Role of Interfacial Tension in Nucleation beneath Monolayer Films

Abstract

Monolayer films at high surface pressures are well-ordered, and due to their 2D crystallinity they can act as sites of preferential nucleation. Recently it has been demonstrated that films at lower surface pressures can also be preferential nucleators, despite their decreased ordering. In this study we show that identifying the factors which can reduce the interfacial tension is vital to understanding the varied mechanisms through which nucleation beneath monolayer films can occur. In particular, the preferential nucleation that is observed at low to medium surface pressures is explained by the compressible film rearranging so as to minimize the lattice mismatch with the nucleating crystal face, thereby reducing the interfacial tension of the system. We introduce a more quantitative approach in this paper to gain a greater insight into this phenomenon. The nucleating species must be adsorbed upon the film as a prerequisite for nucleation. We demonstrate that the extent of this adsorption may be modeled using the appropriate Π−A curves and an equation derived from the Gibbs and Langmuir adsorption isotherms. This approach also allows values for the adsorption energy and interfacial tension for 100% adsorption to be estimated.

Crystallization of calcium oxalate monohydrate at dipalmitoylphosphatidylcholine monolayers in the presence of chondroitin sulfate A

“…Cooper et al, [27,28] indicated that in order to promote nucleation, it is not necessary to have a highly organized monolayer. Monolayers at low or medium pressure, in which a greater dynamical freedom and compressibility occurs, can lead to higher nucleation rates.…”

Controlled and uncontrolled crystallization of calcium oxalate monohydrate in the presence of citric acid

“…Second, the monolayers at low pressures have a greater dynamic freedom and compressibility. 3,39, 40 The monolayer interfaces at low pressure have the ability to optimize the…”

Structural adaptability in an organic template for CaCO3 mineralization

“…31 Cooper, Sessions, and Lubetkin studied amino acid nucleation under partially compressed films and concluded that the ability of the film to reorganize to reduce interfacial energy can optimize nucleation. 32,33 In subsequent publications a mixture of mechanisms began to be represented, with some still emphasizing structure-based molecular recognition [34][35][36][37][38] and others discussing interfacial electrostatics as the predominant mechanism. [39][40][41][42][43][44][45][46][47][48][49] Experiments which highlighted the importance of monolayer adaptability included calcium oxalate grown under phospholipid films; [50][51][52] hydroxyapatite under fatty acids; 53 observations by Brewster Angle Microscopy of mineralization at domain boundaries of Langmuir films, where it can be argued that molecules shift to accommodate crystal nuclei; 54,55 and computational studies.…”