Tag Archives: nanostructures

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.

Material that sheds like a snake when it’s damaged

Truly water-repellent materials are on the horizon. Or, they would be if one tiny problem was solved. According to a May  3, 2017 news item on ScienceDaily, scientists may have come up with that solution,

Imagine a raincoat that heals a scratch by shedding the part of the outer layer that’s damaged. To create such a material, scientists have turned to nature for inspiration. They report in ACS’ journal Langmuir a water-repellant material that molts like a snake’s skin when damaged to reveal another hydrophobic [water-repellent] layer beneath it.

A May 3, 2017 American Chemical Society (ACS) press release (also on EurekAlert), which originated the news item, expands on the theme,

Lotus leaves, water striders and other superhydrophobic examples from nature have inspired scientists to copy their water-repelling architecture to develop new materials. Such materials are often made by coating a substrate with nanostructures, which can be shored up by adding microstructures to the mix. Superhydrophobic surfaces could be useful in a range of applications including rain gear, medical instruments and self-cleaning car windows. But most of the prototypes so far haven’t been strong enough to stand up to damage by sharp objects. To address this shortcoming, Jürgen Rühe and colleagues again found a potential solution in nature — in snake and lizard skins.

The researchers stacked three layers to create their material: a water-repellant film made with poly-1H,1H,2H,2H-perfluorodecyl acrylate (PFA) “nanograss” on the top, a water-soluble polymer in the middle and a superhydrophobic silicon nanograss film on the bottom. Nanograss consists of tiny needle-like projections sticking straight up. The team scratched the coating and submerged the material in water, which then seeped into the cut and dissolved the polymer. The top layer then peeled off like molted skin and floated away, exposing the bottom, water-repellant film. Although further work is needed to strengthen the top coating so that a scratch won’t be able to penetrate all three layers, the researchers say it offers a new approach to creating self-cleaning and water-repellant materials.

The authors acknowledge support from the German Federal Ministry of Education and Research (BMBF) and VDI/VDE/IT GmbH through project NanoTau.

Here’s a video demonstrating the concept,

Published on May 2, 2017

Scientists turn to snakes and lizards for inspiration to create a new material that sheds its outer layer when scratched.

Finally, a link to and a citation for the paper,

Molting Materials: Restoring Superhydrophobicity after Severe Damage via Snakeskin-like Shedding by Roland Hönes, Vitaliy Kondrashov, and Jürgen Rühe. Langmuir, Article ASAP DOI: 10.1021/acs.langmuir.7b00814 Publication Date (Web): April 14, 2017

Copyright © 2017 American Chemical Society

This paper is behind a paywall.

Noniridescent photonics inspired by tarantulas

Last year, I was quite taken with a structural colour story centering on tarantulas which was featured in my Dec. 7, 2015 posting.

Cobalt Blue Tarantula [downloaded from http://www.tarantulaguide.com/tarantula-pictures/cobalt-blue-tarantula-4/]

Cobalt Blue Tarantula [downloaded from http://www.tarantulaguide.com/tarantula-pictures/cobalt-blue-tarantula-4/]

On Oct. 17, 2016 I was delighted to receive an email with the latest work from the same team who this time around crowdfunded resources to complete their research. Before moving on to the paper, here’s more from the team’s crowdfunder on Experiment was titled “The Development of Non-iridescent Structurally Colored Material Inspired by Tarantula Hairs,”

Many vibrant colors in nature are produced by nanostructures rather than pigments. But their application is limited by iridescence – changing hue and brightness with viewing angles. This project aims to mimic the nanostructures that tarantulas use to produce bright, non-iridescent blue colors to inspire next-generation, energy efficient, wide-angle color displays. Moreover, one day non-iridescent structural colorants may replace costly and toxic pigments and dyes.

What is the context of this research?

We recently discovered that some tarantulas produce vivid blue colors using unique nanostructures not found in other blue organisms like birds and Morpho butterflies. We described a number of different nanostructures that help explain how blue color evolved at least eight times within tarantulas. These colors are also remarkably non-iridescent so that they stay bright blue even at wide viewing angles, unlike the “flashy” structural colors seen in many birds and butterflies. We hypothesize that although the hue is produced by multilayer nanostructure, it is the hierarchical morphology of the hairs controls iridescence. We would like to validate our results from preliminary optical simulations by making nano-3D printed physical prototypes with and without key features of the tarantula hairs.

What is the significance of this project?

While iridescence can make a flashy signal to a mating bird or butterfly, it isn’t so useful in optical technology. This limits the application of structural colors in human contexts, even though they can be more vibrant and resist fading better than traditional pigment-based colors. For example, despite being energy efficient and viewable in direct sunlight, this butterfly-inspired color display, that utilizes principles of structural colors, has never made it into the mainstream because iridescence limits its viewing angle. We believe this limitation could be overcome using tarantula-inspired nanostructures that could be mass-produced in an economically viable way through top-down approaches. Those nanostructures may even be used to replace pigments and dyes someday!

What are the goals of the project?

We have designed five models that vary in complexity, incorporating successively more details of real tarantula hairs. We would like to fabricate those five designs by 3D nano-printing, so that we can test our hypothesis experimentally and determine which features produce blue and which remove iridescence. We’ll start making those designs as soon as we reach our goal and the project is fully funded. Once these designs are made, we will compare the angle-dependency of the colors produced by each design through angle-resolved reflectance spectrometry. We’ll also compare them visually through photography by taking series of shots from different angles similar to Fig. S4. Through those steps, we’ll be able to identify how each feature of the complex nanostructure contributes to color.

Budget
Ultra-high resolution (nano-scale) 3D printing
$6,000
To fund nano 3D printing completely
$1,700

This project has been designed using Biomimicry Thinking, and is a follow-up to our published, well-received tarantula research. In order to test our hypothesis, we are planning to use Photonic Professional GT by nanoscribe to fabricate tarantula hair-inspired prototypes by 3D printing nanostructures within millimeter sized swatches. To be able to 3D print nanostructures across these relatively large-sized swatches is critical to the success of our project. Currently, there’s no widely-accessible technology out there that meets our needs other than Photonic Professional GT. However, the estimated cost just for 3D printing those nanostructures alone is $20,000. So far, we have successfully raised and allocated $13,000 of research funds through conventional means, but we are still $7,000 short. Initial trial of our most complex prototype was a success. Therefore, we’re here, seeking your help. Please help us make this nano fabrication happen, and make this project a success! Thank you!

The researchers managed to raise $7, 708.00 in total, making this paper possible,

Tarantula-Inspired Noniridescent Photonics with Long-Range Order by Bor-Kai Hsiung, Radwanul Hasan Siddique, Lijia Jiang, Ying Liu, Yongfeng Lu, Matthew D. Shawkey, and Todd A. Blackledge. Advanced Materials DOI: 10.1002/adom.201600599 Version of Record online: 11 OCT 2016

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

This paper is behind a paywall but I did manage to get my hands on a copy. So here are a few highlights from the paper,

Pigment-based colorants are used for applications ranging from textiles to packaging to cosmetics.[1] However, structural-based alternatives can be more vibrant, durable, and eco-friendly relative to pigmentary colors.[2] Moreover, optical nanostructures are highly tunable, they can achieve a full color gamut by slight alterations to spacing.[3] However, light interference and/or diffraction from most photonic structures results in iridescence,[4] which limits their broader applications. Iridescent colors that change hue when viewed from different directions are useful for niche markets, such as security and anticounterfeiting, {emphasis mine} [5] but are not desirable for most applications, such as paints, coatings, electronic displays, and apparels. Hence, fabricating a photonic structure that minimizes iridescence is a key step to unlocking the potential applications of structural colors.

Noniridescent structural colors in nature are produced by coherent scattering of light by quasi-ordered, amorphous photonic structures (i.e., photonic glass),[6–10] or photonic polycrystals [9,11–14] that possess only short-range order. Iridescence is thought to be a fundamental component of photonic structures with long-range order, such as multilayers.[4] However, the complexity of short-range order photonic structures prohibits their design and fabrication using top-down approaches while bottom-up synthesis using colloidal suspension[15,16] or self-assembly[17–20] lack the tight controls over the spatial and temporal scales needed for industrial mass production. Photonic structures with long-range order are easier to model mathematically. Hence, long-range order photonic structures are intrinsically suitable for top-down fabrication, where precise feature placement and scalability can be guaranteed.

Recently, we found blue color produced by multilayer interference on specialized hairs from two species of blue tarantulas (Poecilotheria metallica (Figure 1a,b) and Lampropelma violaceopes) that was largely angle independent.[21] We hypothesize that the iridescent effects of the multilayer are reduced by hierarchical structuring of the hairs. Specifically, the hairs have: (1) high degrees of rotational symmetry, (2) hierarchy—with subcylindrical multilayers surrounding a larger, overarching multilayer cylinder, and (3) nanoscale surface grooves. Because all of these structures co-occur on the tarantulas, it is impossible to decouple them simply by observing nature. Here, we use optical simulation and nano-3D rapid prototyping to demonstrate that introducing design features seen in these tarantulas onto a multilayer photonic structure nearly eliminates iridescence. As far as we are aware, this is the first known example of a noniridescent structural color produced by a photonic structure with both short and long-range order. This opens up an array of new possibilities for photonic structure design and fabrication to produce noniridescent structural colors and is a key first step to achieving economically viable solutions for mass production of noniridescent structural color.  … (p. 1 PDF)

There is a Canadian security and anti-counterfeiting company (Nanotech Security Corp.), inspired by the Morpho butterfly and its iridescent blue, which got its start in Bozena Kaminska’s laboratory at Simon Fraser University (Vancouver, Canada).

Getting back to the paper, after a few twists and turns, they conclude with this,

This approach of producing noniridescent structural colors using photonic structures with long-range order (i.e., modified multilayer) has, to our knowledge, not been explored previously. Our findings reaffirm the value of using nature and the biomimetic process as a tool for innovation and our approach also may help to overcome the current inability of colloidal self-assembly to achieve pure noniridescent structural red due to single-particle scattering and/or multiple scattering.[25] As a result, our research provides a new and easy way for designing structural colorants with customizable hues (see Figure S6, Supporting Information, as one of the potential examples) and iridescent effects to satisfy the needs of different applications. While nano-3D printing of these nanostructures is not viable for mass production, it does identify the key features that are necessary for top-down fabrication. With promising nanofabrication techniques, such as preform drawing[26]—a generally scalable methodology that has been demonstrated for fabricating particles with complex internal architectures and continuously tunable diameters down to nanometer scale[27] – it is possible to mass produce these “designer structural colorants” in an economically viable manner. Our discovery of how to produce noniridescent structural colors using long-range order may therefore lead to a more sustainable future that does not rely upon toxic and wasteful synthetic pigments and dyes. (p. 5)

I’m glad to have gotten caught up with the work. Thank you, Bor-Kai Hsiung.

Nature-inspired but not really, a new design rule for nanostructures

It’s fascinating to observe the news release writer’s attempt to package this research as biomimetic when the new design rule is not found in nature. An Oct. 7, 2015 news item on ScienceDaily provides an introduction to the work from the Lawrence Berkeley National Laboratory,

Scientists aspire to build nanostructures that mimic the complexity and function of nature’s proteins. These microscopic widgets could be customized into incredibly sensitive chemical detectors or long-lasting catalysts. But as with any craft that requires extreme precision, researchers must first learn how to finesse the materials they’ll use to build these structures. A new discovery is a big step in this direction. The scientists discovered a design rule that enables a recently created material to exist.

An Oct. 7, 2015 Lawrence Berekeley National Laboratory (Berkeley Lab) news release (also on EurekAlert), which originated the news item, features more detail about the research and the writer’s gyrations,

The scientists discovered a design rule that enables a recently created material to exist. The material is a peptoid nanosheet. It’s a flat structure only two molecules thick, and it’s composed of peptoids, which are synthetic polymers closely related to protein-forming peptides.

The design rule controls the way in which polymers adjoin to form the backbones that run the length of nanosheets. Surprisingly, these molecules link together in a counter-rotating pattern not seen in nature. [emphasis mine] This pattern allows the backbones to remain linear and untwisted, a trait that makes peptoid nanosheets larger and flatter than any biological structure.

