#Graphene-based film can be used for efficient cooling of electronics Researchers have developed a method for efficiently cooling electronics using graphene-based film.
The film has a thermal conductivity capacity that is four times that of copper. Moreover, the graphene film is attachable to electronic components made of silicon,
which favours the film's performance compared to typical graphene characteristics shown in previous, similar experiments.
Electronic systems available today accumulate a great deal of heat, mostly due to the ever-increasing demand on functionality.
and would also lead to a considerable reduction in energy usage. According to an American study, approximately half the energy required to run computer servers,
is used for cooling purposes alone. A couple of years ago, a research team led by Johan Liu, professor at Chalmers University of Technology, were the first to show that graphene can have a cooling effect on silicon-based electronics.
That was the starting point for researchers conducting research on the cooling of silicon-based electronics using graphene. ut the methods that have been in place so far have presented the researchers with problems Johan Liu says. t has become evident that those methods cannot be used to rid electronic devices
off great amounts of heat because they have consisted only of a few layers of thermal conductive atoms.
since the adhesion is held together only by weak Van der waals bonds.""e have solved now this problem by managing to create strong covalent bonds between the graphene film and the surface,
which is made an electronic component of silicon, he continues. The stronger bonds result from so-called functionalisation of the graphene,
i e. the addition of a property-altering molecule. Having tested several different additives, the Chalmers researchers concluded that an addition of (3-Aminopropyl) triethoxysilane (APTES) molecules has desired the most effect.
it creates so-called silane bonds between the graphene and the electronic component (see picture). Moreover, functionalisation using silane coupling doubles the thermal conductivity of the graphene.
The researchers have shown that the in-plane thermal conductivity of the graphene-based film, with 20 micrometer thickness, can reach a thermal conductivity value of 1600 W/mk,
which is four times that of copper. ncreased thermal capacity could lead to several new applications for graphene,
says Johan Liu.""One example is the integration of graphene-based film into microelectronic devices and systems,
such as highly Efficient light Emitting Diodes (LEDS), lasers and radio frequency components for cooling purposes. Graphene-based film could also pave the way for faster, smaller, more energy efficient, sustainable high power electronics."
"Image: Graphene-based film on an electronic component with high heat intensity. Credit: Johan Liu Source:
http://www. mynewsdesk. com/uk/chalmers/..
#Environmentally friendly lignin nanoparticle'greens'silver nanobullet to battle bacteria Researchers have developed an effective and environmentally benign method to combat bacteria by engineering nanoscale particles that add the antimicrobial potency of silver to a core of lignin,
a ubiquitous substance found in all plant cells. The findings introduce ideas for better, greener and safer nanotechnology and could lead to enhanced efficiency of antimicrobial products used in agriculture and personal care.
Environmentally friendly lignin nanoparticle'greens'silver nanobullet to battle bacteria In a study being published in Nature Nanotechnology July 13,
North carolina State university engineer Orlin Velev and colleagues show that silver-ion infused lignin nanoparticles, which are coated with a charged polymer layer that helps them adhere to the target microbes,
effectively kill a broad swath of bacteria, including E coli and other harmful microorganisms. As the nanoparticles wipe out the targeted bacteria,
they become depleted of silver. The remaining particles degrade easily after disposal because of their biocompatible lignin core,
limiting the risk to the environment.""People have been interested in using silver nanoparticles for antimicrobial purposes, but there are lingering concerns about their environmental impact due to the long-term effects of the used metal nanoparticles released in the environment,
"said Velev, INVISTA Professor of Chemical and Biomolecular engineering at NC State and the paper's corresponding author."
"We show here an inexpensive and environmentally responsible method to make effective antimicrobials with biomaterial cores."
"The researchers used the nanoparticles to attack E coli, a bacterium that causes food poisoning; Pseudomonas aeruginosa, a common disease-causing bacterium;
Ralstonia, a genus of bacteria containing numerous soil-borne pathogen species; and Staphylococcus epidermis, a bacterium that can cause harmful biofilms on plastics-like catheters-in the human body.
The nanoparticles were effective against all the bacteria. The method allows researchers the flexibility to change the nanoparticle recipe in order to target specific microbes.
Alexander Richter, the paper's first author and an NC State Ph d. candidate who won a 2015 Lemelson-MIT prize,
says that the particles could be the basis for reduced risk pesticide products with reduced cost and minimized environmental impact."
"We expect this method to have a broad impact, "Richter said.""We may include less of the antimicrobial ingredient without losing effectiveness
while at the same time using an inexpensive technique that has a lower environmental burden. We are now working to scale up the process to synthesize the particles under continuous flow conditions
#Environmentally friendly lignin nanoparticle'greens'silver nanobullet to battle bacteria Researchers have developed an effective and environmentally benign method to combat bacteria by engineering nanoscale particles that add the antimicrobial potency of silver to a core of lignin,
a ubiquitous substance found in all plant cells. The findings introduce ideas for better, greener and safer nanotechnology and could lead to enhanced efficiency of antimicrobial products used in agriculture and personal care.
In a study being published in Nature Nanotechnology July 13, North carolina State university engineer Orlin Velev and colleagues show that silver-ion infused lignin nanoparticles,
which are coated with a charged polymer layer that helps them adhere to the target microbes,
effectively kill a broad swath of bacteria, including E coli and other harmful microorganisms. As the nanoparticles wipe out the targeted bacteria,
they become depleted of silver. The remaining particles degrade easily after disposal because of their biocompatible lignin core,
limiting the risk to the environment.""People have been interested in using silver nanoparticles for antimicrobial purposes, but there are lingering concerns about their environmental impact due to the long-term effects of the used metal nanoparticles released in the environment,
"said Velev, INVISTA Professor of Chemical and Biomolecular engineering at NC State and the paper's corresponding author."
"We show here an inexpensive and environmentally responsible method to make effective antimicrobials with biomaterial cores."
"The researchers used the nanoparticles to attack E coli, a bacterium that causes food poisoning; Pseudomonas aeruginosa, a common disease-causing bacterium;
Ralstonia, a genus of bacteria containing numerous soil-borne pathogen species; and Staphylococcus epidermis, a bacterium that can cause harmful biofilms on plastics-like catheters-in the human body.
The nanoparticles were effective against all the bacteria. The method allows researchers the flexibility to change the nanoparticle recipe in order to target specific microbes.
Alexander Richter, the paper's first author and an NC State Ph d. candidate who won a 2015 Lemelson-MIT prize,
says that the particles could be the basis for reduced risk pesticide products with reduced cost and minimized environmental impact."
"We expect this method to have a broad impact, "Richter said.""We may include less of the antimicrobial ingredient without losing effectiveness
while at the same time using an inexpensive technique that has a lower environmental burden. We are now working to scale up the process to synthesize the particles under continuous flow conditions."
"Source: https://news. ncsu. edu
#Imaging lipid rafts reveals some surprises In a previous collaboration, a team of researchers led by Mikiko Sodeoka at the RIKEN Synthetic Organic chemistry Laboratory
and Katsumasa Fujita at Osaka University developed a way to image small, mobile bioactive molecules in living cells,
with the potential to greatly enhance our understanding of cellular processes. The method involves tagging bioactive molecules with small alkyne molecules
and then imaging them using Raman microscopy technique that detects the vibrations of molecules by exciting them using a microscope-focused laser beam.
Unlike the comparatively large fluorescent tags used in conventional approaches the alkyne tags used in Sodeoka method do not alter the physical properties of bioactive molecules
or impede their motion in cells. One of Sodeoka collaborators, Michio Murata at Osaka University, suggested applying the technique to lipid raftsmall domains in cell membranes that are rich in lipids such as cholesterol
and sphingomyelin and that play important roles in membrane signaling and protein trafficking. urata told us it would be a real breakthrough
if we could eethe distribution of sphingomyelin in the raft structure, Sodeoka says. But this required overcoming two major challenges.
Because lipid rafts are constantly moving in the cell membrane it is very difficult to pin them down long enough to obtain an image.
Furthermore, the low number of lipid rafts in membranes makes it hard to extract their signals from the background noise.
