Institute of Catalysis and Surface Chemistry Polish Academy of Science, Cracow, Poland.
J Colloid Interface Sci. 2011 Aug 1;360(1):195-203. doi: 10.1016/j.jcis.2011.02.025. Epub 2011 Feb 15.
The streaming potential of mica covered by bilayers of latex particles was measured using the parallel-plate channel cell. The size of the first latex (A500) bearing amidine charged groups was 503 nm and the second latex (L800) bearing sulfonate groups was 810 nm (at pH 5.5 and an ionic strength of 10(-2)M). The A500 latex exhibited an isoelectric point at pH 10.5, whereas the L800 latex was strongly negative at all pH. Mica sheets were precovered first by the A500 latex particles under diffusion transport conditions. The coverage of this supporting layer was regulated between 0.02 and 0.5 by changing the bulk concentration of latex and the deposition time. Then, the second layer of the L800 latex of regulated coverage up to 0.55 was deposited under the diffusion transport. The coverage of particles and their distributions in both layers were determined by a direct enumeration of particles by optical microscopy under wet conditions and by AFM. It was shown that the structure of the L800 particle layers and the maximum coverage were in accordance with theoretical simulations performed according to the random sequential adsorption (RSA) model. After forming bilayers of desired composition and structure, streaming potential measurements were carried out. The influence of the mica substrate, the supporting layer coverage, and its zeta potential on the apparent zeta potential of bilayers was systematically studied. It was established that for a bilayer coverage exceeding 0.20, the net zeta potential became independent of the substrate and the supporting layer zeta potentials. Then, the asymptotic values of the zeta potential of the bilayer approach 1/√2=0.71 of the bulk zeta potential of the particles forming the external (second) layer. This behavior was interpreted theoretically in terms of the electrokinetic model derived previously for monolayers. It was also concluded that results obtained in this work can be exploited for interpretation of polyelectrolyte film formation in the layer by layer (LbL) processes and protein adsorption pertinent to the antigen/antibody interactions.
采用平行板通道池测量了双层胶乳粒子覆盖云母的流动电势。第一个胶乳（A500）带正电荷的 amidine 基团的粒径为 503nm，第二个胶乳（L800）带负电荷的 sulfonate 基团的粒径为 810nm（在 pH5.5 和离子强度为 10(-2)M 时）。A500 胶乳在 pH10.5 时表现出等电点，而 L800 胶乳在所有 pH 值下均呈强负电性。云母片首先在扩散传输条件下被 A500 胶乳颗粒预先覆盖。通过改变胶乳的体相浓度和沉积时间，调节支撑层的覆盖率在 0.02 到 0.5 之间。然后，在扩散传输下，将具有调节覆盖率的 0.55 的 L800 胶乳的第二层沉积下来。通过在湿条件下使用光学显微镜直接对颗粒进行计数和 AFM，确定了两层中颗粒的覆盖率及其分布。结果表明，L800 颗粒层的结构和最大覆盖率与根据随机顺序吸附（RSA）模型进行的理论模拟相符。在形成具有所需组成和结构的双层后，进行了流动电势测量。系统研究了云母基底、支撑层覆盖率及其 ζ 电势对双层的表观 ζ 电势的影响。结果表明，对于覆盖率超过 0.20 的双层，净 ζ 电势不再依赖于基底和支撑层的 ζ 电势。然后，双层的 ζ 电势渐近值接近形成外部（第二层）的颗粒的体相 ζ 电势的 1/√2=0.71。这种行为根据先前为单层推导的动电模型进行了理论解释。还得出结论，本工作中的结果可用于解释在层层（LbL）过程中形成的聚电解质膜和与抗原/抗体相互作用有关的蛋白质吸附。
