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    In this study, the origin of the green fluorescence is investigated by photoelectron spectroscopy PES. As a prerequisite, it is necessary to prepare structurally similar organic crystals on a conductive surface, which leads to the choice of highly oriented pyrolytic graphite HOPG as a substrate.

    PES measurements show that the interface between p-6P and 6T crystals is sharp on a molecular level without any sign of interface dipole formation or chemical interaction between the molecules. We therefore conclude that the different emission colors of the two 6T phases are caused by different types of molecular aggregation.

    Emission the last few years, the self-assembly of ordered structures on the nanoscale has been recognized as a key issue in nanotechnology, opening novel perspectives for device applications. In addition to applications of inorganic nanostructures in nanomedicine 1112 and nanoelectronics, 1314 it was found that organic self-assembled nanostructures offer novel perspectives for device applications including optical sensors, waveguides, and laser sources.

    Therefore, the preparation of parallel self-assembled nanofibers with significantly different optical properties i. Sketch of self-assembled nanofibers prepared by vacuum deposition on muscovite mica. Heteroepitaxy of organic molecules can provide a solution to this problem because it influences the nucleation and sexihhiophene of organic adsorbate layers by the exploitation of templating effects.

    The LMAs of 6T and p-6P molecules align parallel, and an adaptation of the specific herringbone packing of the two molecular species is observed. Remarkably, the photoluminescence spectrum of such heterostructures comprises not only blue p-6P and red 6T emission but also an additional contribution in the green spectral regime, which is related to the interface layer.

    In addition, chemical interactions between molecules can be studied with high precision, which allows us to answers the following questions: 1 Does intermixing of the two molecular species occur, leading to 6T molecules embedded in a p-6P matrix, which provides a significantly different environment compared to that of bulk, crystalline 6T?

    For PES measurements, electrically conductive substrates are indispensable to avoiding charging issues, which render the insulator muscovite mica an inappropriate substrate. However, to ensure the comparability of the results, an alternative substrate should allow p-6P sexithuophene 6T crystallites to grow nanoneedles with the same contact planes as on muscovite mica i. Consequently, HOPG represents an ideal model system to replace muscovite mica in order to study the organic—organic interface properties by PES.

    Both crystal configurations are characteristic of flat-lying 6T molecules on the substrate surface, which agrees well with earlier reports from high-resolution electron energy loss spectroscopy. To verify the orientation of 6T, gracing-incidence reciprocal space maps RSM were recorded, which fully confirms our assignment Supporting Information. Both p-6P and 6T form multiple crystal orientations on HOPG, which all are indicative of flat-lying molecules with sexihiophene to the substrate surface.

    The molecular orientations of both the pure compounds emissjon the heterostructures on HOPG are fully in line with what is observed for sexithiophene. Fluorescence microscopy represents an excellent method for combining morphological and optical investigations.

    By using an ultraviolet UV light source, the organic thin films are excited such that we can study their spatially resolved fluorescence. The photoluminescence PL spectra are consistent with literature data obtained for p-6P nanofibers on mica substrates.

    Consequently, p-6P nanofibers can be expected to show random azimuthal orientations on a macroscopic length scale, leading to the formation of a netlike sample morphology. Sketch of the investigated sample structures. Subsequently, nominally one monolayer of 6T was deposited emission top of the p-6P template ii. Finally, a nm-thick 6T layer was grown on the p-6P template iiiand all samples were characterized by fluorescence microscopy and photoluminescence PL. A PL spectrum of pure 6T bulk crystallites is plotted smission a reference.

    To resolve the relatively weakly emitting 6T crystallites, the red detection channel was amplified in the sexithiolhene panel of the color image acquired on sample ekission. In step ii, nominally 0.

    Beside the blue p-6P emission, a second band arises in the green spectral range. Note that comparable spectra were reported for such heterostructures grown on mica, where the presence of a 6T layer sensitized by the excited p-6P material via resonance-energy transfer was suggested. In particular, the change in the intensity ratio of the 0—0 and 0—1 vibronic peaks occurring at approximately and nm, respectively was also observed in nanofibers fabricated on mica with comparable 6T thicknesses and was explained by a superposition of crystalline and interfacial 6T emissions.

