and measuring a coupling of photons and electrons on the surface of an unusual type of material called a topological insulator.
This type of coupling had been predicted by theorists, but never observed. The researchers suggest that this finding could lead to the creation of materials
Their method involves shooting femtosecond (millionths of a billionth of a second) pulses of mid-infrared light at a sample of material and observing the results with an electron spectrometer, a specialized high-speed camera the team developed.
They demonstrated the existence of a quantum-mechanical mixture of electrons and photons, known as a Floquet-Bloch state, in a crystalline solid.
electrons move in a crystal in a regular, repeating pattern dictated by the periodic structure of the crystal lattice.
Photons are electromagnetic waves that have a distinct, regular frequency; their interaction with matter leads to Floquet states, named after The french mathematician Gaston Floquet. ntanglingelectrons with photons in a coherent manner generates the Floquet-Bloch state,
which is periodic both in time and space. Victor Galitski, a professor of physics at the University of Maryland who was involved not in this research,
The researchers mixed the photons from an intense laser pulse with the exotic surface electrons on a topological insulator.
They also found there were different kinds of mixed states when the polarization of the photons changed.
That actually modifies how electrons move in this system. And when we do this the light does not even get absorbed. g
When the particles encounter thrombin the thrombin cleaves the peptides at a specific location releasing fragments that are excreted then in the animals urine.
Rusgroup, for instance, previously developed a modular robot called the Molecule, which consisted of two cubes connected by an angled bar
The tissue glue works through a system where molecules in the adhesive serve as eysthat interact with ockschemical structures called amines found in abundance in structural tissue known as collagen.
The new findings using a layer of one-atom-thick graphene deposited on top of a similar 2-D layer of a material called hexagonal boron nitride (hbn) are published in the journal Nano Letters.
Although the two materials are structurally similar both composed of hexagonal arrays of atoms that form two-dimensional sheets they each interact with light quite differently.
Light interaction with graphene produces particles called plasmons while light interacting with hbn produces phonons.
he says. t could even enable single-molecule resolution, Fang says, of biomolecules placed on the hybrid material surface.
run a large booth of"Atoms and Molecules"kits. Tan and Vandiver had a lot to be excited about:
the researchers are able to directly observe individual atoms at the interface of two surfaces
By changing the spacing of atoms on one surface, they observed a point at which friction disappears.
Vladan Vuletic, the Lester Wolfe Professor of Physics at MIT, says the ability to tune friction would be helpful in developing nanomachines tiny robots built from components the size of single molecules.
and an ion crystal. The optical lattice was generated using two laser beams traveling in opposite directions,
When atoms travel across such an electric field, they are drawn to places of minimum potential in this case, the troughs.
an ion crystal essentially, a grid of charged atoms in order to study friction effects, atom by atom.
To generate the ion crystal, the group used light to ionize, or charge, neutral ytterbium atoms emerging from a small heated oven,
and then cooled them down with more laser light to just above absolute zero. The charged atoms can then be trapped using voltages applied to nearby metallic surfaces.
Once positively charged, each atom repels each other via the so-called oulomb force. The repulsion effectively keeps the atoms apart,
so that they form a crystal or latticelike surface. The team then used the same forces that are used to trap the atoms to push
and pull the ion crystal across the lattice, as well as to stretch and squeeze the ion crystal,
much like an accordion, altering the spacing between its atoms. An earthquake and a caterpillarin general, the researchers found that
when atoms in the ion crystal were spaced regularly, at intervals that matched the spacing of the optical lattice, the two surfaces experienced maximum friction,
much like two complementary Lego bricks. The team observed that when atoms are spaced so that each occupies a trough in the optical lattice,
when the ion crystal as a whole is dragged across the optical lattice, the atoms first tend to stick in the lattice troughs,
bound there by their preference for the lower electric potential, as well as by the Coulomb forces that keep the atoms apart.
If enough force is applied, the ion crystal suddenly slips, as the atoms collectively jump to the next trough. t like an earthquake,
Vuletic says. here force building up, and then there suddenly a catastrophic release of energy. he group continued to stretch
and squeeze the ion crystal to manipulate the arrangement of atoms, and discovered that if the atom spacing is mismatched from that of the optical lattice,
friction between the two surfaces vanishes. In this case the crystal tends not to stick then suddenly slip,
but to move fluidly across the optical lattice, much like a caterpillar inching across the ground.
