Nanostructure Patterns with Exceptional Properties
Nanoscience can arrange minute molecular entities into nanoscale patterns thanks to self-organisation. A team of scientists at the Technical University of Munich has supplied a simple rod-shaped building block with hydroxamic acid at both ends. The resulting complex molecular networks show exceptional material properties.
Our genetic information is stored in two DNA strands which come together through a self-organisation process to form the well-known spiral staircase double helix structure. Hydrogen bonds help to stabilise both strands. Inspired by natural "zips", researchers of different disciplines and nationalities at the Technical University of Munich (TUM) are looking for new compounds to construct functional nanostructures and to push the boundaries of artificial structures.
In their research, published in the "Angewandte Chemie" journal, the scientists focused on a new building block for two-dimensional architectures: a chemical group named hydroxamic acid. Employees at the Chair of Proteomics and Bioanalytics in Freising supplied a rod-shaped molecule with a hydroxamic acid group at both ends. This was used to create molecular nanostructures on atomically smooth silver and gold surfaces at the Chair of Surface and Interface Physics in Garching.
A nanoporous network
A combination of microscopy, spectroscopy and density function theory investigations showed that the molecular building block changes its shape slightly in the environment of the supporting surface and its neighbouring molecules. This leads to an unusual variety of supramolecular surface structures formed from two to six molecules which are held together by intermolecular interactions. Only a handful of these motifs are organised into 2-D crystals. Among them, an unparalleled network emerged whose patterns resemble sliced lemons, snowflakes or rosettes. It features three different pores. The smallest would be able to hold an individual, small gas molecule such as carbon monoxide, while the largest has room for a small protein like insulin.
"In this regard, it is a milestone in the tessellations achieved by molecular nanostructures and the number of different pores expressed in crystalline 2-D networks," said Anthoula Papageorgiou, last author of the publication. "It thus offers unique opportunities in bottom-up nano-templating, which we will explore further."