Nanotechnology Now

Our NanoNews Digest Sponsors





Heifer International

Wikipedia Affiliate Button


android tablet pc

Home > Press > Nanothermometer

Abstract:
Tiny gold spheres with a corona of semiconductor nanoparticles show temperature-dependent glow

Nanothermometer

October 25, 2005

Small, smaller, nano - nanoscopic particles that can be arranged into controlled superstructures are the stuff from which future “intelligent” materials with new functions could be made. American researchers at the University of Michigan and Ohio University have now developed a “nanothermometer” based on a system made of two different types of nanoparticle.

The thermometer looks like this: the central components of the superstructure are tiny (20 nm) round gold nanoparticles. The research team headed by Nicholas A. Kotov then attached many tinier spheres (3.7 nm diameter) of the semiconducting material cadmium telluride on the surface of these particles by means of molecular “springs” made of polyethylene glycol chains to form a kind of corona around the gold core. When these nanoparticles are irradiated with laser light, the cadmium telluride is induced to glow. The light transfers its energy to an electron–hole pair in the semiconductor acting as a special oscillator, with the electron being in the conduction band and the hole in the valence band. The electron–hole energy packet is called an exciton. When an electron and a hole are reunited, the energy is released as luminescence and the semiconductor particle glows.

In contrast, as a metal the gold nanoparticle has freely moving conduction electrons that surround the crystal lattice in an “electron cloud.” The presence of an external electromagnetic field, for instance from an exciton, can induce this cloud to vibrate. This vibrational energy packet is called a plasmon. The gold/cadmium telluride nanoparticle system was tuned so that the energies of the corona excitons and the core plasmons are very close.When this is the case, the excitons and plasmons can interact (resonance): the luminescence of the corona is increased significantly. The size of this effect depends on the distance between the coronal particles and the central gold particle, that is, the length of the spring, which is, in turn, temperature-dependent. When heated from 20 to 60 °C, the springs stretch out, the distance between the core and the corona increases, and the glow decreases. If the particles are cooled again, the springs contract, the corona moves closer to the core, and the glow gets brighter. “Our nanoparticle system is an example of a nanoscopic superstructure that changes reversibly in response to an external stimulus, in this case, temperature,” says Kotov. “The coupling with a plasmon–exciton interaction makes this response visible as a very sensitive optical signal - a principle that could form the basis for a new family of sensors and optoelectronic components.”

####


Author: Nicholas A. Kotov, University of Michigan, Ann Arbor (USA),
www.engin.umich.edu/dept/cheme/people/kotov.html

Title: Nanoparticle Assemblies with Molecular Springs: A Nanoscale Thermometer

Angewandte Chemie International Edition, doi: 10.1002/anie.200501264

Contact:
Editorial office:
angewandte@wiley-vch.de

or David Greenberg (US)
dgreenbe@wiley.com

or Julia Lampam (UK)
jlampam@wiley.co.uk

Copyright © Angewandte Chemie

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

Materials/Metamaterials

Guo Lab Shows Potential of RNA as Heat-resistant Polymer Material for Nanoarchitectures April 23rd, 2014

Nanomaterial Outsmarts Ions April 22nd, 2014

Thinnest feasible membrane produced April 17th, 2014

INSCX™ exchange to present Exchange trade reporting mechanism for engineered nanomaterials (NMs) to UK regulation agencies, insurers and upstream/downstream users April 17th, 2014

Announcements

Imec Reports Four Percent Growth for 2013 Fiscal Year End —Continues to Accelerate Innovation Through Global Collaborations and Technological Breakthroughs in Nanoelectronics— April 24th, 2014

Multicapacity Microreactor for Catalyst Characterisation April 24th, 2014

Making graphene work for real-world devices: Fundamental research in phonon scattering helps researchers design graphene materials for applications April 24th, 2014

Return on investment for kit and promotion materials April 24th, 2014

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 1999-2014 7th Wave, Inc. All Rights Reserved PRIVACY POLICY :: CONTACT US :: STATS :: SITE MAP :: ADVERTISE