Photoluminescence of Zn1 – х – yCuxEuyS/EuL3 Quantum Dots in a Polyacrylate Matrix

Zinc sulfide is one of the most popular luminescent semiconductors of the А(II)B(VI) group. Doping of ZnS quantum dots (QDs) with Ln3+ ions makes it possible to form in a semiconductor matrix nanosized structures containing isolated narrowband luminescence centers. Incorporation of QDs into ac-rylate matrices additionally stabilized particles and allows formation of their morphology. The Zn1 ‒ x ‒ yCuxEuyS/EuL3 nanosized structures, where L is a trifluoroacetate anion, are synthesized in situ in methylmethacrylate (MMA) by the method of appearing reagents. Doping of ZnS was performed by introduction of soluble zinc sulfide precursors simultaneously with copper and europium trifluoroacetates into the acrylate reaction mixture. The optically transparent polymer composites PММА/Zn1 – x – yCuxEuyS/EuL3 were obtained by radical casting polymerization of MMA. The excitation of luminescence in the composites is related to electronic interband transitions in ZnS, to the system of levels formed by dopant ions in the ZnS band gap, and to the intrinsic energy absorption by Eu3+ ions. The broadband luminescence of the composites is caused by intracrystalline defects formed in ZnS upon doping. The narrowband luminescence results from the 5D0 → 7Fj electronic transitions of Eu3+ ions bound to QDs and existing in the polymer matrix independently of them. The energy transfer from the donor levels of the semiconductor matrix to the levels of Eu3+ with subsequent luminescence is confirmed by the overlap of the absorption bands of doped ZnS and the luminescence excitation bands of the composites, as well as by an increase in the intensity of the narrowband luminescence of Eu3+ simultaneously with a decrease in the intensity of the broadband recombination luminescence of doped ZnS. The decrease in the intensity of the recombination luminescence of ZnS with increasing concentration of Eu3+ to >1.0 × 10–3 mol/L is also related to the formation of a layer of europium complex compounds on the surface of particles, which hinders the propagation of exciting radiation to the particle core.