Synthesis and Photoluminescence of Cd_{1 –x}(Ca,Sr)_xS:Eu³⁺ Nanostructures in a Polyacrylate Matrix

Abstract

: Colloidal Cd_{1 –x}(Ca,Sr)_xS and Cd_{1 –x}Ca_xS:Eu³⁺ (0 < x < 0.20) quantum dots (QDs) have been synthesized by an emerging reagent method in a methylmethacrylate (MMA) medium. The mole fraction of Eu³⁺ in the starting reaction mixtures was varied from 0 to 0.80 relative to the Ca²⁺ concentration. Using radical block polymerization of MMA, we have obtained transparent luminescent polymethylmethacrylate (PMMA) based composites: PMMA/Cd_{1 –x}(Ca,Sr)_xS and PMMA/Cd_{1 –x}Ca_xS:Eu³⁺. Luminescence excitation in the composites is due to interband electron transitions in the CdS and electron transitions from the ground state to excited states of the Eu³⁺ ions. The observed broadband luminescence is due to structural defects in the CdS crystals, and narrow-band luminescence originates from ⁵D₀ → ⁷F_j electron transitions of the Eu³⁺ ions in the bulk of the CdS crystals, in complexes on their surface, and in the bulk of the polymer matrix, independent of the semiconductor particles. The position and intensity of the observed spectral bands depend on the composition and concentration of the components, excitation wavelength, and other factors.