(Press-News.org) 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. 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."
INFORMATION:
This research was supported by DOE's Office of Science.
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
Hotspots tamed by BEAST
Secrets of mysterious metal hotspots uncovered by new single molecule imaging technique
2011-01-20
ELSE PRESS RELEASES FROM THIS DATE:
UCSF team views genome as it turns on and off inside cells
2011-01-20
UCSF researchers have developed a new approach to decoding the vast information embedded in an organism's genome, while shedding light on exactly how cells interpret their genetic material to create RNA messages and launch new processes in the cell.
By combining biochemical techniques with new, fast DNA-sequencing technology and advanced computer technology, the team was able to examine with unprecedented resolution how a cell converts DNA into RNA – a molecular cousin of DNA that is used in the process of creating proteins that govern most biological functions. And they ...
The Orion nebula: Still full of surprises
2011-01-20
The Orion Nebula, also known as Messier 42, is one of the most easily recognisable and best-studied celestial objects. It is a huge complex of gas and dust where massive stars are forming and is the closest such region to the Earth. The glowing gas is so bright that it can be seen with the unaided eye and is a fascinating sight through a telescope. Despite its familiarity and closeness there is still much to learn about this stellar nursery. It was only in 2007, for instance, that the nebula was shown to be closer to us than previously thought: 1350 light-years, rather ...
Cancer scientists discover genetic diversity in leukemic propagating cells
2011-01-20
(Toronto, Canada – January 20, 2011) – Cancer scientists led by Dr. John Dick at the Ontario Cancer Institute (OCI) and collaborators at St Jude Children's Research Hospital (Memphis) have found that defective genes and the individual leukemia cells that carry them are organized in a more complex way than previously thought.
The findings, published today in Nature (DOI:10.1038/nature09733), challenge the conventional scientific view that cancer progresses as a linear series of genetic events and that all the cells in a tumour share the same genetic abnormalities and ...
How much sex is enough?
2011-01-20
Society has long debated the contrasting advantages of monogamy and promiscuity and, in western society at least, the long term benefits of monogamy have in general won out. However new research published in BioMed Central's open access journal BMC Evolutionary Biology shows that sperm from polygamous mice are better competitors in the race for fertilisation.
Dr Renée Firman at the Centre for Evolutionary Biology, University of Western Australia, has used house mice to show that sperm from rival males compete to fertilise females and that, over several generations, polygamy ...
Creating simplicity: How music fools the ear
2011-01-20
What makes music beautiful? The best compositions transcend culture and time – but what is the commonality which underscores their appeal? New research published in BioMed Central's open access journal BMC Research Notes suggests that the brain simplifies complex patterns, much in the same way that 'lossless' music compression formats reduce audio files, by removing redundant data and identifying patterns.
There is a long held theory that the subconscious mind can recognise patterns within complex data and that we are hardwired to find simple patterns pleasurable. Dr ...
Quality improvement intervention for ICUs results in increased use of evidence-based care practices
2011-01-20
A multifaceted quality improvement intervention that included education, reminders and feedback through a collaborative telecommunication network improved the adoption of evidenced-based care practices in intensive care units at community hospitals for practices such as preventing catheter-related bloodstream infections and ventilator-associated pneumonia, according to a study that will appear in the January 26 issue of JAMA. The study is being published early online to coincide with its presentation at the annual meeting of the Society of Critical Care Medicine.
Despite ...
Triblock spheres provide a simple path to complex structures
2011-01-20
CHAMPAIGN, Ill. — University of Illinois materials scientists have developed a simple, generalizable technique to fabricate complex structures that assemble themselves.
Their advance, published in the Jan. 20 issue of Nature, utilizes a new class of self-assembling materials that they developed. The team demonstrated that they can produce a large, complex structure – an intricate lattice – from tiny colloidal particles called triblock Janus spheres.
"This is a big step forward in showing how to make non-trivial, non-obvious structures from a very simple thing," said ...
