#Researchers improve thermal conductivity of common plastic by adding graphene coating (Phys. org) A team of engineering
and physics researchers with members from the U s. the U k. and the Republic of Muldova has found that covering a common type of plastic with a graphene coating can increase its conductivity by up to 600 times.
In their paper published in the journal Nano Letters the team describes their new technique
and how the coated materials they've created might be used in real world applications. Plastics are not very good conductors of heat they are generally in the 0. 15-0. 24 W/mk range
which is a good trait when it's produced as flakes and used as a stuffing inside a winter coat
but not so good when used in electronics that generally need to convey heat away from a source.
Engineers would like to use them in more applications however due to their very low cost light weight and durability.
Conversely graphene is an excellent conductor of heat (in the 2000-5000 W/mk range)
along with its other unique properties though notably a lot of that improvement is lost when applied to a substrate it's still much better than plastic though.
In this new effort the researchers sought to improve heat conduction in a plastic by applying graphene to its surface.
The type of plastic used PET is very common it's used to make soda bottles and a myriad of other products in a nearly limitless variety of shapes.
or even inside electronic devices to help move heat away from heat generating chips. The team next plans to work on creating models that have more detail and
which are based on multiscale simulations that will shed light on which sorts of real-world applications the coated plastics might best be used in.
Researchers combine graphene and copper in hopes of shrinking electronics More information: Thermal conductivity of Graphene Laminate Nano Lett. 2014 14 (9) pp 5155-5161.
DOI: 10.1021/nl501996v. On Arxiv: http://arxiv. org/ftp/arxiv/papers/1407/1407.1359. pdfabstractwe have investigated thermal conductivity of graphene laminate films deposited on polyethylene terephthalate substrates.
Two types of graphene laminate were studied as deposited and compressed in order to determine the physical parameters affecting the heat conduction the most.
and a set of suspended samples with the graphene laminate thickness from 9 to 44 m. The thermal conductivity of graphene laminate was found to be in the range from 40 to 90 W/mk at room temperature.
The thermal conductivity scales up linearly with the average graphene flake size in both uncompressed and compressed laminates.
The compressed laminates have higher thermal conductivity for the same average flake size owing to better flake alignment.
Coating plastic materials with thin graphene laminate films that have up to 600 higher thermal conductivity than plastics may have important practical implications s
#An unlikely use for diamonds Tiny diamonds are providing scientists with new possibilities for accurate measurements of processes inside living cells with potential to improve drug delivery and cancer therapeutics.
Published in Nature Nanotechnology researchers from Cardiff University have unveiled a new method for viewing nanodiamonds inside human living cells for purposes of biomedical research.
Nanodiamonds are very small particles (a thousand times smaller than human hair) and because of their low toxicity they can be used as a carrier to transport drugs inside cells.
They also show huge promise as an alternative to the organic fluorophores usually used by scientists to visualise processes inside cells and tissues.
and chemical degradation can often be toxic and significantly perturb or even kill cells. There is a growing consensus among scientists that nanodiamonds are one of the best inorganic material alternatives for use in biomedical research, because of their compatibility with human cells,
and due to their stable structural and chemical properties. Previous attempts by other research teams to visualise nanodiamonds under powerful light microscopes have run into the obstacle that the diamond material per se is transparent to visible light.
Locating the nanodiamonds under a microscope had relied on tiny defects in the crystal lattice which fluoresce under light illumination.
Production of the defects proved both costly and difficult to realise in a controlled way.
and in turn the image gleaned from the microscopic exploration of these flawed nanodiamonds, is sometimes also unstable.
In their latest paper, researchers from Cardiff University's Schools of Biosciences and Physics showed that non-fluorescing nanodiamonds (diamonds without defects) can be imaged optically
and far more stably via the interaction between the illuminating light and the vibrating chemical bonds in the diamond lattice structure which results in scattered light at a different colour.
called coherent anti-Stokes Raman scattering (CARS). By focusing these laser beams onto the nanodiamond, a high-resolution CARS image is generated.
Using an in-house built microscope, the research team was able to measure the intensity of the CARS light on a series of single nanodiamonds of different sizes.
The nanodiamond size was measured accurately by means of electron microscopy and other quantitative optical contrast methods developed within the researcher's lab. In this way,
they were able to quantify the relationship between the CARS light intensity and the nanoparticle size.
