Tag Archives: W. M. Keck Foundation

Sea sapphires: now you see them, now you don’t and more about structural colour/color

The structural colour of the sea sapphire

 Scientists are studying the disappearing act of this ocean-dwelling copepod. Credit: Kaj Maney, www.liquidguru.com Courtesy: American Chemical Society


Scientists are studying the disappearing act of this ocean-dwelling copepod.
Credit: Kaj Maney, www.liquidguru.com Courtesy: American Chemical Society

Now, you’ve seen a sea sapphire. Here’s more about them and the interest they hold for experts in photonics, from a July 15, 2015 news item on ScienceDaily,

Sapphirina, or sea sapphire, has been called “the most beautiful animal you’ve never seen,” and it could be one of the most magical. Some of the tiny, little-known copepods appear to flash in and out of brilliantly colored blue, violet or red existence. Now scientists are figuring out the trick to their hues and their invisibility. The findings appear in the Journal of the American Chemical Society and could inspire the next generation of optical technologies.

A July 15, 2015 American Chemical Society (ACS) news release, which originated the news item, provides more detail,

Copepods are tiny aquatic crustaceans that live in both fresh and salt water. Some males of the ocean-dwelling Sapphirina genus display striking, iridescent colors that scientists think play a role in communication and mate recognition. The shimmering animals’ colors result when light bounces off of the thin, hexagonal crystal plates that cover their backs. These plates also help them vanish, if only fleetingly. Scientists didn’t know specifically what factors contributed to creating different shades. Scientists at the Weizmann Institute [Israel] and the Interuniversity Institute for Marine Sciences in Eilat [Israel] wanted to investigate the matter.

The researchers measured the light reflectance — which determines color — of live Sapphirina males and the spacing between crystal layers. They found that changes of reflectance depended on the thickness of the spacing. And for at least one particular species, when light hits an animal at a 45-degree angle, reflectance shifts out of the visible light range and into the ultraviolet, and it practically disappears. Their results could help inform the design of artificial photonic crystal structures, which have many potential uses in reflective coatings, optical mirrors and optical displays.

To sum this up, the colour and the invisibility properties are due to thin, hexagonal crystal plates and the spacing of these plates, in other words, structural colour, which is usually achieved at the nanoscale.

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

Structural Basis for the Brilliant Colors of the Sapphirinid Copepods by Dvir Gur, Ben Leshem, Maria Pierantoni, Viviana Farstey, Dan Oron, Steve Weiner, and Lia Addadi. J. Am. Chem. Soc., 2015, 137 (26), pp 8408–8411 DOI: 10.1021/jacs.5b05289 Publication Date (Web): June 22, 2015

Copyright © 2015 American Chemical Society

This paper is behind a paywall.

For anyone who’s interested, Lynn Kimlicka has a nice explanation of structural colour in a July 22, 2015 posting on the Something About Science blog where she discusses some recent research iridescence in bird feathers and synthetic melanin. She also shares a picture of her budgie and its iridescent feathers. The ‘melanin’ research was mentioned here in a May 19, 2015 posting where I also provide a link to a great 2013 piece on structural throughout the animal and plant kingdoms by Cristina Luiggi for The Scientist.

Understanding how nanostructures can affect optical properties could be leading to new ways of managing light. A July 23, 2015 news item on ScienceDaily describes a project at the University of Delaware dedicated to “changing the color of light,”

Researchers at the University of Delaware have received a $1 million grant from the W.M. Keck Foundation to explore a new idea that could improve solar cells, medical imaging and even cancer treatments. Simply put, they want to change the color of light.

A July 23, 2015 University of Delaware (UD) news release, which originated the news item, provides more information about the proposed research,

“A ray of light contains millions and millions of individual units of light called photons,” says project leader Matthew Doty. “The energy of each photon is directly related to the color of the light — a photon of red light has less energy than a photon of blue light. You can’t simply turn a red photon into a blue one, but you can combine the energy from two or more red photons to make one blue photon.”

This process, called “photon upconversion,” isn’t new, Doty says. However, the UD team’s approach to it is.

They want to design a new kind of semiconductor nanostructure that will act like a ratchet. It will absorb two red photons, one after the other, to push an electron into an excited state when it can emit a single high-energy (blue) photon.

These nanostructures will be so teeny they can only be viewed when magnified a million times under a high-powered electron microscope.

“Think of the electrons in this structure as if they were at a water park,” Doty says. “The first red photon has only enough energy to push an electron half-way up the ladder of the water slide. The second red photon pushes it the rest of the way up. Then the electron goes down the slide, releasing all of that energy in a single process, with the emission of the blue photon. The trick is to make sure the electron doesn’t slip down the ladder before the second photon arrives. The semiconductor ratchet structure is how we trap the electron in the middle of the ladder until the second photon arrives to push it the rest of the way up.”

The UD team will develop new semiconductor structures containing multiple layers of different materials, such as aluminum arsenide and gallium bismuth arsenide, each only a few nanometers thick. This “tailored landscape” will control the flow of electrons into states with varying potential energy, turning once-wasted photons into useful energy.