The researchers overcame both challenges by drawing on the strengths of their respective teams. Murata group made long imaging times possible by preparing artificial membranes with a raft-like composition and immobilizing them on a surface,
while Sodeoka and Fujita groups obtained strong signals from lipid rafts by employing a small, strongly Raman-active conjugated diyne tag and their highly sensitive Raman microscope.
The technique developed by the team opens the way for in depth functional studies of lipid rafts. efore our work,
minimally invasive device for controlling brain cells with drugs and lighta study showed that scientists can wirelessly determine the path a mouse walks with a press of a button.
Researchers at the Washington University School of medicine, St louis, and University of Illinois, Urbana-Champaign, created a remote controlled,
next-generation tissue implant that allows neuroscientists to inject drugs and shine lights on neurons deep inside the brains of mice.
"said Michael R. Bruchas, Ph d.,associate professor of anesthesiology and neurobiology at Washington University School of medicine and a senior author of the study.
The Bruchas lab studies circuits that control a variety of disorders including stress, depression, addiction, and pain.
Typically, scientists who study these circuits have to choose between injecting drugs through bulky metal tubes
Both options require surgery that can damage parts of the brain and introduce experimental conditions that hinder animals'natural movements.
To address these issues, Jae-Woong Jeong, Ph d.,a bioengineer formerly at the University of Illinois at Urbana-Champaign
worked with Jordan G. Mccall, Ph d.,a graduate student in the Bruchas lab, to construct a remote controlled, optofluidic implant.
The device is made out of soft materials that are a tenth the diameter of a human hair
"We used powerful nanomanufacturing strategies to fabricate an implant that lets us penetrate deep inside the brain with minimal damage,
"said John A. Rogers, Ph d.,professor of materials science and engineering, University of Illinois at Urbana-Champaign and a senior author."
"Ultra-miniaturized devices like this have tremendous potential for science and medicine.""With a thickness of 80 micrometers and a width of 500 micrometers, the optofluidic implant is thinner than the metal tubes,
When the scientists compared the implant with a typical cannula they found that the implant damaged
In some experiments, they showed that they could precisely map circuits by using the implant to inject viruses that label cells with genetic dyes.
when they made mice that have light-sensitive VTA neurons stay on one side of a cage by commanding the implant to shine laser pulses on the cells.
In all of the experiments, the mice were about three feet away from the command antenna."
"The researchers fabricated the implant using semiconductor computer chip manufacturing techniques. It has room for up to four drugs
and has four microscale inorganic light-emitting diodes. They installed an expandable material at the bottom of the drug reservoirs to control delivery.
who is now an assistant professor of electrical, computer, and energy engineering at University of Colorado Boulder."
"We tried to engineer the implant to meet some of neurosciences greatest unmet needs.""In the study, the scientists provide detailed instructions for manufacturing the implant."
"A tool is only good if it's used, "said Dr. Bruchas.""We believe an open,
crowdsourcing approach to neuroscience is a great way to understand normal and healthy brain circuitry."
Courtesy of Jeong lab, University of Colorado Boulder. Source: http://www. ninds. nih. gov
#Superfast fluorescence sets new speed record Researchers have developed an ultrafast light-emitting device that can flip on and off 90 billion times a second
At its most basic level, your smart phone's battery is powering billions of transistors using electrons to flip on and off billions of times per second.
But if microchips could use photons instead of electrons to process and transmit data, computers could operate even faster.
But first engineers must build a light source that can be turned on and off that rapidly.
While lasers can fit this requirement they are too energy-hungry and unwieldy to integrate into computer chips.
Duke university researchers are now one step closer to such a light source. In a new study, a team from the Pratt School of engineering pushed semiconductor quantum dots to emit light at more than 90 billion gigahertz.
This so-called plasmonic device could one day be used in optical computing chips or for optical communication between traditional electronic microchips.
The study was published online on July 27 in Nature Communications. his is something that the scientific community has wanted to do for a long time
an assistant professor of electrical and computer engineering and physics at Duke. e can now start to think about making fast-switching devices based on this research, so there a lot of excitement about this demonstration.
