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The DOE Science News Source is a Newswise initiative to promote research news from the Office of Science of the DOE to the public and news media.
  • 2017-07-28 01:05:47
  • Article ID: 678656

Scientists Watch 'Artificial Atoms' Assemble into Perfect Lattices with Many Uses

A serendipitous discovery lets researchers spy on this self-assembly process for the first time with SLAC's X-ray synchrotron. What they learn will help them fine-tune precision materials for electronics, catalysis and more.

  • Credit: Greg Stewart/SLAC National Accelerator Laboratory

    An illustration shows nanocrystals assembling into ordered ‘superlattices’ – a process that a SLAC/Stanford team was able to observe in real time with X-rays from the Stanford Synchrotron Radiation Lightsource (SSRL). They discovered that this assembly takes just a few seconds when carried out in hot solutions. The results open the door for rapid self-assembly of nanocrystal building blocks into complex structures with applications in optoelectronics, solar cells, catalysis and magnetic materials.

  • Credit: Dawn Harmer/SLAC National Accelerator Laboratory

    A lab in the Stanford Chemical Engineering Department where nanocrystals are grown. Experiments at SLAC’s Stanford Synchrotron Radiation Lightsource (SSRL) were able to observe the simultaneous growth of nanocrystals and superlattices for the first time.

  • Credit: Dawn Harmer/SLAC National Accelerator Laboratory

    Stanford Assistant Professor Matteo Cargnello at a lab in the Stanford Chemical Engineering Department where nanocrystals are grown. Cargnello and Chris Tassone, a staff scientist at SLAC’s Stanford Synchrotron Radiation Lightsource (SSRL), led a team that discovered how superlattices can grow unexpectedly fast – in seconds, rather than hours or days – during routine nanocrystal synthesis.

  • Credit: Dawn Harmer/SLAC National Accelerator Laboratory

    Members of the nanocrystal research team, from left: Assistant Professor Jian Qin, postdoctoral researcher Liheng Wu and Assistant Professor Matteo Cargnello, all of Stanford; SLAC staff scientist Chris Tassone; and Stanford graduate student Joshua Willis.

  • Credit: Liheng Wu/Stanford University

    The experimental set-up at SLAC’s Stanford Synchrotron Radiation Lightsource (SSRL) where scientists used an X-ray beam to observe superlattices forming during the synthesis of nanocrystals for the first time. The vessel where the reactions took place is at bottom center, wrapped in gold heating tape that boosted the temperature inside to more than 230 degrees Celsius.

Menlo Park, Calif. — Some of the world’s tiniest crystals are known as “artificial atoms” because they can organize themselves into structures that look like molecules, including “superlattices” that are potential building blocks for novel materials.

Now scientists from the Department of Energy’s SLAC National Accelerator Laboratory and Stanford University have made the first observation of these nanocrystals rapidly forming superlattices while they are themselves still growing. What they learn will help scientists fine-tune the assembly process and adapt it to make new types of materials for things like magnetic storage, solar cells, optoelectronics and catalysts that speed chemical reactions.

The key to making it work was the serendipitous discovery that superlattices can form superfast – in seconds rather than the usual hours or days – during the routine synthesis of nanocrystals. The scientists used a powerful beam of X-rays at SLAC’s Stanford Synchrotron Radiation Lightsource (SSRL) to observe the growth of nanocrystals and the rapid formation of superlattices in real time. 

A paper describing the research, which was done in collaboration with scientists at the DOE’s Argonne National Laboratory, was published today in Nature.

 “The idea is to see if we can get an independent understanding of how these superlattices grow so we can make them more uniform and control their properties,” said Chris Tassone, a staff scientist at SSRL who led the study with Matteo Cargnello, assistant professor of chemical engineering at Stanford

 Tiny Crystals with Outsized Properties 

Scientists have been making nanocrystals in the lab since the 1980s. Because of their tiny size –they’re billionths of a meter wide and contain just 100 to 10,000 atoms apiece -- they are governed by the laws of quantum mechanics, and this gives them interesting properties that can be changed by varying their size, shape and composition. For instance, spherical nanocrystals known as quantum dots, which are made of semiconducting materials, glow in colors that depend on their size; they are used in biological imaging and most recently in high-definition TV displays.

In the early 1990s, researchers started using nanocrystals to build superlattices, which have the ordered structure of regular crystals, but with small particles in place of individual atoms. These, too, are expected to have unusual properties that are more than the sum of their parts.

But until now, superlattices have been grown slowly at low temperatures, sometimes in a matter of days.

That changed in February 2016, when Stanford postdoctoral researcher Liheng Wu serendipitously discovered that the process can occur much faster than scientists had thought. 

‘Something Weird Is Happening’

He was trying to make nanocrystals of palladium - a silvery metal that’s used to promote chemical reactions in catalytic converters and many industrial processes – by heating a solution containing palladium atoms to more than 230 degrees Celsius. The goal was to understand how these tiny particles form, so their size and other properties could be more easily adjusted. 

