The Nano-Blizzard: How the 'snowflake effect' is solving nanotech’s synthesis problem
- Mateo Cardinal
- 6 minutes ago
- 3 min read
Whether they’re tickling your nose, hugging your eyelashes or melting on your tongue, few winter wonders are as fascinating as snowflakes.
The freezing-cold crystals are known for their one-of-a-kind appearances, which can be attributed to the multiple scientific processes that converge during their growth. Water molecules solidify and stick together in the glacial air. As they collect, they craft complex hexagonal formations often too small for the naked eye. No two snowflakes are ever quite the same because rapidly changing temperatures and humidities influence every tiny branch.
However, when it comes to microcrystals generated by complex forces, snowflakes are just the tip of the iceberg.
In a new study from NAU’s Department of Applied Physics and Materials Science, a group of researchers discovered that similar things happened to their fabricated gold, copper and iron nanocrystals. When the metal particles clumped together during a lightning-fast chemical reaction, they formed pentagonal constructs that strongly resemble natural snowflakes, a phenomenon that holds incredible implications for the future of nanotechnology.
Joelin A. Agyei-Mensah, an applied physics doctoral student and the paper’s first author, spearheaded the two-year study as part of her graduate research within the materials science program. The paper’s authors also include applied physics doctoral student Philip Asare, Center for Materials Interfaces in Research and Applications (¡MIRA!) research scientist J. Jesús Velázquez Salazar and Regents’ Professor Miguel José Yacamán.
The team’s paper was published as the cover story for Small, a nanoscience and nanotechnology journal, in November.
“For the first time, we demonstrate that the emergence phenomenon seen in snowflakes plays a key role in nanotechnology,” José Yacamán said. “By introducing the physics of complex systems, we can help individuals understand and control nanomaterial synthesis and advance the field toward broader applications.”
In the not-so-small world of modern nanotechnology, one of the greatest challenges industry scientists face is reliably controlling how nanomaterials are formed. Nanoparticle growth relies on a whirlwind of thermodynamic and kinetic factors, coalescing into processes almost impossible to predict or reproduce.
Researchers often try to subvert this issue by accumulating materials slowly and at high temperatures. These tactics are less than ideal for nanoparticles, though, and can lead to the small specks merging into unwanted shapes.
Agyei-Mensah and her co-authors used a new nanoparticle synthesis method in this study, one conversely characterized by extremely fast reactions.
They heated a small silicon chip to 280 degrees Celsius, or more than 500 degrees Fahrenheit, before placing their metal salts and adding chemical agents designed to encourage growth. In fewer than 10 seconds, the metal salts formed crystals between 1 nanometer and several micrometers long. The rapid reaction allowed scientists to observe all stages of nanoparticle growth in the blink of an eye and record their results.
In the end, the team produced a collection of wholly unique multimetallic structures. Smaller crystals exhibited simple shapes consistent with previous studies, but larger particles were more complex and displayed pentagonal symmetry, concave surfaces and hollow insides. Overall shapes recurred, but each particle had a different metal composition.
What exactly was to blame for these pseudo-icy oddities? José Yacamán said it is the scientific concept of emergence.
The term describes instances where complicated systems possess properties that their individual pieces do not. Unique behaviors only emerge when parts unite to form an unforeseeable whole. This theory can be used to understand occurrences across vastly different fields, including biology, physics, chemistry and even poetry.
“An important example of emergence is human reproduction,” José Yacamán said. “When the embryo starts to grow, many chemical reactions and physical phenomena are present during the self-assembly, and the result is diversity. No two humans are the same, just like snowflakes, because the self-assembly can follow different paths.”
The authors argue that both their metal crystals and snowflakes are governed by the same emergence dynamics. Nanoparticles cluster together, or aggregate, to form larger superstructures. As a result, each of these metallic marvels is entirely distinct, just like their North Pole neighbors.
Proving this fact opens the door to myriad uses of multimetallic nanoparticle synthesis. Understanding emergence could help scientists have better control over the nanomaterials they fabricate, curing a fieldwide ailment and supporting unprecedented scientific breakthroughs.
“Most natural phenomena are complex and can become chaotic, such as the weather or the stock market, in which long-term predictions are very difficult,” José Yacamán said. “Nevertheless, complex systems result in a state which is not necessarily chaotic. Our possibility of prediction is very limited, but we can get an approximate idea of the outcome.”
Reference De Nive Quinquangula: Pentagonal Snowflake Metal Nanocrystals as an Example of Emergence Phenomenon in Nanotechnology Complex Systems
This article relates to:
Joelin A. Agyei-Mensah, Philip Asare, J. Jesús Velázquez Salazar, Steven C. Hayden, Miguel José Yacamán
