Fréchette Joëlle, Vanderlick T Kyle
Department of Chemical Engineering, Princeton University, Princeton, New Jersey 08540, USA.
J Phys Chem B. 2005 Mar 10;109(9):4007-13. doi: 10.1021/jp0454669.
The orientation and extent of adsorption of pyridine on a gold electrode is known to depend on applied potential and is well characterized. By use of the electrochemical surface forces apparatus, we measured the potential dependence of the double-layer interactions and adhesive forces between a gold electrode and a mica surface for different pyridine concentrations. We observed that, unlike mica-mica interactions, the gold-mica interactions were strongly affected by the presence of small concentrations of pyridine. We are able to reach high negative surface potentials (as determined by applying Derjaguin-Landau-Verway-Overbeek theory to our force measurements), which is similar to what is observed in the absence of pyridine. This demonstrates the electronic nature of the forces measured and shows that pyridine does not displace potential-determining ions on the surface. At positive potentials, where the interaction between gold and mica is attractive, pull-off measurements are a strong function of applied potential. The major effect of the presence of pyridine is on the observed shift in the potential of zero force (PZF), moving it to more negative potentials. This effect is caused by the strong dipole of the pyridine molecule. When the applied potential is cast as a deviation from the PZF, the effect of pyridine is to reduce adhesion between gold and mica. We modeled the potential-dependent adhesion of this system using an electrocapillary framework developed previously, and in doing so, we establish the relationship between the gold-liquid and gold-mica surface energies. In addition, we show that pyridine adsorption affects the capacitance of the gold-mica interface.
已知吡啶在金电极上的吸附取向和程度取决于外加电势，且已得到充分表征。通过使用电化学表面力装置，我们测量了不同吡啶浓度下金电极与云母表面之间双层相互作用和粘附力的电势依赖性。我们观察到，与云母-云母相互作用不同，少量吡啶的存在会强烈影响金-云母相互作用。我们能够达到高负表面电势（通过将德亚金-朗道-维韦-奥弗贝克理论应用于我们的力测量来确定），这与在没有吡啶的情况下观察到的情况类似。这证明了所测量力的电子性质，并表明吡啶不会取代表面上的电势决定离子。在正电势下，金和云母之间的相互作用具有吸引力，剥离测量是外加电势的强函数。吡啶存在的主要影响是观察到零力电势（PZF）发生偏移，使其向更负的电势移动。这种效应是由吡啶分子的强偶极引起的。当将外加电势表示为相对于PZF的偏差时，吡啶的作用是降低金和云母之间的粘附力。我们使用先前开发的电毛细管框架对该系统的电势依赖性粘附进行了建模，在此过程中，我们建立了金-液体和金-云母表面能之间的关系。此外，我们表明吡啶吸附会影响金-云母界面的电容。
