다중혈관 관상동맥 환자에서 y-문합을 이용하여 양쪽 내흉동맥만을 사용한 우회술의 조기 성적

Fundamentals of Plasmonics.- Electromagnetics of Metals.- Surface Plasmon Polaritons at Metal / Insulator Interfaces.- Excitation of Surface Plasmon Polaritons at Planar Interfaces.- Imaging Surface Plasmon Polariton Propagation.- Localized Surface Plasmons.- Electromagnetic Surface Modes at Low Frequencies.- Applications.- Plasmon Waveguides.- Transmission of Radiation Through Apertures and Films.- Enhancement of Emissive Processes and Nonlinearities.- Spectroscopy and Sensing.- Metamaterials and Imaging with Surface Plasmon Polaritons.- Concluding Remarks.

/pdf/plasmonics-fundamentals-and-applications-4syb9877sr.pdf

Plasmonics: Fundamentals and Applications

TiO(2) is one of the most studied compounds in materials science. Owing to some outstanding properties it is used for instance in photocatalysis, dye-sensitized solar cells, and biomedical devices. In 1999, first reports showed the feasibility to grow highly ordered arrays of TiO(2) nanotubes by a simple but optimized electrochemical anodization of a titanium metal sheet. This finding stimulated intense research activities that focused on growth, modification, properties, and applications of these one-dimensional nanostructures. This review attempts to cover all these aspects, including underlying principles and key functional features of TiO(2), in a comprehensive way and also indicates potential future directions of the field.

TiO2 nanotubes: synthesis and applications.

The term photonic crystals appears because of the analogy between electron waves in crystals and the light waves in artificial periodic dielectric structures. During the recent years the investigation of one-, two-and three-dimensional periodic structures has attracted a widespread attention of the world optics community because of great potentiality of such structures in advanced applied optical fields. The interest in periodic structures has been stimulated by the fast development of semiconductor technology that now allows the fabrication of artificial structures, whose period is comparable with the wavelength of light in the visible and infrared ranges.

http://ieeexplore.ieee.org/iel5/6354/16969/00781867.pdf

Photonic crystals

Molecular self-assembly is the spontaneous association of molecules under equilibrium conditions into stable, structurally well-defined aggregates joined by noncovalent bonds. Molecular self-assembly is ubiquitous in biological systems and underlies the formation of a wide variety of complex biological structures. Understanding self-assembly and the associated noncovalent interactions that connect complementary interacting molecular surfaces in biological aggregates is a central concern in structural biochemistry. Self-assembly is also emerging as a new strategy in chemical synthesis, with the potential of generating nonbiological structures with dimensions of 1 to 10(2) nanometers (with molecular weights of 10(4) to 10(10) daltons). Structures in the upper part of this range of sizes are presently inaccessible through chemical synthesis, and the ability to prepare them would open a route to structures comparable in size (and perhaps complementary in function) to those that can be prepared by microlithography and other techniques of microfabrication.

Molecular self-assembly and nanochemistry: A chemical strategy for the synthesis of nanostructures

Transmission electron microscopy analysis of self-ordered porous alumina obtained by electrochemical anodization shows that self-ordering requires a porosity of 10%, independent of the specific anodization conditions. This corresponds to a volume expansion of alumina to aluminum of about 1.2. We propose that self-ordering of porous alumina with any interpore distance is possible if the applied potential, which mainly determines the interpore distance, and the pH value of the electrolyte, which mainly defines the pore radius, match the 10% porosity rule.

Self-ordering Regimes of Porous Alumina: The 10% Porosity Rule

We have developed a simple technique for the fabrication of polymer nanotubes with a monodisperse size distribution and uniform orientation. When either a polymer melt or solution is placed on a substrate with high surface energy, it will spread to form a thin film, known as a precursor film, similar to the behavior of low molar mass liquids ([1][1], [2][2]).

Similar wetting phenomena occur if porous templates are brought into contact with polymer solutions or melts: A thin surface film will cover the pore walls in the initial stages of wetting. This is because the cohesive driving forces for complete filling are much weaker than the adhesive forces. Wall wetting and complete filling of the pores thus take place on different time scales. The latter is prevented by thermal quenching in the case of melts or by solvent evaporation in the case of solutions, thus preserving a nanotube structure. If the template is of monodisperse size distribution, aligned or ordered, so are the nanotubes, and ordered polymer nanotube arrays can be obtained if the template is removed. Any melt-processible polymer, such as polytetrafluoroethylene (PTFE), blends, or multicomponent solutions can be formed into nanotubes with a wall thickness of a few tens of nanometers. Owing to its versatility, this approach should be a promising route toward functionalized polymer nanotubes.

