Navigation Links
Look at Mie!
Date:3/12/2010

HOUSTON (March 12, 2010) Calculations are fine, but seeing is believing. That's the thought behind a new paper by Rice University students who decided to put to the test calculations made more than a century ago.

In 1908, the German physicist Gustav Mie came up with an elegant set of equations to describe the interaction of electromagnetic waves with a spherical metal particle. The theory has been a touchstone ever since for researchers seeking to quantify how nanoscale plasmonic particles scatter radiation.

"The Mie theory is used extensively whenever you deal with nanoparticles and their optical properties," said Alexei Tcherniak, a Rice graduate student and primary author of the new paper in the online edition of Nano Letters this month. "That's the foundation of every calculation."

Tcherniak and Stephan Link, a Rice assistant professor of chemistry and electrical and computer engineering, co-authored the paper with former graduate student Ji Won Ha and current Rice graduate students Liane Slaughter and Sergio Dominguez-Medina.

Better characterization of single nanoparticles is important to researchers pursuing microscopic optical sensors, subwavelength "super lenses," catalysis and photothermal cancer therapies that use nanoparticles.

"Since technology is moving toward single-particle detection, we wanted to see whether Mie's predictions would hold," Tcherniak said. "Average properties fall exactly on the predictions of Mie theory. But we show that individual particles deviate quite a bit." Particles that differ in size can return similar signals because they vary in shape and orientation on the substrate, with which they also interact. Mie's theory, developed for spherical particles in solution long before single-particle spectroscopy, did not consider these factors.

The project began as a sideline in the students' attempt to track single nanoparticles in solution. It became their primary focus when they realized the scope of the task, which involved analyzing five sets of gold particles ranging from 51 to 237 nanometers wide the "biologically relevant" sizes, Tcherniak explained.

Each set of particles was photographed with a scanning electron microscope and then analyzed for its absorption and scattering properties via single-particle photothermal imaging and laser dark-field scattering.

It was tedious, they admitted.

"When you need to find a particle 50 nanometers across on a sample that is 5-by-5 millimeters, you're looking for a needle in a haystack," Tcherniak said. Slaughter and Dominguez-Medina nodded in agreement and recalled a summer of long days required to categorize several hundred particles -- enough "to get all those points on the graph."

They used a couple of strategies to locate particles. One was to put micron-scale grid coordinates on the glass slide containing nanoparticle samples. "That let us know roughly where they were," Tcherniak said.

Another involved applying a bit of astronomy to their microscopy. They found themselves looking for "constellations" in the patterns of specks. "We started saying, 'Oh, that looks like a nose. Do we have a nose anywhere else?'" Slaughter said. "We were so tired; the names might not have been very good."

But their results are.

"Mie theory was around long before anyone knew about nanoparticles, so it's a neat thing to be able to test it," said Link of his students' work. "This is important because they really put together the building blocks that will enable scientists to look at more complex structures. This was not an easy job."


'/>"/>

Contact: Mike Williams
mikewilliams@rice.edu
713-348-6728
Rice University
Source:Eurekalert

Post Your Comments:
*Name:
*Comment:
*Email:
(Date:2/28/2017)... , February 28, 2017 News solutions ... ... Amsterdam from 14 to 16 March, Materna will ... and show how seamless travel is a real benefit for passengers. ... added biometrics to their passenger touch point solutions to take passengers ...
(Date:2/26/2017)... 25, 2017  Securus Technologies, a leading provider ... public safety, investigation, corrections and monitoring, announces the ... "Too often, too many offenders return ... jails are trying to tackle this ongoing problem ... and family members. While significant steps are underway, Securus ...
(Date:2/21/2017)... PORTLAND, Ore. , Feb. 22, 2017  IBM ... Companies (Avamere Health Services, Infinity Rehab, Signature Hospice, Home ... that will apply the power of IBM cognitive computing ... health centers. By analyzing data streaming from sensors in ... physical and environmental conditions, and obtain deeper learnings into ...
Breaking Biology News(10 mins):
(Date:3/24/2017)... Sinovac Biotech Ltd. ("Sinovac" or the "Company") (NASDAQ: SVA), ... , today announced that its board of directors has amended its ... from March 27, 2017 to March 27, 2018. The amendment was not ... Biotech Ltd. ... Sinovac Biotech Ltd. is a China -based ...
(Date:3/23/2017)... ... 23, 2017 , ... AxioMed president, Jake Lubinski, describes the ... when deformed, which is identical to how the human discs work to distribute ... return to its natural state along a hysteresis curve, exactly like a healthy ...
(Date:3/23/2017)... 2017  SeraCare Life Sciences, Inc., a manufacturer ... diagnostics manufacturers and clinical laboratories, is announcing ... Inherited Cancer reference material for ... sequencing (NGS). The Seraseqâ„¢ Inherited Cancer DNA Mix ... industry experts to validate the ability of ...
(Date:3/23/2017)... , March 23, 2017 Kineta, ... development of novel therapies in immuno-oncology, today announced ... lead" small molecule compounds that activate interferon response ... pathways and demonstrate immune-mediated tumor regression in a ... the study who demonstrated complete tumor regression to ...
Breaking Biology Technology: