Fluorescence sensing of chloride ions in water based on wavelength shifts of hexane-dispersed CsPbBr3@silicone

Cesium lead halide (CsPbX3, X = Cl, Br, and I) perovskite nanocrystals (PNCs) have become attractive materials for fluorescence sensing in recent years due to their excellent photoluminescent properties. Because of their ionic properties, PNCs are unstable in polar solvents, making it difficult for them to detect substances in water. Some methods are useful, such as non-homogeneous phase sensing and wrapping an inert layer around the surface of PNCs. However, these methods reduce the sensing efficiency and hinder the interaction of PNCs with sensing substances. In addition, the encapsulated PNCs are more likely to undergo fluorescence quenching and decreased storage stability. In this work, (3-aminopropyl)trimethoxysilane (APTMS) was used to synthesize APTMS PNCs (A-PNCs) by a hot injection one-pot method, and they exhibited satisfactory fluorescence properties, stability, and monodispersity. By introducing ethanol to form a water–ethanol–hexane homogeneous system, the A-PNCs were able to increase their anion-exchange capacity after directly interacting with chloride ions (Cl−) in water. Based on the fluorescence wavelength variation of the A-PNCs, testing for Cl− in human sweat was accomplished in 1 minute, with the advantages of fast speed, high precision, and satisfactory stability. On this basis, the reacted A-PNCs were immobilized on the film with bright fluorescence and color stability, and their tricolor (RGB) values were extracted for visual sensing. Thus, well-dispersed A-PNCs in hexane can rapidly detect chloride ions in water, which will enhance the application of perovskite materials for sensing in polar solvents.