Featured Research

from universities, journals, and other organizations

Nanomaterials: Making a bluer light

Date:
April 12, 2012
Source:
The Agency for Science, Technology and Research (A*STAR)
Summary:
A new design for nanoparticles that absorb low-energy light and emit high-energy light may find use in biological imaging.

Upconverted emission from core-shell nanoparticles can take on different colors, by doping the shells with different activator elements.
Credit: Copyright 2011 NPG

A new design for nanoparticles that absorb low-energy light and emit high-energy light may find use in biological imaging.

Related Articles


The light that a luminescent particle emits is usually less energetic than the light that it absorbs. Some applications require the emitted light to be more energetic, but this so-called upconversion process has been observed in only a small handful of materials. Xiaogang Liu at the A*STAR Institute of Materials Research and Engineering and co-workers have now succeeded in expanding the list of upconversion materials, easing the path to new applications.

Traditional upconversion particles are distinguished by their evenly-spaced or 'ladder-like' energy levels which their internal electrons can take on. The even spacings allow an electron to be promoted up in energy many times consecutively, by absorbing many photons of the same color. When an electron that has been promoted to a high energy finally relaxes back to the lowest-energy state, it emits a photon which is more energetic than the photons that excited it to begin with.

Nanoparticles doped with elements from the lanthanide group of the periodic table are capable of upconversion, and are useful for biological imaging because their high-energy emission can be clearly distinguished from background noise. However, only three elements from the lanthanide series are efficient at upconversion: erbium, thulium, and holmium. This list is so short because of the simultaneous requirements that an upconversion particle exhibit a ladder-like electronic energy structure, and also efficient emission.

Liu and colleagues solved this problem by using different lanthanides to perform different stages of the upconversion process. Sensitizer elements absorb incident light, and transfer the absorbed energy to nearby accumulators, whose electrons rise to high energy levels. Then, the energy stored in accumulators transfers by hopping through many migrators, until an activator is reached. Finally, the activator releases a high-energy photon.

By assigning different elements to each of these four functions, the researchers were able to ease the requirements on any individual element. In addition, unwanted interactions among different elements were avoided by separating them spatially inside a single spherical nanoparticle that has sensitizers and accumulators in the core, activators in the shell and migrators in both the core and the shell.

This design allowed Liu and his team to observe a spectrum of colors from the upconverted emission of europium, terbium, dysprosium and samarium (see image). The same approach may also allow other elements to emit efficiently. "Our results may lead to advances in ultrasensitive biodetection," says Liu, "and should inspire more researchers to work in this field."


Story Source:

The above story is based on materials provided by The Agency for Science, Technology and Research (A*STAR). Note: Materials may be edited for content and length.


Journal Reference:

  1. Feng Wang, Renren Deng, Juan Wang, Qingxiao Wang, Yu Han, Haomiao Zhu, Xueyuan Chen, Xiaogang Liu. Tuning upconversion through energy migration in core–shell nanoparticles. Nature Materials, 2011; 10 (12): 968 DOI: 10.1038/nmat3149

Cite This Page:

The Agency for Science, Technology and Research (A*STAR). "Nanomaterials: Making a bluer light." ScienceDaily. ScienceDaily, 12 April 2012. <www.sciencedaily.com/releases/2012/04/120412105102.htm>.
The Agency for Science, Technology and Research (A*STAR). (2012, April 12). Nanomaterials: Making a bluer light. ScienceDaily. Retrieved November 23, 2014 from www.sciencedaily.com/releases/2012/04/120412105102.htm
The Agency for Science, Technology and Research (A*STAR). "Nanomaterials: Making a bluer light." ScienceDaily. www.sciencedaily.com/releases/2012/04/120412105102.htm (accessed November 23, 2014).

Share This


More From ScienceDaily



More Matter & Energy News

Sunday, November 23, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Toyota's Hydrogen Fuel-Cell Green Car Soon Available in the US

Toyota's Hydrogen Fuel-Cell Green Car Soon Available in the US

AFP (Nov. 21, 2014) Toyota presented its hydrogen fuel-cell compact car called "Mirai" to US consumers at the Los Angeles auto show. The car should go on sale in 2015 for around $60.000. It combines stored hydrogen with oxygen to generate its own power. Duration: 01:18 Video provided by AFP
Powered by NewsLook.com
Google Announces Improvements To Balloon-Borne Wi-Fi Project

Google Announces Improvements To Balloon-Borne Wi-Fi Project

Newsy (Nov. 21, 2014) In a blog post, Google said its balloons have traveled 3 million kilometers since the start of Project Loon. Video provided by Newsy
Powered by NewsLook.com
Raw: Paralyzed Marine Walks With Robotic Braces

Raw: Paralyzed Marine Walks With Robotic Braces

AP (Nov. 21, 2014) Marine Corps officials say a special operations officer left paralyzed by a sniper's bullet in Afghanistan walked using robotic leg braces in a ceremony to award him a Bronze Star. (Nov. 21) Video provided by AP
Powered by NewsLook.com
British 'Bio-Bus' Is Powered By Human Waste

British 'Bio-Bus' Is Powered By Human Waste

Buzz60 (Nov. 21, 2014) British company GENeco debuted what its calling the Bio-Bus, a bus fueled entirely by biomethane gas produced from food scraps and sewage. Jen Markham explains. Video provided by Buzz60
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:

Strange & Offbeat Stories


Space & Time

Matter & Energy

Computers & Math

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins