Nanomaterials for clean drinking water

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New materials can be so small as to be almost invisible to the naked eye. Like the ultrathin membranes that the physicist Armin Gölzhäuser (only in German) is manufacturing and researching together with his work group at Bielefeld University in the northwest of Germany. They comprise just a single layer of carbon molecules.

Filters for fresh air and clean water

This two-dimensional carbon structure creates such fine pores that the membrane is able to filter out even the tiniest particles – individual molecules, to be precise. This is why Gölzhäuser is looking among other things at air and water filters as possible future applications. The membrane could for example separate carbon dioxide out of vehicle emissions, filter toxic pharmaceutical residues from drinking water or remove salt from seawater to make it drinkable.

Armin Gölzhäuser has been working on developing these membranes for decades. When manufacturing them in the lab, the researchers dip the surface of a thin gold sheet into a liquid containing organic molecules. A deposit then forms in a thin layer on the surface. It is not until they are subjected to electron radiation, which triggers a chemical reaction, that the molecules bond in the desired manner. The wafer-thin layer is then carefully removed from the carrier material – this is the most complicated part of the manufacturing process.

Tailor-made membranes

The Bielefeld-based physicist has meanwhile optimised the process to the point where different organic molecules can be used as the source materials, not just one particular type. This allows the properties of the membrane and its permeability for specific molecules to be controlled. The goal is to create membranes that are tailor-made for all kinds of different purposes.

"There are very many applications for such membranes today", says Gölzhäuser. "Yet there is limited understanding of what exactly happens when a molecule encounters a membrane. Does it touch the membrane? Does it get reflected?" Despite the many unanswered questions, the professor of physical chemistry is optimistic: "Membranes are already being used to clean freshwater and desalinate seawater – but the amount of energy this requires is enormous. We need more efficient membranes. Our nano membranes are not yet ready to remedy the situation, but in a few years we will be able to make a valuable contribution."

Nanoscience at Bielefeld University

Bielefeld University is home not only to Gölzhäuser’s team of experimental physicists but also to the Bielefeld Institute for Nanoscience (BINAS). Physicists there work together with scientists from the fields of biology, chemistry, nanoscience and biophysics.

www.physik.uni-bielefeld.de > Institute for Nanoscience (only in German)