Experimental study of electrostatically stabilized colloidal particles: colloidal stability and charge reversal.
Experimental study of electrostatically stabilized colloidal particles: colloidal stability and charge reversal.
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DOI：
10.1016/j.jcis.2011.02.039
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发表时间：
2011-06
影响因子：
9.9
通讯作者：
C. Schneider;M. Hanisch;B. Wedel;A. Jusufi;M. Ballauff
中科院分区：
文献类型：
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作者：
C. Schneider;M. Hanisch;B. Wedel;A. Jusufi;M. Ballauff
我们考虑了一价、二价和三价离子存在时胶体球之间的相互作用。由于表面电荷的静电斥力，胶体是稳定的。相互作用势Ψ的排斥部分是由慢凝血速率的精确测量得出的。这些“微表面电势测量”使我们能够确定弱斥力，其中Ψ约为几个kBt的数量级。将这些数据与在类似条件下测量的ζ电势进行了比较。在较高浓度下，二价和三价反离子都聚集在粒子表面非常接近的位置，导致电荷反转。发现发生电荷反转的盐浓度Ccrc总是高于临界凝聚浓度Cccc。然而，Ψ带对ζ势的分析表明，多价反离子的吸附开始于远低于Ccr的位置。因此，在二价和三价离子存在下的胶体稳定性不能用假设表面电荷相对于离子强度恒定的DLVO ansatz来描述。
We consider the interaction of colloidal spheres in the presence of mono-, di-, and trivalent ions. The colloids are stabilized by electrostatic repulsion due to surface charges. The repulsive part of the interaction potential Ψdis deduced from precise measurements of the rate of slow coagulation. These “microsurface potential measurements” allow us to determine a weak repulsion in which Ψdis of the order of a few kBT. These data are compared to ζ potential measured under similar conditions. At higher concentrations both di- and trivalent counterions accumulate at the very proximity of the particle surface leading to charge reversal. The salt concentration ccrat which charge reversal occurs is found to be always above the critical coagulation concentration cccc. The analysis of Ψdand of the ζ potential demonstrates, however, that adsorption of multivalent counterions starts far below ccr. Hence, colloid stability in the presence of di- and trivalent ions cannot be described in terms of a DLVO ansatz assuming a surface charge that is constant with regard to the ionic strength.