Novel Broadband Terahertz Light Emitters

Highlight Date: 
03/28/2014
Display Section: 
Broad Audience Highlights
Article Title: 
Broadband Terahertz Generation from Metamaterials
Author(s): 
L. Luo, I. Chatzakis, J.-G. Wang, F. B. P. Niesler, M. Wegener, T. Koschny and C. M. Soukoulis
Article Link: 
Journal Name: 
Nature Communications
Volume: 
5
Year: 
2014
Page Number(s): 
3055
Project Affiliation: 
Highlight Text: 

Broadband terahertz light emitters have been designed and fabricated using nanoscale U-shaped building blocks. The terahertz spectral range sits between infrared and typical radar frequencies, and the challenges of efficiently generating and detecting terahertz radiation has limited its use.  However, broadband terahertz sources offer exciting possibilities to study fundamental physics principles, to develop non-invasive material imaging and sensing, and make possible terahertz information, communication, processing and storage. The building blocks, known as split ring resonators, are tailored to form nanometer thin, so-called metamaterials.  Split ring resonators, because of the U-shaped design, exhibit a strong magnetic response to wavelengths from the terahertz to infrared range.These new metamaterials could allow integration of terahertz optoelectronics with high-speed telecommunications.

ImageAmes Laboratory senior physicist Costas Soukoulis has been named as the recipient of the 2014 Max Born Award by the Optical Society.

The award is named for Max Born, a German physicist and mathematician who was instrumental in the development of quantum mechanics, solid-state physics and optics and winner of the 1954 Nobel Prize in Physics for his "fundamental research in Quantum Mechanics. The Max Born Award recognizes contributions to physical optics.

ImageSoukoulis is being recognized for "his creative and outstanding theoretical and experimental research in the fields of photonic crystals and left-handed metamaterials and for novel applications of these materials to manipulate electromagnetic radiation."

Soukoulis will receive the award, which includes a medal, certificate and honorarium, at the Optical Society annual meeting in Tucson, Ariz. on Oct. 6.

Contacts:                                                              For release: March 21, 2014
Alex Travesset, Materials Sciences and Engineering, 515-294-7191
Kerry Gibson, Public Affairs, 515-294-1405

Nanoparticles assembled in new ways hold the promise of a wave of new high-tech materials that could offer high strength, enhanced magnetic properties, light reflectivity or absorption, use as catalysts and much more. Scientists at the U.S. Department of Energy’s Ames Laboratory have developed a theoretical model to explore the effect of polymer coatings, including DNA, for self-assembly of nanocubes into so-called superlattices.

What makes the work by Ames Laboratory physicist Alex Travesset and graduate assistant Chris Knorowski significant is that they have characterized how these nanocubes form crystalline and liquid crystalline structures. Their work was published in the Journal of the American Chemical Society and mentioned in an Editor’s Choice article in the January 31 issue of Science.

Image
Using numerical simulations, Ames Lab researchers found that “hairy” (f-star) or DNA grafted on nanocubes provided a general framework to direct the self-assembly into phases with crystalline, liquid crystalline, rotator, or noncrystalline phases with both long-range positional and orientational order.

“Spherical nanoparticles, are isotropic so they can align in any direction,” Travesset explains. “Nanocubes are different. They are anisotropic, so they display orientational order. They will only stack together if the faces orient in certain ways.”

“From a more applied point of view, cubes can pack together more efficiently than spheres; in configurations that do not leave any gaps,” he adds, “so they are of interest in areas such as catalysis where you want to maximize contact area.”

To date scientists had only considered theoretical systems that consist of hard nanocubes. However, by coating nanocubes with strands of polymer, the structures that form are bound together so that they can be extracted and studied in laboratory environments. The nanocubes can be metallic, gold or silver, or made of semiconducting material.

Travesset’s theoretical model uses both a general polymer and DNA. While both resulted in assembly of nanocubes into complex crystalline structures, the DNA system allows control of self-assembly by hybridization of complementary base pairs.

“With DNA, you can encode information about which cubes are going to assemble with which other cubes,” Travesset said. “It gives you a more precise way to target relevant self-assembled structures.”

“Because the system can be polymerized in water, the assembled structure can be extracted and used in dry environments,” Travesset said. “And these complex structures provide much more opportunity for applications and systems than simple hard cubes allow. We hope these systems will lead to further experimentation.”