Consequently, the calibrated CARS signal enabled the team to analyse the size and number of nanodiamonds that had been delivered into living cells,
with a level of accuracy hitherto not achieved by other methods. Professor Paola Borri from the School of Biosciences, who led the study,
said:""This new imaging modality opens the exciting prospect of following complex cellular trafficking pathways quantitatively with important applications in drug delivery.
The next step for us will be to push the technique to detect nanodiamonds of even smaller sizes than what we have shown so far
and to demonstrate a specific application in drug delivery
#Tracking heat-driven decay in leading electric vehicle batteries Rechargeable electric vehicles are one of the greatest tools against rising pollution and carbon emissions and their widespread adoption hinges on battery performance.
Scientists specializing in nanotechnology continue to hunt for the perfect molecular recipe for a battery that drives down price increases durability and offers more miles on every charge.
One particular family of lithium-ion batteries composed of nickel cobalt and aluminum (NCA) offers high enough energy density a measure of the stored electricity in the battery that it works well in large-scale and long-range vehicles including electric cars and commercial aircraft.
There is however a significant catch: These batteries degrade with each cycle of charge and discharge.
As the battery cycles lithium ions shuttle back and forth between cathode and anode and leave behind detectable tracks of nanoscale damage.
Crucially the high heat of vehicle environments can intensify these telltale degradation tracks and even cause complete battery failure.
The relationship between structural changes and the catastrophic thermal runaway impacts both safety and performance said physicist Xiao-Qing Yang of the U s. Department of energy's Brookhaven National Laboratory.
The in depth understanding of that relationship will help us develop new materials and advance this NCA material to prevent that dangerous degradation.
To get a holistic portrait of the NCA battery's electrochemical reactions researchers in Brookhaven Lab's Chemistry department
and Center for Functional Nanomaterials (CFN) completed a series of three studies each delving deeper into the molecular changes.
The work spanned x-ray-based exploration of average material morphologies to surprising atomic-scale asymmetries revealed by electron microscopy.
After each cycle of charge/discharge or even incremental steps in either direction we saw the atomic structure transition from uniform crystalline layers into a disordered rock-salt configuration said Brookhaven Lab scientist Eric
Stach who leads CFN's electron microscopy group. During this transformation oxygen leaves the destabilized battery compound.
This excess oxygen leached at faster and faster rates over time actually contributes to the risk of failure and acts as fuel for a potential fire.
These new and fundamental insights may help engineers develop superior battery chemistries or nanoscale architectures that block this degradation.
Study 1: X-ray snapshots of heat-driven decompositionthe first study published in Chemistry of Materials explored the NCA battery using combined x-ray diffraction
and spectroscopy techniques where beams of high-frequency photons bombard and bounce off a material to reveal elemental structure and composition.
We were able to test the battery cycling in situ meaning we could watch the effects of increasing heat in real time said Brookhaven Lab chemist and study coauthor Seong Min Bak.
We pushed the fully charged NCA coin-cell battery out of thermal equilibrium by heating it all the way to 500 degrees Celsius.
and revealed the widespread transition from one crystal structure to another. The team also measured the amount of oxygen
and carbon dioxide released by the NCA sample a key indicator of potential flammability. The oxygen release peaked between 300 and 400 degrees Celsius during our trials
which is above the operating temperature for most vehicles Bak said. But that temperature threshold dropped for a highly charged battery suggesting that operating at full energy capacity accelerates structural degradation and vulnerability.
While they further confirmed the results with x-ray absorption spectroscopy and electron microscopy after the heating trials the team needed to map the changes at higher resolutions.
The next study also published in Chemistry of Materials used transmission electron microscopy (TEM) to pinpoint the effect of an initial charge on the battery's surface structure.
The highly focused electron beams available at CFN revealed individual atom positions as an applied current pushed pristine batteries to an overcharged state.
and Technology (KIST Even with just one charge on the NCA battery we saw changes in the crystalline structure
To capture the atoms'electronic structures the scientists used electron energy loss spectroscopy (EELS. In this technique measurements of the energy lost by a well-defined electron beam reveal local charge densities and elemental configurations.
We found a decrease in nickel and an increase in the electron density of oxygen Hwang said.
and leave holes in the NCA surface permanently damaging the battery's capacity and performance.
While this combined crystallographic and electronic data confirmed and clarified the earlier work temperature effects still needed to be explored with atomic precision.
