Nanotechnology Now







Heifer International

Wikipedia Affiliate Button


DHgate

Home > Press > Hotspots Tamed by BEAST – Secrets of Mysterious Metal Hotspots Uncovered by New Single Molecule Imaging Technique

Abstract:
The secrets behind the mysterious nano-sized electromagnetic "hotspots" that appear on metal surfaces under a light are finally being revealed with the help of a BEAST.

Hotspots Tamed by BEAST – Secrets of Mysterious Metal Hotspots Uncovered by New Single Molecule Imaging Technique

Berkeley, CA | Posted on January 20th, 2011

Researchers at the U.S. Department of Energy (DOE)'s Lawrence Berkeley National Laboratory (Berkeley Lab) have developed a single molecule imaging technology, dubbed the Brownian Emitter Adsorption Super-resolution Technique (BEAST), that has made it possible for the first time to directly measure the electromagnetic field inside a hotspot. The results hold promise for a number of technologies, including solar energy and chemical sensing.

"With our BEAST method, we were able to map the electromagnetic field profile within a single hotspot as small as 15 nanometers with an accuracy down to 1.2 nanometers, in just a few minutes," says Xiang Zhang, a principal investigator with Berkeley Lab's Materials Sciences Division and the Ernest S. Kuh Endowed Chaired Professor at the University of California (UC), Berkeley. "We discovered that the field is highly localized and, unlike a typical electromagnetic field, does not propagate through space. The field also has an exponential shape that rises steeply to a peak and then decays very fast."

Zhang, who directs the Center for Scalable and Integrated NanoManufacturing (SINAM), a National Science Foundation Nano-scale Science and Engineering Center at UC Berkeley, is the corresponding author of a paper on this research that appears in the journal Nature under the title "Mapping the Distribution of Electromagnetic Field Inside a 15nm Sized Hotspot by Single Molecule Imaging." Co-authoring the paper with Zhang were Hu Cang, Anna Labno, Changgui Lu, Xiaobo Yin, Ming Liu and Christopher Gladden.

Under optical illumination, rough metallic surfaces will become dotted with microscopic hotspots, where the light is strongly confined in areas measuring tens of nanometers in diameter, and the Raman (inelastic) scattering of the light is enhanced by up to 14 orders of magnitude. First observed more than 30 years ago, such hotspots have been linked to the impact of surface roughness on plasmons (electronic surface waves) and other localized electromagnetic modes.

However, during the past three decades, little has been learned about the origins of these hotspots.

"Amazingly, despite thousands of papers on this problem and various theories, we are the first to experimentally determine the nature of the electromagnetic field inside of such a nano-sized hotspots," says Hu Cang, lead author on the Nature paper and a member of Zhang's research group. "The 15 nanometer hotspot we measured is about the size of a protein molecule. We believe there are hotspots that may even be smaller than a molecule."

Because the size of these metallic hotspots is far smaller than the wavelength of incident light, a new technique was needed to map the electromagnetic field within a hotspot. The Berkeley researchers developed the BEAST method to capitalize on the fact that individual fluorescent dye molecules can be localized with single nanometer accuracy. The fluorescence intensity of individual molecules adsorbed on the surface provides a direct measure of the electromagnetic field inside a single hotspot. BEAST utilizes the Brownian motion of single dye molecules in a solution to make the dyes scan the inside of single hotspot stochastically, one molecule at a time.

"The exponential shape we found for the electromagnetic field within a hotspot is direct evidence for the existence of a localized electromagnetic field, as opposed to the more common form of Gaussian distribution," Cang says. "There are several competing mechanisms proposed for hotspots and we are now working to further examine these fundamental mechanisms."

BEAST starts with the submerging of a sample in a solution of freely diffusing fluorescent dye. Since the diffusion of the dye is much faster than the image acquisition time (0.1 milliseconds vs. 50-to-100 milliseconds), the fluorescence produces a homogeneous background. When a dye molecule is adsorbed onto the surface of a hotspot, it appears as a bright spot in images, with the intensity of the spot reporting the local field strength.

