The organization of inorganic nanostructures within self-assembled organic or biological templates is receiving the attention of scientists interested in developing functional hybrid materials. Previous efforts have concentrated on using such scaffolds to spatially arrange nanoscopic elements as a strategy for tailoring the electrical, magnetic or photonic properties of the material. Recent theoretical arguments have suggested that synergistic interactions between self-organizing particles and a self-assembling matrix material can lead to hierarchically ordered structures. Here we show that mixtures of diblock copolymers and either cadmium selenide- or ferritin-based nanoparticles exhibit cooperative, coupled self-assembly on the nanoscale. In thin films, the copolymers assemble into cylindrical domains, which dictate the spatial distribution of the nanoparticles; segregation of the particles to the interfaces mediates interfacial interactions and orients the copolymer domains normal to the surface, even when one of the blocks is strongly attracted to the substrate. Organization of both the polymeric and particulate entities is thus achieved without the use of external fields, opening a simple and general route for fabrication of nanostructured materials with hierarchical order.

Developments in the assembly of nanoparticles at liquid-liquid interfaces are reviewed where the assemblies can be controlled by tuning the size of the nanoparticles and the chemical characteristics of the ligands. Both synthetic and biological nanoparticles are discussed. By controlling the type of ligands, uniform and Janus-type nanoparticles can be produced where, at liquid-liquid interfaces, subsequent reactions of the ligands can be used to generate crosslinked sheets of nanoparticles at the interface that have applications including novel encapsulants, filtration devices with well-defined porosities, and controlled release materials. By controlling the size and volume fraction of the nanoparticles and the chemical nature of the ligands, nanoparticle-polymer composites can be generated where either enthalpy or entropy can be used to control the spatial distribution of the nanoparticles, thereby, producing auto-responsive materials that self-heal, self-corral assemblies of nanoparticles, or self-direct morphologies. Such systems hold great promise for generating novel optical, acoustic, electronic and magnetic materials.

Thin-film membranes consisting of nanoparticles are of interest in applications ranging from nanosieves to electric, magnetic, or photonic devices and sensors. However, the fabrication of large-scale membranes in a simple but controlled way has remained a challenge, due to the limited understanding of their mechanical properties. Systematic experiments on ultrathin, freestanding nanoparticle membranes of different core materials, core sizes, and capping ligands are reported. The results demonstrate that a drying-mediated self-assembly process can be used to create close-packed monolayer membranes that span holes tens of micrometers in diameter. Containing up to approximately 10(7) particles, these freely suspended layers exhibit remarkable mechanical properties with Young's moduli of the order of several GPa, independent of membrane size. Comparison of three different core-ligand combinations suggests that the membrane's elastic response is set by how tightly the ligands are bound to the particle cores and by the ligand-ligand interactions.

We investigate the concentration and size dependent self-assembly of cadmium selenide nanoparticles at an oil/water interface. Using a pendant drop tensiometer, we monitor the assembly kinetics and evaluate the effective diffusion coefficients following changes in the interfacial tension for the early and late stages of nanoparticle adsorption. Comparison with the coefficients for free diffusion reveals the energy barrier for particle segregation to the interface. The formation of a nanoparticle monolayer at the oil/water interface is characterised by transmission electron microscopy.

Bionanoparticles, such as the cowpea mosaic virus, can stabilize oil droplets in aqueous solutions by self‐assembly at liquid interfaces. Subsequent cross‐linking of the bionanoparticles transforms the assemblies into robust membranes that have covalent inter‐bionanoparticle connections. The resulting membranes are nanoscopically thin sheets (see SANS image (SANS=small‐angle neutron scattering)), which were examined by fluorescent labeling.