Two-Photon Excited Luminescence in Polyethylene and Polytetrafluoroethylene
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Journal of Russian Laser Research, Volume 41, Number 5, September, 2020
TWO-PHOTON EXCITED LUMINESCENCE IN POLYETHYLENE AND POLYTETRAFLUOROETHYLENE Maria Tareeva,1 Mikhail Shevchenko,1 Sofia Umanskaya,1 Vladimir Savichev,1 Anatoly Baranov,2 Nikolay Tcherniega,1 and Anna Kudryavtseva1∗ 1 Lebedev
Physical Institute, Russian Academy of Sciences Leninskii Prospect 53, Moscow 119991, Russia 2 Lomonosov
Moscow State University Moscow, Vorob’evy Gory, Moscow 119991, Russia ∗ Corresponding
author e-mail:
kudryavcevaad @ lebedev.ru
Abstract Luminescence spectra of polytetrafluoroethylene (Teflon), a Teflon film, and a polyethylene film are registered in wide wavelength range under excitation by radiations with different wavelengths. For the first time, we detect two-photon-excited luminescence in polymers at low intensity of exciting light. In Teflon, we also register luminescence in the blue range under excitation by ruby laser pulses.
Keywords: luminescence, polymers, spectrum, up conversion, two-photon excitation.
1.
Introduction
The study of luminescence in substances with complex nanostructures and submicrometer structures (in nanomaterials or in polymers) is of great interest from the point of view of various applications and for better understanding the processes occurring in the substances under impact of the electromagnetic radiation. Luminescence studies were carried out both in highly-ordered nanomaterials, for example, in opal matrices [1, 2], and in substances with a disordered structure, such as suspensions of nanoparticles, Teflon, and polyethylene [3–8]. Luminescence in nanomaterials and polymers has some analogies with luminescence in semiconductor materials; however, the forbidden zones in these substances are less defined than in semiconductors. In addition, the position of the zones depends on a number of parameters, such as the nanoparticle sizes, the properties of substances filling the pores between the nanoparticles, etc. As a rule, luminescence is excited employing sources of UV radiation – ultraviolet lasers or lamps. However, it has recently become clear that luminescence can also be very effectively excited by light sources with a wavelength longer than the luminescence wavelength. This process is called the up conversion or anti-Stokes luminescence. The different physical–chemical mechanisms of the up conversion have some specific features, making them more or less effective for different applications [9]. For instance, triplet–triplet-annihilation-based photon up conversion (TTA-UC), which implicates a sequence of photo-physical processes in dyes, allows the frequency up-shifting of low-intensity light [10], which meets the challenges of effective photoelectric conversion of solar energy [11]. The TTA-UC mechanism was first suggested in [12] for anthracene and phenanthrene, and it was described in detail in [13] for polycyclic aromatic compounds, such as polyacenes as emitters with high-quantum yield of luminescence. The most commonly used sensitizers are Manuscript submitted by the authors in English o
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