The Berkeley Lab scientists say this never-before-seen design rule could be used to piece together complex nanosheet structures and other peptoid assemblies such as nanotubes and crystalline solids.

What’s more, they discovered it by combining computer simulations with x-ray scattering and imaging methods to determine, for the first time, the atomic-resolution structure of peptoid nanosheets.

“This research suggests new ways to design biomimetic structures, [emphasis mine]” says Steve Whitelam, a co-corresponding author of the Nature paper. “We can begin thinking about using design principles other than those nature offers.”

The news release goes on to note the previous work which this newest research builds on and provides yet more detail about the latest and greatest,

Peptoid nanosheets were discovered by Zuckermann’s group five years ago. They found that under the right conditions, peptoids self assemble into two-dimensional assemblies that can grow hundreds of microns across. This “molecular paper” has become a hot prospect as a protein-mimicking platform for molecular design.

To learn more about this potential building material, the scientists set out to learn its atom-resolution structure. This involved feedback between experiment and theory. Microscopy and scattering data gathered at the Molecular Foundry and the Advanced Light Source, also a DOE Office of Science user facility located at Berkeley Lab, were compared with molecular dynamics simulations conducted at NERSC.

The research revealed several new things about peptoid nanosheets. Their molecular makeup varies throughout their structure, they can be formed only from peptoids of a certain minimum length, they contain water pockets, and they are potentially porous when it comes to water and ions.

These insights are intriguing on their own, but when the scientists examined the structure of the nanosheets’ backbone, they were surprised to see a design rule not found in the field of protein structural biology.

Here’s the difference: In nature, proteins are composed of beta sheets and alpha helices. These fundamental building blocks are themselves composed of backbones, and the polymers that make up these backbones are all joined together using the same rule. Each adjacent polymer rotates incrementally in the same direction, so that a twist runs along the backbone.

This rule doesn’t apply to peptoid nanosheets. Along their backbones, adjacent monomer units rotate in opposite directions. These counter-rotations cancel each other out, resulting in a linear and untwisted backbone. This enables backbones to be tiled in two dimensions and extended into large sheets that are flatter than anything nature can produce.

“It was a big surprise to find the design rule that makes peptoid nanosheets possible has eluded the field of biology until now,” says Mannige [Ranjan Mannige, a postdoctoral researcher at the Molecular Foundry]. “This rule could perhaps be used to build many more unrealized structures.”

Adds Zuckermann [Peptoid nanosheets were discovered by Zuckermann’s group five years ago. They found that under the right conditions, peptoids self assemble into two-dimensional assemblies that can grow hundreds of microns across. This “molecular paper” has become a hot prospect as a protein-mimicking platform for molecular design.

To learn more about this potential building material, the scientists set out to learn its atom-resolution structure. This involved feedback between experiment and theory. Microscopy and scattering data gathered at the Molecular Foundry and the Advanced Light Source, also a DOE Office of Science user facility located at Berkeley Lab, were compared with molecular dynamics simulations conducted at NERSC.

The research revealed several new things about peptoid nanosheets. Their molecular makeup varies throughout their structure, they can be formed only from peptoids of a certain minimum length, they contain water pockets, and they are potentially porous when it comes to water and ions.

These insights are intriguing on their own, but when the scientists examined the structure of the nanosheets’ backbone, they were surprised to see a design rule not found in the field of protein structural biology.

Here’s the difference: In nature, proteins are composed of beta sheets and alpha helices. These fundamental building blocks are themselves composed of backbones, and the polymers that make up these backbones are all joined together using the same rule. Each adjacent polymer rotates incrementally in the same direction, so that a twist runs along the backbone.

This rule doesn’t apply to peptoid nanosheets. Along their backbones, adjacent monomer units rotate in opposite directions. These counter-rotations cancel each other out, resulting in a linear and untwisted backbone. This enables backbones to be tiled in two dimensions and extended into large sheets that are flatter than anything nature can produce.

“It was a big surprise to find the design rule that makes peptoid nanosheets possible has eluded the field of biology until now,” says Mannige. “This rule could perhaps be used to build many more unrealized structures.”