The team added small windows to a reaction chamber about the size of a tangerine so they could shine an SSRL X-ray beam through it and watch what was happening in real time.

“It’s kind of like cooking,” Cargnello explained. “The reaction chamber is like a pan. We add a solvent, which is like the frying oil; the main ingredients for the nanocrystals, such as palladium; and condiments, which in this case are surfactant compounds that tune the reaction conditions so you can control the size and composition of the particles. Once you add everything to the pan, you heat it up and fry your stuff.”

Wu and Stanford graduate student Joshua Willis expected to see the characteristic pattern made by X-rays scattering off the tiny particles.They saw a completely different pattern instead.

“So something weird is happening,” they texted their advisor.

The something weird was that the palladium nanocrystals were assembling into superlattices.

A Balance of Forces

At this point, “The challenge was to understand what brings the particles together and attracts them to each other but not too strongly, so they have room to wiggle around and settle into an ordered position,” said Jian Qin, an assistant professor of chemical engineering at Stanford who performed theoretical calculations to better understand the self-assembly process.

Once the nanocrystals form, what seems to be happening is that they acquire a sort of hairy coating of surfactant molecules. The nanocrystals glom together, attracted by weak forces between their cores, and then a finely tuned balance of attractive and repulsive forces between the dangling surfactant molecules holds them in just the right configuration for the superlattice to grow.

To the scientists’ surprise, the individual nanocrystals then kept on growing, along with the superlattices, until all the chemical ingredients in the solution were used up, and this unexpected added growth made the material swell. The researchers said they think this occurs in a wide range of nanocrystal systems, but had never been seen because there was no way to observe it in real time before the team’s experiments at SSRL.

“Once we understood this system, we realized this process may be more general than we initially thought,” Wu said. “We have demonstrated that it’s not only limited to metals, but it can also be extended to semiconducting materials and very likely to a much larger set of materials.”

The team has been doing follow-up experiments to find out more about how the superlattices grow and how they can tweak the size, composition and properties of the finished product.

Ian Salmon McKay, a graduate student in chemical engineering at Stanford, and Benjamin T. Diroll, a postdoctoral researcher at Argonne National Laboratory’s Center for Nanoscale Materials, also contributed to the work. 

SSRL and CNM are DOE Office of Science User Facilities, and the research was funded by the DOE Office of Science and by a Laboratory Directed Research and Development grant from SLAC. 

SLAC is a multi-program laboratory exploring frontier questions in photon science, astrophysics, particle physics and accelerator research. Located in Menlo Park, California, SLAC is operated by Stanford University for the U.S. Department of Energy Office of Science. To learn more, please visit www.slac.stanford.edu.

DOE’s 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 https://www.science.energy.gov.

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Research Center Established to Explore the Least Understood and Strongest Force Behind Visible Matter

Science can explain only a small portion of the matter that makes up the universe, from the earth we walk on to the stars we see at night. Stony Brook University and the U.S. Department of Energy's (DOE) Brookhaven National Laboratory (BNL) have established the Center for Frontiers of Nuclear Science to help scientists better understand the building blocks of visible matter. The new Center will push the frontiers of knowledge about quarks, gluons and their interactions that form protons, neutrons, and ultimately 99.9 percent of the mass of atoms - the bulk of the visible universe.

Cyborg Bacteria Outperform Plants When Turning Sunlight Into Useful Compounds (Video)

Photosynthesis provides energy for the vast majority of life on Earth. But chlorophyll, the green pigment that plants use to harvest sunlight, is relatively inefficient. To enable humans to capture more of the sun's energy than natural photosynthesis can, scientists have taught bacteria to cover themselves in tiny, highly efficient solar panels to produce useful compounds.

Scientists Create 'Diamond Rain' That Forms in the Interior of Icy Giant Planets

In an experiment designed to mimic the conditions deep inside the icy giant planets of our solar system, scientists were able to observe "diamond rain" for the first time as it formed in high-pressure conditions. Extremely high pressure squeezes hydrogen and carbon found in the interior of these planets to form solid diamonds that sink slowly down further into the interior.

Nanotechnology Moves From the Clean Room to the Classroom

The U.S. Department of Energy's Argonne National Laboratory and United Scientific Supplies, Inc. are introducing high school students to nanoscience with a new hands-on product.

Discovered: A Quick and Easy Way to Shut Down Instabilities in Fusion Devices

Article describes use of second neutral beam injector to suppress instabilities on the NSTX-U

Researchers Create Molecular Movie of Virus Preparing to Infect Healthy Cells

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Nanotechnology Gives Green Energy a Green Color

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New 3-D Simulations Show How Galactic Centers Cool Their Jets

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Are Your Tweets Feeling Well?

Study finds opinion and emotion in tweets change when you get sick, a method public health workers could use to track health trends.

"Getting to 80%" on Energy Cutbacks Cannot Occur Unless Behaviors Change

California's plan to cut energy consumption by 80 percent by 2050 cannot be achieved with current proposed policy changes because most solutions focus on changing technologies rather than changing behavior, a new UC Davis study suggests.


