Supracrystals are highly symmetrical ordered superstructures built up from nanoparticles (NPs) via self-assembly. While the NP assembly has been intensively investigated, the formation mechanism is still not understood. To shed some light onto the formation mechanism, one of the most common supracrystal morphologies, the trigonal structures, as a model system is being used to investigate the formation process in solution. To explain the formation of the trigonal structures and determining the size of the supracrystal seeds formed in solution, the concept of substrate-affected growth is introduced. Furthermore, the influence of the NP concentration on the seed size is shown and our investigations from Ag toward Au are extended.

Many different aerogel materials are known to be accessible via the controlled destabilization of the respective nanoparticle suspensions. Especially for applications in heterogeneous catalysis such materials with high specific surface areas are highly desirable. Here, a facile method to obtain a mixed ZnPd/ZnO aerogel via a reductive treatment of a preformed Pd/ZnO aerogel is presented. Different morphologies of the Pd/ZnO aerogels could be achieved by controlling the destabilization of the ZnO sol. All aerogels show a high CO₂ selectivity of up to 96% and a very good activity in methanol steam reforming that delivers hydrogen, which is one of the most important fuels for future energy concepts. The method presented is promising for different transition metal/metal oxide systems and hence opens a path to a huge variety of materials.

Eine gezielte Verbesserung der Baueinheiten ist eine naheliegende Herangehensweise, um Aerogele mit herausragenden Eigenschaften zu versehen und gleichzeitig ihre Vorzüge zu erhalten. Bestimmte Eigenschaften, wie die Optimierung der Morphologie für katalytische Anwendungen oder die Übergangsmetalldotierung in metallischen Aerogelen, sind jedoch nach wie vor schwer zu realisieren. In diesem Zusammenhang präsentieren wir hier erstmalig elektrokatalytisch aktive Aerogele, welche sich vollständig aus legierten PdNi-Hohlnanosphären (HNS) aufbauen und deren chemische Zusammensetzung und Schalendicke gezielt eingestellt werden kann. Die Kombination von Übergangsmetalldotierung mit hohlen Baueinheiten in einem dreidimensionalen Netzwerk machen PdNi-HNS-Aerogele zu vielversprechenden Elektrokatalysatoren für die Ethanoloxidation. Gegenüber dem kommerziellen Pd/C-Katalysator zeigt das Pd₈₃Ni₁₇-HNS-Aerogel eine 5.6-fach höhere Massenaktivität. Durch diese Arbeit wird die Nutzbarkeit von metallischen Aerogelen in der Elektrokatalyse erweitert, indem die Morphologie und Zusammensetzung der Baueinheiten gezielt kontrolliert werden.

One plausible approach to endow aerogels with specific properties while preserving their other attributes is to fine-tune the building blocks. However, the preparation of metallic aerogels with designated properties, for example catalytically beneficial morphologies and transition-metal doping, still remains a challenge. Here, we report on the first aerogel electrocatalyst composed entirely of alloyed PdNi hollow nanospheres (HNSs) with controllable chemical composition and shell thickness. The combination of transition-metal doping, hollow building blocks, and the three-dimensional network structure make the PdNi HNS aerogels promising electrocatalysts for ethanol oxidation. The mass activity of the Pd₈₃Ni₁₇ HNS aerogel is 5.6-fold higher than that of the commercial Pd/C catalyst. This work expands the exploitation of the electrocatalysis properties of aerogels through the morphology and composition control of its building blocks.

In this study, we introduce the first membraneless glucose/O₂ biofuel cell using Pd-based aerogels as electrode materials. The bioanode was fabricated with a coimmobilized mediator and glucose oxidase for the oxidation of glucose, in which ferrocenecarboxylic acid was integrated into a three-dimensional porous beta-cyclodextrin-modified Pd aerogel to mediate the bioelectrocatalytic reaction. Bilirubin oxidase and Pd–Pt alloy aerogel were confined to an electrode surface, which realized the direct bioelectrocatalytic function for the reduction of O₂ to H₂O with a synergetic effect at the biocathode. By employing these two bioelectrodes, the assembled glucose/O₂ biofuel cell showed a maximum power output of 20 μW cm⁻² at 0.25 V.

Mixed metal–semiconductor nanocrystal aerogels are fabricated, which are light-emitting and highly porous macroscopic monoliths. Thiol-stabilized CdTe and Au nanoparticles from aqueous synthesis act as building blocks for the hybrid material. The Au colloids undergo a surface-modification to enhance the particle stability and achieve thiol functionalities. A photochemical treatment is applied for the gelation process which is found to be reversible by subsequent addition of thiol molecules. Via supercritical drying aerogels are formed. The variation of the initial CdTe to Au nanoparticle ratio permits a facile tuning of the content and the properties of the resulting aerogels. The obtained structures were characterized by means of optical spectroscopy, electron microscopy, elemental analysis, and nitrogen physisorption.

Kolloidale Halbleiternanopartikel sind vielversprechende Luminophore für die Entwicklung einer neuen Generation von Elektrolumineszenzeinheiten. Bei Halbleiternanokristall-LEDs wurden im Laufe eines Jahrzehnts enorme Fortschritte erzielt: So ließ sich die externe Quantenausbeute um mehr als zwei Größenordnungen verbessern, und Funktionseinheiten mit hoch gesättigten Farbemissionen sind heute Standard. Wenngleich die Geräteeffizienz immer noch eine Größenordnung kleiner ist als bei rein organischen LEDs, haben die Nanokristall-LEDs eine ganze Reihe potenzieller Vorteile, z. B. spektralreine Emissionsfarben, was ein lohnender Forschungszweig für künftige Entwicklungen scheint. Weitere technische Verbesserungen von Nanokristall-LEDs zielen auf höhere Materialstabilitäten, eine gezielte Steuerung chemischer und physikalischer Vorgänge an den Grenzflächen und die Optimierung der Ladungsinjektion und des Ladungstransports ab.

Colloidal semiconductor nanocrystals are promising luminophores for creating a new generation of electroluminescence devices. Research on semiconductor nanocrystal based light-emitting diodes (LEDs) has made remarkable advances in just one decade: the external quantum efficiency has improved by over two orders of magnitude and highly saturated color emission is now the norm. Although the device efficiencies are still more than an order of magnitude lower than those of the purely organic LEDs there are potential advantages associated with nanocrystal-based devices, such as a spectrally pure emission color, which will certainly merit future research. Further developments of nanocrystal-based LEDs will be improving material stability, understanding and controlling chemical and physical phenomena at the interfaces, and optimizing charge injection and charge transport.