Study 3: Thermal decay and real-time electron microscopythe final study published in Applied materials and Interfaces used in situ electron microscopy to track the heat-driven decomposition of NCA materials at different states of charge.
and began to shift toward disorder down at temperatures below 100 degrees Celsius definitely plausible for a lithium-ion battery's normal operation.
and that free oxygen would feed the fire springing from an overheated battery. The corroborating data in the three studies points to flaws in the chemistry
and architecture of NCA batteries including the surprising atomic asymmetries and suggests new ways to enhance durability including the use of nanoscale coatings that reinforce stable structures.
We plan to push these investigative techniques even further to track the battery's structure in real-time as it charges
and discharges under real operating conditions we call this in operando Stach said. Brookhaven's National Synchrotron Light source II will be a game-changer for this kind of experimentation and
I'm eager to take advantage of that facility's ultra-bright x-rays to track internal and surface evolutions in these materials s
#Breakthrough in molecular electronics paves the way for DNA-based computer circuits in the future In a paper published today in Nature Nanotechnology,
an international group of scientists announced the most significant breakthrough in a decade toward developing DNA-based electrical circuits.
The central technological revolution of the 20th century was the development of computers, leading to the communication and Internet era.
A computer with the memory of the average laptop today was the size of a tennis court in the 1970s.
Yet while scientists made great strides in reducing of the size of individual computer components through microelectronics,
they have been less successful at reducing the distance between transistors, the main element of our computers.
These spaces between transistors have been much more challenging and extremely expensive to miniaturize an obstacle that limits the future development of computers.
Molecular electronics, which uses molecules as building blocks for the fabrication of electronic components, was seen as the ultimate solution to the miniaturization challenge.
However to date, no one has actually been able to make complex electrical circuits using molecules. The only known molecules that can be designed pre to self-assemble into complex miniature circuits,
which could in turn be used in computers, are DNA molecules. Nevertheless, so far no one has been able to demonstrate reliably and quantitatively the flow of electrical current through long DNA molecules.
Now, an international group led by Prof. Danny Porath, the Etta and Paul Schankerman Professor in Molecular Biomedicine at the Hebrew University of Jerusalem, reports reproducible and quantitative measurements of electricity flow through long molecules made of four
DNA strands signaling a significant breakthrough towards the development of DNA-based electrical circuits. The research,
which could reignite interest in the use of DNA-based wires and devices in the development of programmable circuits, appears in the prestigious journal Nature Nanotechnology under the title"Long-range charge transport in single G-quadruplex DNA molecules."
"Prof. Porath is affiliated with the Hebrew University's Institute of Chemistry and its Center for Nanoscience and Nanotechnology.
The molecules were produced by the group of Alexander Kotlyar from Tel aviv University, who has been collaborating with Porath for 15 years.
The measurements were performed mainly by Gideon Livshits, a Phd student in the Porath group, who carried the project forward with great creativity, initiative and determination.
The research was carried out in collaboration with groups from Denmark, Spain, US, Italy and Cyprus. According to Prof.
Porath,"This research paves the way for implementing DNA-based programmable circuits for molecular electronics which could lead to a new generation of computer circuits that can be sophisticated more,
cheaper and simpler to make. k
#New nanodevice to improve cancer treatment monitoring In less than a minute, a miniature device developed at the University of Montreal can measure a patient's blood for methotrexate, a commonly used but potentially toxic cancer drug.
Just as accurate and ten times less expensive than equipment currently used in hospitals, this nanoscale device has an optical system that can rapidly gauge the optimal dose of methotrexate a patient needs,
while minimizing the drug's adverse effects. The research was led by Jean-François Masson and Joelle Pelletier of the university's Department of chemistry.
Methotrexate has been used for many years to treat certain cancers among other diseases, because of its ability to block the enzyme dihydrofolate reductase (DHFR.
This enzyme is active in the synthesis of DNA precursors and thus promotes the proliferation of cancer cells."
"While effective, methotrexate is also highly toxic and can damage the healthy cells of patients,
hence the importance of closely monitoring the drug's concentration in the serum of treated individuals to adjust the dosage,
"Masson explained. Until now, monitoring has been done in hospitals with a device using fluorescent bioassays to measure light polarization produced by a drug sample."
