SiO2/COPs的合成及其在光催化反应中的协同效应

共价有机聚合物(COPs)是一类由轻质元素(C,H,O,N和B等)通过共价键的方式连接而成的有机多孔材料.COPs的共轭结构赋予其优异的可见光吸收特性,已经在光催化水分解制氢、二氧化碳还原、有机合成和污染物降解等领域显示出巨大的应用潜力.虽然COPs具有能带结构易调控和高孔隙率等优点,但其光催化活性仍有待提升.使用助催化剂是提升COPs的光催化活性,促进表面反应普遍采用的策略.此外,底物活化官能团的引入和光催化剂表面性质的调控也是提高光催化剂反应活性的有效方法.虽然可以通过改变COPs单体种类、化学键的类型和拓扑结构来调控COPs的组成,但要同时兼顾COPs的结构和亲疏水性的调控以及底物活化官能团的引入仍十分困难.与纯COPs相比,与其他材料进行杂化为扩大COPs的化学组成和功能性提供了更多可能.迄今为止,在COPs纳米孔中封装分子、纳米颗粒或将COPs涂覆在其他固体材料上是制备基于COPs复合材料的常用策略.但是,考虑到COPs和无机材料合成条件的不相容性,在纳米尺度精确控制复合材料的组分、结构和形貌仍然是一项艰巨的任务.本文制备了稳定在十六烷基三甲基溴化铵(CTAB)疏水核中的COPs胶体,其粒度分布在16 nm左右.通过溶胶-凝胶法在CTAB周围水解聚合四乙氧基硅烷,得到SiO2/COPs复合材料.表征结果表明,COPs均匀分布在氧化硅的骨架中.该复合材料具有分别来自于SiO2和COPs的介孔和微孔结构.与纯COPs相比,复合材料的表面疏水性降低.SiO2/COPs具有可见光响应特性,其吸收带边随COPs含量的增加而红移,表明在复合材料中COPs在高含量时发生团聚.SiO2/COPs作为光催化剂,可高效催化α-溴代苯乙酮的还原脱卤反应(汉斯酯为还原剂),其催化活性和SiO2/COPs比例相关,在COPs含量为22.6 wt％时达到最优.SiO2/COPs的催化活性较COPs有大幅度提高.在优化的SiO2/COPs比例下,SiO2/COPs的TOF是COPs的近12倍.控制实验表明,SiO2中的羟基对汉斯酯为还原剂有活化作用.此外,本文研究发现,复合材料的活性与SiO2/COPs的比值呈火山型曲线,表明在光催化反应中SiO2和COPs之间存在协同效应.由此可见,将光催化剂和反应物活化材料耦合是提高光催化反应活性的有效策略.     

Fabrication of flowerlike polymer superstructures using polymer/zeolite composites prepared with supercritical CO2

We report a route to the fabrication of unique flowerlike polymer superstructures with uniform petals at the nanoscale. In this method, polymer/zeolite composite is first prepared by loading corresponding monomer and initiator into the channels of the host zeolite with the aid of supercritical (SC) CO2, followed by thermal polymerization of monomers in the channels of the zeolite. The resultant polymer/zeolite composite is then treated with HF aqueous solution to allow the self-aggregation of the polymer and the inorganic components to form the polymeric layers and inorganic layers. Unique microscale flowerlike polymer superstructures are obtained after further treatment with HF aqueous solution. Different techniques, such as scanning electron microscopy (SEM), X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), and thermogravimetry (TG), have been used to characterize the microflowers.     

Structure of composites prepared via polypyrrole synthesis in supercritical CO2 on microporous polyethylene

The synthesis of polypyrrole in supercritical carbon dioxide in the presence of the microporous polyethylene has been studied. Formation of polymer composites based on polypyrrole and polyethylene has been demonstrated. The structure of the test samples has been investigated by vibrational spectroscopy, SAXS, and atomic force and scanning electron microscopy. It has been discovered that the oxidized structure of polypyrrole forms during the synthesis under supercritical conditions.     

