Understanding and Analyzing Freezing-Point Transitions of Confined Fluids within Nanopores

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• 作者：Steven Shimizu ; Kumar Varoon Agrawal ; Marcus O鈥橫ahony ; Lee W. Drahushuk ; Neha Manohar ; Allan S. Myerson ; Michael S. Strano
• 刊名：Langmuir
• 出版年：2015
• 出版时间：September 22, 2015
• 年：2015
• 卷：31
• 期：37
• 页码：10113-10118
• 全文大小：390K
• ISSN：1520-5827

文摘

Understanding phase transitions of fluids confined within nanopores is important for a wide variety of technological applications. It is well known that fluids confined in nanopores typically demonstrate freezing-point depressions, 螖T_f, described by the Gibbs鈥揟homson (GT) equation. Herein, we highlight and correct several thermodynamic inconsistencies in the conventional use of the GT equation, including the fact that the enthalpy of melting, 螖H_m, and the solid鈥搇iquid surface energy, 纬_SL, are functions of pore diameter, complicating their prediction. We propose a theoretical analysis that employs the Turnbull coefficient, originally derived from metal nucleation theory, and show its consistency as a more reliable quantity for the prediction of 螖T_f. This analysis provides a straightforward method to estimate 螖T_f of nanoconfined organic fluids. As an example, we apply this technique to ibuprofen, an active pharmaceutical ingredient (API), and show that this theory fits well to the experimental 螖T_f of nanoconfined ibuprofen.