Tag Archives: self-assembly

Inspired by Picasso (or Schumpeter, Shiva, and others?), Université de Montréal researchers employ creative destruction to create new nanomachines

I associate the idea of ‘creative destruction’ with economics and Joseph Schumpeter but it is more widespread and has a much longer history (see more at the end of this posting).

Here we have Université de Montréal researchers being inspired by the idea from (what was to me) an unexpected source, from a February 9, 2023 news item on Nanowerk,

“Every act of creation,” Picasso famously noted, “is first an act of destruction.”

Taking this concept literally, researchers in Canada have now discovered that “breaking” molecular nanomachines basic to life can create new ones that work even better.

I love this image. Bravo!

Researchers Dominic Lauzon and Alexis Vallée-Bélisle Credit: Amélie Philibert & Benoit Gougeon | Université de Montréal

A February 9, 2023 Université de Montréal news release, which originated the news item, delves further into this act of creative destruction,

Evolved over millions of years

Life on Earth is made possible by tens of thousands of nanomachines that have evolved over millions of years. Often made of proteins or nucleic acids, they typically contain thousands of atoms and are less than 10,000 times the size of a human hair.

“These nanomachines control all molecular activities in our body, and problems with their regulation or structure are at the origin of most human diseases,” said the new study’s principal investigator Alexis Vallée-Bélisle, a chemistry professor at Université de Montréal.

Studying the way these nanomachines are built, Vallée-Bélisle, holder of the Canada Research Chair in Bioengineering and Bio-Nanotechnology, noticed that while some are made using a single component or part (often long biopolymers), others use several components that spontaneously assemble.

“Since most of my students spend their lives creating nanomachines, we started to wonder if it is more beneficial to create them using one or more self-assembling molecular components,” said Vallée-Bélisle.

A ‘destructive’ idea

To explore this question, his doctoral student Dominic Lauzon, had the “destructive” idea of breaking up some nanomachines to see if they could be reassembled. To do so, he made artificial DNA-based nanomachines that could be “destroyed” by breaking them up.

“DNA is a remarkable molecule that offers simple, programmable and easy-to-use chemistry,” said Lauzon, the study’s first author. “We believed that DNA-based nanomachines could help answer fundamental questions about the creation and evolution of natural and human-made nanomachines.”

Lauzon and Vallée-Bélisle spent years performing the experimental validations. They were able to demonstrate that nanomachines could easily withstand fragmentation, but more importantly, that such a destructive event allowed for the creation of various novel functionalities, including different sensitivity levels towards variation in component concentration, temperature and mutations.

What the researchers found is that these functionalities could arise simply by controlling the concentration of each individual component. For example, when cutting a nanomachine in three components, nanomachines were found to activate more sensitively at high concentration of components. In contrast, at low concentration of components, nanomachines could be programmed to activate or deactivate at specific moment in time or to simply inhibit their function.

“Overall, these novel functionalities were created  by simply cutting up, or destroying, the structure of an existing nanomachine,” said Lauzon. “These functionalities could drastically improve human-based nanotechnologies such as sensors, drug carriers and even molecular computers”.

Evolving new functionalities

Just as Picasso typically destroyed dozens of unfinished works to create his famous artworks, and just like muscles need to break down to get stronger, and innovative new companies are born by eliminating older competitors from the market, nanoscale machines can evolve new functionalities by being taken apart.

Unlike common machines like cell phones, televisions and cars, which are made by combining components using screws and bolts, glue, solder or electronics, “nanomachines rely on thousands of weak dynamic intermolecular forces that can spontaneously reform, enabling broken nanomachines to re-assemble,” said Vallée-Bélisle.

In addition to providing nanotechnology researchers with a simple design strategy to create the next generation of nanomachines, the UdeM team’s findings also shed light on how natural molecular nanomachines may have evolved.

“Biologists have recently discovered that about 20 per cent of biological nanomachines may have evolved through the fragmentation of their genes,” said Vallée-Bélisle. “With our results, biologists now have a rational basis for understanding how the fragmentation of these ancestral proteins could have created new molecular functionalities for life on Earth.”

Here’s a link to and a citation for the paper,

Functional advantages of building nanosystems using multiple molecular components by D. Lauzon & A. Vallée-Bélisle. Nature Chemistry volume 15, pages 458–467 (2023) DOI: https://doi.org/10.1038/s41557-022-01127-4 Published online: 09 February 2023 Issue Date: April 2023

This paper is behind a paywall.

Creative destruction

The Wikipedia entry for ‘Creative destruction’ is primarily on economic theory and various philosophies with no mention of Picasso. However, there is a fascinating segue into Eastern mysticism,

Other early usage

Hugo Reinert has argued that Sombart’s formulation of the concept was influenced by Eastern mysticism, specifically the image of the Hindu god Shiva, who is presented in the paradoxical aspect of simultaneous destroyer and creator.

On that note, have a lovely weekend.