The research is funded by the DOE’s Office of Science. The Office of Science is the single largest supporter of basic research in the physical sciences in the United States, and is working to address some of the most pressing challenges of our time. For more information, please visit the Office of Science website at science.energy.gov/.

Ames Laboratory is a U.S. Department of Energy Office of Science national laboratory operated by Iowa State University. Ames Laboratory creates innovative materials, technologies and energy solutions. We use our expertise, unique capabilities and interdisciplinary collaborations to solve global problems.

 

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ImageLast month was heart healthy, so let’s go right into how to prepare what we eat. This month is cooking oils. Is “EVOO” (extra virgin olive oil) really the best to cook with? If it is, does that make it the healthiest? And what does extra virgin mean and should you care? Yes, you should. What about good ol’ corn oil? Shouldn’t I support my Iowa farmers? Well, hang on, we’ll cover that.

This article won’t promote one oil over another. It is purely meant to inform and educate the reader. There isn’t one oil that is meant to do it all in your kitchen. You should have several different oils available at all times. For instance, olive oil is horrible when deep frying. Vegetable oil is much better for that purpose.  

Image

 

Here’s the skinny on olive oil:

The darker the color of the oil, the better the yield of the flavor. The best oils will be in dark containers that protect the oil from light. Once opened, it can last a year if kept well sealed in a cool, dry cabinet (even longer if refrigerated or frozen). The highest quality comes from the first pressing of the olives and is known as “extra virgin.”  The next, known as “fine virgin” (or simply “virgin”), comes from the second pressing.  Lower-quality olive oils, including “pure and “light” (the lowest quality) involve processing and refining.

Premium extra-virgin olive oil:

  • Nature’s finest due to extremely low acidity, exquisite aroma and flavor
  • Use in salads, dip for bread, or as a condiment

Extra-virgin olive oil:

  • Fruity taste, may be pale yellow to bright green
  • Best to use in uncooked state to appreciate the flavor

Fine virgin olive oil:

  • Must have good taste and is close in quality to extra-virgin
  • Less expensive than extra-virgin

Virgin and Semifine virgin olive oil:

  • “Good” taste but doesn’t have enough flavor to be enjoyed uncooked
Olive oil has 119 calories in 1 Tblsp.
Total Fat 14 g
Saturated Fat 1.9 g
Polyunsaturated Fat 1.4 g
Monounsaturated Fat 10 g
Cholesterol 0 mg

 

ImageSo what about corn oil? At a recent meeting of the American Society of Nutrition, results of a study comparing corn oil and olive oil were discussed. The study (unpublished and funded by companies that sell corn oil and conducted by a company that does nutritional research for hire) revealed results that after 3 weeks on a diet rich in corn oil, subjects saw an 11% reduction in the LDL (less desirable) cholesterol level compared to 3 weeks on a diet rich in olive oil. The subjects on the olive oil diet only saw a 3.5% reduction in the LDL cholesterol.  Now that doesn’t mean the results aren’t valid, it just means………..what did you expect?

Corn oil is naturally rich in phytosterol, compounds that block the absorption of cholesterol. Olive oil is not. Corn oil is VERY high in polyunsaturated fats, which can help reduce cholesterol levels in your blood BUT this type of fat forms harmful compounds when heated ie. frying.

Corn oil has 122 calories in 1 Tblsp.
Total Fat 14 g
Saturated Fat 1.8 g
Polyunsaturated Fat 7 g
Monounsaturated Fat 3.8 g
Cholesterol 0 mg

 

ImageCanola is grown primarily in the prairie regions of Western Canada, with some acreage being planted in Ontario and the Pacific Northwest. The name "Canola" is a contraction of "Canadian" and "ola", which means oil. Canola oil comes from the seeds of the canola plant. Cabbages, broccoli and cauliflower are also part of this botanical family called Brassica. Canola seeds are crushed and each seed yields approximately 45% oil.  Canola oil has the least saturated fat of any cooking oil. It has half the saturated fat of olive or soybean oil.

Canola oil is ideal for any type of cooking. From salad dressings to sautéing, canola oil's neutral taste and light texture make it a great match for just about everything. Furthermore, its high heat tolerance means you can use canola oil for anything from baking to stir-frying to deep-frying or grilling.

