Nanotechnology Now







Heifer International

Wikipedia Affiliate Button


DHgate

Home > Press > Weird science: Crystals melt when they're cooled

Itai Cohen lab
A confocal microscopy image of polystyrene particle clusters beginning to form crystals on a substrate. By changing the aspect ratio in the spacings of the underlying lattice, Savage and colleagues showed that it is possible to direct the growth of crystals to be oriented.
Itai Cohen lab

A confocal microscopy image of polystyrene particle clusters beginning to form crystals on a substrate. By changing the aspect ratio in the spacings of the underlying lattice, Savage and colleagues showed that it is possible to direct the growth of crystals to be oriented.

Abstract:
Growing thin films out of nanoparticles in ordered, crystalline sheets, to make anything from microelectronic components to solar cells, would be a boon for materials researchers, but the physics is tricky because particles of that size don't form crystals the way individual atoms do.

Weird science: Crystals melt when they're cooled

Ithaca, NY | Posted on May 22nd, 2013

Using bigger particles as models, physicists have predicted some unusual properties of nanoparticle crystal growth - in particular, that some particles, due to their sizes and the attractive forces between them, grow crystals that melt when they're cooled.

A study led by John Savage, former postdoctoral associate in the lab of Itai Cohen, associate professor of physics, showed that colloidal crystals, which form out of particles suspended in fluid, can exhibit this odd phenomenon of cold melt. The study was published online May 20 in Proceedings of the National Academy of Sciences.

Usually people grow crystals of different materials, like the common semiconductor gallium arsenide, as layered sheets of strongly bonded atoms. Colloidal crystals are different; they form when colloidal particles suspended in a fluid self-assemble into arrays.

To get the micron-sized colloids to form crystals, the researchers introduced nanometer-sized particles into the fluid, which compete with the larger colloids for space and end up pushing the colloids together, but only when the distance between them is smaller than the nanoparticles. Because this attraction results from the thermal energy of the nanoparticle motions, the bonds between the colloidal particles are also relatively weak.

These short-ranged, weak attractions between particles, as opposed to strong atomic bonds, exhibit some surprising behaviors. For example, Cohen said, in solution the particles are only able to feel each other when they are less than a nanoparticle apart. But if the colloidal particles are resting on a substrate of particles, which sets the spacing between them, then the range of the interaction can increase dramatically.

They found that the substrate particles keep the colloids loosely bound long enough that they can jostle and interact with their in-plane neighbors, but only once in a while. Effectively, it looks like the particles are forming bonds with their in-plane neighbors, even though they are only doing so sometimes.

"This allows in-plane neighbors to form loosely bound crystals whose inter-particle spacing is much larger than what you would expect was possible, given the short-ranged nature of the interaction," Cohen said.

When they lowered the temperature so that the bonds between particles were stronger than their thermal energy, the particles jostled less. Consequently, they sat deeper in the well formed by the substrate particles and interacted with their in-plane neighbors less frequently.

The result, Cohen said, is that the colloids were no longer able to form in-plane bonds that can hold the crystal together, so particles can diffuse away and the crystal dissolves or melts. "It's this weird effect," Cohen said, "where the crystal melts upon cooling."

These results could help materials researchers tailor the growth of crystals composed of nanoparticles - where similar effects arise - for new applications in electronics or energy materials.

The study, "Entropy-driven crystal formation on highly strained substrates," was supported by King Abdullah University of Science and Technology and the National Science Foundation.

####

For more information, please click here

Contacts:
Cornell Chronicle
Anne Ju
607- 255-9735


Media Contact
Syl Kacapyr
607-255-7701

Copyright © Cornell University

If you have a comment, please Contact us.

Issuers of news releases, not 7th Wave, Inc. or Nanotechnology Now, are solely responsible for the accuracy of the content.

