Coordination Cage-Based Emulsifiers: Templated Formation of Metal Oxide Microcapsules Monitored by In Situ LC-TEM

Area of Science:

• Supramolecular Chemistry
• Materials Science
• Nanotechnology

Background:

• Metallo-supramolecular self-assembly has produced various nanosystems for guest capture and catalysis.
• The application of low-molecular bottom-up self-assemblies for structured inorganic materials remains underexplored.

Purpose of the Study:

• To introduce a novel metallo-supramolecular surfactant for stabilizing non-aqueous emulsions.
• To utilize these emulsions for synthesizing metal oxide microcapsules and hollow microspheres.

Main Methods:

• Design and synthesis of a heteroleptic coordination cage surfactant (CGA-3) based on Pd(II) cations.
• Stabilization of non-aqueous emulsions (hexadecane-in-DMSO) using the synthesized surfactant.
• Emulsion-templated synthesis of titanium, zirconium, and niobium oxide microcapsules.
• In situ liquid cell transmission electron microscopy (LC-TEM) for dynamic visualization.

Main Results:

• The metallo-supramolecular surfactant (CGA-3) effectively stabilizes non-aqueous emulsions.
• Spherical metal oxide microcapsules (TiO2, ZrO2, Nb2O5) were synthesized from water-sensitive alkoxide precursors.
• LC-TEM provided the first in situ visualization of hollow inorganic microsphere formation within emulsions.

Conclusions:

• Metallo-supramolecular surfactants offer a new route to structured inorganic materials.
• Emulsion templating with these surfactants is a versatile method for microcapsule synthesis.
• In situ LC-TEM is a powerful tool for studying dynamic self-assembly processes in liquid media.