"By using a maximum likelihood single molecule localization method, the molecule can be localized with single nanometer accuracy," Zhang says. "After the dye molecule is bleached (typically within hundreds of milliseconds), the fluorescence disappears and the hotspot is ready for the next adsorption event."

Choosing the right concentration of the dye molecules enables the adsorption rate on the surface of a hotspot to be controlled so that only one adsorbed molecule emits photons at a time. Since BEAST uses a camera to record the single molecule adsorption events, multiple hotspots within a field of view of up to one square millimeter can be imaged in parallel.

In their paper, Zhang and his colleagues see hotspots being put to use in a broad range of applications, starting with the making of highly efficient solar cells and devices that can detect weak chemical signals.

"A hotspot is like a lens that can focus light to a small spot with a focusing power well beyond any conventional optics," Cang says. "While a conventional lens can only focus light to a spot about half the wavelength of visible light (about 200-300 nanometers), we now confirm that a hotspot can focus light to a nanometer-sized spot."

Through this exceptional focusing power, hotspots could be used to concentrate sun light on the photocatalytic sites of solar devices, thereby helping to maximize light- harvesting and water-splitting efficiencies. For the detection of weak chemical signals, e.g., from a single molecule, a hotspot could be used to focus incident light so that it only illuminates the molecule of interest, thereby enhancing the signal and minimizing the background.

BEAST also makes it possible to study the behavior of light as it passes through a nanomaterial, a critical factor for the future development of nano-optics and metamaterial devices. Current experimental techniques suffer from limited resolution and are difficult to implement on the truly nanoscale.

"BEAST offers an unprecedented opportunity to measure how a nanomaterial alters the distribution of light, which will guide the development of advanced nano-optics devices," says Cang. "We will also use BEAST to answer some challenging problems in surface science, such as where and what are the active sites in a catalyst, how the energy or charges transfer between molecules and a nanomaterial, and what determine surface hydrophobicity. These problems require a technique with electron-microscopy level resolution and optical spectroscopy information. BEAST is a perfect tool for these problems."

This research was supported by DOE's Office of Science.

For more information about the research of Xiang Zhang visit xlab.me.berkeley.edu/xlabnews.htm

####

About Lawrence Berkeley National Laboratory
Lawrence Berkeley National Laboratory is a U.S. Department of Energy (DOE) national laboratory managed by the University of California for the DOE Office of Science. Berkeley Lab provides solutions to the world’s most urgent scientific challenges including sustainable energy, climate change, human health, and a better understanding of matter and force in the universe. It is a world leader in improving our lives through team science, advanced computing, and innovative technology. Visit our Website at www.lbl.gov

For more information, please click here

Contacts:
Lynn Yarris
(510) 486-5375

Copyright © Lawrence Berkeley National Laboratory

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

News and information

Protein Building Blocks for Nanosystems: Scientists develop method for producing bio-based materials with new properties April 17th, 2015

Oxford Instruments commissions high field outsert magnet system for the National High Magnetic Field Laboratory 32 Tesla magnet program April 17th, 2015

QD Vision Expands Product Line with Two-Millimeter Color LCD Display Optic: Color IQ™ Optic Enables Full-Color Gamut for Ultra-Thin Displays and All-in-One Computers April 16th, 2015

The National Science Foundation names engineering researcher Andrea Alú its Alan T. Waterman awardee for 2015: Alú is a pioneer in the field of metamaterials who has developed "cloaking" technology to make objects invisible to sensors April 16th, 2015

Videos/Movies

Light in a spin: Researchers demonstrate angular accelerating light April 15th, 2015

Deben reports on the research of Dr Sunita Ho from UCSF using a CCT500 tensile stage to study the behaviour of dental materials April 14th, 2015

Promising future of quantum dots explored in conference: ‘20 Years of Quantum Dots at Los Alamos’ runs April 12-16 April 13th, 2015

A KAIST research team develops a hyper-stretchable elastic-composite energy harvester April 13th, 2015

