Synergistic ligand engineering enables atomically layered Quasi-2D perovskite nanosheets with tailorable optical emission and enhanced stability

Nanosheets with 1–8 atomic layer thickness are realized by dual-ligand engineering. • Tunable emission from 527 to 754 nm achieved through quantum confinement effects. • CMAI-capped nanosheets exhibit high stability under laser irradiation and in water. • Ammonium establishes stronger bonding on surface and blocks vertical crystal growth. • This method overcomes phase separation and holds promise for optoelectronic devices. Achieving tunable emission in single-halide perovskite nanocrystals via size control remains challenging, while mixed-halide alternatives suffer from inherent instability. Here, we establish a synergistic ligand engineering strategy for the controlled synthesis of atomically layered quasi-2D perovskite nanosheets in pure-iodide systems. By systematically comparing the roles of amine (OLA, PEA) and ammonium (PEAI, CMAI) ligands, we demonstrate that PEAI and CMAI terminate vertical growth via strong surface binding from the –NH 3 + group, while OLA prevents nanocrystal aggregation, which is a complementary function essential for achieving well-dispersed, ultrathin nanosheets. Through combined ligand and solvent engineering, we achieve precise thickness control from n = 1 to n = 8 with tunable emission across 527–729 nm, a broader range than previously reported for single-halide colloidal perovskite nanosheets. Notably, CMAI-passivated n = 3 nanosheets exhibit superior stability, retaining 71% of initial PL in a 1:2 (v/v) aqueous environment after 35 min and 38.1% after 15 min of intense 405 nm laser irradiation (49 mW), significantly outperforming both OLA- and PEAI-based analogues. This work establishes a dual-ligand synergistic framework that overcomes the long-standing challenges of thickness control and spectral tunability in single-halide perovskite nanosystems, providing a generalizable strategy for designing stable, high-performance perovskite optoelectronic materials. © 2012 Published by Elsevier Ltd. Selection and/or peer-review under responsibility of Global Science and Technology Forum Pte Ltd. Download: Download high-res image (336KB) Download: Download full-size image