Crystal of the Week: Silicon!

It’s the fifth annual National Robotics Week celebration, so those of us celebrating International Year of Crystallography realized we could not miss out!  After all, at the National Science Foundation, robots are a big deal! In conjunction with the U.S. Navy and Woods Hole Oceanographic Institution, our Division of Ocean Sciences helped fund recent upgrades and certifications for the retrofitted and rebooted Alvin underwater remotely operated vehicle. Research funded through NSF’s Directorate for Engineering embraces robots big and small: Bin He at University of Minnesota has developed a flying, mind-controlled craft, while Sarah Bergbreiter at the University of Maryland College Park designs insect-like robots smaller than a penny! And through the Advanced Technological Education program, NSF funds continuous improvements to associate degree-granting tech programs throughout the country where thousands of students at these schools learn how to build their own robots!

So how do crystals add up to robots?  It’s all in the chips — the microchips, that is.  For this week’s Crystal of the Week, we focused on the one material that almost all robots have in common – silicon-based microchips (a.k.a., the integrated circuit). Microchip fabrication technology has a long history of NSF support, and many major advances in microchip engineering were developed in American laboratories.

Pure silicon is an electronically neutral insulator (electrically non-conducting). Silicon has a similar electronic structure to carbon, which means the crystal structure of silicon takes on the same form as diamond, called “diamond cubic.” Large, cylindrical, high-purity single crystals of silicon are grown from molten vats of silicon (1500oC!) in a method called “pulling,” also known as the Czochralski process. Various improvements in this process have increased the diameter of the cylindrical silicon crystals that can be pulled from the melt from a once-standard 6 inches to a behemoth 12 inches! Once the large cylindrical crystals have been formed, they are sectioned into very thin slices (less than 1 mm), called silicon wafers. The resulting silicon wafers must be as much as 99.9999999% pure for many applications, including solar technology. However, microchip technology requires silicon wafers to have electrically conducting regions, in addition to the insulating pure silicon.

Those conducting regions are incorporated into silicon chips during subsequent processing steps. Two types of conducting silicon can be fabricated: “n-type” and “p-type,” where electrons and holes are the respective charge carriers. Doping with phosphorus creates “n-type” silicon, whereas doping with boron creates “p-type.” Other dopants can also be used. When silicon is doped, each dopant atom replaces a silicon atom in the lattice. Because dopants can be used to induce conductivity in silicon, the material is known as an extrinsic semi-conductor, i.e., silicon conducts under certain conditions.

Looking at robots from this crystallographic perspective is a bit different. But then again, like so many of our greatest technologies, robotics rely on the most minute details to work successfully and find new ways to move technology forward in trailblazing fashion—clearly a case where the whole robot is far greater than the sum of its very smallest parts.


Jellyfish populations are expanding worldwide. Their growth, reproduction, respiration and prey catch rates are similar to plankton-eating fish. Combined, their increasing numbers and food web impact make it important to better understand their biology and behavior.

Long-time collaborators Sean Colin of Roger Williams University and Jack Costello of Providence College study the comb jellyfishMnemiopsis leidyi. A suspension feeding predator and an invasive species, M. leidyi can impact the entire marine food web.

Since jellyfish feed in the water column, they eat on the move. Colin and Costello’s research reveals M. leidyi has two main ways of swimming: jetting or rowing.

Caption: A body diagram of a comb jellyfish. Credit: Sean Colin, Roger Williams University


Crystal of the Week: Serotonin!

“What,” you say?  Serotonin doesn’t sound like a crystal?  Sure, you are not going to find serotonin amongst your gemstones, crystal rock collections or those stereotypical crystals with extended structures. However, serotonin is, in fact, a molecular crystal.  And a very important one for folks who like to be happy!

Yes, so to celebrate the first anniversary of the Obama Administration’s announcement of the BRAIN Initiative, a brain-y crystal seemed like the right way to celebrate the International Year of Crystallography.