The UD team has shown theoretically that their semiconductors could reach an upconversion efficiency of 86 percent, which would be a vast improvement over the 36 percent efficiency demonstrated by today’s best materials. What’s more, Doty says, the amount of light absorbed and energy emitted by the structures could be customized for a variety of applications, from lightbulbs to laser-guided surgery.

How do you even begin to make structures so tiny they can only be seen with an electron microscope? In one technique the UD team will use, called molecular beam epitaxy, nanostructures will be built by depositing layers of atoms one at a time. Each structure will be tested to see how well it absorbs and emits light, and the results will be used to tailor the structure to improve performance.

The researchers also will develop a milk-like solution filled with millions of identical individual nanoparticles, each one containing multiple layers of different materials. The multiple layers of this structure, like multiple candy shells in an M&M, will implement the photon ratchet idea. Through such work, the team envisions a future upconversion “paint” that could be easily applied to solar cells, windows and other commercial products.

Improving medical tests and treatments

While the initial focus of the three-year project will be on improving solar energy harvesting, the team also will explore biomedical applications.

A number of diagnostic tests and medical treatments, ranging from CT [computed tomography] and PET [positron emission tomography] scans to chemotherapy, rely on the release of fluorescent dyes and pharmaceutical drugs. Ideally, such payloads are delivered both at specific disease sites and at specific times, but this is hard to control in practice.

The UD team aims to develop an upconversion nanoparticle that can be triggered by light to release its payload. The goal is to achieve the controlled release of drug therapies even deep within diseased human tissue while reducing the peripheral damage to normal tissue by minimizing the laser power required.

“This is high-risk, high-reward research,” Doty says. “High-risk because we don’t yet have proof-of-concept data. High-reward because it has such a huge potential impact in renewable energy to medicine. It’s amazing to think that this same technology could be used to harvest more solar energy and to treat cancer. We’re excited to get started!”

That’s it for structural colour/color today.

Call for nominations: US National Academies Communication Awards

The Jan. 16, 2013 press release from US National Academies announced a call for nominations for communication in various media including books, film/radio/tv, magazine/newspaper, and online materials that have been published in the US,

The Keck Futures Initiative—a program of the National Academy of Sciences, National Academy of Engineering, and Institute of Medicine, with the support of the W. M. Keck Foundation—will award $20,000 prizes to individuals or teams who have developed creative, original work that addresses issues and advances in science, engineering and/or medicine for the general public. Nominations are accepted in four categories: Book; Film/Radio/TV; Magazine/Newspaper; and Online.

ELIGIBILITY
To be considered for a 2013 Communication Award, the work should:

  • be accessible and appeal to a broad, public audience;
  • demonstrate clarity, creativity, originality, and accuracy;
  • address issues and/or advances in science, engineering, and/or medicine;
  • cover topics that have an impact on society; and
  • have been published, broadcast, or released in 2012, in the United States and in English.

Call For Nominations Now Being Accepted
Nominations will be accepted through February 8, 2013.  For more information about the process, please visit: http://www.keckfutures.org/awards/nominate.html.

NOMINATION FORM
Nominations must be submitted on the online nomination form at http://www.keckfutures.org/awards/nominate.html. Copies of the nominated work must be submitted as described for each category.  Self nominations are permitted. Please submit a nomination in the category that most closely fits the work(s) being nominated.  Supporting materials will not be returned. There is no nomination fee.

BOOK
Books must have been published in the U.S. in 2012 to be considered. Please submit two copies of the book. The publisher and year of publication must be printed on the book. Advance publication dates must include verification from the publisher.

FILM/RADIO/TV
Submissions must have aired on a U.S. station or have been released in U.S. theaters or on DVD in 2012 and may include a single story or movie, a series, or as many as six brief, unrelated stories. Please submit three CDs or DVDs labeled with the nominee’s name(s), the title(s) included on the DVD or CD, and the original airdate (with the name of the U.S. station and the program on which the stories aired) or release date. These must be submitted in protective cases and include authorization allowing the Keck Futures Initiative to reproduce the CD or DVD for review purposes (copyright release). Submission of copies of the program transcript is also encouraged. If you are not able to provide copyright release, please submit an additional 20 copies of the CD or DVD.

MAGAZINE/NEWSPAPER
Work in this category must have been published in the U.S. in 2012, and may comprise a single article or as many as four articles that are unrelated or that constitute a formal series. Please submit three original copies of each article clearly showing the byline and the name and date of the publication and authorization allowing the Keck Futures Initiative to reproduce the article for review purposes (copyright release). If you are not able to provide copyright release, please send an additional 20 copies of the article(s), or a PDF file of the article(s).

ONLINE
Work created specifically for the Web must have been posted online in 2012. Entries may include as many as six online articles, hypertext documents, podcasts, commentaries, etc., or any combination thereof. Preference will be given to nominations that make the best use of the medium, including multi-media presentations that incorporate a combination of videos, blog entries, interactive features, and/or other capabilities unique to this communication medium. Include links to the unique URLs for each work(s). Links, must be active through October 31, 2013.