For instance, in arrangements where some atoms are in troughs while others are at peaks, and still others are somewhere in between,
as the ion crystal is pulled across the optical lattice, one atom may slide down a peak a bit,
releasing a bit of stress, and making it easier for a second atom to climb out of a trough
which in turn pulls a third atom along, and so on. hat we can do is adjust at will the distance between the atoms to either be matched to the optical lattice for maximum friction,
or mismatched for no friction, Vuletic says. Gangloff adds that the group technique may be useful
not only for realizing nanomachines, but also for controlling proteins, molecules, and other biological components. n the biological domain, there are various molecules
and atoms in contact with one another, sliding along like biomolecular motors, as a result of friction or lack of friction, Gangloff says. o this intuition for how to arrange atoms so as to minimize
or maximize friction could be applied. obias Schaetz, a professor of physics at the University of Freiburg in Germany, sees the results as a lear breakthroughin gaining insight into therwise inaccessible fundamental physics.
The technique he says, may be applied to a number of areas, from the nanoscale to the macroscale. he applications and related impact of their novel method propels a huge variety of research fields investigating effects relevant from raft tectonics down to biological systems
and motor proteins, says Schaetz, who was involved not in the research. ust imagine a nanomachine where we could control friction to enhance contact for traction,
or mitigate drag on demand. his work was funded in part by the National Science Foundation and the National Science and Engineering Research Council of Canada a
#Toward tiny, solar-powered sensors The latest buzz in the information technology industry regards he Internet of thingsthe idea that vehicles, appliances, civil-engineering structures, manufacturing equipment,
and even livestock would have embedded their own sensors that report information directly to networked servers,
#New manufacturing approach slices lithium-ion battery cost in half An advanced manufacturing approach for lithium-ion batteries, developed by researchers at MIT and at a spinoff company called 24m,
The existing process for manufacturing lithium-ion batteries, he says, has changed hardly in the two decades
In this so-called low battery, the electrodes are suspensions of tiny particles carried by a liquid
it is composed of a similar semisolid, colloidal suspension of particles. Chiang and Carter refer to this as a emisolid battery. impler manufacturing processthis approach greatly simplifies manufacturing,
while a flow battery system is appropriate for battery chemistries with a low energy density (those that can only store a limited amount of energy for a given weight),
for high-energy density devices such as lithium-ion batteries, the extra complexity and components of a flow system would add unnecessary extra cost.
e realized that a better way to make use of this flowable electrode technology was to reinvent the lithium ion manufacturing process. nstead of the standard method of applying liquid coatings to a roll of backing material,
Having the electrode in the form of tiny suspended particles instead of consolidated slabs greatly reduces the path length for charged particles as they move through the material a property known as ortuosity.
While conventional lithium-ion batteries are composed of brittle electrodes that can crack under stress the new formulation produces battery cells that can be bent,
With traditional lithium-ion production plants must be built at large scale from the beginning in order to keep down unit costs,
and go-no go decisions. iswanathan adds that 24m new battery design ould do the same sort of disruption to lithium ion batteries manufacturing as
There are plans to add sensors for radiation, temperature and carbon monoxide in future models. For this first manufacturing run, the startup aims to gather feedback from police,
The process involves combining oil with water under such high pressures and temperatures that they mix together, molecule by molecule,
One approach calls for using water rather than natural gas as the source of the hydrogen molecules needed for key chemical reactions in the refining process.
so the molecules can eeone another and chemically react. But using upercriticalwater solves that problem.
and oil molecules react and about the flows and mixing behaviors that will produce the desired reactions and reaction products.
and break down large hydrocarbon molecules to happen and then stop the process to prevent further reactions that form products you don want,
a large molecule made up of 12 carbon atoms, 26 hydrogen atoms, and one atom of sulfur. To test the impact of the SCW,
they performed two parallel experiments. In one, they heated hexyl sulfide without adding water; in the other, they mixed the hexyl sulfide with SCW.
forming a smaller molecule with the sulfur atom in a very reactive form. In the absence of water, that highly reactive sulfur-bearing molecule would join with others like itself to form a long chain
and eventually become coke. But in the presence of water, it reacts with the water,
At first, the vortices are separate swirls that spin in opposite directions, mixing the oil and SCW together.
