Dual-Mode Luminescence from Polyacrylonitrile-Stabilized CsPbX₃ (X = Br and I) Nanocrystals Triggered by NaYF₄:Yb/Ln (Ln = Er and Tm) Upconversion Nanoparticles: Implications for Anticounterfeiting and Optical Thermometry

Owing to their excellent photoelectric and optical properties, lead halide perovskite quantum dots (PeQDs) have attracted great attention and have broad applications in various fields. However, the shortcomings of poor stability and short-wavelength (ultraviolet/visible) excitation restrict their practical applications. Herein, to address the above issues, we report a polyacrylonitrile-based composite film containing CsPbX 3 (X = Br and I) PeQDs and β-NaYF 4:Yb/Ln (Ln = Tm and Er) upconversion nanoparticles (UCNPs) via an electrospinning strategy. Interestingly, all-inorganic CsPbX 3 PeQDs are synthesized through an in situ growth process in polyacrylonitrile nanofibers, which provide a polymer matrix for the protection of PeQDs against decomposition under the effect of an external environment. Upon 980 nm laser irradiation, lanthanide-sensitized UC luminescence of stable CsPbX 3 can be realized through radiative energy transfer from Tm 3+ /Er 3+ ions to PeQDs. Consequently, dual-mode luminescence, including downshifting and UC with color-tunable outputs, can be observed from PeQDs under dual-wavelength excitation (UV and NIR). Benefiting from the special luminescent feathers (temperature-sensitive UC and dual-mode luminescence), the as-obtained composite nanofibers exhibit great potential in high-level anticounterfeiting and accurate noncontact thermometry.