the resulting increase in length and decrease in cross-sectional area restricts the flow of electrons through the material.
because electrons can travel over such a hierarchically buckled sheath as easily as they can traverse a straight sheath."
The researchers report in Nano Letters that by combining inorganic semiconductor nanocrystals with organic molecules, they have succeeded in"upconverting"photons in the visible and near-infrared regions of the solar spectrum."
The hybrid material we have come up with first captures two infrared photons that would normally pass right through a solar cell without being converted to electricity,
then adds their energies together to make one higher energy photon. This upconverted photon is absorbed readily by photovoltaic cells,
generating electricity from light that normally would be wasted.""Bardeen added that these materials are essentially"reshaping the solar spectrum
The cadmium selenide nanocrystals could convert visible wavelengths to ultraviolet photons, while the lead selenide nanocrystals could convert near-infrared photons to visible photons.
In lab experiments the researchers directed 980-nanometer infrared light at the hybrid material, which then generated upconverted orange yellow fluorescent 550-nanometer light,
almost doubling the energy of the incoming photons. The researchers were able to boost the upconversion process by up to three orders of magnitude by coating the cadmium selenide nanocrystals with organic ligands,
but are good at combining two lower energy photons to a higher energy photon. By using a hybrid material,
the inorganic component absorbs two photons and passes their energy on to the organic component for combination.
The organic compounds then produce one high-energy photon. Put simply, the inorganics in the composite material take light in;
"Besides solar energy, the ability to upconvert two low energy photons into one high energy photon has potential applications in biological imaging, data storage and organic light-emitting diodes.
from red to blue, can impact any technology that involves photons as inputs or outputs,
The colloid form of these particles have very interesting properties and characteristics, and their size, shape and properties at nanometric scale can be controlled very well.
in addition to other parameters such as density difference in electrical charges and type and density of surface atoms,
which are affected by the morphology of the particles, prevent the easily formation of a stable colloid.
For instance, the X-ray radiation method cannot detect contaminants with sizes smaller than 1 mm with current practical X-ray levels,
and it cannot be applied for the inspection of foods that have lactic acid bacteria because X-ray radiation causes ionization of such foods.
#Meet the high-performance single-molecule diode: Major milestone in molecular electronics scored by Berkeley Lab and Columbia University team"Using a single symmetric molecule, an ionic solution and two gold electrodes of dramatically different exposed surface areas,
we were able to create a diode that resulted in a rectification ratio, the ratio of forward to reverse current at fixed voltage, in excess of 200,
which is a record for single-molecule devices, "says Jeff Neaton, Director of the Molecular Foundry, a senior faculty scientist with Berkeley Lab's Materials sciences Division and the Department of physics at the University of California Berkeley,
"This leads to different electrostatic environments surrounding the two electrodes and superlative single-molecule device behavior."
"With"smaller and faster"as the driving mantra of the electronics industry, single-molecule devices represent the ultimate limit in electronic miniaturization.
In 1974, molecular electronics pioneers Mark Ratner and Arieh Aviram theorized that an asymmetric molecule could act as a rectifier, a one-way conductor of electric current.
Since then, development of functional single-molecule electronic devices has been a major pursuit with diodes-one of the most widely used electronic components-being at the top of the list.
The asymmetry of a p-n junction presents the electrons with an"on/off"transport environment.
Scientists have fashioned previously single-molecule diodes either through the chemical synthesis of special asymmetric molecules that are analogous to a p-n junction;
or through the use of symmetric molecules with different metals as the two electrodes. However, the resulting asymmetric junctions yielded low rectification ratios,
and low forward current. Neaton and his colleagues at Columbia University have discovered a way to address both deficiencies."
"Electron flow at molecular length-scales is dominated by quantum tunneling, "Neaton explains.""The efficiency of the tunneling process depends intimately on the degree of alignment of the molecule's discrete energy levels with the electrode's continuous spectrum.
In a molecular rectifier, this alignment is enhanced for positive voltage, leading to an increase in tunneling,
and tunneling probability in single-molecule junctions. This method allowed myself and Zhenfei Liu to understand the diode behavior quantitatively."
"In collaboration with Columbia University's Latha Venkataraman and Luis Campos and their respective research groups, Neaton and Liu fabricated a high-performing rectifier from junctions made of symmetric molecules with molecular resonance
in nearly perfect alignment with the Fermi electron energy levels of the gold electrodes. Symmetry was broken by a substantial difference in the size of the area on each gold electrode that was exposed to the ionic solution.
