  Ion complexes hold the key for various energy transfer and communication
systems in nature and industries. Achieving controllable mechanical and
electrical properties in these complex systems is highly desirable but remains
challenging. In this work, we propose the use of amphiphilic molecules to
mediate salt crystallization. The resultant ionic interfaces can be tunable
through reduced surface tensions of crystal facets, an additional
intermolecular modifier, and the diffusion-limited crystallization during
controlled solvent evaporation. Specifically, we utilized the ionic surfactant
Sodium Lauryl sulfoacetate (SLSA) to mediate the crystallization of sodium
chloride. Citric acid (CA) was adopted as a hydrogen-bond modifier. Systems
mediated by SLSA exhibited the highest capacitance, and a significant
enhancement of capacitance was also observed in systems with both SLSA and CA.
The substantially increased capacitance of these ionic complexes can be
attributed to changes in interfacial and crystalline grain structures.
Transmission electron microscopy (TEM), optical microscopy (OM), and Finite
Element Analysis (FEA) were used to study the effects of surfactant molecules
in these ionic complexes. Understanding the role of ionic complexation in
defining the thermodynamic and kinetic process of the crystallization process
will contribute to better optimization in nucleation and scalability of organic
and inorganic crystal production.