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Thesis Prize Winner Explores the Proton's Spectrum

When it comes to laying bare the secrets of the proton, Priyashree Roy's efforts at the Thomas Jefferson National Accelerator Facility have already contributed a whole swath of new information useful to researchers. Now, the thesis she wrote about her work has earned her the 2016 Jefferson Science Associates Thesis Prize.

Kathryn Hastie Wins Spicer Award for Lassa Virus Work at SLAC's X-Ray Synchrotron

Kathryn Hastie, staff scientist at The Scripps Research Institute, has spent the last decade studying how the deadly Lassa virus - which causes up to half a million cases of Lassa fever each year in West Africa - enters human cells via a cell surface receptor.

Southern Research to Play Key Role in Low Cost Carbon Fiber Project

Southern Research's Energy & Environment division (E&E) will participate as a subcontractor to WRI to provide renewable acrylonitrile -- the key raw material needed to produce the highest quality carbon fibers -- produced from biomass-derived second generation sugars.

Newly Upgraded Laser Allows Scientists to Peer Further Into the Extreme Universe at SLAC's LCLS

Scientists at the Department of Energy's SLAC National Accelerator Laboratory recently upgraded a powerful optical laser system used to create shockwaves that generate high-pressure conditions like those found within planetary interiors. The laser system now delivers three times more energy for experiments with SLAC's ultrabright X-ray laser, providing a more powerful tool for probing extreme states of matter in our universe.

Three Brookhaven Lab Scientists Selected to Receive Early Career Research Program Funding

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Upcoming 232nd ECS Meeting to Feature International Energy Summit, Nobel Laureate Lecture

The 232nd ECS Meeting will include 49 topical symposia and over 2,300 technical presentations, including the 7th International Electrochemical Energy Summit, the Society's inaugural OpenCon and Hack Day events, and plenary lecture delivered by former U.S. Secretary of Energy and Nobel Prize Laureate Steven Chu.

PNNL Scientist Jiwen Fan Receives DOE Early Career Research Award

Jiwen Fan of the Department of Energy's Pacific Northwest National Laboratory has been selected to receive a 2017 Early Career Research Program award from the U.S. Department of Energy. Fan will use the award to study severe thunderstorms in the central United States - storms that produce large hail, damaging winds, tornadoes, and torrential rainfall.

Three SLAC Scientists Receive DOE Early Career Research Grants

Three scientists at the Department of Energy's SLAC National Accelerator Laboratory will receive DOE Early Career Research Program grants for research to find evidence of cosmic inflation, understand how plasmas excite particles to high energies and develop a way to accelerate particles in much shorter distances with terahertz radiation.

Four ORNL Researchers Receive DOE Early Career Funding Awards

Four Oak Ridge National Laboratory researchers specializing in nuclear physics, fusion energy, advanced materials and environmental science are among 59 recipients of Department of Energy's Office of Science Early Career Research Program awards.

Missouri S&T Professor Earns Patent for Energy Storage Technology

ceramic engineering professor at Missouri University of Science and Technology has received a federal patent for his latest innovation, a multi-layer ceramic capacitor that could help boost energy storage in applications ranging from pulse power devices to military hardware.


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A New Oxidation State for Plutonium

Plutonium has more verified and accessible oxidation states than any other actinide element, an important insight for energy and security applications.

A Traffic Cop for Molecules

Easily manufactured, rigid membranes with ultra-small pores provides to be ultra-selective in separating chemicals.

Creating a Molecular Super Sponge, From the Ground Up

A new uranium-based metal-organic framework, NU-1301, could aid energy producers and industry.

Physicists Move Closer to Listening in on Sub-Atomic Conversation

Calculations of a subatomic particle called the sigma provide insight into the communication between subatomic particles deep inside the heart of matter.

Meet the Director: Chuck Black

This is a continuing profile series on the directors of the Department of Energy (DOE) Office of Science User Facilities. These scientists lead a variety of research institutions that provide researchers with the most advanced tools of modern science including accelerators, colliders, supercomputers, light sources and neutron sources, as well as facilities for studying the nano world, the environment, and the atmosphere.

Making an Ultra-small Silicon "Chip"

A new polymer, created with a structure inspired by crystalline silicon, may make it easier to build better computers and solar cells.

How to Keep a Vital Diagnostic Isotope in Stock

Researchers succeed in producing larger quantities of a long-lived radioisotope, titanium-44, that generates a needed isotope, scandium-44g, on demand.

When Strontium Is Away, Iridium Comes Out to Play

Developing a highly active and acid-stable catalyst for water splitting could significantly impact solar energy technologies.

On Track Towards a Zika Virus Vaccine

Antibody's molecular structure reveals how it recognizes the Zika virus

Quantum Computing Building Blocks

Scientists invented an approach to creating ordered patterns of nitrogen-vacancy centers in diamonds, a promising approach to storing and computing quantum data.


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