The Columbia group's experiments showed that with the same molecule and electrode setup, a nonionic solution yields no rectification at all."
"The Berkeley Lab-Columbia University team believes their new approach to a single-molecule diode provides a general route for tuning nonlinear nanoscale-device phenomena that could be applied to systems beyond single-molecule junctions
"With the increasing level of experimental control at the single-molecule level, and improvements in theoretical understanding and computational speed and accuracy, we're just at the tip of the iceberg with
The paper is titled"Single-molecule diodes with high rectification ratios through environmental control.""Other co-authors are Brian Capozzi, Jianlong Xia, Olgun Adak, Emma Dell, Zhen-Fei Liu and Jeffrey Taylor r
#Sol-gel capacitor dielectric offers record-high energy storage If the material can be scaled up from laboratory samples,
The new material is composed of a silica sol-gel thin film containing polar groups linked to the silicon atoms and a nanoscale self-assembled monolayer of an octylphosphonic acid,
The bilayer structure blocks the injection of electrons into the sol-gel material providing low leakage current, high breakdown strength and high energy extraction efficiency."
"Sol-gels with organic groups are well known and fatty acids such as phosphonic acids are noted well known Joseph Perry, a professor in the School of Chemistry and Biochemistry at the Georgia Institute of technology."
Dielectric materials can provide fast charge and discharge response, high energy storage, and power conditioning for defense, medical and commercial applications.
while maintaining high energy density, demonstrating its flexibility. But they were still seeing high current leakage.
This biomimetic membrane is composed of lipids--fat molecules --and protein-appended molecules that form water channels that transfer water at the rate of natural membranes,
and self-assembles into 2-dimensional structures with parallel channels.""Nature does things very efficiently
"We were surprised to see transport rates approaching the'holy grail'number of a billion water molecules per channel per second,
and shuttle data with light instead of electrons. Electrical and computer engineering associate professor Rajesh Menon and colleagues describe their invention today in the journal Nature Photonics Silicon photonics could significantly increase the power and speed of machines such as supercomputers
"But that information has to be converted to electrons when it comes into your laptop. In that conversion, you're slowing things down.
"Photons of light carry information over the Internet through fiber-optic networks. But once a data stream reaches a home or office destination,
the photons of light must be converted to electrons before a router or computer can handle the information.
And because photonic chips shuttle photons instead of electrons, mobile devices such as smartphones or tablets built with this technology would consume less power,
#Scientists print low cost radio frequency antenna with graphene ink (Nanowerk News) Scientists have moved graphene--the incredibly strong and conductive single-atom-thick sheet of carbon--a significant step along the path
which enabled efficient radio frequency radiation, was one of the most exciting aspects of the experiment,
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("Tunable Lightatter
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.
To retain high energy density, nanostructures (such as nanowires) must be paced into dense"nanostructure forests, "producing 3-D nanogeometries in
which ions and electrons must rapidly move. Researchers have built arrays of nanobatteries inside billions of ordered,
identical nanopores in an alumina template to determine how well ions and electrons can do their job in such ultrasmall environments.
Up to a billion of these nanopore batteries could fit in a grain of sand. The nanobatteries were fabricated by atomic layer deposition to make oxide nanotubes (for ion storage) inside metal nanotubes for electron transport, all inside each end of the nanopores.
The tiny nanobatteries work extremely well: they can transfer half their energy in just a 30 second charge
and well-controlled fabrication of nanotubular electrodes to accommodate ion motion in and out and close contact between the thin nested tubes to ensure fast transport for both ions and electrons.
Complete nanobatteries are formed in each nanopore of a dense nanopore array (2 billion per cm2),
while their ion insertion processes occur very fast, much like what happens at the surface of a double-layer capacitor.
and discharge) and for extended cycling, demonstrating that precise nanostructures can be constructed to assess the fundamentals of ion
and electron transport in nanostructures for energy storage and to test the limits of 3-D nanobattery technology y
#Large-scale simulations of atom dynamics An international research team has developed a highly efficient novel method for simulating the dynamics of very large systems potentially containing millions of atoms,
and gaining a previously unattainable understanding of processes such as electron, water or ion transport or chemical reactions.
to only a few hundred atoms. For the first time, this new method provides the means of performing atomic and electronic structure simulations on much larger systems,
Matter is composed of atoms, and its physical characteristics are determined by the complex interactions between atoms and electrons.
