Electrostatic self-assembly of macroscopic crystals using contact electrification

Self-assembly of components larger than molecules into ordered arrays is an efficient way of preparing microstructured materials with interesting mechanical and optical properties. Although crystallization of identical particles or particles of different sizes or shapes can be readily achieved, the repertoire of methods to assemble binary lattices of particles of the same sizes but with different properties is very limited. This paper describes electrostatic self-assembly of two types of macroscopic components of identical dimensions using interactions that are generated by contact electrification. The systems we have examined comprise two kinds of objects (usually spheres) made of different polymeric materials that charge with opposite electrical polarities when agitated on flat, metallic surfaces. The interplay of repulsive interactions between like-charged objects and attractive interactions between unlike-charged ones results in the self-assembly of these objects into highly ordered, closed arrays. Remarkably, some of the assemblies that form are not electroneutral-that is, they possess a net charge. We suggest that the stability of these unusual structures can be explained by accounting for the interactions between electric dipoles that the particles in the aggregates induce in their neighbours.     

Ordered mesoporous silica fibers: effects of synthesis conditions on fiber morphology and length

Ordered mesoporous silica fibers offer potential industrial application in several areas including polymerization catalysis and separation. Understanding the effects of synthesis conditions on these fibers prepared by the interfacial self-assembly growth method is important to their production and application. The focus of this work is to understand the effect of two previously unstudied factors: silica source height (tetrabutylorthosilicate, TBOS) and the humidity, on the formation of ordered mesoporous silica fibers by the interfacial self-assembly method. Here the TBOS content, interface area, height of source, and humidity of the environment were varied to study their effect on fiber growth. The results show that the TBOS content and interface area do not have a significant impact on results of ordered mesoporous silica fibers. Increasing silica source height or environmental humidity, which lowers the water evaporation rate, gives silica fibers with lower length, less ordered inner pore structure and macroscopic morphology, and smaller pore size. Attempts to mix the growth medium eliminate the fiber morphology and yield gyroidal shapes. A mechanism that combines evaporation of water resulting in local concentration and surfactant, self-assembly, and reaction and diffusion of silica source is proposed to describe the formation of ordered mesoporous silica fibers.     

碳纤维/棉纤维/聚吡咯柔性复合材料的制备及性能研究

柔性超级电容器作为一种储能器件,具有功率密度高、充电时间短、循环寿命长、比电容高等优点,可满足可穿戴器件的需求,而柔性电极材料是决定柔性超级电容器发展的关键因素,它决定着电容器的主要性能指标。采用混纺的方法制备了碳纤维含量为20%(质量分数)的碳纤维/棉纤维混纺纱线,然后通过电化学沉积法在碳纤维/棉纤维混纺纱线上生长聚吡咯颗粒,成功制备了20%(质量分数)碳纤维/棉纤维/聚吡咯柔性复合材料。利用扫描电子显微镜、拉曼光谱分析仪和电化学工作站研究了复合材料的形貌、聚吡咯沉积情况以及复合材料的电容性能。结果表明,20%(质量分数)碳纤维/棉纤维/聚吡咯柔性复合材料中,聚吡咯颗粒直径为30~60 nm,且沉积均匀,化学活性较高;在1.02 mA/cm^2电流密度下,复合材料的最大比电容达到1.28 F/cm^2,其高比电容归因于电极的独特结构;复合材料具有良好的柔韧性、机械稳定性和充放电循环寿命,其经过6000次弯曲循环后,电容保持率仍有80%以上,可以用作柔性可穿戴超级电容器的电极材料。     

新型多级形貌的硅酸盐空心球的合成

由化学方法制备的氧化硅通常是在较苛刻的条件下制备的,如升高的温度、较高压力和/或强酸性、强碱性媒介,相比之下,在自然界里具有精致形貌的硅藻氧化硅构架在温和周围环境下的水相中就可以形成.本文中我们系统研究了具有相似于硅藻多级形貌的氧化硅空心球的合成,该合成经过一步步骤,采用嵌段高分子EO76PO29EO76基的乳液和廉价硅酸钠溶液为硅源.     

