Structural and photoluminescent analysis of novel Eu3+ and Dy3+ Co-doped ZnO nanoparticles by incorporation of Li+ and K+ ions

Abstract

In this study, we thoroughly investigate the structural and luminescent features of ZnO nanoparticles doped with Eu3+ and co-doped with Dy3+, exploring the impact of Li+ and K+ incorporation during the precipitation process. The synthesized nanoparticles were comprehensively characterized using X-ray diffraction (XRD), Fourier transmission infrared (FTIR), Energy dispersive spectroscopy (EDS), and photoluminescence (PL) techniques. The XRD analysis conclusively verified the presence of the hexagonal wurtzite phase in the ZnO nanoparticles. PL assessment of undoped ZnO revealed a well-defined and narrow exciton band peaked at 390 nm, accompanied by a broad defect-related band spanning from 450 nm to 750 nm. For ZnO:Eu3+ phosphors, distinct emission peaks emerged at 590 nm, 618 nm, and 696 nm when excited at 349 nm, corresponding to the 4f electron transition inherent to Eu3+ ions. The optimized doping level for the ZnO:xEu3+ sample was determined to be 7 wt%. The mechanism of concentration quenching was identified as dipole-quadrupole interaction. Co-doping with Li+ as a charge compensator resulted in a threefold enhancement in the luminescence intensity of the red-emitting ZnO: Eu3+, Li+. As the temperature decreases, the luminescence intensity of Eu3+ transitions in ZnO:7 wt% Eu3+ diminishes due to less efficient energy transfer among Eu3+ ions, while the intrinsic broad band from ZnO fades away, emphasizing the temperature-sensitive nature of the material. The addition of Dy3+ as a co-dopant to ZnO: Eu3+ induces a counterintuitive effect, where an increase in Dy3+ concentration unexpectedly results in a decrease in Eu3+ emission peak intensity. This unconventional behavior highlights a complex interplay between Dy3+ and Eu3+ ions, suggesting the influence of spatial factors, competing processes, and potential dopant ag gregation within the ZnO lattice. The CIE analysis conducted on ZnO:Eu3+, Dy3+, and Li+ nanoparticles demonstrated precise control over the emitted light, enabling the fine-tuning of their optical properties for ap plications in displays.