A new study from Northwestern University and the University of Michigan has recently revealed how, for the first time, low-symmetry colloidal crystals can be produced, which includes a single phase for which there is the unknown natural correspondent.
According to a Phys.org report, "nature keeps a few secrets." Whereas many structures that have low symmetry are present in nature, researchers have been restricted to high-symmetry designs when colloidal crystals are being synthesized.
Essentially, colloidal crystals are a valuable nanomaterial type used for optoelectronic devices, as well as biological sensing.
According to Chad Mirkin of Northwestern University, they have discovered something essential about the system for developing new materials. He added, such a strategy for breaking symmetry modifies the rules for both material design and synthesis.
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In a study, metal nanoparticles with surfaces covered with designer DNA were used to make the crystals.
Colloidal Crystals
The research, published in the Nature Materials journal, was directed by Mirkin and Sharon Glotzer, the Anthony C. Lembke Department of Chair of Chemical Engineering at the University of Michigan.
In their study, the authors specified that nanoparticles can be programmed and pulled together into ordered arrays called colloidal crystals, which can be engineered for use from light sensors and lasers, to computing and communications.
Describing their report, Glotzer explained, using large and tiny nanoparticles, where the tinier ones "move around like electrons in a crystal of metal atoms," is an entirely new method to constructing complex structures of crystals.
Essentially, in this study, metal nanoparticles with surfaces covered with designer DNA were used to make the crystals.
'Programmable Atom Equivalents'
The researchers also showed that the DNA functioned as an "encodable bonding material" that turns them into the so-called PAEs or programmable atom equivalents.
This method provides exceptional control over the crystal lattices' shape and parameters, as the nanoparticles can be engineered to arrange themselves in detailed ways after a set of rules had been previously developed by Mirkin and his team.
Nevertheless, to this point, researchers have not had a way to organize lattices, with some crystal symmetries. Since a lot of PAEs is isotropic, which means, their constructions are uniform in all directions, they are inclined to arrange into highly symmetric constructions, and it is quite hard to develop low-symmetry lattices.
Valency
Such a breakthrough arose through a new method to regulating valency, which in Chemistry, is associated with the electrons' arrangement around an atom.
Valency determines the number of bonds that can be formed by the atom, as well as the geometry it assumes. Building on a recent find that the tiny PAEs can behave as electron correspondents, roaming through, and evening out lattices for more massive PAEs, the Michigan and Northwestern researchers improved their electron equivalents' valency by regulating the DNA strands' density grafted into their surface.
Then, they used advanced electron microscopy to watch closely how changing the electron equivalents' valency impacts their spatial distribution among the PAEs and thus, and consequently, the resulting lattices.
As specified in the similar Nano Magazine report, the impacts of changing temperatures and improving the PAEs' ratio to electrons are were also examined.
According to Glotzer, they explored more complex structures where regulation over the number of neighbors surrounding each particle generated further symmetry gracing.
She added, their computer simulations helped to understand the complicated patterns and show the mechanisms that allowed the nanoparticles to develop them.
Related information about colloidal crystals is shown on Sacanna Lab's YouTube video below:
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