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:4/6/2017)... LONDON , April 6, 2017 ... Control, RFID, ANPR, Document Readers, by End-Use (Transportation & ... Energy Facility, Oil, Gas & Fossil Generation Facility, Nuclear ... Healthcare, Educational, Other) Are you looking for ... Authentication sector? ...
(Date:4/5/2017)... , April 5, 2017 Today HYPR ... that the server component of the HYPR platform is ... providing the end-to-end security architecture that empowers biometric authentication ... HYPR has already secured over 15 million users across ... manufacturers of connected home product suites and physical access ...
(Date:4/4/2017)... NEW YORK , April 4, 2017   ... solutions, today announced that the United States Patent and ... The patent broadly covers the linking of an iris ... the same transaction) and represents the company,s 45 th ... our latest patent is very timely given the multi-modal ...
Breaking Biology News(10 mins):
(Date:4/26/2017)... Pa. , April 26, 2017  Genisphere ... delivery platform, has signed a collaborative and sponsored ... Dr. Silvia Muro . The overall goal ... and pharmacodynamics of various 3DNA designs and formulations ... involve targeting diseases of the vasculature as well ...
(Date:4/25/2017)... CA (PRWEB) , ... April 25, 2017 , ... ... of L3 Healthcare, is pleased to announce the company is now a certified ... The iMedNet software certification enables the company’s clinical research team to build, ...
(Date:4/25/2017)... Gatos, California (PRWEB) , ... April 25, 2017 ... ... business, Analytical Services and Metrology Partners.     , Covalent’s Analytical Services unit ... Most samples can be measured within 24 hours of receipt. There are no ...
(Date:4/24/2017)... 2017  Dante Labs announced today the offer of whole ... $900). While American individuals have been able to access WGS ... access WGS below EUR 1,000. The sequencing includes ... information to make informed decisions about disease monitoring, prevention, nutrition, ... ...
Breaking Biology Technology: