News & Highlights

 

Nanowire Synthesis in Motion – New Flow-based Solution-Liquid-Solid Technique

Scientific Achievement
A new technique for solution-phase nanowires synthesis was developed called “flow” solution-liquid-solid growth or flow-SLS. The versatile microfluidics-based approach affords unprecedented  control over the parameters that govern catalyzed semiconductor nanowire nucleation and growth in a liquid environment.

Significance and Impact
Flow-SLS combines the solution-processibility of flask-synthesized nanowires with a capacity for dynamic control over the introduction of reactants and removal of by-products that heretofore was limited to gas-phase methods. By transforming SLS into a continuous technique, we have established a versatile  platform for conducting mechanistic studies and growing novel nanowire heterostructures.

Research Details

  • It was revealed for the first time that a combined-growth model—Gibbs–Thomson and diffusion-limited growth—governs SLS nanowire synthesis.
  • Reaction parameters were tuned to influence supersaturation and shift the minimum diameter that supports nanowire growth to smaller or larger sizes; in this way ultra-small sub-10 nm wires were accessed.
  • Reactant introduction/removal was dynamically controlled to synthesize CdSe/ZnSe superlattice nanowires of unprecedented complexity.
SLS Flow technique

 

 

 

 

 

 

Reference: R. Laocharoensuk, K. Palaniappan, N. A. Smith, R. M. Dickerson, D. J. Werder, J. K. Baldwin and J. A. Hollingsworth, Nature Nanotechnology 2013 8, 660-666.

Contact: Jennifer Hollingsworth

 

Strong coupling in the sub-wavelength limit using metamaterial nanocavities

Scientific Achievement - We demonstrate that the strong light-matter coupling between a metamaterial and an intersubband transition in semiconductor heterostructures is fully scalable from the mid-infrared (~10 microns) to the near-infrared (~1.5 microns) and happens on a single nanocavity level in deep sub-wavelength volumes.

Significance - Plasmonic metamaterials offer the possibility to control light in all three dimensions. Here, we experimentally demonstrate strong light-matter coupling between a single nanocavity and intersubband transitions in heterostructures. Such systems show great potential for the realization of electrically tunable optical filters and modulators at any given wavelength or for studying unusual effects such as superradiance.

Research Details

  • The structure consists of  metallic nanocavities fabricated using a combination of electron-beam lithography and metal evaporation. Typical feature sizes are approximately 100 nm for mid-infrared and 30 nm for near-infrared samples.  
  • Transmission spectra were measured  at CINT using a Fourier-transform infrared spectrometer. Numerical calculations were performed for a periodic array of “dogbone” nanocavities supporting strong field enhancement in their vicinity without the need of an additional ground plane.
metamaterials (left) Schematic of a “dogbone” metamaterial nanocavity strongly coupled to optical dipoles (indicated by the vertical arrows). (right) Scanning electron micrograph image of a fabricated nanocavity with a resonance frequency of 22 THz.

 

metamaterials

 

 

(top left) Calculated mode profile for a single dogbone nanocavity with an effective interaction volume of 4.9´10-4 (l/n)3. (bottom left, right) Experimental polariton splitting demonstrated in the mid-infrared (~10 mm) and in the near-infrared (~1.5 mm ) spectral range.

 

 

 

Reference: A. Benz, S. Campione, S. Liu, I. Montano, J.F. Klem, A. Allerman, J.R. Wendt, M.B. Sinclair, F. Capolino, and I. Brener, Nature Communications 4, 2882 (2013)

Contact: Igal Brener

 

 

Metamaterial flexible sheets could transform optics

Grady, Chen, and Heyes

New ultrathin, planar, lightweight, and broadband polarimetric photonic devices and optics could result from recent research by CINT Scientist Hou-Tong Chen and his team. The advances would boost security screening systems, infrared thermal cameras, energy harvesting, and radar systems. (Members of the metamaterials team, from left: Nathaniel K. Grady, Hou-Tong Chen, Jane E. Heyes)

This development is a key step toward replacing bulky conventional optics with flexible sheets that are about the thickness of a human hair and weighing a fraction of an ounce. The advance is in the design of artificially created materials, called metamaterials, that give scientists new levels of control over light wavelengths.

The research was reported online in Science magazine, “Terahertz Metamaterials for Linear Polarization Conversion and Anomalous Refraction.” The team demonstrated broadband, high-performance linear polarization conversion using ultrathin planar metamaterials, enabling possible applications in the terahertz (THz) frequency regime. Their design can be scaled to other frequency ranges from the microwave through infrared.

metamaterials

(a) Photograph of an ultrathin (72 µm thick) metamaterial sample.

(b) Illustration of how the metamaterial redirects an electromagnetic wave, which would not happen for a normal thin film. The structure is not drawn to scale.

 

Reference: ‘Terahertz Metamaterials for Linear Polarization Conversion and Anomalous Refraction,” Science, published online in Science Express, May 16, DOI: 10.1126/science.1235399, by Nathaniel K. Grady, Jane E. Heyes, Dibakar Roy Chowdhury, Yong Zeng, Matthew T. Reiten, Abul K. Azad, Antoinette J. Taylor, Diego A. R. Dalvit and Hou-Tong Chen of Los Alamos National Laboratory.

Contact: Hou-Tong Chen

 

First Infrared Quantum Dots to Stop Blinking

non-blinking

Non-blinking excitonic emission from near-infrared (NIR) and type-II nanocrystal quantum dots (NQDs) is reported for the first time, coupled with suppressed Auger recombination (AR). To realize this unusual degree of stability at the single-dot level, novel InP/CdS core/shell NQDs were synthesized for a range of shell thicknesses (~1-11 monolayers of CdS).

Significance: This new system demonstrates that electronic structure and shell thickness can be employed together to effect control over key single-dot and ensemble NQD photophysical properties. Suppressed-blinking, NIR emitting NQDs are ideal candidates molecular probes for single-particle tracking; suppressed AR has important implications for optical amplification and lasing.

Research Details:
•Ensemble spectroscopy measurements (photoluminescence peak position and radiative lifetimes) and electronic structure calculations established the transition from type-I to type-II band alignment.
•Single-NQD studies revealed clear evidence for blinking suppression that was not strongly shell-thickness dependent, while photobleaching and biexciton lifetimes trended explicitly with extent of shelling.
•Specifically, very long biexciton lifetimes-up to 7 ns-were obtained for the thickest-shell structures, indicating dramatic suppression of AR.

Full article:A.M. Dennis, B.D. Mangum, A. Piryatinski, Y.-S. Park, D.C. Hannah, J.L. Casson, D.J. Williams, R.D. Schaller, H. Htoon, J.A. Hollingsworth, Nano Lett. 12, 5545 (2012).

Contact: Jennifer Hollingsworth

 

Extremely High Tunability and Low Loss in Nanoscaffold Ferroelectric Films

nanorod assemblies

We have created a nanoscaffold nanocomposite ferroelectric material containing Ba0.6Sr0.4TiO3 (BSTO) and Sm2O3. Strained vertical nanopillar heteroepitaxial films of (Ba0.6Sr0.4TiO3)1-x(Sm2O3)x show remarkably improved tunability values at the same time a reduced dielectric loss. This behavior is opposite to what has been demonstrated in any previous report.

Significance: This new kind of nanostructure and composition holds great promise for electrically tunable microwave devices operating at room temperature and above. The vertical strain controlling mechanism represents a new paradigm to design tunable microwave dielectrics.

image2Research Details: CINT’s well controlled pulsed laser deposition system enabled the growth of desired vertically strained nanocomposites (Fig. 1) with desired structural and physical properties (Fig. 2).
Tunability values of 75% (200 kV/cm field) were achieved at room temperature in micrometer thick films, the value remaining to >50% at 160 °C. Low dielectric loss values of <0.01 were also achieved, significantly lower than reference pure BST films.

 

Full article: L. O. Lee, S. A. Harrington, A. Kursumovic, E. Defay, H. Wang, Z. Bi, C.-F. Tsai, L. Yan, Q. X. Jia, and J. L. MacManus-Driscoll, Nano Lett. 12, 4311 (2012).

