共查询到20条相似文献，搜索用时 46 毫秒
1.
Nanoscale architecture was used to control energy transfer in semiconducting polymers embedded in the channels of oriented, hexagonal nanoporous silica. Polarized femtosecond spectroscopies show that excitations migrate unidirectionally from aggregated, randomly oriented polymer segments outside the pores to isolated, aligned polymer chains within the pores. Energy migration along the conjugated polymer backbone occurred more slowly than Forster energy transfer between polymer chains. The different intrachain and interchain energy transfer time scales explain the behavior of conjugated polymers in a range of solution environments. The results provide insights for optimizing nanostructured materials for use in optoelectronic devices. 相似文献
2.
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
3.
Jérome D 《Science (New York, N.Y.)》1991,252(5012):1509-1514
The upper temperature for superconductivity in organic conductors has increased from 1 kelvin in 1980, when the phenomenon was discovered in the quasi-one-dimensional cation radical salt tetramethyltetraselenafulvalene phosphorus heptafluoride to 12 kelvin in a new series of organic salts that show nearly two-dimensional electronic properties. These superconductors are attracting interest because of the wide range of new phenomena that they exhibit, including the competition between various ground states, the influence of a magnetic field on a quasi-one-dimensional conductor, the quantization of the Hall effect in a three-dimensional material, the giant magnetoresistance effects related to the two-dimensional nature of the Fermi surface of some materials, and the coherent voltage oscillation of a spin-modulated ground state. Furthermore, there is reason to believe that organic conductors with high superconducting transition temperatures could be produced in the near future. The recent finding of superconductivity in "fullerene" doped with alkali metals supports this optimism. 相似文献
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Hugel T Holland NB Cattani A Moroder L Seitz M Gaub HE 《Science (New York, N.Y.)》2002,296(5570):1103-1106
Light-powered molecular machines are conjectured to be essential constituents of future nanoscale devices. As a model for such systems, we have synthesized a polymer of bistable photosensitive azobenzenes. Individual polymers were investigated by single-molecule force spectroscopy in combination with optical excitation in total internal reflection. We were able to optically lengthen and contract individual polymers by switching the azo groups between their trans and cis configurations. The polymer was found to contract against an external force acting along the polymer backbone, thus delivering mechanical work. As a proof of principle, the polymer was operated in a periodic mode, demonstrating for the first time optomechanical energy conversion in a single-molecule device. 相似文献
6.
We report a method for compensating the birefringence of optical polymers by doping them with inorganic birefringent crystals. In this method, an inorganic birefringent material is chosen that has the opposite birefringence to that of the polymer and has rod-shaped crystals that are oriented when the polymer chains are oriented. The birefringence of the polymer is thus compensated by the opposing birefringence of the crystal. Birefringence is minimized in various polymer optical devices by adjusting process conditions, because it degrades the performance of devices. This method minimizes it, independent of process conditions, which potentially improves the productivity of devices. 相似文献
7.
Gabor NM Song JC Ma Q Nair NL Taychatanapat T Watanabe K Taniguchi T Levitov LS Jarillo-Herrero P 《Science (New York, N.Y.)》2011,334(6056):648-652
We report on the intrinsic optoelectronic response of high-quality dual-gated monolayer and bilayer graphene p-n junction devices. Local laser excitation (of wavelength 850 nanometers) at the p-n interface leads to striking six-fold photovoltage patterns as a function of bottom- and top-gate voltages. These patterns, together with the measured spatial and density dependence of the photoresponse, provide strong evidence that nonlocal hot carrier transport, rather than the photovoltaic effect, dominates the intrinsic photoresponse in graphene. This regime, which features a long-lived and spatially distributed hot carrier population, may offer a path to hot carrier-assisted thermoelectric technologies for efficient solar energy harvesting. 相似文献
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Sazio PJ Amezcua-Correa A Finlayson CE Hayes JR Scheidemantel TJ Baril NF Jackson BR Won DJ Zhang F Margine ER Gopalan V Crespi VH Badding JV 《Science (New York, N.Y.)》2006,311(5767):1583-1586
Deposition of semiconductors and metals from chemical precursors onto planar substrates is a well-developed science and technology for microelectronics. Optical fibers are an established platform for both communications technology and fundamental research in photonics. Here, we describe a hybrid technology that integrates key aspects of both engineering disciplines, demonstrating the fabrication of tubes, solid nanowires, coaxial heterojunctions, and longitudinally patterned structures composed of metals, single-crystal semiconductors, and polycrystalline elemental or compound semiconductors within microstructured silica optical fibers. Because the optical fibers are constructed and the functional materials are chemically deposited in distinct and independent steps, the full design flexibilities of both platforms can now be exploited simultaneously for fiber-integrated optoelectronic materials and devices. 相似文献
10.
