微液滴在仿蛛丝结构TiO_2纤维表面的定向运动与粘附

制备了具有响应性的仿蛛丝周期纺锤节TiO2纤维。通过改变纤维表面微观结构、紫外光照和超声波等手段,仿蛛丝结构TiO2纤维表面浸润性会发生响应性变化。纤维表面的这种浸润性变化,不仅实现了水滴从纺锤节两端到中心处的定向运动,而且可以使得水滴被纤维纺锤节粘附。当仿蛛丝结构TiO2纤维表面为亲水状态时,无论纺锤节光滑还是粗糙,水都是从纺锤节两端向中心方向运动;当仿蛛丝结构TiO2纤维表面疏水时,水滴会被具有粗糙表面的纺锤节两端粘附。     

聚乙二醇对TiO2薄膜光致亲水性的促进作用

为了提高TiO₂薄膜的光致亲水性及其持久性, 将聚乙二醇(PEG)2000 引入TiO₂溶胶中, 利用提拉法在载玻片上制备出含PEG的TiO₂薄膜样品, 通过测试样品紫外光照下水滴接触角的变化, 考察不同浓度PEG对TiO₂薄膜光致亲水性能的影响; 并通过测试光照后的亲水薄膜样片暗处放置不同时间后接触角的变化, 比较含PEG的TiO₂薄膜和纯TiO₂薄膜样品的亲水持久性. 结果表明: PEG作为一种非离子型长链分子, 其适量的添加可促进TiO₂薄膜的光致亲水性及其持久性. 基于薄膜样品的傅里叶变换红外(FTIR)光谱和紫外-可见漫反射光谱(UV-Vis DRS)结果, 认为PEG作为空穴捕获剂有助于TiO₂薄膜中Ti³⁺的生成和稳定存在, 进而有助于亲水中心(表面羟基)的形成. 此研究对于TiO₂光自洁涂料的应用很有意义, 也为研究TiO₂的光激发瞬态行为提供了一个可能的简易方法.     

简易模板剂法制备多级介孔TiO2微球及其在染料敏化太阳能电池中的性能

采用模板剂法一步合成分级结构的介孔TiO₂微球, 考察了烷基胺类模板剂中烷基链长度对介孔TiO₂微球合成及性能影响. 将其应用于染料敏化太阳能电池的光阳极半导体薄膜中, 得到了9.5%-10.1%的高能量转换效率. X射线衍射(XRD)、物理吸附仪(BET)、扫描电镜(SEM)等的分析结果表明: 分级结构介孔TiO₂微球的晶相为纯锐钛矿型; 介孔TiO₂微球表面粗糙, 的纳米粒子堆积形成, 使微球具有介孔性质和较适宜的比表面积. 介孔TiO₂微球堆积形成了利于物质扩散的通道并具有良好的光散射效果; 同时微球介孔粗糙表面保证了染料的大量吸附, 从而提高了电池的光电流. 通过电化学阻抗分析结果验证了分等级结构介孔TiO₂微球光阳极有利于电解液的传输和物质扩散的优异性能.     

Bi2S3量子点敏化TiO2纳米阵列结构的制备及光电性能

利用水热法制备一维TiO₂纳米棒阵列,并采用化学浴沉积法(CBD)结合自组装技术在TiO₂纳米棒上敏化Bi₂S₃量子点,形成TiO₂/Bi₂S₃复合纳米棒阵列。系统研究了复合结构的表面形貌、晶体结构、光学及光电性能。结果表明:在修饰有三氨丙基三乙氧基硅烷自组装单分子膜(APTS-SAMs)的TiO₂纳米棒表面形成一层致密的Bi₂S₃量子点敏化层,这一技术的关键是含-NH₂末端的APTS-SAMs可有效促进Bi₂S₃的异相成核作用;Bi₂S₃的沉积时间对复合结构的光吸收及光电响应性能有决定性的影响,薄膜的光电流随着沉积时间呈先增加后减小的趋势,在沉积时间为20min时,光电流密度最大。这是因为随着沉积时间的增加,TiO₂纳米棒表面Bi₂S₃量子点密度增大,光吸收增加;而当沉积时间进一步延长时,Bi₂S₃在TiO₂纳米棒表面的大量负载而形成堆积和团聚,导致表面缺陷增多,光生电子复合几率增大,从而使光电流密度减小。     

