The Cornell-led project created synthetic nanoclusters that mimic this hierarchical self-assembly from nanometers to centimeters, reaching seven orders of magnitude. The resulting synthetic thin films have the potential to serve as model systems for exploring biomimetic hierarchical systems and future advanced features.
Nature can be disgusting in a vacuum, but she definitely loves structure. Complex, self-organized clusters can be found throughout the natural world, from double-stranded DNA molecules to photonic crystals that make butterfly wings colorful and iridescent.
The document “Multiscale Hierarchical Structures from Nanocluster Mesophase” (nanoclusters that mimic this hierarchical self-assembly) was published on April 14 in Nature Materials.
Previously, the biggest obstacle in producing this type of synthetic nanomaterial was the lack of nanoscale building blocks with the necessary versatility to interact with scales of different lengths, allowing them to organize them into complex structures, as seen in biomolecules.
This team, led by co-authors Richard Robinson, a professor of materials science and engineering at the College of Engineering, and Tobias Hanrath, a professor at the Smith School of Chemical and Biomolecular Engineering, turned to cadmium sulfide, test, and the real material. for nanoparticle research.
Unlike previous attempts to synthesize a compound, the group has developed a high concentration version of the synthesis with less solvent. The process created “clusters of magical size” of 57 atoms, about 1.5 nanometers long. Each of these nanoparticles has a shell of ligands – special binding molecules – that can interact with each other in such a way that they form fibers several microns long and hundreds of nanometers long. According to Robinson, fibers are “rarely decorated with perfect distance in these magical big clumps, like on a highway.”
“When you look at the front of the fiber, below the center, it’s radially organized and also hexagonally structured,” he said. “And because these structural fibers have attractive references, they seem to assemble in a high order when dried under the right conditions.”
It is noteworthy that by carefully checking the evaporation geometry, the fibers in larger cables are wound hundreds of microns in length and the cables are then tied and tuned into very well-fitting strips. , which eventually led to the creation of a thin film on centimeter scales.
“Most of the time, you can’t synthesize anything with a seven-order-sized hierarchical nanometer organization. I think it’s really the special sauce,” Robinson said. “The meetings imitate many interesting natural products – natural mineralization, natural photonics – things that happen in nature that we in the laboratory cannot successfully reproduce.”
A mixture of organic and inorganic interactions gives magical large clusters the ability to produce films with perfect periodic patterns. The fact that a thin film can cover the entire spectrum of the rainbow, as scientists show, testifies to its flawless structure.
“It’s probably people haven’t seen it yet, because most syntheses are done in low concentrations, so you have a lot of solvents. “They don’t have the same ligand-ligand interactions,” he said. We changed that. We move the scale by clicking on the decimal place and perform this solvent-free synthesis.
One of the most interesting aspects of nanomaterial film is that it exhibits chiral optical properties – asymmetric absorption of polarized light – which are likely to occur at the nanoparticle level, and this property is extended to a macroscopic scale. . Thin films also share some strange similarities with liquid crystals.
To better understand the nature of the organization itself, Robinson and Hanrath consulted with a group of collaborators.
Lena Kourkoutis, associate professor of applied and engineering physics, performed electron microscopy, which allowed the team to see where the nanoparticles were sitting in the fibers. Julia Dshemuchadse, an assistant professor of materials science and engineering, theorized the rules governing fiber assembly and strength. Researchers at the University of Toronto and the Rochester Institute of Technology evaluated the interactions between the electrical dipoles that orient the clusters and developed a theoretical model that shows why the evaporation method and the nanocluster form a completely periodic film.
The discovery of unique multilevel structures opens up new avenues for the development of technologies that take advantage of their evolving chiropractic properties.
“The unique interactions between light and material of these chiropractic metamaterials can be used for a variety of potential applications, from sensing, catalysis, and circularly polarized light detectors to other perspectives in spintronics, quantum computing, and holography,” said Hanrath.