Contact: Quanxi Jia

 

 

Zois Award given to CINT User Janez Bonca.

Congratulations to Janez Bonca, who was given the Zois Award for 2012, the highest Slovene award for science . Only one such award is given each year for lifetime achievements to researchers who have most excelled in their scientific, research and development work, and outstanding achievements in scientific, research and development activities.

New CINT Distinguished Affiliate Scientist: C. Barry Carter

Barry CarterWe are pleased to welcome Professor C. Barry Carter (University of Connecticut) as a Sandia consultant and a CINT Distinguished Affiliate Scientist. Barry is the Editor-in-Chief of the Journal of Materials Science, President of the International Federation of Societies for Microscopy, and former Head of the Department of Chemical, Materials & Biomolecular Engineering at the university. His research is concerned with understanding defects in crystals, interfaces between different and similar materials, how these defects and interfaces impact one another and influence properties, and how these structures and interactions depend on the crystallography and chemistry of the materials. He is an internationally respected expert in transmission electron microscopy and has co-authored two popular textbooks. Barry will be at the CINT Core Facility periodically throughout 2012-2013 to conduct research, engage in collaborations, and assist in identifying candidates to fill the CINT Scientist position (TEM capability) in the NEM Thrust.

 

Ultrafast carrier dynamics and radiative recombination in multiferroic BiFeO3

nanorod assemblies

We report a comprehensive study of ultrafast carrier dynamics
in single crystals of multiferroic BiFeO3. Using degenerate femtosecond optical pump-probe spectroscopy, we find that the
photoexcited electrons relax to the conduction band minimum
through electron-phonon coupling with a ~1 ps time constant
that does not significantly change across the antiferromagnetic
transition. Electrons subsequently leave the conduction band
and primarily decay via radiative recombination on a nanosecond
timescale, as supported by photoluminescence measurements.
We find that despite the coexisting ferroelectric and antiferromagnetic orders in BiFeO3, its intrinsic nature results in carrier relaxation similar to that observed in bulk semiconductors.

Degenerate pump-probe-reflectivity measurements at 3 different photon energies at room temperature. The inset displays the early time dynamics, with two identical vertical bars that represent the maximum difference between the signals at the highest and lowest pump photon energies. The signals reach their maximum difference at 3 ps.

Full article published in Appl. Phys. Lett. 100, 242904 (2012)

Contact: Rohit Prasankumar

 

 

LANL Fellows Prizes at CINT

CINT Scientist Steve Doorn and CINT Distinguished Affiliate Amit Misra have recently been recognized for their scientific contriubutions at LANL. .

Steve was awarded the 2011 Fellows Prize for Research. Here is a snippet from the press release:
Stephen Doorn is an intellectual leader in carbon nanotube spectroscopy and is best known in the nanotube community for his groundbreaking advances in Raman spectroscopy of nanotubes, with many examples of “first-ever” types of experiments. He has distinguished himself with numerous scientific accomplishments in the area of spectroscopic studies of carbon nanomaterials, particularly single-walled carbon nanotubes.

And Amit was selected as a 2011 LANL Laboratory Fellow. Fellows are honored for their sustained high-level achievements in programs of importance to the Lab. Amit Misra has had a tremendous impact on the field of structural materials. He has pioneered the development of metal nanostructured multilayers for a range of structural applications, and he has defined this class of materials as a critical platform for understanding the underlying principles that drive new discoveries. His work on plastic flow stability provided theinsight into the development of damage-tolerant nanocomposites that is being explored in the Energy Frontier Research Center at Materials and Irradiation Extremes, for which he now serves as director. For more information, please see the press release.

Congratulations, Steve and Amit!