Canola oil has 120 calories in 1 Tblsp.
Total Fat 14 g
Saturated Fat 1 g
Polyunsaturated Fat 4 g
Monounsaturated Fat 8 g
Cholesterol 0 mg

 

ImageAnd now the Miracle of Coconut Oil!!!!

The recent return of a certain someone to our office from an extended stay in Hawaii brings me to the next oil. I’d never heard of it, let alone tried it, but she gave me a sample and I was sold! It’s delicious and addictive. It tastes just like butter. I swear it does.  So, I researched coconut oil for this article and was amazed at what I found.  Coconut oil may have the power to save us from heart disease, arthritis, promote weight loss, and one researcher’s website actually stated on it that it “cured or reversed Alzheimer’s”. I immediately clicked off of there for obvious reasons.  If coconut oil reversed or cured Alzheimer’s, I would have had my Grandma on it. However, I will try it on my Psoriasis and let you know how it works.  I’m not sure if the stuff I spread on my cracker is the same stuff that I spread on my elbows?

Proponents suggest that you replace your regular oil with extra virgin coconut oil to harness all it’s tremendous benefits.

“Don’t do it!,” cry the folks at the National Heart, Lung and Blood Institute and the American Heart Association. Coconut oil contains more saturated fat than any other food--almost twice as much as in butter! Diets high in saturated fat, they point out, can raise your cholesterol and increase your risk of heart disease.

“Ah, yes,” retort the coconut nuts, “but the saturated fats in coconut oil are different than the saturated fats found in butter and meat. They behave completely differently in the body and we have studies to prove it.”

“Oh yeah?” say the saturated fat haters. “We’ll see your study and raise you two studies that show that some people who eat coconut oil actually have increased risk factors for heart disease!”

The truth is that the existing research on how coconut oil might interact with other dietary elements to promote or possibly threaten your health is limited, flawed, and contradictory. Anyone who claims to know with certainty that eating coconut oil will improve your health over the long term is either guessing, ignoring some of the evidence, or both.

Coconut oil has 117 calories in 1 Tblsp.
Total Fat 14 g
Saturated Fat 12 g
Polyunsaturated Fat .2 g
Monounsaturated Fat .8 g
Cholesterol 0 mg

I could go on and provide information on more oils, but I think you get the point. As with anything, when consumed in moderation and as part of a healthy diet and lifestyle, any oil is probably neither a dietary devil nor a nutritional savior. It’s just another piece of the big puzzle we call L I F E.

 

Enjoy!

Jean Johnson and Your friends in Occupational Medicine.

ImageOne thing Andreja Bakac knows about her 37 years as a chemist—it has been beautiful.

“There is a lot of beauty to chemistry, the kind that anyone can appreciate. You don’t have to be a scientist to see it,” she said.

“I love the colors.  Inorganic compounds cover the entire spectrum, from sky blue to emerald green, purple, yellow and everything in between.  Sometimes the hues are different at different concentrations of reagents or when observed from different angles.  And crystals, tiny or large, can take breath-taking shapes and colors.”

Bakac, a senior scientist for Ames Laboratory and adjunct professor in the Department of Chemistry at Iowa State University, was drawn to the beauty of chemistry in middle school. Though she enjoyed studying other subjects like physics, math, and literature, chemistry had special appeal.

As she gained knowledge in the science, attending the University of Zagreb and University of Leeds, it became clear that it also suited her personality.

“By nature I am not a patient person,” Bakac said. “I can’t wait to see results. Organic chemistry is typically slow, so that you set up an experiment and let it run for hours. In inorganic chemistry, especially the kind we do, reactions are finished in minutes, microseconds, nanoseconds. I like that. A side benefit is that one can do a lot of experiments in a short amount of time.”

The nature of chemical reaction

Bakac has turned that beauty and speed into an entire career exploring and understanding the nature of chemical reactions.

 Her research group studies ways to activate normally unreactive molecular oxygen (02) through the use of specially designed complexes of transition metals, such as iron or cobalt.  The ultimate goal is to develop catalytic oxidations with 02 in ways that are efficient and environmentally friendly, ideally using light as an energy source.

“Oxidation is the most prevalent type of chemical reaction, occurring in nature and useful in industry.  Oxygen is free and all around us.  Light is provided by the sun.  Thus the ingredients are freely available.  What we need to do is to find a way to make them work together toward our goal,” said Bakac.

