Amino Acid-Driven Dimensional Reduction of CsPbBr3 Nanocrystals

Inspired by biomineralization, the recent incorporation of organic molecules into inorganic lattices shows interesting optical properties and tunability. We functionalize all inorganic CsPbBr₃ perovskite nanocrystals (PNCs) with amino acid (AA) cysteine using the water-hexane interfacial approach. Along with the AA cysteine, we added AuBr₃ salt into the aqueous phase, leading to the formation of a Au-cysteine thiolate complex to activate the aqueous to nonaqueous phase transportation of the AA via a molecular shuttle, oleylamine. The interaction between CsPbBr₃ PNCs and the Au-cysteine thiolate complex is probed using optical spectroscopy, which reveals dimensional reduction of the parent PNCs to form CsPbBr₃ nanoplatelets (NPls) and subsequent phase transformation to CsPb₂Br₅ NPls. X-ray diffraction, X-ray photoelectron spectroscopy, and high-resolution transmission electron microscopy conclusively support the above chemical transformation reaction via interfacial chemistry. We propose a mechanistic insight into the dimensional growth in one direction in the presence of AAs via preferential ligand binding to specific facets, leading to transformation from 3D cubes to 2D NPls, while, presumably, the phase transformation occurs via the CsBr stripping mechanism upon prolonged interaction with water. Since AAs are building blocks for several redox-active complex biological moieties, including proteins, investigation of the interaction of AAs with PNCs may be advantageous since the latter can act as a fluorescent probe for bioimaging application.