Peptide-Passivated Lead Halide Perovskite Nanocrystals Based on Synergistic Effect between Amino and Carboxylic Functional Groups

A new strategy has been developed using peptides with amino and carboxylic functional groups as passivating ligands to produce methyl ammonium lead bromide (CH3NH3PbBr3) perovskite nanocrystals (PNCs) with excellent optical properties. The well-passivated PNCs can only be obtained when both amino and carboxylic groups are involved, and this is attributed to the protonation reaction between. NH2 and. COOH that is essential for successful passivation of the PNCs. To better understand this synergistic effect, peptides with different lengths have been studied and compared. Due to the polar nature of peptides, peptide-passivated PNCs (denoted as PNCspeptide) aggregate and precipitate from nonpolar toluene solvent, resulting in a high product yield (approximate to 44%). Furthermore, the size of PNCspeptide can be varied from approximate to 3.9 to 8.6 nm by adjusting the concentration of the peptide, resulting in tunable optical properties due to the quantum confinement effect. In addition, CsPbBr3 PNCs are also synthesized with peptides as capping ligands, further demonstrating the generality and versatility of this strategy, which is important for generating high quality PNCs for photonics applications including light-emitting diodes, optical sensing, and imaging.