Bilotto Pierluigi, Imre Alexander M, Dworschak Dominik, Mears Laura L E, Valtiner Markus
Institute of Applied Physics, Applied Interface Physics, Vienna University of Technology, 1040 Vienna, Austria.
ACS Phys Chem Au. 2021 Nov 24;1(1):45-53. doi: 10.1021/acsphyschemau.1c00012. Epub 2021 Aug 23.
Function and properties at biologic as well as technological interfaces are controlled by a complex and concerted competition of specific and unspecific binding with ions and water in the electrolyte. It is not possible to date to directly estimate by experiment the interfacial binding energies of involved species in a consistent approach, thus limiting our understanding of how interactions in complex (physiologic) media are moderated. Here, we employ a model system utilizing polymers with end grafted amines interacting with a negatively charged mica surface. We measure interaction forces as a function of the molecule density and ion concentration in NaCl solutions. The measured adhesion decreases by about 90%, from 0.01 to 1 M electrolyte concentration. We further demonstrate by molecular resolution imaging how ions increasingly populate the binding surface at elevated concentrations, and are effectively competing with the functional group for a binding site. We demonstrate that a competing Langmuir isotherm model can describe this concentration-dependent competition. Further, based on this model we can quantitatively estimate ion binding energies, as well as binding energy relationships at a complex solid|liquid interface. Our approach enables the extraction of thermodynamic interaction energies and kinetic parameters of ionic species during monolayer level interactions at a solid|liquid interface, which to-date is impossible with other techniques.
生物界面以及技术界面的功能和性质受电解质中离子和水的特异性和非特异性结合的复杂协同竞争所控制。迄今为止，还不可能通过实验以一种一致的方法直接估算所涉及物种的界面结合能，因此限制了我们对复杂（生理）介质中相互作用如何调节的理解。在此，我们采用一个模型系统，该系统利用末端接枝胺的聚合物与带负电荷的云母表面相互作用。我们测量了相互作用力与NaCl溶液中分子密度和离子浓度的函数关系。在电解质浓度从0.01 M增加到1 M时，测得的粘附力降低了约90%。我们还通过分子分辨率成像证明，在较高浓度下离子如何越来越多地占据结合表面，并有效地与官能团竞争结合位点。我们证明了一个竞争朗缪尔等温线模型可以描述这种浓度依赖性竞争。此外，基于该模型，我们可以定量估算离子结合能以及复杂固液界面处的结合能关系。我们的方法能够在固液界面的单层水平相互作用过程中提取离子物种的热力学相互作用能和动力学参数，而这是其他技术迄今为止无法做到的。
