Determining the properties of mesoporous materials more precisely
A marriage between order and disorder.
Everyone should have had them in their hands at least once: Little bags with small balls, which are in the packaging of new shoes or electrical goods. The spheres are there to absorb moisture and thus protect the items from damage. "These materials can be compared to a sponge," explains physicist Prof. Dr. Rustem Valiullin of the University of Leipzig.
He and his research group have found a way to more precisely determine the properties of these materials because they can better account for the underlying disorder. Their findings were selected as an "ACS Editors' Choice" by the editors of the American Chemical Society journals because they recognize the "importance to the global scientific community" of the Leipzig researchers' article and see it as a breakthrough in accurately describing phase transition phenomena in disordered porous materials.
In mesoporous materials, the openings are incomparably smaller than in a normal sponge: their diameters range in the nanoscale from 2 to 50 nanometers and are imperceptible to the human eye. Nevertheless, their properties make them of interest, for example, for the separation of substances, which takes place, for example, as a function of the molecule and pore size.
Until now, it has only been possible to find out the desired properties of these materials approximately through experiments. "So it's more based on experience whether you can determine which of the structures can be used for which applications," the physicist said. That's because the problem is that these materials are mostly disordered, meaning that pores of different sizes in the material form a complex network structure.
The researchers at the University of Leipzig have developed a model that captures the features that can be observed in the complex pore networks. "We can statistically describe how the individual pores in these networks are coupled to each other," Prof. Valiullin said, outlining the approach. "We marry disorder with order." This makes it possible to capture the physical phenomena that need to be understood in gas-liquid and solid-liquid phase transitions, for example. And not just in theory: using special mesoporous model systems, it was possible to demonstrate with the aid of modern nuclear magnetic resonance methods that the theoretical results can also be directly translated into practice.
In the future, this should simplify the use of such materials, which, for example, help to release drugs into the human body over a defined, even longer period of time only when this is necessary and desired. Other fields of application for such materials include sensor technology and energy storage and conversion.
Scientific article: Langmuir: Enninful et al. (2021) - Impact of Geometrical Disorder on Phase Equilibria of Fluids and Solids Confined in Mesoporous Materials
Source: Chemie.de – Eigenschaften mesoporöser Materialien präziser bestimmen
Image source: Wikimedia Commons : Biofilter tech – Porous Ceramic