Synthesis Protocols for δ-Doped NaYF4:Yb,Er

A novel structure, δ-doped NaYF4:Yb,Er, has been proposed for significantly enhancing the fluorescence efficiency of up-conversion phosphors. Theoretical calculations indicate that these new δ-doped NaYF4:Yb,Er structures will suppress the Yb3+-defect energy transfer rate while effectively preserving or enhancing the Yb3+ to Er3+ energy transfer. To investigate this effect δ-doped NaYF4:Yb,Er nanocrystals have been synthesized according to the designed structure model and the prepared samples characterized physically by transmission electron microscopy (TEM), high-resolution TEM (HRTEM), X-ray diffraction (XRD), energy dispersed spectroscopy (EDS) and optically by photoluminescence (PL) spectroscopy. Well-defined doping geometries of the order of 3–5 nm in width were clearly identified, both spatially and chemically. The up-converted emission spectra data were consistent with the theoretical predictions.