有序纳米材料.ppt

1、Ordered nanomaterial Self-assembly,Lidan,Introduction,Self-assembly is a widespread phenomenon in nature. Biological cells, animal bones, shells, pearls, natural mineral zeolite and so on are all nano-structred materials through self-assembly technical.,2,calcareous structure in the body of plankton

2、,Introduction,3,We have used self-assembly to fabricate materials for only 20 years. It is widely believed that self-assembly is a process, in which atoms, molecules, particles, and other units combine together to generate nanomaterials spontaneously driven by lowest energy principle in the suitable

3、 physical and chemical conditions. In this process, the most important driving force is the interaction force among the structural units, like hydrogen bond, Vander Waals force, electrostatic interaction, hydrophilic - hydrophobic interaction and so on.,Contents,self-assembly of Vander Waals force,s

4、elf-assembly of electrostatic attraction,self-assembly of template method,self-assembly of vapor phase catalytic,self-assembly of surface tension and capillary force,self-assembly of microemulsion,self-assembly of oriented attachment,4,5,The structure of surfactant: there is at least one hydrophilic

5、 group in the head, along with one hydrophobic group in the tail. It can be adsorbed on the surface or interface to decrease its surface energy in low concentration.,schematic of surfactant,Self-assembly of microemulsion,Structure of surfactant,6,Surfactant has two states. First is dispersed state,

6、which is also called as ionization state. The second is condensed state, in which micelle will be generated.,The shape of micelle is various due to composition of solution. It may look like spherical, rod-like, hexagonal, cubic, flake, layer and so on. The solution containing ordered micellar struct

7、ure can change into gel after dehydration. Then, ordered mesoporous material will form after drying and calcination if its structure does not collapse.,schematic of micelle,The existing state of surfactant and CMC,7,Microemulsion method is also known as surfactant template method. It mainly utilize

8、this property that surfactant can aggregate in solution to form micelle (or reserve micelle), microemulsion (or reserve microemulsion), liquid crystal and vesica, which have ordered microstructure. Most of these microstructures are often nano-sized. It can not only provide special condition and serv

9、e as micro-reactor, but also be used as template. Now, oxides, halides, chalcogenides, metals, polymers, inorganic salts, and other nanostructured materials have been made through surfactant template method (microemulsion method).,Example 1,8,A stable and highly active ordered mesoporous polymer-bas

10、ed acid catalyst has been prepared via a simple surfactant templating approach and oxidation treatment.,The precursors: low-polymerized phenolic resins and 3-mercaptopropyltrimethoxysilane The coupling agent: TEOS The structure directing agent: triblock copolymer F127,Main idea,Raw material and func

11、tion,9,Results,TEM images,TEM images of mesoporous polymers modified with sulfonic acid groups show oriented and hexagonally arranged pores, further confirming the ordered 2-D hexagonal mesostructure. Ordered mesostructure can be observed in large domains, without distinct defects.,Self-assembly of

12、Vander Waals force,10,Combining two nano-particles with different component and size together can form crystal structure through Vander Waals force. The driving force in the self-assembly process is maximization of the stacking density, which is consistent with the essence of Vander Waals force. Thi

13、s self-assembly method is great important in designing nano-sized material with novel properties.,Example 2,11,SEM image of superlattice structure assembled by binary nanoparticles,self-assembly of electrostatic attraction,12,Professor Wang Zhonglin has made innovative work in the self-assembly fiel

14、d induced by electrostatic attraction.,13,Example 3,Main idea,By controlling growth kinetics, growing nanobelt-based novel structures whose surfaces are dominated by the polarized (0001) facets is successful.,Reasons,Owing to the positive and negative ionic charges on the zinc- and oxygen-terminated

15、 (0001) surfaces, respectively, a spontaneous polarization is induced across the nanobelt thickness. This phenomenon is attributed to a consequence of minimizing the total energy contributed by spontaneous polarization and elasticity.,14,Results,SEM images,SEM images of the as-synthesized ZnO nanobe

16、lts, showing helical nanostructure. The typical width of the nanobelt is 30 nm, and pitch distance is rather uniform. The helixes are right-handed.,15,Example 4,Reasons,Example 4 is an extension of Example 3,Because as-prepared zinc oxide nanorodes grow along the orientation of (001) plane, the latt

17、ice arrangement can cause two sides with reverse charges. (001) plane enriched with zinc atoms has positive charges, while (001) plane enriched with oxide atoms has negative charges. In order to reduce the total energyof this system, zinc oxide will finally be self-assembled into flower-like aggrega

18、tes.,16,Results,Self-assembly of ZnO nanorod into flowerlike structure via electrostatic interactions, as well the flowerlike ZnO nanotubes because of aging.,17,self-assembly of template method,Using monodisperse microspheres to synthesize ordered macroporous materials has drawn grate attention. Sil

19、icate and polystyrene are the common templates. They have a lot of advantages, such as cheap, non-toxic, low decomposition temperature, high surface stability, and so on.,SEM images of PS (a) and SiO2(b) templates,18,Example 5,A nanoporous manganese oxide (MnO2) film was fabricated via a polystyrene

20、 templated electrodeposition in the solution containing MnSO4 .,Main idea,Process,19,Results,It can be clearly seen that the PS particles are assembled as monolayer.,The growth of MnO2 on the ITO electrode surface is directed by the ordered structure of the assembled PS particles.,FESEM image,20,It

