Nanotechnology Now

Our NanoNews Digest Sponsors

Heifer International

Wikipedia Affiliate Button

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

Copper catalyst yields high efficiency CO2-to-fuels conversion: Berkeley Lab scientists discover critical role of nanoparticle transformation September 20th, 2017

New quantum phenomena in graphene superlattices September 18th, 2017

New insights into nanocrystal growth in liquid: Understanding process that creates complex crystals important for energy applications September 14th, 2017

Corrosion in real time: UCSB researchers get a nanoscale glimpse of crevice and pitting corrosion as it happens September 14th, 2017

Announcements

GLOBALFOUNDRIES Delivers 8SW RF SOI Technology for Next-Generation Mobile and 5G Applications: Advanced 8SW 300mm SOI technology enables cost-effective, high-performance RF front-end modules for 4G LTE mobile and sub-6GHz 5G applications September 20th, 2017

GLOBALFOUNDRIES Unveils Vision and Roadmap for Next-Generation 5G Applications: Technology platforms are uniquely positioned to enable a new era of ‘connected intelligence’ with the transition to 5G September 20th, 2017

GLOBALFOUNDRIES Delivers Custom 14nm FinFET Technology for IBM Systems: Jointly developed 14HP process is world’s only technology that leverages both FinFET and SOI September 20th, 2017

GLOBALFOUNDRIES Introduces New 12nm FinFET Technology for High-Performance Applications September 20th, 2017

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