Preparation And Photoluminescence Properties Of Au/Ln³⁺ Co-doped Gd₂（MoO₄）₃ Composite Thin Film

Rare earth doped luminescence materials have attracted considerable attention due to their potential applications in biomedicine, white light display and solid laser.With the rapid advancement of nanomaterials and laser technology, the research of rare earth doped luminescence materials has been applied to bio-imaging,bio-thermometry and bio-therapy. It is of paramount importance to develop novel rare earth doped luminescence materials with simpler synthesis procedure, higher luminescence efficiency and good thermometry sensitivity. In this thesis, we investigated the methods to enhance the up-conversion photoluminescence intensity of rare earth co-doped Gd2(Mo O4)3 thin film. The main work is as follows:We prepared the Gd2(Mo O4)3 composite thin films composing three layers of Gd2(Mo O4)3:1Er3+/Yb3+and different layers of Gd2(Mo O4)3:1Tm3+/12Yb3+using spin-coating method. And the effect of Gd2(Mo O4)3:1Tm3+/12Yb3+ layers on the up-conversion emission intensity was studied. The experimental results were analyzed using steady-state rate equations based on energy level. And the mechanism of up-conversion emission enhancement was evaluated.We prepared a composite system consisting of Gd2(Mo O4)3 thin film and Au nanoparticles using electrostatic layer-by-layer technique. The effect of Au nanoparticles on the green fluorescence intensity of Gd2(Mo O4)3 thin films was investigated. Gold island was observed in the AFM and SEM images of the Gd2(Mo O4)3 composite thin films and the localized surface plasmon resonance enhanced up-conversion photoluminescence was verified though our experiments.Two mechanisms(radiation rate increase and excitation efficiency) were used to explain the observed results. The theoretical prediction was verified through experiments about fluorescence lifetime and the dependences of the green emissions of Gd2(Mo O4)3 composite thin films upon the pump power.We studied the contactless temperature measurement with Gd2(Mo O4)3composite thin films using both fluorescence intensity ratio and fluorescence lifetime experiments. Th results demonstrate the effect of temperature and composition on the temperature measurement sensitivity.The study of fluorescence lifetime nano-thermometry found that the relationship between fluorescence life and temperature of the composite Gd2(Mo O4)3 composite thin film is exponental.Comparing the two fluorescence nano-thermometry methods, we found that between300 and 500 K, the sensitivity of fluorescence intensity ratio is higher thanfluorescence lifetime. However, the fluorescence lifetime is thought to have higher sensitivity when the temperature is before 300 k.