Water-Stable CsPbBr<sub>3</sub>/Cs<sub>4</sub>PbBr<sub>6</sub> Nanocrystals with a Mixed Fluoropolymer Shell for Optical Temperature Sensing
Zhangdi Lu, Yanxiu Li, Yilei Xue, Wentao Zhou, Steevanson Bayer, Ian D. Williams, Andrey L. Rogach, Stefan Nagl
Abstract
Hyflon AD 60 and dodecafluoroheptylpropyl-trihydroxysilane are employed as ligands to synthesize water-stable core–shell CsPbBr3/Cs4PbBr6 nanocrystals in aqueous dispersion, with a high photoluminescence quantum yield of 73% and a long luminescence lifetime of 207 ns. The obtained CsPbBr3/Cs4PbBr6 NCs passivated by fluorinated ligands are well dispersed in water with a mean diameter of 21.9 nm. The whole synthesis can be performed at room temperature on air; fluorinated chains of the Hyflon ligand strongly bond on the surface of CsPbBr3/Cs4PbBr6 nanocrystals and further link amphiphilic fluorinated silanol molecules through hydrophobic interactions. CsPbBr3/Cs4PbBr6 nanocrystals are stable in the aqueous phase for at least 1 month, maintaining strong photoluminescence (68% of initial intensity after 31 days) because of surface passivation. They are used as a luminescent temperature probe in water with a sensitivity of its intensity equal to 1.01% K–1 and good thermal stability for 10 heating–cooling cycles between 278 and 328 K.