 

CINT User Science featured in Nature Nanotechnology

Los Alamos scientists detect and track single molecules with nanoscale carbon cylinders

carbon nanotubes

The electronic properties of single-walled carbon nanotubes can be altered by surface adsorption of electronic impurities or dopants. However, fully understanding the influence of these impurities is difficult because of the inherent complexity of the solution-based colloidal chemistry of nanotubes, and because of a lack of techniques for directly imaging dynamic processes involving these impurities. Here, CINT Users Jared Crochet and Juan Duque, along with CINT Scientists Jim Werner and Steve Doorn show that photoluminescence microscopy can be used to image exciton quenching in semiconducting single-walled carbon nanotubes during the early stages of chemical doping with two different species. The addition of AuCl3 leads to localized exciton-quenching sites, which are attributed to a mid-gap electronic impurity level, and the adsorbed species are also found sometimes to be mobile on the surface of the nanotubes. The addition of H2O2 leads to delocalized exciton-quenching hole states, which are responsible for long-range photoluminescence blinking, and are also mobile.

See the LANL Press Release.


Artist's concept of nanotubes on the liquid surface. Image from Los Alamos National Laboratory

 

"Unraveling the Mystery of Quantum Dot Blinking by Single Dot Spectroelectrochemistry" featured in Nature.

Blinking (fluorescence intermittency) of colloidal nanocrystal quantum dots (NQDs) has been a key road block in their utilization in a number of practical applications ranging from bio-medical imaging and singl-particle tracking to solid-state lighting. CINT scientist Han Htoon in collaboration with Christophe Galland, Milan Sykora and Victor I. Klimov of Chemistry Division, have recently developed a novel single-NQD spectroelectrochemistry approach to shine new light onto this intriguing phenomena. To make this approach work, the team collaborated with CINT Scientist Jennifer Hollingsworth who recently developed a new class of ultra-stable core/shell NQDs.

carbon nanotubes

 

The dual goals: to develop novel non-blinking quantum dots as molecular probes and to understand the underlying mechanism of blinking by correlating charging events with blinking events, have been at the center of a National Institutes of Health funded project established in 2008 by Jennifer Hollingsworth (PI), Han Htoon, and Milan Sykora. The work goes a long way toward realizing key aims of this effort and, thereby, application of robust, non-blinking quantum dots for advanced bioimaging concepts.

 

 

CINT User Recognized for Work in Cancer Detection

CINT User, Ed Flynn, was featured in numerous articles in October 2011 for his work in cancer detection. He was recently recognized by the American Physics Society Journal and featured in articles in the Wall Street Journal and APS News. Congratulations, Ed!

 

2011 R&D 100 awarded to CINT team

NanoCluster Beacons

NanoCluster Beacons are collections of silver atoms maneuvered to illuminate when bound to specific nucleic acids, such as the DNA of particular pathogens. Created by Hsin-Chih (Tim) Yeh, James Werner, Jaswinder Sharma, and Jennifer Martinez, these beacons can be used to probe for diseases that threaten humans by identifying the nucleic acid targets that represent a person's full genome, and allow for personalized medication. They also can be used in quantitative biology applications, such as counting individual molecules inside a cell.

Once bound with a specific target, a NanoCluster Beacon lights up, emitting fluorescence approximately 200 times greater than in the unbound state and easily viewed by the naked eye under ultraviolet light. The beacons come in an array of colors for multiplexed analyses, are more photostable than beacons used today, and can be turned on and off reversibly. Inexpensive, easy to use, and reversible, NanoCluster Beacons are superior molecular probes for detecting specific targets, human oncogene (cancer) sequences, and molecular disease sequences (such as sickle cell anemia).


R&D 100 Award-winning NanoCluster Beacons are easily seen with the naked eye under ultraviolet (UV) light.

 

 

 

 

 

 

CINT Distinguished Affiliate Scientist named 2011 MRS Fellow

Michael Nastasi, a Distinguished Affiliate Scientist, and former CINT Scientist, has been selected as a 2011 Materials Research Society (MRS) Fellow. The Fellows are outstanding MRS members whose sustained and distinguished contributions to the advancement of materials research are internationally recognized. Each year, no more than 0.2 percent of the current membership of the Society is elected to the status of Fellow.

Nastasi's award citation reads, “For seminal contributions to the field of ion-solid interactions and radiation effects, including synthesis of novel materials using energetic ions, with applications to energy, manufacturing, nanotechnology, and advanced microelectronics.” 

Nastasi was formally recognized during the 2011 MRS Spring Meeting in San Francisco.

 

 

 

 

Science Highlight:
Insight from a Single Nanowire Electrode

Video story on the news.

