2021-10-27

Scientists have discovered the mechanism of controllable growth of tetrahedral nanoparticles

By yqqlm yqqlm

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2246011afee3ee6 - Scientists have discovered the mechanism of controllable growth of tetrahedral nanoparticles

Jones、 A new study by the main author and postdoctoral researcher sun Muhua and graduate students Cheng Zhihua and Chen Weiyin shows how the symmetry destruction in the process of particle growth can reliably form pyramid shaped tetrahedral nanocrystals. In symmetry breaking, small fluctuations in a developing system determine the fate of the system. In this example, it is suitable for crystal growth starting from nanoscale seeds with symmetrical atomic lattices

Rice University researchers showed how the force of balancing thermodynamics and kinetic energy in the crystallization process can be used to tilt the growth of particles in an ideal direction. Their discovery also opens a way for using asymmetric nanoparticles as building blocks of unique metamaterials

the research published in ACS Nano, the Journal of the American Chemical Society, comes from the work supported by Jones’s Packard scholarship, which helps him study liquid cell transmission electron microscopy (TEM)

the technology developed by Jones and his laboratory allows researchers to observe the formation of single metal nanoparticles in liquid through a window sufficient for electrons to pass through. In general, transmission electron microscopy works in high vacuum and simply evaporates the exposed liquid

researchers point out that tetrahedral nanoparticles are often found as by-products of other processes, but manufacturing them purposefully in the laboratory has proved to be a challenge

Jones said: “if a particle is a single crystal, it usually inherits the symmetry of the lattice. The crystal is often highly symmetrical, such as cube or diamond, dodecahedron or octahedron. However, some people see these strange outliers, which mysteriously have lower symmetry than the parent lattice.”

this new study is the first from Jones laboratory to show how liquid cell technology works well. While they were observing, the ability to flow the liquid containing ligands and precursors through the cells enabled them to redefine the symmetry of the final nanoparticle product

the key seems to be the growth rate and conditions. Under these conditions, gold atoms tend to attach themselves at the tips and edges of particles rather than on thermodynamically favorable surfaces

Jones said, “now we can screen out a series of conditions. We can see a spectrum. One end is kinetic energy growth, and the other end is in equilibrium. Kinetic energy growth is fast, and protrusions grow very fast, which is not well controlled. In equilibrium, growth is slow, and the system does what it wants to do, that is, maintain symmetry.”

“But liquid cell TEM allows us to change a variable in flight and see the behavior in the middle. We can see this strange symmetry destruction and a well-defined tetrahedral particle. So we conclude that this must be the balance between equilibrium and kinetic factors.”

Jones said to understand this basic equilibrium “It should be extended to other conditions.” he said that this discovery also established liquid cell TEM as a valuable tool for observing and analyzing dynamic chemical processes, and it is possible to eliminate a large number of experiments and errors in the synthesis of particles required for biomedicine, catalysis or nanophotonics.

he said: “Nothing is more important than being able to observe the whole thing. That’s what this technology does. You’re not emitting photons at something, and then you have to do a lot of analysis to explain the results. You just watch the process. Seeing is believing.”