Understanding secondary light emission by plasmonic nanostructures may improve medical imaging

Jan 13, 2014
This is an illustration of resonant electronic Raman scattering and resonant fluorescence. Credit: Jingyu Huang, University of Illinois

Applications in imaging and sensing typically involve the emission of light at a different wavelength than the excitation, or "secondary light emission." The interpretation of resonant secondary light emission in terms of fundamental processes has been controversial for 40 years. In this work, researchers found that resonant electronic Raman scattering and resonant fluorescence may both be useful descriptions of the secondary emission.

"Plasmonic nanostructures are of great current interest as chemical sensors, in vivo imaging agents, and for photothermal therapeutics," explained David G. Cahill, a Willett Professor and head of the Department of Materials Science and Engineering at the University of Illinois at Urbana-Champaign. "Applications in imaging and sensing typically involve the emission of light at a different wavelength than the excitation, or 'secondary '. The interpretation of resonant secondary light emission in terms of fundamental processes has been controversial for 40 years."

"In this work, we point out that resonant electronic Raman and resonant fluorescence may both be useful descriptions of the secondary emission, Cahill added. "Better understanding of these principles and their limitations can result in improved biological and medical imaging modalities."

Fluorescence is a relatively familiar process by which light of one color or wavelength is absorbed by a material, e.g., an organic dye or a phosphor, and then light is emitted at a different color after a brief interval of time. In Raman scattering, the is shifted to a different color in an instantaneous scattering event. Raman scattering is not common in everyday life but is a critical tool of analytical chemistry.

"Light emission from plasmonic nanostructures at wavelengths shorter than the wavelength of pulsed laser excitation is typically described as the simultaneous absorption of two photons followed by fluorescence, which is used a lot in biological imaging," explained Jingyu Huang, first author of the paper that appears in the Proceedings of the National Academy of Sciences. "However, we found that by modeling the emission as Raman scattering from electron-hole pairs can predict how the light emission depends on laser power, pulse duration, and wavelength.

"Since we understand more of the mechanism of this kind of light mission, we can help to design the biological and medical imaging experiments better, and at the same time we can also have more insight into the broad background of surface-enhanced Raman scattering which is also related to this kind of light emission, Huang added.

Explore further: Amplifying our vision of the infinitely small

More information: "Resonant secondary light emission from plasmonic Au nanostructures at high electron temperatures created by pulsed laser excitation," www.pnas.org/content/early/201… 477111.full.pdf+html

Related Stories

Amplifying our vision of the infinitely small

Dec 02, 2013

Richard Martel and his research team at the Department of Chemistry of the Université de Montréal have discovered a method to improve detection of the infinitely small. Their discovery is presented in the ...

Nanoparticle imaging: A resonant improvement

Oct 28, 2011

Raman spectroscopy is a powerful technique for analyzing atomic structure based on the inelastic scatter of light from molecules, with diverse applications including medical imaging and chemical sensing. Researchers ...

CARS microscopy on its way to clinical translation

Jan 10, 2014

Coherent anti-Stokes Raman scattering microscopy offers noninvasive label-free imaging, high sensitivity, and chemical specificity, which makes it an attractive alternative to histopathology for diagnosis. For clinical translation, ...

Altering organic molecules' interaction with light

Aug 06, 2013

Enhancing and manipulating the light emission of organic molecules is at heart of many important technological and scientific advances, including in the fields of organic light emitting devices, bio-imaging, ...

Recommended for you

PPPL studies plasma's role in synthesizing nanoparticles

20 hours ago

DOE's Princeton Plasma Physics Laboratory (PPPL) has received some $4.3 million of DOE Office of Science funding, over three years, to develop an increased understanding of the role of plasma in the synthesis ...

First ab initio method for characterizing hot carriers

Jul 17, 2014

One of the major road blocks to the design and development of new, more efficient solar cells may have been cleared. Researchers with the Lawrence Berkeley National Laboratory (Berkeley Lab) have developed ...

User comments : 0