Directed aerosol writing of ordered silica nanostructures on arbitrary surfaces with self-assembling inks

This paper reports the fabrication of micro- and macropatterns of ordered mesostructured silica on arbitrary flat and curved surfaces using a facile robot-directed aerosol printing process. Starting with a homogenous solution of soluble silica, ethanol, water, and surfactant as a self-assembling ink, a columnated stream of aerosol droplets is directed to the substrate surface. For deposition at room temperature droplet coalescence on the substrates and attendant solvent evaporation result in continuous, highly ordered mesophases. The pattern profiles are varied by changing any number of printing parameters such as material deposition rate, printing speed, and aerosol-head temperature. Increasing the aerosol temperature results in a decrease of the mesostructure ordering, since faster solvent evaporation and enhanced silica condensation at higher temperatures kinetically impede the molecular assembly process. This facile technique provides powerful control of the printed materials at both the nanoscale and microscale through chemical self-assembly and robotic engineering, respectively.     

介孔氧化硅/氧化铈核壳双相复合颗粒的制备及其光催化降解活性

将CeO2纳米粒子负载在介孔氧化硅(W-mSiO2)支撑体上,制备了核壳结构的W-mSiO2/CeO2双相光催化复合颗粒.用X射线衍射、扫描电镜、透射电镜、氮气吸脱附、STEM-EDX mapping、Raman光谱、荧光光谱、紫外-可见漫反射光谱等手段分析样品的结构和性质,考察了复合光催化材料对亚甲基蓝(MB)的光催...     

Synthesis of a quaternary amine anion exchange resin and study [of] its adsorption behaviour for chromate oxyanions

Glycidyl methacrylate/N,N'-methylene bis-acrylamide (GMA/MBA) was prepared and allowed to react with tetraethylenepentamine (TEP) to give glycidyl methacrylate amine resin (RPA) followed by treatment with glycidyl trimethylammonium chloride (GTA) to give glycidyl methacrylate resin bearing quaternary ammonium chloride moieties (RQA). Zeta potential measurements showed that RQA particles are positively charged over pH 2-10 indicating the strong basic nature of the quaternary amine sites. The effect of pH on the recovery of chromate by RPA and RQA was examined. The results indicated that RQA is an efficient sorbent for chromate from both acidic and basic media. The repeated use of RQA was tested through stripping the adsorbed chromate using a mixture of 0.05 NaOH and 2 M NaCl in the case of the uptake from acidic media and using 2 M NaCl solution in the case of alkaline solutions.     

采用不同钛源合成介孔钛硅催化材料的研究

利用聚氧乙烯-聚氧丙烯-聚氧乙烯三嵌段共聚物(P123)作为结构导向剂,用氯化钾调控材料的形貌,以1,3,5-三甲苯(TMB)为分子筛的扩孔剂,钛酸正丁酯和四氯化钛作为不同的钛源,原位一步法合成出Ti-SBA-15分子筛。在高温煅烧除去模板剂之后,利用X射线衍射、紫外-可见漫反射光谱、红外光谱、扫描电镜以及N2吸附-脱附曲线对合成的介孔材料进行表征。结果表明:合成的介孔钛硅材料具有有序的孔道结构,钛在SBA-15的孔道内,钛在硅中的分散好。以钛酸丁酯为钛源合成的Ti-SBA-15呈规则的球形,平均直径为3.0μm;四氯化钛为钛源合成的Ti-SBA-15没有规则的形状,大小也不均一。     

镧(Ⅲ)对SBA-15分子筛改性研究

借助水热法，利用三嵌段共聚物聚(1，2—亚乙基二醇)—嵌段—聚(丙二醇)—嵌段—聚(1，2—亚乙基二醇)为模板剂，正硅酸四乙酯为硅源，强酸性条件下制备了分子筛SBA—15．分别以水及水 乙醇为介质采用LaCl3溶液与煅烧的主体材料SBA—15分子筛固—液相交换法，制备了La—(SBA—15)复合材料．利用化学分析、粉末XRD、N2吸附技术、IR评价了制备方法的有效性及对SBA—15分子筛孔结构的影响．结果表明，镧已并入SBA—15分子筛中，SBA—15内表面上的硅羟基团是镧进入的主要位置，部分客体在分子筛孔道内．制得的材料La—(SBA—15)保持高度有序的介孔二维六角结构，不改变载体SBA—15的介SLSL道结构．此外，考察了La—(SBA—15)产物的发光现象。     