Theoreticians use quantum mechanics to calculate the forces between atoms, and the behaviour of electrons in materials.
Specifically, first-principles simulations are based on quantum mechanics, and are a powerful technique widely used to uncover diverse properties of matter and materials at the atomic scale.
The research team led by TYC member David Bowler, UCL and NIMS MANA and Tsuyoshi Miyazaki at NIMS,
used high performance computing to introduce a new technique, where the time required for the calculations increases linearly with the number of atoms,
to perform first-principles dynamical simulations of systems comprising more than 30,000 atoms, 100 times larger than is usual with conventional methods.
The technique has further been used to calculate properties of over 2 million atoms. This new method will be an invaluable tool for those using predictive computational modelling and,
as most simulations are stuck below 1, 000 atoms, it will open the doors to studying completely new areas of physics s
#Freshly squeezed vaccines (Nanowerk News) MIT researchers have shown that they can use a microfluidic cell-squeezing device to introduce specific antigens inside the immune systems B cells,
As a result, large molecules antigens, in the case of this study can enter before the membrane reseals.
so molecules can enter. Courtesy of SQZ Biotech) Through Cellsqueeze, the device platform originally developed at MIT,
Discovered in the 1970s, SERS is a sensing technique prized for its ability to identify chemical and biological molecules in a wide range of fields.
A Universal Surface-Enhanced Raman Spectroscopy Substrate for All Excitation Wavelengths"),the photonics advancement aims to improve our ability to detect trace amounts of molecules in diseases, chemical warfare agents, fraudulent
and measure chemical and biological molecules using a broadband nanostructure that traps wide range of light,
When a powerful laser interacts chemical and biological molecules, the process can excite vibrational modes of these molecules and produce inelastic scattering, also called Raman scattering, of light.
As the beam hits these molecules, it can produce photons that have a different frequency from the laser light.
While rich in details, the signal from scattering is weak and difficult to read without a very powerful laser.
if scientists want to use a different laser to test the same molecules. In turn, this requires more chemical molecules and substrates,
increasing costs and time to perform the test. The universal substrate solves the problem because it can trap a wide range of wavelengths
"The ability to detect even smaller amounts of chemical and biological molecules could be helpful with biosensors that are used to detect cancer, Malaria, HIV and other illnesses."
#Exciton, exciton on the wall Researchers have observed, in metals for the first time, transient excitons the primary response of free electrons to light.
Here, the researchers discovered that the surface electrons of silver crystals can maintain the excitonic state more than 100 times longer than for the bulk metal,
which excite coherent three-photon photoemission at a single crystal silver surface. The interferogram is taken from a movie of photoelectron energy vs. momentum with one frame corresponding to a 50-attosecond delay.
the light shakes the metals free electrons and the resulting acceleration of electrons creates a nearly perfect replica of the incident light providing a reflection.
Excitons, or particles of the light-matter interaction where light photons become temporarily entangled with electrons in molecules
This discovery sheds light on the primary excitonic response of solids which could allow quantum control of electrons in metals, semiconductors,
It also potentially allows for the generation of intense femotosecond electron pulses that could increase resolution for time-resolved electron microscopes that follow the motion of individual atoms
and molecules as they rearrange themselves during structural transitions or chemical reactions s
#The robot that learns everything from scratch (Nanowerk News) Two researchers at NTNU have made a robot that learns like a young child.
#Powerful tool to control living cells at will by light A research group at the University of Tokyo has developed small photoswitching proteins that enable the highly accurate control of the activity of various intracellular molecules at will by irradiation with light.
which the molecules are stabilised so that the material does not collapse.""The result is a material that is both strong, light and soft,
in association with Montpellier Regional University Hospital and Stanford university, have transformed bacteria into"secret agents"that can give warning of a disease based solely on the presence of characteristic molecules in the urine or blood.
"In vitro"diagnosis is based on the presence in physiological fluids (blood and urine, for example) of molecules characteristic for a particular disease.
It is thus now possible to implant simple genetic"programmes"into living cells in response to different combinations of molecules.
The key is the structuring of this layer-the protective particles arrange themselves like roof tiles.
As in a wall, several layers of particles are placed on top of each other in an offset arrangement;
The specially formulated mixture contains a solvent, a binder and nanoscale and platelet-like particles;
have allowed snapshot imaging of a single 300 nm gold nanocrystal in the picosecond time interval after the particle was excited with a laser.
while preserving the integrity and large surface area of the particle. Ian Robinson, coordinator of the project said"Bragg Coherent Diffraction Imaging is an emerging X-ray technique with great potential for probing the dynamics of matter.
