Synthesis of Ultrathin Few-Layer 2D Nanoplates of Halide Perovskite Cs 3 Bi 2 I 9 and Single-Nanoplate Super-Resolved Fluorescence Microscopy

The discovery of new two-dimensional (2D) perovskite halides has created sensation recently because of their structural diversity and intriguing optical properties. The toxicity of Pb-based perovskite halides led to the development of Pb-free halides. Herein, we have demonstrated a one-pot solution-based synthesis of 2D ultrathin (∼1.78 nm) few-layer (2-4 layers) nanoplates (300-600 nm lateral dimension), nanosheets (0.6-1.5 μm), and nanocrystals of layered Cs Bi I by varying the reaction temperature from 110 to 180 °C. We have established a mechanistic pathway for the variation of morphology of Cs Bi I with temperature in the presence of organic capping ligands. Further, we have synthesized the bulk powder of Cs Bi I by mechanochemical synthesis and liquid-assisted grinding and crystalline ingot by vacuum-sealed tube melting. 2D nanoplates and bulk Cs Bi I demonstrate optical absorption edge along with excitonic transition. Photoluminescence properties of individual nanoplates were studied by super-resolution fluorescence imaging, which indicated the blinking behavior down to the level of an individual Cs Bi I nanoplate along with its emission at the far-red region and high photostability.