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Surface Sites and Ligation in Amine-capped CdSe Nanocrystals** |
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| Authors: | Dr Weicheng Cao Dr Alexander Yakimov Dr Xudong Qian Dr Jiongzhao Li Prof Dr Xiaogang Peng Prof Dr Xueqian Kong Prof Dr Christophe Copéret |
| Institution: | 1. Department of Chemistry and Applied Biosciences, ETH Zürich, 8093 Zürich, Switzerland
Department of Chemistry, Key Laboratory of Excited-State Materials of Zhejiang Province, Zhejiang University, Hangzhou, 310058 China These authors contributed equally to this work.;2. Department of Chemistry and Applied Biosciences, ETH Zürich, 8093 Zürich, Switzerland These authors contributed equally to this work.;3. Department of Chemistry, Key Laboratory of Excited-State Materials of Zhejiang Province, Zhejiang University, Hangzhou, 310058 China These authors contributed equally to this work.;4. Department of Chemistry, Key Laboratory of Excited-State Materials of Zhejiang Province, Zhejiang University, Hangzhou, 310058 China;5. Institute of Translational Medicine, Shanghai Jiao Tong University, Shanghai, 200240 China;6. Department of Chemistry and Applied Biosciences, ETH Zürich, 8093 Zürich, Switzerland |
| Abstract: | Converting colloidal nanocrystals (NCs) into devices for various applications is facilitated by designing and controlling their surface properties. One key strategy for tailoring surface properties is thus to choose tailored surface ligands. In that context, amines have been universally used, with the goal to improve NCs synthesis, processing and performances. However, understanding the nature of surface sites in amine-capped NCs remains challenging, due to the complex surface compositions as well as surface ligands dynamic. Here, we investigate both surface sites and amine ligation in CdSe NCs by combining advanced NMR spectroscopy and computational modelling. Notably, dynamic nuclear polarization (DNP) enhanced 113Cd and 77Se 1D NMR helps to identify both bulk and surface sites of NCs, while 113Cd 2D NMR spectroscopy enables to resolve amines terminated sites on both Se-rich and nonpolar surfaces. In addition to directly bonding to surface sites, amines are shown to also interact through hydrogen-bonding with absorbed water as revealed by 15N NMR, augmented with computations. The characterization methodology developed for this work provides unique molecular-level insight into the surface sites of a range of amine-capped CdSe NCs, and paves the way to identify structure-function relationships and rational approaches towards colloidal NCs with tailored properties. |
| Keywords: | Colloidal Nanocrystals DNP Enhanced NMR Surface Site Amine Ligands |