To borrow from the American Chemical Society (ACS), “Serotonin is a monoamine neurotransmitter found in blood, the gastrointestinal tract, and the central nervous system in humans. It also occurs in other animals and many plants. M. M. Rapport and co-workers isolated it from beef serum in 1948.”

Serotonin regulates myriad functions in humans (and other animals), as well as plants.  The most commonly prescribed antidepressants, SSRIs or Selective Serotonin Reuptake Inhibitors, prevent reabsorption (known as reuptake) of neurotransmitter serotonin in the brain. Scientists have found that if we change the balance of serotonin in a person, it in turn helps brain cells better send and receive chemical messages, and that is what can relieve depression.

Serotonin is also associated with regulating aging, reproduction, appetite, growth and sleep in humans. Consequently, you can find derivatives of serotonin in drugs beyond antidepressants, for treating nausea (e.g., after chemotherapy), migraines, psychosis and anxiety.  It is also infamously linked to psychotropic drugs as well, such as LSD and mescaline.

Unfortunately, according to ACS, “serotonin can be a double-edged sword: Earlier this year, W. H. Kaye at the University of California, San Diego, and others implicated elevated levels of serotonin in the brain in eating disorders, such as anorexia and bulimia.

Note:The structure shown here is a space-filling model of the serotonin molecule, C10H12N2O from the Wikimedia Commons. “It is based on that found in the salt serotonin hydrogen oxalate, determined by X-ray crystallography in Acta Chem. Scand. (1978) 32a, 267-270”


Crystal of the Week: Pyrite!


In 1848, the first reports of gold (Au) came out of the Sierra Nevada mountains in California. As the news spread to neighboring Oregon and Latin America, eager prospectors flocked to California by the thousands, staking new claims throughout the region. Nearby cities, such as San Francisco, swelled from hundreds of residents to tens of thousands within a handful of years. In total, 300,000 people immigrated to California to find their gold and get rich. Although the gold extracted from California’s mountains totaled to nearly the equivalent of $2 billion today before the rush began to subside, many miners never profited—and some even lost money.

One complicating factor was the abundance of pyrite (FeS2), also known as “fool’s gold,” which leads us to our Crystal of the Week in celebration of 2014 International Year of Crystallography! There is certainly no better week to celebrate a “foolish” element than one that includes April Fools Day, afterall. 

Because of pyrite’s resemblance to gold, miners often encountered difficulty distinguishing between the two. Besides a comparison of density, solutions of strong nitric acid and hydrochloric acid were routinely used to identify the imposter; as a noble metal, gold is not susceptible to corrosion by strong acids, whereas almost all other metals and minerals are. Years later, we still strongly associate pyrite with the legacy that it earned in the Sierra Nevadas. However, today, fool’s gold has found a fantastic, new application, to the surprise of many.

Materials engineers are now experimenting with solar cells composed of fool’s gold. Unlike the highly toxic cadmium and rare, expensive elements (e.g., tellurium and indium) used in more conventional solar cells, or the inherently brittle silicon wafer, pyrite is both an efficient absorber of visible light and more robust to mechanical handling. Additionally, iron and sulfur are some of the most abundant and cost-effective materials on Earth. The fool’s gold is often alloyed with silicon (also abundant and cheap!) to achieve better thermal stability, which increases the survivability of the iron silicon sulfide thin film solar cells during processing.

In addition to a Center for Chemical Innovation that exclusively studies solar fuels, the National Science Foundation has supported many researchers who look at new ways to build upon basic science to find smarter, better ways to harness solar energy. Several of these researchers, in fact, include pyrite in their research, such as Matt Law at the University of California Irvine. (See Los Angeles Times story.) According to an abstract of his NSF-funded research, his team combines material scientists, chemists and mathematicians who hope to overcome two hurdles to this technology: “the difficulty in synthesizing high-quality, phase-pure pyrite and the low photovoltage of pyrite devices.”

While much work remains before bringing such devices to market, this material could rapidly move forward America’s renewable energy industry. With this kind of effort, pyrite is no joke when it comes to potential sustainable energy solutions…not even on April Fools Day.

