Aspect Ratio-Tunable CsPbBr₃ Nanorods from Cs₄PbBr₆ at the Oil–Water Interface with Enhanced Stability via Ligand Treatment

One-dimensional CsPbBr 3 nanocrystals (NCs) possess significant potential in laser and photodetection fields due to their longer carrier lifetimes, more efficient carrier transport, and anisotropic optical properties. In recent years, Cs 4 PbBr 6 has been employed to synthesize highly luminescent one-dimensional CsPbBr 3 NCs; however, the poor stability of CsPbBr 3 NCs produced by this method has limited their practical applications. In this study, CsPbBr 3 nanorods (NRs) were prepared by removing CsBr from Cs 4 PbBr 6 using a postsynthetic method. Water was added dropwise to Cs 4 PbBr 6 NCs dispersed in a nonpolar solvent. Due to the high solubility of CsBr in water, the Cs 4 PbBr 6 NCs rapidly converted into CsPbBr 3 NCs. At this point, the addition of water-induced dipole–dipole interactions within the system drives the self-assembly of CsPbBr 3 NCs into NRs. As the amount of water increased, the local concentration of CsPbBr 3 NCs also rose, raising the probability of collisions between CsPbBr 3 NCs and resulting in the formation of longer NRs. Subsequently, benzoic acid was introduced to replace the ligands removed along with CsBr. Due to the surface passivation effect of benzoic acid, the stability and photoluminescence performance of the CsPbBr 3 NRs were significantly enhanced. The resulting CsPbBr 3 NRs exhibited a fluorescence lifetime of 45.97 ns and achieved a high photoluminescence quantum yield (PLQY) of 94.2%. Stability tests showed that the ligand-passivated CsPbBr 3 NRs retained 65% of their initial photoluminescence intensity after one month of storage in an open atmospheric environment.