Ultra-stable CsPbBr3@PbBrOH nanorods for fluorescence labeling application based on methylimidazole-assisted synthesis

The extension application of perovskites in aqueous media such as bioassays requires the development of a water-stable perovskite with a simple preparation process and low cost. However, the degradation of perovskites in aqueous solution is still a thorny problem. Here, we develop a methylimidazole-assisted two-step synthesis protocol to prepare CsPbBr3@PbBrOH nanorods with superior water stability and remarkable optical properties at room temperature. The synergy of 2-methylimidazole (2-MIM), an N-donor ligand, with water can not only facilitate CsPbBr3 formation and suppress CsPb2Br5 or Cs4PbBr6 formation, but also promote the formation of a PbBrOH shell capping CsPbBr3. 2-MIM is ionized into 2-MIM- in DMF and 2-MIM+ in water. They passivated the surface defects and changed the crystallization environment, leading to water-stable CsPbBr3@PbBrOH. The obtained CsPbBr3@PbBrOH nanorods can still maintain 91% PL intensity after being stored in water for more than 2 months. Furthermore, the CsPbBr3@PbBrOH nanorods show excellent stability in polar solvents, water, and phosphate buffer solution in a wide pH range, as well as better thermal and irradiation stability. In addition, the CsPbBr3@PbBrOH nanorods are further functionalized with polydopamine (PDA) for biomolecular immobilization and immunoassay studies. The resulting assay shows a detection limit of 0.003 ng mL-1 for IgG detection, illustrating important progress towards expanding fluorescence labeling application of perovskite nanomaterials for immunoassays.