Metal,semiconductor and magnetic nanoparticle inclusions in gels

A room temperature chemical process has been developed to prepare composite materials formed of different nanometer particles trapped in a glass matrix. This involves a controlled precipitation of the crystallites using usual techniques of colloid chemistry, a grafting of a functionalized alkoxide on the particles and a sol-gel synthesis of transparent oxide matrices.     

表面自由基链转移反应制备超萍聚合物膜

研究了通过自由基链转移反应原位接枝聚合物膜。所得聚合物膜经红外（FT- IR）、X射线光电子能谱（XPS）、原子力显微镜（AFM）、接触角及椭圆偏光测量 进行了表征。两种单体如苯乙烯/甲基丙烯酸甲酯共聚合时,改变单体对的组成, 可以得到不同亲水亲油性质的表面。     

Syntheses and characterization of nanometer-sized semiconductor clusters

During the past few years a wide variety of synthetic teainiques have been developed to prepare semiconductor clusters in the nanometer size regime. These clusters possess properties which are intermediate between the molecular and bulk limits and can be considered a new class of materials. In this paper, we review their synthesis and discuss recent developments as well as possible future directions.     

液相法制备纳米氧化锡防团聚方法综述

针对液相法制备纳米氧化锡颗粒团聚的问题,以溶胶-凝胶法为例,介绍了防团聚的几种措施:加入表面活性剂,有机溶剂洗涤,共沸蒸馏及冷冻干燥等.这几种方法虽可以制备出粒径较小,均匀,分散性好的粒子,但也各有优缺点:反应时加入表面活性剂,容易引入杂质;有机溶剂洗涤廉价而便利,但是存在洗涤凝胶滤饼时溶剂漏滤的问题;而共沸蒸馏需要特殊的减压装置,比较看来,利用有机溶剂洗涤是一种相对方便的办法.     

Zeolite synthesis by simulation of their natural formation conditions: from macroscopic to nanosized crystals

A successful route to prepare zeolites with controlled crystal size from the millimeter range down to nanometer scale by simulating the natural formation conditions is presented. Water is used as the solution and reaction medium at high temperatures and pressures (T=120-400°C, p=1 kbar); aluminosilicate glasses with identical chemical composition as the zeolite products are used as precursors. The synthesis of heulandite is reported as representative example.     

Studies on the ultra-fine transition metal particles dispersed in polymer matrix

A series of complexes of styrene-4-vinylpyridine copolymers (SVP) or poly(4-vinylpyridine) (PVP) and transition metal chlorides were prepared. The transition metal-polymer complexes were used to prepare the ultra-fine metallic particles dispersed in polymer matrix by chemical reduction. The effects of the ion concentration and the polymer backbone on the size of these metal particles were studied. It was found that the transition metal ions may coordinate to pyridine groups in precursor polymers after blending. Upon reduction, the metal ions were transformed into the corresponding metal particles in the range of nanometer scale. The protective polymers take an important role to prevent metal particles from oxidation and excessive aggregation.     

Atomic force microscopy of microbial cells: application to nanomechanical properties, surface forces and molecular recognition forces

In recent years, the physical properties and interaction forces of microbial cell surfaces have been extensively studied using atomic force microscopy (AFM). A variety of AFM force spectroscopy approaches have been developed for investigating native cell surfaces with piconewton (nanonewton) sensitivity and nanometer lateral resolution, providing novel information on the nanomechanical properties of cell walls, on surface forces such as van der Waals and electrostatic forces, solvation and steric/bridging forces, and on the forces and localization of molecular recognition events. The intention of this article is to survey these different applications and to discuss related methodologies (how to prepare tips and samples, how to record and interpret force curves).     

