McKechnie David, Anker Samira, Zahid Saraf, Mulheran Paul A, Sefcik Jan, Johnston Karen
Department of Chemical and Process Engineering, University of Strathclyde, 75 Montrose Street, Glasgow G1 1XJ, U.K.
Doctoral Training Centre in Continuous Manufacturing and Advanced Crystallisation, University of Strathclyde, Glasgow G1 1RD, U.K.
J Phys Chem Lett. 2020 Mar 19;11(6):2263-2271. doi: 10.1021/acs.jpclett.0c00540. Epub 2020 Mar 6.
Crystal nucleation from solution plays an important role in environmental, biological, and industrial processes and mainly occurs at interfaces, although the mechanisms are not well understood. We performed nucleation experiments on glycine aqueous solutions and found that an oil-solution interface dramatically accelerates glycine nucleation compared to an air-solution interface. This is surprising given that nonpolar, hydrophobic oil (tridecane) would not be expected to favor heterogeneous nucleation of highly polar, hydrophilic glycine. Molecular dynamics simulations found significantly enhanced vs depleted glycine concentrations at the oil-solution vs air-solution interfaces, respectively. We propose that this interfacial concentration effect facilitates heterogeneous nucleation, and that it is due to dispersion interactions. This interface effect is distinct from previously described mechanisms, including surface functionalization, templating, and confinement and is expected to be present in a wide range of solution systems. This work provides new insight that is essential for understanding and controlling heterogeneous nucleation.
溶液中的晶体成核在环境、生物和工业过程中起着重要作用，主要发生在界面处，但其机制尚未完全明确。我们对甘氨酸水溶液进行了成核实验，发现油-溶液界面相比于气-溶液界面能显著加速甘氨酸的成核。鉴于非极性、疏水性的油（十三烷）预计不会促进高极性、亲水性的甘氨酸的异相成核，这一结果令人惊讶。分子动力学模拟分别发现，在油-溶液界面处甘氨酸浓度显著增强，而在气-溶液界面处则有所降低。我们认为这种界面浓度效应促进了异相成核，并且这是由于色散相互作用所致。这种界面效应与先前描述的机制不同，包括表面功能化、模板化和受限效应，预计在广泛的溶液体系中都存在。这项工作为理解和控制异相成核提供了至关重要的新见解。
