Solar-to-Fuel System Recycles CO2 to Make Ethanol and Ethylene: Berkeley National Lab



Schematic of a solar-powered electrolysis cell which converts carbon dioxide into hydrocarbon and oxygenate products with an efficiency far higher than natural photosynthesis. Power-matching electronics allow the system to operate over a range of sun conditions. (Credit: Clarissa Towle/Berkeley Lab)

Berkeley Lab advance is first demonstration of efficient, light-powered production of fuel via artificial photosynthesis

Scientists at the Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) have harnessed the power of photosynthesis to convert carbon dioxide into fuels and alcohols at efficiencies far greater than plants. The achievement marks a significant milestone in the effort to move toward sustainable sources of fuel.

Many systems have successfully reduced carbon dioxide to chemical and fuel precursors, such as carbon monoxide or a mix of carbon monoxide and hydrogen known as syngas. This new work, described in a study published in the journal Energy and Environmental Science, is the first to successfully demonstrate the approach of going from carbon dioxide directly to target products, namely ethanol and ethylene, at energy conversion efficiencies rivaling natural counterparts.

The researchers did this by optimizing each component of a photovoltaic-electrochemical system to reduce voltage loss, and creating new materials when existing ones did not suffice.

“This is an exciting development,” said study principal investigator Joel Ager, a Berkeley Lab scientist with joint appointments in the Materials Sciences and the Chemical Sciences divisions. “As rising atmospheric CO2 levels change Earth’s climate, the need to develop sustainable sources of power has become increasingly urgent. Our work here shows that we have a plausible path to making fuels directly from sunlight.”

That sun-to-fuel path is among the key goals of the Joint Center for Artificial Photosynthesis (JCAP), a DOE Energy Innovation Hub established in 2010 to advance solar fuel research. The study was conducted at JCAP’s Berkeley Lab campus.

The initial focus of JCAP research was tackling the efficient splitting of water in the photosynthesis process. Having largely achieved that task using several types of devices, JCAP scientists doing solar-driven carbon dioxide reduction began setting their sights on achieving efficiencies similar to those demonstrated for water splitting, considered by many to be the next big challenge in artificial photosynthesis.

Another research group at Berkeley Lab is tackling this challenge by focusing on a specific component in a photovoltaic-electrochemical system. In a study published today, they describe a new catalyst that can achieve carbon dioxide to multicarbon conversion using record-low inputs of energy.

Not just for noon


For this JCAP study, researchers engineered a complete system to work at different times of day, not just at a light energy level of 1-sun illumination, which is equivalent to the peak of brightness at high noon on a sunny day. They varied the brightness of the light source to show that the system remained efficient even in low light conditions.

When the researchers coupled the electrodes to silicon photovoltaic cells, they achieved solar conversion efficiencies of 3 to 4 percent for 0.35 to 1-sun illumination. Changing the configuration to a high-performance, tandem solar cell connected in tandem yielded a conversion efficiency to hydrocarbons and oxygenates exceeding 5 percent at 1-sun illumination.

Copper-Silver Cathode

At left is a surface view of a bimetallic copper-silver nanocoral cathode taken from a scanning electron micrograph. To the right is an energy-dispersive X-ray image of the cathode with the copper (in pink/red) and silver (in green) highlighted. (Credit: Gurudayal/Berkeley Lab)

“We did a little dance in the lab when we reached 5 percent,” said Ager, who also holds an appointment as an adjunct professor at UC Berkeley’s Materials Science and Engineering Department.

Among the new components developed by the researchers are a copper-silver nanocoral cathode, which reduces the carbon dioxide to hydrocarbons and oxygenates, and an iridium oxide nanotube anode, which oxidizes the water and creates oxygen.

“The nice feature of the nanocoral is that, like plants, it can make the target products over a wide range of conditions, and it is very stable,” said Ager.

The researchers characterized the materials at the National Center for Electron Microscopy at the Molecular Foundry, a DOE Office of Science User Facility at Berkeley Lab. The results helped them understand how the metals functioned in the bimetallic cathode. Specifically, they learned that silver aids in the reduction of carbon dioxide to carbon monoxide, while the copper picks up from there to reduce carbon monoxide further to hydrocarbons and alcohols.

