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1.
Mussel-inspired surface chemistry for multifunctional coatings 总被引：2，自引：0，他引：2
We report a method to form multifunctional polymer coatings through simple dip-coating of objects in an aqueous solution of dopamine. Inspired by the composition of adhesive proteins in mussels, we used dopamine self-polymerization to form thin, surface-adherent polydopamine films onto a wide range of inorganic and organic materials, including noble metals, oxides, polymers, semiconductors, and ceramics. Secondary reactions can be used to create a variety of ad-layers, including self-assembled monolayers through deposition of long-chain molecular building blocks, metal films by electroless metallization, and bioinert and bioactive surfaces via grafting of macromolecules. 相似文献
2.
Thin gold films placed in contact on compliant elastomeric poly(dimethylsiloxane) supports weld together. This ;;cold welding' is remarkable both for the low loads required and for the fact that it occurs under ambient laboratory conditions, conditions in which the gold surfaces are covered with films of weakly adsorbed organic impurities. These impurities are probably displaced laterally during the welding. Welding can be prevented by the presence of a self-assembled gold(I) alkylthiolate monolayer on the gold surfaces. The welded contacts have low electrical resistivity and can be made thin enough to transmit light. This system is a promising one with which to study interaction between interfaces. 相似文献
3.
A periodic mesoporous organosilica composed of interconnected three-ring [Si(CH2)]3 units built of three SiO2(CH2)2 tetrahedral subunits is reported. It represents the archetype of a previously unknown class of nanocomposite materials in which two bridging organic groups are bound to each silicon atom. It can be obtained with powder and oriented film morphologies. The nanocomposite is self-assembled from the cyclic three-ring silsesquioxane [(EtO)2Si(CH2)]3 precursor and a surfactant mesophase to give a well-ordered mesoporous framework. Low dielectric constants and good mechanical stability of the films were measured, making this material interesting for microelectronic applications. Methylene group reactivity of the three-ring precursor provides entry to a family of nanocomposites, exemplified by the synthesis and self-assembly of [(EtO)2Si(CHR)][(EtO)2Si(CH2)]2 (where R indicates iodine, bromine, or an ethyl group). 相似文献
4.
采用室内增溶性实验及吸附实验,研究了表面活性剂十六烷基三甲基溴化胺(CTMAB)对甲基对硫磷的增溶作用,并进一步研究了甲基对硫磷在硼润土-十六烷基三甲基溴化胺体系中的分配特性。结果表明,CTMAB对膨润土吸附甲基对硫磷有明显的增溶作用,且当CTMAB其浓度大于CMC时,增溶效果显著;在低浓度表面活性剂条件下,膨润土对甲基对硫磷的吸附量随着CTMAB浓度的增加而增加,吸附在膨润土表面的CTMAB并不是作为一个分配体而存在,而是作为一个有效的吸附薄膜;在高浓度表面活性剂条件下,膨润土对甲基对硫磷的吸附量随着表面活性剂浓度的增加而降低。 相似文献
5.
BS Gallardo VK Gupta FD Eagerton LI Jong VS Craig RR Shah NL Abbott 《Science (New York, N.Y.)》1999,283(5398):57-60
Electrochemical methods were combined with redox-active surfactants to actively control the motions and positions of aqueous and organic liquids on millimeter and smaller scales. Surfactant species generated at one electrode and consumed at another were used to manipulate the magnitude and direction of spatial gradients in surface tension and guide droplets of organic liquids through simple fluidic networks. Solid microparticles could be transported across unconfined surfaces. Electrochemical control of the position of surface-active species within aqueous films of liquid supported on homogeneous surfaces was used to direct these films into periodic arrays of droplets with deterministic shapes and sizes. 相似文献
6.
The relative importance of x-rays alone and of x-ray-generated primary and secondary electrons in damaging organic materials was explored by use of self-assembled monolayers (SAMs) on multilayer thin-film supports. The substrates were prepared by the deposit of thin films of silicon (0, 50, 100, and 200 angstroms) on thick layers of gold (2000 angstroms). These systems were supported on chromium-primed silicon wafers. Trifluoroacetoxy-terminated SAMs were assembled on these substrates, and the samples were irradiated with common fluxes of monochromatic aluminum K(alpha) x-rays. The fluxes and energy distributions of the electrons generated by interactions of the x-rays with the various substrates, however, differed. The substrates that emitted a lower flux of electrons exhibited a slower loss of fluorine from the SAMs. This observation indicated that the electrons-and not the x-rays themselves-were largely responsible for the damage to the organic monolayer. 相似文献
7.
Kim M Hohman JN Cao Y Houk KN Ma H Jen AK Weiss PS 《Science (New York, N.Y.)》2011,331(6022):1312-1315
The products of photoreactions of conjugated organic molecules may be allowed by selection rules but not observed in solution reactions because of unfavorable reaction geometries. We have used defect sites in self-assembled alkanethiolate monolayers on gold surfaces to direct geometrically unfavorable photochemical reactions between individual organic molecules. High conductivity and stochastic switching of anthracene-terminated phenylethynylthiolates within alkanethiolate monolayers, as well as in situ photochemical transformations, have been observed and distinguished with the scanning tunneling microscope (STM). Ultraviolet light absorbed during imaging increases the apparent heights of excited molecules in STM images, a direct manifestation of probing electronically excited states. 相似文献
8.
