Hooper Thomas J N, Fang Yanan, Brown Alasdair A M, Pu Suan Hui, White Tim J
Centre of High Field NMR Spectroscopy and Imaging, Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, 21 Nanyang Link, Singapore 637371, Republic of Singapore.
School of Materials Science and Engineering, Nanyang Technological University, 50 Nanyang Drive, Singapore, 637553, Republic of Singapore.
Nanoscale. 2021 Oct 1;13(37):15770-15780. doi: 10.1039/d1nr04602k.
This investigation has characterised the structure and surface chemistry of CsPbBr nanocrystals with controlled diameters between 6.4 to 12.8 nm. The nanocrystals were investigated a thorough Cs solid state NMR and nuclear relaxation study, identifying and mapping radially-increasing nanoscale disorder. This work has formalised Cs NMR as a highly sensitive probe of nanocrystal size, which can conveniently analyse nanocrystals in solid forms, as they would be utilised in optoelectronic devices. A combined multinuclear solid state NMR and XPS approach, including Cs-H heteronuclear correlation 2D (HETCOR) NMR, was utilised to study the nanocrystal surface and ligands, demonstrating that the surface is Cs-Br rich with vacancies passivated by didodecyldimethylammonium bromide (DDAB) ligands. Furthermore, it is shown that a negligible amount of phosphonate ligands remain on the powder nanocrystal surface, despite the key role of octylphosphonic acid (OPA) in controlling the colloidal nanocrystal growth. The CsPbBr NCs were shown to be structurally stable under ambient conditions for up to 6 months, albeit with some particle agglomeration.
本研究对直径控制在6.4至12.8纳米之间的CsPbBr纳米晶体的结构和表面化学进行了表征。通过全面的Cs固态核磁共振和核弛豫研究对纳米晶体进行了研究，识别并绘制了径向增加的纳米级无序情况。这项工作将Cs核磁共振正式确立为纳米晶体尺寸的高灵敏度探针，它可以方便地分析固体形式的纳米晶体，就像它们在光电器件中被使用的那样。采用了包括Cs-H异核相关二维（HETCOR）核磁共振在内的多核固态核磁共振和XPS相结合的方法来研究纳米晶体表面和配体，结果表明表面富含Cs-Br，空位被十二烷基二甲基溴化铵（DDAB）配体钝化。此外，研究表明，尽管辛基膦酸（OPA）在控制胶体纳米晶体生长中起关键作用，但粉末纳米晶体表面残留的膦酸酯配体数量可以忽略不计。CsPbBr纳米晶体在环境条件下显示出长达6个月的结构稳定性，不过存在一些颗粒团聚现象。