Seeking better, low-energy breakups



Because carbon dioxide is a stubbornly stable molecule, breaking it up typically involves a significant input of energy.
“Reducing CO2 to a hydrocarbon end product like ethanol or ethylene can take up to 5 volts, start to finish,” said study lead author Gurudayal, postdoctoral fellow at Berkeley Lab. “Our system reduced that by half while maintaining the selectivity of products.”

Notably, the electrodes operated well in water, a neutral pH environment.

“Research groups working on anodes mostly do so using alkaline conditions since anodes typically require a high pH environment, which is not ideal for the solubility of CO2,” said Gurudayal. “It is very difficult to find an anode that works in neutral conditions.”

The researchers customized the anode by growing the iridium oxide nanotubes on a zinc oxide surface to create a more uniform surface area to better support chemical reactions.

“By working through each step so carefully, these researchers demonstrated a level of performance and efficiency that people did not think was possible at this point,” said Berkeley Lab chemist Frances Houle, JCAP deputy director for Science and Research Integration, who was not part of the study. “This is a big step forward in the design of devices for efficient CO2 reduction and testing of new materials, and it provides a clear framework for the future advancement of fully integrated solar-driven CO2-reduction devices.”

Other co-authors on the study include James Bullock, a Berkeley Lab postdoctoral researcher in materials sciences, who was instrumental in engineering the system’s photovoltaic and electrolysis cell pairing. Bullock works in the lab of study co-author Ali Javey, Berkeley Lab senior faculty scientist and a UC Berkeley professor of electrical engineering and computer sciences.

This work is supported by the DOE Office of Science.

Lawrence Berkeley National Laboratory addresses the world’s most urgent scientific challenges by advancing sustainable energy, protecting human health, creating new materials, and revealing the origin and fate of the universe. Founded in 1931, Berkeley Lab’s scientific expertise has been recognized with 13 Nobel Prizes. 
The University of California manages Berkeley Lab for the U.S. Department of Energy’s Office of Science. For more, visit http://www.lbl.gov.
DOE’s Office of Science is the single largest supporter of basic research in the physical sciences in the United States, and is working to address some of the most pressing challenges of our time. For more information, please visit science.energy.gov.

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Ionic Industries announces a process for economically mass-producing graphene micro supercapacitors



Ionic Industries recently announced a process for economically mass-producing graphene micro supercapacitors and added that its directors and key personnel have taken direct stakes in the company.

Ionic Industries’ graphene supercapacitors patent image




Ionic stated that since it published the positive results on its graphene micro planar supercapacitors 2 years before, the company has been working toward developing a device that not only demonstrates similar performance but can be produced at scale to deliver an economically viable device.

The last 2 years of work reportedly culminated in the filing of a new patent titled: Capacitive energy storage device and method of producing same (Australian Provisional Patent Application 2017903619). 

The new patent covers: the design of new energy storage device, being a planar micro supercapacitor printed on a porous film; Ionic’s technique of stacking multiple layers of planar supercapacitors to create a 3D device that has ground-breaking energy and power density characteristics; and, most importantly, the company’s method for printing these devices so that they can be mass produced at low cost.

The critical element in this new technology is the ability to print the supercapacitors in the 1000s per minute, rather than individually creating each device with an expensive, direct-write approaches using lasers or ion beams. The technology builds on Ionic’s existing patent relating to graphene oxide membranes and it means the company could create these devices as easily as factories today produce food packaging and labels using gravure printers.

The team is now working on assembling the prototype device which is scheduled for completion in the next 6 weeks before it go into trials for a period of several months. 
The expected end result is a supercapacitor energy storage device comprised of printed graphene micro planar supercapacitors that can be produced economically at scale.

Ionic stated that it is extremely excited about this development as it brings it well within sight of a commercial product. The next steps involve identifying appropriate, world leading partners with whom Ionic can introduce this technology into products such as medical devices, wearable technologies, IoT devices or remote sensing applications.

Nanotechnology delivers medicine to cancer cells while protecting healthy cells ~ “Fooling Cancer”



Cancer treatments, including chemotherapy, have helped many of those who have been diagnosed with the disease to go on to live healthy lives.

