One-Pot Aqueous Solution Syntheses of Iron Oxide Nanostructures with Controlled Crystal Phases through a Microbial-Mineralization-Inspired Approach

Assembly of Protein Stacks With in Situ Synthesized Nanoparticle Cargo

The ability of proteins to form hierarchical structures through self-assembly provides an opportunity to synthesize and organize nanoparticles. Ordered nanoparticle assemblies are a subject of widespread interest due to the potential to harness their emergent functions. In this work, the toroidal-shaped form of the protein peroxiredoxin, which has a pore size of 7 nm, was used to organize iron oxyhydroxide nanoparticles. Iron in the form of Fe²⁺ was sequestered into the central cavity of the toroid ring using metal-binding sites engineered there and then hydrolyzed to form iron oxyhydroxide particles bound into the protein pore. By precise manipulation of the pH, the mineralized toroids were organized into stacks confining one-dimensional nanoparticle assemblies. We report the formation and the procedures leading to the formation of such nanostructures and their characterization by chromatography and microscopy. Electrostatic force microscopy clearly revealed the formation of iron-containing nanorods as a result of the self-assembly of the iron-loaded protein. This research bodes well for the use of peroxiredoxin as a template with which to form nanowires and structures for electronic and magnetic applications.

Incorporation of organic crystals into the interspace of oriented nanocrystals: morphologies and properties

Oriented nanocrystals, as seen in biominerals, have both the macroscopic hierarchical morphologies and the nanoscale interspace among the unit crystals. Here we studied the incorporation effects of the specific interspace in the oriented nanocrystals on the morphologies, properties, and applications of organic crystals. Organic crystals, such as 9-vinylcarbazole (VCz), azobenzene (AB), and pyrene (PY), were introduced into the specific interspace of oriented nanocrystals from the melts. The morphologies and properties of the incorporated organic crystals were systematically studied in these model cases. The incorporation of the organic crystals provided the composites with the original oriented nanocrystals. The incorporated organic crystals formed the single-crystalline structures even in the nanoscale interspace. The melts of the organic compounds were crystallized and grown in the interspace of the original materials. The incorporated organic crystals showed the specific phase transition behavior. The freezing points of the organic crystals were raised by the incorporation into the nanospace while the melting points were not changed. The hierarchical morphologies of the organic crystals were obtained after the dissolution of the original materials. The hierarchical morphologies of the original materials were replicated to the organic crystals. The incorporated organic crystal was polymerized without deformation of the hierarchical morphologies. The hierarchical polymer can be applied to the donor material for the generation of a larger amount of the charge-transfer complex with the acceptor molecule than the commercial polymer microparticles. The present work shows the potential use of the nanoscale interspace generated in the oriented nanocrystals.

Controlled radical polymerization of styrene with magnetic iron oxides prepared through hydrothermal, bioinspired, and bacterial processes

Controlled/living radical polymerization of styrene proceeded with the use of magnetic iron oxide (Fe₃O₄) prepared through various processes.

Effects of organic polymer addition in magnetite synthesis on the crystalline structure

Various polymers with different functional groups and surface charges were added to the precursor solution of Fe₃O₄ to clarify the relationship between the chemical structure of the organic substances and the crystal structure of Fe₃O₄.