Insights into the Self-Assembly of a Heterocluster Janus Molecule into Colloidal Onions

Abstract

Diverse nanostructures and nano-objects for advanced applications are created by the self-assembly of lipids, surfactants, and block copolymers. Understanding this process is critical for improving their functions and expanding their applications. Accordingly, we pioneered the synthesis and application of heterocluster Janus molecules (HCJMs), which resemble conventional amphiphiles. Their self-assembly into nanostructures and nano-objects can be directly characterized by transmission electron microscopy (TEM), allowing the process to be unraveled through the monitoring of the intermediates. In this study, we focused on the TEM characterization of HCJM-based colloidal onions, which have an onion-like inner structure, to gain insight into the self-assembly process from molecules to perfect onions. Multiple mechanisms, including molecular aggregation, structural ordering within aggregates into colloidal onions, and layer-by-layer growth caused by particle coarsening, contributed to the overall self-assembly process. The analysis also indicated that the reduction in the Gibbs free energy and bending free energy of curved layers are the driving forces for structural ordering and onion growth. Finally, this work provided a useful method for preparing colloidal onions for attractive applications in nanomedicine and other areas.

Polyoxometalate Clusters: Sub-nanometer Building Blocks for Construction of Advanced Materials

“…Later they synthesized another POM-ABPOSS cluster, which is formed by POM, heptaphenyl POSS, and heptaisobutyl POSS clusters. 115 In acetone/water mixture, the Janus clusters could aggregate into colloidal onions with wide-ranging size distribution, and the onion-like structure could reach up to 100 nm with 18 layers.…”

Continuous Curvature Change into Controllable and Responsive Onion-like Vesicles by Rigid Sphere–Rod Amphiphiles

“…Formed by amphiphilic molecules such as phospholipids and block copolymers, vesicles are one of the most fundamental nanostructures in natural and artificial processes. − Over the past decades, the vesicular structures have shown attractive properties and drawn much attention in various fields such as supramolecular chemistry, − chemical reaction, , imaging, and simulation. − In addition to common hollow vesicles (with one bilayer membrane), amphiphiles are also found to form interesting onion-like vesicles (multilayered vesicles) which consist of concentric alternating bilayers, and the observations of onion-like vesicles have been extensively reported in various systems including small-molecule surfactants, − block copolymers, − dendrimers, − surfactant-encapsulated complexes, and cluster-based hybrids − and also elucidated by simulations. , Although the formation of onion-like vesicles can enrich supramolecular structures in amphiphilic systems, a microscopic mechanism to reveal their self-assembly process is still not fully understood, especially, why some amphiphiles can form onion-like vesicles while others cannot. Additionally, the size of onion-like vesicles and their layer number are usually difficult to control and exhibit significant polydispersity in solution.…”

Chiral three-dimensional supramolecular assemblies: colloidal onions, cubosomes, and hexosomes

“…The POM and POSS clusters are the same as those used in our previous studies. 14–22 The design and synthesis of the chiral and achiral heteroclusters shown in Fig. 1A were reported in our previous study.…”