Revolutionizing Water Purification: The Breakthrough of Ion-Permeable Graphene Sensors

A multitude of scientists are diligently researching graphene. There is a significant rationale for this, as the unique properties of the substance suggest new uses, particularly in electronics or energy technology.

Rendering Graphene Permeable to Additional Molecules

It is particularly intriguing for researchers to manipulate the permeability of graphene for various substances: ‘So-called defects can be introduced in the carbon lattice of graphene. These can be envisioned as tiny holes that render the lattice permeable to gases,’ explains chemistry professor Frank Würthner from Julius-Maximilians-Universität (JMU) Würzburg in Bavaria, Germany.

Permeability to other substances, like ions such as fluoride, chloride or bromide, has yet to be documented. ‘Nonetheless, this would hold fundamental scientific significance for applications such as the desalination of water, as well as detection or purification of mixtures of substances,’ elucidates the Würzburg professor.

Defect Permits Ions to Pass: Publication in Nature

For the first time, a research team headed by Frank Würthner has succeeded in creating a model system with a defect that allows halides like fluoride, chloride and bromide to traverse, but not iodide. This was accomplished with a stable double layer comprised of two nanographenes that encloses a cavity. The infiltrated halide ions are retained within this cavity, enabling the measurement of the time required for entry. The findings have been released in the journal Nature.

Chloride, a part of common salt, is present in seawater and plays a crucial role in life processes across all organisms. ‘The demonstration of a high permeability for chloride via single-layer nanographene and a selective binding of halides in a double-layer nanographene brings several applications closer,’ states Dr. Kazutaka Shoyama, who conceived and managed the project alongside Frank Würthner. Potential applications include water filtration membranes, artificial receptors, and chloride channels.

Larger Collections of Nanographenes are the Upcoming Target

In the subsequent phase, the Würzburg chemists aim to construct larger assemblies of their nanographenes. Their goal is to explore the movement of ions — thus investigating a process that occurs in a similar fashion within biological ion channels.

This investigation was conducted at the Institute of Organic Chemistry and the Center for Nanosystems Chemistry at JMU. The research received funding from the German Research Foundation (DFG) as part of two grants aimed at developing nanographenes modified with imide groups.