Design of Pb1−xSrxF2 hollow crystals with gas–solution interfacial reactions

Abstract

Porous or hollow crystals have attracted considerable interest due to their unique properties and outstanding performance in various applications. In this study, hollow Pb_1−xSr_xF₂ crystals have been successfully fabricated via controlled precipitation–dissolution at the liquid–gas interface. As a result of the reaction on the surface of a solution mixture of Pb(CH₃COO)₂ and Sr(CH₃COO)₂ under the action of gaseous HF, a film of Pb_1−xSr_xF₂ crystals with a fluorite-type structure was formed. Placing the film on the water surface resulted in selective dissolution and formation of hollow crystals, associated with a relative increase in the overall Sr content in the Pb_1−xSr_xF₂ solid solution. By adjusting the crystallization conditions and the dissolution time it was possible to obtain hollow crystals with a wall thickness of 20–40 nm, membrane films with ordered through holes, or microstructures with flower-like morphology. The Gas–Solution Interface Technique used in this work can potentially be utilized to synthesize other metal fluorides with tunable porous morphology.