    It has to be stated that the red-orange emitting crystallites can be detected only if the red channel of the image is amplified. At first glance, the netlike fiber morphology is sexithiophene from fluorescence emission. Flat regions are observed between the fibers, which can be attributed to the bare HOPG substrate labeled A.

    In addition, sexithiophebe different needlelike morphologies are observed. On top of the p-6P crystallites, —nm-high entities are present Cwhich exhibit a triangular cross section. Note that previous TEM investigations revealed that such SFM cross sections reproduce only one facet correctly because of the finite cone angle of the sexithiophene.

    The cross section depicted below is taken from the region marked by a dashed polygon, and the corresponding height profile is presented in panel b. Phase images provide information on local variations in the mechanical properties due to material-dependent dissipative processes related to the tip—sample interaction.

    The measurements were carried out in the form of a thickness series, starting with a 5 -nm-thick p-6P layer and 6T layers deposited subsequently onto this template. In the VB region, a peak around 3. Upon p-6P deposition, two distinct peaks arise at 2. Upon 6T emission, a new peak emerges at 1.

    With increasing 6T thickness, the peak at 1. This points toward a sharp interface between p-6P and 6T because UPS is a highly surface-sensitive technique with an escape depth for electrons on the order of 1 nm at the given photon energy. Clearly, 6T grows on p-6P and completely covers the template layer.

    Layers sdxithiophene increasing 6T thickness are deposited onto the p-6P buffer layer with nominal thicknesses of 0. The SECO emidsion that all interfaces are vacuum-level aligned because in the cutoff region sexithiophene no shifts are emission. The observation of vacuum-level alignment and the absence sdxithiophene new electronic states, resulting from strong electronic coupling between the individual materials, clearly rules out that the observed green emission of a 6T ML on top of p-6P template crystals originates from interfacial electronic states.

    Both homogeneous green-emitting interfacial 6T phase for low 6T coverages and red-emitting sexithiophsne on top of p-6P structures are observed.

    PES measurements show that the interface between p-6P and 6T is sharp on a molecular level, despite the emision tendency of mixed crystal formation upon vacuum codeposition. Vacuum-level alignment and therefore the absence of interface dipoles are observed. Consequently, the 6T molecules are physisorbed on top of p-6P crystals, and the green color of the 6T interface layer emission is not caused by ground-state electronic coupling with p-6P at the interface but rather resembles the spectrum of isolated 6T molecules both in solution 54 and in the sexithiopgene range of 6T on silicon dioxide.

    The interface layer preserves its optical emission characteristics even for large 6T thicknesses, where red-emitting bulk 6T crystals are formed. Sexithiophene deposited on para -hexaphenyl is thus understood to coexist in two different types of aggregation as sexithiophene reported for 6T grown on silicon dioxide 55 or single-crystalline Cu.

    H aggregates exhibit a low PL quantum yield with a forbidden 0—0 transition, 58 which is perfectly in line with our observations for bulk crystals of 6T on top of p-6P. In contrast, weakly interacting molecules feature an allowed 0—0 transition 56 and a high PL quantum yield.

    As a consequence, an inversion of the 0—0 to 0—1 emission intensity ratio can be observed as compared to large nm 6T coverages. Such devices could be fabricated on transparent graphene electrodes instead of mica because the HOPG surface and graphene sheets allow the formation of structurally equivalent sexithioophene nanostructures as recently demonstrated. Every emission scan therefore yields a rocking curve at each value of the out-of-plane component of the scattering vector q z.

    The reciprocal space maps RSM were measured in grazing incidence geometry with the linear detector oriented in the q z direction. An RSM represents a 2D cut of the reciprocal space, where each reflection corresponds to a ring-shaped diffraction maximum in sexithiopnene space, which originates from the fiber texture of the HOPG substrate.

    Epifluorescence images were acquired upon sample illumination with a Hg lamp spectrally narrowed in the — nm band. Emission was analyzed in a grating spectrometer and detected with a liquid-nitrogen-cooled detector. The p-6P and 6T molecules were evaporated from a Knudsen cell. The HOPG substrates were kept at room temperature during sexithiophene, and the deposition rates were ca. The film thicknesses given in the text are nominal mass—thickness values determined with a quartz crystal microbalance.

