Plasmon-enhanced up-conversion luminescence and oxygen vacancy defect-induced yellow light in annealed Cu8S5@SiO2@Er2O3 nanocomposites

Abstract Monodispersed Cu8S5 nanoparticles were successfully synthesized by modified hot-injection method, and Cu8S5@SiO2@Er2O3 core-shell particles were designed and prepared for up-conversion luminescence. Under the excitation of 980 nm laser, the local surface plasmon resonance of Cu8S5 nanoparticles coupled with annealed Er2O3 crystals to enhance the up-conversion luminescence of Cu8S5@SiO2@Er2O3 nanocomposites in the green and red emission bands, compared with that of SiO2@Er2O3 particles. After addition of Cu8S5 nanoparticles, the local near-field enhancement of Cu8S5@SiO2@Er2O3 nanocomposites was ~36-folds stronger than that of annealed Er2O3 crystals under 980 nm incident light, indicating that Cu8S5 nanoparticles have excellent potential for enhancing the up-conversion luminescence of rare earth elements. The generation of yellow light at ~610 nm was attributed to oxygen vacancy defects in annealed Er2O3. The formation mechanism of oxygen vacancy defects in annealed Er2O3 was proposed and investigated. Furthermore, the mechanism of up-conversion luminescence of Cu8S5@SiO2@Er2O3 composites and the electronic band structure of annealed Er2O3 crystals were also discussed.