Mishra Aditya, Hope Michael A, Stevanato Gabriele, Kubicki Dominik J, Emsley Lyndon
Institut des Sciences et Ingénierie Chimiques, Ecole Polytechnique Fédérale de Lausanne, Lausanne CH-1015, Switzerland.
J Phys Chem C Nanomater Interfaces. 2023 Jun 2;127(23):11094-11102. doi: 10.1021/acs.jpcc.3c01527. eCollection 2023 Jun 15.
The intrinsic low sensitivity of nuclear magnetic resonance (NMR) experiments limits their utility for structure determination of materials. Dynamic nuclear polarization (DNP) under magic angle spinning (MAS) has shown tremendous potential to overcome this key limitation, enabling the acquisition of highly selective and sensitive NMR spectra. However, so far, DNP methods have not been explored in the context of inorganic lead halide perovskites, which are a leading class of semiconductor materials for optoelectronic applications. In this work, we study cesium lead chloride and quantitatively compare DNP methods based on impregnation with a solution of organic biradicals with doping of high-spin metal ions (Mn) into the perovskite structure. We find that metal-ion DNP provides the highest bulk sensitivity in this case, while highly surface-selective NMR spectra can be acquired using impregnation DNP. The performance of both methods is explained in terms of the relaxation times, particle size, dopant concentration, and surface wettability. We envisage the future use of DNP NMR approaches in establishing structure-activity relationships in inorganic perovskites, especially for mass-limited samples such as thin films.
核磁共振（NMR）实验固有的低灵敏度限制了它们在材料结构测定中的应用。魔角旋转（MAS）下的动态核极化（DNP）已显示出克服这一关键限制的巨大潜力，能够获取高选择性和高灵敏度的NMR谱。然而，到目前为止，DNP方法尚未在无机卤化铅钙钛矿的背景下进行探索，无机卤化铅钙钛矿是一类用于光电子应用的领先半导体材料。在这项工作中，我们研究了氯化铯铅，并基于用有机双自由基溶液浸渍与向钙钛矿结构中掺杂高自旋金属离子（Mn）对DNP方法进行了定量比较。我们发现，在这种情况下，金属离子DNP提供了最高的整体灵敏度，而使用浸渍DNP可以获取高度表面选择性的NMR谱。两种方法的性能根据弛豫时间、颗粒尺寸、掺杂剂浓度和表面润湿性进行了解释。我们设想未来使用DNP NMR方法来建立无机钙钛矿中的构效关系，特别是对于诸如薄膜等质量受限的样品。
