Spontaneous organization of supracolloids into three-dimensional structured materials

(Nanowerk News) Researchers of nanotechnology at the Eindhoven University of Technology reported a three-dimensional structured material achieved through supracolloids assembly. The key to this achievement is revealed through extensive analysis of the hybrid colloidal self-assembly using advanced cryogenic electron microscopy at the Centre for Multi-scale Electron Microscopy (CMEM).
This organic-inorganic hybrid material formation can ease the development of multi-component nanomaterials for optoelectronics, energy materials, membrane filtration, nanocatalysts and bioinspired materials.
3D Tomographic views of the whole, bottom, top and middle surface (left to right) of the stable supracolloids in a drying process approaching a hexagonal structure
3D Tomographic views of the whole, bottom, top and middle surface (left to right) of the stable supracolloids in a drying process approaching a hexagonal structure. Cryogenic electron microscopy snapshots showed a promised order in the final material. (Image: Eindhoven University of Technology)
Hybrid supracolloids were synthesized from charge-switchable silica nanoparticles and three to five times larger oppositely charged polymer spheres. When switching the silica charge by dropping the pH, the silica and polymer spheres usually cluster and form a gel. By controlling the ratio of the components, their charge density and the ionic strength, supracolloids can be formed that remain dispersed with increasing concentration during drying.
The supracolloids reorganized only upon close contact. The reorganization space was limited to the voids between them, thereby not disturbing the emerging hexagonal packing of the supracolloids.
The method was verified for different size ratios of the particles and two different types of polymer spheres. After polymer removal by a temperature treatment, the silica particles structure remains stable, implying that structured porosity in a silica network can be realized. Such a structured porous network offers options for optical properties, membranes and filters.
The scientists hypothesize that by adding still one more component to this system, its modularity and complexity can be further tuned.
In collaboration with Utrecht University and Cambridge University, the results of this research are published in Nature Materials ("Spontaneous organization of supracolloids into three-dimensional structured materials").
Source: Eindhoven University of Technology
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