Bi2S3量子点敏化TiO2纳米阵列结构的制备及光电性能研究

利用水热法制备一维TiO₂纳米棒阵列,并采用化学浴沉积法(CBD)结合自组装技术在TiO₂纳米棒上敏化Bi₂S₃量子点,形成TiO₂/Bi₂S₃复合纳米棒阵列.系统研究了复合结构的表面形貌、晶体结构、光学及光电性能.结果表明:在修饰有三氨丙基三乙氧基硅烷自组装单分子膜(APTS-SAMs)的TiO₂纳米棒表面形成一层致密的Bi₂S₃量子点敏化层,这一技术的关键是含-NH₂末端的APTS-SAMs可有效促进Bi₂S₃的异相成核作用;Bi₂S₃的沉积时间对复合结构的光吸收及光电响应性能有决定性的影响,薄膜的光电流随着沉积时间呈先增加后减小的趋势,在沉积时间为20 min时,光电流密度最大.这是因为随着沉积时间的增加,TiO₂纳米棒表面Bi₂S₃量子点密度增大,光吸收增加;而当沉积时间进一步延长时,Bi₂S₃在TiO₂纳米棒表面的大量负载而形成堆积和团聚,导致表面缺陷增多,光生电子复合几率增大,从而使光电流密度减小.     

TiO2-MoO3复合纳米管阵列薄膜的制备及其可见光活性

通过阳极氧化的方法制备TiO₂纳米管薄膜, 在MoO₃存在的条件下对该薄膜进行热处理得到TiO₂-MoO₃复合纳米管阵列薄膜. 利用X射线衍射(XRD), 扫描电子显微镜(SEM), X射线光电子能谱(XPS), 电化学阻抗谱(EIS), Mott-Schottky 及光电化学方法对得到的薄膜进行了表征. XRD结果表明, TiO₂-MoO₃复合纳米管薄膜中的TiO₂主要为锐钛矿晶型. SEM实验证实了薄膜纳米管结构的存在, 样品中的MoO₃均匀地分散在TiO₂纳米管表面. 利用XPS方法分析了TiO₂-MoO₃复合纳米管薄膜元素的组成, 结果表明, MoO₃在TiO₂表面形成TiO₂-MoO₃复合纳米管薄膜. 研究了热处理温度以及热处理时间对样品的光电化学性能的影响, 相对于单纯TiO₂纳米管薄膜, 适量引入MoO₃提高了样品在可见光区的光电响应能力, 样品的平带电位负移. 在450 °C热处理60 min制得的TiO₂-MoO₃复合半导体纳米管阵列薄膜光电响应活性最高.     

气相燃烧合成纳米复合粒子的形态与结构

在气相燃烧反应器中成功地合成了TiO₂-SiO₂、TiO₂-SnO₂复合粒子。TiO₂-SiO₂复合粒子中TiO₂以金红石型和锐钛型存在，SiO₂以无定型的形式存在。复合结构为SiO₂附着于TiO₂的外部，在Ti∶Si的进料比较大时SiO₂附着于TiO₂的表面，Ti∶Si比值减小到1∶4时，SiO₂包覆全部TiO₂表面。包覆层的厚度大约为6～7nm。TiO₂-SnO₂的复合粒子中同时存在着三种晶体结构SnO₂、金红石型和锐钛型的TiO₂。在复合粒子的表面，TiO₂和SnO₂两种组分分布均匀。通过改变进料方式可以调整复合粒子的结构。     

不同浓度Sn4+离子掺杂TiO2的结构、性质和光催化活性

采用溶胶-凝胶法制备出纯TiO₂和不同浓度Sn⁴⁺离子掺杂的TiO₂光催化剂(TiO₂-Snx%, x%代表Sn⁴⁺离子掺杂的TiO₂样品中Sn⁴⁺离子摩尔分数). 利用X 射线衍射(XRD)、X 射线光电子能谱(XPS)和表面光电压谱(SPS)确定了TiO₂-Snx%催化剂的晶相结构和能带结构, 结果表明: 当Sn⁴⁺离子浓度较低时, Sn⁴⁺离子进入TiO₂晶格, 取代并占据Ti⁴⁺离子的位置, 形成取代式掺杂结构(Ti_1-xSn_xO₂), 其掺杂能级在导带下0.38 eV处; 当Sn⁴⁺离子浓度较高时, 掺入的Sn⁴⁺离子在TiO₂表面生成金红石SnO₂, 形成TiO₂和SnO₂复合结构(TiO₂/SnO₂), SnO₂的导带位于TiO₂导带下0.33 eV处. 利用瞬态光电压谱和荧光光谱研究了TiO₂-Snx%催化剂光生载流子的分离和复合的动力学过程, 结果表明, Sn⁴⁺离子掺杂能级和表面SnO₂能带存在促进光生载流子的分离, 有效地抑制了光生电子与空穴的复合; 然而, Sn⁴⁺离子掺杂能级能更有效地增加光生电子的分离寿命, 提高了光生载流子的分离效率, 从而揭示了TiO₂-Snx%催化剂的光催化机理.     

