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  • 1
    Electronic Resource
    Electronic Resource
    Room-temperature phosphorescence and delayed charge-transfer fluorescence of coronene adsorbed on .gamma.-alumina (1983)
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 87 (1983), S. 4872-4877 
    Details
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/j150642a022
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  • 2
    Electronic Resource
    Electronic Resource
    Kinetik der Lumineszenz-Thermochromie und Zuordnung der Tieftemperaturemission von Pyridino-Cu(I)-jodid (1980)
    Springer
    Colloid & polymer science 258 (1980), S. 1098-1098 
    Details
    ISSN: 1435-1536
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01382445
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  • 3
    Electronic Resource
    Electronic Resource
    Fluorescence yields and molecular orientation of thin organic films: Vapor-Deposited Oligothiophenes α3T–α8T (1995)
    Springer
    Journal of fluorescence 5 (1995), S. 165-170 
    Details
    ISSN: 1573-4994
    Keywords: Thin organic films ; vapor-deposited oligothiophenes ; quantum yields
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The fluorescence quantum yields of vapor-deposited (VD) films of α-oligothiophenes,nT, with ring numbers ofn=3–8 and layer thicknesses ofd=3–50 nm were determined at room temperature andT=77 K and compared to the yields of dilute solutions and small (5T)x clusters. The yields of highly oriented ultrathin films are of the order of ΦF=5*10−5-1*10−4. The yields increase strongly with the layer thickness and also upon cooling, but do not reach the values in dilute solution. The main nonradiative deactivation step S1 → T1 in solution was quantified by1O2 production, the yields of which systematically decrease withn from ΦF (3T) to 0.36 (6T), in contrast to the fluorescence yields, which increase from ΦF=0.01 (2T) to 0.40 (6T). In films or clusters the S1 → T1 deactivation step must be a very unimportant side reaction: neither1O2 nor any signal of triplet-triplet absorption could be positively identified.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00727534
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  • 4
    Electronic Resource
    Electronic Resource
    Combined Fluorescence and NMR Studies of Reversed HPLC Stationary Phases with Different Ligand Chain Lengths (1997)
    Springer
    Journal of fluorescence 7 (1997), S. 311-315 
    Details
    ISSN: 1573-4994
    Keywords: HPLC stationary phases ; ligand length ; solid-state NMR spectroscopy ; time resolved fluorescence anisotropy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Alkyl chain bonded “reversed” HPLC phases consisting of 6 to 30 carbon atoms are investigated by fluorescence spectroscopy, steady-state and time-resolved fluorescence anisotropy, and solid-state NMR spectroscopy. The structure and dynamics of the interphase formed by alkyl chains and liquid phase penetrating each other are studied as a function of alkyl chain length. Increasing alkyl chain lengths lead to enhanced partitioning of the fluorescent probe diphenylhexatriene (DPH) into the interphase, as monitored by fluorescence decay curves. The concomitant spectral red shift of DPH fluorescence excitation maxima is evidence of increased interphase polarizability. Time-resolved fluorescence anisotropy measurements reveal that the motion of the probe molecule in the interphase is “wobble in cone”-like. Cone angles θ and rotational correlation times τR change from θ = 63° and τR = 0.75 ns in C6 phases to θ = 42° and τR = 1.50 ns in C30 phases, thus indicating decreasing probe mobility with increasing ligand length. This interpretation is supported by 13C CP/MAS NMR spectra, which show reduced contributions of alkyl chain gauche conformations, i.e., enhanced interphase order, in phases with long alkyl chains and high surface coverage. A concomitant increase in the line-widths of 1H MAS NMR peaks indicates reduced mobility of the longer chains. The spectroscopic observations are consistent with the results of HPLC separations, where enhanced shape selectivity is found with increasing ligand length, rod-shaped molecules like DPH showing the greatest increase in retention time.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1022534110945
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  • 5
    Electronic Resource
    Electronic Resource
    Fluorescence Study on Translational Mobility in Polystyrene–Polyethyleneglycol Microbeads (1998)
    Springer
    Journal of fluorescence 8 (1998), S. 171-177 
    Details
    ISSN: 1573-4994
    Keywords: Polystyrene–polyethyleneglycol microbeads ; translational mobility ; dynamic excimers ; pyrenebutyric acid
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Polyethyleneglycol (PEG) chain mobility in gelatineous microbeads is investigated by means of dynamic excimer formation. Pyrenebutyric acid (PYB) is covalently linked to the chain ends as probe molecule. Excimer formation is monitored by steady-state and time-resolved fluorescence spectroscopy in the presence of a series of liquid phases and in the dry state. PYB concentration in the beads is varied over three orders of magnitude up to c = 6·10−2 M. The concentration is derived from absorption measurements in stirred bead suspensions, considering the deviations from Lambert–Beer's law in heterogeneous systems. Excimer formation is found to be a dynamic process in the presence of liquid phases which solvate both the polymer and the fluorophore. The collisional rate constant, k DM, is of the order of k DM-values of PYB in homogeneous solutions, indicating a high translational mobility. Excimer-to-monomer intensity ratios are in general accordance with the solvation capacity of the liquid phase. In the dry state excimer formation is found only at high PYB concentrations, c ≈ 3·10−2 M. It is concluded that this excimer emission arises from aggregated PYB, since corresponding fluorescence response curves show no rise time.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1022506627591
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  • 6
    Electronic Resource
    Electronic Resource
    Possibilities of kinetic analysis of micellar solutions by use of microprocessor-controlled UV/VIS-spectrometry (1982)
    Springer
    Fresenius' Zeitschrift für analytische Chemie 311 (1982), S. 443-443 
    Details
    ISSN: 1618-2650
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00481807
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  • 7
    Electronic Resource
    Electronic Resource
    In situ characterization of electrochemically-formed oxide films on low carbon steel by diffuse reflectance spectroscopy (1984)
    Springer
    Fresenius' Zeitschrift für analytische Chemie 319 (1984), S. 695-700 
    Details
    ISSN: 1618-2650
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Summary The mechanism of corrosion of steel and iron is studied by the combination of cyclic voltammetry and diffuse reflectance absorption spectroscopy (DRS). The method is especially valuable to investigate samples with rough or polycrystalline surfaces without prior preparation as it is the case for cold rolled low carbon steel. The sensitivity depends on the absorption coefficients of the oxide film. In the case of the Fe2+/Fe3+-redox-system it is possible to investigate the formation and reduction of the passive layer even with under monolayer coverage. The spectroscopic measurements allow to identify the formation of Fe2+-Fe3+-mixed oxides which are responsible for protective or non-protective films. Spectra of different modifications of iron oxide powders are also given.