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
11.
Integrated optoelectronic devices based on conjugated polymers 总被引：1，自引：0，他引：1
An all-polymer semiconductor integrated device is demonstrated with a high-mobility conjugated polymer field-effect transistor (FET) driving a polymer light-emitting diode (LED) of similar size. The FET uses regioregular poly(hexylthiophene). Its performance approaches that of inorganic amorphous silicon FETs, with field-effect mobilities of 0.05 to 0.1 square centimeters per volt second and ON-OFF current ratios of >10(6). The high mobility is attributed to the formation of extended polaron states as a result of local self-organization, in contrast to the variable-range hopping of self-localized polarons found in more disordered polymers. The FET-LED device represents a step toward all-polymer optoelectronic integrated circuits such as active-matrix polymer LED displays. 相似文献
12.
通过盆栽试验,研究了2种改性剂(有机肥和无机功能材料)对重金属Cd、Pb和Cu污染土壤油菜生长及其吸收重金属的影响。结果表明,2种改性剂均可明显增加油菜产量,但对土壤的改良效果存在差别。有机肥对油菜茎叶吸收Pb具有较好的抑制作用,但却提高了土壤中有效态Cd、Cu含量,使油菜体内Cd、Cu含量增加;施加无机功能材料与有机肥相比,降低了油菜茎叶中Cd、Pb和Cu含量,对油菜吸收Cd、Pb和Cu均起到了较好的抑制作用。 相似文献
13.
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
14.
为了解施用不同种类有机物对污染农田土壤重金属行为的影响,布设了田间小区试验,观察研究施用6种不同类型有机物对土壤水溶性重金属和农作物对重金属吸收等的影响。试验设7个处理,分别为对照（不施有机肥）、施新鲜水稻秸秆、新鲜鸡粪、鸡粪堆肥、新鲜猪粪、猪粪堆肥和商品有机肥,动态检测土壤中水溶性重金属含量、田面水中重金属浓度及收获水稻籽粒中重金属含量的变化。结果表明,与不施有机物的对照处理比较,施用各类有机物在试验前期均可明显提高土壤中水溶性重金属和田面水中重金属的含量,总体上以施用新鲜猪粪的最高,其次为新鲜鸡粪,施用商品有机肥的最低。土壤中水溶性重金属含量随试验时间增长逐渐下降。施用各类有机物对水稻籽粒中重金属的积累影响不明显。土壤中水溶性重金属及田面水中重金属含量均与相应的水溶性碳（DOC）浓度呈显著相关性,表明因有机物施用增加土壤中DOC浓度可能是土壤中水溶性重金属含量增加的主要原因;而不同有机物对土壤重金属活性影响的差异可能与有机物本身的分解程度及可释放DOC大小有关。但施用有机物引起的农田土壤水溶性重金属含量的增加是暂时的,对水稻生长后期籽粒中重金属积累的影响不明显。 相似文献
15.
A device configuration for light emission from electroactive polymers is described. In these light-emitting electrochemical cells, a p-n junction diode is created in situ through simultaneous p-type and n-type electrochemical doping on opposite sides of a thin film of conjugated polymer that contains added electrolyte to provide the necessary counterions for doping. Light-emitting devices based on conjugated polymers have been fabricated that operate by the proposed electrochemical oxidation-reduction mechanism. Blue, green, and orange emission have been obtained with turn-on voltages close to the band gap of the emissive material. 相似文献
16.