Improvements in Li-ion battery technologies require breakthroughs in materials and electrochemistry

  • World's smallest battery inside a transmission electron microscope (TEM), enabling real time observations of electrochemistry process at atomistic length scales
  • A unique open cell battery using ionic liquid electrolyte in the high vacuum of a TEM
  • New insight into electrochemical processes critical to developing new high performance batteries
    • Nanowires can sustain large stress (>10 GPa) without breaking, good candidate for battery
    • Elongation of nanowires during charging may lead to short circuit, thus failure of battery, a key factor to consider during design

JianYu Huang, et al, Science Dec 10, 2010
Please see the Sandia National Laboratory press release.

 

 

CINT Scientist appointed to Editorial Board of MRS Bulletin

CINT Scientist Amit Misra was recently appointed a permanent member of the Editorial Board of MRS Bulletin. He served as a 2009 Volume Organizer and a Guest Editor for the December 2010 theme issue for MRS Bulletin. MRS Bulletin (2009 impact factor = 6.33) is one of the most widely recognized and highly respected publications in advanced materials research. Published monthly by the Materials Research Society (MRS), it features technical theme topics that capture a snapshot of the state-of-the-art of material research. Written by leading experts, the overview articles are useful references for specialists but are also presented at a level understandable to a broad scientific audience.


 

CINT Science on PRL cover

Spherical nanoparticles (NPs), uniformly coated with a simple polymer used to passivate NPs in solution, are shown to produce highly asymmetric coating arrangements. We show that a class of spherical particles is not symmetrically coated even when extremely uniform grafting arrangements and full coverages are employed. We demonstrate, using explicit-atom molecular dynamics simulations of model NPs, that geometric properties dictate when a coating’s spherical symmetry will be unstable and show that the chain end group and the solvent play a secondary role in determining the properties of surface patterns. At the water-vapor interface the coatings are significantly distorted and oriented by the surface. These asymmetric and oriented coatings are expected to have a dramatic effect on the interactions between NPs and will likely influence the structures of aggregated NPs which self-assemble in the bulk and at surfaces. Full article.

J. Matthew D. Lane and Gary S. Grest

 

 

CINT researchers use NanoCluster Beacon to detect specific nucleic acid target sequences for diagnostics

Hsin-Chih (Tim) Yeh, Jaswinder Sharma, Jason Han, Jennifer Martinez, and James Werner of the Center for Integrated Nanotechnologies (MPA-CINT) recently demonstrated that DNA-templated silver nanoclusters (DNA/Ag NCs) can be used to detect specific nucleic acid targets. The nanoclusters circumvent many of the shortcomings of conventional molecular beacons. The team has developed a novel way to control conversions of DNA-templated silver nanoclusters (DNA/Ag NCs) between highly fluorescent and weakly fluoresc ent states. More information (pdf).

 

 

Quanxi Jia named 2010 American Ceramic Society Fellow

The American Ceramic Society (ACerS) recently announced the names of the organization's two newest Distinguished Life Members and 19 members elevated to Fellow status. The title of "Fellow" is an honor ACerS gives to distinguished mid-career scientists, engineers and business leaders who specialize in ceramic and glass materials. Quanxi Jia, among the 19 newly named Fellows, is a Fellow of Los Alamos National Laboratory and a Thrust Leader at CINT.

Dr. Jia received his B.S. and M.S. in Electrical Engineering from Xian Jiaotong University, China, in 1982 and 1985 respectively, and his PhD in the same field from the State University of New York, Buffalo in 1991. He was a team leader at the Superconductivity Technology Center of LANL before joining CINT at the beginning of 2010. Dr. Jia has authored/co-authored over 350 refereed journal articles and 8 book chapters. He has 32 US patents awarded in electronic materials and devices. Among the numerous awards and honors he has received are two prestigious R&D 100 awards, the 2005 Asian-American Engineer of the Year Award, and the Federal Laboratory Consortium for Technology Transfer Awards for Excellence in Technology Transfer. He is a Fellow of Los Alamos National Laboratory and a Fellow of the American Physical Society. His current research interests include nanostructured materials, multifunctional materials, thin films, multilayer systems, and the development of novel solid-state microelectronic/electro-optic devices.

