤性能良好.     

Photoinduced swelling control of amphiphilic azoaromatic polymer membrane

To control the swelling of polymer membrane by photoirradiation amphiphilic azoaromatic polymer membranes were prepared and a photoinduced change in the swelling degree of water was investigated. The azobenzene moiety in the side chain of the polymer was isomerized from trans form to cis form by ultraviolet (UV) irradiation and reverse isomerization was found by visible light irradiation. The swelling degree of the polymer membrane for water in the dark was decreased by UV radiation, and when visible light irradiation was carried out in the polymer membrane the degree of swelling recovered to the original level. The swelling degree decreased with an increase in the mole fraction of the azobenzene moiety in the dark and under UV irradiation. The deswelling degree of the polymer membrane by UV irradiation also decreased with an increase in the mole fraction of the azobenzene moiety. This reversible change in the swelling degree was considered to be caused by the photoisomerization of the azobenzene moiety in the polymer membrane.     

Wettability conversion from superoleophobic to superhydrophilic on titania/single-walled carbon nanotube composite coatings

Superoleophobic surfaces were demonstrated on perfluorosilane-rendered titania (TiO(2))/single-walled carbon nanotube (SWNT) composite coatings. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) observations revealed that SWNTs play a key role in the formation of overhanging structures and the nanoscale roughness on the coating surface, which compose the two critical morphologic factors for a superoleophobic surface. The wettability conversion from superoleophobic to superhydrophilic of the composite coatings was realized by the gradual decomposition of 1H,1H,2H,2H-perfluorodecyltrichlorosilane (FDTS) on the coating surface using UV irradiation. Contact angle measurement on both smooth TiO(2) surface and rough composite coating surface under different UV irradiation time revealed that the wetting behavior of the liquids on the composite coating surface passes from the Cassie to the Wenzel and finally to the inversed-Cassie regime. Different liquids show different irradiation time for the wetting state change. By controlling the UV irradiation dose, liquids with surface tension difference smaller than 5 mN/m can exist in completely converse wetting states on the same coating surface, that is, superphobic for one liquid while superphilic for another with lower surface tension. Mixed organic liquids with different surface tension can be completely separated through a coated grid using this wettability tuning technique.     

Effect of Nano TiO2 on Self-cleaning Property of Cross-linking Cotton Fabric with Succinic Acid Under UV Irradiation

Optimization of curing cotton textiles through self-cleaning property constructs the main goal of the present study. Cotton fabrics with 0.1, 0.3, 0.5, 1 and 1.5 on weight of bath percent were cured by nano titanium dioxide (P25 Degussa) with cross-link and non cross-link methods. In this study, succinic acid was used as a cross-link agent to attach TiO₂ to the cotton. The amount of loaded titania particles to cotton fabrics and the thermal behavior of cured samples were studied by the burning method and thermogravimetric analysis, respectively. Self-cleaning degree of cured samples, stained with natural and synthesized dyes under irradiation of 20 and 400 W UV lamps was investigated by a reflectance spectrophotometer. The structure and morphology of treated cotton fabrics were investigated using scanning electron microscopy and crystallinity of titania coatings by X-ray diffraction spectroscopy. The tearing strengths of titania-coated cotton fabrics before and after light irradiation were measured. Results showed that the stability of nano TiO₂ coating and self-cleaning degree of treated samples with cross-link method were much higher than those of non cross-link method, and cotton cellulosic chains were not decomposed by the photocatalytic activity of titania.     

Organic pigment particles coated with titania via sol-gel process

This paper presented a novel method for the organic pigment coated with titania to improve the weatherability and dispersion ability in waterborne system. The organic pigment was first orderly adsorbed by two kinds of electrolyte: poly(sodium 4-styrenesulfonate) (PSS) and poly(diallyldimethylammonium chloride) (PDADMAC), then coated by titania via sol-gel process from titanium n-butoxide (TBOT). The effects of the numbers of polyelectrolyte layer, water content, and TBOT content on the morphology, particle size, surface element composition, porosity and pore size, thermal stability, and UV shielding property of the organic pigment were systematically investigated. It was found that only two layers of electrolyte adsorption and one-step coating of titania could obviously enhance the UV shielding property even thermal stability of the organic pigment. The thickness of the titania layer could be easily tailored by TBOT content.     

Self-generated hierarchically porous titania with high surface area: photocatalytic activity enhancement by macrochannel structure

Various hierarchical porous titania with high surface area over 600 m(2)/g have been synthesized via a spontaneous self-formation process from titanium alkoxides by a water adjusting approach using acetonitrile as reaction medium. The reactivity of metal alkoxides and the water content in acetonitrile medium on the resultant structure have been investigated. The porosities of the products were characterized by SEM, TEM and N(2) adsorption-desorption measurements. The observation on the evolution of porous structure with increasing water content in reaction system is essential for a better understanding of hierarchical porous structure formation over different length scales by this self-formation process. The creation of macro/micropores in photocatalytic titania materials has been found to enhance the photocatalytic activity due to both the action of macrochannels as light harvester and the easy diffusion effect of organic molecules. The present work shows clearly that hierarchically porous titania with the presence of macroporous structure and high surface area can be very efficient photocatalysts, suggesting their potential applications in water treatment as decontamination materials.     