Photo credit: Didier Descouens, Wikimedia Commons


Researchers discovered that when building citizen science participation, not all social networks are equally effective. Google Hangout outperformed Twitter, Facebook and CosmoQuest in engaging a larger audience for Zooniverse, a framework for a diverse set of citizen science tasks. Read more… 

Caption: The Cartwheel galaxy provides a rainbow of mult-wavelength observations. Credit: NASA/JPL-Caltech


Crystal of the Week: Widmanstätten iron!

In continued celebration of the 2014 International Year of Crystallography, this week we highlight the recently announced potential discovery of “primordial gravitational waves,” based on data collected with the National Science Foundation’s South Pole Telescope. This exciting discovery seems to verify the final prediction of Albert Einstein’s general theory of relativity, documenting the earliest shock waves of the big bang.

Of course, any expert (or amateur!) particle physicist knows that immediately after the big bang, the degree of atomic order necessary for crystalline structures was non-existent in the universe. In fact, research has shown that the universe had to cool for thousands of years before the first electrically neutral atoms could form. Instead, our connection to crystallography this week comes from the location of the South Pole Telescope on Antarctica.

Did you know that Antarctica is the best place on Earth to find meteorites? The National Science Foundation also funds the Antarctic Search for Meteorites (ANSMET) through its Office of Polar Programs. The glaciers and terrain of the Transantarctic Mountains are perfect for capturing and sifting meteorites. Combined with local weather patterns, meteorites caught in the glaciers are concentrated and then exposed by high winds, allowing the ANSMET scientists to recover them.

Meteorites come in a variety of classes—indeed, meteorite taxonomy is its own field of science! Most meteorites that fall to Earth are chondrites (86%), formed by the accretion of dust and mineral grains into asteroids. Achondrite meteorites (8%) are similar to igneous rocks found on Earth, having suffered extensive degrees of internal heating and melting while hurtling through space.

In contrast, iron-based meteorites (only 6%), which are composed of an iron-nickel alloy known as meteoric iron, often yield some of the most beautiful internal crystallinity. Typically, the alloy separates into two phases, kamacite and taenite. Cut, polished, and acid-etched iron meteorites are known for their striking geometric Widmanstätten patterns, which reflect the internal crystal symmetry of the alloy. The lamellar grains in these striking specimens can grow to several centimeters in length, as a result of the excessively long cooling times (thousands of years!) allowed for crystal growth in the parent asteroid body.

Finally, while modern scientists collect iron meteorites to study their composition and origin, ancient civilizations used these forms for something quite different—forging and smelting to manufacture swords! (Photo credit: Liz Boatman, NSF)


An anatomically correct robotic hand, developed by a group of researchers funded through NSF’s Emerging Frontiers in Research and Innovation program, will enhance studies of the human hand’s biomechanics and movement control. The device is expected to contribute to more dexterous robotic devices. Read more… 

Caption: Researchers are studying how the brain controls hand movements with the Anatomically Correct Testbed hand. 

Credit: Ellen Garvens, University of Washington


Want to know how old a fish is? Check its ear bones. The bones, called otoliths, have growth rings just like growth rings in a tree, and many fish add one growth ring to their ear bones every year. During an NSF-sponsored Research Experiences for Undergraduates summer internship, James White wondered if eel ear bones add one growth ring every year. He spent the summer studying eel otoliths at the Department of Natural Resources in Charleston, S.C.

