Hydrochromic CsPbBr3Nanocrystals for Anti-Counterfeiting

Hydrochromic materials that can reversibly change color upon water treatment have attracted much attention owing to their potential applications in diverse fields. Herein, for the first time, we report that space-confined CsPbBr(3)nanocrystals (NCs) are hydrochromic. When CsPbBr3NCs are loaded into a porous matrix, reversible transition between luminescent CsPbBr(3)and non-luminescent CsPb(2)Br(5)can be achieved upon the exposure/removal of water. The potential applications of hydrochromic CsPbBr3NCs in anti-counterfeiting are demonstrated by using CsPbBr3NCs@mesoporous silica nanospheres (around 100 nm) as the starting material. Owing to the small particle size and negatively charged surface, the as-prepared particles can be laser-jet printed with high precision and high speed. We demonstrate the excellent stability over repeated transformation cycles without color fade. This new discovery may not only deepen the understanding of CsPbX3, but also open a new way to design CsPbX(3)materials for new applications.