Abstract
In this paper, we investigate the effects of gamma (γ) radiation on the spectral and mplified spontaneous emission (ASE) properties of two conjugated polymers (CPs) viz., poly [2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] (MEH–PPV) (CPM) and poly{[2-[2′,5′-bis(2″-ethylhexyloxy)phenyl]-1,4-phenylenevinylene]-co-[2-methoxy-5-(2′-ethylhexyloxy)-1,4-phenylene vinylene]} (BEHP-co-MEH–PPV) (BMP) in tetrahydrofuran (THF). Gamma irradiation strongly affected the photophysical properties of these CPs. To explore these changes, gamma radiation, in the range of 2–50 kGy, was used to maintain the temperature at 5 °C constant for all doses at a dose rate of 12.67 kGy/h, using a 60Co gamma ray. The ASE profiles of the CPs in THF were obtained under the high power excitation of a Nd:YAG laser (355 nm), pre- and post-radiation. The result revealed a dramatic blue shift of the fluorescence and the ASE spectra after gamma irradiation. This shift in the luminescence and ASE spectra could be a response to the conformational disorders such as gamma irradiation-induced polymer crosslinking, which was verified using Raman spectra, FTIR, and swelling experiments. This could be the first report on the effect of gamma radiation on the ASE properties of conjugated polymers.
Highlights
IntroductionLight emitting diodes (LEDs) based on conjugated polymers have generated great interest because of their potential applicability to large areas and flat panel displays, their ability to operate at relatively low voltage, their low cost, and their easy fabrication [1]
In this paper, we investigate the effects of gamma (γ) radiation on the spectral and mplified spontaneous emission (ASE) properties of two conjugated polymers (CPs) viz., poly
Light emitting diodes (LEDs) based on conjugated polymers have generated great interest because of their potential applicability to large areas and flat panel displays, their ability to operate at relatively low voltage, their low cost, and their easy fabrication [1]
Summary
Light emitting diodes (LEDs) based on conjugated polymers have generated great interest because of their potential applicability to large areas and flat panel displays, their ability to operate at relatively low voltage, their low cost, and their easy fabrication [1]. Conjugated polymers can be excited via charge injection or photo-excitation. These macromolecules show spectral properties similar to those of optically active small organic molecules, such as laser dyes. Conjugated polymers possess characteristics of broadband emission appropriate for tunable lasers, with strong powers of absorption and emission, a large Stokes shift, high luminescence, and substantial quantum yield. Many fluorescent organic molecules such as laser dyes reveal a very low quantum yield at higher concentrations because of reabsorption and are unable to emit laser light, Polymers 2017, 9, 7; doi:10.3390/polym9010007 www.mdpi.com/journal/polymers
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