Emission spectra poly

A study of the valence band photoelectron spectrum and the X-ray emission spectrum of poly(ethylene oxide) was carried out by Brena and co-workers [102] in order to understand the effect of conformation on the observed spectra. Up to 12 monomers were used in the calculations for the valence band photoelectron... 

A first generation poly(amido amine) dendrimer has been functionalized with three calyx[4]arenes, each carrying a pyrene fluorophore (4) [30]. In acetonitrile solution the emission spectrum shows both the monomer and the excimer emission band, typical of the pyrene chromophore. Upon addition of Al3+ as perchlorate salt, a decrease in the excimer emission and a consequent revival of the monomer emission is observed. This can be interpreted as a change in the dendrimer structure and flexibility upon metal ion complexation that inhibits close proximity of pyrenyl units, thus decreasing the excimer formation probability. 1H NMR studies of dendrimer 4 revealed marked differences upon Al3+ addition only in the chemical shifts of the CH2 protons linked to the central amine group, demonstrating that the metal ion is coordinated by the dendrimer core. MALDI-TOF experiments gave evidence of a 1 1 complex. Similar results have been obtained for In3+, while other cations such as Ag+, Cd2+, and Zn2+ do not affect the luminescence properties of... 

Fig. 14 A The emission spectrum from a chloroform solution of Au fMeN = COMe)3. B The emission spectrum from a polycrystalline sample of Au fMeN = COMe)3. C The spectrum of the light emitted from a poly-crystalline sample of AuVMeN = COMe)3 after UV irradiation and contact with a drop of chloroform. From [43]...

Sato and Woody found a preference for binding left-handed conformers of ANS to the beta form of poly(Lys) and suggested that the dyes are bound to the polypeptide in regions of low polarity due to the increase in fluorescence quantum yield and the blue shift in the emission spectrum [261],... 

Fig. 15. Rotatory artifacts that simulate Cotton effects at an absorption band. The dependence of the rotatory artifact on absorbance of p-cresol solutions placed in series with the same poly-L-glutamic acid solution is shown. The concentration of p-cresol was adjusted to give the total absorbance of chromophore plus polypeptide background that appears with each curve. The rotator, poly-L-glutamic acid, was at concentration of 0.5% at pH 7.0 in a 10-cm cell. The rotations are those actually observed, a, in degrees. The rotatory dispersion at Am 2 coincides almost exactly with that for the polypeptide alone, so that it has been omitted from the figure. At Am 4, an interference filter, /, with maximum transmission between 280 and 285 m/i, was placed in the optical path. The absorption spectrum, in arbitrary units, is typical of p-cresol plus poly-L-glutamic acid background. The emission spectrum is represented in arbitrary units, uncorrected for detector response. (Urnes et al., 1961a.)...

Fig. 16. The appearance of rotatory artifacts both at the minimum in the emission spectrum of the mercury arc and as increasing polypeptide absorption is encountered below 250 m/i. The rotations are those actually observed, a, in degrees, for a 0.6% poly-L-glutamic acid solution at pH 7 in a 10-cm cell. The absorption spectrum of poly-L-glutamic acid and the emission spectrum of the arc, uncorrected for detector response, are in arbitrary units. (Urnes et al., 1961b.)...

The PL spectrum of a thin film of poly(3,6-dibenzosilole) 31 at 77 K exhibited a 0-0 transition at 3.5 eV and a second maximum at 3.3 eV (excitation at 4.4 eV) [41]. The phosphorescence emission spectrum at 77K consists of a broad band exhibiting vibronic structure (excitation at 3.9 eV). The polymer triplet energy level was taken to be the onset of triplet emission at 2.55 eV. This is considerably higher than the triplet energy of commonly used polyfluorenes (2.1 eV) [10,46] making it a host for phosphorescent emitters without the risk of energy back-transfer onto the polymer. 

Fig. 25. Single-photon-induced emission spectrum (curve a) and two-photon pumped lasing spectra at various energy levels (curves b-d) ofthe poly(DHASI-HEMA) system. From [91]...

With a glassy solution of poly-1-vinylnaphthalene, the delayed emission spectrum has been shown to consist of an emission having a mean lifetime of approximately 80 ms at the normal fluorescence wavelength, in addition to the phosphorescence having a mean lifetime of about 2 s [159]. The delayed fluorescence did not appear in the spectrum of 1-ethylnaphthalene. With the polymer it was found to be inhibited by piperylene, a well-known triplet quencher. These results have been explained by mutual annihilation of two excited triplet states produced by the absorption of two photons by the same polymer molecule. They are considered as strong evidence for migration of the excited triplet state in poly-1-vinylnaphthalene. In polyacenaphthalene, however, which is chemically very similar to poly-1-vinylnaphthalene (see p. 409), no delayed fluorescence could be detected in the same experimental conditions [155]. 

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]. 

Fluorescence studies 14, 15) using pyrene, pyrene derivatives, and cationic probes in poly(methacrylic acid) have shown that a conformational transition from a closed compact coil to extended form induced by pH is a progressive process over several pH units (pH 4-6). The emission spectrum of 4 X 10 M R6G and 4 X 10 M RB excited at 480 nm in water is not dependent on pH. However, in aqueous solutions of PM A, the spectra are significantly dependent on pH (shown in Figure 6). At pH 4-5, the spectra are similar to the typical emission of RB at pH 2-3 and 6-7, the spectra in PMA display stronger emission at 550 nm and at pH 8, the spectra are identical to those in water. 

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