A sieve for molecules

Date:
March 7, 2022
Source:
Ruhr-University Bochum
Summary:
Scientists have long tried to use graphene, which is composed of
carbon, as a kind of sieve. But this material doesn't have any
pores. Now, a team has found an alternative material which comes
with pores from the outset.



FULL STORY ========================================================================== Scientists have long tried to use graphene, which is composed of carbon,
as a kind of sieve. But this material doesn't have any pores. Now, a team
has found an alternative material which comes with pores from the outset.


========================================================================== Researchers from Bielefeld, Bochum and Yale have succeeded in producing
a layer of two-dimensional (2D) silicon dioxide. This material contains
natural pores and can therefore be used like a sieve for molecules and
ions. Scientists have been looking for such materials for a long time
because they could for example help desalinate seawater and be used in
new types of fuel cells. The team outlines the fabrication process of
bilayer silicates in the journal Nano Letters, published online on 19
January 2022. The study was jointly conducted by the teams headed by
Dr. Petr Dementyev from Bielefeld University, Professor Anjana Devi from Ruhr-Universita"t Bochum and Professor Eric Altman from Yale University.

Naturally occurring pores in the crystal lattice When two-dimensional
materials are pierced with high precision, they can be used to filter
out certain ions and molecules. Researchers have time and again tried
to perforate the material graphene for this purpose, which consists
of carbon atoms. Since it has no natural pores, they must be inserted artificially. But it is difficult to create holes of a defined size in
graphene without permanently damaging the material. This is because
it loses mechanical stability due to the perforation. Consequently,
an alternative had to be found.

In the current study, the research team took advantage of the fact that
the crystal lattice of two-dimensional silicon dioxide contains pores
by nature.

They showed that these pores can be used to separate certain gases from
each other.

"This is very exciting because 2D silicon dioxide has a very high
density of tiny pores by nature that is simply not possible to be
created in artificial membranes," says Petr Dementyev from the Physics of Supramolecular Systems and Surfaces research group in Bielefeld. "Unlike
in perforated graphene, the pores are all almost the same size. And
there's such an incredible number of them that the material behaves like
a fine-mesh sieve for molecules." Problematic to manufacture 2D silica
has been known since 2010. However, it was very expensive to manufacture,
which could only be done on a small scale. Pooling together expertise
from materials chemistry, chemical engineering and chemical physics, the researchers from Bochum, Bielefeld and Yale came up with a new material fabrication process. They used so-called atomic layer deposition to
deposit a single layer of silicon dioxide on a gold surface. Using a high-pressure process, the researchers transferred the layer into its two-dimensional form and then characterised it in detail by means of spectroscopy and microscopy.

They then examined the gas flow through the 2D membrane in a vacuum
chamber.

While vaporous water and alcohol penetrated the silica layer, the gases nitrogen and oxygen couldn't pass through. "Materials like this with
selective permeability are in high demand in industry," says Anjana
Devi. However, before the 2D silica can be used in practice, it is
important to evaluate exactly how many different molecules can attach
to the surface of the material or how they can penetrate it.

"We expect our results to be of high relevance to the materials
science community worldwide," concludes Anjana Devi from the
Inorganic Materials Chemistry research group. Such 2D membranes
could be at the forefront of aiding sustainable development,
for example in the field of energy conversion or storage." ========================================================================== Story Source: Materials provided by Ruhr-University_Bochum. Original
written by Julia Weiler.

Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. Daniil Naberezhnyi, Lukas Mai, Nassar Doudin, Inga Ennen, Andreas
Hu"tten, Eric I. Altman, Anjana Devi, Petr Dementyev. Molecular
Permeation in Freestanding Bilayer Silica. Nano Letters, 2022; 22
(3): 1287 DOI: 10.1021/acs.nanolett.1c04535 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2022/03/220307091727.htm

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