Survey reveals potential innovation gap in the US
2011-01-20
Cambridge, Mass., January 19, 2011 – Invention and innovation are essential to remaining globally competitive, and a new survey shows an untapped group of potential inventors in the U.S. The 2011 Lemelson-MIT Invention Index , announced today, indicates that American women ages 16 – 25 possess many characteristics necessary to become inventors, such as creativity, interest in science and math, desire to develop altruistic inventions, and preference for working in groups or with mentors – yet they still do not see themselves as inventive. Young men in the same age group ...
Parental divorce linked to suicidal thoughts
2011-01-20
TORONTO, ON –Adult children of divorce are more likely to have seriously considered suicide than their peers from intact families, suggests new research from the University of Toronto
In a paper published online this week in the journal Psychiatry Research, investigators examined gender specific differences among a sample of 6,647 adults, of whom 695 had experienced parental divorce before the age of 18. The study found that men from divorced families had more than three times the odds of suicidal ideation in comparison to men whose parents had not divorced. Adult daughters ...
Case Western Reserve and Athersys show regenerative benefit of MultiStem after spinal cord injury
2011-01-20
Case Western Reserve University School of Medicine and Athersys, Inc. (NASDAQ: ATHX) announced a joint scientific study on spinal cord injury will be published today in the January issue of the Journal of Neuroscience. The study, by leading researchers from the Department of Neurosciences at the School of Medicine and scientists at Athersys, presents data supporting the potential therapeutic benefit of Athersys' MultiStem® program for spinal cord injury. Researchers observed that administration of Multipotent Adult Progenitor Cells (MAPC) following spinal cord injury in ...
LAST 30 PRESS RELEASES:
Sensitive ceramics for soft robotics
Trends in hospitalizations and liver transplants associated with alcohol-induced liver disease
Spinal cord stimulation vs medical management for chronic back and leg pain
Engineered receptors help the immune system home in on cancer
How conflicting memories of sex and starvation compete to drive behavior
Scientists discover ‘entirely unanticipated’ role of protein netrin1 in spinal cord development
Novel SOURCE study examining development of early COPD in ages 30 to 55
NRL completes development of robotics capable of servicing satellites, enabling resilience for the U.S. space infrastructure
Clinical trial shows positive results for potential treatment to combat a challenging rare disease
New research shows relationship between heart shape and risk of cardiovascular disease
Increase in crisis coverage, but not the number of crisis news events
New study provides first evidence of African children with severe malaria experiencing partial resistance to world’s most powerful malaria drug
Texting abbreviations makes senders seem insincere, study finds
Living microbes discovered in Earth’s driest desert
Artemisinin partial resistance in Ugandan children with complicated malaria
When is a hole not a hole? Researchers investigate the mystery of 'latent pores'
ETRI, demonstration of 8-photon qubit chip for quantum computation
Remote telemedicine tool found highly accurate in diagnosing melanoma
New roles in infectious process for molecule that inhibits flu
Transforming anion exchange membranes in water electrolysis for green hydrogen production
AI method can spot potential disease faster, better than humans
A development by Graz University of Technology makes concreting more reliable, safer and more economical
Pinpointing hydrogen isotopes in titanium hydride nanofilms
Political abuse on X is a global, widespread, and cross-partisan phenomenon, suggests new study
Reintroduction of resistant frogs facilitates landscape-scale recovery in the presence of a lethal fungal disease
Scientists compile library for evaluating exoplanet water
Updated first aid guidelines enhance care for opioid overdose, bleeding, other emergencies
Revolutionizing biology education: Scientists film ‘giant’ mimivirus in action
Genetic variation enhances cancer drug sensitivity
Protective genetic mutation offers new hope for understanding autism and brain development
[Press-News.org] Hotspots tamed by BEASTSecrets of mysterious metal hotspots uncovered by new single molecule imaging technique