Most studies on the synthesis of nanoparticles are currently focused on the controlled synthesis of new morphologies, including core-shell structures, which are expected to exhibit new magnetic properties for uses in spintronics and recording media applications. In this study, the structure, morphology, and composition of cubic-shaped nanoparticles are carefully investigated and compared to those of spherically shaped nanoparticles through the use of a combination of techniques: X-ray diffraction (XRD) and transmission electronic microscopy (TEM) combined with more sensitive techniques such as scanning transmission electron microscopy-high-angle annular dark field (STEM-HAADF) imaging, electron tomography, and holography. While spherically shaped nanoparticles (NPs) crystallize with the spinel structure, cubic-shaped NPs can be described as a cubic core of w€ ustite surrounded by a spinel shell. Stresses are observed at the core-shell interface and within the spinel shell due to the epitaxial growth and oxidation mechanisms of the w€ ustite phase. Furthermore, magnetic measurements displayed an exchange bias coupling between the antiferromagnetic (AFM) core and the ferrimagnetic (FIM) shell structure of cubic-shaped nanoparticles. It is shown that the magnetic properties are influenced by stresses generated by the oxidation of w€ ustite and, also exhibit variations depending upon the evolution of this core-shell structure as a function of the oxidation time.

Microdroplets for nanoparticles: An extremely reliable method to create droplet pairs, based on hydrodynamic coupling of two spatially separated nozzles, has been developed. Droplets containing the reagents for the precipitation of iron oxide are electrocoalesced to synthesize iron oxide nanoparticles in a very fast (millisecond‐scale) and reproducible reaction (see picture).

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The coupling of atmospheric pressure ionization (API) sources like electrospray ionization (ESI) to vacuum based applications like mass spectrometry (MS) or ion beam deposition (IBD) is done by differential pumping, starting with a capillary or pinhole inlet. Because of its low ion transfer efficiency the inlet represents a major bottleneck for these applications. Here we present a nano-ESI vacuum interface optimized to exploit the hydrodynamic drag of the background gas for collimation and the reduction of space charge repulsion. Up to a space charge limit of 40 nA we observe 100% current transmission through a capillary with an inlet and show by MS and IBD experiments that the transmitted ion beams are well defined and free of additional contamination compared to a conventional interface. Based on computational fluid dynamics modelling and ion transport simulations, we show how the specific shape enhances the collimation of the ion cloud. Mass selected ion currents in the nanoampere range available further downstream in high vacuum open many perspectives for the efficient use of electrospray ion beam deposition (ES-IBD) as a surface coating method.

The present article focuses on the build-up and the properties of oriented silver nanowire monolayer films and Layer-by-Layer assembled multilayer films. We describe the template-free oriented spray-assisted assembly of silver nanowires at solid/air-interfaces using Grazing Incidence Spraying, a simple and versatile approach that allows the formation of highly oriented thin films with a tunable density and in-plane orientation. Depending on the spraying conditions the nematic order parameter, which describes the angular spread of misaligned nanowires, can be as high as 0.98 (a value of 1.00 corresponding to a perfectly parallel alignment). The combination with the Layer-by-Layer assembly allows building multilayer thin films possessing in-plane anisotropy. In order to demonstrate that the local alignment does not cancel out on the macroscopic scale but leads to direction-dependent properties, we use linearly polarized UV-Vis-NIR spectroscopy to probe the selective excitation of the transverse and longitudinal localized plasmon resonances of the nanowires. The polarization efficiency of the thin films increases strongly with the in-plane density, the degree of orientation, and the number of silver nanowire layers. Multilayer films containing 4 layers of nanowires oriented in the same direction reach a polarization efficiency of up to 97% in the near-infrared region.

Self-assembly of nanoparticles (NPs) into tailored structures is a promising strategy for the production and design of materials with new functions. In this work, 2D arrays of iron oxide NPs with interparticle distances tuned by grafting fatty acids and dendritic molecules at the NPs surface have been obtained over large areas with high density using the Langmuir-Blodgett technique. The anchoring agent of molecules and the Janus structure of NPs are shown to be key parameters driving the deposition. Finally the influence of interparticle distance on the collective magnetic properties in powders and in monolayers is clearly demonstrated by DC and AC SQUID measurements. The blocking temperature T(B) increases as the interparticle distance decreases, which is consistent with the fact that dipolar interactions are responsible for this increase. Dipolar interactions are found to be stronger for particles assembled in thin films compared to powdered samples and may be described by using the Vogel Fulcher model.

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This review presents the main techniques employed to construct chiral plasmonic materials and metasurfaces, in particular using soft-chemistry approaches, and discusses some applications of these nanostructures.