When a laser shines on the surface of a silver cube just 75 nanometers wide,
Energy trapped on the surface of the nanocube in this fashion is called a plasmon. The plasmon creates an intense electromagnetic field between the silver nanocube
and a thin sheet of gold placed a mere 20 atoms away. This field interacts with quantum dotspheres of semiconducting material just six nanometers widehat are sandwiched in between the nanocube and the gold.
The quantum dots, in turn, produce a directional, efficient emission of photons that can be turned on and off at more than 90 gigahertz. here is great interest in replacing lasers with LEDS for short-distance optical communication,
but these ideas have always been limited by the slow emission rate of fluorescent materials, lack of efficiency and inability to direct the photons,
said Gleb Akselrod, a postdoctoral research in Mikkelsen laboratory. ow we have made an important step towards solving these problems. he eventual goal is to integrate our technology into a device that can be excited either optically
including funding agencies, is pushing pretty hard for. The group is now working to use the plasmonic structure to create a single photon source necessity for extremely secure quantum communicationsy sandwiching a single quantum dot in the gap between the silver nanocube and gold foil.
They are also trying to precisely place and orient the quantum dots to create the fastest fluorescence rates possible.
Aside from its potential technological impacts, the research demonstrates that well-known materials need not be limited by their intrinsic properties. y tailoring the environment around a material
like wee done here with semiconductors, we can create new designer materials with almost any optical properties we desire,
said Mikkelsen. nd that an emerging area that fascinating to think about. i
#Superfast fluorescence sets new speed record Researchers have developed an ultrafast light-emitting device that can flip on and off 90 billion times a second
At its most basic level, your smart phone's battery is powering billions of transistors using electrons to flip on and off billions of times per second.
But if microchips could use photons instead of electrons to process and transmit data, computers could operate even faster.
But first engineers must build a light source that can be turned on and off that rapidly.
While lasers can fit this requirement they are too energy-hungry and unwieldy to integrate into computer chips.
Duke university researchers are now one step closer to such a light source. In a new study, a team from the Pratt School of engineering pushed semiconductor quantum dots to emit light at more than 90 billion gigahertz.
This so-called plasmonic device could one day be used in optical computing chips or for optical communication between traditional electronic microchips.
The study was published online on July 27 in Nature Communications. his is something that the scientific community has wanted to do for a long time
an assistant professor of electrical and computer engineering and physics at Duke. e can now start to think about making fast-switching devices based on this research,
When a laser shines on the surface of a silver cube just 75 nanometers wide,
Energy trapped on the surface of the nanocube in this fashion is called a plasmon. The plasmon creates an intense electromagnetic field between the silver nanocube
and a thin sheet of gold placed a mere 20 atoms away. This field interacts with quantum dotspheres of semiconducting material just six nanometers widehat are sandwiched in between the nanocube and the gold.
The quantum dots, in turn, produce a directional, efficient emission of photons that can be turned on and off at more than 90 gigahertz. here is great interest in replacing lasers with LEDS for short-distance optical communication,
but these ideas have always been limited by the slow emission rate of fluorescent materials, lack of efficiency and inability to direct the photons,
said Gleb Akselrod, a postdoctoral research in Mikkelsen laboratory. ow we have made an important step towards solving these problems.?
including funding agencies, is pushing pretty hard for. he group is now working to use the plasmonic structure to create a single photon source necessity for extremely secure quantum communicationsy sandwiching a single quantum dot in the gap between the silver nanocube and gold foil.
They are also trying to precisely place and orient the quantum dots to create the fastest fluorescence rates possible.
Aside from its potential technological impacts the research demonstrates that well-known materials need not be limited by their intrinsic properties. y tailoring the environment around a material,
like wee done here with semiconductors, we can create new designer materials with almost any optical properties we desire,
said Mikkelsen. nd that an emerging area that fascinating to think about
#Reshaping the solar spectrum to turn light to electricity Researchers find a way to use the infrared region of the sun's spectrum to make solar cells more efficient.
When it comes to installing solar cells, labor cost and the cost of the land to house them constitute the bulk of the expense.
The solar cells made often of silicon or cadmium telluride rarely cost more than 20 percent of the total cost.
Solar energy could be made cheaper if less land had to be purchased to accommodate solar panels, best achieved if each solar cell could be coaxed to generate more power.