模板法制备的Fe3+/TiO2中空纳米纤维的光催化性能

以棉花纤维为模板,利用浸渍-热转化两步法制备了Fe³⁺掺杂的二氧化钛(Fe³⁺/TiO₂)中空纳米纤维光催化材料,并利用扫描电镜(SEM)、X射线衍射(XRD)、紫外-可见光谱(UV-Vis)和ζ电位等技术对其形貌、结构、光吸收特性及其表面状态等进行了表征。以亚甲基蓝(methylene blue,MB)溶液的脱色降解为模型反应,考察了煅烧温度与时间对Fe³⁺/TiO₂中空纳米纤维光催化性能的影响。结果表明：利用该法可以制得棉花纤维形貌的Fe³⁺/TiO₂中空纳米结构材料;所得材料的催化性能除与材料的尺寸、相结构有关外,还与表面荷电性质有关,表面荷电量越高、表面结构缺陷越多、表面活性位越多,催化活性越高。500 ℃下煅烧2 h所得材料表面长有大量的粒子(平均尺寸为12 nm),其中TiO₂为锐钛矿结构,表面荷负电荷量最高,催化性能最好,如在太阳光下,2 h可使MB溶液的脱色降解率达93%,6 h完全脱色,而在纯TiO₂中空纤维材料上约为70%;该材料还具有良好的催化稳定性能,重复使用5次仍可使MB溶液的脱色降解率保持在90%以上,且该催化剂材料易于离心分离去除。     

超声场中纳米TiO2表面包覆氧化硅的研究

在超声场中，通过硅酸钠水解生成的无定形氧化硅对金红石相纳米TiO₂进行表面包覆，利用红外光谱、X射线光电子能谱、X射线衍射和透射电镜对所得样品进行了表征，并对纳米TiO₂的光稳定性和分散性进行了评价。红外光谱和X射线光电子能谱表明，氧化硅以化学键合的方式沉积在纳米TiO₂的表面，在包覆层和纳米TiO₂颗粒之间的界面上形成了Ti-O-Si键。TEM照片、表面元素分析和光稳定性实验显示，氧化硅在纳米TiO₂表面形成了均匀的包覆层，超声场有助于提高包覆层的均匀性和致密性。氧化硅的表面包覆提高了纳米TiO₂在水中的分散性、紫外线屏蔽能力和可见光透过性。随着氧化硅含量的增加，纳米TiO₂的光稳定性逐渐提高，当m(SiO₂)∶m(TiO₂)>1∶5时，纳米TiO₂的光稳定性基本不变，而且在热处理过程中纳米TiO₂的晶粒生长得到有效抑制。     

Controlled Directional Water‐Droplet Spreading on a High‐Adhesion Surface

Controlled directional spreading of a droplet on a smart high‐adhesion surface was made possible by simply controlling anodic oxidation. The wettability gradient of the surface was controlled from 0.14 to 3.38° mm^?1 by adjusting the anodic oxidation conditions. When a water droplet made contact with the substrate, the droplet immediately spread in the direction of the wettability gradient but did not move in other directions, such as those perpendicular to the gradient direction, even when the surface was turned upside down. The spreading behavior was mainly controlled by the wettability gradient. Surfaces with a V‐ or inverse‐V‐shaped wettability gradient were also formed by the same method, and two droplets on these surfaces spread either toward or away from one another as designed. This method could be used to oxidize many conductive substrates (e.g., copper, aluminum) to form surfaces with variously shaped wettability gradients. It has potential for application in microfluidic devices.     

