Emission-Decay Curves, Energy-Transfer and Effective-Refractive Index in Gd2O3:Eu3+ Nanorods

Cubic Gd2O3:Eu3+ (0.30, 1.01, 2.78, and 4.60 mol %) nanorods with an average diameter of ca. 14 nm were synthesized at ambient pressure and mild temperature (70 degrees C), using a simple and cost-effective wet-chemical route. The emission-decay curves of the D-5(1) and D-5(0) levels, hereafter referred to as D-5(1) (C-2) and D-5(0)(C-2), were investigated. Although the decay time of the D-5(0) level of the Eu3+ ions residing in the C-2 site of cubic Gd2O3:Eu3+ nanostructures were previously reported, little is known about the rise time component in the D-5(0) emission-decay curve and the energy-transfer pathways responsible for it. The D-5(0)(C-2) rise time and the D-5(1)(C-2) decay time exhibit similar and strong dependence on the Eu3+ concentration and temperature. The D-5(1)(C-2) decay time matches well the rise time extracted from the rising component of the D-5(0)(C-2) emission-decay curve. The decay time of the D-5(0)(C-2) level (ranging from 1.4 to 2.1 ms, depending on the filing factor of the nanorods) is longer than that of the bulk counterpart mainly due to the reduction in the size of the nanorods, which introduces an effective-refractive index smaller than the refractive index of Gd2O3.