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On-surface Reactions in Growth of High-Quality CdSe Nanocrystals in Nonpolar Solutions
Journal of the American Chemical Society ( IF 14.4 ) Pub Date : 2018-06-29 , DOI: 10.1021/jacs.8b04743
Runchen Lai 1 , Chaodan Pu 1 , Xiaogang Peng 1
Affiliation  

On-surface reaction mechanisms during the growth of high-quality CdSe nanocrystals are studied quantitatively and systematically by introducing a cyclic growth scheme. Prior to the repeating growth cycles, presynthesized CdSe QD seeds from a conventional scheme are reacted with an activated Se precursor, which is found to include three elementary steps and generate Se-terminated CdSe QDs. The cyclic growth in amine-octadecene solution includes two repeating half-reactions. The first half-reaction is between cadmium carboxylates in the bulk solution and the Se-terminated QDs, and the other is between the Se precursor in the bulk solution and the Cd-terminated QDs generated by the first half-reaction. While two elementary steps in the Se-surface half-reaction can be quantitatively treated as parallel kinetics, two elementary steps for the Cd-surface half-reaction must be treated as consecutive steps. These elementary steps are found to possess substantially different reaction rates as well as activation energies. Results indicate that, in the growth of compound semiconductor nanocrystals with metal carboxylates as cationic precursor (or ligands), the elementary step between activated anionic precursors in the bulk solution and the cationic sites on the surface of nanocrystals would be the rate-limiting step. This rate-limiting step should be the one that causes nucleation (or formation of small clusters by solution reactions) to be substantially faster than the corresponding growth through on-surface reactions.

中文翻译:

在非极性溶液中生长高质量 CdSe 纳米晶体的表面反应

通过引入循环生长方案,定量和系统地研究了高质量 CdSe 纳米晶体生长过程中的表面反应机制。在重复生长循环之前,来自传统方案的预合成 CdSe QD 种子与活化的 Se 前体反应,发现它包括三个基本步骤并生成 Se 终止的 CdSe QD。胺-十八碳烯溶液中的循环生长包括两个重复的半反应。第一个半反应发生在本体溶液中的羧酸镉与 Se 封端的 QD 之间,另一个发生在本体溶液中的 Se 前体与前半反应产生的 Cd 封端的 QD 之间。虽然硒表面半反应中的两个基本步骤可以定量处理为平行动力学,Cd 表面半反应的两个基本步骤必须视为连续步骤。发现这些基本步骤具有显着不同的反应速率以及活化能。结果表明,在金属羧酸盐作为阳离子前驱体(或配体)的化合物半导体纳米晶体的生长过程中,本体溶液中活化的阴离子前驱体与纳米晶体表面阳离子位点之间的基本步骤将是限速步骤。这个限速步骤应该是导致成核(或通过溶液反应形成小簇)比通过表面反应的相应生长快得多的步骤。发现这些基本步骤具有显着不同的反应速率以及活化能。结果表明,在金属羧酸盐作为阳离子前驱体(或配体)的化合物半导体纳米晶体的生长过程中,本体溶液中活化的阴离子前驱体与纳米晶体表面阳离子位点之间的基本步骤将是限速步骤。这个限速步骤应该是导致成核(或通过溶液反应形成小簇)比通过表面反应的相应生长快得多的步骤。发现这些基本步骤具有显着不同的反应速率以及活化能。结果表明,在金属羧酸盐作为阳离子前驱体(或配体)的化合物半导体纳米晶体的生长过程中,本体溶液中活化的阴离子前驱体与纳米晶体表面阳离子位点之间的基本步骤将是限速步骤。这个限速步骤应该是导致成核(或通过溶液反应形成小簇)比通过表面反应的相应生长快得多的步骤。本体溶液中活化的阴离子前体与纳米晶体表面的阳离子位点之间的基本步骤将是限速步骤。这个限速步骤应该是导致成核(或通过溶液反应形成小簇)比通过表面反应的相应生长快得多的步骤。本体溶液中活化的阴离子前体与纳米晶体表面的阳离子位点之间的基本步骤将是限速步骤。这个限速步骤应该是导致成核(或通过溶液反应形成小簇)比通过表面反应的相应生长快得多的步骤。
更新日期:2018-06-29
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