Bookmark:
Delicious Digg Newsvine Google Yahoo Reddit Magnoliacom Furl Facebook

Related News Press

News and information

Nanoscale worms provide new route to nano-necklace structures March 29th, 2015

Solving molybdenum disulfide's 'thin' problem: Research team increases material's light emission by twelve times March 29th, 2015

A first glimpse inside a macroscopic quantum state March 28th, 2015

DFG to Establish One Clinical Research Unit and Five Research Units: New Projects to Investigate Complications in Pregnancy, Particle Physics, Nanoparticles, Implants and Transport Planning / Approximately 13 Million Euros in Funding for an Initial Three-Year Period March 28th, 2015

State-of-the-art online system unveiled to pinpoint metrology software accuracy March 27th, 2015

Physics

A first glimpse inside a macroscopic quantum state March 28th, 2015

Using magnetic fields to understand high-temperature superconductivity: Los Alamos explores experimental path to potential 'next theory of superconductivity' March 27th, 2015

Thousands of atoms entangled with a single photon: Result could make atomic clocks more accurate March 26th, 2015

Square ice filling for a graphene sandwich March 26th, 2015

Quantum experiment verifies Einstein's 'spooky action at a distance': Griffith University, University of Tokyo homodyne measurements show what Einstein did not believe to be real: the non-local collapse of a particle's wave function March 25th, 2015

Thin films

LAMDAMAP 2015 hosted by the University March 26th, 2015

Govt.-Legislation/Regulation/Funding/Policy

Nanoscale worms provide new route to nano-necklace structures March 29th, 2015

UT Dallas engineers twist nanofibers to create structures tougher than bulletproof vests March 27th, 2015

Novel nanoparticle therapy promotes wound healing March 27th, 2015

Designer's toolkit for dynamic DNA nanomachines: Arm-waving nanorobot signals new flexibility in DNA origami March 27th, 2015

Discoveries

Nanoscale worms provide new route to nano-necklace structures March 29th, 2015

Solving molybdenum disulfide's 'thin' problem: Research team increases material's light emission by twelve times March 29th, 2015

A first glimpse inside a macroscopic quantum state March 28th, 2015

Designer's toolkit for dynamic DNA nanomachines: Arm-waving nanorobot signals new flexibility in DNA origami March 27th, 2015

Materials/Metamaterials

DFG to Establish One Clinical Research Unit and Five Research Units: New Projects to Investigate Complications in Pregnancy, Particle Physics, Nanoparticles, Implants and Transport Planning / Approximately 13 Million Euros in Funding for an Initial Three-Year Period March 28th, 2015

Chemists make new silicon-based nanomaterials March 27th, 2015

UT Dallas engineers twist nanofibers to create structures tougher than bulletproof vests March 27th, 2015

Using magnetic fields to understand high-temperature superconductivity: Los Alamos explores experimental path to potential 'next theory of superconductivity' March 27th, 2015

Announcements

Nanoscale worms provide new route to nano-necklace structures March 29th, 2015

Solving molybdenum disulfide's 'thin' problem: Research team increases material's light emission by twelve times March 29th, 2015

A first glimpse inside a macroscopic quantum state March 28th, 2015

DFG to Establish One Clinical Research Unit and Five Research Units: New Projects to Investigate Complications in Pregnancy, Particle Physics, Nanoparticles, Implants and Transport Planning / Approximately 13 Million Euros in Funding for an Initial Three-Year Period March 28th, 2015

Research partnerships

SUNY Poly & M+W Make Major Announcement: Major Expansion To Include M+W Owned Gehrlicher Solar America Corporation That Will Create up to 400 Jobs to Develop Solar Power Plants at SUNY Poly Sites Across New York State March 26th, 2015

ORNL-led team demonstrates desalination with nanoporous graphene membrane March 25th, 2015

New kind of 'tandem' solar cell developed: Researchers combine 2 types of photovoltaic material to make a cell that harnesses more sunlight March 24th, 2015

UW scientists build a nanolaser using a single atomic sheet March 24th, 2015

NanoNews-Digest
The latest news from around the world, FREE




  Premium Products
NanoNews-Custom
Only the news you want to read!
 Learn More
NanoTech-Transfer
University Technology Transfer & Patents
 Learn More
NanoStrategies
Full-service, expert consulting
 Learn More










ASP
Nanotechnology Now Featured Books




NNN

The Hunger Project







© Copyright 1999-2015 7th Wave, Inc. All Rights Reserved PRIVACY POLICY :: CONTACT US :: STATS :: SITE MAP :: ADVERTISE