Nevertheless, chemotherapy takes a toll on the body. During treatment, chemotherapy attacks all of the body’s cells, not just cancer cells. The result destroys healthy cells, causing many patients to suffer major side effects during and after treatment.

And because current treatments aren’t specifically targeted to cancer cells, only 0.01 percent of chemotherapy drugs actually reach the tumor and its diseased cells.

“I’m working on figuring out how we can deliver more of the chemotherapy drugs to the tumor and less to healthy cells,” says Sofie Snipstad, who recently graduated from the Department of Physics at the Norwegian University of Science and Technology (NTNU). Last year, she won a Norwegian science communication competition for PhD candidates called Researcher Grand Prix. When she made her winning presentation about her research during the competition finals, she was in the middle of testing a new method of cancer treatment on mice.

Now her research has shown that the method can cure cancer in mice.

Her study has just been published in the academic journal Ultrasound in Medicine and Biology (“Ultrasound Improves the Delivery and Therapeutic Effect of Nanoparticle-Stabilized Microbubbles in Breast Cancer Xenografts”).


Blood vessels supplying the cancer cells (kreftceller in the illustration) have porous walls, while the sections of blood vessels passing through healthy cells are not porous. This protects healthy cells from the chemotherapy. (Image: NTNU)

Promising results

Snipstad’s method targets cancerous tumors with chemotherapy so that more of the drug reaches cancer cells while protecting healthy cells. The experiments were conducted in mice with an aggressive breast cancer type (triple negative).

Researchers undertook many laboratory experiments before conducting their tests with mice — which were the first actual tests using this delivery method for chemotherapy. In addition to causing the tumors to disappear during treatment, the cancer has not returned in the trial animals.

“This is an exciting technology that has shown very promising results. That the first results from our tests in mice are so good, and that the medicine does such a good job right from the start is very promising,” Snipstad says.

Here’s how the treatment works

Instead of being injected straight into the bloodstream and transported randomly to both sick and healthy cells, the chemotherapy medicine is encapsulated in nanoparticles. When nanoparticles containing the cancer drugs are injected into the bloodstream, the nanoparticles are so large that they remain in the blood vessels in most types of healthy tissues. This prevents the chemotherapy from harming healthy cells.

Blood vessels in the tumor, however, have porous walls, so that the nanoparticles containing the chemotherapy can work their way into the cancerous cells.

“My research shows that this method allows us to supply 100 times more chemotherapy to the tumor compared to chemotherapy alone. That’s good,” Snipstad says.

However, the nanoparticles can only reach cells that are closest to the blood vessels that carry the drug-laden particles, she said. That means that cancer cells that are far from the blood vessels that supply the tumour do not get the chemotherapy drugs.

“For the treatment to be effective, it has to reach all parts of the tumor. So our nanoparticles need help to deliver the medicine,” she said.

Ultrasound is the key

The nanoparticles used by Snipstad and her research team were developed at SINTEF in Trondheim. SINTEF is one of Europe’s largest independent research organizations. The particles are unusual because they can form small bubbles. The nanoparticles are in the surface of the bubbles.

These bubbles are an important part of the cancer treatment. Another essential part is the use of ultrasound, which is Snipstad’s area of research.

nanobubbles in ultrasound treatments

To make the bubbles behave the way they wanted, the researchers tested many different ultrasound treatments, and measured how many of the nanoparticles were delivered to cancerous tissues in mice. Many of the ultrasound treatments had little effect, but Sofie Snipstad found one that worked quite well. (Image: NTNU)

The bubbles that contain the chemotherapy-laden nanoparticles are injected into the bloodstream. Ultrasound is then applied to the tumor. The ultrasound causes the bubbles to vibrate and eventually burst, so that the nanoparticles are released. The vibrations also massage the blood vessels and tissues to make them more porous. 

This helps push the nanoparticles further into the cancerous tumor, instead of only reaching the cancer cells closest to the blood vessels.

“By using ultrasound to transport the chemotherapy-laden nanoparticles into the tumors, our research on mice has shown that we can deliver about 250 times more of the drug to the tumor compared to just injecting chemotherapy into the bloodstream alone,” she says.