and mixing rates decay. The colored circles in Figure 2 show mixing between the two fluids at five cross sections located along the pipe.
maybe they could use our particles as well, Brandl says. hen we came up with the idea to use our particles to remove toxic chemicals, pollutants,
or hormones from water, because we saw that the particles aggregate once you irradiate them with UV LIGHT. trap for ater-fearingpollutionthe researchers synthesized polymers from polyethylene glycol,
a widely used compound found in laxatives, toothpaste, and eye drops and approved by the Food and Drug Administration as a food additive,
in a solution hydrophobic pollutant molecules move toward the hydrophobic nanoparticles, and adsorb onto their surface,
the stabilizing outer shell of the particles is shed, and now nrichedby the pollutants they form larger aggregates that can then be removed through filtration, sedimentation,
according to the researchers, was confirming that small molecules do indeed adsorb passively onto the surface of nanoparticles. o the best of our knowledge,
it is the first time that the interactions of small molecules with preformed nanoparticles can be measured directly,
and molecules. he interactions we exploit to remove the pollutants are nonspecific, Brandl says. e can remove hormones, BPA,
we showed in a system that the adsorption of small molecules on the surface of the nanoparticles can be used for extraction of any kind,
This allows for much higher energy-efficiency, and orders-of-magnitude faster switching frequency meaning power-electronics systems with these components can be made much smaller.
#Researchers use oxides to flip graphene conductivity Graphene a one-atom thick lattice of carbon atoms is touted often as a revolutionary material that will take the place of silicon at the heart of electronics.
The unmatched speed at which it can move electrons plus its essentially two-dimensional form factor make it an attractive alternative
By demonstrating a new way to change the amount of electrons that reside in a given region within a piece of graphene they have a proof-of-principle in making the fundamental building blocks of semiconductor devices using the 2-D material.
because its charge-carrier density the number of free electrons it contains can be increased easily
To resolve that imbalance you could have other ions come in and bond or have the oxide lose
or gain electrons to cancel out those charges but we've come up with a third way.
Now if the oxide surface says'I wish I had more negative charge'instead of the oxide gathering ions from the environment
or gaining electrons the graphene says'I can hold the electrons for you and they'll be right nearby.'
and the possibility of waveguiding lensing and periodically manipulating electrons confined in an atomically thin material.
or by binding ions from the aqueous solution the researchers were able to show the relationship between the polarization of the oxide
but that's the direction we want to take it Rappe said There are some oxides that can be repolarized on the timescale of nanoseconds
#Researchers make magnetic graphene Graphene a one-atom thick sheet of carbon atoms arranged in a hexagonal lattice has many desirable properties.
The finding has the potential to increase graphene's use in computers as in computer chips that use electronic spin to store data.
Researchers find magnetic state of atoms on graphene sheet impacted by substrate it's grown on More information:
Graphene edges can be tailor-made Theoretical physicists at Rice university are living on the edge as they study the astounding properties of graphene.
The way atoms line up along the edge of a ribbon of graphenehe atom-thick form of carbonontrols
but semiconductors allow a measure of control over those electrons. Since modern electronics are all about control,
with each six-atom unit forming a hexagon. The edges of pristine zigzags look like this://Turning the hexagons 30 degrees makes the edges"armchairs"
which atoms in graphene are enticed to shift around to form connected rings of five and seven atoms.
Yakobson, Zhang and Rice postdoctoral researcher Alex Kutana used density functional theory, a computational method to analyze the energetic input of every atom in a model system,
The researchers have used the technique to determine that materials with a highly organized structure at the nanoscale are not more efficient at creating free electrons than poorly organized structures#a finding
First the cell absorbs sunlight which excites electrons in the active layer of the cell.
Each excited electron leaves behind a hole in the active layer. The electron and hole is called collectively an exciton.
In the second step called diffusion the exciton hops around until it encounters an interface with another organic material in the active layer.
During dissociation the exciton breaks apart freeing the electron and respective hole. In step four called charge collection the free electron makes its way through the active layer to a point where it can be harvested.
In previous organic solar cell research there was ambiguity about whether differences in efficiency were due to dissociation or charge collection#because there was no clear method for distinguishing between the two.
Was a material inefficient at dissociating excitons into free electrons? Or was the material just making it hard for free electrons to find their way out?
