Design of Pb 1− x Sr x F 2 hollow crystals with gas–solution interfacial reactions

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− x Sr x F 2 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(CH 3 COO) 2 and Sr(CH 3 COO) 2 under the action of gaseous HF, a film of Pb 1− x Sr x F 2 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− x Sr x F 2 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.