Markus Boese

Europium-Directed Self-Assembly of a Luminescent Supramolecular Gel from a Tripodal Terpyridine-Based Ligand†

Eu(III), the last piece in the puzzle: Europium-induced self-assembly of ligands having a C(3)-symmetrical benzene-1,3,5-tricarboxamide core results in the formation of luminescent gels. Supramolecular polymers are formed through hydrogen bonding between the ligands. The polymers are then brought together into the gel assembly through the coordination of terpyridine ends by Eu(III) ions (blue dashed arrow: distance between two ligands in the strand direction).

Chemical Nano-Gardens: Growth of Salt Nanowires from Supramolecular Self-Assembly Gels

In this article, we examine the phenomenon of single-crystal halide salt wire growth at the surface of porous materials. We report the use of a single-step casting technique with a supramolecular self-assembly gel matrix that upon drying leads to the growth of single-crystal halide (e.g., NaCl, KCl, and KI) nanowires with diameters ~130-200 nm. We demonstrate their formation using electron microscopy and electron-dispersive X-ray spectroscopy, showing that the supramolecular gel stabilizes the growth of these wires by facilitating a diffusion-driven base growth mechanism. Critically, we show that standard non-supramolecular gels are unable to facilitate nanowire growth. We further show that these nanowires can be grown by seeding, forming nanocrystal gardens. This study helps understand the possible prefunctionalization of membranes to stimulate ion-specific filters or salt efflorescence suppressors, while also providing a novel route to nanomaterial growth.

Nitrogen assisted etching of graphene layers in a scanning electron microscope

We describe the controlled patterning of nanopores in graphene layers by using the low-energy (<10 keV) focused electron beam in a scanning electron microscope. Regular nanometer-sized holes can be fabricated with the presence of nitrogen gas. The effect of the gas pressure, beam current, and energy on the etching process are investigated. Transmission electron microscopy, coupled with plasmon energy loss imaging, reveals the microstructure modification of the etched graphene. A nitrogen-ion assisted etching mechanism is proposed for the controlled patterning.

Porous TiO2 with a controllable bimodal pore size distribution from natural ilmenite

Ilmenite (FeTiO3) is an inexpensive abundant natural mineral and it would be a perfect precursor for the production of porous TiO2 if a suitable synthesis method was developed. A new method combining a series of processing steps of ball milling, high-temperature annealing, selective chemical leaching and final calcining in air is proposed in this paper. The resulting TiO2 is a porous material with a bimodal pore structure. The pore size distribution has two clear maxima corresponding to small mesopores (2–30 nm) and large meso- and macropores (centered at around 50–80 nm). It was found that the duration of the annealing step could alter the contribution of each type of pores. A short annealing time (0.5 h) lead to the preferential formation of pores within 2–30 nm while pores centered at 50–80 nm dominated the pore size distribution after a relatively long annealing (1.5 h). The obtained porous rutile TiO2 shows a better photocatalytic activity than that of a commercial rutile TiO2 powder.

Surface Energy Driven Agglomeration and Growth of Single Crystal Metal Wires

We introduce a novel wire growth technique that involves simply heating a multilayer film specifically designed to take advantage of the different surface energies of the substrate and film components. In all cases the high surface energy component is extruded as a single crystal nanowire. Moreover we demonstrate that patterning the bilayer film generates localized surface agglomeration waves during the anneal that can be exploited to position the grown wires. Examples of Au and Cu nanowire growth are presented, and the generalization of this method to other systems is discussed.

A facile “bottom-up” approach to prepare free-standing nano-films based on manganese coordination clusters

We present herein a novel method to prepare free-standing Dried Foam Films (DFFs) whereby individual polynuclear manganese complexes cover quantitatively the holes of micro-grids; the fabricated, homogeneous films have a cross-sectional thickness of only ca. 5 nm and are characterised by high mechanical stability.

Synthesis and self-assembly of ultrathin β-nickel hydroxide nanodisks via a wet-chemistry method

Self-assembled ultrathin β-nickel hydroxide nanodisks have been synthesized by using a wet-chemistry method. The uniformity and the assembly of β-Ni(OH)2 nanostructures are sensitive to the iron ion concentration in the precursor. An optimum concentration of 10% results in the formation of uniform ultrathin β-Ni(OH)2 nanodiscs with a typical side length of 50 nm and a thickness of 8 nm. They are also self-assembled by connecting their (0001) facets and form a chain-like microstructure.