School of Materials Science and Engineering, Georgia Institute of Technology , Atlanta, Georgia 30332-0245, United States.
Langmuir. 2017 Apr 18;33(15):3576-3587. doi: 10.1021/acs.langmuir.6b04210. Epub 2017 Apr 3.
We report direct high-resolution monitoring of an evolving mixed nanodomain surface morphology during thiol adsorption on polyvinylpyrrolidone (PVP)-stabilized single crystal gold nanocrystals. The thiol adsorption and replacement dynamics are much more complex than a simple complete substitution of the initial polymer ligand. We observed that during ligand exchange with linear thiol, the nanocrystal surface evolved from an initial 1 nm uniform PVP coating into a remarkably stable network of globular PVP domains 20-100 nm in size and ∼4 nm in height surrounded by thiol self-assembled monolayers. The final stability of such a mixed thiol-PVP surface morphology can possibly be attributed to the interfacial energy reduction from partially solvophilic surfaces and the entropic gain from mixed ligand surface layers. The ligand-exchange dynamics and the unusual equilibrium morphology revealed here provide important insights into both displacement dynamics of surface-bound molecules and the nanoscale peculiarities of surface functionalization of colloidal metal substrates.
我们报告了在聚维酮（PVP）稳定的单晶金纳米晶体上巯基吸附过程中混合纳米域表面形态演变的直接高分辨率监测。巯基的吸附和取代动力学比初始聚合物配体的简单完全取代复杂得多。我们观察到，在与线性硫醇进行配体交换时，纳米晶体表面从初始的 1nm 均匀 PVP 涂层演变成大小为 20-100nm 且高度约为 4nm 的球形 PVP 域的非常稳定的网络，由巯基自组装单层包围。这种混合硫醇-PVP 表面形态的最终稳定性可能归因于部分亲溶剂表面的界面能降低和混合配体表面层的熵增益。这里揭示的配体交换动力学和异常平衡形态为表面结合分子的置换动力学和胶体金属基底表面功能化的纳米尺度特性提供了重要的见解。
