Fluorescence wavelength shifts combined with light scattering for ratiometric sensing of chloride in the serum based on CsPbBr@SiO perovskite nanocrystal composite halide exchanges.

A traditional fluorescence-scattering intensity based ratiometric sensing system utilizes both inherent scattering and fluorescence intensity and has drawn extensive attention owing to its simplicity and self-calibration properties. In this work, we propose a novel ratiometric fluorescence sensing system that combines a fluorescence wavelength shift and scattering in a single window, using second-order scattering (SOS) as the representative scattering signal based on the halide exchange of CsPbBr@SiO perovskite nanocrystal composites. We observe a fast halide exchange within 10 seconds, resulting in an identifiable fluorescence wavelength blue shift, while the scattering wavelength remains relatively constant for self-correction. This system could be applied for ratiometric sensing of Cl in the serum without any sample treatment. The established wavelength-based ratiometric system demonstrates high reliability and reproducibility, paving a new way for fluorescence sensing.