21、shows the morphology of MnO2 after removing the PS particles with toluene. Some holes or defects were formed during the removing process of PS particles because PS is an organic substance with excellent toluene solubility.,21,Example 6,A series of hierarchically ordered macro-/mesoporous polymer res

22、ins and macro-/ mesoporous carbon monoliths were synthesized using SiO2 opal as a hard template for the macropore, amphiphilic triblock copolymer PEOPPOPEO as a soft template for the mesopore, and phenolic resin as a precursor for the polymer or carbon.,Main idea,Process,22,Results,The obtained hier

23、archical macro- / mesoporous frameworks had highly periodic arrays of uniform macropores that were surrounded by walls containing the mesoporous structures. HMMC is hierarchical macro-/microporous carbon.,SEM images of (a, b) SiO2 opal template and (c, d) HMMC.,self-assembly of vapor phase catalytic

24、,23,This method can combine one-dimensional homogeneous nanowires or one-dimensional heterogeneous materials with highly matching lattice together. Then, complex three-dimensional nanostructured materials will be formed. It can be divided into two types. One-step method: the precursor (including cat

25、alyst) is introduced into the growth chamber. Complex ordered nanostructure can be fabricated through one growing process. Two-step method: catalyst is sprinkled on the surface of the pre-prepared nanomaterial (nanowire, nanoribbon). Homogeneous or heterogeneous nanostructure can be formed through t

26、wo growth on this basis. Finally, complex three-dimensional ordered nanostructure can be obtained.,24,Example 7,Main idea,It is about the synthesis and characterization of nanowire-nanoribbon junction arrays of ZnO, which were grown by thermal evaporation of the mixture of ZnO and SnO2 powders at 13

27、00 C through a vapor-liquid-solid process.,Reasons,The Sn particles produced by the reduction of SnO2 act as the catalyst; the structure is formed due to a fast growth of ZnO nanowires along 0001 and the subsequent “epitaxial” radial growth of the ZnO nanoribbons along the six 0110 directions around

28、 the nanowire.,25,Results,high magnification SEM images of the ZnO,It is apparent in Figure that the top and bottom strings have a dense and ordered stacking of tadpole-like nanostructures, while the central one is a string assembled with sparsely distributed tadpole-like nano-structures along a thi

29、n nanowire.,self-assembly of surface tension and capillary force,26,This method always utilizes capillary force or surface tension to assemble one-dimensional material spontaneously to fabricate micro-sized and ordered structure on the surface or bulk phase of liquid. This technique simulates the ci

30、rcumstance of transporting timber.,27,Example 8,Main idea,LangmuirBlodgett technique was used to assemble monolayers of aligned silver nanowires. These nanowires possess pentagonal cross-sections and pyramidal tips. They are close-packed and are aligned parallel to each other.,Process,LB nanowire as

31、sembly process,28,Results,SEM image,It shows scanning electron microscopy images of monolayer transferred onto a silicon wafer. The nanowires are aligned side-by-side over large areas, resembling a nematic two-dimensional ordering of a liquid crystal.,29,Example 9,Main idea,It is about the first use

32、 of a long-range force (capillary force) in the self-assembly of three-dimensional (3D) micropatterns on aligned carbon nanotube films through a water-spreading method after the growth of the carbon nanotube.,Reasons,It is considered that low-density regions or vacancies of carbon nanotube films pla

33、y an important role in the formation of the pattern. Therefore different kinds of highly ordered micropatterned structures have been built in a controlled fashion by introducing vacancies artificially.,30,Results,SEM image,SEM observations show that the structures in the grey color region are microp

34、atterns composed of honeycomb-like polygons. An oblique view shows that these honeycomb-like patterns have 3D structures in which the “walls” are vertical to the substrate. Some designs of the etching positions are given in the inserts of Figure cd, in which the blue dots represent vacancies and the

35、 lines represent “walls”.,self-assembly of oriented attachment,31,The concept of oriented attachment was proposed by R.L.Penn on science in 1998. Its definition is that nanocrystals combine together with the same plane to form ordered pattern if other internal driving force is weak. In the self-asse

36、mbly process, nanoparticles always keep in doing Brownian motion. When the same plane begins to be close to each other, more chemical bond can be formed to reduce free energy of this system because of the same atomic arrangement and lattice distance. Oriented attachment has drawn a lot of attention.

37、 More and more novel nanostructure has been synthesized, and more growth mechanism has also been explained reasonably.,32,Example 10,Principle,growth process of CdS nanoparticles-based leaf- and tower-like hierarchical architectures.,33,Results,SEM(a,c), TEM(b,d),It represents the SEM and TEM images

38、 of the products pre-pared by hydrothermal reaction at 180C for 24 h in the absence of surfactant. The products were composed of hierarchical 2D leaf-shaped and 3D flower-like CdS architectures. TEM image further confirmed the bionic behavior of these leaf-shaped flakes.,conference,1 Wei Wang，Xin Zh

39、uang，Qingfei Zhao，Ying WanSelf-assembly synthesis of a high-content sulfonic acid group functionalized ordered mesoporous polymer-based solid as a stable and highly active acid catalystJJournal of Materials Chemistry2012，22：15874-15886 2 Xiang Yang Kong，Zhong Lin WangSpontaneous polarization-inducednanohelixes, nanosprings, and