Janus‐Partikel

Anisotropic particles are a materials class, which allows to induce multifunctional properties in a particular solid. This approach presents the possibility that different functions are packed in one particle, for example different surface polarities or optical and magnetic properties. The extraordinary structure of this particle consisting of two different compartments is expressed by the name Janus‐Particles. The chemical challenge is the synthetic approach to such particle structures. The reaction rooms on the length scale of the particle have to be differentiated in such a way that an anisotropy of growth and functionalization processes is generated. In this regard reactions at interphases play a major role. Meanwhile many different Janus‐material combinations are established and the first systems are transferred to technological processes.     

Analyse sehr kleiner Partikel mit der Mikrosonde

Zusammenfassung Sehr kleine Festkörperpartikel werden in einer Mikroschmelze aus Lithiumtetraborat unter Zugabe eines inneren Standards gelöst und mit der Mikrosonde quantitativ analysiert. Die Bestimmung der Menge an innerem Standard erfolgt durch mikroskopisches Ausmessen von Kriställchen des kubischen Systems.

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Analysis of very small particles by means of the microprobe

Summary Very small particles of solid substances are determined by the microprobe in melts of Li₂B₄O₇ using micro crucibles with addition of inner standards. The determination of the amount of inner standard is performed microscopically by measuring the size of small crystals of the cubic system.

Die Mittel zur Beschaffung der Mikrosonde wurden dankenswerterweise vom Bundesministerium für Wissenschaftliche Forschung zur Verfügung gestellt. Wir danken weiterhin der Fa. W. C. Heraeus, Hanau, für die Anfertigung der Mikrotiegel und der Hoechst AG (Herrn Dr. Kehler) für die Aufnahmen mit dem Rasterelektronenmikroskop.     

General Synthesis of Multishell Mixed‐Metal Oxyphosphide Particles with Enhanced Electrocatalytic Activity in the Oxygen Evolution Reaction

We report a general approach for the synthesis of multishell mixed‐metal oxyphosphide particles. Seven‐layer Mn‐Co oxide particles were first prepared by thermal treatment of Mn‐Co coordination polymer precursors. Afterwards, these multishell Mn‐Co oxide particles were further transformed into multishell Mn‐Co oxyphosphide particles through a phosphidation reaction. This approach is very versatile and can be applied to synthesize other multishell mixed‐metal oxyphosphide particles with different compositions. By applying a constant electrochemical potential, these multishell Mn‐Co oxyphosphide particles can be activated to produce Mn‐Co oxide/hydroxide species in their nanoshells and then show greatly enhanced electrocatalytic activity in the oxygen evolution reaction (OER).     

Shape-Shifting Patchy Particles

A facile method to synthesize shape-shifting patchy particles on the colloidal scale is described. The design is based on the solvent-induced shifting of the patch shape between concave and convex features. The initial concave patchy particles were synthesized in a water suspension by a swelling-induced buckling process. Upon exposure to different solvents, the patches were tuned reversibly to be either concave or convex. These particles can be assembled into chained, branched, zigzag, and cyclic colloidal superstructures in a highly site-specific manner by surface–liquid capillary bridging. The biphasic nature of the particles also enables site-selective surface functionalization.