Department of Theoretical Chemistry and Amsterdam Center for Multiscale Modeling (ACMM), VU University Amsterdam, De Boelelaan 1083, 1081 HV Amsterdam, The Netherlands.
Department of Nanochemistry, Istituto Italiano di Tecnologia, Via Morego 30, 16163 Genova, Italy.
Nanoscale. 2023 Apr 27;15(16):7410-7419. doi: 10.1039/d2nr06681e.
Synthesis protocols of colloidal semiconductor nanocrystals (NCs) comprise the coordination of the semiconductive inorganic core by a layer of organic ligands, which play a crucial role in stabilizing the NCs in organic solvents. Understanding the distribution, binding and mobility of ligands on the different NC facets is key to prevent the formation of surface defects and to optimize the overall optoelectronic efficiency of these materials. In this paper, we employed classical molecular dynamics (MD) simulations to shed light on the plausible locations, binding modes and mobilities of carboxylate ligands on the different facets of CdSe nanocrystals. Our results suggest that these features are influenced by the temperature of the system and the coordination number of the surface (Cd and Se) atoms. High ligand mobilities and structural rearrangements are linked to a low coordination of the Cd atoms. Undercoordinated Se atoms, which are considered the culprit of hole trap states in the bandgap of the material, are instead found to spontaneously form on the nanosecond timescale, making them likely candidates for an efficient photoluminescence quenching mechanism.
胶体半导体纳米晶体（NCs）的合成方案包括由有机配体层配位的半导体无机核，该配体层在有机溶剂中对 NCs 的稳定起着至关重要的作用。了解配体在不同 NC 晶面上的分布、结合和迁移率对于防止表面缺陷的形成和优化这些材料的整体光电效率至关重要。在本文中，我们采用经典分子动力学（MD）模拟来阐明羧酸配体在 CdSe 纳米晶体不同晶面上的可能位置、结合模式和迁移率。我们的结果表明，这些特性受到系统温度和表面（Cd 和 Se）原子配位数的影响。高配体迁移率和结构重排与 Cd 原子的低配位数有关。相反，被认为是材料带隙中空穴陷阱态罪魁祸首的低配位 Se 原子在纳秒时间尺度上自发形成，这使它们成为有效光致发光猝灭机制的候选者。
