A novel self-assembling nanosheet has the potential to significantly quicken the creation of sustainable and useful nanomaterials for a variety of applications, including energy storage, electronics, health, and safety.
Transmission electron microscope (TEM) images of the new 2D nanosheet as a barrier coating that self-assembles on a variety of substrates, including a Teflon beaker and membrane, polyester film, thick and thin silicon films, and glass. The TEM experiments were conducted at UC Berkeley’s Electron Microscope Laboratory. Image Credit: Emma Vargo et al./Berkeley Lab. Images courtesy of Nature
The novel self-assembling nanosheet, created by a team at Lawrence Berkeley National Laboratory (Berkeley Lab), has the potential to significantly extend the shelf life of consumer products. Additionally, the new material’s recyclable nature could make it possible to implement a sustainable manufacturing strategy that prevents electronics and single-use packaging from ending up in landfills.
The group is the first to effectively create a barrier material with several uses and outstanding efficiency using self-assembling nanosheets. Nature published a report on the breakthrough on November 8th, 2023.
Our work overcomes a longstanding hurdle in nanoscience—scaling up nanomaterial synthesis into useful materials for manufacturing and commercial applications. It is really exciting because this has been decades in the making.
Ting Xu, Study Lead and Faculty Senior Scientist, Materials Sciences Division, Lawrence Berkeley National Laboratory
Using nanoscience to produce functional materials is a problem since the nanomaterial must come together in large enough parts to be useful. Furthermore, while growing nanomaterials into a product by stacking nanosheets is one of the easiest methods, working with pre-existing nanosheets or nanoplatelets would inevitably result in “stacking defects,” or spaces between the nanosheets.
If you visualize building a 3D structure from thin, flat tiles, you will have layers up the height of the structure, but you’ll also have gaps throughout each layer wherever two tiles meet. It is tempting to reduce the number of gaps by making the tiles bigger, but they become harder to work with.
Emma Vargo, Study First Author and Postdoctoral Scholar, Lawrence Berkeley National Laboratory
By eschewing the serial stacked sheet technique completely, the novel nanosheet material solves the stacking defect problem. Rather, the group combined alternating layers of the constituent elements suspended in a solvent with mixtures of compounds known to self-assemble into small particles.
The researchers used complicated blends of small molecules, block copolymer-based supramolecules, and nanoparticles—all of which are commercially available—to build the system.
Experiments at the Spallation Neutron Source at Oak Ridge National Laboratory aided the researchers in understanding the early, coarse stages of the blends’ self-assembly. As the solvent evaporates, the small particles consolidate and spontaneously organize, forming coarsely templating layers before solidifying into thick nanosheets.
Instead of being piled one by one in a serial process, the ordered layers form concurrently. The small pieces only need to move a short distance to get organized and close gaps, avoiding the issues associated with moving larger “tiles” and the unavoidable gaps between them.
Combining nanocomposite blends with multiple “building blocks” of different sizes and chemistries, such as complex polymers and nanoparticles, would not only cope with impurities but also unlock a system’s entropy, or the inherent disorder in mixtures of materials that Xu’s group used to distribute the material’s building blocks. This knowledge came from a previous study led by Xu.
This earlier work is expanded upon in this new study. The researchers anticipated two perfect characteristics of the complicated mix utilized in this study: Apart from possessing a high entropy to facilitate the self-assembly of hundreds of nanosheets produced concurrently, they anticipated that the novel nanosheet structure would be little impacted by varying surface chemistries.
They reasoned that this would enable the same mixture to create a barrier of protection over a range of surfaces, such as polyester masks or the glass screen of electronic devices.
Ease of Self-Assembly and High Performance
The researchers collaborated with some of the top research centers in the country to assess the material’s effectiveness as a barrier coating in a variety of applications.
The researchers measured the mobilities of each component and the way it travels to form a functioning material by mapping out how each component joins together during tests at the Advanced Photon Source at Argonne National Laboratory.
By applying a diluted solution of polymers, organic small molecules, and nanoparticles to a variety of substrates, including a Teflon beaker and membrane, polyester film, thick and thin silicon films, glass, and even a prototype microelectronic device, and then regulating the rate of film formation, the researchers created barrier coatings based on these quantitative studies.
At Berkeley Lab’s Molecular Foundry, transmission electron microscopy experiments reveal that by the time the solvent evaporated, over 200 stacked nanosheets had self-assembled into a highly organized layered structure with a very low defect density on the substrates.
Additionally, each nanosheet was made by the researchers to be 100 nanometers thick with a few holes and gaps. According to Vargo, this makes the material especially effective in blocking the passage of electrons, water vapor, and volatile organic molecules.
The material has a lot of potential as a dielectric, an insulating “electron barrier” material frequently employed in capacitors for energy storage and computer applications, according to additional tests conducted at the Molecular Foundry.
Xu and colleagues, working with researchers in Berkeley Lab’s Energy Technologies Area, showed that the material is extremely effective at filtering out volatile organic compounds that can lower indoor air quality when it is applied to porous Teflon membranes, a material commonly used to make protective face masks.
Additionally, the material can be dissolved and recast to create a new barrier coating, as demonstrated by the researchers in a final experiment conducted at the Xu lab.
After proving that a single nanomaterial can be used to create a diverse functional material for a range of industrial applications, the researchers now want to improve the material’s recyclability and add color tunability (it is now available in blue).
The other authors of the study are Hugo Destaillats, Ivan Kuzmenko, Jan Ilavsky, Wei-Ren Chen, William Heller, Robert O. Ritchie, Yi Liu, Le Ma, He Li, Qingteng Zhang, Junpyo Kwon, Katherine M. Evans, Xiaochen Tang, Victoria L. Tovmasyan, Jasmine Jan, and Ana C. Arias.
The Laboratory Directed Research and Development (LDRD) program at Berkeley Lab and the DOE’s Office of Science provided funding for the study. The National Science Foundation, the Defense Threat Reduction Agency, and the Department of Defense contributed additional funds.
Journal Reference:
Vargo, E., et al. (2023) Functional composites by programming entropy-driven nanosheet growth. Nature. doi:10.1038/s41586-023-06660-x