Simultaneous size and luminescence control of KZnF₃:Yb³⁺/Er³⁺ nanoparticles by incorporation of Mn²⁺

A strategy is demonstrated for simultaneous size and color tuning of KZnF₃:Yb³⁺/Er³⁺ nanocrystals through transition metal Mn²⁺ doping. The experimental results indicate that the introduction of Mn²⁺ into the KZnF₃:Yb³⁺/Er³⁺ reaction system facilitates the decrease of the crystal size. Moreover, in the case of a high concentration of Mn²⁺ doping, the downshifting (DS) and upconversion (UC) luminescence all show a single red band emission. In this work, we mainly investigate the DS and UC energy transfer process among Mn²⁺/Yb³⁺/Er³⁺ in KZnF₃ nanocrystals by the detection and analysis of the absorption, excitation, emission, and transient fluorescence spectra. The results show that both Mn²⁺ and Yb³⁺ ions can decrease the green emission while improving the red luminescence of Er³⁺. This DS and UC single red color tuning is significant for the application of nanoparticles in light conversion, biological labeling, or plant photosynthesis.