MC Lonergan 《Science (New York, N.Y.)》1997,278(5346):2103-2106
Although in principle semiconductor-metal (Schottky) diodes should be tunable by changing the work function of the metal, such flexibility cannot be achieved in a single device and in practice is often limited by interfacial states that cause Fermi-level pinning. A tunable diode is reported based on a hybrid inorganic-organic, n-indium phosphide&cjs3539;poly- (pyrrole)&cjs3539;nonaqueous electrolyte architecture. By electrochemically manipulating the work function of the conjugated polymer poly(pyrrole), the turn-on voltage (more precisely, the forward bias potential required to pass a particular current) of the diode can be continuously and actively tuned by more than 0.6 volt. The work highlights a distinguishing feature of conjugated polymers relative to more traditional semiconductor materials, namely, the ability of dopant ions to permeate conjugated polymers, thereby enabling electrochemical manipulation. 相似文献
17.
Chmiola J Yushin G Gogotsi Y Portet C Simon P Taberna PL 《Science (New York, N.Y.)》2006,313(5794):1760-1763
Carbon supercapacitors, which are energy storage devices that use ion adsorption on the surface of highly porous materials to store charge, have numerous advantages over other power-source technologies, but could realize further gains if their electrodes were properly optimized. Studying the effect of the pore size on capacitance could potentially improve performance by maximizing the electrode surface area accessible to electrolyte ions, but until recently, no studies had addressed the lower size limit of accessible pores. Using carbide-derived carbon, we generated pores with average sizes from 0.6 to 2.25 nanometer and studied double-layer capacitance in an organic electrolyte. The results challenge the long-held axiom that pores smaller than the size of solvated electrolyte ions are incapable of contributing to charge storage. 相似文献
18.
Hayatsu R Winans RE Scott RG McBeth RL Moore LP Studier MH 《Science (New York, N.Y.)》1980,207(4436):1202-1204
Seven phenolic acids and many nonphenolic organic acids, including large amounts of meta-hydroxy (3-hydroxy) benzoic acid and 3-hydroxy-1,5-benzene-dicarboxylic acid, were obtained from the organic polymer of the Murchison C2 chondrite upon oxidation with alkaline cupric oxide. The phenolic acids apparently were derived from phenolic ethers in the polymer, which in turn probably were formed from carbon monoxide and hydrogen by catalytic Fischer-Tropsch type reactions in the solar nebula. In contrast, terrestrial polymers such as lignin, humic acid, and coal yield mainly para-hydroxy (4-hydroxy) benzene derivatives by the same oxidation procedure. 相似文献
19.
As a novel approach for turning the peculiar features of quantum mechanics into practical devices, researchers are investigating the use of ultracold atomic clouds above microchips. Such "atom chips" may find use as sensitive probes for gravity, acceleration, rotation, and tiny magnetic forces. In their Perspective, Fortagh and Zimmermann discuss recent advances toward creating atom chips, in which current-carrying conductors in the chips create magnetic microtraps that confine the atomic clouds. Despite some intrinsic limits to the performance of atom chips, existing technologies are capable of producing atom chips, and many possibilities for their construction remain to be explored. 相似文献
20.
Several spectroscopic methods were applied to study the characteristic properties of the electronic excitations in thin films of regioregular and regiorandom polythiophene polymers. In the regioregular polymers, which form two-dimensional lamellar structures, increased interchain coupling strongly influences the traditional one-dimensional electronic properties of the polymer chains. The photogenerated charge excitations (polarons) show two-dimensional delocalization that results in a relatively small polaronic energy, multiple absorption bands in the gap where the lowest energy band becomes dominant, and associated infrared active vibrations with reverse absorption bands caused by electron-vibration interferences. The relatively weak absorption bands of the delocalized polaron in the visible and near-infrared spectral ranges may help to achieve laser action in nanocrystalline polymer devices using current injection. 相似文献