LAUSR

In this work, we study the effect of the average shortest interaction distance between zinc oxide nanocrystals (ZnO-nc) and Europium (Eu3+) ions and between two Eu3+ ions in the energy transfer process between ZnO-nc and Eu3+ ions embedded in a SiO2 matrix fabricated by a combination of sol-gel and the sputtering technique. A detailed model to calculate the two interaction distances based on the ratio of Zn, Si and Eu3+ ions in the samples and using the density and molecular mass of ZnO and SiO2 is presented. Based on these calculations together with the photoluminescence emission from the samples, it is clearly shown that the energy transfer from ZnO-nc to Eu3+ ions is higher in samples with a shorter distance between the ZnO-nc and Eu3+ ions. The maximum red emission at 614 nm due to the efficient energy transfer from ZnO-nc to Eu3+ was found in the sample with 5.11 nm distance between the ZnO-nc and Eu3+ ions. However, the red emission from the Eu3+ ions does not increase as the distance between the ZnO-nc and Eu3+ ions is reduced below 5.11 nm by increasing the Eu3+ concentration. This is due to the Eu3+ ion concentration quenching effect, where the distances between the Eu3+ ions become shorter than 0.57 nm, resulting in a migration of energy between the Eu3+ ions that is non-radiatively dissipated. It is also shown that the energy transfer from ZnO-nc to Eu3+ ions occur mostly due to the radiative energy transfer process when the interaction distance between the ZnO-nc and Eu3+ ions is 6.53 nm or greater.