Kazuo Inamori School of Engineering, Alfred University, 2 Pine Street, Alfred, New York 14802, United States.
Langmuir. 2012 Jun 26;28(25):9267-74. doi: 10.1021/la300586f. Epub 2012 Jun 6.
We present a systematic investigation and analysis of the structure and stability of reverse micelle systems with the addition of NH(4)OH, ZrOCl(2), and Al(NO(3))(3) salts. We demonstrate that the reverse micelle size decreases with increasing salt additions until one reaches a critical concentration, which characterizes the onset of system destabilization. The concept of an electrical double layer, as it applies to reverse micelles, is considered for explaining features of destabilization, including the initial decrease in reverse micelle size, the destabilization concentration, and the effect of cation valence. We propose that the reduction in size prior to instability is caused by compression of the reverse micelle electrical double layers, as higher concentrations of salts are present. The reduced thickness of the electrical double layers allows the decaying potentials to move into closer proximity to each other before generating enough repulsion to balance the forces for reverse micelle formation and form a new equilibrium average reverse micelle size. The point of reverse micelle instability has been related to the formation of a two-phase system as a result of the inability to further compress the salt co-ions in the core of the reverse micelles, which would cause an excessive repulsive force between the overlapping potentials. We have extracted a critical potential of -89 nV between the two overlapping potentials for the AOT/water/isooctane (ω(0) = 10) systems studied. All these effects have important implications for the preparation of nanopowders by reverse micelle synthesis. If the reverse micelles are unstable before the precipitates are formed, then the advantage of reverse micelle synthesis is immediately lost.
我们对添加了 NH(4)OH、ZrOCl(2) 和 Al(NO(3))(3)盐的反胶束体系的结构和稳定性进行了系统的研究和分析。我们证明，随着盐的加入，反胶束的尺寸减小，直到达到一个临界浓度，这标志着体系失稳的开始。考虑到反胶束的电双层概念，适用于解释失稳的特征，包括反胶束尺寸的初始减小、失稳浓度以及阳离子价态的影响。我们提出，在不稳定之前的尺寸减小是由于反胶束电双层的压缩引起的，因为存在更高浓度的盐。电双层的厚度减小使得衰减电势在产生足够的斥力以平衡形成反胶束的力并形成新的平衡平均反胶束尺寸之前相互靠近。反胶束不稳定性的点已经与两相体系的形成有关，这是由于无法进一步压缩反胶束核心中的盐共离子，这将导致重叠电势之间产生过大的斥力。我们已经从两个重叠电势之间提取出一个临界电势为-89 nV，用于研究的 AOT/水/异辛烷（ω(0) = 10）体系。所有这些效应对通过反胶束合成制备纳米粉末都有重要意义。如果在沉淀物形成之前反胶束不稳定，那么反胶束合成的优势就会立即丧失。