Three groups, three clear results

The mice were divided into three groups:

Group 1 received no treatment, and the tumor continued to grow.

Group 2 received the treatment using drug-laden nanoparticles. The growth of the tumor stagnated after time, but the tumour did not disappear.

Group 3 received the treatment using drug-laden nanoparticles, bubbles and ultrasound. In this group, the tumor shrank until it disappeared. One hundred days after the treatment was discontinued, the mice were still cancer-free.

Fooling cancer cells

“For the treatment to be effective, we have to trick the cancer cells to take up the nanoparticles so that the chemotherapy reaches its target,” Snipstad says.

To study this process, she has grown cancer cells and examined them under a microscope. Here, she has seen that the nanoparticles camouflage the chemotherapy drug, allowing the cancer cells to take them up. But for the treatment to work, the nanoparticles have to release the cancer drug exactly when and where it is needed.

“We can do that by changing the chemical composition of the nanoparticles so that we can tailor properties, including determining how quickly the nanoparticles break down. After the cell takes up the nanoparticle, the nanoparticle dissolves and releases the cancer drug inside the cell. That causes the cancer cell to stop dividing, and it will eventually shrink and die.

Close interdisciplinary cooperation

NTNU physics professor Catharina Davies heads the research group of which Snipstad is part. The group mainly works with nanoparticles.

The NTNU group works closely with SINTEF and St. Olavs Hospital in Trondheim. NTNU conducts the animal tests and studies the cancer cells. SINTEF has developed the bubbles containing nanoparticles, which provides the research platform. The cancer clinic and ultrasound group at St. Olavs contribute with their clinical skills.

“One of the things that I like about this project is that so many good people with different backgrounds are involved. Trondheim has a very good interdisciplinary environment, and this project needs all of these different disciplines for us to make progress,” Snipstad said.

No human trials anytime soon

While research results are very promising, it will still be some time before the method can be used in humans.

“It can take from 10-20 years from the time a discovery is made in the lab until it can be used as a treatment,” Snipstad said. “We’ve been working on this about six years, so we still have a lot to learn. 
We need to understand more about the mechanisms behind our success and we have to do much more work using microscopes to understand what is happening inside the tissues.”

Snipstad said that the find also has researchers excited to test the method on other types of cancers, because each type of cancer is different.

Possible treatment for brain cancer

This combination of bubbles, nanoparticles and ultrasound also opens the door on the possibility of treating brain diseases. The brain is protected by a special blood-brain barrier, which makes it difficult to deliver drugs to the brain for treatment. This barrier allows only substances that the brain needs to pass through the barrier, which means that for many brain diseases, there is no treatment whatsoever.

“But there is hope. By using ultrasound and our bubbles we have managed to deliver nanoparticles and drugs to the brain. This may be promising for the treatment of cancer and other diseases in the brain,” Snipstad said.

Source: Norwegian University of Science and Technology

Thanks 

The Design of Future Nano-Electronic  Circuits – Free Flowing Electrons in Graphene 



Electrons flowing like liquid in graphene start a new wave of physics – University of Manchester 

A new understanding of the physics of conductive materials has been uncovered by scientists observing the unusual movement of electrons in graphene.

Graphene is many times more conductive than copper thanks, in part, to its two-dimensional structure. In most metals, conductivity is limited by crystal imperfections which cause electrons to frequently scatter like billiard balls when they move through the material.


Now, observations in experiments at the National Graphene Institute have provided essential understanding as to the peculiar behaviour of electron flows in graphene, which need to be considered in the design of future nanoelectronic circuits.

In some high-quality materials, like graphene, electrons can travel micron distances without scattering, improving the conductivity by orders of magnitude. This so-called ballistic regime, imposes the maximum possible conductance for any normal metal, which is defined by the Landauer-Buttiker formalism.

Appearing today in Nature Physics (“Superballistic flow of viscous electron fluid through graphene constrictions”), researchers at The University of Manchester, in collaboration with theoretical physicists led by Professor Marco Polini and Professor Leonid Levitov, show that Landauer’s fundamental limit can be breached in graphene. Even more fascinating is the mechanism responsible for this.

