Sichuan girl Li Yuanwei has been in love with polymers for nine years. After the college entrance examination, she was admitted to the school of Polymer Science and Engineering, Sichuan University, and the school's polymer discipline has always been well-known, and she also published a polymer paper when she was a bachelor's degree.
Figure | Li Yuanwei (Source: Li Yuanwei)
Later, she found that many well-known professors in the fields of polymers and nanomaterials were at , and there was also International Institute of Nanotechnology founded by Professor Chad Mirkin.
Professor Milkin is an academician of the Seventh Academy and has served as a science and technology consultant to former US President Obama . Li Yuanwei is currently studying for a doctorate in Professor Milkin's research group. She said: "I plan to do post-blog first, and consider returning to China to find a faculty position after the post-blog is over."
Recently, Li Yuanwei's latest paper was published on Nature. In the field of colloids, she and her team reported negative refractive index crystals for the first time, providing new ideas for the preparation of invisible garment and high-performance optics.
"also takes an important step towards the preparation of porous supercrystals that can arbitrarily adjust the size, appearance, and connection between holes. At the same time, the design method we proposed paves the way for the reverse design of open channel superlattice ." She said.
At the same time, This progress in nanomaterial synthesis and structural regulation is of some transformation. On the one hand, the open channel supercrystal is a negative refractive index metamaterial . Currently, no natural material has this property.
The negative refractive index material of photonic crystal structure has exciting broad application prospects, including ultralens, supermicroscopy, electromagnetic invisibility, information storage, mobile communication, etc. . This new type of negative refractive index metamaterial makes invisible and high-performance optical devices more "close" to reality, so it can help realize the invisible cloak earlier.
On the other hand, the supercrystals of the open channel can be used to adsorb some large-sized functional materials that were previously unable to be adsorbed, such as quantum dot , proteins and viruses. This is equivalent to providing a preparation method for new composite structures. At the same time, these structures will also have a wide impact on the fields of catalysis, optics, electronics, and biology. The review experts of
paper pointed out that for the first time, the team pioneered the preparation of porous materials by edge bonding of hollow nanoparticle , enriching the design space of colloidal crystals. Moreover, the proposed construction method is universal. The porous structure prepared by has unprecedented controllability and diversity , filling the pore size gap of existing porous materials in the range of 10-1000nm.
At the same time, these porous superlattices themselves also have strong negative refractive index, setting a precedent for negative refractive index in the field of colloidal crystals, perfecting the full spectrum from unusual ultra-high positive refractive index to negative refractive index, and promoting the development of optical products.
(Source: Nature)
A new self-assembly mode is launched
Overall, This result not only solves the core problems in the field: how to prepare porous materials with adjustable pore topology and 10-1000nm pore size; it also proposes a new programmable self-assembly mode and a new design rule based on this mode.
As a highly ordered material with extraordinary characteristics, porous crystals mainly have high surface area and low density, so they can be used to physically absorb object substances of specific sizes, shapes and chemical functions, and have a series of physical and chemical effects with them.
porous colloidal materials based on colloid self-assembled and are an especially interesting class of porous crystals. They can provide an reflective crystal for use in optics, energy storage, biological reactions, etc.
Before this, people generally made this type of structure through template technology. However, the limitation of this strategy is that using face-centered cubic crystals self-assembled with spherical particles as templates will greatly limit the pore topology and pore volume distribution.
is used to realize the method of reticular chemical synthesis based on metal ions and bridged ligands, although significant progress has been made in the preparation of porous materials with pore sizes less than 10nm. However, how to prepare supercrystals with customized pore topology and pore sizes between 10-1000nm remains a major challenge in the field.
In this paper, Li Yuanwei and others used a programmable ligand such as DNA (deoxyribonucleic acid), to assemble hollow three-dimensional metal nanoparticles into open channel superlattice.
They found that there is an interaction of DNA junctions between the edges of the hollow nanoparticles and will lead to the formation of an ordered superlattice.
Previously, face-to-face connection was generally used to control the assembly of solid nanoparticles. This edge and edge assembly mode is a brand new self-assembly mode.
More importantly, The team also used two new design rules to describe this edge bonding construction strategy, and used the above design rules to synthesize 12 open channel superlattices. , which cannot be achieved by traditional assembly methods.
