Visualizing single-molecule diffusion in mesoporous materials

Periodic mesoporous materials formed through the cooperative self-assembly of surfactants and framework building blocks can assume a variety of structures, and their widely tuneable properties make them attractive hosts for numerous applications. Because the molecular movement in the pore system is the most important and defining characteristic of porous materials, it is of interest to learn about this behaviour as a function of local structure. Generally, individual fluorescent dye molecules can be used as molecular beacons with which to explore the structure of--and the dynamics within--these porous hosts, and single-molecule fluorescence techniques provide detailed insights into the dynamics of various processes, ranging from biology to heterogeneous catalysis. However, optical microscopy methods cannot directly image the mesoporous structure of the host system accommodating the diffusing molecules, whereas transmission electron microscopy provides detailed images of the porous structure, but no dynamic information. It has therefore not been possible to 'see' how molecules diffuse in a real nanoscale pore structure. Here we present a combination of electron microscopic mapping and optical single-molecule tracking experiments to reveal how a single luminescent dye molecule travels through linear or strongly curved sections of a mesoporous channel system. In our approach we directly correlate porous structures detected by transmission electron microscopy with the diffusion dynamics of single molecules detected by optical microscopy. This opens up new ways of understanding the interactions of host and guest.     

Electronic connection to the interior of a mesoporous insulator with nanowires of crystalline RuO2

Highly porous materials such as mesoporous oxides are of technological interest for catalytic, sensing and remediation applications: the mesopores (of size 2-50 nm) permit ingress by molecules and guests that are physically excluded from microporous materials. Connecting the interior of porous materials with a nanoscale or 'molecular' wire would allow the direct electronic control (and monitoring) of chemical reactions and the creation of nanostructures for high-density electronic materials. The challenge is to create an electronic pathway (that is, a wire) within a mesoporous platform without greatly occluding its free volume and reactive surface area. Here we report the synthesis of an electronically conductive mesoporous composite--by the cryogenic decomposition of RuO4--on the nanoscale network of a partially densified silica aerogel. The composite consists of a three-dimensional web of interconnected (approximately 4-nm in diameter) crystallites of RuO2, supported conformally on the nanoscopic silica network. The resulting monolithic (RuO2//SiO2) composite retains the free volume of the aerogel and exhibits pure electronic conductivity. In addition to acting as a wired mesoporous platform, the RuO2-wired silica aerogel behaves as a porous catalytic electrode for the oxidation of chloride to molecular chlorine.     

无机介孔材料在第三代电化学生物传感器中的应用研究

无机介孔材料是一种孔直径在2,50nm的多孔材料。这种材料具有结构规则,机械性能高、化学和热能稳定性好等特点。近年来,随着材料合成技术的提高,不断有新型高负载能力和生物相容性好的介孔材料被开发出来。同时,实验表明,无机介孔材料是固载生物大分子的良好载体。利用无机介孔材料固载氧化还原蛋白质并结合其的直接电子转移,为我们提供了一种新的构建第三代生物传感器的方法。基于无机介孔材料的特点及氧化还原蛋白质的直接电子转移,所构建的第三代电化学生物传感器有望具有较传统电化学传感器更好的性能。将介孔材料分为二氧化硅基和非二氧化硅基2大类,描述了无机介孔材料在第三代电化学生物传感器中的应用。     

李政, 宋益善, 左思语,刘超,马晨晨

氨基酸分子首次用以制备构筑稀土介孔发光材料.L-丝氨酸通过分子修饰得到新配体2-烟酰氨基-3-羟基丙酸(L),并进一步引入MCM-41介孔基质中,最后和稀土Tb3+离子复合得发光介孔材料Tb-L-MCM-41.通过核磁共振、紫外、XRD、氮吸附和荧光光谱等对配体和杂化材料的结构和性质进行了表征.结果表明,配体L很好的引入到MCM-41介孔基质中,Tb-L-MCM-41介孔材料呈现L的特征紫外吸收.同时,稀土配合物的引入占据了MCM41基质的部分孔道,使其比表面和孔体积都有所降度.Tb-L-MCM-41呈现稀土Tb3+离子的特征光.     