After looking at many eel otoliths, White determined that American eels in South Carolina add one growth ring to their ear bones each year. This is important because researchers can use the ear bones to figure out how long eels are living as well as the location of old and young eels. Read further… 
Here, you see a slice of an eel ear bone.
Credit: James White and Stephen Arnott, Marine Resources Research Institute

To get a better view of the world’s oceans, scientists have developed remotely controlled, autonomous vehicles called Seagliders that can travel deep under the ocean surface. The vehicles permit continuous, high-resolution observations of key elements of the deep ocean’s circulation patterns. An essential event in global ocean circulation is the cascade of cold, dense waters of Arctic origin across the deep ocean ridge system that extends from Greenland to Norway. By sensing the vertical movement of water and recording temperature, salinity, dissolved oxygen and suspended particles, Seagliders can provide portraits of the “waterfalls” that form key components of the ocean’s global overturning circulation, often referred to as the global conveyor belt. Read more … 

Here, you see a Seaglider in action. Image credit: Troy Swanson, University of Washington


Since the 1950s, the number of acrylic paintings acquired by museums has grown almost exponentially. These works of art represent a significant cultural asset both in terms of their sheer monetary value and from the standpoint of their social, economic and cultural importance. However, the buildup of indoor air pollution on the paintings over the years now requires removal to preserve the art.

To address this issue, a collaborative research effort between the University of Delaware and Villanova University developed “green” solvents to clean modern art surfaces. Read more…

Here, you see a researcher cleans an acrylic painting with a microemulsion.

Credit: Anthony Lagalante, Villanova University and Richard Wolbers, University of Delaware


Using radio and infrared telescopes, the scientists studied a giant cloud about 770 light-years from Earth in the constellation Perseus. They used the European Space Agency’s Herschel Space Observatory and NSF’s Green Bank Telescope to make detailed observations of the clump, which has a mass nearly 100 times that of the mass of the Sun.

By studying the motions and temperatures of molecules, primarily ammonia, within substructures of a clump in a gas cloud, astronomers got a first, tantalizing look at a crucial early stage in the formation of a star. The entire clump, the scientists say, may form about 10 new stars.

The observations promise to help scientists understand the early stages of a sequence of events through which a giant cloud of gas and dust collapses into dense cores that, in turn, form new stars.

Here you see an example of the second stage of star formation (not to scale). Credit: Bill Saxton, NRAO/AUI/NSF


Crystal of the Week: Ammonium Nitrate!

An interesting NSF-funded study this week examined trends in various cities and their residents’ quests for perfect lawns. That naturally led those of us involved in celebrating 2014 International Year of Crystallography to think of fertilizer, which naturally led to ammonium nitrate, a perfect crystal of the week….

Have you ever had your shoes, luggage, or hands swabbed by TSA when passing through an airport security checkpoint? The TSA officers are looking for trace residues of compounds used to manufacture explosives. One compound that their explosive trace detection (ETD) systems search for is ammonium nitrate (NH4NO3), a common fertilizing agent. All crops require nitrogen to grow, but even though 78 percent of our atmosphere is gaseous nitrogen (N2), the natural incorporation of nitrogen into the soil in sufficient quantities to supply the rapid growth of dense crop fields is poor. For this reason, farmers use fertilizing agents to supply additional nitrogen and promote crop growth.

Originally, farmers used urea to fertilize their fields. However, even though urea has a higher density of nitrogen than ammonium nitrate, it also tends to break down more quickly once exposed to the open environment of a field. For this reason, many farmers turned to ammonium nitrate as their fertilizer of choice. Ammonium nitrate is a white, crystalline solid at standard pressure and temperature. It’s also relatively stable under normal conditions. But if you expose ammonium nitrate to high temperatures, open flames, or significant mechanical shock (i.e., the detonation of an explosive), then ammonium nitrate decomposes very rapidly and very energetically—that is, the ammonium nitrate explodes.

Remember a catastrophic fertilizer plant explosion in West, Texas in 2013? Unfortunately, that plant had a large stockpile of ammonium nitrate, which was exposed to open flames as a fire spread through the facility. Likewise, the Oklahoma City federal building attack in 1995 was also fueled by detonating barrels of ammonium nitrate, among other compounds.

So, if you use ammonium-based fertilizers in your garden, be careful with their storage! Or better yet, take a cue from organic growers who use plant rotations to infuse nitrogen into their gardens in a more natural manner. One can also till plant waste back into garden beds or mix manure into the soil to supply nitrogen slowly as the organic matter decays.