Highly Luminescent and Multifunctional Zero-Dimensional Cesium Lanthanide Chloride (Cs3LnCl6) Colloidal Nanocrystals

Abstract

Herein, the synthesis of novel, highly luminescent, and nearly monodisperse zero-dimensional (0D) cesium lanthanide chloride (Cs3LnCl6; Ln = Y, Ce, Gd, Er, Tm, Yb) colloidal nanocrystals (NCs) is reported for the first time. The Cs3LnCl6 NCs are synthesized using a heating-up method and exhibit highly uniform size and shape. The monoclinic-phase Cs3LnCl6 NCs contain completely isolated [LnCl6]3− octahedral units, resulting in 0D ternary metal halide structures. Therefore, these NCs exhibit deep-blue photoluminescence under ultraviolet excitation, and this photoluminescence can be tuned by changing the lanthanide cations within the [LnCl6]3− octahedral units. High photoluminescence quantum yields of up to 60% and 90% are observed for the Cs3YbCl6 and Cs3YCl6 NCs, respectively, at room temperature and under ambient conditions. The Cs3LnCl6 NCs exhibit characteristic optical and magnetic properties owing to the f-orbitals of the lanthanide elements. For example, near-infrared-to-visible upconversion luminescence appears when Cs3LnCl6 NCs are doped with Er3+ and Yb3+ ions. In addition, the Cs3GdCl6 NCs demonstrate paramagnetic properties owing to the unpaired electrons within the f-orbitals of the trivalent gadolinium ions. This study provides guidance for the rational design and synthesis of novel lanthanide-based 0D metal halide NCs, which can potentially be used as highly efficient, multifunctional NC emitters. © 2022 Wiley-VCH GmbH