Template synthesis of imine-based covalent organic framework core-shell structure and hollow sphere: a case of COF<Subscript>TTA-DHTA</Subscript>

Controllably synthesizing well-dispersed covalent organic frameworks (COFs) with uniform both morphology and size is still a challenge. Herein, we report the template-directed synthesis of COF_TTA-DHTA-based core-shell hybrids under solvothermal conditions by using amino-functionalized SiO₂ microspheres as templates coupled with stepwise addition of initial monomer molecules. The modified amino groups on the surfaces of SiO₂ templates play an important role in the formation of well-defined NH₂-f-SiO₂@COF_TTA-DHTA core-shell hybrids. COF_TTA-DHTA hollow spheres can be obtained by etching SiO₂ cores of NH₂-f-SiO₂@COF_TTA-DHTA. Both the NH₂-f-SiO₂@COF_TTA-DHTA and COF_TTA-DHTA hollow spheres possess the well-defined morphology, high crystallinity and porosity, excellent dispersion property and high chemical stability. The template synthesis method demonstrated in this work provides a general method for the shape-controlled synthesis of COF-based materials, which is important for the further applications in the fields such as energy storage, drug delivery and catalysis.     

Silver Hollow Microspheres: Large-scale Synthesis, Characterization and Electromagnetic Shielding Property

A facile and large-scale synthesis method to fabricate silver hollow microspheres with controllable morphologies and shell thickness is described using low-cost glass microspheres as templates. The method mainly involves two steps of the preparation of silver-coated glass microsphere core-shell particles by a controllable liquid reduced reaction of Ag[(NH3)2]+ solution, which only produces silver nanoparticles anchored on the surface of the thiolated glass microsphere templates, and the removal of glass microspheres by wet chemical etching with HF solution. The products are well characterized by field emitted scanning electron microscopy (SEM), transmitted electron microscopy (TEM), X-ray photoelectron spectra (XPS), X-ray diffraction (XRD) and energy dispersive X-ray (EDX) etc. The as-prepared core-shell particles and hollow particles have even and compact silver shells. The electromagnetic shielding coatings based on the silver hollow microspheres are demonstrated to have high conductivity, excellent shielding effectiveness and long durability, suggesting that the silver hollow microspheres obtained here are a novel light-weight electromagnetic shielding filler and will have extensive applications in the electromagnetic compatibility fields.     

Synthesis of silica/carbon-encapsulated core-shell spheres: templates for other unique core-shell structures and applications in in situ loading of noble-metal nanoparticles

Silica@carbon core-shell spheres have been synthesized via a hydrothermal carbonization procedure with glucose as the carbon precursor and silica spheres as the cores. Such SiO(2)@C core-shell spheres can be further used as templates to produce SiO(2)@C@SiO(2), and SiO(2)@SiO(2) spheres with a vacant region in two SiO(2) shells, noble-metal nanoparticle loaded SiO(2)@C core-shell spheres, and hollow carbon capsules through different follow-up processes. The obtained core-shell materials possess remarkable chemical reactivity in reducing noble-metal ions to nanoparticles, e.g., platinum. These unique core-shell spherical composites could find applications in catalyst supports, adsorbents, encapsulation, nanoreactors, and reaction templates.     

A facile method to fabricate ZnO hollow spheres and their photocatalytic property

This paper presents a novel and facile method for the fabrication of ZnO hollow spheres. In this approach, zinc ions were first adsorbed onto the surfaces of sulfonated polystyrene core-shell template spheres, and then reacted with NaOH to form a ZnO crystal nucleus, which was followed by a growth step to form ZnO nanoshells. During the formation of ZnO nanoshells or later on, the template spheres were "dissolved" in the same media to obtain ZnO hollow spheres directly. Neither additional dissolution nor calcination process was needed in this method to remove the templates, and the reaction conditions were very mild: neither high temperature nor long time was needed. Transmission electron microscopy, scanning electron microscopy, X-ray photoelectron spectroscopy, X-ray diffraction, and Brunauer-Emmett-Teller analysis were used to investigate the morphology, surface composition, crystalline structure, specific surface area, and porosity of the ZnO hollow spheres, respectively. UV-visible spectra show that these ZnO hollow spheres had very good photocatalytic activity.     

