Scharf Einav, Krieg Franziska, Elimelech Orian, Oded Meirav, Levi Adar, Dirin Dmitry N, Kovalenko Maksym V, Banin Uri
The Institute of Chemistry and the Center for Nanoscience and Nanotechnology, The Hebrew University of Jerusalem, Jerusalem 91904, Israel.
Institute of Inorganic Chemistry, Department of Chemistry and Applied Bioscience, ETH Zürich, Vladimir Prelog Weg 1, Zürich CH-8093, Switzerland.
Nano Lett. 2022 Jun 8;22(11):4340-4346. doi: 10.1021/acs.nanolett.2c00611. Epub 2022 May 23.
The soft lattice of lead-halide perovskite nanocrystals (NCs) allows tuning their optoelectronic characteristics via anion exchange by introducing halide salts to a solution of perovskite NCs. Similarly, cross-anion exchange can occur upon mixing NCs of different perovskite halides. This process, though, is detrimental for applications requiring perovskite NCs with different halides in close proximity. We study the effects of various stabilizing surface ligands on the kinetics of the cross-anion exchange reaction, comparing zwitterionic and ionic ligands. The kinetic analysis, inspired by the "cage effect" for solution reactions, showcases a mechanism where the surface capping ligands act as anion carriers that diffuse to the NC surface, forming an encounter pair enclosed by the surrounding ligands that initiates the anion exchange process. The zwitterionic ligands considerably slow down the cross-anion exchange process, and while they do not fully inhibit it, they confer improved stability alongside enhanced solubility relevant for various applications.
卤化铅钙钛矿纳米晶体（NCs）的软晶格允许通过将卤化物盐引入钙钛矿NCs溶液中进行阴离子交换来调节其光电特性。同样，在混合不同卤化钙钛矿的NCs时会发生交叉阴离子交换。然而，对于需要不同卤化物的钙钛矿NCs紧密相邻的应用来说，这个过程是有害的。我们研究了各种稳定表面配体对交叉阴离子交换反应动力学的影响，比较了两性离子配体和离子配体。受溶液反应“笼效应”启发的动力学分析展示了一种机制，其中表面封端配体充当阴离子载体，扩散到NC表面，形成由周围配体包围的遭遇对，从而启动阴离子交换过程。两性离子配体大大减缓了交叉阴离子交换过程，虽然它们没有完全抑制它，但它们赋予了更好的稳定性以及与各种应用相关的增强溶解性。