Another research area for Bakac is the reactivity of nitric oxide (NO), a free radical so vital in biology, medicine, and the environment that it was named “Molecule of the Year” by the journal Science in 1992. Bakac’s  group has produced  and studied several metal-based precursors that use visible light to release NO slowly and in a controlled manner, properties crucial for many applications 

“My  research team and I work to contribute to the basic understanding of how all these reactions happen on the molecular level, how fast they are, what intermediate states are involved, and how the conditions affect the outcome,” said Bakac.“ In-depth understanding of a particular reaction gives you the power to tailor the outcome by changing temperature, pressure, reagent concentrations and other parameters. If you understand it, you can control it.”

Women in chemistry: that’s the way it should be

Though Bakac was developing her research career at a time women faced discrimination in many professional fields, she claims to have never felt it. Instead, she was too busy with her science and coping with the adjustments of moving from the city of Zagreb to a much smaller community in Ames. She came to Iowa State University as a post-doctoral researcher and joined Ames Laboratory in 1976.   

“If the discrimination was there, I never experienced it. I am not saying that it didn’t exist, but I never thought about it. I never saw myself as a woman scientist. I was a teacher and a scientist, no prefixes,” Bakac said.

Reflecting back, she considered her views part of her upbringing.

“My mother worked outside the home. So did my grandmother. I grew up in a family where women were strong and had careers. For me that was the natural order of things,” she said.

Nevertheless, Bakac is aware that women in chemistry are few.  She is the only woman principal investigator in the Catalysis Program at the Ames Lab, and often in her career she’s been the only woman at professional conferences.

 “Several years ago I attended a pre-conference reception where the only other woman in the room was tending the bar. In my younger days I might have been intimidated by the all-men make-up of the conference, but not anymore. Such situations are quite familiar by now, and I had no problem joining the guys at one of the tables.”

But the gender balance is improving as more young women join the field; a number of female graduate students working in the Catalysis Program proves that.

“Chemistry students today don’t think anything of it.  Female students have this attitude ‘I’m a girl, so what?’ You go to chemistry lectures and half of the students are women, and no one’s  making a big deal of it. It’s wonderful, and it’s the way it should be.”

And Bakac takes her students, both male and female, to the same conferences that gave her pause years ago.

“It makes all of them, not just the women but the male students too, see that there is a professional community out there that anybody can be a part of, and that it includes women scientists.”

Making chemistry beautiful in new ways

Bakac will be retiring at the end of the year, and is thinking about the new directions her life will take outside of the lab. While she will include leisure time and travel, Bakac is also thinking about a second calling.

“I’m sure I will miss science. It will be hard to leave the lab, my colleagues and students behind. But science takes all of your time, energy, and enthusiasm, and there comes a point when you start thinking about other things that you are interested in and want to do before it is too late.“

For Bakac that means picking up another thing she finds beauty in: literature. Not only does she have a lengthy backlog of books to read, she’s got a plan to write some of her own.

“I have a diploma in children’s literature, and I’m planning to write for children. I don’t have a specific topic or story just yet, but whatever I write will have a strong science component to it.”

"I am still looking for other things out there as well, things that will excite me, and I know I will find them. My eyes are open and I’m heading forward.”

Ames Lab scientist Andreja Bakac reflects on her career

ImageOne thing Andreja Bakac knows about her 37 years as a chemist—it has been beautiful.

“There is a lot of beauty to chemistry, the kind that anyone can appreciate. You don’t have to be a scientist to see it,” she said.

“I love the colors.  Inorganic compounds cover the entire spectrum, from sky blue to emerald green, purple, yellow and everything in between.  Sometimes the hues are different at different concentrations of reagents or when observed from different angles.  And crystals, tiny or large, can take breath-taking shapes and colors.”

Bakac, a senior scientist for Ames Laboratory and adjunct professor in the Department of Chemistry at Iowa State University, was drawn to the beauty of chemistry in middle school. Though she enjoyed studying other subjects like physics, math, and literature, chemistry had special appeal.

As she gained knowledge in the science, attending the University of Zagreb and University of Leeds, it became clear that it also suited her personality.

