Anion Exchanges of Water-Stable Perovskite Nanocrystals in the Pure Water Phase and Applications in Detecting Halide Ions via a Smartphone-Based Sensing Platform

PNCs by a simple "oil-solid-water" phase transition. The W-PNCs without being encapsulated with compact polymers or inorganic materials can sensitively and stably sense targets in the pure water phase via direct chemical reactions. For the first time, ion exchanges between PNCs and halide ions and their effects on the fluorescence wavelength of PNCs were investigated in the pure water phase, on the basis of which a new, visualized, selective, and sensitive smartphone-based sensing platform for halide ions has been established by the integration of the conveniently prepared W-PNC nanoprobe and the portable mobile phone. It is envisioned that the uncoated but extremely water-stable and highly fluorescent W-PNCs have promising applications in chemical sensing, biosensing, and bioimaging of targets in aqueous medium.