Surfactant effect on the upconversion emission and decay time of ZrO2:Yb-Er nanocrystals

Luminescent properties of doped ZrO2:Er3+ and codoped ZrO2:Yb3+–Er3+ nanocrystals with average size ∼54 nm were analyzed as a function of non-ionic surfactant (Pluronic F-127) concentration. Surfactant and non-surfactant samples were prepared by the sol–gel micelle process with hydrothermal aging and annealed at 1000 °C for 5 h. The introduction of the surfactant reduces the presence of impurities such as OH and CO2 on both samples, and increments the tetragonal phase for codoped nanocrystals. It induces an increment larger than 90% and 70% for doped and codoped, respectively, for an optimum molar ratio of 0.0082. The observed enlargement of fluorescence decay time is partly the result of the nanosize effect but is dominated by the reduction of impurities attached on the nanocrystalline surface.