超临界CO_2技术在高分子科学中应用的研究进展

本文综述了超临界CO_2的特殊性质，如溶解能力和溶胀能力随压力急剧变化等，总结了它在高分子科学中的应用，包括以它为介质的溶液聚合、乳液聚合、分散聚合、沉淀聚合反应及RESS技术、分级技术等．     

N-K2Ti4O9/UiO-66-NH2复合材料的协同效应及其光催化降解阳离子型染料

半导体光催化剂作为一种可再生和可持续降解有机污染物的材料被广泛研究.K2Ti4O9由于无毒、低成本、稳定的物理化学性质和独特的光电性能被应用于光催化反应.但是,K2Ti4O9只能被紫外光所激发(因为其带隙能为3.2-3.4 eV),所以大量工作致力于研究如何降低其带隙能,从而使其可以被太阳光中的可见光激发,扩大其应用范围.其中N元素掺杂K2Ti4O9 (N-K2Ti4O9)是最常见的方法之一.单纯的N-K2Ti4O9虽然具有光催化能力,但其吸附容量太小,不能有效地将溶液中的有机物吸附至其表面,因而催化降解有机物效果不显著.UiO-66-NH2是一种Zr基金属-有机骨架化合物,它对阳离子染料具有良好的吸附性能,且具有一些常规无机半导体光催化材料所没有的性质.本文将UiO-66-NH2和N-K2Ti4O9经高温焙烧制备了N-K2Ti4O9/UiO-66-NH2复合材料,发现该复合材料不仅具有UiO-66-NH2优良的吸附性能,还因为复合提高了其光电性能,从而大大提高了光催化性能,当N-K2Ti4O9/ZrCl4质量比为3∶7时光催化性能最佳.为了考察N-K2Ti4O9/UiO-66-NH2复合材料的微观形貌、复合结构及光生电子-空穴分离效率,首先通过场发射透射电镜分析N-K2Ti4O9,UiO-66-NH2和N-K2Ti4O9/UiO-66-NH2(3∶7)复合材料的形貌,然后采用能量散射谱测定复合材料的元素分布,并利用N-K2Ti4O9和UiO-66-NH2中代表性元素K,Ti和Zr的分布判断复合材料的复合结构,最后运用高分辨电镜观察复合材料中N-K2Ti4O9和UiO-66-NH2的异质结界面,确定了两者是通过自组装复合在一起,而不是简单的物理混合.X射线衍射结果表明,复合材料具有N-K2Ti4O9和UiO-66-NH2两者的特征衍射峰,仅在强度和位置上略有变化.这可能是N-K2Ti4O9/UiO46-NH2异质结构所致.通过UiO-66-NH2和N-K2Ti4O9的紫外-可见吸收光谱,用公式计算出它们的带隙能分别是2.645和3.195 eV,与文献结果基本一致.由于光催化剂的光生载流子迁移速率同样影响光催化性能,因此我们在CHI-660D电化学工作站上控制光源反复开关数次,同时记录N-K2Ti4O9,UiO-66-NH2和N-K2Ti4O9/UiO-66-NH2(3∶7)的光响应电流,发现N-K2Ti4O9/UiO-66-NH2(3∶7)复合材料展现出最高的光响应电流强度,表明其具有最高的光生载流子迁移速率和最低的光生载流子复合速率.可见,N-K2Ti4O9和UiO-66-NH2复合有利于光生载流子迁移,这可能是由于N-K2Ti4O9/UiO-66-NH2异质结界面有利于光生载流子在两种材料之间迁移所致.测试了N-K2Ti4O9/UiO-66-NH2(3∶7)复合材料对不同染料的光催化降解性能.结果发现,该材料对阳离子型染料(罗丹明B和亚甲基蓝)的光催化性能远远高于对阴离子型染料(甲基橙和刚果红).这是由于它对阳离子型染料的吸附性能远高于对阴离子型染料,因此N-K2Ti4O9/UiO-66-NH2复合材料对阳离子型染料具有选择性光催化.     

One-pot synthesis of highly luminescent InP/ZnS nanocrystals without precursor injection

InP/ZnS core/shell nanocrystals are prepared using a single-step heating-up method relying on the difference in reactivity of the applied InP and ZnS precursors. The obtained particles exhibit size-dependent emission in the range of 480-590 nm, a fluorescence quantum yield of 50-70%, and high photostability.     

One-pot synthesis of new symmetric and asymmetric xanthene dyes

Symmetric and asymmetric xanthene dyes have been prepared by a convenient one-step procedure from aldehyde and diol or m-aminophenol precursors using concentrated phosphoric acid as a solvent. This protocol provides access to water-soluble dyes with large Stoke’s shifts and far-red fluorescence emission. These compounds are envisioned as components of fluorescence-based sensors for a variety of imaging applications.     

