Kinetics of Isovalent (Cd2+) and Aliovalent (In3+) Cation Exchange in Cd1-xMnxSe Nanocrystals
Kinetics of Isovalent (Cd2+) and Aliovalent (In3+) Cation Exchange in Cd1-xMnxSe Nanocrystals
复制标题
DOI：
10.1021/jacs.6b05649
复制
发表时间：
2016-10-05
影响因子：
15
通讯作者：
Gamelin, Daniel R.
中科院分区：
文献类型：
--
作者：
Chakraborty, Pradip;Jin, Yu;Gamelin, Daniel R.
离子交换（其中向内扩散的离子取代晶格离子）已被广泛用作半导体掺杂和固体到固体化学转化的合成工具，无论是在本体还是纳米尺度上。在这里，我们对阳离子交换反应进行了系统研究，该反应涉及 CdSe 纳米晶体中 Mn2+ 被 Cd2+ 或 In3+ 置换。对于两种进入的阳离子，Mn2+ 置换是自发的，但是热激活的，在广泛的实验温度范围内遵循阿伦尼乌斯行为。在任何给定温度下，In3+ 的阳离子交换比 Cd2+ 的阳离子交换快大约 2 个数量级，这说明了对引入阳离子的关键依赖性。对菲克斯定律扩散模型内的动力学数据进行定量分析，得出两种传入离子的扩散势垒 (E-D) 和限制扩散率 (D-0)。尽管动力学差异很大，但两种反应（In3+ 和 Cd2+）的 E-D 扩散势垒接近 1.1 eV，无法区分。发现 In3+ 的 Mn2+ 阳离子交换的扩散率显着增强。总的来说，这些发现为胶体半导体纳米晶体内的阳离子扩散提供了独特的实验见解，有助于我们对纳米科学这一丰富而重要的领域的基本理解。
Ion exchange, in which an in-diffusing ion replaces a lattice ion, has been widely exploited as a synthetic tool for semiconductor doping and solid-to-solid chemical transformations, both in bulk and at the nanoscale. Here, we present a systematic investigation of cation-exchange reactions that involve the displacement of Mn2+ from CdSe nanocrystals by Cd2+ or In3+. For both incoming cations, Mn2+ displacement is spontaneous but thermally activated, following Arrhenius behavior over a broad experimental temperature range. At any given temperature, cation exchange by In3+ is approximately 2 orders of magnitude faster than that by Cd2+, illustrating a critical dependence on the incoming cation. Quantitative analysis of the kinetics data within a Ficks-law diffusion model yields diffusion barriers (E-D) and limiting diffusivities (D-0) for both incoming ions. Despite their very different kinetics, indistinguishable diffusion barriers of E-D approximate to 1.1 eV are found for both reactions (In3+ and Cd2+). A dramatically enhanced diffusivity is found for Mn2+ cation exchange by In3+. Overall, these findings provide unique experimental insights into cation diffusion within colloidal semiconductor nanocrystals, contributing to our fundamental understanding of this rich and important area of nanoscience.