Recyclable nanosheets as high-performance barrier material

New self-assembling and recyclable nanosheets for electronics, energy storage, and health and safety applications have been developed by researchers led by Lawrence Berkeley National Laboratory. The 2D nanosheets could significantly improve the shelf life of consumer products, as well as reducing the amount of single-use packaging and electronics being thrown away.

As reported in Nature [Vargo et al. Nature (2023) DOI: 10.1038/s41586-023-06660-x], this is the first time that a multipurpose, high-performance barrier material from self-assembling nanosheets has been successfully developed. It is hoped the nanosheets could significantly increase the rate of development of functional and sustainable nanomaterials. To develop such materials the various pieces need to combine for the nanomaterial to grow big enough for use.

Although stacking nanosheets into a product is straightforward, gaps between the nanosheets cannot be avoided. However, this nanosheet material circumvents the problem of stacking defects by missing the serial stacked sheet approach by combining blends of materials that can self-assemble into small particles with alternating layers of the component materials, suspended in a solvent.

The complex blend needed two ideal properties, that in addition to having high entropy to drive the self-assembly of a stack of nanosheets formed simultaneously, the system would be minimally affected by different surface chemistries. This means the same blend can form a protective barrier on many surfaces, including the glass screen of electronic devices.

The performance of the material as a barrier coating was tested by mapping out how each component comes together. Barrier coatings were then made by applying a dilute solution of polymers, organic small molecules, and nanoparticles to a range of substrates, with the rate of film formation being controlled.

When the solvent evaporates, the small particles coalesce and spontaneously organize coarsely templating layers, before solidifying into dense nanosheets. As the small pieces are only required to move short distances to get organized and close gaps, the problems of moving larger tiles and the inevitable gaps between them is avoided.

As principal investigator and study leader Ting Xu told Materials Today, “Self-assembly prizes precision and naturally connects precision with clean systems. Yet, real material synthesis and applications aren’t. I believe our study shows […] there are room for both if we are willing to think outside of the box.”

Although the research remains at an early stage, and the blends have significantly enhanced miscibility that needs to be investigated at the molecular level, which is a challenge because of the size differences involved. The team also want to improve the material’s recyclability and add color tunability.

“Self-assembly prizes precision and naturally connects precision with clean systems. Yet, real material synthesis and applications aren’t. I believe our study shows […] there are room for both if we are willing to think outside of the box.”Ting Xu