Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Nanoscopic Particles Resist Full Encapsulation, Simulations Show

14.10.2010
It may seem obvious that dunking relatively spherical objects in a sauce — blueberries in melted chocolate, say — will result in an array of completely encapsulated berries.

Relying on that concept, fabricators of spherical nanoparticles have similarly dunked their wares in protective coatings in the belief such encapsulations would prevent clumping and unwanted chemical interactions with solvents.

Unfortunately, reactions in the nanoworld are not logical extensions of the macroworld, Sandia National Laboratories researchers Matthew Lane and Gary Grest have found.

In a cover article this past summer in Physical Review Letters, the researchers use molecular dynamics simulations to show that simple coatings are incapable of fully covering each spherical nanoparticle in a set.

Instead, because the diameter of a particle may be smaller than the thickness of the coating protecting it, the curvature of the particle surface as it rapidly drops away from its attached coating provokes the formation of a series of louvres rather than a solid protective wall (see illustration).

“We’ve known for some time now that nanoparticles are special, and that ‘small is different,’” Lane said. “What we’ve shown is that this general rule for nanotechnology applies to how we coat particles, too.”

Carlos Gutierrez, manager of Sandia’s Surfaces and Interface Sciences Department, said, “It’s well-known that aggregation of nanoparticles in suspension is presently an obstacle to their commercial and industrial use. The simulations show that even coatings fully and uniformly applied to spherical nanoparticles are significantly distorted at the water-vapor interface.”

Said Grest, “You don’t want aggregation because you want the particles to stay distributed throughout the product to achieve uniformity. If you have particles of, say, micron-size, you have to coat or electrically charge them so the particles don’t stick together. But when particles get small and the coatings become comparable in size to the particles, the shapes they form are asymmetric rather than spherical. Spherical particles keep their distance; asymmetric particles may stick to each other.”

The simulation’s finding isn’t necessarily a bad thing, for this reason: Though each particle is coated asymmetrically, the asymmetry is consistent for any given set. Said another way, all coated nanoscopic sets are asymmetric in their own way.

A predictable, identical variation occurring in every member of a nanoset could open doors to new applications.

“What we’ve done here is to put up a large ‘dead end’ sign to prevent researchers from wasting time going down the wrong path,” Lane said. “Increasing surface density of the coating or its molecular chain length isn’t going to improve patchy coatings, as it would for larger particles. But there are numerous other possible paths to new outcomes when you can control the shape of the aggregation.”

The paper, “Spontaneous Asymmetry of Coated Spherical Nanoparticles in Solution and at Liquid-Vapor Interfaces,” was published on June 9 in Physical Review Letters 104, 235501 (2010).

The computations were carried out at the New Mexico Computing Application Center. The work was supported, in part, by the Center for Integrated Nanotechnologies, a U.S. Department of Energy, Office of Basic Energy Sciences user facility and by the National Institute for NanoEngineering through Laboratory Directed Research and Development program at Sandia National Laboratories.

Sandia National Laboratories is a multiprogram laboratory operated and managed by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy’s National Nuclear Security Administration. With main facilities in Albuquerque, N.M., and Livermore, Calif., Sandia has major R&D responsibilities in national security, energy and environmental technologies, and economic competitiveness.

Sandia news media contact: Neal Singer, nsinger@sandia.gov (505) 845-7078

Neal Singer | Newswise Science News
Further information:
http://www.sandia.gov

More articles from Physics and Astronomy:

nachricht Shape matters when light meets atom
05.12.2016 | Centre for Quantum Technologies at the National University of Singapore

nachricht Climate cycles may explain how running water carved Mars' surface features
02.12.2016 | Penn State

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: Shape matters when light meets atom

Mapping the interaction of a single atom with a single photon may inform design of quantum devices

Have you ever wondered how you see the world? Vision is about photons of light, which are packets of energy, interacting with the atoms or molecules in what...

Im Focus: Novel silicon etching technique crafts 3-D gradient refractive index micro-optics

A multi-institutional research collaboration has created a novel approach for fabricating three-dimensional micro-optics through the shape-defined formation of porous silicon (PSi), with broad impacts in integrated optoelectronics, imaging, and photovoltaics.

Working with colleagues at Stanford and The Dow Chemical Company, researchers at the University of Illinois at Urbana-Champaign fabricated 3-D birefringent...

Im Focus: Quantum Particles Form Droplets

In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.

“Our Quantum droplets are in the gas phase but they still drop like a rock,” explains experimental physicist Francesca Ferlaino when talking about the...

Im Focus: MADMAX: Max Planck Institute for Physics takes up axion research

The Max Planck Institute for Physics (MPP) is opening up a new research field. A workshop from November 21 - 22, 2016 will mark the start of activities for an innovative axion experiment. Axions are still only purely hypothetical particles. Their detection could solve two fundamental problems in particle physics: What dark matter consists of and why it has not yet been possible to directly observe a CP violation for the strong interaction.

The “MADMAX” project is the MPP’s commitment to axion research. Axions are so far only a theoretical prediction and are difficult to detect: on the one hand,...

Im Focus: Molecules change shape when wet

Broadband rotational spectroscopy unravels structural reshaping of isolated molecules in the gas phase to accommodate water

In two recent publications in the Journal of Chemical Physics and in the Journal of Physical Chemistry Letters, researchers around Melanie Schnell from the Max...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

ICTM Conference 2017: Production technology for turbomachine manufacturing of the future

16.11.2016 | Event News

Innovation Day Laser Technology – Laser Additive Manufacturing

01.11.2016 | Event News

#IC2S2: When Social Science meets Computer Science - GESIS will host the IC2S2 conference 2017

14.10.2016 | Event News

 
Latest News

Speed data for the brain’s navigation system

06.12.2016 | Health and Medicine

What happens in the cell nucleus after fertilization

06.12.2016 | Life Sciences

IHP presents the fastest silicon-based transistor in the world

05.12.2016 | Power and Electrical Engineering

VideoLinks
B2B-VideoLinks
More VideoLinks >>>