Heterogeneous, patterned surfaces comprising well-defined hydrophobic and hydrophilic regions and having micrometer-scale periodicities were prepared by patterning the adsorption of omega-functionalized alkanethiolates in self-assembled monolayers (SAMs) on gold. Condensation of water on such surfaces resulted in drops that followed the patterns in the SAMs. These patterned condensation figures (CFs) acted as optical diffraction gratings for reflected (or transmitted) light from a helium-neon laser (wavelength of 632.8 nanometers). Under an atmosphere of constant relative humidity, the development of the condensation figure was monitored quantitatively, as the temperature of the surface was lowered, by following the change in intensity of a first-order diffraction spot. This experimental technique may be useful in the development of new types of optical sensors that respond to their environment by changing the reflectivity of patterned regions and for studying phenomena such as drop nucleation, contact angle hysteresis, and spontaneous dewetting and break-up of thin liquid films. 相似文献
9.
The surface microstructure of c-axis (Ca,Sr)CuO(2) thin films, grown by laser molecular beam epitaxy on SrTiO(3)(001) substrates, was studied by ultrahigh-vacuum scanning tunneling microscopy (STM). Images were obtained for codeposited Ca1-xSrxCuO(2) thin films, which show a layered-type growth mode. The surfaces consist of atomically flat terraces separated by steps that are one unit cell high. A pronounced dependence of the growth mechanism on the Sr/Ca ratio of the films was observed. Atomic resolution STM images of the CuO(2) sheets in the ab plane show a square lattice with an in-plane spacing of 4 angstroms; the lattice contains different concentrations of point defects, depending on the polarity of the sample-tip bias. 相似文献
10.
Colson JW Woll AR Mukherjee A Levendorf MP Spitler EL Shields VB Spencer MG Park J Dichtel WR 《Science (New York, N.Y.)》2011,332(6026):228-231
Covalent organic frameworks (COFs), in which molecular building blocks form robust microporous networks, are usually synthesized as insoluble and unprocessable powders. We have grown two-dimensional (2D) COF films on single-layer graphene (SLG) under operationally simple solvothermal conditions. The layered films stack normal to the SLG surface and show improved crystallinity compared with COF powders. We used SLG surfaces supported on copper, silicon carbide, and transparent fused silica (SiO(2)) substrates, enabling optical spectroscopy of COFs in transmission mode. Three chemically distinct COF films grown on SLG exhibit similar vertical alignment and long-range order, and two of these are of interest for organic electronic devices for which thin-film formation is a prerequisite for characterizing their optoelectronic properties. 相似文献
11.
研究电致发光有机薄膜中载流子的输运过程，迁移率是描述输运过程的关键物理量。根据载流子在格点间跳跃（hopping)输运理论，提出了一个有机薄膜中载流子输运的理论模型，推导出了迁移率的理论公式，以聚对苯乙炔（poly(p-phenylene vinylene)为例，数值计算了其在不同温度和电场下的迁移率，与实验符合得很好。 相似文献
12.
The frequency-dependent shear response of an ultrathin polymer melt (polyphenylmethylsiloxane) confined between adsorbing surfaces (parallel plates of mica) is described. The sinusoidal deformations were sufficiently small to give linear response, implying that measurement did not perturb the film structure. A remarkable transition was observed with decreasing thickness. When the film thickness was less than five to six times the unperturbed radius of gyration, there emerged a strong rubber-like elasticity that was not characteristic of the bulk samples. This result indicates enhanced entanglement interactions in thin polymer films and offers a mechanism to explain the slow mobility of polymers at surfaces. 相似文献
13.
The interaction in water of neutral hydrocarbon and fluorocarbon surfaces, prepared by Langmuir-Blodgett deposition of surfactant monolayers, has been investigated. The attraction between these hydrophobic surfaces can be measured at separations of 70 to 90 nanometers and thus is of considerably greater range than previously found. Spontaneous cavitation occurred as soon as the fluorocarbon surfaces were brought into contact but occurred between the hydrocarbon surfaces only after separation from contact. The very long range forces measured are a consequence of the metastability of water films between macroscopic hydrophobic surfaces. Thus the hydrophobic interaction between macroscopic surfaces may not be related to water structure in the same way that the hydrophobic effect between nonpolar molecules is related to water structure. 相似文献
14.
Nanometer-thick films at interfaces and surfaces exist in various materials and can substantially influence their properties. Whether these films are an equilibrium or transient state is debated. To address this question, we equilibrated 1.2-nanometer-thick films at gold-sapphire interfaces in the presence of anorthite glass and measured the solid-solid interface energy. The equilibrated film significantly reduced the interfacial energy and could be described by the Gibbs adsorption isotherm expanded to include structure in addition to chemical excess. Unlike artificially made conventional thin films, these films do not break up during equilibration and offer an alternative design criterion for thin-film technology. These results demonstrate that nanometer-thick films at interfaces and surfaces can be an equilibrium state and included in phase diagrams with dedicated tie-lines. 相似文献
15.
Bunker BC Rieke PC Tarasevich BJ Campbell AA Fryxell GE Graff GL Song L Liu J Virden JW McVay GL 《Science (New York, N.Y.)》1994,264(5155):48-55
Processing routes have been developed for the production of thin ceramic films through precipitation from aqueous solutions. The techniques are based on crystal nucleation and growth onto functionalized interfaces. Surface functionalization routes have been developed by the mimicking of schemes used by organisms to produce complex ceramic composites such as teeth, bones, and shells. High-quality, dense polycrystalline films of oxides, hydroxides, and sulfides have now been prepared from "biomimetic" synthesis techniques. Ceramic films can be synthesized on plastics and other materials at temperatures below 100 degrees C. As a low-temperature process in which water rather than organic solvents is used, this synthesis is environmentally benign. Nanocrystalline ceramics can be produced, sometimes with preferred crystallite orientation. The direct deposition of high-resolution patterned films has also been demonstrated. The process is well suited to the production of organic-inorganic composites. 相似文献
16.
The converse piezoelectric effect, in which an electric field applied across a piezoelectric material induces a stress in that material, has spurred many recent developments in mass measurement techniques. These methods commonly rely on the changes in the vibrational resonant frequency of piezoelectric quartz oscillators that result from changes in mass on the surface of the oscillator. The dependence of frequency on mass has been exploited extensively for mass measurements in vacuum or gas phase, for example, thickness monitors for thin-film preparation and sensors for chemical agents. Advances in piezoelectric methodology in the last decade now allow dynamic measurements of minute mass changes (< 10(-9) grams per square centimeter) at surfaces, thin films, and electrode interfaces in liquid media as well. Mass measurements associated with a diverse collection of interfacial processes can be readily performed, including chemical and biological sensors, reactions catalyzed by enzymes immobilized on surfaces, electron transfer at and ion exchange in thin polymer films, and doping reactions of conducting polymers. 相似文献
17.
Sailor MJ Ginsburg EJ Gorman CB Kumar A Grubbs RH Lewis NS 《Science (New York, N.Y.)》1990,249(4973):1146-1149
The optical and electronic properties of thin films of the solution-processible polymer poly-(CH(3))(3)Si-cyclooctatetraene are presented. This conjugated polymer is based on a polyacetylene backbone with (CH(3))(3)Si side groups. Thin transparent films have been cast onto n-doped silicon (n-Si) substrates and doped with iodine to form surfacebarrier solar cells. The devices produce photovoltages that are at the theoretical limit and that are much greater than can be obtained from n-Si contacts with conventional metals. Two methods for forming layered polymeric materials, one involving the spincoating of preformed polymers and the other comprising the sequential polymerization of different monomers, are also described. An organic polymer analog of a metal/insulator/metal capacitor has been constructed with the latter method. 相似文献
18.
We analyzed the transport of ballistic electrons through organic molecules on uniformly flat surfaces of bismuth grown on silicon. For the fullerene C60 and for a planar organic molecule (3,4,9,10-perylene-tetracarboxylic acid dianhydride), the signals revealed characteristic submolecular patterns that indicated where ballistic transport was enhanced or attenuated. The transport was associated to specific electronic molecular states. At electron energies of a few electron volts, this "scanning near-field electron transmission microscopy" method could be applied to various adsorbates or thin layers. 相似文献
19.
Epitaxial BiFeO3 multiferroic thin film heterostructures 总被引：2，自引：0，他引：2
Wang J Neaton JB Zheng H Nagarajan V Ogale SB Liu B Viehland D Vaithyanathan V Schlom DG Waghmare UV Spaldin NA Rabe KM Wuttig M Ramesh R 《Science (New York, N.Y.)》2003,299(5613):1719-1722
Enhancement of polarization and related properties in heteroepitaxially constrained thin films of the ferroelectromagnet, BiFeO3, is reported. Structure analysis indicates that the crystal structure of film is monoclinic in contrast to bulk, which is rhombohedral. The films display a room-temperature spontaneous polarization (50 to 60 microcoulombs per square centimeter) almost an order of magnitude higher than that of the bulk (6.1 microcoulombs per square centimeter). The observed enhancement is corroborated by first-principles calculations and found to originate from a high sensitivity of the polarization to small changes in lattice parameters. The films also exhibit enhanced thickness-dependent magnetism compared with the bulk. These enhanced and combined functional responses in thin film form present an opportunity to create and implement thin film devices that actively couple the magnetic and ferroelectric order parameters. 相似文献
20.
An experimental technique is described for simultaneously measuring the static and dynamic interactions of very thin liquid films between two surfaces as they are moved normally or laterally relative to each other. Film thickness can be measured and controlled to 1 angstrom. Initial results are presented of the transition in the physical properties of liquid films only one molecular layer thick to thicker films whose properties are practically indistinguishable from the bulk. In particular, the results show that two molecularly smooth surfaces, when close together in simple liquids, slide (shear) past each other while separated by a discrete number of molecular layers, and that the frictional force is "quantized" with the number of layers. 相似文献