Department of Chemistry , University of North Carolina , Chapel Hill , North Carolina 27599-3290 , United States.
Nano Lett. 2019 Feb 13;19(2):1151-1157. doi: 10.1021/acs.nanolett.8b04544. Epub 2019 Jan 14.
Quantum dot surfaces are redox active and are known to influence the electronic properties of nanocrystals, yet the molecular-level changes in surface chemistry that occur upon addition of charge are not well understood. In this paper, we report a systematic study monitoring changes in surface coordination chemistry in 3.4 nm CdSe quantum dots upon remote chemical doping by the radical anion reductant sodium naphthalenide (Na[CH]). These studies reveal a new mechanism for charge-balancing the added electrons that localize on surface states through loss of up to ca. 5% of the native anionic carboxylate ligands, as quantified through a combination of UV-vis absorption, H NMR, and FTIR spectroscopies. A new method for distinguishing between reduction of surface metal and chalcogenide ions by monitoring ligand loss and optical changes upon doping is introduced. This work emphasizes the importance of studying changes in surface chemistry with remote chemical doping and is more broadly contextualized within the redox reactivity of the QD surface.
量子点表面具有氧化还原活性，已知会影响纳米晶体的电子性质，但对于在添加电荷时表面化学发生的分子水平变化还不是很了解。在本文中，我们报告了一项系统研究，监测了在自由基阴离子还原剂萘钠（Na[CH]）远程化学掺杂下，3.4nm CdSe 量子点表面配位化学的变化。这些研究揭示了一种新的电荷平衡机制，通过失去多达约 5%的天然阴离子羧酸盐配体，来局部化添加的电子，通过紫外-可见吸收、H NMR 和傅里叶变换红外光谱的组合进行定量。引入了一种新的方法，通过监测掺杂时配体的损失和光学变化来区分表面金属和硫属离子的还原，这强调了用远程化学掺杂研究表面化学变化的重要性，并更广泛地将其置于 QD 表面的氧化还原反应性中。
