Argonne National Laboratory

Science Highlights

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Fluorescence resonance energy transfer (FRET)-based toxin sensor components. Gray/purple = ribbon/space-fill diagram of botulinum neurotoxin. Dashed lines show binding locations for labeled antibody fragments sBOT1/QD (quantum dot) donors and BOT2/dye acceptors.  (right) Photoluminescence spectra vs BoNT relay assay sensitivity demonstrating the radiometric sensing.
Ratiometric Sensing of Toxins using Quantum Dots

Botulinum neurotoxin (BoNT) presents a significant hazard under numerous realistic scenarios. BoNT is the most toxic substance known. Current tests for BoNT are slow (2 days), lab-based, and complex. A new scheme enabled by the ratio of two fluorescence bands offers quick, specific quantification by non-specialized personnel such as first responders in the field.

December 4, 2015
Researchers at Argonne’s Center for Nanoscale Materials have confirmed the growth of self-directed graphene nanoribbons on the surface of the semiconducting material germanium by researchers at the University of Wisconsin at Madison. (Click on image to enlarge.)
One Direction: Researchers grow nanocircuitry with semiconducting graphene nanoribbons

Researchers from the University of Wisconsin at Madison are the first to grow self-directed graphene nanoribbons on the surface of the semiconducting material germanium. This allows the semiconducting industry to tailor specific paths for nanocircuitry in their technologies. The findings were confirmed at Argonne’s Center for Nanoscale Materials.

October 13, 2015
A phenomenon called extremely large magnetoresistance occurs in 2-dimensional layers of the metal tungsten ditelluride (WTe2). New findings show the metal is, unexpectedly, electronically 3-dimensional. At left, an electron (green) in WTe2 travels a long distance between two scattering events (yellow). In the presence of a magnetic field (center and right) the electron experiences a force that bends its trajectory and increases its resistance. The effect increases as a function of the magnetic field strength B. (from K. Behnia, Viewpoint in Physics, 2015).
Traveling Electrons in Loosely Bound Layers

The metal tungsten ditelluride (WTe2) cleaves easily into atomically thin 2-dimensional layers, but its electrons conduct well in all directions, suggesting a rare case of good charge conduction across weak mechanical bonds.

September 24, 2015
Plasmonic gold nanodisks of ∼100-150 nm fabricated on a 30 nm thick continuous gold film separated by a few nm thick oxide spacer layer. Control of the ultrafast response (probe) depends on spacer thickness and composition, and on excitation wavelength (pump).
Fast Times and Hot Spots in Plasmonic Nanostructures

Light-matter interactions in metallic nanosystems is governed by the collective oscillation of their surface electrons – or plasmons. The ability to control the ultrafast (femtoseconds) response of metal nanostructures was achieved by introducing and tailoring plasmonic hot spots.

August 3, 2015
Using the spin Seebeck effect (SSE), it is possible to create a current of pure spin (a quantum property of electrons related to its magnetic moment) in magnetic insulators. This work demonstrates that the SSE is not limited to magnetic insulators but also occurs in paramagnets.
Spintronics: spin current from a paramagnet

A ferromagnetic material was found to be unnecessary for creating spin current from insulators; this has important implications for the field of spintronics and the development of high-speed, low-power electronics that use electron spin rather than charge to carry information.

July 30, 2015
(top) A membrane of 5.8 nm coated gold nanoparticles folds into a tube under an electron beam; (bottom left) High resolution SEM image of a single tube (bottom right) MD simulation shows two types of membranes with an asymmetric coating of about 0.6 nm. (background) Simulated GISAXS pattern that is used to compare with experiments.
Nanoscale Asymmetry Leads to Janus-like Nanoparticle Membranes

Using grazing incidence small angle x-ray scattering (GISAXS) and surface-enhanced Raman scattering (SERS), very small differences in the distribution of coated-nanoparticle membranes were detected and found to be responsible for their folding into tubular structures. Molecular dynamics simulations show this is related to surface molecular packing density and mobility. Understanding the Janus-like behavior of the man-made membrane opens new design principles to creating 3D artificial superstructures through nanoparticle self-assembly, with opportunities for tuning their electrical, magnetic, and mechanical properties.

June 16, 2015
From left, Ani Sumant, Ali Erdemir, Subramanian Sankaranarayanan, Sanket Deshmukh, and Diana Berman combined diamond, graphene, and carbon to achieve superlubricity.
Slip-sliding away: graphene nanoscrolls enable slick surfaces

Superlubricity, the near absence of friction, is realized at the engineering scale when graphene patches at a diamond-like carbon (DLC)-silica interface wrap around nanodiamonds, creating nanoscroll-like features, and slide against the DLC/SiO2 surfaces. Friction and wear are the primary modes of energy dissipation in moving mechanical assemblies. The nanoscroll system results in reduced contact areas and a significantly reduced coefficient of friction, with a potential savings in energy cost.

May 26, 2015
Illustration of the creation of porous colloidal superparticles (CSPs) of platinum (journal cover image of Advanced Functional Materials, Wiley)
Porous Platinum Superparticles Make Better Catalysts

Colloidal superparticles (CSPs) inherit behavior from their constituent Pt nanocrystals and also have unique collective properties from coupling between their constituents. The CSPs enable full access of reactants to allow 88% conversion in just 35 minutes, vs only 40% in 100 minutes for the nanocrystals alone. The new CSPs also can be efficiently recovered via centrifugation for their re-use. More efficient catalysts can have a tremendous impact on industrial processes and environmental remediation, for example.

May 6, 2015
Schematic of microelectromechanical device consisting of a small oscillating mirror, illustrating the reflection of an incoming X-ray at precise times and at a particular critical angle.
Manipulating X-rays with Tiny Mirrors

Using microelectromechanical system (MEMS) technology, a new class of devices has been made for controlling X-rays. MEMS allow shrinking the optics to the microscale creating ultrafast devices for reflecting X-rays at precise times and specific angles. The successful application of the MEMS technology to manipulate an X-ray beam at very high frequencies will lead to more elaborate X-ray optical schemes for studying the structure and dynamics of matter at atomic length and time scales.

May 6, 2015
Optical interferogram of actuated micromechanical bridges used to manipulate and control the flow of plasmons in a new plasmonic phase modulator. The device can introduce a maximum of 5 rad of phase modulation with low insertion and excess losses.
Nano-mechanical plasmonic phase modulator with potential for electronics

Using standard semiconductor manufacturing equipment, a team from CNM's Nanofabrication & Device Group, NIST, Rutgers University and the University of Colorado at Colorado Springs, has demonstrated a nano-mechanical plasmon phase modulator that can control and manipulate the flow of plasmons at the nanoscale without any degradation in optical performance. The device incorporates nano-mechanical elements to control the speed and wavelength of plasmons and may be a step towards faster computer architectures, as well as enabling other new electronics technologies.

April 3, 2015