Self-assembled molecular nanofibers that are stronger than steel

A January 26, 2021 news item on Nanowerk announces a promising discovery in ‘self-assembly research’ (Note: A link has been removed,

Self-assembly is ubiquitous in the natural world, serving as a route to form organized structures in every living organism. This phenomenon can be seen, for instance, when two strands of DNA — without any external prodding or guidance — join to form a double helix, or when large numbers of molecules combine to create membranes or other vital cellular structures. Everything goes to its rightful place without an unseen builder having to put all the pieces together, one at a time.

For the past couple of decades, scientists and engineers have been following nature’s lead, designing molecules that assemble themselves in water, with the goal of making nanostructures, primarily for biomedical applications such as drug delivery or tissue engineering.

“These small-molecule-based materials tend to degrade rather quickly,” explains Julia Ortony, assistant professor in [Massachusetts Institute of Technology] MIT’s Department of Materials Science and Engineering (DMSE), “and they’re chemically unstable, too. The whole structure falls apart when you remove the water, particularly when any kind of external force is applied.”

She and her team, however, have designed a new class of small molecules that spontaneously assemble into nanoribbons with unprecedented strength, retaining their structure outside of water. The results of this multi-year effort, which could inspire a broad range of applications, were described in Nature Nanotechnology (“Self-assembly of aramid amphiphiles into ultra-stable nanoribbons and aligned nanoribbon threads”) by Ortony and coauthors.

“This seminal work — which yielded anomalous mechanical properties through highly controlled self-assembly — should have a big impact on the field,” asserts Professor Tazuko Aida, deputy director for the RIKEN Center for Emergent Matter Science and professor of chemistry and biotechnology at the University of Tokyo, who was not involved in the research.

A January 26, 2021 MIT news release, which originated the news item, describe the work in more detail,

The material the MIT group constructed — or rather, allowed to construct itself — is modeled after a cell membrane. Its outer part is “hydrophilic,” which means it likes to be in water, whereas its inner part is “hydrophobic,” meaning it tries to avoid water. This configuration, Ortony comments, “provides a driving force for self-assembly,” as the molecules orient themselves to minimize interactions between the hydrophobic regions and water, consequently taking on a nanoscale shape.

The shape, in this case, is conferred by water, and ordinarily the whole structure would collapse when dried. But Ortony and her colleagues came up with a plan to keep that from happening. When molecules are loosely bound together, they move around quickly, analogous to a fluid; as the strength of intermolecular forces increases, motion slows and molecules assume a solid-like state. The idea, Ortony explains, “is to slow molecular motion through small modifications to the individual molecules, which can lead to a collective, and hopefully dramatic, change in the nanostructure’s properties.”

One way of slowing down molecules, notes Ty Christoff-Tempesta, a PhD student and first author of the paper, “is to have them cling to each other more strongly than in biological systems.” That can be accomplished when a dense network of strong hydrogen bonds join the molecules together. “That’s what gives a material like Kevlar — constructed of so-called ‘aramids’ — its chemical stability and strength,” states Christoff-Tempesta.

Ortony’s team incorporated that capability into their design of a molecule that has three main components: an outer portion that likes to interact with water, aramids in the middle for binding, and an inner part that has a strong aversion to water. The researchers tested dozens of molecules meeting these criteria before finding the design that led to long ribbons with nanometer-scale thickness. The authors then measured the nanoribbons’ strength and stiffness to understand the impact of including Kevlar-like interactions between molecules. They discovered that the nanoribbons were unexpectedly sturdy — stronger than steel, in fact. 

This finding led the authors to wonder if the nanoribbons could be bundled to produce stable macroscopic materials. Ortony’s group devised a strategy whereby aligned nanoribbons were pulled into long threads that could be dried and handled. Notably, Ortony’s team showed that the threads could hold 200 times their own weight and have extraordinarily high surface areas — 200 square meters per gram of material. “This high surface-to-mass ratio offers promise for miniaturizing technologies by performing more chemistry with less material,” explains Christoff-Tempesta. To this end, they have already developed nanoribbons whose surfaces are coated with molecules that can pull heavy metals, like lead or arsenic, out of contaminated water. Other efforts in the research group are aimed at using bundled nanoribbons in electronic devices and batteries.

Ortony, for her part, is still amazed that they’ve been able to achieve their original research goal of “tuning the internal state of matter to create exceptionally strong molecular nanostructures.” Things could easily have gone the other way; these materials might have proved to be disorganized, or their structures fragile, like their predecessors, only holding up in water. But, she says, “we were excited to see that our modifications to the molecular structure were indeed amplified by the collective behavior of molecules, creating nanostructures with extremely robust mechanical properties. The next step, figuring out the most important applications, will be exciting.”

Here’s a link to and a citation for the paper,

Self-assembly of aramid amphiphiles into ultra-stable nanoribbons and aligned nanoribbon threads by Ty Christoff-Tempesta, Yukio Cho, Dae-Yoon Kim, Michela Geri, Guillaume Lamour, Andrew J. Lew, Xiaobing Zuo, William R. Lindemann & Julia H. Ortony. Nature Nanotechnology (2021) DOI: https://doi.org/10.1038/s41565-020-00840-w Published: 18 January 2021

This paper is behind a paywall.