Novel sol–gel synthesis of N-doped TiO<Subscript>2</Subscript> hollow spheres with high photocatalytic activity under visible light

Novel ammonia and triethanolamine assisted sol–gel synthesis method was developed to fabricate the N-doped TiO₂ hollow spheres. The prepared hollow spheres were in submicron size and had good morphology and high specific surface area. Polystyrene (PS) latexes in size of 470 nm were used as the templates to fabricate PS/TiO₂ core–shell spheres. Here ammonia and triethanolamine was first employed together to control the sol–gel process. The N-doped TiO₂ hollow spheres were got after calcinations of the core–shell spheres by using triethanolamine as N source, and the amount of doped N could be easily adjusted by changing the amount of triethanolamine. The hollow spheres had distinct visible light response, and the optical response shifted more to the visible region as the amount of doped N increases. The photodegradation of methylene blue expressed the high photocatalytic activity of the N-doped TiO₂ hollow spheres under visible light.     

中空TiO_2微球的制备及对聚丙烯酸酯薄膜性能的影响

采用阳离子聚苯乙烯微球作为模板,钛酸四丁酯为钛源,氨水为催化剂,制备了中空TiO_2微球.采用X射线衍射、扫描电镜及比表面测定仪对其形貌和结构进行了表征,并考察了模板粒径、钛源用量以及催化剂用量对中空TiO_2微球形貌的影响.通过物理共混法将其引入至聚丙烯酸酯乳液中并成膜,研究了复合薄膜的保温性能、抗紫外性能及力学性能.结果表明,锐钛矿相中空TiO_2微球模板粒径、钛源用量以及催化剂用量影响中空TiO_2微球的空心尺寸、壁厚及壳层致密性.中空TiO_2微球可显著提升聚丙烯酸酯薄膜的保温性能、抗紫外性能和力学性能.采用不同粒径的模板制备的中空TiO_2微球对复合薄膜的各项性能均有影响,其中模板粒径为140 nm时复合薄膜性能最优,光反射率提升63%,导热系数降低27%,且在波长小于360 nm范围内,紫外透过率几乎为0,抗张强度增加100%,断裂伸长率提升62%.     

Low‐Temperature Facile Template Synthesis of Crystalline Inorganic Composite Hollow Spheres

This report presents a facile approach for the low‐temperature synthesis of crystalline inorganic‐oxide composite hollow spheres by employing the bulk controlled synthesis of inorganic‐oxide nanocrystals with polymer spheres as templates. The sulfonated polystyrene gel layer can adsorb the target precursor and induce inorganic nanocrystals to grow on the template in situ. The crystalline phase and morphology of the composite shell is tunable. By simply adjusting the acidity of the titania sol, crystalline titania composite hollow spheres with tunable crystalline phases of anatase, rutile, or a mixture of both were achieved. The approach is general and has been extended to synthesize the representative perovskite oxide (barium and strontium titanate) composite hollow spheres. The traditional thermal treatment for crystallite transformation is not required, thus intact shells can be guaranteed. The combination of oxide properties such as high refractive index, high dielectric constant, and catalytic ability with the cavity of the hollow spheres is promising for applications such as opacifiers, photonic crystals, high‐κ‐gate dielectrics, and photocatalysis.     

Preparation of hollow silica microspheres with controlled shell thickness in supercritical fluids

This article presents a novel route to prepare hollow silica microspheres with well-defined wall thickness by using cross-linked polystyrene (PS) microspheres as templates with the assistance of supercritical carbon dioxide (SC-CO₂). In this approach, the cross-linked PS templates can be firstly prepared via emulsifier-free polymerization method by using ethylene glycol dimethacrylate or divinylbenzene as cross-linkers. Then, the silica shell from the sol–gel process of tetraethyl orthosilicate (TEOS) which was penetrated into the PS template with the assistance of SC-CO₂ was obtained. Finally, the hollow silica spheres were generated after calcinations at 600 °C for 4 h. The shell thickness of the hollow silica spheres could be finely tuned not only by adjusting the TEOS/PS ratio, which is the most frequently used method, but also by changing the pressure and aging time of the SC-CO₂ treatment. Fourier transform infrared spectroscopy, transmission electron microscopy, and scanning electron microscope were used to characterize these hollow silica spheres.     

单分散SnO2中空微纳米球的制备和性质

模板法是制备无机中空微纳米球的重要方法之一. 本文以苯乙烯为单体, 通过乳液聚合得到粒径约为620 nm的单分散聚苯乙烯(PS)微球. 以磺化后的聚苯乙烯(PSS)微球为模板, 利用阴阳离子静电吸附作用, 将PSS与前驱体SnSO₄中的Sn²⁺结合. 通过Sn²⁺在乙醇-水介质中的水解作用得到核-壳复合结构, 再经高温煅烧, 得到SnO₂中空微纳米球. 实验对前驱体的浓度、表面活性剂的用量、反应时间及模板选择等方面做了研究,通过扫描电镜(SEM)、X 射线衍射(XRD)、红外(IR) 光谱、热重分析(TGA)、H₂ 程序升温还原(H₂-TPR)、Brunauer-Emmett-Teller (BET)比表面积等技术深入探究SnO₂中空微纳米球的结构, 并对比中空SnO₂与实心粒子的氧化还原特性. BET和H₂-TPR显示将SnO₂制备成微纳米空心球后其比表面积增大, 表面氧空位明显增多, 氧化活性明显提高. 从IR 及XRD推断核-壳结构形成机理, 进而优化出简单合理的实验方案, 获得表面光滑、结构致密, 包覆厚度可控的SnO₂中空微纳米球.     