以CO_2和环氧氯丙烷为底物一锅合成碳酸甘油酯

以环氧氯丙烷和CO2为底物,三乙胺作为溶剂和CO2活化试剂,一锅合成碳酸甘油酯.该方法反应条件温和,反应收率较高,所使用的底物环氧氯丙烷工业上可由甘油制得,因此该方法直接和间接地利用了CO2和甘油两个工业副产物,并为碳酸甘油酯的合成提供了一种高效实用的方法.     

One-pot synthesis, photoluminescence, and photocatalysis of Ag/ZnO composites

One-pot synthesis of Ag/ZnO composites is described by a simple hydrothermal approach. In the reaction process, hexamethylenetetramine (HMT) can convert into ammonia and formaldehyde, which are used as a precipitant for the fabrication of ZnO and a reducing agent for the loading of metal Ag, respectively. The UV emission of ZnO is obviously enhanced by the deposition of silver islands on its surface. The photocatalytic characterization reveals that the composites behave high photocatalytic activity for a solution of rhodamine B. The influence of Ag+ ions on the morphology of ZnO is discussed. The composites are characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), and photoluminescence (PL).     

Direct synthesis of zirconia aerogel nanoarchitecture in supercritical CO2

The objective of the present study was to synthesize porous ZrO2 aerogels with a nanostructure via a direct sol-gel route in the green solvent supercritical carbon dioxide (scCO2). The synthesis involved the coordination and polycondensation of a zirconium alkoxide using acetic acid in CO2, followed by scCO2 drying and calcination. Either a translucent or opaque monolith was obtained, which was subsequently characterized by electron microscopy, X-ray diffraction, thermal analysis, N2 physisorption, and infrared spectroscopy analysis. The electron microscopy results showed that the translucent monolithic ZrO2 exhibited a well-defined mesoporous structure, while the opaque monolith, formed using added alcohol as a cosolvent, was composed of loosely compacted nanospherical particles with a diameter of ca. 20 nm. After calcination at 400 and 500 degrees C, X-ray diffraction results indicated that the ZrO2 exhibited tetragonal and/or monoclinic phases. In situ infrared spectroscopy results showed the formation of a Zr-acetate coordinate complex at the initial stage of the polycondensation, followed by further condensation of the complex into macromolecules.     

One-pot hydrothermal synthesis of heterostructured ZnO/ZnS nanorod arrays with high ethanol-sensing properties

ZnO/ZnS heterostructured nanorod arrays with uniform diameter and length were synthesized from zinc substrates in a one-pot procedure by using a simple hydrothermal method. Structural characterization by HRTEM indicated that the heterostructured nanorods were composed of parallel segments of wurtzite-type ZnO and zinc-blende ZnS, with a distinct interface along the axial direction, which revealed the epitaxial relationship, ZnO (1010) and ZnS (111). The as-prepared ZnO/ZnS nanorods showed only two green emissions at around 523?nm and 576?nm. We also found that the nanorods exhibited high sensitivity to ethanol at relatively low temperatures, owing to their smaller size and structure.     

Facile synthesis of ZnS/MnS nanocomposites for supercapacitor applications

Journal of Solid State Electrochemistry - In this study, we have reported a facile fabrication of pristine zinc sulfide (ZnS), manganese sulfide (MnS), and ZnS/MnS nanocomposites (NCs) via...     

Micronization of phenylbutazone by rapid expansion of supercritical CO2 solution

Rapid expansion of supercritical solutions (RESS) technique was applied for the preparation of phenylbutazone fine particles. The operating temperature and pressure affected the yield of the drug fine particles, which was evaluated by dissolving the sprayed product of drug into ethanol. Effect of pre- and post-expansion conditions on the particle size distribution of phenylbutazone was investigated and the smallest sample (mean particle size: 1.59 microm) was obtained when the RESS method was operated at a pressure of 26 MPa combined with a temperature of 32 degrees C. Physicochemical properties of the fine particles were investigated by powder X-ray diffraction and differential scanning calorimetry. It was found that the phenylbutazone fine particles obtained were meta-stable beta form under the experimental conditions tested, suggesting polymorphic transformation during the RESS process.     