At the same time, the crystal symmetry, pore geometry and topological structure of these structures can be adjusted arbitrarily by processing the shape and DNA design of hollow nanoparticles.
It can be said that these new crystal structure and universal assembly methods have brought new opportunities in the field: that is, the outstanding optical characteristics of open channel metal superlattices such as make it an attractive new optical metamaterial.
Recently, the relevant paper was published on Nature[1] under the title "Open-channel metal particle superlattices". Li Yuanwei is the first author and Academician Chad Mirkin serves as the corresponding author.
Figure | Related papers (Source: Nature)
One of the reviewers pointed out that the research team described a new type of self-assembly phenomenon of hollow nanoparticles. The edges of these hollow polyhedrons are connected to each other. Therefore, even non-space filled polyhedrons can be assembled into porous non-close-packaged crystals.
And the self-assembly and nanocages can better control the crystal structure and pore topological structure than most methods of preparing porous materials before.
(Source: Nature)
Fill in the pore size gap of existing porous materials in the range of 10-1000nm
Li Yuanwei said that as of now, the methods of preparing porous crystals can be roughly divided into two types: 3D printing and chemical synthesis.
On the one hand, 3D printing can prepare some complex porous materials. However, due to the limitation of printing accuracy , the pore size of D printing material is usually greater than one micron.
On the other hand, when molecular chemistry is used to prepare porous materials such as metal organic frames, zeolite , covalent organic frames, the pore size is generally less than 10nm.
Therefore, she has always hoped to propose a universal method for the preparation of porous materials with pore sizes of 10-1000nm.
In this scale, colloidal nanoparticles have a high degree of adjustability. Therefore, introducing the concept of porous into colloidal crystals is expected to solve this problem.
However, the self-assembly of colloidal nanoparticles always tend to form dense and non-porous structures. Therefore, how to create or retain the open hole structure in the colloidal superlattice has become a problem that needs to be overcome.
Based on this idea, Li Yuanwei proposed to use hollow nanoparticles to assemble into a porous structure. In order to make the idea come true, she needs to answer three questions:
How to prepare hollow construction units? How to assemble this new type of hollow structure and how to understand this new assembly mode? What are the interesting performance and potential of these new porous structures?
. Li Yuanwei previously published a paper on Science Advanceds , which has helped solve the above problems. That paper introduces the selective growth of nanoparticles and has been patented.
It can be said that when preparing hollow and uniform nanostructured units, the Science Advanceds paper laid a solid foundation for this project. Because the selective growth of nanoparticles on specific sides or surfaces is a key step in the preparation of hollow nanoparticles.
is different from the assembly of traditional solid nanoparticles. The hollow nanoframe has only sides but no faces. This type of new type of hollow particles, through the connection between edges, the assembled supercrystal is beyond expectations, which means that a new self-assembly model is officially launched.
Using this edge-to-edge bonding pattern, coupled with an in-depth understanding of geometry, Li Yuanwei and her team summarized two new design rules to synthesize a series of new open channel supercrystals.
In order to test performance and application value, they studied the possibility of these three-dimensional structures in chemical adsorption and optical (negative refractive index), and also studied the optical application of two-dimensional crystal films, and verified the possibility of a single-layer plasma nanoframe as a large-area, broadband metasurface absorber [3].
(Source: Nature)
At the same time, Li Yuanwei also admitted that although this study showed 12 porous supercrystals, this is just the beginning. Next, she will carry out structural designs with a wider coverage.
In order to enable these materials to generate application value as soon as possible, she will also strive to overcome the following challenges: First, make large-area open-channel superlattice films of any shape; Second, use a new nanoframework composed of low-optical loss materials as the construction unit, thereby increasing the signal transmission of open-channel superlattice, thereby improving the performance of devices based on them.
Reference:
.Li, Yuanwei, et al. Open-channel metal particle superlattices. Nature 611, 695–701 (2022). https://doi.org/10.1038/s41586-022-05291-y
.Li, Yuanwei, et al. Corner-, edge-, and facet-controlled growth of nanocrystals. Science Advanceds 7, eabf1410 (2021). https://www.science.org/doi/10.1126/sciadv.abf1410
.Li, Yuanwei, et al. Monolayer Plasmonic Nanoframes as Large‐Area, Broadband Metasurface Absorbers. Small 18, 2201171 (2022). https://onlinelibrary.wiley.com/doi/full/10.1002/smll.202201171