Preparation and Optical Properties of (Nanometer MCM-41)-CdS Composite Materials

The nanometer and micrometer molecular sieves MCM-41 were prepared by a hydrothermal method. Cadmium (II) was exchanged into the molecular sieves by ion-exchange, and thioacetamide was then used as a precursor of hydrogen sulfide for sulphidizing the (MCM-41)-cadmium samples to prepare the host-guest composite materials (MCM-41)-CdS. By means of chemical analysis, powder X-ray diffraction, infrared spectroscopy, low temperature nitrogen adsorption-desorption technique, solid state diffuse reflectance absorption spectroscopy and luminescence, the prepared materials were characterized. The chemical analysis shows that the guest is successfully trapped in the molecular sieves. The powder X-ray diffraction suggests that the frameworks of the molecular sieves in the prepared host-guest composite materials are retained during the preparative process. They are intact and the degrees of crystallinity are still very high. The infrared spectra show that the frameworks of the prepared host-guest materials keep intact. The low temperature nitrogen adsorption-desorption studies indicate that the pore volumes, the pore sizes and the surface areas of the prepared composite materials decrease relative to those of the MCM-41 molecular sieve hosts. This shows that the guests are successfully encapsulated in the channels of the molecular sieves. The solid state diffuse reflectance absorption spectra of the prepared host-guest composites show some blue-shifts relative to that of bulk cadmium sulfide, indicating that the guests are trapped in the channels of the molecular sieves. This shows the obvious stereoscopic confinement effect of the molecular sieve host on the nanometer cadmium sulfide guest. The (nanometer MCM-41)-CdS and (micrometer MCM-41)-CdS samples show obvious luminescence.     

生物形态的高性能材料

经过长期进化,生物质已经形成了复杂的分级胞状结构.这些结构为生物体生长和发育提供了传输水分和营养物质的快速通道.由生物质转化形成的高性能材料,不仅保持了材料本身的优良性质,而且还具有生物质的宏观形貌和微观结构特征.由于具有丰富的分级多孔结构和优良的机械性能,生物形态材料在催化、分离与吸附和高温尾气处理等领域具有广泛的应用前景.目前,各种不同类型的生物质已被广泛用来制备生物形态的高性能材料.本文结合国内外研究进展综述了生物形态材料的制备技术、材料种类以及应用情况.     

低温等离子体制备与改性纳米催化材料的研究进展

低温等离子体属于非热平衡等离子体,它具有较高的电子温度和较低的气体温度,是一种纳米催化剂制备与改性的新方法。 低温等离子体因其高效、环境友好、材料易实现功能化等特点在制备和改性纳米催化材料方面引起了广泛关注,在纳米催化材料的非常规制备、掺杂、缺陷和空位制造中展现了突出的优势,因而被广泛用于各类催化剂的制备与改性中。 本文主要综述了低温等离子体在氧还原(ORR)、氧析出(OER)、析氢(HER)和燃料氧化反应(FOR)催化剂制备与改性方面的研究进展,从不同角度阐述了上述各类催化剂性能改善的原因,并对低温等离子体在纳米催化剂制备与改性方面存在的成本相对较高、反应器放大、材料可控制备等挑战进行了总结,最后对等离子体制备与改性纳米催化剂的发展趋势进行了预测。     

Synthesis of cross-linked enzyme aggregates (CLEAs) in CO2-expanded micellar solutions

A new method to prepare the cross-linked enzyme aggregates (CLEAs) was developed. Through cross-linking the enzyme (Trypsin) aggregates, which was precipitated from the CO2-expanded reverse micellar solutions, dendritic CLEAs were obtained. The sizes of the CLEAs prepared by this new method were nanometer order of magnitudes and could be tuned by changing the water-to-surfactant ratio (w0) and the concentration of enzyme in the reverse micellar solution. The diameter of CLEAs increased with increasing w0 value of reverse micelles and the concentration of Trypsin. The activity of CLEAs obtained by this method is improved in contrast to those obtained by the conventional method. This method has some advantages in applications and can be easily applied to the synthesis of other cross-linked enzyme aggregates.     

染料敏化太阳能电池用TiO2薄膜电极的改性制备及光电化学性能

以钛酸四异丙酯为钛源, 用水热法合成制备了具有典型锐钛矿晶型的TiO2纳米材料. 采用金属镍掺杂和表面包覆一层氧化钕, 对TiO2薄膜电极进行改性研究. 实验结果表明, 所制备纳米TiO2颗粒较均匀, 粒径约为17~18 nm. 经镍掺杂后, 颗粒团聚粒径明显增大, 但是仍保持均匀状态和多孔结构. 与改性前的TiO2薄膜电极相比, 金属掺杂和表面包覆有助于光生电子和空穴有效地分离, 电池的短路光电流提高了16%, 光电转换效率提高了17%.     

