Multistep self-assembly opens the door to new reconfigurable materials

The synthetic materials to be joined unite when tiny uniform blocks interact and form a structure. However, nature makes it possible to assemble materials such as proteins of variable size and shape, which makes it possible to create complex architectures capable of managing several tasks.

Engineers at the University of Illinois have taken a closer look at how non-uniform synthetic particles are assembling and have been surprised to find that this occurs in several phases, thus opening the door new reconfigurable materials for technologies such as solar cells and catalysis.

The results are reported in the newspaper Nature Communications.

"A traditional self-assembly can be considered a grocery store piling apples for a presentation in the product section," said Qian Chen, professor of materials science and engineering and senior author of the new study. "They would need to work with apples of similar size and shape – or particles in the case of self-assembly – to make the structure solid."

In the new study, Chen's group observed the behavior of microscopic silver plates of varying sizes and thicknesses in liquids. The particles used in self-assembled materials being so small, they behave like atoms and molecules, allowing researchers to use the classical theories of chemistry and physics to understand their behavior, indicated Researchers.

Ununiform particles repel and attract according to the laws of nature in ordinary deionized water. However, when researchers add salt to the water, the change in electrostatic forces triggers a multi-step assembly process. The team discovered that nonuniform particles began to assemble to form stacked silver plate columns and then assemble into increasingly complex and orderly hexagonal networks. .

"We can actually witness the assembly of particles in this hierarchy with the help of an optical microscope," said Binbin Luo, a graduate student in materials science and engineering and co-author of l & # 39; study. "Thus, we can track the particle movements one by one and study the dynamics of the assembly in real time."

"The results of this study could help develop reconfigurable self-assembly materials," said Ahyoung Kim, a graduate student in materials science and engineering and co-author of the study. "These materials can change from one type of solid crystal to another with different properties for a variety of applications."

"Another benefit of this discovery is that it can be generalized to other types of systems," Chen said. "If you have another type of nanoparticle, be it magnetic or semiconductor, this hierarchical assembly principle always applies, allowing you to create even more types of reconfigurable materials."