Wettability conversion on the liquid flame spray generated superhydrophobic TiO2 nanoparticle coating on paper and board by photocatalytic decomposition of spontaneously accumulated carbonaceous overlayer

Titanium dioxide (TiO₂) is a photoactive material with various interesting and useful properties. One of those is the perfect wettability of TiO₂ surface after ultraviolet (UV) illumination. Wettability of a solid surface plays an important role in the field of printing, coating, and adhesion among others. Here we report on a superhydrophobic and photoactive liquid flame spray (LFS) generated TiO₂ nanoparticle coating that can be applied on web-like materials such as paper and board in one-step roll-to-roll process. The LFS TiO₂ nanoparticle coated paper and board were superhydrophobic instantly after the coating procedure because of spontaneously accumulated carbonaceous overlayer on TiO₂, and thus there was no need for any type of separate hydrophobization treatment. The highly photoactive LFS TiO₂ nanoparticle coating could be converted steplessly from superhydrophobic to superhydrophilic by UV-illumination, and the coating gave strong response to natural daylight illumination even in the shade. The superhydrophobic LFS TiO₂ coated surface can be used as an intelligent substrate, where photo-generated hydrophilic patterns guide the fluid setting and figure formation. Our study reveals that the wettability changes on the LFS TiO₂ surface were primarily caused by the photocatalytic removal of the carbonaceous material from TiO₂ during the UV-illumination and spontaneous accumulation of the carbonaceous material on the surface of the metal oxide during storage in the dark. The latter mechanism was found to be a temperature activated process which could be significantly speeded up by heat treatment. If other mechanisms such as surface oxidization, increment of hydroxyl groups, or charge separation played a role in the wetting phenomena on TiO₂, their effect was rather secondary as the removal and accumulation of the carbonaceous material dominated the wettability changes on the surface. Our study gives valuable information on the complex issue of photo-induced wettability changes on TiO₂.     

TiO2 photocatalysis: Design and applications

TiO₂ photocatalysis is widely used in a variety of applications and products in the environmental and energy fields, including self-cleaning surfaces, air and water purification systems, sterilization, hydrogen evolution, and photoelectrochemical conversion. The development of new materials, however, is strongly required to provide enhanced performances with respect to the photocatalytic properties and to find new uses for TiO₂ photocatalysis. In this review, recent developments in the area of TiO₂ photocatalysis research, in terms of new materials from a structural design perspective, have been summarized. The dimensionality associated with the structure of a TiO₂ material can affect its properties and functions, including its photocatalytic performance, and also more specifically its surface area, adsorption, reflectance, adhesion, and carrier transportation properties. We provide a brief introduction to the current situation in TiO₂ photocatalysis, and describe structurally controlled TiO₂ photocatalysts which can be classified into zero-, one-, two-, and three-dimensional structures. Furthermore, novel applications of TiO₂ surfaces for the fabrication of wettability patterns and for printing are discussed.     

超疏水性表面在冷凝条件下的润湿特性

采用测量接触角和观测偏光显微镜对超疏水表面在冷凝条件下的疏水特性进行了研究, 发现冷凝蒸汽进入超疏水表面的微凸起内冷凝, 表面的疏水特性被破坏, 表面的润湿特性变得不均匀, 部分区域甚至呈现亲水状态. 根据实验结果提出了冷凝条件下粗糙表面表观接触角的计算模型, 并使用冷凝条件下表面接触角的测量结果进行了验证.     

Thermal-induced durable superhydrophilicity of TiO<Subscript>2</Subscript> films with ultra-smooth surfaces

Superhydrophilic surfaces without the need of other stimuli are usually realized by constructing a rough morphology. However, constructing rough surfaces usually require specialized equipment or complicated processing. Besides, rough surfaces can cause undesirable scattering, which strongly limits the use in optical devices. In this article, we prepared superhydrophilic TiO₂ films with ultra-smooth surfaces using simple sol-gel dip-coating method. The hydrophilicity of the TiO₂ films varied with different post-heat treatments. The films heat-treated at 400?°C exhibited a durable superhydrophilicity and anti-fogging property. This superhydrophilicity was attributed to the decrease of surface hydrophobic alkoxy groups and the formation of point defects, i.e., Ti³⁺ and oxygen vacancies, which are favourable for dissociative water adsorption. The amount of surface organic groups was influenced by autophobicity effects, further hydrolysis and decomposition of residual alkoxy groups. Additionally, the wettability behaviours of the films were also explained from the perspective of the surface energy. These results can benefit the design and manufacture of anti-fogging and self-cleaning superhydrophilic TiO₂ films.

