Study of energy transfer mechanism from ZnO nanocrystals to Eu3+ ions

Abstract

In this work, we investigate the efficient energy transfer occurring between ZnO nanocrystals (ZnO-nc) and europium (Eu3+) ions embedded in a SiO2 matrix prepared using the sol-gel technique. We show that a strong red emission was observed at 614 nm when the ZnO-nc were excited using a continuous optical excitation at 325 nm. This emission is due to the radiative 5D0 → 7F2 de-excitation of the Eu3+ ions and has been conclusively shown to be due to the energy transfer from the excited ZnO-nc to the Eu3+ ions. The photoluminescence excitation spectra are also examined in this work to confirm the energy transfer from ZnO-nc to the Eu3+ ions. Furthermore, we study various de-excitation processes from the excited ZnO-nc and their contribution to the energy transfer to Eu3+ ions. We also report the optimum fabrication process for maximum red emission at 614 nm from the samples where we show a strong dependence on the annealing temperature and the Eu3+ concentration in the sample. The maximum red emission is observed with 12 mol% Eu3+ annealed at 450 °C. This work provides a better understanding of the energy transfer mechanism from ZnO-nc to Eu3+ ions and is important for applications in photonics, especially for light emitting devices.

Bright red luminescence emission of macroporous honeycomb-like Eu3+ ion-doped ZnO nanoparticles developed by gel-combustion technique

“…Examples of these methods are co-precipitation, sol-gel, combustion, solvothermal, microwave, etc. [21,[26][27][28][29]. An alternative is a gel-combustion reaction technique, as it does not involve intermediate composition or steps of calcinations, to make a synthesis of these Eu-doped ZnO compounds quick and cheap [30][31][32].…”

Tin Dioxide Nanocrystals as an Effective Sensitizer for Erbium Ions in Er-Doped SnO2Systems for Photonic Applications

“…Hence the emission at 454 nm is the result of recombination of electron from conduction band to these acceptor centres. The intensity of this emission increases with doping contents and this band shifts to shorter wavelength due to the fact that an increasing of doping concentration not only induces the more acceptor centres but also shifts the acceptor levels nearer to the valence band [15]. The disappearance of characteristic band at 620 nm of SnO 2 in all spectra of doped samples proves that the energy is efficiently transferred from defect levels of SnO 2 nanocrystals to Er 3+ ions.…”

Effect of CdS nanocrystals on the photoluminescence of Eu3+-doped silicophosphate sol gel glass

“…At these wavelengths, Eu 3+ ions have negligible absorption. 37 Under an excitation at 375 nm, the PL spectra of the sample doped only with CdS exhibits a narrow emission band in the UV region centered at 406 nm, which is Stokes-shied from absorption onset of CdS nanocrystals together with a weak and large band peaking at 647 nm. These two emissions are ascribed respectively to shallow traps (ST) and deep traps (DT) states in the bandgap of CdS nanocrystals.…”

“…Similar behavior was observed in SiO 2 gel doped with Eu 3+ and ZnO nanocrystals. 43 Additionally, the fact that no luminescence from CdS nanocrystals was observed under 355 nm excitation wavelength indicates that energy transfer from a nanocrystal to Eu 3+ is so fast. Indeed, when CdS are coupled to Eu 3+ , any generated exciton will immediately recombine non-radiatively by exciting Eu 3+ ions.…”