Temperature-Dependent Circularly Polarized Luminescence of a Cholesteric Copolymer Doped with a Europium Complex

Abstract

The design of new materials for non-contact temperature sensors is an important task for scientists working in the fields of chemistry, physics, and materials science. In the present paper, a novel cholesteric mixture based on a copolymer doped with a highly luminescent europium complex was prepared and studied. It was found that the spectral position of the selective reflection peak strongly depends on temperature and a shift towards shorter wavelengths is observed upon heating with an amplitude of more than 70 nm, from the red to green spectral range. This shift is associated with the existence and melting of clusters of smectic order, as confirmed by X-ray diffraction investigations. The extreme temperature dependence of the wavelength of selective light reflection provides a high thermosensitivity of the degree of circular polarization of the europium complex emission. The highest values of the dissymmetry factor are observed when the peak of selective light reflection fully overlaps with the emission peak. As a result, the highest sensitivity of 65%/K for luminescent thermometry materials was obtained. In addition, the ability of the prepared mixture to form stable coatings was demonstrated. The obtained experimental results, i.e., the high thermosensitivity of the degree of circular polarization, and the ability to form stable coatings allow us to consider the prepared mixture as a promising material for luminescent thermometry.

Circularly Polarized Luminescence of Cholesteric Liquid Crystal Polymer Networks with a Europium(III) Complex as an Emitter

“…The emission intensity gradually weakened as the temperature increased, and the emission intensity was enhanced as the temperature decreased and recovered at room temperature. The temperature-sensitive emission could be attributed to thermally activated nonradiative processes at high temperatures, which was similar to what was observed in the literature. , Thus, the CLCN pattern can be used as a fluorescence temperature thermometry material.…”

“…The temperature-sensitive emission could be attributed to thermally activated nonradiative processes at high temperatures, which was similar to what was observed in the literature. 47,57 Thus, the CLCN pattern can be used as a fluorescence temperature thermometry material.…”

“…38 Chiral enantiomers based on Eu III complexes were prepared to study CPL performance. 39−44 The CPL properties of a spiral Eu(III) coordination polymer, 45 a Eu III -grafting chiral polymer, 46 and a cholesteric copolymer doped with a Eu III complex 47 were also reported. However, those reported | g lum | values were not very high, and the strategy to achieve high |g lum | values lacked a general rule.…”

“…Due to the antenna effect, Eu III complexes usually absorb light in the UV region and exhibit strong photoluminescence with large Stokes shifts, long emission lifetimes, sharp red emission bands, and relatively high absolute quantum yields (QYs) in both the solid state and solution state . Chiral enantiomers based on Eu III complexes were prepared to study CPL performance. − The CPL properties of a spiral Eu­(III) coordination polymer, a Eu III -grafting chiral polymer, and a cholesteric copolymer doped with a Eu III complex were also reported. However, those reported | g lum | values were not very high, and the strategy to achieve high | g lum | values lacked a general rule.…”

Charge Carrier Mobility in Poly(N,N′-bis-4-butylphenyl-N,N′-bisphenyl)benzidine Composites with Electron Acceptor Molecules

“…Due to stereocenters, the molecules can absorb photon incidents not only at right angles to the planes of aromatic rings [21,22], but also with a significant deviation from orthogonality increasing the harvest of incident light. In addition, stereocenters in the molecules can exhibit the effect of circularly polarized luminescence, for example, similar to polymers containing chiral fragments of cholesterol [23].…”