Periodic table of nanomaterials

This charming illustration is the only pictorial representation i’ve seen for Kyoto University’s (Japan) proposed periodic table of nanomaterials, (By the way, 2019 is UNESCO’s [United Nations Educational, Scientific and Cultural Organization] International Year of the Periodic Table of Elements, an event recognizing the table’s 150th anniversary. See my January 8, 2019 posting for information about more events.)

Caption: Molecules interact and align with each other as they self-assemble. This new simulation enables to find what molecules best interact with each other to build nanomaterials, such as materials that work as a nano electrical wire.
Credit Illustration by Izumi Mindy Takamiya

A July 23, 2018 news item on Nanowerk announces the new periodic table (Note: A link has been removed),

The approach was developed by Daniel Packwood of Kyoto University’s Institute for Integrated Cell-Material Sciences (iCeMS) and Taro Hitosugi of the Tokyo Institute of Technology (Nature Communications, “Materials informatics for self-assembly of functionalized organic precursors on metal surfaces”). It involves connecting the chemical properties of molecules with the nanostructures that form as a result of their interaction. A machine learning technique generates data that is then used to develop a diagram that categorizes different molecules according to the nano-sized shapes they form.

This approach could help materials scientists identify the appropriate molecules to use in order to synthesize target nanomaterials.

A July 23, 2018 Kyoto University press release on EurekAlert, which originated the news item, explains further about the computer simulations run by the scientists in pursuit of their specialized periodic table,

Fabricating nanomaterials using a bottom-up approach requires finding ‘precursor molecules’ that interact and align correctly with each other as they self-assemble. But it’s been a major challenge knowing how precursor molecules will interact and what shapes they will form.

Bottom-up fabrication of graphene nanoribbons is receiving much attention due to their potential use in electronics, tissue engineering, construction, and bio-imaging. One way to synthesise them is by using bianthracene precursor molecules that have bromine ‘functional’ groups attached to them. The bromine groups interact with a copper substrate to form nano-sized chains. When these chains are heated, they turn into graphene nanoribbons.

Packwood and Hitosugi tested their simulator using this method for building graphene nanoribbons.

Data was input into the model about the chemical properties of a variety of molecules that can be attached to bianthracene to ‘functionalize’ it and facilitate its interaction with copper. The data went through a series of processes that ultimately led to the formation of a ‘dendrogram’.

This showed that attaching hydrogen molecules to bianthracene led to the development of strong one-dimensional nano-chains. Fluorine, bromine, chlorine, amidogen, and vinyl functional groups led to the formation of moderately strong nano-chains. Trifluoromethyl and methyl functional groups led to the formation of weak one-dimensional islands of molecules, and hydroxide and aldehyde groups led to the formation of strong two-dimensional tile-shaped islands.

The information produced in the dendogram changed based on the temperature data provided. The above categories apply when the interactions are conducted at -73°C. The results changed with warmer temperatures. The researchers recommend applying the data at low temperatures where the effect of the functional groups’ chemical properties on nano-shapes are most clear.

The technique can be applied to other substrates and precursor molecules. The researchers describe their method as analogous to the periodic table of chemical elements, which groups atoms based on how they bond to each other. “However, in order to truly prove that the dendrograms or other informatics-based approaches can be as valuable to materials science as the periodic table, we must incorporate them in a real bottom-up nanomaterial fabrication experiment,” the researchers conclude in their study published in the journal xxx. “We are currently pursuing this direction in our laboratories.”

Here’s a link to and a citation for the paper,

Materials informatics for self-assembly of functionalized organic precursors on metal surfaces by Daniel M. Packwood & Taro Hitosugi. Nature Communicationsvolume 9, Article number: 2469 (2018)DOI: https://doi.org/10.1038/s41467-018-04940-z Published 25 June 2018

This paper is open access.

Mussels to muscles for biocompatible fibres

Mussels and barnacles in the intertidal near Newquay, Cornwall, England.
Wilson44691 at English Wikipedia – Photograph taken by Mark A. Wilson (Department of Geology, The College of Wooster

I love puns and word play so I was happy to see this in a June 9, 2017 news item on ScienceDaily,

Rice University chemists can thank the mussel for putting the muscle into their new macroscale scaffold fibers.

A June 9, 2017 Rice University news release (also on EurekAlert), which originated the news item, provides more details about the research,

The Rice lab of chemist Jeffrey Hartgerink had already figured out how to make biocompatible nanofibers out of synthetic peptides. In new work, the lab is using an amino acid found in the sticky feet of mussels to make those fibers line up into strong hydrogel strings.

Hartgerink and Rice graduate student I-Che Li introduced their room-temperature method this month in an open-access paper in the Journal of the American Chemical Society.

The hydrogel strings can be picked up and moved with tweezers, and Li said he expects they will help labs gain better control over the growth of cell cultures.

“Usually when cells grow on a surface, they spread randomly,” he said. “There are a lot of biomaterials we want to grow in a specific direction. With the hydrogel scaffold aligned, we can expect cells to grow the way we want them to. One example would be neuron cells, which we want to grow head-to-tail to aid nerve regeneration.