Tandem dynamic kinetic resolution and enzymatic polycondensation to synthesize mPEG‐functionalized poly(amine‐co‐ester)‐type chiral prodrugs

Amphiphilic poly(amine‐co‐ester)s, which contain a single effective enantiomer of an asymmetric drug and thus can avoid potentially serious side effects, are difficult to prepare through nonselective chemical routes not only in the process of introducing chiral drugs to the polymer, but also in the synthesis of the polymer's backbone by metal catalysts. A model of racemic mexiletine, an important antiarrhythmic agent, was used to demonstrate the tandem combination of Candida antarctica lipase B (CAL‐B)‐ and Pd/C‐catalyzed dynamic kinetic resolution (DKR) and subsequent CAL‐B‐catalyzed polycondensation, as an efficient protocol to prepare poly(ethylene glycol)‐functionalized poly(amine‐co‐ester)s containing (R)‐mexiletine with 99% ee value. Chemoenzymatic DKR and enzymatic polymerization conditions were optimized, and the optical purity of incorporated (R)‐mexiletine was confirmed through its hydrolysis from polyester. The copolymers can readily self‐assemble into nanometer‐scale‐sized micelles with well‐dispersed spheres, which have a size distribution that can be efficiently adjusted by changing the polymer concentration. © 2013 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

纳米材料在生物医学领域的应用

目前应用于生物医学中的纳米材料的主要类型有纳米碳材料、纳米高分子材料、纳米复合材料等.纳米材料在生物医学的许多方面都有广泛的应用前景.     

Defect of nanocrystalline copper and silver

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Polyamide‐6/natural clay mineral nanocomposites prepared by solid‐state shear milling using pan‐mill equipment

The polyamide‐6 (PA6)/natural clay mineral nanocomposites were successfully prepared by solid‐state shear milling method without any treatment of clay mineral and additives. PA6/clay mixture was pan‐milled to produce PA6/clay compounding powder, using pan‐mill equipment. The obtained powder as master batch was diluted with neat PA6 to prepare composites by a twin‐screw extruder. The clay silicate layers were found to be partially exfoliated and dispersed homogeneously at nanometer level in PA6 matrix. The rheological measurements and mechanical properties of nanocomposites were characterized. The shear viscosities of nanocomposites were higher than that of pure PA6, and tensile strength and tensile modulus increased, but Izod impact strength decreased, with increasing concentration of clay. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 249–255, 2006     

自上向下的合成策略:最大程度提高贵金属的原子利用率

因为贵金属的价格比较高,并且很多催化反应主要发生在载体和金属接触的周围原子,所以减少贵金属的粒径对于提高金属原子利用率是非常可取的.原子利用率的最高极限就是形成单原子催化活性中心,然而合成稳定的单原子金属催化剂是一个巨大的挑战,因为单原子金属极易聚合成较大的金属颗粒.尽管存在着很大的困难,合成稳定的单原子金属还是可能的.研究表明,单原子金属容易镶嵌在表面能量最高的活性位上,以降低金属和载体的总能量,使之达到最稳定状态.随着金属的负载量增加,以此单原子金属为"晶种"将形成金属纳米粒子.根据这一原理,我们通过简单热扩散方法在HMO表面把Ag纳米粒子"拆分"成单个的Ag原子,并稳定地镶嵌在由HMO四个氧形成的空穴上(HMO的孔道口),使体系的能量降到最低.我们通过原位X射线衍射(XRD)、扩展X射线吸收精细结构光谱(EXAFS)和电子显微镜照片(TEM)详细证明了这种自上而下的合成过程,并通过X射线吸收近边结构光谱(XANES)、氢气程序升温还原(H2-TPR)、CO吸附实验等表征手段和理论计算说明了诱导这一过程的原因.首先我们合成了具有高比表面积的Hollandite型二氧化锰(HMO)纳米颗粒,并且在上面负载纳米银颗粒.TEM数据表明经过焙烧纳米银颗粒消失,形成单原子分散在HMO表面.原位XRD的结果表明随着焙烧温度的升高,银颗粒的衍射峰强度逐渐降低,最后消失,说明纳米银颗粒随着温度的升高逐渐减少,最后达到银高分散的状态.通过对Ag(111)衍射峰强度进行分析,我们发现当温度低于150 oC时,Ag(111)衍射峰强度基本保持不变,说明银颗粒没有变化.当温度高于150 oC时,Ag(111)衍射峰强度开始减小,并且减小的程度随温度的升高而变大.当温度高于260 oC时,Ag(111)衍射峰消失.为了更好的研究这个过程,我们分别在150,200,350 oC焙烧银颗粒的样品,并测试了它们的EXAFS谱.结果表明随着焙烧温度的升高,银和银之间配位数减小,意味着银颗粒的减小.350 oC焙烧样品的EXAFS谱在银原子散射的0.28–0.30 nm范围内没有吸收峰,说明银原子在HMO表面高度分散.然后我们通过XANES谱和理论计算证明了银和载体表面晶格氧的相互作用导致银的前线轨道的电子重新发生排布,从而诱导了整个自上向下的合成过程.最后活性测试表明,单原子银催化剂在甲醛催化氧化中表现出最好的催化活性,并简单研究了单原子催化氧化甲醛的机理.因此这种合成策略有两个重要的作用:(1)增加催化活性位的数量;(2)单原子催化剂的合成有利于催化反应机理的研究,比如甲醛催化氧化.     

