Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Engineering team images tiny quasicrystals as they form

18.08.2017

When Israeli scientist Daniel Shechtman first saw a quasicrystal through his microscope in 1982, he reportedly thought to himself, "Eyn chaya kazo" -- Hebrew for, "There can be no such creature."

But there is, and the quasicrystal has become a subject of much research in the 35 years since Shechtman's Nobel Prize-winning discovery. What makes quasicrystals so interesting? Their unusual structure: Atoms in quasicrystals are arranged in an orderly but nonperiodic way, unlike most crystals, which are made up of a three-dimensional, orderly and periodic (repeating) arrangement of atoms.


A transmission electron microscope image of a mesoporous silica nanoparticle, showing the tiling with triangles and squares, and the Fourier analysis (inset) showing 12-fold symmetry.

Credit: Lab of Uli Wiesner, Cornell University

The lab of Uli Wiesner, the Spencer T. Olin Professor of Engineering in the Department of Materials Science and Engineering (MSE) at Cornell University, has joined scientists pursuing this relatively new area of study. And much like Shechtman, who discovered quasicrystals while studying diffraction patterns of aluminum-manganese crystals, Wiesner came upon quasicrystals a bit by accident.

While working with silica nanoparticles -- from which the Wiesner lab's patented Cornell dots (or C dots) are made -- one of his students stumbled upon an unusual non-periodic but ordered silica structure, directed by chemically induced self-assembly of groups of molecules, or micelles.

"For the first time, we see this [quasicrystal] structure in nanoparticles, which had never been seen before to the best of our knowledge," said Wiesner, whose research team proceeded to conduct hundreds of experiments to capture the formation of these structures at early stages of their development.

Their work resulted in a paper, "Formation Pathways of Mesoporous Silica Nanoparticles With Dodecagonal Tiling," published Aug. 15 in Nature Communications. Lead authors are former MSE doctoral student Yao Sun, current postdoc Kai Ma and doctoral student Teresa Kao. Other contributors included Lena Kourkoutis, assistant professor of applied and engineering physics; Veit Elser, professor of physics; and graduate students Katherine Spoth, Hiroaki Sai and Duhan Zhang.

To study the evolution of silica nanoparticle quasicrystals, the best solution would be to take video of the growth process, but that was not possible, Wiesner said.

"The structures are so small, you can only see them through an electron microscope," he said. "Silica degrades under the electron beam, so to look at one particle over a longer period of time is not possible."

The solution? Conduct many experiments, stopping the growth process of the quasicrystals at varying points, imaging with transmission electron microscopy (TEM), and comparing results with computer simulations, conducted by Kao. This imaging, done by Sun and Ma, gave the team a sort of time-lapse look at the quasicrystal growth process, which they could control in a couple of different ways.

One way was to vary the concentration of the chemical compound mesitylene, also known as TMB, a pore expander. The imaging, including cryo-TEM performed by Spoth, showed that as TMB concentration increased, micelles became bigger and more heterogeneous. Adding TMB induced four mesoporous nanoparticle structure changes, starting as a hexagonal and winding up as a dodecagonal (12-sided) quasicrystal.

"The more TMB we add, the broader the pore size distribution," Wiesner said, "and that perturbs the crystal formation and leads to the quasicrystals."

The other way to make these structures evolve is mechanical. Starting with a hexagonal crystal structure, the team found that by simply stirring the solution more and more vigorously, they introduced a disturbance that also changed the micelle size distribution and triggered the same structural changes "all the way to the quasicrystal," Wiesner said.

A lot of the discovery in this work was "serendipity," Wiesner said, the result of "hundreds and hundreds" of growth experiments conducted by the students.

The more insight gained into the early formation of these unique particles, the better his understanding of silica nanoparticles, which are at the heart of his group's work with Cornell dots.

"As the techniques become better, the ability to see small structures and better understand their assembly mechanisms is improving," he said. "And whatever helps us understand these early formation steps will help us to design better materials in the end."