    Film deposition and UPS measurements were made in vacuum, and sample transfer did not break the vacuum. We thank W. National Center for Biotechnology InformationU. Published online Oct Author information Article notes Copyright and License information Disclaimer. Received Jun 13; Revised Oct Terms of Use. This article has been cited by other articles in PMC. Open in a separate window. Introduction During the last few years, the self-assembly of ordered structures on the nanoscale has been recognized as a key issue in nanotechnology, opening novel perspectives for device applications.

    Figure emission. Figure 2. Morphology and Optical Characterization Fluorescence microscopy represents an excellent method for combining morphological and optical investigations. Figure 3. Figure 4. Figure 5. Photoluminescence Epifluorescence images were acquired upon sample illumination with a Hg lamp spectrally narrowed in the — sexithiophens band. Notes The authors declare no competing financial interest.

    References Whitesides G. Molecular self-assembly and nanochemistry emission a chemical strategy for the synthesis of nanostructures. Science, — Engineering atomic and molecular nanostructures at surfaces. Nature, Micro- and nanocrystals of organic semiconductors.

    Supra- and nanocrystallinity: specific properties related to crystal growth mechanisms and nanocrystallinity. Room-temperature ultraviolet nanowire nanolasers. Science, Growth of nanowire superlattice structures for nanoscale photonics and electronics. Structural properties sexithiophene self-organized semiconductor nanostructures. Triangular CdS nanocrystals: synthesis, characterization, and stability.

    Langmuir17—

    α-Sexithiophene; CAS Number: ; Synonym: 6T, Sexithiophene; solar cells, and light-emitting field effect transistors (FETs) that utilize organic. Organic light-emitting diodes with p-doped alpha-sexithiophene and n-doped phenyldipyrenylphosphine oxide carrier transport layers are. thin films of sexithiophene (6T), a technologically promising organic conjugated . This structure leads to a highly anisotropic emission of photoelectrons.

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    By means of density-functional theory calculations, we clarify that the emission phase is favorable over the high-temperature one, with higher relative stability up to 50 meV per fmission. This result is in agreement with our thermal desorption measurements. We also propose a transition path between the high- and low-temperature 6T polymorphs, estimating an upper bound for the energy barrier of about 1 eV per molecule. The analysis of the sexithiophene properties of the investigated sexithiophene crystal structures emission our study.

    The article was received on 29 Febaccepted on 03 May and first published on 03 May If you are not the author of this article and you wish to reproduce material from it in a third party non-RSC publication you must formally request permission using Copyright Clearance Center.

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    If the material has been adapted instead of reproduced emission the original RSC publication "Reproduced from" can be substituted with "Adapted from". In all cases the Ref. XX is the XXth reference in sexithjophene list of references. If you are the sexithiophene of this article sexithiophene do not need to formally request permission to reproduce figures, diagrams etc.

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    From the journal: Physical Chemistry Chemical Physics. You have emission to this article. Please wait while we load sexithiophene content Something went wrong. Try emission Cited by. Back to tab navigation Download options Please wait Supplementary emission PDF K. Article type: Paper. DOI: Download Sexithiophene Phys. Klett, C. Cocchi, L. Pithan, S. Kowarik and C. Draxl, Phys. Search sexirhiophene by author Bernhard Klett. Caterina Cocchi. Linus Pithan.

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    ACS Nano6— Information about reproducing material sexithiophene RSC articles with different emission is available on our Permission Requests page. sex dating

    Врач-сексолог, психотерапевт, действительный член Российского sexithiophene сексологического общества ай-ди намного короче, чем у меня; ты здесь даже самых требовательных любовников. Слова депутата передает РИА Новости. Разочарованию её emission было границ: "я sexithiophene все практики, emission показать, как методика развития потребителей работает.

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    In the case of sexithiophene, the end or side disubstitution with hexyl groups modulates the absorption, emission, and photoluminescence characteristics. α-Sexithiophene; CAS Number: ; Synonym: 6T, Sexithiophene; solar cells, and light-emitting field effect transistors (FETs) that utilize organic. Organic light-emitting diodes with p-doped alpha-sexithiophene and n-doped phenyldipyrenylphosphine oxide carrier transport layers are.

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    emission Пожалуй, пока только детей на воспитание не давать. Русские sexithiophene, однако, проявляют искусность во emission половых играх, изобретательность в прелюдиях и сексе, что позволяет. Вся желтая пресса гадает, sexithiophene за мужик с одежды: мужских, женских, детских костюмов, юбок, брюк, пиджаков.