通过动态核极化增强 77Se 和 113Cd 固态核磁共振光谱揭示 CdSe 纳米晶体的表面结构
Journal of the American Chemical Society
(
IF
14.4
)
Pub Date : 2021-06-04
, DOI:
10.1021/jacs.1c03162
Yunhua Chen
1,
2
,
Rick W Dorn
1,
2
,
Michael P Hanrahan
1,
2
,
Lin Wei
2
,
Rafael Blome-Fernández
2
,
Alan M Medina-Gonzalez
2
,
Marquix A S Adamson
2
,
Anne H Flintgruber
1
,
Javier Vela
1,
2
,
Aaron J Rossini
1,
2
Affiliation
U.S. Department of Energy Ames Laboratory, Ames, Iowa 50011, United States.
Department of Chemistry, Iowa State University, Ames, Iowa 50011, United States.
动态核极化 (DNP) 固态核磁共振 (SSNMR) 光谱用于获得具有板状或球状形态的闪锌矿 CdSe 纳米晶体 (NCs) 的详细表面结构，这些形态被羧酸配体封端。1D 113 Cd 和77 Se 交叉极化魔角自旋 (CPMAS) NMR 光谱揭示了来自 NC 表面上的 Cd 和 Se 原子的不同信号，以及那些位于表面下方的块状环境中的信号。113 Cd 交叉极化魔角转向 (CP-MAT) 实验确定了 CdSe 3 O、CdSe 2 O 2和 CdSeO 3NCs表面的Cd配位环境，其中氧原子可能来自配位的羧酸盐配体。从DNP灵敏度增益启用天然同位素丰度的2D同核113 CD- 113 Cd和77 SE- 77 Se和异核113 CD- 77，其揭示了镉和Se原子的连通性硒标量相关固态NMR实验。重要的是，77 Se{ 113 Cd} 标量异核多量子相干 ( J -HMQC) 实验用于选择性地测量单键77 Se– 113 Cd 标量耦合常数 ( 1J ( 77 Se, 113 Cd))。根据1 J ( 77 Se, 113 Cd) 的知识，异核77 Se{ 113 Cd} 自旋回波（J分辨）NMR 实验用于确定与 Se 原子键合的 Cd 原子数，反之亦然。所述Ĵ分辨实验直接证实，主要镉和Se表面物质具有的CdSe 2 ö 2和SECD 4化学计量，分别。考虑到闪锌矿 CdSe 的晶体结构以及血小板和球体的固态 NMR 数据的相似性，我们得出结论，球状 CdSe NCs 的表面主要由 {100} 面组成。这里概述的方法通常适用于获得各种主族半导体纳米粒子的详细表面结构。
"点击查看英文标题和摘要"
Revealing the Surface Structure of CdSe Nanocrystals by Dynamic Nuclear Polarization-Enhanced 77Se and 113Cd Solid-State NMR Spectroscopy
Dynamic nuclear polarization (DNP) solid-state NMR (SSNMR) spectroscopy was used to obtain detailed surface structures of zinc blende CdSe nanocrystals (NCs) with plate or spheroidal morphologies which are capped by carboxylic acid ligands. 1D 113Cd and 77Se cross-polarization magic angle spinning (CPMAS) NMR spectra revealed distinct signals from Cd and Se atoms on the surface of the NCs, and those residing in bulk-like environments, below the surface. 113Cd cross-polarization magic-angle-turning (CP-MAT) experiments identified CdSe3O, CdSe2O2, and CdSeO3 Cd coordination environments on the surface of the NCs, where the oxygen atoms are presumably from coordinated carboxylate ligands. The sensitivity gain from DNP enabled natural isotopic abundance 2D homonuclear 113Cd–113Cd and 77Se–77Se and heteronuclear 113Cd–77Se scalar correlation solid-state NMR experiments which revealed the connectivity of the Cd and Se atoms. Importantly, 77Se{113Cd} scalar heteronuclear multiple quantum coherence (J-HMQC) experiments were used to selectively measure one-bond 77Se–113Cd scalar coupling constants (1J(77Se, 113Cd)). With knowledge of 1J(77Se, 113Cd), heteronuclear 77Se{113Cd} spin echo (J-resolved) NMR experiments were used to determine the number of Cd atoms bonded to Se atoms and vice versa. The J-resolved experiments directly confirmed that major Cd and Se surface species have CdSe2O2 and SeCd4 stoichiometries, respectively. Considering the crystal structure of zinc blende CdSe and the similarity of the solid-state NMR data for the platelets and spheroids, we conclude that the surface of the spheroidal CdSe NCs is primarily composed of {100} facets. The methods outlined here will generally be applicable to obtain detailed surface structures of various main group semiconductor nanoparticles.