To address these questions the researchers developed a method that takes advantage of a particular characteristic of light:
so that it runs parallel to the long axis of organic solar cell molecules it will be absorbed; but if the light runs perpendicular to the molecules it passes right through it.
The researchers created highly organized nanostructures within a portion of the active layer of an organic solar cell meaning that the molecules in that portion all ran the same way.
They left the remaining regions of the cell disorganized meaning the molecules ran in a bunch of different directions.
This design allowed the researchers to make the organized areas of the cell effectively invisible by controlling the polarity of light aimed at the active layer.
and it tells us that we don't need highly ordered nanostructures for efficient free electron generation.
A similar effect can be realized at a much smaller scale by using arrays of metallic nanostructures since light of certain wavelengths excites collective oscillations of free electrons known as plasmon resonances in such structures.
Joel Yang and Shawn Tan at the A*STAR Institute of Materials Research and Engineering and co-workers used an electron beam to form arrays of approximately 100-nanometer-tall pillars.
The ytterbium is dense in electrons property that facilitates detection by CT SCANS. The Pop wrapper has biophotonic qualities that make it a great match for fluorescence
""Another advantage of this core/shell imaging contrast agent is that it could enable biomedical imaging at multiple scales, from single-molecule to cell imaging,
photoacoustic and radionuclide imaging abilities that the agent possesses.""Lovell says the next step in the research is to explore additional uses for the technology.
For example, it might be possible to attach a targeting molecule to the Pop surface that would enable cancer cells to take up the particles,
An electric field at the nozzle opening causes ions to form on the meniscus of the ink droplet.
The electric field pulls the ions forward deforming the droplet into a conical shape. Then a tiny droplet shears off and lands on the printing surface.
Yingnan Zhao decided to use nanometre-sized colloidal palladium particles, as their dimensions can be controlled easily.
These particles are fixed to a surface, so they do not end up in the mains water supply. However, it is important to stop them clumping together,
Unfortunately, these stabilizers tend to shield the surface of the palladium particles, which reduces their effectiveness as a catalyst.
Molecules designed for this purpose are deposited onto a surface in such a way that they react with each other
) centre extended this very concept to new molecules that were forming wider graphene nanoribbons and therefore with new electronic properties This same group has managed now to go a step further by creating through this self-assembly heterostructures that blend segments of graphene nanoribbons of two different widths.
#Researchers find exposure to nanoparticles may threaten heart health Nanoparticles extremely tiny particles measured in billionths of a meter are increasingly everywhere and especially in biomedical products.
We also wanted to use nanoparticles as a model for ultrafine particle (UFP) exposure as cardiovascular disease risk factors.
A recent update from the American Heart Association also suggested that fine particles in air pollution leads to elevated risk for cardiovascular diseases.
However more research was needed to examine the role of ultrafine particles (which are much smaller than fine particles) on atherosclerosis development and cardiovascular risk.
and optical simulation revealed that such improvement was contributed by the superior photon capturing capability of the nanobowl.
Solar cells based on nanobowl with pitch of 1000 nm exhibited the best photon absorption in photoactive layer leading to the highest short-circuit current density of 9. 41 ma cm-2 among all nanobowl substrates.
The higher the voltage the more electrons can leak out into the insulation material a process which leads to breakdown.
Fullerenes prevent electrical trees from forming by capturing electrons that would otherwise destroy chemical bonds in the plastic.
This means they have unsurpassed a hitherto ability to capture electrons and thus protect other molecules from being destroyed by the electrons.
To arrive at these findings, the researchers tested a number of molecules that are used also within organic solar cell research at Chalmers.
The molecules were tested using several different methods, and were added to pieces of insulation plastic used for high-voltage cables.
The pieces of plastic were subjected then to an increasing electric field until they crackled. Fullerenes turned out to be the type of additive that most effectively protects the insulation plastic.
For example using an optically active particle like gold (Au) will provide excellent contrast in near infrared (NIR) imaging
Magnetically active particles like iron (Fe) can enable physical therapies by generating heat when exposed to alternating magnetic fields causing cell death (magnetic hyperthermia).
Mechanochemical Stimulation of MCF7 Cells with Rod-shaped Fe Au Janus Particles Induces Cell Death Through Paradoxical Hyperactivation of ERK.
#Stacking two-dimensional materials may lower cost of semiconductor devices A team of researchers led by North carolina State university has found that stacking materials that are only one atom thick can create semiconductor junctions that transfer charge efficiently regardless of
For example in photonic devices like solar cells lasers and LEDS the junction is where photons are converted into electrons or vice versa.
