Model of formation of monodispersed colloids
Model of formation of monodispersed colloids
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DOI：
10.1021/jp011306a
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发表时间：
2001-11-29
影响因子：
3.3
通讯作者：
Matijevic, E
中科院分区：
文献类型：
--
作者：
Park, J;Privman, V;Matijevic, E
已经积累了大量的实验证据，证明单分散胶体的形成是通过一种比通常所排除的扩散“爆发成核”过程更复杂的机制进行的。相反，窄尺寸分布的胶体分散体的合成涉及两个不同的阶段。纳米级初级粒子在过饱和溶液中成核。然后它们聚集形成更大的均匀的次级颗粒。为了解释在这样的过程中的大小选择，已经开发了一个动力学模型，耦合的两个生长/聚集阶段。我们早期的研究表明，初级粒子的爆发成核生长强烈依赖于进入亚临界胚胎自由能中表面项的有效表面张力的值。本工作的目的是确定一个适当的控制参数的过程中的二次粒子的形成。我们尝试修改的聚集率占单线态尺寸和聚集扩散。我们发现，只有在二聚体形成速率中引入“瓶颈”因素对最终的尺寸分布有深远的影响，并提出了一种可能的尺寸控制机制。
Ample experimental evidence has been accumulated demonstrating that the formation of monodispersed colloids proceeds through a more complex mechanism than the generally excepted diffusional "burst nucleation" process. Instead, the synthesis of narrow-size-distribution colloidal dispersions involves two distinct stages. Nanosize primary particles are nucleated in a supersaturated solution. They then aggregate to form much larger uniform secondary particles. To explain the size selection in such a process, a kinetic model has been developed which couples the two growth/aggregation stages. Our earlier study has shown the burst-nucleation growth of the primary particles to depend strongly on the value of the effective surface tension entering the surface term in the free energy of the subcritical embryos. The aim of the present work has been to identify an appropriate control parameter in the process of secondary particle formation. We tried modifications of the aggregation rates to account for singlet size and aggregate diffusivity. We found that only the introduction of a "bottleneck" factor in the dimer formation rate has a profound effect on the final size distribution and suggests a possible size-control mechanism.