“Basically, this could allow us to direct cell growth from here to there,” he said. “That’s why this material is so exciting.”

In previous research Hartgerink’s lab had developed synthetic hydrogels that could be injected into the body to serve as scaffolds for tissue growth. The hydrogels contained hydrophobic peptides that self-assembled into fibers about 6 nanometers wide and up to several microns long. However, because the fibers did not interact with one other, they generally appeared in microscope images as a tangled mass.

Experiments showed the fibers could be coaxed into alignment with the application of shear forces, in the same way that playing cards are aligned during shuffling by pushing on both the top and bottom of the deck.

Hartgerink and Li decided to try pushing the fibers through a needle to force them into alignment, a process that would be easier if the material was water soluble. So they added a chain of amino acids known as DOPA to the sides of the fibers to allow them to remain water-soluble in the syringe, Li said.

DOPA — short for 3,4-dihydroxyphenylalanine — is the compound that lets mussels stick to just about anything. Hartgerink and Li found that the combination of DOPA and shear stress from passing through the needle prompted the fibers to form visible, rope-like bundles.

They also found that DOPA promoted chemical cross-linking reactions that helped the bundles hold their shape. “DOPA is really sensitive to oxidizing agents,” Li said. “Even exposing DOPA to air oxidizes it, and that aids in cross-linking the fibers.”

As a bonus, the aligned fibers also proved to have a curious and useful optical property called “uniform birefringence,” or double-refraction. Li said this could allow researchers to use polarized light to see exactly where the aligned fibers are, even if they’re covered by cells.

“This will be an important technique for us to make sure of the long-range order of fiber alignment when we are testing directed cell growth,” he said.

The researchers expect the aligned fibers can be used for macroscale medical applications but with nanoscale control over the structures.

“Self-assembly is basically the ability of a molecule to make ordered structure from chaos, and what I-Che has done is push this organization to a new level with his aligned strings,” said Hartgerink, a professor of chemistry and of bioengineering. “With this material, we are excited to see if we can impose this organization onto the growth of cells that interact with it.”

Here’s a link to and a citation for the paper,

Covalent Capture of Aligned Self-Assembling Nanofibers by I-Che Li and Jeffrey D. Hartgerink. J. Am. Chem. Soc., Article ASAP DOI: 10.1021/jacs.7b04655 Publication Date (Web): June 5, 2017

Copyright © 2017 American Chemical Society

This paper is open access.

Carbon nanotubes self-assembling into transistors on a gold substrate

I’m not sure this work is ready for commercialization (I think not) but it’s certainly intriguing. From an April 5, 2017 news item on ScienceDaily,

Carbon nanotubes can be used to make very small electronic devices, but they are difficult to handle. University of Groningen scientists, together with colleagues from the University of Wuppertal and IBM Zurich, have developed a method to select semiconducting nanotubes from a solution and make them self-assemble on a circuit of gold electrodes. …

An April 5, 2017 University of Groningen (Netherlands) press release on EurekAlert, which originated the news item, explains the work in more detail,

The results look deceptively simple: a self-assembled transistor with nearly 100 percent purity and very high electron mobility. But it took ten years to get there. University of Groningen Professor of Photophysics and Optoelectronics Maria Antonietta Loi designed polymers which wrap themselves around specific carbon nanotubes in a solution of mixed tubes. Thiol side chains on the polymer bind the tubes to the gold electrodes, creating the resultant transistor.

Patent

‘In our previous work, we learned a lot about how polymers attach to specific carbon nanotubes’, Loi explains. These nanotubes can be depicted as a rolled sheet of graphene, the two-dimensional form of carbon. ‘Depending on the way the sheets are rolled up, they have properties ranging from semiconductor to semi-metallic to metallic.’ Only the semiconductor tubes can be used to fabricate transistors, but the production process always results in a mixture.

‘We had the idea of using polymers with thiol side chains some time ago’, says Loi. The idea was that as sulphur binds to metals, it will direct polymer-wrapped nanotubes towards gold electrodes. While Loi was working on the problem, IBM even patented the concept. ‘But there was a big problem in the IBM work: the polymers with thiols also attached to metallic nanotubes and included them in the transistors, which ruined them.’

Solution

Loi’s solution was to reduce the thiol content of the polymers, with the assistance of polymer chemists from the University of Wuppertal. ‘What we have now shown is that this concept of bottom-up assembly works: by using polymers with a low concentration of thiols, we can selectively bring semiconducting nanotubes from a solution onto a circuit.’ The sulphur-gold bond is strong, so the nanotubes are firmly fixed: enough even to stay there after sonication of the transistor in organic solvents.

The production process is simple: metallic patterns are deposited on a carrier , which is then dipped into a solution of carbon nanotubes. The electrodes are spaced to achieve proper alignment: ‘The tubes are some 500 nanometres long, and we placed the electrodes for the transistors at intervals of 300 nanometres. The next transistor is over 500 nanometres away.’ The spacing limits the density of the transistors, but Loi is confident that this could be increased with clever engineering.