We used ordered porous alumina and oxidized macroporous silicon templates with narrow pore size distribution ([3][3]). Extended regular pore arrays were prepared by lithography. The pores are well-defined, straight, with a smooth inner surface and with diameters DP between 300 and 900 nm. To process melts, we placed the polymer on a pore array at a temperature well above its glass transition temperature, in the case of amorphous polymers, or its melting point, in the case of partially crystalline polymers. The liquid polymer forms a thin wetting film covering the entire pore surface on a time scale ranging from a few minutes to half an hour. Polymer solutions were dropped on the templates at ambient conditions (fig. S1A) ([4][4]). The resulting nanotubes obtained from either method had wall thicknesses between 20 and 50 nm and lengths of up to 100 μm. Oligomers as well as polymers with molecular masses Mn up to several hundreds of thousands of grams per mol were processed. [Figure 1][5]depicts nanotubes formed from several polymers by melt-wetting. The tip of a polystyrene (PS) nanotube ( Mn ∼ 850,000 g/mol) formed in an alumina template was uncovered by etching the alumina substrate with aqueous potassium hydroxide ([Fig. 1][5]A) ([4][4]). [Figure 1][5]B shows the same sample after the complete removal of the template. [Figure 1][5]C depicts an array of aligned PTFE nanotubes obtained by wetting an alumina template and [Fig. 1][5]D a highly ordered array of polymethyl methacrylate (PMMA; Mn ∼ 80,000 g/mol) nanotubes prepared by wetting a macroporous silicon template. After selectively dissolving the template, the remaining nanotube array still exhibits its hexagonal long-range order.

![Figure 1][6] 

Figure 1 
Scanning electron micrographs of nanotubes obtained by melt-wetting. ( A ) Damaged tip of a PS nanotube ( Mn ∼ 850,000 g/mol) protruding from a porous alumina membrane. The substrate, on which the pore array was located, has been removed to uncover the tube tips. ( B ) Ordered array of tubes from the same PS sample after complete removal of the template. ( C ) Array of aligned PTFE tubes. ( D ) PMMA tubes with long-range hexagonal order obtained by wetting of a macroporous silicon pore array after complete removal of the template.



The wetting technique can be easily extended to prepare functionalized nanotubes, for example, palladium/polymer composite nanotubes. We first wetted the porous templates with a solution containing poly-l-lactide (PLLA) and palladium(II)acetate under ambient conditions. After evaporation of the solvent dichloromethane, a PLLA/palladium(II)acetate film covered the pore walls. The template was subsequently annealed in vacuum at temperatures of up to 300°C to degrade PLLA ([5][7]) and to reduce Pd. In a second wetting step, molten PS was added, so that Pd/PS composite tubes were formed (fig. S1B). Energy-dispersive x-ray microanalysis verified the presence of Pd (fig. S1C), and selected area electron diffraction of single composite tubes revealed that it was metallic with a typical crystallite size of 2 to 3 nm (fig. S1D). As demonstrated by this example, template-wetting should have an outstanding potential in providing customized nanotubes for a broad range of applications in nanoscience.

1. [↵][8]1. P. G. de Gennes
 , Rev. Mod. Phys. 57, 827 (1985).
 [OpenUrl][9][CrossRef][10][Web of Science][11]

2. [↵][12]S. F. Kistler, in Wettability , Surfactant Science Series , vol. 49, J. C. Berg, Ed. (Dekker, New York, 1993), chap. 6.
 

3. [↵][13]1. R. B. Wehrspohn, 2. J. Schilling
 , MRS Bull. 8, 623 (2001).
 [OpenUrl][14]

4. [↵][15]Materials and methods are available as supporting mate rial on Science Online.
 