"The operation of the current device is based on a cumbersome, expensive platform that requires experienced personnel because of the many samples that need to be manipulated,
"Masson said. Six years ago, Joelle Pelletier, a specialist of the DHFR enzyme, and Jean-François Masson, an expert in biomedical instrument design, investigated how to simplify the measurement of methotrexate concentration in patients.
Gold nanoparticles on the surface of the receptacle change the colour of the light detected by the instrument.
The detected colour reflects the exact concentration of the drug in the blood sample. In the course of their research
they developed and manufactured a miniaturized device that works by surface plasmon resonance. Roughly, it measures the concentration of serum (or blood) methotrexate through gold nanoparticles on the surface of a receptacle.
In"competing"with methotrexate to block the enzyme, the gold nanoparticles change the colour of the light detected by the instrument.
And the colour of the light detected reflects the exact concentration of the drug in the blood sample.
The accuracy of the measurements taken by the new device were compared with those produced by equipment used at the Maisonneuve-Rosemont Hospital in Montreal."
"In the near future, we can foresee the device in doctors'offices or even at the bedside,
"While traditional equipment requires an investment of around $100, 000, the new mobile device would likely cost ten times less, around $10, 000.0
#Team reveals molecular structure of water at gold electrodes When a solid material is immersed in a liquid the liquid immediately next to its surface differs from that of the bulk liquid at the molecular level.
This interfacial layer is critical to our understanding of a diverse set of phenomena from biology to materials science.
When the solid surface is charged just like an electrode in a working battery it can drive further changes in the interfacial liquid.
However elucidating the molecular structure at the solid-liquid interface under these conditions has proven difficult.
Miquel Salmeron a senior scientist in Berkeley Lab's Materials sciences Division (MSD) and professor in UC Berkeley's Materials science and engineering Department explains this in the context of a battery.
At an electrode surface the build up of electrical charge driven by a potential difference (or voltage) produces a strong electric field that drives molecular rearrangements in the electrolyte next to the electrode.
Berkeley Lab researchers have developed a method not only to look at the molecules next to the electrode surface
but to determine their arrangement changes depending on the voltage. With gold as a chemically inert electrode and slightly-saline water as an electrolyte Salmeron and colleagues used a new twist on x-ray absorption spectroscopy XAS) to probe the interface
and show how the interfacial molecules are arranged. XAS itself is not new. In this process a material absorbs x-ray photons at a specific rate as a function of photon energy.
A plot of the absorption intensity as a function of energy is referred to as a spectrum
which like a fingerprint is characteristic of a given material molecule and its chemical state.
The x-ray photons used in this study have energies that are about 250 times higher than those of visible light
or a tenth of a micrometer) x-ray transparent window with a thin coating of gold (20nm) on a sealed liquid sample holder the Berkeley Lab team was able to expose water molecules in the liquid to x-rays
We are interested only really in a nanoscale interfacial region and looking at the fluorescence photon signal we can't tell the difference between the interface
and the interior electrolyte molecules says Salmeron. The challenge therefore was to collect a signal that would be dominated by the interfacial region.
because electrons emitted from x-ray excited water molecules travel only nanometer distances through matter. The electrons arriving at the gold electrode surface can be detected as an electrical current traveling through a wire attached to it.
This avoids confusion with signals from the interior electrolyte because electrons emitted from interior molecules don't travel far enough to be detected.
There's an additional problem that arises when studying liquids in contact with working electrodes because they carry a steady current as in batteries and other electrochemical systems.
While the emitted electrons from nearby molecules are indeed detectable this contribution to the current is dwarfed by the normal Faradaic current of the battery at finite voltages.
When measuring current off the electrode it is critical to determine which part is due to the x-rays and
which is due to the regular battery current. To overcome this problem the researchers pulsed the incoming x-rays from the synchrotron at a known frequency.
The current contribution resulting from electron emission by interfacial molecules is pulsed thus as well and instruments can separate this nanoampere modulated current from the main Faradaic current.
These experiments result in absorption vs. x-ray energy curves (spectra) that reflect how water molecules within nanometers of the gold surface absorb the x-rays.
To translate that information into molecular structure a sophisticated theoretical analysis technique is needed. David Prendergast a staff scientist in the Molecular Foundry and researcher in the Joint Center for Energy storage Research (JCESR) has developed computational techniques that allow his team to accomplish this translation Using supercomputer facilities at Berkeley Lab
's National Energy Research Scientific Computing Center (NERSC) he conducted large molecular dynamics simulations of the gold-water interface
and then predicted the x-ray absorption spectra of representative structures from those simulations. These are first-principles calculations explains Prendergast.