Synthesis of a new meso／microporous composite molecular sieve of MCM-41／mordenite

An MCM-41/mordenite composite with twofold porous structure and stepwise-distributed acidity was prepared for the first time by using zeolite mordenite as the silica-alumina source. The composite molecular sieve has been investigated and compared with a mechanical mixture of mordenite and MCM-41 for their structure, acidity and catalytic activity by means of XRD, N2 adsorption and desorption, HRTEM, DTG, NH3-TPD and catalytic reaction. The characterization results show that the structure and property of the composite molecular sieve are quite different from those of the mechanical mixture, which might be ascribed to the incorporation of secondary building units characteristic of zeolite mordenite into the mesoporous walls of the composite which gives rise to the thicker mesoporous walls, the higher hydrothermal stability and more strong acid sites. Furthermore, the new strategy could be used as a new general method for the preparation of catalysts for the reaction system with multifold large molecules, and the results were well confirmed by the dealkylation of C10^ aromatic hydrocarbon.     

SBA-15基功能材料吸附应用研究进展

介孔SBA-15分子筛因具有较大的孔径、较高的比表面积和较厚的孔壁,在催化、吸附、分离、药物控释以及化学传感等领域得到广泛的应用。介绍了介孔分子筛的发展过程,并着重就SBA-15基功能材料在吸附应用方面的研究状况进行概述,最后展望了SBA-15功能材料未来的发展方向与应用前景。     

改性硅基介孔材料去除废水中重金属研究进展

对硅基介孔材料的功能化改性进行了系统的分析调研.在概述硅基介孔材料基本性质和改性条件的基础上,总结了对其进行改性的三类主要方法及其改性原理,包括无机、有机、无机-有机复合改性.针对各类改性方法,详细综述了硅基介孔材料改性前后性质的变化特点,以及对重金属的吸附效果和吸附机理,并对改性硅基介孔材料吸附重金属的关键影响因素进行了探讨.     

Hexagonal nanoporous germanium through surfactant-driven self-assembly of Zintl clusters

Surfactant templating is a method that has successfully been used to produce nanoporous inorganic structures from a wide range of oxide-based material. Co-assembly of inorganic precursor molecules with amphiphilic organic molecules is followed first by inorganic condensation to produce rigid amorphous frameworks and then, by template removal, to produce mesoporous solids. A range of periodic surfactant/semiconductor and surfactant/metal composites have also been produced by similar methods, but for virtually all the non-oxide semiconducting phases, the surfactant unfortunately cannot be removed to generate porous materials. Here we show that it is possible to use surfactant-driven self-organization of soluble Zintl clusters to produce periodic, nanoporous versions of classic semiconductors such as amorphous Ge or Ge/Si alloys. Specifically, we use derivatives of the anionic Ge9(4-) cluster, a compound whose use in the synthesis of nanoscale materials is established. Moreover, because of the small size, high surface area, and flexible chemistry of these materials, we can tune optical properties in these nanoporous semiconductors through quantum confinement, by adsorption of surface species, or by altering the elemental composition of the inorganic framework. Because the semiconductor surface is exposed and accessible in these materials, they have the potential to interact with a range of species in ways that could eventually lead to new types of sensors or other novel nanostructured devices.     

介孔硅铝酸盐材料的合成、 表征及催化应用

采用NaOH调节体系的pH值, 通过改变造孔剂柠檬酸的加入量, 制备了一系列新型介孔硅铝酸盐材料, 并利用X射线衍射(XRD)、 透射电镜(TEM)和N₂吸附脱附等进行表征, 同时分析了不同柠檬酸加入量对材料孔结构的影响.  结果表明： 合成材料具有蠕虫状内交联的介孔结构,   具有较强的酸性; 柠檬酸与铝物质的量比为13的样品在苯酚与叔丁醇烷基化反应中具有较高的催化活性和对2,4-二叔丁基苯酚（2,4-DTBP）的选择性; 较高的苯酚转化率和对2,4-DTBP的选择性主要归因于催化剂较强的酸性和较大的介孔孔径.     

不同合成方法对Y/SBA-15复合分子筛的结构的影响

研究了微波水热法合成的Y/SBA—15复合分子筛与普通机械方法将Y和SBA—15混合制备的混合分子筛。采用XRD、IR、氮气吸附脱附和TEM等方法对两种分子筛进行结构表征,结果表明:红外具有565、693、958 cm-1等微孔、介孔特征峰且有偏移,孔径为1.8、6.1 nm,微波水热法合成的分子筛是同时具备微孔和介孔特征的复合分子筛,而不是简单的机械混合分子筛。     

