Thermally Driven Self‐Assembly of Nanomicelles: A Facile Route to Functional Monodisperse Mesoporous Colloidal Nanocomposites of Inorganic Nature and Mesoscale Size

Thermally driven self‐assembly of nanomicelles can be a feasible route to produce monodisperse porous colloidal nanocomposites of inorganic nature and sizes around the mesoscale (below 100 nm). Success relies on extending the lifetime of intermediate droplets (size below about 100 nm) that are obtained under particular conditions. Herein, the conditions for the long‐term stabilization of these unique templates are studied and a model proposed to produce monodisperse porous colloidal nanocomposites. As an example of the potential applications of this methodology, functional colloidal nanocomposites with a high loading of the doping material (30 mol%) are obtained. In particular, superparamagnetic nanomagnets of metallic nature encapsulated in porous oxide colloidal matrixes of mesoscale size that easily respond to an external magnetic field are prepared and characterized in terms of structure and textural and magnetic properties.     

Bionanocomposites: A New Concept of Ecological,Bioinspired, and Functional Hybrid Materials

Bionanocomposites represent an emerging group of nanostructured hybrid materials. They are formed by the combination of natural polymers and inorganic solids and show at least one dimension on the nanometer scale. Similar to conventional nanocomposites, which involve synthetic polymers, these biohybrid materials also exhibit improved structural and functional properties of great interest for different applications. The properties inherent to the biopolymers, that is, biocompatibility and biodegradability, open new prospects for these hybrid materials with special incidence in regenerative medicine and in environmentally friendly materials (green nanocomposites). Research on bionanocomposites can be regarded as a new interdisciplinary field closely related to significant topics such as biomineralization processes, bioinspired materials, and biomimetic systems. The upcoming development of novel bionanocomposites introducing multifunctionality represents a promising research topic that takes advantage of the synergistic assembling of biopolymers with inorganic nanometer‐sized solids.     

Virus Matryoshka: A Bacteriophage Particle—Guided Molecular Assembly Approach to a Monodisperse Model of the Immature Human Immunodeficiency Virus

Immature human immunodeficiency virus type 1 (HIV‐1) is approximately spherical, but is constructed from a hexagonal lattice of the Gag protein. As a hexagonal lattice is necessarily flat, the local symmetry cannot be maintained throughout the structure. This geometrical frustration presumably results in bending stress. In natural particles, the stress is relieved by incorporation of packing defects, but the magnitude of this stress and its significance for the particles is not known. In order to control this stress, we have now assembled the Gag protein on a quasi‐spherical template derived from bacteriophage P22. This template is monodisperse in size and electron‐transparent, enabling the use of cryo‐electron microscopy in structural studies. These templated assemblies are far less polydisperse than any previously described virus‐like particles (and, while constructed according to the same lattice as natural particles, contain almost no packing defects). This system gives us the ability to study the relationship between packing defects, curvature and elastic energy, and thermodynamic stability. As Gag is bound to the P22 template by single‐stranded DNA, treatment of the particles with DNase enabled us to determine the intrinsic radius of curvature of a Gag lattice, unconstrained by DNA or a template. We found that this intrinsic radius is far larger than that of a virion or P22‐templated particle. We conclude that Gag is under elastic strain in a particle; this has important implications for the kinetics of shell growth, the stability of the shell, and the type of defects it will assume as it grows.     

Combining X‐Ray Whole Powder Pattern Modeling,Rietveld and Pair Distribution Function Analyses as a Novel Bulk Approach to Study Interfaces in Heteronanostructures: Oxidation Front in FeO/Fe3O4 Core/Shell Nanoparticles as a Case Study

Understanding the microstructure in heterostructured nanoparticles is crucial to harnessing their properties. Although microscopy is ideal for this purpose, it allows for the analysis of only a few nanoparticles. Thus, there is a need for structural methods that take the whole sample into account. Here, a novel bulk‐approach based on the combined analysis of synchrotron X‐ray powder diffraction with whole powder pattern modeling, Rietveld and pair distribution function is presented. The microstructural temporal evolution of FeO/Fe₃O₄ core/shell nanocubes is studied at different time intervals. The results indicate that a two‐phase approach (FeO and Fe₃O₄) is not sufficient to successfully fit the data and two additional interface phases (FeO and Fe₃O₄) are needed to obtain satisfactory fits, i.e., an onion‐type structure. The analysis shows that the Fe₃O₄ phases grow to some extent (≈1 nm) at the expense of the FeO core. Moreover, the FeO core progressively changes its stoichiometry to accommodate more oxygen. The temporal evolution of the parameters indicates that the structure of the FeO/Fe₃O₄ nanocubes is rather stable, although the exact interface structure slightly evolves with time. This approach paves the way for average studies of interfaces in different kinds of heterostructured nanoparticles, particularly in cases where spectroscopic methods have some limitations.