Water soluble cubic K2NaScF6nanocrystals: crystal structure evolution and luminescence properties

Abstract

Studies on Sc3+-based nanomaterials have been reported in recent years. However, most of the as-prepared nanomaterials are hydrophobic, thus complicated surface encapsulation renders them hydrophilic for biological applications. In our work, we used water soluble polyvinylpyrrolidone (PVP) as a chelating agent and a classic hydrothermal method to prepare water soluble cubic K2NaScF6 nanocrystals (NCs) for the first time. Different ratios of NH4F/RE (3, 4, 5, 6) have been studied in the crystalline phase transformation from KSc2F7 to K2NaScF6 NCs. When the ratio is over 6, an unusual hexagonal NaYbF4 phase separation phenomenon can be observed. In addition, Yb3+/Er3+ ion pairs have been doped into the K2NaScF6 NCs to verify that they are better up-conversion luminescence matrix materials than KSc2F7 NCs.