These nanoparticles are adapted specifically to the particular application by Small Molecule Surface Modification (SMSM. How this approach can be used to produce custom-tailored coatings will be demonstrated at the Techconnect World trade fair on 15 and 16 june in WASHINGTON DC, USA,
Small Molecule Surface Modification (SMSM) bestows specific combinations of desired properties, for example hydrophilic, hydrophobic, adhesive, anti-adhesive
it is absorbed by electrons in the gold arms. The arms are so thin that the electrons are forced to move along the spiral.
Electrons that are driven toward the center absorb enough energy so that some of them emit blue light at double the frequency of the incoming infrared light.
This is similar to what happens with a violin string when it is bowed vigorously, said Stevenson Professor of Physics Richard Haglund,
The electrons at the center of the spirals are driven pretty vigorously by the lasers electric field.
because the polarization pushes the electrons toward the center of the spiral. Counterclockwise polarized light,
because the polarization tends to push the electrons outward so that the waves from all around the nano-spiral interfere destructively.
So far, Davidson has experimented with small arrays of gold nano-spirals on a glass substrate made using scanning electron-beam lithography.
which half of the electronic states that can contribute to the material electrical conductivity are occupied by electrons,
because electrons can freely travel around by moving in and out of the empty sites. In this organic material,
however, strong repulsion between the electrons in the full and empty states suppresses free movement.
The layered structure and arrangement of molecules into layered triangular patterns (Fig. 1) removes the freedom of the electrons'spin such that the molecules line up
and form valence bonds. The only way for electrons to break free is to forcefully add additional electrical charge to the system,
or to subject the material to high pressure. In both cases, the electronic states change such that the material undergoes a Mott transition to a conducting state.
a solid material with spin-transition solution-like behaviour Spintronics is called a discipline to change the way we store
and manage digital information by using the spin of electrons. Metal complexes showing spin-transition (i e. reversible interconversion between different isomers) are among the best candidates for the preparation of molecular memories and spintronic devices.
A major bottleneck for the use of these compounds in such high-added value applications is however the lack of reliable methodologies for their integration into solid materials,
As such, a general and scalable strategy enabling direct transfer of spin-transition behaviour from solution to the solid state is yet to be developed.
The present study demonstrates that this methodology meets the most important conditions required to integrate spin-transition into functional materials:(
iii) it enables incorporation of spin-transition into any final solid matrix of choice by simple dispersion of the liquid-filled capsules.
All these features, in combination with its simplicity and the lack of synthetic modification of the complex, makes this strategy very appealing for the future fabrication of solid functional materials based on spin transition materials s
Semiconductor QDS can produce full-color luminescence through tuning of the particle size. QDS have attracted significant attention as potential components of next-generation solid-state light sources,
The researchers have studied the sensitivity of thermometers created with a handful of atoms, small enough to be capable of showing typical quantum-style behaviours.
which deals with ultra-precise measures in quantum systems. The physicists searched to find the maximum precision which could be achieved in a real situation, in
San diego. Shawkey and his team sought to produce synthetic particles that mimic the tiny packets of melanin found in feathers.
This produces a plasma consisting of carbon ions, which is deposited as a coating on the workpiece in the vacuum.
a magnetic field guides the plasma and filters out any particles of dirt. The laser arc method can be used to deposit very thick ta-C coatings of up to 20 micrometers at high coating rates.
One Dalton is roughly the mass of a proton or neutron, and several thousand Daltons are the mass of individual proteins and DNA molecules.
So the new optical sensor will allow for diagnosing diseases long before they can be detected by any other method,
it'll capture the viral particles in the analyzed environment. Oscillations will occur at a lower
configured to detect different particles or molecules. The price, thanks to the simplicity of the design, will most likely depend on the number of sensors,
simple process for making platinum"nano-raspberries"microscopic clusters of nanoscale particles of the precious metal("Stability and phase transfer of catalytically active platinum nanoparticle suspensions").
The raspberry color suggests the particles? corrugated shape, which offers high surface area for catalyzing reactions in fuel cells.
Individual particles are 3-4 nm in diameter but can clump into bunches of 100 nm
To learn how such formulas affect particle properties, the NIST team measured particle clumping in four different solvents for the first time.
