Phase segregation enabled scandium fluoride–lanthanide fluoride Janus nanoparticles

Abstract

Janus particles, in which two distinct compositions are integrated, have attracted considerable interest for their potential multi-functionalities and synergistic effects. Although seed-mediated growth appears to be a suitable strategy that meets the stringent specifications for obtaining Janus particles, it is inapplicable to guide the growth of two crystalline components with different crystal structures. Herein, the formation of Janus particles via phase segregation is proposed. As proof-of-concept, promising photon conversion materials, ScF₃ and lanthanide (Ln) fluorides, with great differences in structure, were chosen to build a series of Janus particles. Interestingly, using heavy (Lu, Yb, Dy and Tb) and light (Pr, Nd, Sm, Eu and Gd) lanthanides, ScF₃–LiLnF₄ and ScF₃–LnF₃ were formed, respectively. Time-dependent reaction studies indicate that phase segregation paves the way for the formation of these Janus nanoparticles (NPs), and this speculation is further confirmed by in situ transmission electron microscopy observations. These investigations provide new insights for the synthesis of heterostructured materials.