5. [↵][16]1. M. Bognitzki 2. et al.
 , Adv. Mater. 12, 637 (2000).
 [OpenUrl][17]

6. Support from the Deutsche Forschungsgemeinschaft (WE 2637/1-1 and WE 496/19-1) and transmission electron microscopy investigations by C. Dietzsch are gratefully acknowledged. Supporting Online Material [www.sciencemag.org/cgi/content/full/296/5575/1997/DC1][18] Materials and Methods Fig. S1

 [1]: #ref-1
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 [6]: pending:yes
 [7]: #ref-5
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 [9]: {openurl}?query=rft.jtitle%253DReviews%2Bof%2BModern%2BPhysics%26rft.stitle%253DRev.%2BMod.%2BPhys.%26rft.issn%253D1539-0756%26rft.volume%253D57%26rft.spage%253D827%26rft_id%253Dinfo%253Adoi%252F10.1103%252FRevModPhys.57.827%26rft.genre%253Darticle%26rft_val_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Ajournal%26ctx_ver%253DZ39.88-2004%26url_ver%253DZ39.88-2004%26url_ctx_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Actx
 [10]: /lookup/external-ref?access_num=10.1103/RevModPhys.57.827&link_type=DOI
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 [12]: #xref-ref-2-1 "View reference 2 in text"
 [13]: #xref-ref-3-1 "View reference 3 in text"
 [14]: {openurl}?query=rft.jtitle%253DMRS%2BBull.%26rft.volume%253D8%26rft.spage%253D623%26rft.genre%253Darticle%26rft_val_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Ajournal%26ctx_ver%253DZ39.88-2004%26url_ver%253DZ39.88-2004%26url_ctx_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Actx
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 [17]: {openurl}?query=rft.jtitle%253DAdv.%2BMater.%26rft.volume%253D12%26rft.spage%253D637%26rft.atitle%253DADV%2BMATER%26rft.genre%253Darticle%26rft_val_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Ajournal%26ctx_ver%253DZ39.88-2004%26url_ver%253DZ39.88-2004%26url_ctx_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Actx
 [18]: http://www.sciencemag.org/cgi/content/full/296/5575/1997/DC1

/pdf/polymer-nanotubes-by-wetting-of-ordered-porous-templates-2py17nlryz.pdf

Polymer nanotubes by wetting of ordered porous templates.

Hysteresis loops of two-dimensional arrays of magnetic nanowires have been micromagnetically modelled. The calculations focus on magnetostatic interactions in addition to Zeeman and magnetic anisotropy energy terms. Starting from an ideally ordered hexagonal array, the generation of local disorder is first modelled and subsequently, hysteresis loops are calculated by Monte Carlo and iterative methods considering dipolar and higher-order multipole effects. The main conclusions of the modelling are: (i) distortion of the hexagonal ordering results in an increasing effective field to reach magnetic saturation while roughly maintaining coercivity, and (ii) an increase of the average distributed coercivity of individual nanowires gives rise to enhanced coercivity and anisotropy field. The results of these simulations are analysed in view of experimental loops of arrays of Ni nanowires filling nanoporous alumina membranes with different degrees of 2D-polycrystalline arrangement. After a careful analysis by image processing, it is concluded that fluctuations in the diameter and cross-section of individual nanowires play an important role in a deep correlation between modelled and experimental hysteresis loops.

Modelling hysteresis of interacting nanowires arrays

Bifunctional Heterostructure Assembly of NiFe LDH Nanosheets on NiCoP Nanowires for Highly Efficient and Stable Overall Water Splitting

The magnetic behavior of 100 nm period arrays of Ni nanowires embedded in a highly ordered alumina pore matrix were characterized by magnetometry and magnetic force microscopy. Reducing the diameter of the nanowires from 55 to 30 nm while keeping the interwire distance constant leads to increasing coercive fields from 600 to 1200 Oe and to increasing remanence from 30% to 100%. The domain structure of the arrays exhibits in the demagnetized state a labyrith-like pattern. These results show that stray field interactions of single domain nanowires are entirely dependent on the nanowire diameter.

/pdf/hexagonally-ordered-100-nm-period-nickel-nanowire-arrays-54tsanlm35.pdf

Ralf B. Wehrspohn

Papers

Self-ordering Regimes of Porous Alumina: The 10% Porosity Rule

Polymer nanotubes by wetting of ordered porous templates.

Modelling hysteresis of interacting nanowires arrays

Bifunctional Heterostructure Assembly of NiFe LDH Nanosheets on NiCoP Nanowires for Highly Efficient and Stable Overall Water Splitting

Hexagonally ordered 100 nm period nickel nanowire arrays