CsPbBr3 nanocrystals as luminescent probe for in situ detection of chloride and iodide ions in water

All-inorganic cesium lead halide (CsPbX3, X = Cl, Br, I) Perovskite nanocrystals (PNCs) are promising new luminescent nanomaterials. However, PNCs are less stable in ambient environments. The fully encapsulated protective layer greatly improves the stability but limits direct contact with substances in the environment, leading to great challenges for luminescent probe applications. We developed a simple approach that hydrogen-bond cross-linking reinforcement to deal with the challenge. Target ACD-PNCs, which use β-CD (β- cyclodextrin) as the ligand with addition of Arginine, were prepared by adding arginine to an ethanol solution of CsPbBr3 stabilized by β-CD. The ACD-PNCs have a luminescence efficiency of 82% and show good stability in external environments including high temperature, humidity, and ethanol–water mixed solvents. It is worth noting that neither arginine nor cyclodextrin alone could have allowed PNCs to perform so well. More interestingly, the hydrogen-bond network permits the passage of chloride and iodide ions. Through the response of luminescence color upon ion exchange, the ACD-PNCs can detect aqueous Cl− and I− with good selectivity and sensitivity. Under optimum conditions, the LOD and % RSD were determined as 3.2*10−6 M and 5.7% for Cl−, 9.0*10−6 M and 6.7% for I−, respectively. To identify halide ions in samples like sweat, saliva, and kelp, conveniently prepared ACD-PNCs test strips were employed. This work provides insights into the design and development of perovskite probes capable of detection in aqueous solution, and also demonstrates the importance of rapidly forming hydrogen-bonding networks when studying such sensing systems.