A huge gain in this direction has now been made by a team of chemists at the University of California
Riverside that has found an ingenious way to make solar energy conversion more efficient. The researchers report in Nano Letters that by combining inorganic semiconductor nanocrystals with organic molecules, they have succeeded in pconvertingphotons in the visible and near-infrared regions of the solar spectrum. he infrared region of the solar
spectrum passes right through the photovoltaic materials that make up today solar cells, explained Christopher Bardeen, a professor of chemistry.
The research was a collaborative effort between him and Ming Lee Tang, an assistant professor of chemistry. his is lost energy, no matter how good your solar cell.
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. ardeen added that these materials are essentially eshaping the solar spectrumso that it better matches the photovoltaic materials used today in solar cells.
The ability to utilize the infrared portion of the solar spectrum could boost solar photovoltaic efficiencies by 30 percent or more.
In their experiments, Bardeen and Tang worked with cadmium selenide and lead selenide semiconductor nanocrystals.
The organic compounds they used to prepare the hybrids were diphenylanthracene and rubrene. 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,
providing a route to higher efficiencies. his 550-nanometer light can be absorbed by any solar cell material,
Bardeen said. he key to this research is the hybrid composite material combining inorganic semiconductor nanoparticles with organic compounds.
Organic compounds cannot absorb in the infrared 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;
the organics get light out. esides 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.
Bardeen emphasized that the research could have wide-ranging implications. he ability to move light energy from one wavelength to another, more useful region, for example,
from red to blue, can impact any technology that involves photons as inputs or outputs,
he said. Image: Photographs of upconversion in a cuvette containing (a) an optimized cadmium selenide/9-ACA/DPA and (b) a cadmium selenide/ODPA/DPA mixture.
9-ACA: 9-anthracenecarboxylic acid; ODPA: octadecylphosphonic acid; and DPA: 9, 10-diphenylanthracene. They were excited with a focused continuous wave 532-nm laser.
The violet DPA output in (a) swamps the green beam that is clearly seen in (b),
where no upconversion takes place. This indicates the enhancement of the upconverted fluorescence by the 9-ACA ligand e
#Reshaping the solar spectrum to turn light to electricity Researchers find a way to use the infrared region of the sun's spectrum to make solar cells more efficient.
When it comes to installing solar cells, labor cost and the cost of the land to house them constitute the bulk of the expense.
The solar cells made often of silicon or cadmium telluride rarely cost more than 20 percent of the total cost.
Solar energy could be made cheaper if less land had to be purchased to accommodate solar panels, best achieved if each solar cell could be coaxed to generate more power.
A huge gain in this direction has now been made by a team of chemists at the University of California
Riverside that has found an ingenious way to make solar energy conversion more efficient. The researchers report in Nano Letters that by combining inorganic semiconductor nanocrystals with organic molecules, they have succeeded in pconvertingphotons in the visible and near-infrared regions of the solar spectrum. he infrared region of the solar
spectrum passes right through the photovoltaic materials that make up today solar cells, explained Christopher Bardeen, a professor of chemistry.
The research was a collaborative effort between him and Ming Lee Tang, an assistant professor of chemistry. his is lost energy, no matter how good your solar cell.
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. ardeen added that these materials are essentially eshaping the solar spectrumso that it better matches the photovoltaic materials used today in solar cells.
The ability to utilize the infrared portion of the solar spectrum could boost solar photovoltaic efficiencies by 30 percent or more.
In their experiments, Bardeen and Tang worked with cadmium selenide and lead selenide semiconductor nanocrystals.
The organic compounds they used to prepare the hybrids were diphenylanthracene and rubrene. 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,
providing a route to higher efficiencies. his 550-nanometer light can be absorbed by any solar cell material,
Bardeen said. he key to this research is the hybrid composite material combining inorganic semiconductor nanoparticles with organic compounds.
Organic compounds cannot absorb in the infrared 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;
the organics get light out. esides 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.
Bardeen emphasized that the research could have wide-ranging implications. he ability to move light energy from one wavelength to another, more useful region, for example,
from red to blue, can impact any technology that involves photons as inputs or outputs,
he said t
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