Synthesis, structures, luminescent and color properties of polyethylmethacrylate (PEMA) polymers doped with rare earths

Solid-state bulk polymer hosts doped with rare earths are expected to play a central role in the development of future light-emitting diodes and photonic devices due to the superior properties of polymers. In this study, linear polyethylmethacrylate (PEMA) and crosslinked PEMA gels doped with CdNb₂O₆: Er³⁺/Yb³⁺ nanocrystal powders were synthesized by free-radical crosslinking copolymerization. Er³⁺/Yb³⁺ ion structures embedded in PEMA polymers were investigated by the X-ray diffraction technique. The average crystalline particle sizes were found using the Pielazsek particle distribution and the Scherrer equation. The particle sizes decreased from 60 to 17 nm for CdNb₂O₆: Er³⁺/Yb³⁺ powders when they were embedded in PEMA polymers. Transmission electron microscopy and scanning electron microscopy monitored the change in the morphology of polymer samples doped with CdNb₂O₆: Er³⁺/Yb³⁺ powders. The optical properties of polymer samples were investigated by measuring luminescence spectra at room temperature. The doped Er³⁺/Yb³⁺ ion excited with a 975 nm diode laser achieved the up-conversion (UC) emissions by involving two-photon absorptions in the visible region. The UC intensities and absorbed photon numbers were increased by increasing crosslinker content. The effects of change in the structure and morphology of the host polymer material on the color tuning, color coordinates and color quality parameters were observed.