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51.
We present the fabrication and optical investigation of highly random self-assembled, nano-scale films, probing their influence
on the luminescence properties of near surface CdSe/ZnS colloidal quantum dots. When compared to quantum dots distributed
on unstructured quartz substrates, the average luminescence intensity is found to be enhanced by a factor of 160×. The silver
nanoparticles are prepared using slow thermal evaporation on quartz substrates and post-deposition annealing to produce a
randomly-arranged layer of smooth nano-islands. Clear polarization dependent hot spots are observed. Such hot spots deliver
a maximal enhancement of the emission intensity of 240× and have a spatial density of (0.050±0.002) μm − 2. The results show that silver nano-island films strongly enhance the optical efficiency of near quantum dots emitters. 相似文献
52.
Florian Kretschmer Stefan Mühlig Stephanie Hoeppener Andreas Winter Martin D. Hager Carsten Rockstuhl Thomas Pertsch Ulrich S. Schubert 《Particle & Particle Systems Characterization》2014,31(7):721-744
The unique properties of plasmonic nanostructures have fuelled research based on the tremendous amount of potential applications. Their tailor‐made assemblies in combination with the tunable size and morphology of the initial building blocks allow for the creation of materials with a desired optical response. In this respect, it is crucial to synthesize nanoparticles with a defined shape that are at the core of such developments. Moreover, the interaction of individual nanoparticles with an incident electromagnetic field cannot only be influenced by their structure, but in fact, also by their spatial arrangement to each other. To harvest such opportunities, a profound theoretical understanding of these interactions is required as well as concise strategies to create such ordered assemblies. A quantitative evaluation of their optical properties can only be conducted when discrete structures of high uniformity can be achieved. As a consequence, separation steps have to be applied in order to obtain materials of high purity and uniformity. This also allows for an easier structural characterization of the nanoparticles and their assembled superstructures. In this progress report, an overview about the current development in this field of research is provided. 相似文献
53.
A. Morozov T. Heindl J. Wieser R. Krücken A. Ulrich 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2008,46(1):51-57
Continuous and pulsed 12 keV electron beams were used to excite nitrogen
within a gas cell at pressures ranging from 10 to 1400 hPa. The pressure
dependence of the ratio of photon fluxes for emission from vibrational
levels v'=0 and 1 of the C 3Π u state has been studied. The
results confirm the presence of a collisional excitation mechanism
populating v'=0, 1 in addition to electron impact excitation. Rate constants
of (1.27 ±0.04)×10-11 cm3s-1 [ v'=0] and
(2.68 ±0.08)×10-11 cm3s-1 [ v'=1] were measured for
C 3Π u quenching by ground state nitrogen. For electron beam
conditions relative excitation efficiencies of 1:0.59:0.22 for
vibrational levels 0, 1 and 2 were calculated. The recorded flux ratios are
compared with the predictions given by a vibrational relaxation model. 相似文献
54.
Well-defined and homogeneous, contamination-free self-assembled monolayers (SAMs) were fabricated by the chemisorption of lip-NH-p-C6H4-NN-p-C6H4-COOH (lip = α-lipoyl) onto gold. This adsorbate species is composed of a 1,2-dithiolane-based headgroup, an azobenzene-based (and hence photochromic) spacer unit and a carboxylic acid functional group. The SAM constituents are covalently attached to the substrate by the bidentate thiolate anchor groups and exhibit a strongly tilted binding configuration. 相似文献
55.
Franziska Schulte Klaus‐Werner Brzezinka Karin Lutzenberger Heike Stege Ulrich Panne 《Journal of Raman spectroscopy : JRS》2008,39(10):1455-1463
Raman microscopy allows a non‐destructive characterisation of inorganic and organic painting materials such as pigments and organic dyestuffs. The objectives of this study are the more recent organic pigments typically present in paintings and other art works from the 20th century. More than 20 organic synthetic pigments from different chemical classes could be identified by Raman spectroscopy using different excitation wavelengths (457.9, 476.5, 487.9, 514.5, 632.8, and 1064 nm). To evaluate the performance for real paint samples, varying paint mixtures of the Hansa Yellow pigment PY 3 and the binding medium Mowilith, a polyvinyl acetate (PVAC) compound, were characterised; PY 3 was determined at a 1 wt% level in the binder. In addition, commercial tube paints containing the quinacridone violet PV 19 were studied. The pigment was clearly identified in all of these more complex oil and acrylic paints. Finally, alizarin (PR 83) and a green copper phthalocyanine pigment (PG 7) could unambiguously be identified by Raman microscopy in the painting ‘Woman with mandolin in yellow and red’ of Max Beckmann dating 1950. The discovery of a red naphthol AS pigment by Raman spectroscopy in a sample from the ‘Three field workers’ by Georg Baselitz (1964/1965) demonstrated that in some cases complementary chromatographic methods are needed for a comprehensive identification of the organic pigments. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
56.
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58.
Ulrich Schwenk und Erhard Weber 《Fresenius' Journal of Analytical Chemistry》1958,164(1):159-164
Zusammenfassung An Stelle der Podbielniak-Analyse für Gasproben, die neben Inertgasen und leichten Kohlenwasserstoffen auch C5- und höhere Kohlenwasserstoffe enthalten, wird ein neues Verfahren vorgeschlagen. Die Inertgase und leichten Kohlenwasserstoffe werden wie üblich gaschromatographisch bestimmt. Zusätzlich trennt man aus einer zweiten Probe gaschromatographisch die leichten Anteile ab, spült durch Umkehr der Trägergasrichtung die Summe der schweren Kohlenwasserstoffe wieder aus der Säule und bestimmt ihre Menge durch Wägung. 相似文献
59.
Ulrich Kohlenbach 《Journal of Mathematical Analysis and Applications》2003,279(2):531-544
In Numer. Funct. Anal. Optim. 22 (2001) 641-656, we obtained an effective quantitative analysis of a theorem due to Borwein, Reich, and Shafrir on the asymptotic behavior of general Krasnoselski-Mann iterations for nonexpansive self-mappings of convex sets C in arbitrary normed spaces. We used this result to obtain a new strong uniform version of Ishikawa's theorem for bounded C. In this paper we give a qualitative improvement of our result in the unbounded case and prove the uniformity result for the bounded case under the weaker assumption that C contains a point x whose Krasnoselski-Mann iteration (xk) is bounded. We also consider more general iterations for which asymptotic regularity is known only for uniformly convex spaces (Groetsch). We give uniform effective bounds for (an extension of) Groetsch's theorem which generalize previous results by Kirk, Martinez-Yanez, and the author. 相似文献
60.
David Eisenbud Craig Huneke Bernd Ulrich 《Proceedings of the American Mathematical Society》2003,131(3):701-708
In this paper we show that the Rees algebra can be made into a functor on modules over a ring in a way that extends its classical definition for ideals. The Rees algebra of a module may be computed in terms of a ``maximal' map from to a free module as the image of the map induced by on symmetric algebras. We show that the analytic spread and reductions of can be determined from any embedding of into a free module, and in characteristic 0--but not in positive characteristic!--the Rees algebra itself can be computed from any such embedding.