Interfacial Concentration Effect Facilitates Heterogeneous Nucleation from Solution

Abstract

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.

Influence of Volume on the Nucleation of Model Organic Molecular Crystals through an Induction Time Approach

“…Additionally, starting around the 100–150 min mark, all curves taper off. This tapering-off of the cumulative probability distribution was also observed in other induction time studies involving microscopy and image analysis, possibly due to a microscope or a camera’s limited detection capabilities. ,− Thus, nucleation kinetics was calculated using the first linear portion of the probability distribution, which follows a Poisson distribution. The regime for the early time points presents a steep slope and thus a high nucleation rate as defined by theories.…”

Tuning Interfacial Concentration Enhancement through Dispersion Interactions to Facilitate Heterogeneous Nucleation

“…The position and magnitude of the peaks in the P 2 values show excellent agreement between the two simulated systems, demonstrating that the LJ 9-3 wall successfully matches the structural details of the fully atomistic interface. We see stronger alignment with the solid surfaces than was observed in the previous liquid tridecane simulations, 13 suggesting that the mobile liquid–liquid tridecane–solution interfaces also obscure, or disrupt, the ordering of the molecules.…”

“…The layering seen in the density profiles in Figure 4 was not observed in the previous simulations of the glycine solution at a mobile, liquid–liquid tridecane–solution interface. 13 This layering is due to the fixed, flat nature of the interfaces in the present work. Our analysis of density profiles does not account for capillary waves and interfacial fluctuations that are present in the liquid–liquid interface and as such the density at the fluctuating surface is smeared.…”

“…It is possible that the layering would become clearer using more advanced interfacial analysis techniques, such as the generalized identification algorithm for non-planar interfaces. 29 To provide further insights into the effects of liquid–liquid versus solid–liquid interfaces on the obtained density profiles, a simulation of a film of glycine solution at 307 g/kg (the same solution that was simulated in the previous work 13 ) was carried out in contact with frozen liquid tridecane (an amorphous, solid surface). This frozen, amorphous surface acts as an intermediate step between the fully liquid and crystalline tridecane surfaces.…”

Surface-Induced Crystallization of Sodium Dodecyl Sulfate (SDS) Micellar Solutions in Confinement

“…(c) Induction time t i measurements vs contact angle of water on different surfaces at T f = 4 °C. Average surface free energy values reported in the literature are provided as a reference. − Images show wetting conditions for DI water droplets on the different tested substrates.…”