    Notes: Zusammenfassung Mit Hilfe der Kombination von cyclischer Voltammetrie und der diffusen Reflexionsspektroskopie läßt sich der Mechanismus der Korrosion von Stahl und Eisen untersuchen. Die Methode ist besonders geeignet zur Untersuchung von rauhen und auch polykristallinen Oberflächen, wie es der Fall ist bei Tiefziehblechen. Die Proben können ohne Vorbehandlung wie z.B. Polieren direkt eingesetzt werden. Die Empfindlichkeit liegt beim Eisensystem bei unter monomolekularer Bedeckung des Oxids auf dem Metall. Durch die spektroskopischen Untersuchungen ist es möglich, die Bildung von Mischoxiden zu verfolgen. Diese Oxide sind verantwortlich für die Bildung von schützenden oder weniger schützenden Passivschichten. Es werden auch Beispiele von Absorptionsspektren verschiedener Modifikationen von Eisenoxiden gegeben.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01226751
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  • 8
    Electronic Resource
    Electronic Resource
    Über geordnete Perowskite mit Kationenfehlstellen. XI. Das System Ba2Gd2/3□1/3U1-xWxO6 (1982)
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 495 (1982), S. 219-231 
    Details
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: On Ordered Perovskites with Cationic Vacancies. XI. System Ba2Gd2/3□1/3U1-xWxO6The cation deficient polymorphic perovskites Ba2Gd2/3□1/3UO6 and Ba2Gd2/3□1/3WO6 form a continuous series of mixed crystals, which crystallize over a wide range (x = 0.1 up to 0.99) in a cubic 1:1 ordered perovskite lattice. According to the investigations of the vibrational spectra, the diffuse reflectance spectra, and the photoluminescence  -  opposite to isostructural perovskites without vacancies  -  different species of UO6 and WO6 octahedra are present. Numerous differences in properties  -  e. g. an orange emission colour in comparison with a green one by absence of vacancies  -  are based upon that.
    Notes: Die beiden fehlstellenhaltigen, polymorphen Perowskite Ba2Gd2/3□1/3UO6 und Ba2Gd2/3□1/3WO6 bilden eine lückenlose Reihe von Mischkristallen, die in einem weiten Bereich (x = 0,1 bis 0,99) in einem kubischen 1:1 geordneten Perowskitgitter kristallisieren. Wie die Untersuchung der Schwingungsspektren, der diffusen Reflexionsspektren und der Photolumineszenz zeigen, liegen  -  im Gegensatz zu isostrukturellen fehlstellenfreien Perowskiten  -  mehrere Sorten an UO6- und WO6-Oktaedern vor. Hierauf sind zahlreiche Eigenschaftsunterschiede  -  z. B. eine orangefarbene Emission im Unterschied zu einer grünen bei Abwesenheit von Fehlstellen  -  zurückzuführen.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/zaac.19824950123
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  • 9
    Electronic Resource
    Electronic Resource
    Investigation of Structure and Mobility of Silica Bonded Stationary Acridine Phases by Means of Fluorescence and NMR Spectroscopy (1998)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 21 (1998), S. 11-17 
    Details
    ISSN: 0935-6304
    Keywords: Acridine-modified HPLC stationary phases ; ligand mobility ; fluorescence spectroscopy ; time-resolved fluorescence anisotropy ; solid state NMR spectroscopy ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---Ligand mobility of silica-based HPLC stationary phases modified by various surface coverages of acridine-9-carboxy(N-aminoethylaminopropyl)amide ligands was investigated by fluorescence spectroscopy, time-resolved fluorescence anisotropy measurements, as well as solid-state 13C-CP/MAS- and 1H-MAS-NMR spectroscopy. Rotational correlation times, τR, of the bound acridine fluorophore obtained from fluorescence anisotropy measurements are significantly longer in the bound phase, than in solution. Also, in time-resolved experiments anisotropies do not decay to zero. These results are interpreted in terms of wobble-in-cone ligand motion. The mobility of the fluorophore in the presence of liquid phase correlates strongly with the solubility of the model compound acridine-9-carboxy-n-butylamide in the same solvent. In the good solvent acetonitrile τR = 3.2 ns is found, whereas in methanol, τR 〉 80 ns is obtained. NMR measurements of the dry phase yield large linewidths, cross polarization constants, TCH, and spin-lattice relaxation times, T1ρH, shifting around the minimum in the correlation time curve. Both fluorescence and NMR data indicate medium to low ligand mobility. No difference in the mobilities of alkyl spacer and aromatic group is observed, probably due to the rigidity of the amide group.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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