Determining nonuniformities of core-shell nanoparticle coatings by analysis of the inelastic background of X-ray photoelectron spectroscopy survey spectra

Most real core-shell nanoparticle (CSNP) samples deviate from an ideal core-shell structure potentially having significant impact on the particle properties. An ideal structure displays a spherical core fully encapsulated by a shell of homogeneous thickness, and all particles in the sample exhibit the same shell thickness. Therefore, analytical techniques are required that can identify and characterize such deviations. This study demonstrates that by analysis of the inelastic background in X-ray photoelectron spectroscopy (XPS) survey spectra, the following types of deviations can be identified and quantified: the nonuniformity of the shell thickness within a nanoparticle sample and the incomplete encapsulation of the cores by the shell material. Furthermore, CSNP shell thicknesses and relative coverages can be obtained. These results allow for a quick and straightforward comparison between several batches of a specific CSNP, different coating approaches, and so forth. The presented XPS methodology requires a submonolayer distribution of CSNPs on a substrate. Poly(tetrafluoroethylene)-poly(methyl methacrylate) and poly(tetrafluoroethylene)-polystyrene polymer CSNPs serve as model systems to demonstrate the applicability of the approach.     

About the fluorine chemistry in MCVD: The mechanism of fluorine incorporation into SiO2 layers

Fluorine incorporation during the deposition of silica layers is studied under MCVD conditions using C₂F₃Cl₃ as fluorine source. The experimental results are compared with known models of the incorporation mechanism. It is found that a gas/solid equilibrium during the consolidation step determines the final fluorine content of the layers.     

Time-resolved imaging of hydrogel printing via laser-induced forward transfer

In this work, the printing mechanism of an alginate-based hydrogel via laser-induced forward transfer (LIFT) is investigated by spatial and temporal high-resolved stroboscopic imaging. First, the generation of the liquid jet is studied at two different laser fluences in a process without collector slide. Furthermore, the impingement process onto the collector slide at the same fluence levels is observed. With the help of these images the development of the jet is explained. Besides the influences of the collector slide as well as the applied laser fluence on the transfer are demonstrated.     

Untersuchungen zur Struktur von 1,1-Komplexen der Nickelhalogenide mit N-substituierten Aminomethyl- und Aminoäthylpyridinen

The 1.1-complexes formed by the reaction of nickel(II) halides and substituted aminoethyl- and aminomethyl-pyridines-(2) may be divided into two groups. Compounds, which are yellow or red brown in the solid state, and violet in solution in acetone belong to the first group. The complexes of the second group are violet in solution and in the solid state. On account of the vis- and ir-spectra, the magnetic behaviour, and the molar weight a distorted tetrahedral structure is discussed for the violet compounds, and a dimeric structure with coordination number 5 of the central atom for the complexes of the first group. The factors determining the structure of the investigated compounds are stated.     

Magnetization reversal of CuyCr2Se4−zBrx single crystals

Due to a partially inhomogeneous Cu concentration, Cu_yCr₂Se_4?zBr_x single crystal can show a complicated temperature dependence of the wall motion threshold field which is about 0.5 kA/m near the Curie temperature. The crystals can be homogenized by means of a NH₄OH treatment.     

Raman and infrared spectra of CdIn2S4 and ZnIn2S4

Four one-phonon Raman lines have been found in CdIn₂S₄ (ZnIn₂S₄) spinels at 92 (72) cm^-1, 186 (184) cm^-1, 246 (253) cm^-1, and 367 (372) cm^-1 for incident photon energies well below the energy gap E_G ～ 2.4 (2.2) eV at 300 K. For photon energies close to E_G, the 367 cm^-1 mode underwent a resonant enhancement in CdIn₂S₄ and four infrared active but Raman forbidden F_1u modes appeared in the CdIn₂S₄ and ZnIn₂S₄ Raman spectra: TO modes at 226 (221) cm^-1 and 309 (312) cm^-1, and LO modes at 274 (272) cm^-1 and 340 (342) cm^-1.