镧(Ⅲ)对SBA-15分子筛改性研究

借助水热法,利用三嵌段共聚物聚(1,2-亚乙基二醇)-嵌段-聚(丙二醇)-嵌段-聚(1,2-亚乙基二醇)为模板剂,正硅酸四乙酯为硅源,强酸性条件下制备了分子筛SBA-15.分别以水及水+乙醇为介质采用LaCl₃溶液与煅烧的主体材料SBA-15分子筛固-液相交换法,制备了La-(SBA-15)复合材料.利用化学分析、粉末XRD、N₂吸附技术、IR评价了制备方法的有效性及对SBA-15分子筛孔结构的影响.结果表明,镧已并入SBA-15分子筛中,SBA-15内表面上的硅羟基团是镧进入的主要位置,部分客体在分子筛孔道内.制得的材料La-(SBA-15)保持高度有序的介孔二维六角结构,不改变载体SBA-15的介孔孔道结构.此外,考察了La-(SBA-15)产物的发光现象.     

Chiral mesoporous materials based on the self-assembly

Ordered mesoporous materials with various structures are synthesized based on the self-assembly of surfactant and inorganic precursors and covered by several excellent reviews. However, less work has been directed to chiral structured mesoporous materials, although these could have wide-ranging applications on the manufacturing of enantio-pure chemicals and pharmaceuticals as catalysts and separation media with both shape selectivity and enantioselectivity. This short review will address the synthesis of chiral mesoporous materials by chiral organic compounds templating route, covering single and 2-dimensional ordered chiral channel mesoporous materials. Non-porous helical fiber, atomic-scale enantio-morphism and zeolite-like materials with three-dimensional helical pores are beyond the scope of this paper.     

Continuous-flow lithography for high-throughput microparticle synthesis

Precisely shaped polymeric particles and structures are widely used for applications in photonic materials, MEMS, biomaterials and self-assembly. Current approaches for particle synthesis are either batch processes or flow-through microfluidic schemes that are based on two-phase systems, limiting the throughput, shape and functionality of the particles. We report a one-phase method that combines the advantages of microscope projection photolithography and microfluidics to continuously form morphologically complex or multifunctional particles down to the colloidal length scale. Exploiting the inhibition of free-radical polymerization near PDMS surfaces, we are able to repeatedly pattern and flow rows of particles in less than 0.1 s, affording a throughput of near 100 particles per second using the simplest of device designs. Polymerization was also carried out across laminar, co-flowing streams to generate Janus particles containing different chemistries, whose relative proportions could be easily tuned. This new high-throughput technique offers unprecedented control over particle size, shape and anisotropy.     

Synthesis of silica nanocubes by sol–gel method

A novel approach was employed in the fabrication of silica nanocubes with controlled size and shape. The silica nanocubes were highly dispersed with width of about 30 nm and product with high purity. A small amount of tartaric acid was introduced in the TEOS hydrolysis process. In this work tartaric acid as the organic template, was formed on the surface of hydrous silica colloidal particles. The organic template ordered by carboxyl, led to the self-assembly of amorphous silica sol encapsulated into cubic matrixes, and the organic template was packed into 3D structure.     

Hierarchical nanofabrication of microporous crystals with ordered mesoporosity

Shaped zeolite nanocrystals and larger zeolite particles with three-dimensionally ordered mesoporous (3DOm) features hold exciting technological implications for manufacturing thin, oriented molecular sieve films and realizing new selective, molecularly accessible and robust catalysts. A recognized means for controlled synthesis of such nanoparticulate and imprinted materials revolves around templating approaches, yet identification of an appropriately versatile template has remained elusive. Because of their highly interconnected pore space, ordered mesoporous carbon replicas serve as conceptually attractive materials for carrying out confined synthesis of zeolite crystals. Here, we demonstrate how a wide range of crystal morphologies can be realized through such confined growth within 3DOm carbon, synthesized by replication of colloidal crystals composed of size-tunable (about 10-40 nm) silica nanoparticles. Confined crystal growth within these templates leads to size-tunable, uniformly shaped silicalite-1 nanocrystals as well as 3DOm-imprinted single-crystal zeolite particles. In addition, novel crystal morphologies, consisting of faceted crystal outgrowths from primary crystalline particles have been discovered, providing new insight into constricted crystal growth mechanisms underlying confined synthesis.     

Cotton wool-like poly(lactic acid)/vaterite composite scaffolds releasing soluble silica for bone tissue engineering

Cotton wool-like poly(l-lactic acid) and siloxane-doped vaterite (SiV) composite scaffolds were prepared with a modified electrospinning system for bone tissue engineering applications. The effects of changing the SiV content in the materials from 10 to 30 wt% on elasticity and the ability to release calcium ions and soluble silica were evaluated. The elasticity of the cotton wool-like composites was almost the same as that of the PLLA from the results of compressibility and recovery tests. The materials released calcium ions for more than 56 days and soluble silica for 28–56 days in a tris buffer solution (pH 7.4). Mouse osteoblast-like cells (MC3T3-E1 cells) were cultured on/in the cotton wool-like materials or the fibremats out of the same composite materials as that used for the cotton wool-like materials. The cells penetrated into and proliferated inside the cotton wool-like materials, although they mainly adhered on the fibremat surface.     

Synthesis of ZnS nanoparticles into the pore of mesoporous silica spheres

The ZnS nanoparticles were exclusively synthesized in the pores of the mesoporous silica (MS) particles which had been coated with two bilayers of poly(allylamine hydrochloride) (PAH)/poly(styrene sulfonate) (PSS) via the layer-by-layer (LbL) self-assembly technique. Measurements and analysis of XRD and TEM showed that the ZnS nanocrystals were inserted into the pores of the MS spheres. This approach can be used to prepare composite materials involving functional inorganic nanoparticles which have potential application in biological immunoassay and photoelectronic fields.     

磁场诱导有序排列和自组装的研究进展

磁场是一种无接触的、新型的物理场,粒子受到这种物理场的作用会发生取向形成有序结构,从而赋予材料新颖的光、电、磁等特性.综述了在磁场作用下粒子有序排列和自组装的研究进展.     

Synthesis of Janus composite particles by the template of dumbbell-like silica/polystyrene

Janus particles possess promising performances. It is challenging to develop new methods to control composition and microstructure of the particles. In this report, we describe a general template synthesis of several non-spherical Janus composite particles by the template of dumbbell-like silica/polystyrene (PS) Janus particles. Both PS and silica can be modified to introduce desired functional groups respectively, or induce crystallization of other materials on the particle surface. Especially, by favorable growth of materials within the sulfonated PS gel forming the core–shell structure at the polymer part, several new Janus hollow particles are obtained after removal of the PS core.     

Silica crystalline colloidal array deep ultraviolet narrow-band diffraction devices

We developed a facile method to fabricate deep ultraviolet (UV) photonic crystal crystalline colloidal array (CCA) Bragg diffraction devices. The CCAs were prepared through the self-assembly of small, monodisperse, highly surface charged silica particles (~50 nm diameter) that were synthesized by using a modified St?ber process. The particle surfaces were charged by functionalizing them with the strong acid, non-UV absorbing silane coupling agent 3-(trihydroxylsilyl)-1-propane-sulfonic acid (THOPS). These highly charged, monodisperse silica particles self assemble into a face-centered cubic CCA that efficiently Bragg diffracts light in the deep UV. The diffracted wavelength was varied between 237 nm to 227 nm by tilting the CCA orientation relative to the incident beam between glancing angles from 90° to ~66°. Theoretical calculations predict that the silica CCA diffraction will have a full width at half-maximum (FWHM) of 2 nm with a transmission of ~10(-11) at the band center. We demonstrate the utility of this silica CCA filter to reject the Rayleigh scattering in 229 nm deep UV Raman measurements of highly scattering Teflon.     

Self-assembly of uniform nanoporous silica fibers

Self-assembly of nanoporous silica shapes is of great interest for modern nanotechnology because of uniform pore size, simplicity, and low cost of production. However, there are two major problems that prevent broad use of the self-assembly process. First, the process brings too broad a variety of the assembled shapes. Secondly, the yield of the desired shapes is far from 100%. Here, we describe a process of acidic self-assembly of silica shapes that is free of both of these problems. The process described results in virtually a 100% of very uniform fibers. Each fiber has a hexagonal cross section of approximately 2 /spl mu/m and a length of approximately 5 /spl mu/m. The highly uniform pores with periodicity of 3.8 nm are unidirectional along the fiber. These new fibers can be used in chromatography, drug delivery, manufacturing nanowires, nanoreactors for "one-dimensional" chemistry, etc.