Methods for determining the intrinsic and effective charges on spherical macroions.
Methods for determining the intrinsic and effective charges on spherical macroions.
复制标题
确定球形宏离子的固有电荷和有效电荷的方法。
作者：
J. M. Roberts;J. O.DÉ.;J. Osteryoung
单分散磺化聚苯乙烯乳胶悬浮液中颗粒上每个颗粒的固有电荷数 Z 是通过测量稳态伏安传输限制电流来确定的，该电流用于在含有过量支持电解质的悬浮液中的 Pt 盘微电极处还原氢抗衡离子。在去离子乳胶悬浮液中测量的极限电流产生相应的有效电荷 Z*。抗衡离子内层与颗粒的静电结合使得 Z* < Z。伏安法测定的电荷与分别通过滴定和电泳测定的固有和有效斯托克斯电荷一致。 ❖- 根据测量的粒子电泳迁移率计算出的电势产生了 Loeb 电荷数，它与 Z 的一致性比 Z* 更接近。对于球形带电大离子的现有数据，Z*/Z 随着固有电荷与大离子半径 Z/a 之比的增加而减小。这一发现得到了使用非线性泊松-玻尔兹曼方程从细胞模型计算得出的有效电荷值的支持，约定 Z* 是 c(r)/ <c> = 1 边界和细胞壁之间发现的电荷。
The intrinsic number of charges per particle, Z, on particles in a suspension of monodisperse sulfonated polystyrene latex is found by measuring steady-state voltammetric transport-limited currents for the reduction of hydrogen counterion at a Pt disk microelectrode in a suspension containing excess supporting electrolyte. Limiting currents measured in deionized latex suspensions yield a corresponding effective charge, Z*. Electrostatic binding of an inner layer of counterions to the particle renders Z* < Z. Voltammetrically determined charges agree with the intrinsic and effective Stokes charges as determined by titration and electrophoresis, respectively. ζ- Potentials calculated from the measured electrophoretic mobility of the particles yield the Loeb charge number, which agrees more closely with Z than with Z*. For existing data on spherically charged macroions, Z*/Z decreases with increasing ratio of intrinsic charge to macroion radius, Z/a. This finding is supported by effective charge values calculated from the cell model using the nonlinear Poisson-Boltzmann equation with the convention that Z* is the charge found between the c(r)/ 〈c〉 = 1 boundary and the cell wall.