‘Over the last years, we have created a library of polymers that select semiconducting nanotubes and developed a better understanding of how the structure and composition of the polymers influences which carbon nanotubes they select’, says Loi. The result is a cheap and scalable production method for nanotube electronics. So what is the future for this technology? Loi: ‘It is difficult to predict whether the industry will develop this idea, but we are working on improvements, and this will eventually bring the idea closer to the market.’

Here’s a link to and a citation for the paper,

On-Chip Chemical Self-Assembly of Semiconducting Single-Walled Carbon Nanotubes (SWNTs): Toward Robust and Scale Invariant SWNTs Transistors by Vladimir Derenskyi, Widianta Gomulya, Wytse Talsma, Jorge Mario Salazar-Rios, Martin Fritsch, Peter Nirmalraj, Heike Riel, Sybille Allard, Ullrich Scherf, and Maria A. Loi. Advanced Materials DOI: 10.1002/adma.201606757 Version of Record online: 5 APR 2017

© 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

This paper is behind a paywall.

Synthesized nanoparticles with the complexity of protein molecules

Caption: The structure of the largest gold nanoparticle to-date, Au246(SR)80, was resolved using x-ray crystallography. Credit: Carnegie Mellon University

Carnegie Mellon University (CMU) researchers synthesized a self-assembled nanoparticle of gold as they built on their 2015 work described in my April 14, 2015 posting (Nature’s patterns reflected in gold nanoparticles). Here’s the latest from the team in a Jan. 23, 2017 news item on phys.org,

Chemists at Carnegie Mellon University have demonstrated that synthetic nanoparticles can achieve the same level of structural complexity, hierarchy and accuracy as their natural counterparts – biomolecules. The study, published in Science, also reveals the atomic-level mechanisms behind nanoparticle self-assembly.

The findings from the lab of Chemistry Professor Rongchao Jin provide researchers with an important window into how nanoparticles form, and will help guide the construction of nanoparticles, including those that can be used in the fabrication of computer chips, creation of new materials, and development of new drugs and drug delivery devices.

Caption: By resolving the structure of Au246, Carnegie Mellon researchers were able to visualize its hierarchical assembly into artificial solid. Credit: Carnegie Mellon University

A Jan.  23, 2017 CMU news release on EurekAlert, which originated the news item, expands on the theme,

“Most people think that nanoparticles are simple things, because they are so small. But when we look at nanoparticles at the atomic level, we found that they are full of wonders,” said Jin.

Nanoparticles are typically between 1 and 100 nanometers in size. Particles on the larger end of the nanoscale are harder to create precisely. Jin has been at the forefront of creating precise gold nanoparticles for a decade, first establishing the structure of an ultra-small Au25 nanocluster and then working on larger and larger ones. In 2015, his lab used X-ray crystallography to establish the structure of an Au133 nanoparticle and found that it contained complex, self-organized patterns that mirrored patterns found in nature.

In the current study, they sought to find out the mechanisms that caused these patterns to form. The researchers, led by graduate student Chenjie Zeng, established the structure of Au246, one of the largest and most complex nanoparticles created by scientists to-date and the largest gold nanoparticle to have its structure determined by X-ray crystallography. Au246 turned out to be an ideal candidate for deciphering the complex rules of self- assembly because it contains an ideal number of atoms and surface ligands and is about the same size and weight as a protein molecule.

Analysis of Au246’s structure revealed that the particles had much more in common with biomolecules than size. They found that the ligands in the nanoparticles self-assembled into rotational and parallel patterns that are strikingly similar to the patterns found in proteins’ secondary structure. This could indicate that nanoparticles of this size could easily interact with biological systems, providing new avenues for drug discovery.

The researchers also found that Au246 particles form by following two rules. First, they maximize the interactions between atoms, a mechanism that had been theorized but not yet seen. Second the nanoparticles match symmetric surface patterns, a mechanism that had not been considered previously. The matching, which is similar to puzzle pieces coming together, shows that the components of the particle can recognize each other by their patterns and spontaneously assemble into the highly ordered structure of a nanoparticle.

“Self-assembly is an important way of construction in the nanoworld. Understanding the rules of self-assembly is critical to designing and building up complex nanoparticles with a wide-range of functionalities,” said Zeng, the study’s lead author.

In future studies, Jin hopes to push the crystallization limits of nanoparticles even farther to larger and larger particles. He also plans to explore the particles’ electronic and catalytic power.

Here’s a link to and a citation for the paper,

Emergence of hierarchical structural complexities in nanoparticles and their assembly by Chenjie Zeng, Yuxiang Chen, Kristin Kirschbaum, Kelly J. Lambright, Rongchao Jin. Science  23 Dec 2016: Vol. 354, Issue 6319, pp. 1580-1584 DOI: 10.1126/science.aak9750

This paper is behind a paywall.

New design strategy for synthesizing metal-organic frameworks (MOFs)

A Jan. 24, 2017 news item on Nanowerk announces new research from South Korea,

The accurate interpretation of particle sizes and shapes in nanoporus materials is essential to understanding and optimizing the performance of porous materials used in many important existing and potentially new applications. However, only a few experimental techniques have been developed for this purpose.