Govt.-Legislation/Regulation/Funding/Policy

Oxford Instruments commissions high field outsert magnet system for the National High Magnetic Field Laboratory 32 Tesla magnet program April 17th, 2015

The National Science Foundation names engineering researcher Andrea Alú its Alan T. Waterman awardee for 2015: Alú is a pioneer in the field of metamaterials who has developed "cloaking" technology to make objects invisible to sensors April 16th, 2015

Long Island Capital Alliance Announces Participants for Brookhaven National Laboratory Technology Transfer Capital Forum on May 8: Keynote Speaker Dr. Doon Gibbs, Director of Brookhaven National Laboratory April 16th, 2015

Major advance in artificial photosynthesis poses win/win for the environment: Berkeley Lab researchers perform solar-powered green chemistry with captured CO2 April 16th, 2015

Possible Futures

A glass fiber that brings light to a standstill: By coupling photons to atoms, light in a glass fiber can be slowed down to the speed of an express train; for a short while it can even be brought to a complete stop April 9th, 2015

Nanotechnology in Medical Devices Market is expected to reach $8.5 Billion by 2019 March 25th, 2015

Nanotechnology Enabled Drug Delivery to Influence Future Diagnosis and Treatments of Diseases March 21st, 2015

Nanocomposites Market Growth, Industry Outlook To 2020 by Grand View Research, Inc. March 21st, 2015

Academic/Education

JPK reports on the use of the NanoWizard® 3 AFM system at the Hebrew University of Jerusalem April 14th, 2015

UK National Graphene Institute Selects Bruker as Official Partner: World-Leading Graphene Research Facility Purchases Multiple Bruker AFMs April 7th, 2015

SUNY Poly CNSE and Title Sponsor SEFCU Name Capital Region Teams Advancing to the Final Round of the 2015 New York Business Plan Competition March 30th, 2015

LAMDAMAP 2015 hosted by the University March 26th, 2015

Materials/Metamaterials

The National Science Foundation names engineering researcher Andrea Alú its Alan T. Waterman awardee for 2015: Alú is a pioneer in the field of metamaterials who has developed "cloaking" technology to make objects invisible to sensors April 16th, 2015

Cobalt film a clean-fuel find: Rice University discovery is efficient, robust at drawing hydrogen and oxygen from water April 15th, 2015

Combined effort for structural determination April 15th, 2015

Harvesting energy from electromagnetic waves: In the future, clean alternatives such as harvesting energy from electromagnetic waves may help ease the world's energy shortage April 15th, 2015

Announcements

Protein Building Blocks for Nanosystems: Scientists develop method for producing bio-based materials with new properties April 17th, 2015

Oxford Instruments commissions high field outsert magnet system for the National High Magnetic Field Laboratory 32 Tesla magnet program April 17th, 2015

Newly-Developed Nanocatalysts Increase Performance of Fuel Cells April 16th, 2015

Lanthanide-Organic Framework Nanothermometers Prepared by Spray-Drying April 16th, 2015

Tools

Oxford Instruments commissions high field outsert magnet system for the National High Magnetic Field Laboratory 32 Tesla magnet program April 17th, 2015

Lanthanide-Organic Framework Nanothermometers Prepared by Spray-Drying April 16th, 2015

Combined effort for structural determination April 15th, 2015

JPK reports on the use of the NanoWizard® 3 AFM system at the Hebrew University of Jerusalem April 14th, 2015

Photonics/Optics/Lasers

Protein Building Blocks for Nanosystems: Scientists develop method for producing bio-based materials with new properties April 17th, 2015

Light in a spin: Researchers demonstrate angular accelerating light April 15th, 2015

Graphene pushes the speed limit of light-to-electricity conversion: Researchers from ICFO, MIT and UC Riverside have been able to develop a graphene-based photodetector capable of converting absorbed light into an electrical voltage at ultrafast timescales April 14th, 2015

Scientists create invisible objects without metamaterial cloaking April 14th, 2015

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







© Copyright 1999-2015 7th Wave, Inc. All Rights Reserved PRIVACY POLICY :: CONTACT US :: STATS :: SITE MAP :: ADVERTISE