利用Ostwald熟化作用合成空心碳纳米材料

以淀粉等易获得的生物质为碳前驱物, 亚铁盐为添加剂, 采用水热法制备了碳材料. 实验发现, 在反应过程中, 首先生成了被无定形碳包裹的铁氧化物纳米棒, 形成碳/铁氧化物的核/壳结构. 在进一步的反应中, 铁氧化物核自发溶解, 最终得到了空心的碳纳米棒. 讨论了铁氧化物自发溶解的原因, 认为空心碳纳米棒的形成是由Ostwald熟化现象造成的. 当以葡萄糖或环糊精为碳前驱物时, 得到的是空心碳球, 这可能与各种碳前驱物不同的表面活性剂作用有关.     

新型氧化铝空心球的制备及表征

以胶体碳球为模板, 廉价的硝酸铝为铝源, 成功制备出了新型的大小可控的氧化铝空心球. 通过透射电子显微镜(TEM)、扫描电子显微镜(SEM)、能量扩散X射线(EDX)、X射线粉末衍射(XRD)等手段对合成产品进行了表征, 并考察了不同合成条件对空心球形貌的影响. 实验结果表明, 合成的氧化铝空心球大小均一, 粒径及壁厚均可调节. 在该实验条件下, 硝酸铝浓度及吸附时间的改变对产品结果没有明显的影响, 而吸附温度的改变引起了产品表面光滑度及壁厚的改变.     

利用胶体碳球为模板制备SiO2、TiO2、SnO2空心球

介观尺度的氧化物空心球材料在许多领域都有着潜在的应用价值[1],因此近年来受到人们的广泛关注。其制备方法包括:模板法[2],声化学法[3],水热法[4]等。其中胶体粒子模板合成是制备氧化物空心球材料的一条最为有效的途径。常见的胶体粒子有金、银、CdS的纳米粒子,介观尺度的SiO     

一种新型的空心镍纳米球的合成

通过以二氧化硅粒子作为模板和金纳米粒子为表面晶种的方法制备了壳厚度可控的镍空心球。采用TEM﹑XRD对二氧化硅/镍复合球和镍空心球进行了表征和研究。结果表明镍纳米壳是由似针状的面心立方的镍纳米粒子构成的，碱溶液处理过程不影响镍纳米壳的形貌。高温处理显示镍空心球具有良好的热稳定性。     

α-Fe_2O_3空心球的水热法制备及其对苯酚的吸附性能

以铁氰化钾、磷酸二氢铵等为反应物,采用水热法合成了α-Fe2O3空心球,并用XRD,TEM,FESEM(场发射扫描电镜)、UV-Vis和低温氮吸附脱附对其进行了表征。结果表明,α-Fe2O3空心球直径在200～560nm之间,其BET比表面积为80m2·g-1,平均孔径为8.5nm。考察了反应时间、反应物用量和反应温度等对α-Fe2O3空心球形貌和大小的影响,提出了其可能的形成机理。研究了室温下α-Fe2O3空心球吸附苯酚的性能,吸附达平衡时,其吸附苯酚的量达97mg·g-1。     

Preparation, structure, and magnetic properties of mesoporous magnetite hollow spheres

Preparation of mesoporous Fe3O4 (magnetite) hollow spheres has been reported using hydrothermal synthesis and calcinations. The carboxyl-functionalized PS spheres were used as the templates coated by Fe3O4 particles and ethylene glycol (EG) as an organic structure directing agent. PS and EG were removed by calcinations method. The surface area after calcination at 500 degrees C is found to be 74 m(2) g(-1). The hollow spheres exhibited the weak ferromagnetism.     

Use of carbonaceous polysaccharide microspheres as templates for fabricating metal oxide hollow spheres

A general method for the synthesis of metal oxide hollow spheres has been developed by using carbonaceous polysaccharide microspheres prepared from saccharide solution as templates. Hollow spheres of a series of metal oxides (SnO2, Al2O3, Ga2O3, CoO, NiO, Mn3O4, Cr2O3, La2O3, Y2O3, Lu2O3, CeO2, TiO2, and ZrO2) have been prepared in this way. The method involves the initial absorption of metal ions from solution into the functional surface layer of carbonaceous saccharide microspheres; these are then densified and cross-linked in a subsequent calcination and oxidation procedure to form metal oxide hollow spheres. Metal salts are used as starting materials, which widens the accessible field of metal oxide hollow spheres. The carbonaceous colloids used as templates have integral and uniform surface functional layers, which makes surface modification unnecessary and ensures homogeneity of the shell. Macroporous films or cheese-like nanostructures of oxides can also be prepared by slightly modified procedures. XRD, TEM, HRTEM, and SAED have been used to characterize the structures. In a preliminary study on the gas sensitivity of SnO2 hollow spheres, considerably reduced "recovery times" were noted, exemplifying the distinct properties imparted by the hollow structure. These hollow or porous nanostructures have the potential for diverse applications, such as in gas sensitivity or catalysis, or as advanced ceramic materials.     

单分散PS/SiO_2纳米复合微球的制备与表征

采用一种简单和低成本的方法制备单分散SiO2包覆聚苯乙烯(PS)(PS/SiO2)核-壳型纳米复合微球.首先在聚乙烯吡咯烷酮(PVP)存在下制备了PS纳米微球,然后在NH4OH/乙醇溶液中通过溶胶-凝胶过程在PS微球表面包覆SiO2.PS纳米微球的制备在水介质中进行,无需使用共单体,使用的是常用的过硫酸钾自由基引发剂;包覆处理前不用进行溶剂交换或离心处理.研究了PVP,NH4OH和原硅酸乙酯(TEOS)的用量对PS/SiO2纳米复合微球尺寸和形态的影响.随着PVP用量增加,PS微球变小,因此得到较小的PS/SiO2纳米复合微球;NH4OH用量对SiO2包覆层的厚度没有影响,但对SiO2包覆层的表面形态有影响,随着NH4OH用量增加包覆层表面变得粗糙;随着TEOS溶液用量增加,生成的SiO2增加,其包覆层的厚度增加.     

海藻酸改性的中空SiO2微球的简易制备及应用

以CaCO3为模板,正硅酸四乙酯（TEOS）为硅源,用比较简单的方法制备了中空SiO2;然后将海藻酸钠嫁接在氨基化的中空SiO2表面;再利用海藻酸盐与钙离子的作用,在中空SiO2表面形成一个凝胶化层,制得海藻酸盐凝胶化的中空SiO2微球,粒径为1~2 μm。 采用FTIR、XRD、SEM、TEM和TGA等测试技术对微球进行表征。 此微球成功地用于柔红霉素的载负和缓释,最大载负率和载药量分别为55.6%和27.8%;缓释结果表明,海藻酸盐凝胶化层的存在,能更有效控制柔红霉素缓慢的释放,这种凝胶化载体对药效强、毒性较大的药物有潜在的临床应用前景。     

Synthesis of Hollow Mesoporous TiO2 Microspheres with Single and Double Au Nanoparticle Layers for Enhanced Visible‐Light Photocatalysis

A facile method was used to prepare hollow mesoporous TiO₂ and Au@TiO₂ spheres using polystyrene (PS) templates. Au nanoparticles (NPs) were simultaneously synthesized and attached on the surface of PS spheres by reducing AuCl₄^? ions using sodium citrate which resulted in the uniform deposition of Au NPs. The outer coating of titania via sol‐gel produced PS@Au@TiO₂ core–shell spheres. Removing the templates from these core–shell spheres through calcination produced hollow mesoporous and crystalline Au@TiO₂ spheres with Au NPs inside the TiO₂ shell in a single step. Anatase spheres with double Au NPs layers, one inside and another outside of TiO₂ shell, were also prepared. Different characterization techniques indicated the hollow mesoporous and crystalline morphology of the prepared spheres with Au NPs. Hollow anatase spheres with Au NPs indicated enhanced harvesting of visible light and therefore demonstrated efficient catalytic activity toward the degradation of organic dyes under the irradiation of visible light as compared to bare TiO₂ spheres.     

制备核-壳结构聚合物纳米微球和空心球的原位聚合方法的普适性研究

采用原位聚合制备核-壳结构聚合物纳米微球和空心球的新方法, 利用甲基丙烯酸2-羟丙酯(HPMA)和乙酸乙烯酯(VAc)两种单体, 在类似的反应条件下, 成功地制备了以聚(ε-己内酯)(PCL)为核, 分别以交联PHPMA和PVAc为壳的纳米微球; 将微球的核酶解后, 分别得到了对应的交联PMAA空心球和交联PVA空心球. 结果表明, 原位聚合制备核-壳结构聚合物微球的新方法具有一定的普适性, 适用于单体可溶于水而生成的聚合物不溶于水的体系.