“By nature I am not a patient person,” Bakac said. “I can’t wait to see results. Organic chemistry is typically slow, so that you set up an experiment and let it run for hours. In inorganic chemistry, especially the kind we do, reactions are finished in minutes, microseconds, nanoseconds. I like that. A side benefit is that one can do a lot of experiments in a short amount of time.”

The nature of chemical reaction

Bakac has turned that beauty and speed into an entire career exploring and understanding the nature of chemical reactions.

 Her research group studies ways to activate normally unreactive molecular oxygen (02) through the use of specially designed complexes of transition metals, such as iron or cobalt.  The ultimate goal is to develop catalytic oxidations with 02 in ways that are efficient and environmentally friendly, ideally using light as an energy source.

“Oxidation is the most prevalent type of chemical reaction, occurring in nature and useful in industry.  Oxygen is free and all around us.  Light is provided by the sun.  Thus the ingredients are freely available.  What we need to do is to find a way to make them work together toward our goal,” said Bakac.

Another research area for Bakac is the reactivity of nitric oxide (NO), a free radical so vital in biology, medicine, and the environment that it was named “Molecule of the Year” by the journal Science in 1992. Bakac’s  group has produced  and studied several metal-based precursors that use visible light to release NO slowly and in a controlled manner, properties crucial for many applications 

“My  research team and I work to contribute to the basic understanding of how all these reactions happen on the molecular level, how fast they are, what intermediate states are involved, and how the conditions affect the outcome,” said Bakac.“ In-depth understanding of a particular reaction gives you the power to tailor the outcome by changing temperature, pressure, reagent concentrations and other parameters. If you understand it, you can control it.”

Women in chemistry: that’s the way it should be

Though Bakac was developing her research career at a time women faced discrimination in many professional fields, she claims to have never felt it. Instead, she was too busy with her science and coping with the adjustments of moving from the city of Zagreb to a much smaller community in Ames. She came to Iowa State University as a post-doctoral researcher and joined Ames Laboratory in 1976.   

“If the discrimination was there, I never experienced it. I am not saying that it didn’t exist, but I never thought about it. I never saw myself as a woman scientist. I was a teacher and a scientist, no prefixes,” Bakac said.

Reflecting back, she considered her views part of her upbringing.

“My mother worked outside the home. So did my grandmother. I grew up in a family where women were strong and had careers. For me that was the natural order of things,” she said.

Nevertheless, Bakac is aware that women in chemistry are few.  She is the only woman principal investigator in the Catalysis Program at the Ames Lab, and often in her career she’s been the only woman at professional conferences.

 “Several years ago I attended a pre-conference reception where the only other woman in the room was tending the bar. In my younger days I might have been intimidated by the all-men make-up of the conference, but not anymore. Such situations are quite familiar by now, and I had no problem joining the guys at one of the tables.”

But the gender balance is improving as more young women join the field; a number of female graduate students working in the Catalysis Program proves that.

“Chemistry students today don’t think anything of it.  Female students have this attitude ‘I’m a girl, so what?’ You go to chemistry lectures and half of the students are women, and no one’s  making a big deal of it. It’s wonderful, and it’s the way it should be.”

And Bakac takes her students, both male and female, to the same conferences that gave her pause years ago.

“It makes all of them, not just the women but the male students too, see that there is a professional community out there that anybody can be a part of, and that it includes women scientists.”

Making chemistry beautiful in new ways

Bakac will be retiring at the end of the year, and is thinking about the new directions her life will take outside of the lab. While she will include leisure time and travel, Bakac is also thinking about a second calling.

“I’m sure I will miss science. It will be hard to leave the lab, my colleagues and students behind. But science takes all of your time, energy, and enthusiasm, and there comes a point when you start thinking about other things that you are interested in and want to do before it is too late.“

For Bakac that means picking up another thing she finds beauty in: literature. Not only does she have a lengthy backlog of books to read, she’s got a plan to write some of her own.

“I have a diploma in children’s literature, and I’m planning to write for children. I don’t have a specific topic or story just yet, but whatever I write will have a strong science component to it.”

"I am still looking for other things out there as well, things that will excite me, and I know I will find them. My eyes are open and I’m heading forward.”

 

-30-

 

Contacts:
Andreja Bakac, Chemical and Biological Sciences, (515) 294-3544
Laura Millsaps, Public Affairs, (515) 294-3474

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