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, email@example.com (505) 845-7078
Neal Singer | Newswise Science News
SF State astronomer searches for signs of life on Wolf 1061 exoplanet
20.01.2017 | San Francisco State University
Molecule flash mob
19.01.2017 | Technische Universität Wien
An important step towards a completely new experimental access to quantum physics has been made at University of Konstanz. The team of scientists headed by...
Yersiniae cause severe intestinal infections. Studies using Yersinia pseudotuberculosis as a model organism aim to elucidate the infection mechanisms of these...
Researchers from the University of Hamburg in Germany, in collaboration with colleagues from the University of Aarhus in Denmark, have synthesized a new superconducting material by growing a few layers of an antiferromagnetic transition-metal chalcogenide on a bismuth-based topological insulator, both being non-superconducting materials.
While superconductivity and magnetism are generally believed to be mutually exclusive, surprisingly, in this new material, superconducting correlations...
Laser-driving of semimetals allows creating novel quasiparticle states within condensed matter systems and switching between different states on ultrafast time scales
Studying properties of fundamental particles in condensed matter systems is a promising approach to quantum field theory. Quasiparticles offer the opportunity...
Among the general public, solar thermal energy is currently associated with dark blue, rectangular collectors on building roofs. Technologies are needed for aesthetically high quality architecture which offer the architect more room for manoeuvre when it comes to low- and plus-energy buildings. With the “ArKol” project, researchers at Fraunhofer ISE together with partners are currently developing two façade collectors for solar thermal energy generation, which permit a high degree of design flexibility: a strip collector for opaque façade sections and a solar thermal blind for transparent sections. The current state of the two developments will be presented at the BAU 2017 trade fair.
As part of the “ArKol – development of architecturally highly integrated façade collectors with heat pipes” project, Fraunhofer ISE together with its partners...
19.01.2017 | Event News
10.01.2017 | Event News
09.01.2017 | Event News
20.01.2017 | Awards Funding
20.01.2017 | Materials Sciences
20.01.2017 | Life Sciences