Simultaneous Cationic and Anionic Ligand Exchange For Colloidally Stable CsPbBr3 Nanocrystals
Simultaneous Cationic and Anionic Ligand Exchange For Colloidally Stable CsPbBr3 Nanocrystals
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DOI：
10.1021/acsenergylett.9b00140
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发表时间：
2019-04-01
影响因子：
22
通讯作者：
Manna, Liberato
中科院分区：
文献类型：
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作者：
Imran, Muhammad;Ijaz, Palvasha;Manna, Liberato
合成后配体交换已被广泛用于卤化铅钙钛矿（LHP）纳米晶体（NC），但起始NC的复杂配体壳组合物阻止了对交换过程的清楚理解，并且最终NC的表面化学仍然表征不佳。在这里，我们描述了一种配体交换策略，涉及在CsPbBr 3 NC的天然模型系统上置换阳离子和阴离子配体，该系统专门用Cs-油酸酯涂覆。这些配体与各种季铵溴化物（R4 NBr）交换，并且通过核磁共振（NMR）光谱分析确认完全交换。用无质子的R4 NBr置换天然Cs-油酸酯配体提供具有优异的胶体稳定性和接近统一的PLQY的NC，其在用极性溶剂洗涤后、在空气中储存超过3周后以及在将NC溶液加热至80 ° C后得以保存，如通过NMR分析所证实的。结果，连同密度泛函理论计算，表明，更高的稳定性的季铵封端的NC是不是由于一个更强的结合相互作用的表面，而是更弱的溶剂-配体相互作用的R4 NBr相比，Cs-油酸酯，驱动前者的表面的NC。
Postsynthesis ligand exchange has been employed extensively on lead halide perovskite (LHP) nanocrystals (NCs), but the complex ligand shell composition of the starting NCs prevented a clear understanding of the exchange process, and the surface chemistry of the final NCs remained poorly characterized. Here, we describe a ligand exchange strategy involving the displacement of both cationic and anionic ligands on native model systems of CsPbBr3 NCs, which are exclusively coated with Cs-oleate. These ligands are exchanged with various quaternary ammonium bromides (R4NBr), and complete exchange is confirmed by nuclear magnetic resonance (NMR) spectroscopy analysis. The displacement of the native Cs-oleate ligands with proton-free R4NBr delivers NCs with excellent colloidal stability and near-unity PLQY, which is preserved after washing with polar solvents, over 3 weeks of storage in air, and after heating a solution of NCs to 80 degrees C, as confirmed by NMR analysis. The results, together with density functional theory calculations, suggest that the higher stability of quaternary ammonium capped NCs is not due to a stronger binding interaction to the surface but rather to weaker solvent-ligand interactions of R4NBr compared to Cs-oleate, driving the former to the surface of the NCs.