2013 TIMELINE

  • February 8 – Nomination process closes.
  • Fall 2013 – Winners honored at a ceremony to be held in Washington D.C. Date TBD.

All nominations must be submitted online by February 8, and all supporting materials must be received by February 15, 2013.

For More Information
Visit www.keckfutures.org/awards for a complete listing of this year’s Selection Committee, information about the awards and to nominate.

I wonder if I could self-nominate, despite the fact that I self-identify as a Canadian science blogger; this blog is hosted by a US company. Does that constitute publication in the US? That $20,000 prize is tempting. Good luck to all who enter the competition.

Nanocrystals by design

A trio of researchers from the University of Chicago are looking for ways to design new atoms or nanocrystals according to the Dec. 5, 2012 news item on ScienceDaily,

Three University of Chicago chemistry professors hope that their separate research trajectories will converge to create a new way of assembling what they call “designer atoms” into materials with a broad array of potentially useful properties and functions.

These “designer atoms” would be nanocrystals — crystalline arrays of atoms intended to be manipulated in ways that go beyond standard uses of atoms in the periodic table. Such arrays would be suited to address challenges in solar energy, quantum computing and functional materials.

The partners in the project are Prof. David Mazziotti, and Associate Professors Greg Engel and Dmitri Talapin. All three have made key advances that are critical for moving the project forward. Now, with $1 million in funding from the W. M. Keck Foundation, they can build on their separate advances in a concerted way toward a new goal.

The Dec. 4, 2012 University of Chicago news release by Stephen Koppes, which originated the news item, provides some excellent descriptions of the science (thank you Stephen), as well as, a description of the work,

Developments in Talapin’s laboratory form the core of the project. A synthetic inorganic chemist, he specializes in creating precisely engineered nanocrystals with well-defined characteristics.

Nanocrystals consist of hundreds or thousands of atoms. This is small enough that new quantum phenomena begin to emerge, but large enough to provide convenient “modules” for the design of new materials. “It’s an interesting combination in that you build materials not from individual atoms, but from the units that resemble atoms in many ways but also behave as a metal, semiconductor or magnet. It’s a bit crazy,” Talapin said.

The potential of the new arrangements may exceed that of existing elements. Chemists cannot tune the properties of hydrogen or helium, for example, but they can tune the properties of nanocrystals.

“You build chemistry from atoms, and quantum mechanics provides principles for doing that,” said Mazziotti, referring to the laws of physics that dominate the world at ultra-small scales. “In the same way, we envision tremendous opportunities in terms of taking nanocrystalline arrays and nanocrystals as the building blocks for new structures where we assemble them into strongly correlated systems.”

The essence of strong correlation, of chemical bonds, of chemistry generally, is the connections between particles and how properties of these particles change as they bind to one another, Engel noted. “It’s about new emerging properties coming from strong mixing between the electronic states of particles, the same way two atoms come together to make a molecule,” he said.

Hydrogen and oxygen gases have very different properties. Yet when two hydrogen atoms share electrons with an oxygen atom, they form water. The UChicago trio’s ambition is to extend this framework from the level of individual atoms to the level of small, functional objects, such as metal or magnetic semiconductors.

The key to their project is controlling the degree of correlation between electrons on different nanocrystals. In 2009, Talapin and his collaborators developed a way to control the motions of electrons as they move from one nanocrystal to the next. Their “electronic glue” enables semiconductor nanocrystals to efficiently transfer their electric charges to one another, an important step in the synthesis of new materials.

Achieving greater control of correlated electrons—those whose motions are linked to each other—on different nanocrystals is the key to success in the Keck project.

Mazziotti and Engel bring theoretical and spectroscopic advances, respectively, to the collaboration. Mazziotti’s advance provides an alternative to traditional approaches to computing strongly correlated electrons in molecules, which scale exponentially with the number of electrons. He has solved a longstanding problem that enables calculations using just two of a molecule’s electrons, which dramatically decreases the computational cost.

His studies of firefly bioluminescence and other phenomena have shown that as molecular systems grow larger, strong correlations between electrons grow more powerful and open new possibilities for emergent behavior. In the context of a semiconducting material such as silicon, emergent behavior is how individual nanoparticles effectively lose their identity, giving rise to collective properties in new materials.

“As the size of a molecular system increases, we see the emergence of new physics behavior and the importance of strong correlation of electrons,” Mazziotti said. “The importance of strong correlation increases dramatically with system size.”

The advance in Engel’s research group was the development of a technique called GRadient-Assisted Photon Echo (GRAPE) spectroscopy, which borrows ideas from magnetic resonance imaging but is used for spectroscopy rather than medical imaging. Engel already has used GRAPE to observe the correlated motion and coupling between chromophores, which are light-absorbing molecules. Now he will apply the technique to nanocrystals.

Over the last 10 days or so, there have been a number of gobsmacking developments, including this one.