Organometallic synthesis and electrophoretic characterization of high-quality ZnS:Mn/ZnS core/shell nanoparticles for bioanalytical applications

A novel and facile preparation method for colloidal ZnS nanoparticles doped with Mn²⁺ is introduced, using a simple one pot heating process followed by a capping procedure for saturation of the surface bound doping atoms to increase the nanoparticles’ stability and photoluminescence quantum yield. The particles were transferred into water with a standard ligand exchange method and investigated by means of laser Doppler electrophoresis, agarose gel electrophoresis, and isotachophoresis. Correspondence: Alexey Merkulov, Freiburg Materials Research Centre (FMF), University of Freiburg, Stefan-Meier-Strasse 21, D-79104 Freiburg, Germany     

Novel one pot synthesis of silver nanoparticle-polymer composites by supercritical CO2 polymerisation in the presence of a RAFT agent

We report the one pot synthesis of a silver-polymer nanocomposite in supercritical carbon dioxide (scCO(2)) whereby an organometallic silver complex is thermally decomposed in the presence of a reversible addition fragmentation chain transfer (RAFT) agent during a polymerisation reaction in which the RAFT agent simultaneously stabilises the growing polymer microparticles and the formation of surface located silver nanoparticles.     

一锅法合成Ce_xZr_(1-x)O_2固溶体催化剂用于热化学循环分解CO_2制CO

采用一锅蒸发诱导自组装法(EISA)制备了一系列不同铈锆物质的量比的铈锆固溶体催化剂,用TGA研究了其热化学循环分解CO_2制CO的催化性能,并采用XRD、Raman光谱、H2-TPR、XPS、SEM和N_2吸附-脱附等手段对催化剂的物相结构、还原性能和表面化学性质进行了表征分析,用热重分析(TGA)研究了铈锆固溶体对热化学循环分解CO_2制CO的催化性能。结果表明,随着Ce/Zr物质的量比增加,铈锆固溶体催化剂的CO_2高温分解活性先增大后减小。Ce/Zr物质的量比为1的Ce_(0.5)Zr_(0.5)O_2催化剂由于具有较多的晶格缺陷和氧空穴,氧迁移能力强,催化活性高,而Ce/Zr物质的量比为3的Ce_(0.75)Zr_(0.25)O_2催化剂具有相对稳定的氧空穴数,循环稳定性好。循环反应后,所有的催化剂均出现了一定程度的烧结,且富锆固溶体发生了相分离,这可能会影响催化剂的性能。     

Photodegradation of a polyamidehydroxyurethane type polymer in aqueous solution. The role of some dyes in the degradation

The influence of some dyes on the photodegradation of a polyamidehydroxyurethane type polymer in aqueous solution has been studied. It has been found that, among the dyes used, only riboflavin sensitizes and accelerates the degradation of the polymer. It is proposed that under ultraviolet irradiation riboflavin undergoes photoreduction to lumichrome, which sensitizes the photodegradation of the polymer. It is also possible that the mechanism of photodegradation involves the participation of singlet oxygen.     

Hydrothermal synthesis of CuO micro-/nanostructures and their applications in the oxidative degradation of methylene blue and non-enzymatic sensing of glucose/H2O2

In this paper, we report on the amino acids-/citric acid-/tartaric acid-assisted morphologically controlled hydrothermal synthesis of micro-/nanostructured crystalline copper oxides (CuO). These oxides were characterized by means of X-ray diffraction, nitrogen sorption, scanning electron microscopy, Fourier transform infrared, and UV-visible spectroscopy. The surface area of metal oxides depends on the amino acid used in the synthesis. The formation mechanisms were proposed based on the experimental results, which show that amino acid/citric acid/tartaric acid and hydrothermal time play an important role in tuning the morphology and structure of CuO. The catalytic activity of as-synthesized CuO was demonstrated by catalytic oxidation of methylene blue in the presence of hydrogen peroxide (H(2)O(2)). CuO synthesized using tyrosine was found to be the best catalyst compared to a variety of CuO synthesized in this study. CuO (synthesized in this study)-modified electrodes were used for the construction of non-enzymatic sensors, which displayed excellent electrocatalytic response for the detection of H(2)O(2) and glucose compared to conventional CuO. The high electrocatalytic response observed for the CuO synthesized using tyrosine can be correlated with the large surface area, which enhances the accessibility of H(2)O(2)/glucose molecule to the active site that results in high observed current. The methodology adopted in the present study provides a new platform for the fabrication of CuO-based high-performance glucose and other biosensors.