More information on the 2010 ACerS Fellows can be found at http://ceramics.org/awards.


CINT Postdoc Receives Prestigious Fellowship

Shadi Dayeh, a Director's Postdoctoral Fellow in the Center for Integrated Nanotechnologies, has been appointed a Distinguished J. Robert Oppenheimer Postdoctoral Fellow at Los Alamos National Laboratory.  Named after the Laboratory's first Director, this prestigious 3 year fellowship provides the opportunity for recipients to collaborate with LANL scientists and engineers on staff initiated research. Candidates must display extraordinary ability in scientific research and show clear and definite promise of becoming outstanding leaders in the research they pursue. As an Oppenheimer Fellow Shadi plans to pursue semiconductor nanowire studies in a wide variety of areas, including understanding and controlling the science of their growth and their applications in electronics, spintronics, solar energy harvesting and neural probe research. Shadi joined LANL in September, 2008 as a Director's Postdoctoral Fellow; his CINT mentor is Tom Picraux.

 

CINT User, Ed Flynn, featured in New Mexico Business Weekly

CINT User, Dr. Edward Flynn, was recently featured in New Mexico Business Weekly for his ground-breaking technology that can detect certain cancers much earlier than current diagnostic techniques. To view this article, click here.

 

Two CINT Scientists recognized for outstanding scientific contributions

CINT Scientists Toni Taylor and Tom Picraux, were two of the six designated 2009 Los Alamos National Laboratory Fellows recognized for sustained, outstanding scientific contributions and exceptional promise for continued professional achievement.

The title of Fellow is bestowed on only about 2 percent of the Laboratory's current technical staff. The new Fellows come from myriad scientific disciplines and have sustained high-level achievement important to the Laboratory, become recognized authorities in their fields, and made important discoveries used or cited by peers inside and outside the Laboratory.

"These distinguished scientists were chosen as 2009 Laboratory Fellows based on a very rigorous peer review process and honored for their considerable scientific accomplishments," said Terry Wallace, principal associate director for Science, Technology, and Engineering. "I am pleased to have such a distinguished class of Fellows for 2009 that reflects the diversity of top-notch scientific talent at Los Alamos National Laboratory."

Fellows play a continuing role in helping maintain the scientific excellence of the Laboratory. Fellows are often asked by the Laboratory director to assess issues and provide advice. As recognized leaders, Fellows are advocates for the continuing conduct of science at the Laboratory.

Toni Taylor leads the Laboratory's Materials Physics and Applications Division and is a pioneer in electromagnetic metamaterials as well as terahertz science and technology, and in applying coherent control techniques to ultrafast optics, which provide unique insight into condensed-matter physics. Taylor has made key contributions in the exploration of fundamental properties of superconductors through ultrafast techniques; made key demonstrations of exquisite control of phase and amplitude in ultrafast pulses leading to coherent control of propagation in fibers; and has contributed to novel metamaterial concepts leading to devices with unique dielectric properties. She has written or cowritten 250 publications, wrote two book chapters, edited three books,and has mentored 32 postdoctoral researchers. Taylor is a Fellow of the American Physical Society and American Association for the Advancement of Science, and the Optical Society of America.

Samuel "Tom" Picraux is chief scientist of the Laboratory's Center for Integrated Nanotechnologies. Picraux is known internationally for use of energetic ion beams for the characterization of materials, as well as for his advances in surface processing and epitaxy. Using his quantitative ion beam analysis developments, Picraux and his group pioneered the use of surface probes of the plasma edge to diagnose conditions in the U.S. and European tokamak experiments in fusion energy. Picraux and his colleagues pioneered the field of ion implantation metallurgy, creating a standard process for fabrication in the semiconductor industry. A 1990 E.O. Lawrence Award recipient for his developments in ion-challenging and related ion-beam techniques for materials characterization, Picraux has more than 250 publications (6,500 citations). He coauthored one book and edited six others. He is a Fellow of the American Physical Society, American Academy for the Advancement of Science, and the Materials Research Society.