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  • 1
    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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  • 2
    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
    Library Location Call Number Volume/Issue/Year Availability
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    Paper (German National Licenses)
    Fulltext
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