We don't dictate the chemistry: we just choose what atomic elements are present and how many atoms.
That's the main thing we know about the gold electrode surface from the x-ray absorption spectra:
Water next to the electrode has a different molecular structure than it would in the absence of the electrode.
and these two layers span only about 1 nanometer. To observe any difference in the experimental spectra with varying voltage means that measurements are sensitive to a shorter length scale than was thought possible.
We had thought the sensitivity to be tens of nanometers but it turns out to be subnanometer says Prendergast.
That's spectacular! This study which is reported in Science in a paper titled The structure of interfacial water on gold electrodes studied by x-ray absorption spectroscopy marks the first time that the scientific community has shown such high sensitivity in an in-situ environment under working electrode conditions s
#NIST offers electronics industry two ways to snoop on self-organizing molecules A few short years ago,
the idea of a practical manufacturing process based on getting molecules to organize themselves in useful nanoscale shapes seemed...
well, cool, sure, but also a little fantastic. Now the day isn't far off when your cell phone may depend on it.
depositing thin films of a uniquely designed polymer on a template so that it self-assembles into neat, precise, even rows of alternating composition just 10 or so nanometers wide.
The work by researchers at the National Institute of Standards and Technology, the Massachusetts institute of technology, and IBM Almaden Research center focuses on block copolymers a special class of polymers that under the proper conditions, will segregate on a microscopic scale into regularly spaced"domains"of different chemical composition.
The two groups demonstrated ways to observe and measure the shape and dimensions of the polymer rows in three dimensions.
The experimental techniques can prove essential in verifying and tuning the computational models used to guide the fabrication process development.
It's old news that the semiconductor industry is starting to run up against physical limits to the decades-long trend of ever-denser integrated chips with smaller and smaller feature sizes,
but it hasn't reached bottom yet. Just recently, Intel Corp. announced that it had in production a new generation of chips with a 14-nanometer minimum feature size.
That's a little over five times the width of human DNA. At those dimensions, the problem is creating the multiple masking layers, sort of tiny stencils,
Hence the polymers.""The issue in semiconductor lithography is not really making small featuresou can do thatut you can't pack them close together,
"explains NIST materials scientist Alexander Liddle.""Block copolymers take advantage of the fact that if I make small features relatively far apart,
I can put the block copolymer on those guiding patterns and sort of fill in the small details."
"The strategy is called"density multiplication"and the technique,"directed self-assembly.""Block copolymers (BCPS) are a class of materials made by connecting two or more different polymers that,
as they anneal, will form predictable, repeating shapes and patterns. With the proper lithographed template,
the BCPS in question will form a thin film in a pattern of narrow, alternating stripes of the two polymer compositions.
Alternatively, they can be designed so one polymer forms a pattern of posts embedded in the other.
Remove one polymer, and in theory, you have a near-perfect pattern for lines spaced 10 to 20 nanometers apart to become, perhaps, part of a transistor array.
If it works.""The biggest problem for the industry is the patterning has to be perfect.
There can't be any defects, "says NIST materials scientist Joseph Kline.""In both of our projects we're trying to measure the full structure of the pattern.
working with IBM, demonstrated a new measurement technique*that uses low energy or"soft"X rays produced by the Advanced Light source at Lawrence Berkeley National Labs to probe the structure of the BCP film from multiple angles.
although the basic technique was developed using short wavelength"hard"X rays that have difficulty distinguishing two closely related polymers,
at individual sections of a film by doing three-dimensional tomography with a transmission electron microscope (TEM).*
***Unlike the scattering technique, the TEM tomography can actually image defects in the polymer structureut only for a small area.
The technique can image an area about 500 nanometers across. Between them, the two techniques can yield detailed data on the performance of a given BCP patterning system.
The data, the researchers say, are most valuable for testing and refining computer models.""Our measurements are both fairly time-consuming,
so they're not something industry can use on the fab floor, "says Kline.""But as they're developing the process,
they can use our measurements to get the models right, then they can do a lot of simulations
and let the computers figure it out.""""It's just so expensive and time-consuming to test out a new process,
That's a huge factor in the electronics industry. d
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