A team of researchers, led by Professor Wonyoung Choe of Natural Science and Professor Ja Hun Kwak of Energy and Chemical Engineering [ at Ulsan National Institute of Science and Technology {UNIST}] has recently developed a novel design strategy for synthesizing various forms of functional materials, especially for metal-organic materials (MOMs).

The research team expects that this synthetic approach might open up a new direction for the development of diverse forms in MOMs, with highly advanced areas such as sequential drug delivery/release and heterogeneous cascade catalysis targeted in the foreseeable future.

A Jan. 6, 2017 UNIST press release, which originated the news item, provides more detail,

In the last decades, much research has been developed to the synthesis and design of functional materials, but only a few of them could control the walls of the interior of the particles within the nanoporous materials.

In the study, Professor Choe and his team denomstrated sequential self-assembly strategy for synthesizing various forms of MOM crystals, including double-shell hollow MOMs, based on single-crystal to single-crystal transformation from MOP to MOF.

Schematic representation of various forms of micro-/nanostructures. From left are Solid, core-shell, hollow, matryoshka, yolk-shell and multi-shell hollow structures.

Porous materials are highly utilized as catalysts or gas capture materials because they supply abundant surface active sites for chemical reaction. Although materials, like Zeolites, which can be obtained from nature, have the ability to act as catalysts for chemical reactions, they suffer from the difficulty of controlling pore sizes and shapes.

As one solution, scientists have developed self-assembled porous materials using organic molecules and metals. Metal-Organic Frameworks (MOFs) and Metal-Organic Polyhedral (MOPs) are notable examples and they both have holes all over their surfaces. MOPs dissolve easily in chemical solvent, while MOFs are practically insoluble.

“MOFs take the form of three-dimensional (3D) structure, linking metals with organic molecules, while MOPs agglomerate together to form larger clusters,” says Jiyoung Lee, the first contributor of the study and a graduate student in the combined master-doctoral program from Chemistry department.

Schematic illustration of form evolution.

Schematic illustration of form evolution.

According to the research team, this synthetic strategy also yields other forms, such as solid, core-shell, double and triple matryoshka, and single-shell hollow MOMs, thereby exhibiting form evolution in MOMs.

“The best feature of this technique is that it allows two very different substances to coexist within a single crystal,” says Professor Choe. “This technique also permits greater control over size and shape of the pore, which can be then used to regulate the entrance and exit of molecules.”

This particular synthetic approach also has the potential to generate new type of porous materials containing micropores with diameters less than 2nm, macropores with diameters between 20 to 50nm, as well as pores of larger than 50 nm. Such hierarchical pore structure plays a critical role during catalysis, adsorption, and separation processes.

Here’s a link to and a citation for the paper,

Evolution of form in metal–organic frameworks by Jiyoung Lee, Ja Hun Kwak & Wonyoung Choe. Nature Communications 8, Article number: 14070 (2017) doi:10.1038/ncomms14070 Published online: 04 January 2017

This is an open access paper.

Novel self-assembly at 102 atoms

A Jan. 13, 2017 news item on ScienceDaily announces a discovery about self-assembly of 102-atom gold nanoclusters,

Self-assembly of matter is one of the fundamental principles of nature, directing the growth of larger ordered and functional systems from smaller building blocks. Self-assembly can be observed in all length scales from molecules to galaxies. Now, researchers at the Nanoscience Centre of the University of Jyväskylä and the HYBER Centre of Excellence of Aalto University in Finland report a novel discovery of self-assembling two- and three-dimensional materials that are formed by tiny gold nanoclusters of just a couple of nanometres in size, each having 102 gold atoms and a surface layer of 44 thiol molecules. The study, conducted with funding from the Academy of Finland and the European Research Council, has been published in Angewandte Chemie.

A Jan. 13, 2017 Academy of Finland press release, which originated the news item, provides more technical information about the work,

The atomic structure of the 102-atom gold nanocluster was first resolved by the group of Roger D Kornberg at Stanford University in 2007 (2). Since then, several further studies of its properties have been conducted in the Jyväskylä Nanoscience Centre, where it has also been used for electron microscopy imaging of virus structures (3). The thiol surface of the nanocluster has a large number of acidic groups that can form directed hydrogen bonds to neighbouring nanoclusters and initiate directed self-assembly.

The self-assembly of gold nanoclusters took place in a water-methanol mixture and produced two distinctly different superstructures that were imaged in a high-resolution electron microscope at Aalto University. In one of the structures, two-dimensional hexagonally ordered layers of gold nanoclusters were stacked together, each layer being just one nanocluster thick. Modifying the synthesis conditions, also three-dimensional spherical, hollow capsid structures were observed, where the thickness of the capsid wall corresponds again to just one nanocluster size (see figure).

While the details of the formation mechanisms of these superstructures warrant further systemic investigations, the initial observations open several new views into synthetically made self-assembling nanomaterials.

