Internal OH− defect-induced upconversion quenching in β-NaLuF4:Yb,Er microcrystals

Luminescence quenching effect of lanthanide-doped upconversion materials occurs with high probability even in larger-sized particles, but their main quenching pathway remains controversial. In this work, we investigate the influence of the surfactant and pH value on the luminescence properties of β-NaLuF 4 :Yb,Er microcrystals. A convincing evidence can be provided by the combination of X-ray diffraction (XRD), inductively coupled plasma (ICP) spectrometer, and Eu 3+ structural probe measurements that the major quenching pathway comes from the fast energy migration from the excited lanthanides to nearby OH − defects in the crystal lattice rather than surface quenching effect. Even at OH − -rich reactant condition, the upconversion luminescence intensity becomes more efficient by reduced internal quenching effects. Our findings provide a new and fundamental understanding of severe luminescence quenching effect at microscale, thus guiding the design and preparation of highly efficient upconversion materials.