Competitive Anionic Exchange of Thiolate Ligands onto Aqueous Phosphonate-Capped Quantum Dots
Competitive Anionic Exchange of Thiolate Ligands onto Aqueous Phosphonate-Capped Quantum Dots
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DOI：
10.1021/acs.jpcc.2c05568
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发表时间：
2022-10
期刊：
影响因子：
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通讯作者：
J. Dunlap;Nuwanthaka P. Jayaweera;P. Pellechia;Andrew B. Greytak
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文献类型：
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作者：
J. Dunlap;Nuwanthaka P. Jayaweera;P. Pellechia;Andrew B. Greytak
采用等温滴定量热法（ITC）研究了碱性条件下，一系列巯基配体与锌基CdSe/ZnS核/壳量子点（QDs）表面的相对结合强度。一个不稳定的亲水性中间体，2-氨基乙基膦酸（AEP），被引入的地方天然疏水羧酸配体，以产生水溶性量子点，并提供一个通用的起点竞争性阴离子交换反应。我们引入不同链长的单硫醇，和二硫醇类似物（二氢硫辛酸），以探测链长和齿数对结合强度的影响。每个配体的引入产生放热响应。单硫醇中链长的增加导致平衡交换常数Kex的增加，表明较长的链长导致更强的结合。然而，较短链的巯基丙酸显示出更大的总疏水性，这似乎表明可接近的结合位点的总数更大。二硫醇配体的引入产生比单齿硫醇更大的Kex，这与从之前的观察中推断的更大的结合强度和稳定性一致，并且配体密度与饱和时的短链巯基丙酸相当。这项工作应有助于发展稳定和多功能的水溶性量子点胶体的生物成像和传感应用。
This study examines the relative binding strength of a series of thiolate ligands to the surfaces of zincblende CdSe/ZnS core/shell quantum dots (QDs) passivated by phosphonate ligands under basic conditions in water by means of isothermal titration calorimetry (ITC). A labile hydrophilic intermediate, 2-aminoethylphosphonic acid (AEP), was introduced in place of native hydrophobic carboxylate ligands to produce water-soluble QDs and provide a universal starting point for competitive anionic exchange reactions. We introduce monothiols of different chain lengths, and a dithiol analogue (dihydrolipoic acid), to probe the effects of chain length and denticity on binding strength. The introduction of each of the ligands produces an exothermic response. An increase in chain length among the monothiols led to an increase in the equilibrium exchange constant,Kex, indicating longer chain lengths lead to stronger binding. However, the shorter chain mercaptopropionic acid showed greater total exothermicity, which appears to indicate a greater total number of accessible binding sites. The introduction of a dithiol ligand produces a largerKexthan the monodentate thiols, consistent with greater binding strength and stability inferred from previous observations, and ligand density comparable to the shorter chain mercaptopropionic acid at saturation. This work should aid in the development of stable and versatile water-soluble QD colloids for bioimaging and sensing applications.