Chemical Sciences and Engineering Division, Argonne National Laboratory, Lemont, Illinois 60439, United States.
J Phys Chem Lett. 2023 Apr 20;14(15):3685-3690. doi: 10.1021/acs.jpclett.3c00225. Epub 2023 Apr 10.
We study the adsorption of trivalent neodymium on floating arachidic acid films at the air-water interface by two complementary surface specific probes, sum frequency generation spectroscopy and X-ray fluorescence near total reflection. In the absence of background ions, neodymium ions compensate for the surface charge of the arachidic acid film at a bulk concentration of 50 μM without any charge reversal. Increasing the bulk concentration to 1 mM does not change the neodymium surface coverage but affects the interfacial water structure significantly. In the presence of a high concentration of NaCl, there is overcharging at 1 mM Nd, i.e., 30% more Nd than needed to compensate for the surface charge. These results show that the total coverage of neodymium ions is not enough to describe the complete picture at the interface, and interfacial water and ion coverage needs to be considered together to understand more complex ion adsorption and transport processes.
我们通过两种互补的表面特异性探针——和频产生光谱学和 X 射线荧光近全反射——研究了三价钕离子在气/水界面浮动花生酸膜上的吸附。在不存在背景离子的情况下，在 50μM 的体相浓度下，钕离子补偿了花生酸膜的表面电荷，而没有任何电荷反转。将体相浓度增加到 1mM 不会改变钕的表面覆盖率，但会显著影响界面水结构。在高浓度 NaCl 存在下，在 1mM Nd 时存在过充电，即比补偿表面电荷所需的 Nd 多 30%。这些结果表明，钕离子的总覆盖率不足以描述界面上的完整情况，需要同时考虑界面水和离子覆盖率，以理解更复杂的离子吸附和传输过程。
