胶体导体表面静电作用

I. INTRODUCTION The electrostatic interaction between charge-stabilized colloidal particles is mediated and modified by simple ions dissolved in a supporting electrolyte. For like-charged particles, the resulting effective interaction, described by the Poisson-Boltzmann meanfield theory , is predicted to be always purely repulsive independent of the strength of the electrostatic coupling, the valency of the suspended ions, or the state of confinement of the suspension.
In all such cases, mean-field theory fails because the relevant electrostatic interactions exceed the thermal energy scale over length scales of interest. Colloidal spheres in symmetric monovalent electrolytes, by contrast, are expected to satisfy the conditions of the mean-field approximation. Indeed,PM simulations of charged colloidal spheres in symmetric monovalent electrolytes are found to agree well with mean-field predictions 13–15, a class of systems for which Poisson-Boltzmann theory is expected to be accurate. Experimental results, however, have been more mixed. Direct measurements of colloidal pair interactions 16–18 in bulk dispersions qualitatively agree with mean-field predictions.
When applied to dispersions confined to thin layers by charged glass surfaces, however, these same methods have repeatedly revealed longranged attractions 19–22 that are too strong to be accounted for by van der Waals interactions 22,23 and are inconsistent with PoissonBoltzmann theory 2–4. Measurements on colloidal spheres confined by just a single glass wall, by contrast, have not revealed anomalous attractions 18,24–26. These measurements were performed at much lower ionic strengths than those in thin samples, however. One explanation for this seeming inconsistency is that the appearance of confinement-induced like-charge attractions might depend strongly on the ionic concentration. Perhaps, then, even a single bounding surface could induce anomalous attractions if the ionic strength were in the appropriate range.当应用在一层薄薄分散密闭的带
静电电荷之间的相互作用，介导的稳定胶体粒子和电解液是作为媒介 和重排通过简单的离子溶解。对于类似的带电粒子，由此产生的有效 互动，被泊松-波尔兹曼平均场理论所描述，预计总是纯粹独立的静电 耦合的强度的，悬浮离子的化合价，暂时紧闭的态。
經典 Poisson-Boltzmann ‡\論 膠體科學中對靜電力的處理多基於經典的Poisson-Boltzmann 理論，其包 含了電學及熱運動的兩個重要結果。 從靜電學來說： 電荷與電位滿足高斯定律，或等效的Poisson 方程。由此 方程可以從已知的離子分佈算出電位。從統計熱力學來看：根據電位能 的高低，離子位置的分佈應滿足Boltzmann 分佈。以上兩個結果均屬準確。 如果進一步簡化問題，忽略掉離子兩兩之間的位置關連，我們以離子的 濃度滿足Boltzmann 分佈，而其Boltzmann 分佈是由平均電位能來計算。 這個近似的平均場理論便是Poisson-Boltzmann理論。Poisson-Boltzmann 理論是目前研究帶電懸浮粒子之間作用力的標準工具。以下，有一些現 象是Poisson Boltzmann 理論無法解釋的。另一些現象初看奇怪，最 後仍是與Poisson-Boltzmann ‡\論的計算吻合。
即使在所谓的原始模型永磁体上，平均场理论仍然出现偏离，那 些被看做胶体粒子和溶解离子的带电硬球，并被描述为电介质悬 浮液连续。类似的效果也更预测更加普遍的模型，当联系到10， 盐的具体分散的力11，简单的离子大小的影响成为重要的12。
10 R. Kjellander and S. Marcelja, Chem. Phys. Lett. 112, 49 1984. 11 F. W. Tavares, D. Bratko, H. W. Blanch, and J. M. Prausnitz, J. Phys. Chem. B 108, 9228 2004. 12 H. Greberg and R. Kjellander, J. Chem. Phys. 108, 2940 1998.
Like-charged colloidal spheres dispersed in de-ionized water are supposed to repel each other. Instead, artifact-corrected video microscopy measurements reveal an anomalous long-ranged like-charge attraction in the interparticle pair potential when the spheres are confined to a layer by even a single-charged glass surface. These attractions can be masked by electrostatic repulsions at low ionic strengths. Coating the bounding surfaces with a conducting gold layer suppresses the attraction. These observations suggest a possible mechanism for the anomalous confinement-induced attractions. 带电胶体球分散在去离子水中本应该是相互排斥的,去影修正显微镜显影的 检查出现了一种反常的粒子间出现的两极长距离的静电作用，这种静电作 用出现在一个被一个单层玻璃包围的球体当中。这种作用被掩盖在低离子 强度的相互排斥作用下。将表面一种导电金属层来抑制相互吸引作用。这 个理论提出了对不规则的封闭导体内部作用的一种可能的原理。
在所有这些情况下，平均场理论的失败，因为有关的静电相互作用超过平衡长 度所产生热能。事实上，在一价均值电解质中的带电胶粒小球的永磁现象被证 明符合平均场理论13-15，在这个阶段poisson-boltzmann理论是准确的。但实 验的结果却很复杂。胶体在分散系的对电子效应从本质上符合平均场理论16-18。
These departures from mean-field behavior appear even the so-called primitive model PM, which treats both the colloidal particles and the dissolved ions as charged hard spheres and describes the suspending fluid as a uniform dielectric continuum. Similar effects are also predicted in more general models, when image charges 10, salt-specific dispersion forces 11, or the sizes of simple ions 12 become important.
This reasonable prediction is known to fail under some conditions. For example, both simulations and non-meanfield theoretical studies predict the possibility of an attraction 来自百度文库n bulk suspensions of like-charged colloidal particles if multivalent counterions are present see 6,7 and references therein. This attraction is mediated by strong ion-ion correlations induced by coupling to the charged colloidal particles. Experimental observations have confirmed similar predictions for highly charged parallel plates 8 and cylinders9. 这种已知的合理的推理在一些情况下失败了，例如，无论模拟和非平 均场理论研究的粒子如果存在多价抗衡，可能吸引了一大部分类似带 电胶体在悬浮液中，（可参见6，7 作为参考）。这种带电胶体所具有 的吸引力是强大的离子介导的离子粒子的相关性诱导耦合，实验观察 证实被控平行板高度类似的预测为8、9。
6 L. Belloni, J. Phys.: Condens. Matter 12, R549 2000. 7 P. Linse, Adv. Polym. Sci. 185, 111 2005.（反多型） （
8 P. Kékicheff, S. M. Celja, T. J. Senden, and V. E. Shubin, J. Chem. Phys. 8, 6098 1999. 9 J. L. Sikorav, J. Pelta, and F. Livolant, Biophys. J. 67, 1387 1994.
Colloidal electrostatic interactions near a conducting surface
胶体导体表面的静电作用 Marco Polin,1 David G. Grier,1 and Yilong Han2 1Center for Soft Matter（软物质） Research, New York University, 4 Washington Place, New York, New York 10003, USA 2Department of Physics, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong Received 2 May 2006; revised manuscript（手稿修订） received 19 July 2007; published 30 October 2007