External Electric Field Effects on Fluorescence of Pyrene Butyric Acid in a Polymer Film:  Concentration Dependence and Temperature Dependence

Abstract

Fluorescence spectra and electrofluorescence spectra (plots of the electric field-induced change in fluorescence intensity as a function of wavelength) have been measured at different temperatures for pyrene butyric acid (PBA) in a PMMA film at different concentrations. At a low concentration of 0.5 mol % where fluorescence emitted from the locally excited state of PBA (LE fluorescence) is dominant, LE fluorescence spectra show only the Stark shift in the presence of an electric field (F), which results from the difference in molecular polarizability between the ground and emitting states. At a high concentration of 10 mol % where the so-called sandwich-type excimer fluorescence (EX(1)) is dominant, both EX(1) and LE fluorescence are quenched by F. Another fluorescence assigned to a partially overlapped excimer (EX(2)) also exists at room temperature, and this emission is enhanced by F. As the temperature decreases, three fluorescence emissions whose electric field effects are different from each other become clear besides EX(1) and LE fluorescence, indicating that at least five fluorescence components exist at high concentrations at low temperatures. At a medium concentration of 5 mol % where EX(1) is comparable in intensity to the LE fluorescence, the intensity of EX(1) is not affected by F at any temperature, but LE fluorescence and EX(2) are markedly influenced by F at room temperature, and four fluorescence emissions are confirmed at low temperatures.

Magnetic field effects on electro-photoluminescence of photoinduced electron transfer systems in a polymer film

“…The former exciplex fluorescence shows the magnetic field effect even in the absence of F, while EX ECZ-DMTP (45) shows the synergy effect which is similar to the one observed in the pair of ECZ and DCB. Thus, the magnetic field effects of the exciplex fluorescence in the ECZ and DCB pairs are very different from the one in the pair of ECZ and DMTP, indicating that the synergy effect as well as the magnetic field effect or electric field effect depend on donor (D) as well as on acceptor (A).…”

“…A noticeable magnetic field effect was not observed in the absence of F for I PL both of the LE fluorescence and of the exciplex fluorescence, i.e., EX ECZ-DMTP (45), but a significant magnetic field effect was observed for I PL both of the LE fluorescence and of EX ECZ-DMTP (45). It should be noted that the magnetic field effect on I PL as well as on I PL was observed for the broad PL with a peak at ~380 nm, assigned to another exciplex fluorescence between ECZ and DMTP.…”

“…In a mixture of ECZ and DMTP in a PMMA film, broad exciplex fluorescence with a peak at 450 nm, denoted by EX ECZ-DMTP (45), was observed following excitation into ECZ as a result of PIET from the excited state of ECZ to DMTP besides the structured LE fluorescence emitted from ECZ in the region of 350~400 nm, and both fluorescence emissions were quenched by F (see Figures 3a,b).…”

“…In the former case, however, the synergy effect of F and H was observed even when the concentrations of ECZ and DCB were replaced by each other, as mentioned below. In the pair of ECZ and DMTP, further, two kinds of exciplex fluorescence, i.e., EX ECZ-DMTP (38) and EX ECZ-DMTP (45), exist in a PMMA film.…”

Stark fluorescence spectroscopy on peridinin–chlorophyll–protein complex of dinoflagellate, Amphidinium carterae

“…The precise knowledge about the nature of PCP fluorescence is essential since a clear understanding about the pathways and mechanisms that PCPs follow for deactivating their singlet exciton energy via fluorescence is still nebulous. Stark spectroscopy, which monitors electric field-induced changes in absorption (Stark absorption, SA) or fluorescence (Stark fluorescence, SF), can be used to probe and quantify the change in electrostatic parameters such as permanent dipole moment and molecular polarizability following optical excitation and/or relaxation (Wahadoszamen et al 2007(Wahadoszamen et al , 2012(Wahadoszamen et al , 2014a(Wahadoszamen et al , b, 2015Ara et al 2006Ara et al , 2007Bublitz and Boxer 1997), as well as to probe the rates of excited state reactions and deactivations and their response to an electric field (Wahadoszamen et al 2014b). The determination of these parameters is essential for the characterization of the excited state electronic structures and dynamics of the molecule or molecular aggregate under study.…”