The preparation of hexagonally ordered metallic nanodots was studied in detail with emphasis on the chemical state of the resulting particles. To obtain these dots, in a first step micellar structures were formed from diblock copolymers in solution. The reverse micelles themselves are capable of ligating defined amounts of a metal salt within their cores, acting as nanoreactors. After transfer of the metal‐loaded reverse micelles onto a substrate, the polymer was removed by means of different plasmas (oxygen and/or hydrogen), which also allow the metal salt to be reduced to the metallic state. In this way, ordered arrays of metallic nanodots can be prepared on various substrates. By adjusting the appropriate parameters, the separation and the size of the dots can be varied and controlled. To determine their purity, chemical state, and surface cleanliness—all of which are crucial for subsequent experiments since nanoscale structures are intrinsically surface dominated—in‐situ X‐ray photoelectron spectroscopy (XPS) and ex‐situ transmission electron microscopy (TEM) were applied, also giving information on the formation of the nanodots.

Starting with Co‐salt‐loaded inverse micelles, which form if the diblock copolymer polystyrene‐block‐poly(2‐vinylpyridine) is dissolved in a selective solvent like toluene and CoCl2 is added to the solution, monomicellar arrays of such micelles exhibiting a significant hexagonal order can be prepared on top of various substrates with tailored intermicellar distances and structure heights. In order to remove the polymer matrix and to finally obtain arrays of pure Co nanoparticles, the micelles are first exposed to an oxygen plasma, followed by a treatment in a hydrogen plasma. Applying in‐situ X‐ray photoelectron spectroscopy, it is demonstrated that: 1) The oxygen plasma completely removes the polymer, though conserving the original order of the micellar array. Furthermore, the resulting nanoparticles are entirely oxidized with a chemical shift of the Co 2p3/2 line pointing to the formation of Co3O4. 2) By the subsequent hydrogen plasma treatment the nanoparticles are fully reduced to metallic Co. 3) By exposing the pure Co nanoparticles for 100 s to various oxygen partial pressures p, a stepwise oxidation is observed with a still metallic Co core surrounded by an oxide shell. The data allow the extraction of the thickness of the oxide shell as a function of the total exposure to oxygen (p × time), thus giving the opportunity to control the ferromagnetic–antiferromagnetic composition of an exchange‐biased magnetic system.

One of the most important elements of a luminescent solar concentrator (LSC) is the host material. In this work, we investigate the key optical properties of eight polymeric host matrices. Poly(methyl methacrylate) (PMMA) and polycarbonate (PC) based formulations exhibited the lowest internal absorbance within the spectral range of the absorption and emission bands of a red‐emitting fluorescent organic dye (Lumogen Red 305). The dye absorbance was dependent on the host matrix and was higher for the PC‐based formulations than the other polymers. However, two different doping concentrations were used, and the higher concentration led to the absorption of more than 90 % of the incident photons within the absorption band of the dye in all cases. The overall optical efficiency with respect to edge emission from 60 mm×60 mm×3.2 mm LSCs varied within an absolute value of 1 % for the eight host matrices investigated. The best result achieved in terms of optical efficiency was 8.9 % for PMMA‐ and PC‐based hosts.

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