Open image in new window

The TiO₂ films exhibited intrinsic superhydrophilicity and anti-fogging property; the superhydrophilicity can maintain 30 days.

     

Fabrication of Ag Nanoparticles Embedded in TiO2 Nanotubes: Using Electrospun Nanofibers for Controlling Plasmonic Effects

Composites of electrospun poly(ethylene oxide) (PEO) fibers and silver nanoparticles (Ag NPs) were used as a soft template for coating with TiO₂ by atomic layer deposition (ALD). Whereas the as‐deposited TiO₂ layers on PEO fibers and Ag NPs were completely amorphous, the TiO₂ layers were transformed into polycrystalline TiO₂ nanotubes (NTs) with embedded Ag NPs after calcination. Their plasmonic effect can be controlled by varying the thickness of the dielectric Al₂O₃ spacer between Ag NPs and dye molecules by means of the ALD process. Electronic and spectroscopic analyses demonstrated enhanced photocurrent generation and solar‐cell performance due to the intense electromagnetic field of the dye resulting from the surface plasmon effect of the Ag NPs.     

A Polymer Composite Film with Reversible Responsive Behaviors

Summary: A responsive polymer composite film was generated by the use of reversibly switchable surface morphology of polystyrene‐block‐poly(methyl methacrylate) (PS‐b‐PMMA) films in response to different block selective solvents on the rough isotactic poly(propylene) (i‐PP) substrate. The maximum difference of the water contact angle of the composite films increased from 22.6° of PS‐b‐PMMA films on the smooth substrate to 42.6° when they were treated by PS and PMMA selective solvents, respectively. The mechanisms of the responsive extent enhanced and the superhydrophobicity of the composite films were discussed in detail.

Schematic illustration of how to fabricate a wettability‐responsive composite film: (a) on the flat Si substrate, (b) on the rough PP substrate.     

Switchable water absorption of paper via liquid flame spray nanoparticle coating

Surface wetting/anti-wetting and liquid absorption are relevant properties of many porous solids including paper and other cellulose-based materials. Here we demonstrate how surface wetting by water and water absorption of commercially available kraft paper can be altered by thin nanoparticle coatings fabricated by liquid flame spray in facile and continuous one-step process. Surface wettability and absorption properties of paper increased with silica and decreased with titania (TiO₂) nanoparticle coatings. Moreover, the water-repellent (superhydrophobic) TiO₂ nanoparticle coated paper could be switched to superhydrophilic and water absorbing by ultraviolet illumination. The experiments revealed that although surface wetting and liquid absorption of nanoparticle coated paper are strongly related to each other, they are two distinct phenomena which do not necessarily correlate. We propose wetting regimes on the nanoparticle coated paper samples on the basis of the experimental observations.     

Preparation and photocatalytic activity of B,Ce Co-doped TiO2 hollow fibers photocatalyst

A series of B, Ce co-doped TiO₂ (B, Ce-TiO₂) photocatalytic materials with a hollow fiber structure were successfully prepared by template method using boric acid, ammonium ceric nitrate and tetrabutyltitanate as precursors and cotton fibers as template, followed by calcination at 500°C in an N₂ atmosphere for 2 h. Scanning electron microscopy (SEM), X-ray diffraction (XRD), nitrogen adsorption-desorption measurements, and UV-visible spectroscopy (UV-Vis) were employed to characterize the morphology, crystal structure, surface structure, and optical absorption properties of the samples. The photocatalytic performance of the samples was studied by photodegradation phenol in water under UV light irradiation. The results showed that the TiO₂ fiber materials have hollow structures, and the fiber structure materials showed better photocatalytic properties for the degradation of phenol than pure TiO₂ under UV light. In the experiment condition, the photocatalytic activity of B, Ce co-doped TiO₂ fibers was optimal of all the prepared samples. In addition, the possibility of cyclic usage of B, Ce co-doped TiO₂ fiber photocatalyst was also confirmed, the photocatalytic activity of TiO₂ fibers remained above 90% of that of the fresh sample after being used four times. The material was easily removed by centrifugal separation from the medium. It can therefore be potentially applied for the treatment of water contaminated by organic pollutants.