碱处理法制备微孔 介孔ZSM-5分子筛及其在苯酚叔丁醇烷基化反应中的应用#br#

首先, 以微孔结构的ZSM-5沸石为前驱物, 经碱液处理不同时间后与介孔模板剂十六烷基三甲基溴化铵（CTAB）混合, 水热处理后制备微孔-介孔ZSM-5分子筛, 并用X射线衍射（XRD）、 Fourier变换红外光谱（FT-IR）、 N₂吸附 脱附和透射电镜（TEM）等方法表征微孔-介孔ZSM-5分子筛的理化性质. 其次, 将微孔 介孔ZSM-5分子筛作为苯酚叔丁醇烷基化反应的催化剂, 利用苯酚转化率与2,4-二叔丁基苯酚的选择性测试所得材料的催化性能. 结果表明: [JP2]碱处理1 h可获得微孔和介孔复合较好的ZSM-5, 且该催化剂具有较好的苯酚叔丁基化催化性能, 苯酚的转化率最高为86.2%, 大分子2,4 二叔丁基苯酚的选择性可达57.9%.     

Synthesis of mesoporous MCM-48 with a mixed nonionic-cationic surfactant templating pathway

In a hydrothennal system, we studied the influence of nonionic surfactant poly(ethylenglycol) monooc-tylphenyl ether (OP-10) on the self-assembling process of mesoporous molecular sieve MCM-48 and found that OP-10 can decrease the amount of cationic surfactant needed for the preparation of MCM-48 further by its stronger van der Waals force , shorten the synthetic period and produce MCM-48 with more extensive cross-linked framework. By altering the ratio of nonionic surfactant to cationic surfactant, we could obtain the mesoporous molecular sieves with different structures. When the crystallization temperature exceeded -140℃, OP-10 would separate from micelle, lose its amphiphilic character , and then hamper the conversion of lamellar mesoporous molecular sieves into microporous materials.     

类毛线团表面银微球的制备及其表面增强拉曼散射性能研究

以低分子量聚丙烯酰胺（PAM）为模板,通过液相化学还原法首次制备了类毛线团表面银微球,并采用扫描电子显微镜（SEM）、X射线衍射（XRD）及氮气吸附法对银微球形貌及分散性进行表征。结果表明,微球是由纳米片有序组装而成的介孔材料,表面遍布棱角和狭缝。考察了PAM分子量、硝酸银浓度及还原体系pH值变化对银球结构的影响,并对类毛线团表面的形成过程进行了阐述。将银球用作表面增强拉曼散射（SERS）检测基底,可显著地增强罗丹明B（Rh B）分子的拉曼信号强度,能够检测出浓度低至10^-16mol/L的Rh B。     

基于SiC和BC5的多孔材料设计及储氢性能研究

基于金刚石结构的SiC晶体和类似金刚石结构的BC5晶体设计了多孔材料,并用分子力学方法对其进行优化得到平衡态结构.利用GCMC对其在温度为298 K和77 K,压强为0-100 bar的条件下的储氢量、氢分子密度分布和等量吸附热进行了讨论.考虑孔内壁以化学吸附的氢在内,基于SiC晶体设计的多孔材料储氢量比Si C纳米管的结果更理想.氢分子密度分布图表明氢分子在孔道中的分布距孔道边缘有一定的距离,此距离与氢分子动力学直径2.89A相当.等量吸附热表明材料在温度为298 K和77 K对氢分子的吸附都是物理吸附.     

Free-standing mesoporous silica films with tunable chiral nematic structures

Chirality at the molecular level is found in diverse biological structures, such as polysaccharides, proteins and DNA, and is responsible for many of their unique properties. Introducing chirality into porous inorganic solids may produce new types of materials that could be useful for chiral separation, stereospecific catalysis, chiral recognition (sensing) and photonic materials. Template synthesis of inorganic solids using the self-assembly of lyotropic liquid crystals offers access to materials with well-defined porous structures, but only recently has chirality been introduced into hexagonal mesostructures through the use of a chiral surfactant. Efforts to impart chirality at a larger length scale using self-assembly are almost unknown. Here we describe the development of a photonic mesoporous inorganic solid that is a cast of a chiral nematic liquid crystal formed from nanocrystalline cellulose. These materials may be obtained as free-standing films with high surface area. The peak reflected wavelength of the films can be varied across the entire visible spectrum and into the near-infrared through simple changes in the synthetic conditions. To the best of our knowledge these are the first materials to combine mesoporosity with long-range chiral ordering that produces photonic properties. Our findings could lead to the development of new materials for applications in, for example, tuneable reflective filters and sensors. In addition, this type of material could be used as a hard template to generate other new materials with chiral nematic structures.     

