Influence of Gd doping on the absolute quantum efficiency and lifetime of EuxGd1−x(TTA)3phens

Absolute quantum yield (Φ) is one of the most important parameters to evaluate the potential of novel materials. Lanthanide complexes EuxGd1−x(TTA)3phens are synthesized with the ratio of Gd3+ dopant concentration ranging from 10% to 90% to improve the absolute quantum yield. EuxGd1−x(TTA)3phens possess similar infrared and ultraviolet spectra, showing that they have similar molecular structures. The absolute emission quantum yields of EuxGd1−x(TTA)3phens are determined using a fluoromax-4 spectrofluorometer equipped with an integrating sphere. The fluorescence lifetimes of the EuxGd1−x(TTA)3phens are measured in the same experiment. It was found that both absolute quantum yields and fluorescence lifetimes of EuxGd1−x(TTA)3phens are of quasi-periodic variation with the change of the Gd3+ dopant concentrations. The absolute quantum efficiency and fluorescence lifetime vary with respect to the Gd content in an opposite fashion, indicating that the rate of energy absorption by the EuxGd1−x(TTA)3phens and the conversion to light energy is critical for the absolute quantum efficiency. The radiative rate constant Kr and non-radiative rate constant Knr are calculated. The dependence of Kr and Knr on the Gd3+ dopant concentrations is very similar to that of absolute quantum efficiency. The radiation rate constant Kr and absolute quantum efficiency have a linear relationship.