Design of Pb_1-xSr_xF₂ 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 Pb1-xSrxF2 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 Pb1-xSrxF2 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 Pb1-xSrxF2 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.