储层多孔介质中烃类液体非平衡吸附实验研究

油气体系在地层多孔介质中储集和渗流,与储层多孔介质形成一个相互作用的系统.由于储层岩石孔隙小、比表面大,部分流体将吸附于孔隙表面,形成吸附相,进而影响流体相态和渗流规律,尤其在低渗透多孔介质中,吸附现象更为严重.在分析研究多孔介质中液烃吸附特点的基础上,进行了真实岩心中三元烃类液体混合物的吸附实验研究.研究结果表明,对于低渗透储层,吸附的影响不能忽略.     

A mesoporous germanium oxide with crystalline pore walls and its chiral derivative

Microporous oxides are inorganic materials with wide applications in separations, ion exchange and catalysis. In such materials, an important determinant of pore size is the number of M (where M = Si, Ge and so on) atoms in the rings delineating the channels. The important faujasite structure exhibits 12-ring structures while those of zeolites, germanates and other materials can be much larger. Recent attention has focused on mesoporous materials with larger pores of nanometre scale; however, with the exception of an inorganic-organic hybrid, these have amorphous pore walls, limiting many applications. Chiral porous oxides are particularly desirable for enantioselective sorption and catalysis. However, they are very rare in microporous and mesoporous materials. Here we describe a mesoporous germanium oxide, SU-M, with gyroidal channels separated by crystalline walls that lie about the G (gyroid) minimal surface as in the mesoporous MCM-48 (ref. 9). It has the largest primitive cell and lowest framework density of any inorganic material and channels that are defined by 30-rings. One of the two gyroidal channel systems of SU-M can be filled with additional oxide, resulting in a mesoporous crystal (SU-MB) with chiral channels.     

三聚氰胺改性酚醛基多孔碳材料的制备及其二氧化碳吸附性能

采用浓乳液模板法制备三聚氰胺-间苯二酚-甲醛多孔树脂,将其热解后得到了可用于二氧化碳吸附的氮掺杂多孔碳材料。研究了浓乳液模板的分散相体积分数和三聚氰胺含量对多孔碳材料微观形貌的影响,结果表明,在浓乳液模板分散相体积分数为90%的条件下制备的多孔聚合物具有丰富的通孔结构。经过热解后,得到了兼具无机碳骨架和有机氮活性位点的氮掺杂多孔碳材料。进一步研究了不同热解温度和三聚氰胺含量对多孔碳材料二氧化碳吸附性能的影响,二氧化碳的吸附容量最高可达到3.32 mmol/g,同时表现出良好的选择吸附性和再生性。     

水杨醛希夫碱功能化介孔硅基吸附剂制备及其对水体中Cu(Ⅱ)离子的吸附性能研究

采用后嫁接法制备了水杨醛希夫碱功能化介孔硅基吸附材料SA-SBA-15,对Cu(II)离子的饱和吸附量为60.0 mg/g,最佳溶液pH值为5.动力学研究表明,合成的SA-SBA-15对Cu(II)离子的吸附40 min达到平衡.吸附Cu(II)离子后形成的Cu-SA-SBA-15具有良好的杀菌性能,对大肠杆菌的最小抑菌浓度为160μg/mL,对金黄色葡萄球菌的最小抑菌浓度为120μg/mL.     

A titanosilicate molecular sieve with adjustable pores for size-selective adsorption of molecules

Zeolites and related crystalline microporous oxides-tetrahedrally coordinated atoms covalently linked into a porous framework-are of interest for applications ranging from catalysis to adsorption and ion-exchange. In some of these materials (such as zeolite rho) adsorbates, ion-exchange, and dehydration and cation relocation can induce strong framework deformations. Similar framework flexibility has to date not been seen in mixed octahedral/tetrahedral microporous framework materials, a newer and rapidly expanding class of molecular sieves. Here we show that the framework of the titanium silicate ETS-4, the first member of this class of materials, can be systematically contracted through dehydration at elevated temperatures to 'tune' the effective size of the pores giving access to the interior of the crystal. We show that this so-called 'molecular gate' effect can be used to tailor the adsorption properties of the materials to give size-selective adsorbents suitable for commercially important separations of gas mixtures of molecules with similar size in the 4.0 to 3.0 A range, such as that of N2/CH4, Ar/O2 and N2/O2.