Adds Zuckermann, [Ron Zuckermann directs the Molecular Foundry’s Biological Nanostructures Facility.] “We also expect there are other design principles waiting to be discovered, which could lead to even more biomimetic nanostructures.”

They might have been better off describing the work as “bioinspired” but it is a tricky thing to describe and there doesn’t seem to be an easy way out of describing this discovery which is based on observations from nature but follows no rule found in nature.

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

Peptoid nanosheets exhibit a new secondary-structure motif by Ranjan V. Mannige, Thomas K. Haxton, Caroline Proulx, Ellen J. Robertson, Alessia Battigelli, Glenn L. Butterfoss, Ronald N. Zuckermann, & Stephen Whitelam. Nature (2015) doi:10.1038/nature15363 Published online 07 October 2015

This paper is behind a paywall.

Qualitative and quantitative understanding of nanostructures by University of BC researchers

It’s not the sexiest research (no nanobots, no self-cleaning windows, no textiles with colours never seen before on fabrics, no heating up a tumour to destroy it, etc.)  I’ve come across but developing a model that predicts a nanostructure’s optical properties is likely to prove valuable. According to the University of British Columbia Chemistry Department researchers the models could be useful with the “design of tailored nano-structures, and be of utility in a wide range of fields, including the remote sensing of atmospheric pollutants and the study of cosmic dust formation.”

From the March 24, 2011 news item on Nanowerk,

Now research published this week by UBC chemists indicates that the optical properties of more complex non-conducting nano-structures can be predicted based on an understanding of the simple nano-objects that make them up. Those optical properties in turn give researchers and engineers an understanding of the particle’s structure.

“Engineering complex nano-structures with particular infrared responses typically involves hugely complex calculations and is a bit hit and miss,” says Thomas Preston, a researcher with the UBC Department of Chemistry.

“Our solution is a relatively simple model that could help guide us in more efficiently engineering nano-materials with the properties we want, and help us understand the properties of these small particles that play an important role in so many processes.”

The findings were published this week in the Proceedings of the National Academy of Sciences (“Vibron and phonon hybridization in dielectric nanostructures”).

“For example, the properties of a more complex particle made up of a cavity and a core structure can be understood as a hybrid of the individual pieces that make it up,” says UBC Professor Ruth Signorell, an expert on the characterization of molecular nano-particles and aerosols and co-author of the study.

The experiment also tested the model against CO2 aerosols with a cubic shape, which play a role in cloud formation on Mars.

The paper, Vibron and phonon hybridization in dielectric nanostructures, is behind a Proceedings of the National Academy of Sciences paywall but an abstract is available here.

Walking on eggshells? and sunshine too?

Tissue scaffolding, egg shells, and nanostructures all come together in work being done by Ryerson University (Toronto, Ontario, Canada) researchers Bo Tan and Krishnan Venkatakrishnan. From the Feb. 28, 2011 news item on physorg.com,

… Venkatakrishnan and Tan first began studying nanostructures within micro-electronics. More recently, though, the researchers have started developing nanostructures using a variety of materials.

One example: the pair’s research on eggshell-based nanostructures – co-authored with Ryerson PhD candidate Amirhossein Tavangar – was published last month in the Journal of Nanobiotechnology. But eggshells aren’t the only materials that can support nanostructures; bones and other natural bio-materials are also being studied in Venkatakrishnan and Tan’s lab.

Typically, fragile ceramics or rigid polymers are used in surgery to fix broken, old or cancer-damaged bones. Nanostructures embedded within actual bones, however, offer a better solution and can help “glue” deteriorated or fragmented bones back together. Through a biomedical process called tissue scaffolding, a porous, artificially created material is used to simulate real tissue and stimulate new bone growth in the body – something that other grafting materials are limited in their capacity to do.

This couple (partners in research and in life) are also working on solar energy panels and water quality monitoring as part of their investigations into nanostructures. I recommend reading this article for a good general introduction about how multidisciplinary research on nanostructures can be applied to many fields.

After writing my headline about “walking on eggshells” I was reminded of a song, “Walking on Sunshine” by Katrina and the Waves. Enjoy a happy weekend,