Preuss M, Butt HJ
Institut für Physikalische Chemie, Universität Mainz, Mainz, 55099, Germany
J Colloid Interface Sci. 1998 Dec 15;208(2):468-477. doi: 10.1006/jcis.1998.5833.
The aim of this study was to measure the contact angles of individual colloidal spheres ( solidus in circle 4.4 µm) and compare it to contact angles obtained on similarly prepared planar surfaces. For this purpose the particles were attached to atomic force microscope cantilevers. Then the force between the particle in aqueous medium and an air bubble was measured versus the distance. From the resulting force curves we obtained contact angles and detachment forces of single particles. Contact angles of gold coated silica particles were adjusted between 20 degrees and 100 degrees by self-assembling monolayers from different mixtures of undecanethiols and omega-hydroxy undecanethiols from solution. In parallel, contact angles on flat gold surfaces prepared in the same way were determined by the sessile drop method. A systematic difference between contact angles measured with particles and on planar surfaces was observed. Results are discussed in terms of line tension of the three-phase contact line. In addition, detachment forces were measured. Detachment forces were slightly higher than predicted from flotation theory. This might be caused by a pinning of the three phase contact line. Copyright 1998 Academic Press.
本研究的目的是测量单个胶体球（直径4.4 µm的实心球）的接触角，并将其与在类似制备的平面表面上获得的接触角进行比较。为此，将颗粒附着在原子力显微镜悬臂上。然后测量水性介质中的颗粒与气泡之间的力随距离的变化。从所得的力曲线中，我们获得了单个颗粒的接触角和脱离力。通过从溶液中不同比例的十一烷硫醇和ω-羟基十一烷硫醇自组装单分子层，将涂金二氧化硅颗粒的接触角调整在20度至100度之间。同时，采用静滴法测定以相同方式制备的平坦金表面的接触角。观察到用颗粒测量的接触角与平面表面上的接触角之间存在系统差异。根据三相接触线的线张力对结果进行了讨论。此外，还测量了脱离力。脱离力略高于浮选理论的预测值。这可能是由于三相接触线的钉扎作用所致。版权所有1998年学术出版社。