By using a protein recognised by the immune system to effectively disguise carbon nanoparticles we will be able to deploy these tiny particles to target hard-to-reach areas without damaging side effects to the patient.
These techniques rely on specialized lenses electron beams or lasers-all of which are extremely expensive. Other conventional techniques use mechanical probes
And ultimately we want to look at ways of controlling the placement of particles on the photosensitive film in patterns other than uniform arrays.
The paper Sculpting Asymmetric Hollow-Core Three-dimensional Nanostructures Using Colloidal Particles was published online Dec 8 in the journal Small l
Thanks to state-of-the-art X-ray analysis provided by Argonne's Advanced Photon Source (APS) a DOE Office of Science user facility the researchers identified the cause of the dumbbell formation as lattice mismatch in
which the spacing between the atoms in the two materials doesn't align. Essentially you can think of lattice mismatch as having a row of smaller boxes on the bottom layer and larger boxes on the top layer.
The mismatch can be handled by the first two layers of gold atoms creating the core-shell effect
The arrangement of atoms is the same in the two materials but the distance between atoms is said different Argonne postdoctoral researcher Soon Gu Kwon.
Eventually this becomes unstable and the growth of the gold becomes unevenly distributed. As the gold continues to accumulate on one side of the seed nanoparticle small quantities slide down the side of the nanoparticle like grains of sand rolling down the side of a sand hill creating the dumbbell shape.
The team's discovery comes after nearly a century of failed attempts by other labs to compress separate carbon-containing molecules like liquid benzene into an ordered diamond-like nanomaterial.
Badding's team is the first to coax molecules containing carbon atoms to form the strong tetrahedron shape then link each tetrahedron end to end to form a long thin nanothread.
He describes the thread's width as phenomenally small only a few atoms across hundreds of thousands of times smaller than an optical fiber enormously thinner that an average human hair.
The molecule they compressed is benzene a flat ring containing six carbon atoms and six hydrogen atoms.
During the compression process the scientists report the flat benzene molecules stack together bend and break apart.
Then as the researchers slowly release the pressure the atoms reconnect in an entirely different yet very orderly way.
That the atoms of the benzene molecules link themselves together at room temperature to make a thread is shocking to chemists and physicists.
when the benzene molecule breaks under very high pressure its atoms want to grab onto something else
and the Carnegie Institution for Science including X-ray diffraction neutron diffraction Raman spectroscopy first-principle calculations transmission electron microscopy and solid-state nuclear magnetic resonance (NMR).
Our discovery that we can use the natural alignment of the benzene molecules to guide the formation of this new diamond nanothread material is really interesting
because it opens the possibility of making many other kinds of molecules based on carbon and hydrogen Badding said.
You can attach all kinds of other atoms around a core of carbon and hydrogen.
The dream is to be able to add other atoms that would be incorporated into the resulting nanothread.
#Controlled emission and spatial splitting of electron pairs demonstrated In quantum optics generating entangled and spatially separated photon pairs (e g. for quantum cryptography) is already a reality.
So far it has however not been possible to demonstrate an analogous generation and spatial separation of entangled electron pairs in solids.
Physicists from Leibniz University Hannover and from the Physikalisch-Technische Bundesanstalt (PTB) have taken now a decisive step in this direction.
They have demonstrated for the first time the on-demand emission of electron pairs from a semiconductor quantum dot and verified their subsequent splitting into two separate conductors.
This for example allows the controlled generation of pairs of entangled but spatially separated photons which are of essential importance for quantum cryptography.
An analogous generation and spatial separation of entangled electrons in solids would be of fundamental importance for future applications
As an electron source the physicists from Leibniz University Hannover and from PTB used so-called semiconductor single-electron pumps.
Controlled by voltage pulses these devices emit a defined number of electrons. The single-electron pump was operated in such a way that it released exactly one electron pair per pulse into a semiconducting channel.
A semitransparent electronic barrier divides the channel into two electrically distinct areas. A correlation measurement then recorded
whether the electron pairs traversed the barrier or whether they were reflected or split by the barrier.
It could be shown that for suitable parameters more than 90%of the electron pairs were split
This is an important step towards the envisioned generation and separation of entangled electron pairs in semiconductor components s
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