For applications such as liquid methanol fuel cells, catalyst particles should remain separated and dispersed in the liquid,
not clumped.""Our innovation has little to do with the platinum and everything to do with how new materials are tested in the laboratory,
We made the particles in water and tested whether you could put them in other solvents.
"The NIST team measured conditions under which platinum particles, ranging in size from 3 to 4 nanometers (nm) in diameter,
where solvent molecules lack regions with strongly positive or negative charges. Water is a strongly polar molecule.
The researchers expected that. What they didn't expect is that the trend doesn't scale in a predictable way.
the researchers concluded that the particles could be transferred to that solvent, assuming they were to be used within a few dayseffectively putting an expiration date on the catalyst t
and UV radiation (Nanowerk News) RMIT University researchers have created wearable sensor patches that detect harmful UV radiation and dangerous, toxic gases such as hydrogen and nitrogen dioxide (Small,"Stretchable
stretchy electronic sensors are also capable of detecting harmful levels of UV radiation known to trigger melanoma.
and alert the user when radiation hits harmful levels. Gutruf said the research used zinc oxide-present in most sunscreens as a fine powder mixed into a lotion-as the UV sensing material.
High energy In this study, the researchers used a surprisingly high laser energy in comparison to earlier work,
An intense Gaussian-shaped x-ray pulse (transparent blue shape) has passed just through a cluster of Argon atoms (pink spheres.
A short time after excitation, the initial excitation of Argon's eighteen electrons (blue spheres) is observed at several places within cluster.
At longer times after excitation, many excited electrons are see escaping the cluster in all directions.
The x-ray electron-free laser (XFEL) is the perfect example of new technology and old perceptions converging on that narrow boundary between science and science fiction.
Firing pulses of a trillion x-ray photons at molecular-sized samples in time scales on the order of million-billionths of a second (femtoseconds
researchers are aiming for the Holy grail of ultra-fast X-ray Science single-particle 3d imaging with atomic resolution.
Understanding the effects that these ultra-intense x-ray pulses will have on their potential targets will take the team work of Argonne National Laboratorys Advanced Photon Source (APS) and the Argonne Leadership Computing Facility (ALCF), both
But first, many atoms and molecules will have to meet with a sci-fi appropriate demise. And the ability to capture
when x-ray photons collide with the electrons of a target samplea specific atom or enzyme molecule, for instanceand scatter.
These scatterings are captured as images by photon detectors inside the machine. From the dizzying cascade of lines
there emerges the information necessary to detect the electron locations of the sample before it was irradiated,
The photon/electron collisions create infinite and simultaneous quantum reactions, where electrons emerge and disappear and new particles propagate,
all of them creating those frantic lines etched on the detectors. To read between the lines, quite literally, Young
and Ho work closely with computational scientists at the ALCF to optimize their method within a molecular simulation program called LAMMPS.
Where the MD tracks the time evolution for all the particles in the system MC incorporates detailed information from quantum mechanics to simulate the interactions between the electrons and the XFEL pulses.
So MC takes all of the complicated quantum mechanics and recasts it in a simpler way, says ALCF assistant computational scientist, Chris Knight.
Unlike typical molecular simulations, the XFEL studies are computationally more intensive. The blast from the intense x-ray pulse produces more than a 10-fold increase in the number of particles,
which are generated on relatively faster timescales. And the processes which occur during and after the bombardment lead to rapid expansion of the system sizeor the simulated playing field on
But rather than try to calculate every electronic structure and excited particle during a simulation
and track the electronic configuration of every particle interacting with an x-ray pulse. Even with a computational cost significantly smaller than fully quantum mechanical simulations, some unique computational challenges remain before the team can exploit the full potential of the hybrid method.
The team continues to tweak the hybrid code as well as pulse rates by studying Argon clusters composed of 20 thousand to 2 million particles,
and nanodiamond materials composed of 1-100 million particles, with an end goal of mapping the electron pathways created by XFEL bursts.
According to Young, small bursts produce very high-resolution scattering patterns, while large bursts create radiation damage, causing smeared patterns and lower resolution.
All of the work with the XFEL was performed at the Linac Coherent light Source (LCLS) at Stanford universitys SLAC National Accelerator Laboratory
which provides a billion-fold more peak intensity than any other x-ray source in the world.
the APS will not conduct single-shot single-particle imaging studies, though the question of radiation damage still will apply.
Because synchrotron pulses are longer, computational efforts will have to propagate what happens during a short burst,
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