Poly simultaneous fluorescence

Time-resolved fluorescence spectroscopy and fluorescence anisotropy measurements have been applied to study (i) excimer formation and energy transfer in solutions of poly(acenaphthalene) (PACE) and poly(2-naphthyl methacrylate) (P2NMA) and (ii) the conformational dynamics of poly(methacrylic acid) (PMA) and poly (acrylic acid) as a function of solution pH. For PACE and P2NMA, analysis of projections in which the spectral, temporal and intensity information are simultaneously displayed have been used to re-examine kinetic models proposed to account for the complex fluorescence decay behaviour that is observed. Time-resolved fluorescence anisotropy measuranents of fluorescent probes incorporated in PMA have led to the proposal of a "connected cluster" model for the hypercoiled conformation of this polymer existing at low pH. 

We employ method B to study effects of this type. In this mode, our apparatus yields relative high-resolution fluorescence spectra at different time windows after excitation of the sample by the 355 nm pulse. The spectra are acquired by the upconversion method. The upconverted fluorescence spectrum is recorded simultaneously at all monitored wavelengths by an optical multichannel analyzer. It is constructed from a poly-chromator (HR320 Instruments SA) and an intensified silicon photodiode array detector (Princeton Applied Research Model 1412). The detector is interfaced to our Cromemco computer. 

It has been shown [155,171] that the dependence of excimer emission intensity on acceptor concentration obeys the Stern—Volmer equation whether M or D is the donor, whereas a second-order equation is obtained if both types of excited state simultaneously act as donor. It seems that in poly-1-vinylnaphthalene and polyacenaphthalene films at room temperature, energy transfer to benzophenone occurs from M, although normal fluorescence cannot be detected in the emission spectrum of the polymers in these conditions [155]. Decay time measurements have shown that the excimers in solid polyvinylcarbazole are traps rather than intermediates in the energy transfer process [148]. With polystyrene, however, it has been clearly demonstrated that energy transfer to tetraphenylbutadiene occurs from both excimer and isolated excited chromophore [171]. 

Poly (styrene-afo-methyl methacrylate) undergoes yellowing more rapidly in vacuum than in air. The major yellowing moiety is a species related to l,5-diphenyl-l,3,5-hexatriene. Simultaneous photolysis of the triene results in a reduction in the rate of yellowing with increasing time of irradiation oxidative reactions of the triene appear to reduce the rate of yellowing in air. Fluorescence quenching takes place by processes that are the same in air and vacuum. 

A stopped-flow setup can relatively easily be equipped with multispectral detection. The fluorescence light is emitted from a small spot in the flow channel. Therefore the flow cell can be placed directly in the input slit plane of a poly-chromator. The spectram is detected by a multianode PMT. The photons detected in the spectral channels are recorded simultaneously by a TCSPC device and a router. However, although the implementation is relatively simple, no spectrally resolved TCSPC-based stopped-flow system has yet been described. 

Fig. 20 SNOM images of a 250 nm thick film of poly(9,9-didodecylfluorene) prepared by spin coating from toluene solution (a) topography, (b) total fluorescence intensity calculated from sum of the two polarized images (c) and (d) fluorescence collected simultaneously at orthogonal polarization, (e) anisotropy image calculated from panels c and d, and (f) simulated anisotropy image assuming the polymers are perfectly oriented in 15 nm cubic domains. Reprinted with permission of [68], copyright (2000) American Chemical Society...

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