“Today, we know of several tens of different types of atomistically precise gold nanoclusters, and I believe they can exhibit a wide variety of self-assembling growth patterns that could produce a range of new meta-materials,” said Academy Professor Hannu Häkkinen, who coordinated the research at the Nanoscience Centre. “In biology, typical examples of self-assembling functional systems are viruses and vesicles. Biological self-assembled structures can also be de-assembled by gentle changes in the surrounding biochemical conditions. It’ll be of great interest to see whether these gold-based materials can be de-assembled and then re-assembled to different structures by changing something in the chemistry of the surrounding solvent.”

“The free-standing two-dimensional nanosheets will bring opportunities towards new-generation functional materials, and the hollow capsids will pave the way for highly lightweight colloidal framework materials,” Postdoctoral Researcher Nonappa (Aalto University) said.

Professor Olli Ikkala of Aalto University said: “In a broader framework, it has remained as a grand challenge to master the self-assemblies through all length scales to tune the functional properties of materials in a rational way. So far, it has been commonly considered sufficient to achieve sufficiently narrow size distributions of the constituent nanoscale structural units to achieve well-defined structures. The present findings suggest a paradigm change to pursue strictly defined nanoscale units for self-assemblies.”

References:

(1)    Nonappa, T. Lahtinen, J.S. Haataja, T.-R. Tero, H. Häkkinen and O. Ikkala, “Template-Free Supracolloidal Self-Assembly of Atomically Precise Gold Nanoclusters: From 2D Colloidal Crystals to Spherical Capsids”, Angewandte Chemie International Edition, published online 23 November 2016, DOI: 10.1002/anie.201609036

(2)    P. Jadzinsky et al., “Structure of a thiol-monolayer protected gold nanoparticle at 1.1Å resolution”, Science 318, 430 (2007)

(3)    V. Marjomäki et al., “Site-specific targeting of enterovirus capsid by functionalized monodispersed gold nanoclusters”, PNAS 111, 1277 (2014)

Here’s the figure mentioned in the news release,

Figure: 2D hexagonal sheet-like and 3D capsid structures based on atomically precise gold nanoclusters as guided by hydrogen bonding between the ligands. The inset in the top left corner shows the atomic structure of one gold nanocluster.

Here’s a link to and a citation for the paper,

Template-Free Supracolloidal Self-Assembly of Atomically Precise Gold Nanoclusters: From 2D Colloidal Crystals to Spherical Capsids by Dr. Nonappa, Dr. Tanja Lahtinen, M. Sc. Johannes. S. Haataja, Dr. Tiia-Riikka Tero, Prof. Hannu Häkkinen, and Prof. Olli Ikkala. Angewandte Chemie International Edition Volume 55, Issue 52, pages 16035–16038, December 23, 2016 Version of Record online: 23 NOV 2016 DOI: 10.1002/anie.201609036

© 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

This paper is behind a paywall.

Ocean-inspired coatings for organic electronics

An Oct. 19, 2016 news item on phys.org describes the advantages a new coating offers and the specific source of inspiration,

In a development beneficial for both industry and environment, UC Santa Barbara [University of California at Santa Barbara] researchers have created a high-quality coating for organic electronics that promises to decrease processing time as well as energy requirements.

“It’s faster, and it’s nontoxic,” said Kollbe Ahn, a research faculty member at UCSB’s Marine Science Institute and corresponding author of a paper published in Nano Letters.

In the manufacture of polymer (also known as “organic”) electronics—the technology behind flexible displays and solar cells—the material used to direct and move current is of supreme importance. Since defects reduce efficiency and functionality, special attention must be paid to quality, even down to the molecular level.

Often that can mean long processing times, or relatively inefficient processes. It can also mean the use of toxic substances. Alternatively, manufacturers can choose to speed up the process, which could cost energy or quality.

Fortunately, as it turns out, efficiency, performance and sustainability don’t always have to be traded against each other in the manufacture of these electronics. Looking no further than the campus beach, the UCSB researchers have found inspiration in the mollusks that live there. Mussels, which have perfected the art of clinging to virtually any surface in the intertidal zone, serve as the model for a molecularly smooth, self-assembled monolayer for high-mobility polymer field-effect transistors—in essence, a surface coating that can be used in the manufacture and processing of the conductive polymer that maintains its efficiency.

An Oct. 18, 2016 UCSB news release by Sonia Fernandez, which originated the news item, provides greater technical detail,

More specifically, according to Ahn, it was the mussel’s adhesion mechanism that stirred the researchers’ interest. “We’re inspired by the proteins at the interface between the plaque and substrate,” he said.

Before mussels attach themselves to the surfaces of rocks, pilings or other structures found in the inhospitable intertidal zone, they secrete proteins through the ventral grove of their feet, in an incremental fashion. In a step that enhances bonding performance, a thin priming layer of protein molecules is first generated as a bridge between the substrate and other adhesive proteins in the plaques that tip the byssus threads of their feet to overcome the barrier of water and other impurities.

That type of zwitterionic molecule — with both positive and negative charges — inspired by the mussel’s native proteins (polyampholytes), can self-assemble and form a sub-nano thin layer in water at ambient temperature in a few seconds. The defect-free monolayer provides a platform for conductive polymers in the appropriate direction on various dielectric surfaces.

