Department of Chemistry, Iowa State University, 2438 Pammel Drive, Ames, IA, 50011, USA.
US Department of Energy, Ames Laboratory, 2756 Gilman Hall, Ames, IA, 50011, USA.
Angew Chem Int Ed Engl. 2017 Aug 7;56(33):9802-9806. doi: 10.1002/anie.201704471. Epub 2017 Jul 17.
Engineering nanoparticle (NP) functions at the molecular level requires a detailed understanding of the dynamic processes occurring at the NP surface. Herein we show that a combination of dark-state exchange saturation transfer (DEST) and relaxation dispersion (RD) NMR experiments on gel-stabilized NP samples enables the accurate determination of the kinetics and thermodynamics of adsorption. We used the former approach to describe the interaction of cholic acid (CA) and phenol (PhOH) with ceria NPs with a diameter of approximately 200 nm. Whereas CA formed weak interactions with the NPs, PhOH was tightly bound to the NP surface. Interestingly, we found that the adsorption of PhOH proceeds via an intermediate, weakly bound state in which the small molecule has residual degrees of rotational diffusion. We believe the use of aqueous gels for stabilizing NP samples will increase the applicability of solution NMR methods to the characterization of nanomaterials.
在分子水平上设计纳米颗粒 (NP) 的功能需要深入了解 NP 表面发生的动态过程。在此，我们展示了暗态交换饱和转移 (DEST) 和弛豫分散 (RD) NMR 实验的组合可用于准确确定吸附的动力学和热力学。我们使用前者的方法来描述直径约为 200nm 的铈纳米颗粒与胆酸 (CA) 和苯酚 (PhOH) 的相互作用。CA 与 NPs 形成弱相互作用，而 PhOH 则紧密结合在 NP 表面。有趣的是，我们发现 PhOH 的吸附是通过一个中间弱结合态进行的，在这个中间态中，小分子仍然具有一定程度的旋转扩散。我们相信，使用水凝胶来稳定 NP 样品将增加溶液 NMR 方法在纳米材料表征中的适用性。
