Role of Inert Shell in improving Energy Utilization in Lanthanide-doped Upconversion Nanoparticles
Inert shell coating is a well-known efficient appoach for enhancing both emission intensity and luminescence quantum yield of upconversion nanoparticles. In this work, the role of inert shell on the photon energy collection and energy transfer behavior inside upconversion nanoparticles is carefully studied. Our experimental results indicate that due to the valid energy trapping by the shell, energy clustering effect is formed among the Yb3+ ions in the core. Such an effect reduces the total absorption and enhances the upconversion emission, especially the emission from higher lying level of lanthanide emitters. Moreover, the morphologies of inert shell, which could be controlled during our synthesis, are deemed to be critical on the formation of energy clustering.