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

One-dimensional CsPbBr3 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, Cs4PbBr6 has been employed to synthesize highly luminescent one-dimensional CsPbBr3 NCs; however, the poor stability of CsPbBr3 NCs produced by this method has limited their practical applications. In this study, CsPbBr3 nanorods (NRs) were prepared by removing CsBr from Cs4PbBr6 using a postsynthetic method. Water was added dropwise to Cs4PbBr6 NCs dispersed in a nonpolar solvent. Due to the high solubility of CsBr in water, the Cs4PbBr6 NCs rapidly converted into CsPbBr3 NCs. At this point, the addition of water-induced dipole–dipole interactions within the system drives the self-assembly of CsPbBr3 NCs into NRs. As the amount of water increased, the local concentration of CsPbBr3 NCs also rose, raising the probability of collisions between CsPbBr3 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 CsPbBr3 NRs were significantly enhanced. The resulting CsPbBr3 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 CsPbBr3 NRs retained 65% of their initial photoluminescence intensity after one month of storage in an open atmospheric environment.