Lanthanum strontium manganite/yttria-stabilized zirconia nanocomposites derived from a surfactant assisted,co-assembled mesoporous phase

A one-pot, soft-chemistry, surfactant-assisted co-assembly approach to prepare La(1-x)Sr(x)MnO(3) (LSM)/Y(2)O(3)-stabilized ZrO(2) (YSZ) nanocomposites for use as solid oxide fuel cell (SOFC) cathodes has been investigated. This material with sub-hundred nanometer grain sizes for each phase is the first such nanocomposite where aqueous-based precursors of each component are incorporated in a single synthetic step. This approach utilizes the co-assembly of an anionic yttrium/zirconium acetatoglycolate gel, cetyltrimethylammonium bromide as the cationic surfactant template, and inorganic La, Mn, and Sr salts under alkaline aqueous conditions. The resulting as-synthesized product is an amorphous mesostructured organic/inorganic composite, which is transformed to a mesoporous inorganic oxide with nanocrystalline YSZ walls upon calcination. Calcination to temperatures above 600 degrees C lead to collapse of the mesopores followed by further crystallization of the nanocrystalline YSZ phase and a final crystallization of the LSM perovskite phase above 1000 degrees C. Both the fully crystalline LSM/YSZ and the mesoporous intermediate phase have been investigated for phase homogeneity by TEM energy-dispersive X-ray spectroscopy (EDX) mapping and spot analysis which confirm the dispersion of LSM within a YSZ matrix at the nanometer scale. Impedance spectroscopy analysis of LSM/YSZ nanocomposite electrodes demonstrate a low polarization resistance of around 0.2 omega cm(2) with an activation energy (E(a)) as low as 1.42 eV. Cathodic polarization studies show stable current densities over a 40 h test demonstration.     

聚合物表面的纳米力学研究

综述了近些年才开展的采用原子力显微技术,在聚合物表面进行纳米力学测量的实验方法和基本理论的进展,内容包括分子链的纳米强度测量,纳米力学各向异性的表征,表面分子间的纳米相互作用,表面形貌的纳米测量以及表面微区的纳米粘弹性研究。     

Size-induced diffuse behavior in Pb0.89La0.11Zr0.40Ti0.60O3 nanocrystalline ferroelectric ceramics

The Pb_1−xLa_xZr_yTi_1−yO₃ system is a perovskite ABO₃ structured material which presents ferroelectric properties and has been used as capacitors, actuators, transducers and electro-optic devices. In this paper, we describe the synthesis and the characterization of Pb_0.89La_0.11Zr_0.40Ti_0.60O₃ (PLZT11) nanostructured material. The precursor polymeric method and the spark plasma sintering technique were respectively used to prepare ceramic samples. In order to compare the effect of grain size, microcrystalline PLZT11 ceramic samples were also prepared. PLZT11 samples were characterized by X-ray diffraction technique which results show a reduction on the degree of tetragonality as the average grain size decreases. Moreover, the grain size decrease to a nanometer range induces a diffuse behavior on the dielectric permittivity curves as a function of the temperature and a reduction on the dielectric permittivity magnitude. Furthermore, the large number of grain boundaries due to the nanometer size gives rise to a dielectric anomaly.