Current methods to treat silicon surfaces (the most common dielectric surface), for the production of organic field-effect transistors, requires a batch processing method that is relatively impractical, said Ahn. Although heat can hasten this step, it involves the use of energy and increases the risk of defects.

With this bio-inspired coating mechanism, a continuous roll-to-roll dip coating method of producing organic electronic devices is possible, according to the researchers. It also avoids the use of toxic chemicals and their disposal, by replacing them with water.

“The environmental significance of this work is that these new bio-inspired primers allow for nanofabrication on silicone dioxide surfaces in the absence of organic solvents, high reaction temperatures and toxic reagents,” said co-author Roscoe Lindstadt, a graduate student researcher in UCSB chemistry professor Bruce Lipshutz’s lab. “In order for practitioners to switch to newer, more environmentally benign protocols, they need to be competitive with existing ones, and thankfully device performance is improved by using this ‘greener’ method.”

Here’s a link to and a citation for the research paper,

Molecularly Smooth Self-Assembled Monolayer for High-Mobility Organic Field-Effect Transistors by Saurabh Das, Byoung Hoon Lee, Roscoe T. H. Linstadt, Keila Cunha, Youli Li, Yair Kaufman, Zachary A. Levine, Bruce H. Lipshutz, Roberto D. Lins, Joan-Emma Shea, Alan J. Heeger, and B. Kollbe Ahn. Nano Lett., 2016, 16 (10), pp 6709–6715
DOI: 10.1021/acs.nanolett.6b03860 Publication Date (Web): September 27, 2016

Copyright © 2016 American Chemical Society

This paper is behind a paywall but the scientists have made an illustration available,

An artist's concept of a zwitterionic molecule of the type secreted by mussels to prime surfaces for adhesion Photo Credit: Peter Allen

An artist’s concept of a zwitterionic molecule of the type secreted by mussels to prime surfaces for adhesion Photo Credit: Peter Allen

Lawrence Berkeley National Laboratory (US) and five of its nanoscience projects

An Aug 3, 2016 Lawrence Berkeley National Laboratory news release (also on Azonano as an Aug. 5, 2016 news item) features a selection of their nanoscience projects (Note: Links, embedded images, and embedded videos have been removed),

1. A DIY paint-on coating for energy efficient windows

This “cool” DIY retrofit tech could improve the energy efficiency of windows and save money. Researchers are developing a polymer-based heat-reflective coating that makes use of the unusual molecular architecture of a polymer.

It has the potential to be painted on windows at one-tenth the cost of current retrofit approaches. Window films on the market today reflect infrared solar energy back to the sky while allowing visible light to pass through, but a professional contractor is needed to install them. A low-cost option could significantly expand adoption and result in potential annual energy savings equivalent to taking 5 million cars off the road.

2. Nanowires that move data at light speed

Researchers have found a new way to produce nanoscale wires that can serve as tiny, tunable lasers. The excellent performance of these tiny lasers is promising for the field of optoelectronics, which is focused on combining electronics and light to transmit data, among other applications. Miniaturizing lasers to the nanoscale could further revolutionize computing, bringing light-speed data transmission to desktop, and ultimately, handheld computing devices.

3. Nano sponges that fight climate change

Scientists are developing nano sponges that could capture carbon from power plants before it enters the atmosphere. Initial tests show the hybrid membrane, composed of nano-sized cages (called metal-organic frameworks) and a polymer, is eight times more carbon dioxide permeable than membranes composed only of the polymer.

Boosting carbon dioxide permeability is a big goal in efforts to develop carbon capture materials that are energy efficient and cost competitive. Watch this video for more on this technology.

4. Custom-made chemical factories

Scientists have recently reengineered a building block of a nanocompartment that occurs naturally in bacteria, greatly expanding the potential of nanocompartments to serve as custom-made chemical factories. Researchers hope to tailor this new use to produce high-value chemical products, such as medicines, on demand

The sturdy nanocompartments are formed by hundreds of copies of just three different types of proteins. Their natural counterparts, known as bacterial microcompartments, encase a wide variety of enzymes that carry out highly specialized chemistry in bacteria.

5. Nanotubes that assemble themselves

Researchers have discovered a family of nature-inspired polymers that, when placed in water, spontaneously assemble into hollow crystalline nanotubes. What’s more, the nanotubes can be tuned to all have the same diameter of between five and ten nanometers.

Controlling the diameter of nanotubes, and the chemical groups exposed in their interior, enables scientists to control what goes through. Nanotubes have the potential to be incredibly useful, from delivering cancer-fighting drugs inside cells to desalinating seawater.

It’s nice to see projects grouped together like that as it gives you a bigger picture of what’s taking place at the lab than you’re likely to get reading news releases about individual projects and breakthroughs.

Berkeley Lab has also got an introductory video which does one of the best jobs I’ve seen of conveying the concept of the nanoscale,

H/t to Aug. 10, 2016 news item on Nanowerk for the Berkeley Lab’s ‘nano penny’ video.