High permeate flux of PVA/PSf thin film composite nanofiltration membrane with aluminosilicate single-walled nanotubes

This article describes a simple method to fabricate uniform porous antireflective (AR) coatings composed of nanoflakes on the surface of soda lime glass through one-step hydrothermal alkali (NaOH) etching process. Experimental conditions including reaction temperature, NaOH concentration, and reaction time were investigated to find the optimal etching conditions, and the maximum transmittance increases from 90.5% to 98.5%. The coating thickness increases with increase in the NaOH concentration, leading to the tunable red-shift of transmission and reflection spectra in the UV and entire visible range. And the corresponding uniform structural reflected colors varying from gray, pale yellow, yellow, pink, blue to pale blue are observed when the etched glasses are viewed in reflected light. The relationship of coating thickness, transmittance, reflectance, and reflected color was obtained and discussed. The etched glass after introducing TiO(2) component onto the porous coating had AR, self-cleaning (superhydrophilic and photocatalytic) and antifogging properties. It is conceivable that such etched glasses would have broad potential applications in optical devices, solar cells, light emitting diodes, and varied window glasses.     

Photocatalytic reaction on photofuel cell titania electrode

Benzoic acid-doped titania electrodes were prepared from titanium alkoxide sols containing benzoic acid in order to examine the photocatalytic reaction of the fuel material concentrated on the titania surface of a photofuel cell electrode. This doping was developed in order to understand the physicochemical processes on the titania rather than to advance the practical use of the photofuel cells. The observed photocurrent and CO₂ and H₂O productions indicated that the oxidation of the benzoic acid enhanced the generation of electricity during the UV irradiation. Benzoic acid molecules should be oxidized by oxygen molecules and holes on the titania surface. The steam treatment of the electrodes improved the benzoic acid oxidation and the photocurrent because it promoted the titania densification and enhanced the interaction between the benzoic acid and titania. The benzoic acid-doped titania is a valid model of the fuel material concentrated in the porous titania when using benzoic acid as the fuel material. The contact between the benzoic acid and titania is important in order to obtain a high photofuel electric conversion.     

Photoflocculation of TiO2 microgel mixed suspensions

Photocatalytic TiO 2 was derivatized with an amino silane to give a positively charged colloidal suspension in water. UV irradiation of the cationic titania oxidized the organo silane coating converting the titania to a negatively charged colloid. Irradiation of mixed suspensions of cationic titania and cationic polyvinylamine microgel induced catastrophic flocculation. Electrophoresis and XPS evidence suggests that the UV removed the amine groups from the titania resulting in heteroflocculation of anionic titania with cationic microgel particles.     

UV‐Induced Tetrazole‐Thiol Reaction for Polymer Conjugation and Surface Functionalization

A UV‐induced 1,3‐dipolar nucleophilic addition of tetrazoles to thiols is described. Under UV irradiation the reaction proceeds rapidly at room temperature, with high yields, without a catalyst, and in both polar protic and aprotic solvents, including water. This UV‐induced tetrazole‐thiol reaction was successfully applied for the synthesis of small molecules, protein modification, and rapid and facile polymer–polymer conjugation. The reaction has also been demonstrated for the formation of micropatterns by site‐selective surface functionalization. Superhydrophobic–hydrophilic micropatterns were successfully created by sequential modifications of a tetrazole‐modified porous polymer surface with hydrophobic and hydrophilic thiols. A biotin‐functionalized surface could be fabricated in aqueous solutions under long‐wavelength UV irradiation.     

Construction of 3D hierarchical SnO2 microspheres from porous nanosheets towards NO decomposition

Three-dimensional (3D) hierarchical architectures are currently attracting worldwide interest owing to their fascinating morphology-dependent properties and potential applications. Herein we constructed SnO₂ microspheres with 3D hierarchical flower-like architectures self-assembled with porous SnS₂ nanosheets by a facile hydrothermal method with subsequent calcination. The chemical and physical properties as well as photocatalytic application of SnO₂ microspheres were investigated. The size and morphology were examined with scanning electron microscopy and transmission electron microscopy. The phase and crystalline structure were determined with powder X-ray diffraction. The UV–Vis absorption property was determined with UV–Vis diffuse reflectance. The photocatalytic activities were evaluated with nitrogen monoxide (NO) decomposition under UV–Vis light irradiation. The effects of calcination temperature on morphology and NO decomposition were also studied.