Amino acid assisted aqueous synthesis of highly stable CsPbBr₃ nanocrystals for cell imaging

Lead halide perovskite nanocrystals (NCs) exhibit excellent optoelectronic performance and have drawn great interests in the fields of biological imaging and sensing. However, the poor stability of CsPbX₃ (X = Cl, Br, I) in water is still a challenge to hinder their practical applications. In this work, a facile strategy has been developed for aqueous synthesis of CsPbX₃ nanocrystals, in which L-glutamic acid (L-Glu) has been used to replace oleic acid in the synthetic process. Benefiting from the synergic effects of L-Glu and oleylamine (OAm), CsPbBr₃ nanocrystals (L-Glu/OAm-CsPbBr₃ NCs) with high water stability have been directly prepared under a mild condition at room temperature in water, facilitated by the process of crystal phase transformation from Cs₄PbBr₆ to CsPbBr₃. L-Glu/OAm-CsPbBr₃ NCs exhibit a high quantum yield of 85% and a narrow full width at half maximum of 16 nm, demonstrating their efficient luminescence in water. Typically, L-Glu on the surface have contributed greatly to an acidic environment and passivation of surface defects, improving the water stability and dispersibility of CsPbBr₃ nanocrystals. Moreover, L-Glu/OAm-CsPbBr₃ NCs exhibit great biocompatibility due to the presence of L-Glu, resulting in their good performance for HeLa cell imaging. Thus, we propose a facile and effective method to prepare CsPbBr₃ nanocrystals with excellent water stability by using L-Glu and OAm as cooperated ligands and expand their application in cell imaging.