###

The work was supported by grants from the U.S. Department of Energy Office of Science, the National Science Foundation and the Cornell Center for Materials Research, and made use of the Nanobiotechnology Center at Cornell. Additional support came from the Weill Institute and the Kavli Institute at Cornell for Nanoscale Science.

Media Contact

Daryl Lovell
dal296@cornell.edu
607-592-3925

 @cornell

http://pressoffice.cornell.edu 

Daryl Lovell | EurekAlert!

Further reports about: Nanoparticles Silica crystals micelles nanoparticle quasicrystals silica nanoparticles tiny

More articles from Physics and Astronomy:

nachricht NASA's James Webb Space Telescope completes final cryogenic testing
21.11.2017 | NASA/Goddard Space Flight Center

nachricht Previous evidence of water on mars now identified as grainflows
21.11.2017 | US Geological Survey

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Nanoparticles help with malaria diagnosis – new rapid test in development

The WHO reports an estimated 429,000 malaria deaths each year. The disease mostly affects tropical and subtropical regions and in particular the African continent. The Fraunhofer Institute for Silicate Research ISC teamed up with the Fraunhofer Institute for Molecular Biology and Applied Ecology IME and the Institute of Tropical Medicine at the University of Tübingen for a new test method to detect malaria parasites in blood. The idea of the research project “NanoFRET” is to develop a highly sensitive and reliable rapid diagnostic test so that patient treatment can begin as early as possible.

Malaria is caused by parasites transmitted by mosquito bite. The most dangerous form of malaria is malaria tropica. Left untreated, it is fatal in most cases....

Im Focus: A “cosmic snake” reveals the structure of remote galaxies

The formation of stars in distant galaxies is still largely unexplored. For the first time, astron-omers at the University of Geneva have now been able to closely observe a star system six billion light-years away. In doing so, they are confirming earlier simulations made by the University of Zurich. One special effect is made possible by the multiple reflections of images that run through the cosmos like a snake.

Today, astronomers have a pretty accurate idea of how stars were formed in the recent cosmic past. But do these laws also apply to older galaxies? For around a...

Im Focus: Visual intelligence is not the same as IQ

Just because someone is smart and well-motivated doesn't mean he or she can learn the visual skills needed to excel at tasks like matching fingerprints, interpreting medical X-rays, keeping track of aircraft on radar displays or forensic face matching.

That is the implication of a new study which shows for the first time that there is a broad range of differences in people's visual ability and that these...

Im Focus: Novel Nano-CT device creates high-resolution 3D-X-rays of tiny velvet worm legs

Computer Tomography (CT) is a standard procedure in hospitals, but so far, the technology has not been suitable for imaging extremely small objects. In PNAS, a team from the Technical University of Munich (TUM) describes a Nano-CT device that creates three-dimensional x-ray images at resolutions up to 100 nanometers. The first test application: Together with colleagues from the University of Kassel and Helmholtz-Zentrum Geesthacht the researchers analyzed the locomotory system of a velvet worm.

During a CT analysis, the object under investigation is x-rayed and a detector measures the respective amount of radiation absorbed from various angles....

Im Focus: Researchers Develop Data Bus for Quantum Computer

The quantum world is fragile; error correction codes are needed to protect the information stored in a quantum object from the deteriorating effects of noise. Quantum physicists in Innsbruck have developed a protocol to pass quantum information between differently encoded building blocks of a future quantum computer, such as processors and memories. Scientists may use this protocol in the future to build a data bus for quantum computers. The researchers have published their work in the journal Nature Communications.

Future quantum computers will be able to solve problems where conventional computers fail today. We are still far away from any large-scale implementation,...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Ecology Across Borders: International conference brings together 1,500 ecologists

15.11.2017 | Event News

Road into laboratory: Users discuss biaxial fatigue-testing for car and truck wheel

15.11.2017 | Event News

#Berlin5GWeek: The right network for Industry 4.0

30.10.2017 | Event News

 
Latest News

Previous evidence of water on mars now identified as grainflows

21.11.2017 | Physics and Astronomy

NASA's James Webb Space Telescope completes final cryogenic testing

21.11.2017 | Physics and Astronomy

New catalyst controls activation of a carbon-hydrogen bond

21.11.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>