Facile Uniaxial Electrospinning Strategy To Embed CsPbBr Nanocrystals with Enhanced Water/Thermal Stabilities for Reversible Fluorescence Switches.

All-inorganic halide perovskite nanocrystals with their fascinating optical properties have drawn increasing attention as promising nanoemitters. However, due to the intrinsic poor colloidal stability against the external environment, the practical applications are greatly limited. Herein, a facile and effective strategy for the in situ encapsulation of CsPbBr NCs into highly dense multichannel polyacrylonitrile (PAN) nanofibers via a uniaxial electrospinning strategy is presented. Such a facile uniaxial electrospinning strategy enables the in situ formation of CsPbBr NCs in PAN nanofibers without the introduction of stabilizers. Significantly, the obtained CsPbBr nanofibers not only display intense fluorescence with a high quantum yield (≈48%) but also present high stability when exposed to water and air owing to the peripheral protecting matrix of PAN. After immersing CsPbBr@PAN nanofiber films in water for 100 days, the quantum yield of CsPbBr@PAN nanofibers maintained 87.5% of the original value, which was much higher than that using CsPbBr NCs. Furthermore, based on the spectral overlap between the electrochromic material of ruthenium purple and fluorescence of CsPbBr@PAN nanofiber films with excellent water stability, a reversible fluorescence switch is constructed with good fatigue resistance, suggesting their promising applications.