Functional Nano-Objects by Electrostatic Self-Assembly: Structure, Switching, and Photocatalysis

Abstract

The design of functional nano-objects by electrostatic self-assembly in solution signifies an emerging field with great potential. More specifically, the targeted combination of electrostatic interaction with other effects and interactions, such as the positioning of charges on stiff building blocks, the use of additional amphiphilic, π−π stacking building blocks, or polyelectrolytes with certain architectures, have recently promulgated electrostatic self-assembly to a principle for versatile defined structure formation. A large variety of architectures from spheres over rods and hollow spheres to networks in the size range of a few tenths to a few hundred nanometers can be formed. This review discusses the state-of-the-art of different approaches of nano-object formation by electrostatic self-assembly against the backdrop of corresponding solid materials and assemblies formed by other non-covalent interactions. In this regard, particularly promising is the facile formation of triggerable structures, i.e. size and shape switching through light, as well as the use of electrostatically assembled nano-objects for improved photocatalysis and the possible solar energy conversion in the future. Lately, this new field is eliciting an increasing amount of understanding; insights and limitations thereof are addressed in this article. Special emphasis is placed on the interconnection of molecular building block structures and the resulting nanoscale architecture via the key of thermodynamics.

Entropic Origin of Ionic Interactions in Polar Solvents

“…The implications of these conclusions are important since assembly in charged systems is ubiquitous. − For instance, in drug discovery, researchers often discuss enthalpy–entropy compensation, where a strong enthalpic interaction between two species (i.e., protein–ligand) invariably comes with an equivalent entropic compensation. As reemphasized by Dragan et al, a significant part of this entropy likely comes from the solvent release.…”

Polythiophene as a Double-Electrostatic Template for Zinc Oxide and Gold: Multicomponent Nano-Objects for Enhanced Photocatalysis

“…Further, the catalytic properties of metal oxides and metal nanoparticles can be optimized via morphology, size, and crystal arrangement. ,− Surface-modifying substances, especially macromolecules, are powerful in controlling the morphology. ,− In particular, electrostatic nanotemplating directs precursor ions into an organic polyelectrolyte template, followed by a chemical reaction resulting in well-defined inorganic nanoparticles inside of the template . First established by Antonietti et al, polyelectrolyte microgel templating of gold or iron oxide resulted in stable colloidal solutions with gold in nugget and thread shapes, after which multiple polymers have been studied. ,− For successful catalysis, a balance of stabilizing coverage and accessibility of the catalytically active surface is essential. , Recently, a combination of electrostatic templating and a biomimetic approach has been used to create two different separated particles with a double-hydrophilic copolymer …”

“…16,35−37 In particular, electrostatic nanotemplating directs precursor ions into an organic polyelectrolyte template, followed by a chemical reaction resulting in well-defined inorganic nanoparticles inside of the template. 12 Antonietti et al, polyelectrolyte microgel templating of gold or iron oxide resulted in stable colloidal solutions with gold in nugget and thread shapes, 23 after which multiple polymers have been studied. 15,38−41 For successful catalysis, a balance of stabilizing coverage and accessibility of the catalytically active surface is essential.…”

Hierarchical electrostatic nanotemplating and self-assembly of electron-transferring hybrid nanostructures: CdS–polymer–porphyrin particles

“…Whether or not precipitation through interconnection occurs, in electrostatic self-assembly strongly depends on the interplay of interactions and ratio of the components. 40 In particular, in electrostatic self-assembly of polyelectrolytes with stiff multivalent counterions.…”