Er3+–Yb3+ co-doped TiO2 nanoparticles embedded in amorphous matrix with strong up-conversion emissions

Er3+–Yb3+ co-doped TiO2 nanoparticles (NPs) embedded in amorphous matrix with varying Yb3+ concentrations are fabricated by a sol–gel method, afterwards parts of which are separated and surface modified in Mo(NO3)3 solution. Phase and structure analysis indicate that Er3+ and Yb3+ are incorporated into the TiO2 lattice successfully, a NP is single crystal that is surrounded by amorphous matrix. The visible up-conversion (UC) emissions change with Yb3+ concentration, surface modification enhances the UC emissions of all the samples, the most significant enhancement of the UC emission is the one with Yb3+ concentration of 10%. The different electronegativity of Mo6+ and Ti4+ are responsible for the enhancement of UC emission after surface modification, the detail is discussed.

► We fabricate Er3+–Yb3+ co-doped TiO2 nanoparticles (NPs) and parts are surface modified with Mo(NO3)3.
► Er3+ and Yb3+ are incorporated into the TiO2 lattice, a NP is single crystal surrounded by amorphous matrix.
► Visible up-conversion (UC) emissions change with Yb3+ concentration.
► Surface modification enhances the emission and results in a highest intensity with Yb3+ concentration of 10%.
► The different electronegativity of Mo6+ and Ti4+ are responsible for the enhancement of UC emission after modification.