Last year, a new field in solid-state physics termed ‘electron hydrodynamics’ generated huge scientific interest. Three different experiments, including one performed by The University of Manchester, demonstrated that at certain temperatures, electrons collide with each other so frequently they start to flow collectively like a viscous fluid.

The new research demonstrates that this viscous fluid is even more conductive than ballistic electrons. 

The result is rather counter-intuitive, since typically scattering events act to lower the conductivity of a material, because they inhibit movement within the crystal. However, when electrons collide with each other, they start working together and ease current flow.

This happens because some electrons remain near the crystal edges, where momentum dissipation is highest, and move rather slowly. At the same time, they protect neighbouring electrons from colliding with those regions. Consequently, some electrons become super-ballistic as they are guided through the channel by their friends.

Sir Andre Geim said: “We know from school that additional disorder always creates extra electrical resistance. In our case, disorder induced by electron scattering actually reduces rather than increase resistance. This is unique and quite counterintuitive: Electrons when make up a liquid start propagating faster than if they were free, like in vacuum”.

The researchers measured the resistance of graphene constrictions, and found it decreases upon increasing temperature, in contrast to the usual metallic behaviour expected for doped graphene.

By studying how the resistance across the constrictions changes with temperature, the scientists revealed a new physical quantity which they called the viscous conductance. The measurements allowed them to determine electron viscosity to such a high precision that the extracted values showed remarkable quantitative agreement with theory.


Source: University of Manchester

Army COE Creates New Energy Efficient ‘Graphene Oxide’ Water Filter at Commercial Scale



The Army Corps of Engineers have successfully created a usable prototype of a new type of water filter.

The membranes are made of a mixture of chitosan, a material commonly found in shrimp shells, and a new synthetic chemical known as “graphene oxide”. Graphene oxide is a highly researched chemical worldwide.

  According to the Army Corps, one problem encountered by scientists working with graphene oxide is not being able to synthesize the material on a scale that can be put to use.

“One of the major breakthroughs that we’ve had here is that with our casting process, we’re not limited by size,” explains Luke Gurtowski, a research chemical engineer working on the membranes.


These filters have been found to effectively remove a number of different contaminants commonly found in water.

Dr. Christopher Griggs is the research scientist in charge of overseeing development of the new membranes.

Dr. Griggs told us, “Anybody who’s experienced water shortages or has been concerned about their water quality, or any type of contaminants in the water, this type of technology certainly works to address that.”

Another challenged faced by conventional water filtering methods is maintaining high energy efficiency.

“It requires a lot of energy for the net driving pressure to force the water through the membrane,” Dr. Griggs explains. “…we’re going to have to look to new materials to try to get those efficiency gains, and so graphene oxide is a very promising candidate for that.”

The Engineer Research and Development Center currently has two patents associated with the new filters and hopes to apply them for both civil and military purposes in the near future. 

Metal-free nanoparticle could expand MRI use, tumor detection



What might sound like the set-up to a joke actually has a clinical answer: Both groups can face health risks when injected with metal-containing agents sometimes needed to enhance the color contrast — and diagnostic value — of MRIs.

But a new metal-free nanoparticle developed by the University of Nebraska-Lincoln and MIT could help circumvent these health- and age-related barriers to the powerful diagnostic tool, which physicians use to investigate or confirm a broad range of medical issues.

The team’s nanoparticle contains a non-metallic molecule that enhances MRI contrast to help distinguish among bodily tissue, a task typically performed by contrast agents containing gadolinium or other metals (ACS Central Science, “Nitroxide-Based Macromolecular Contrast Agents with Unprecedented Transverse Relaxivity and Stability for Magnetic Resonance Imaging of Tumors”).

It also survived long enough to congregate around tumors in mice, suggesting the nanoparticle could help detect cancers as well as its metallic counterparts while eliminating concerns about the long-term accumulation of metal in the body.


MRIs of a mouse before (first and third rows) and 20 hours after being injected with a low dose (second row) and high dose (fourth row) of a new metal-free contrast agent developed by Nebraska and MIT. The yellow arrow indicates the location of a tumor. (click on image to enlarge)

Contrast in styles

The molecules residing in the team’s nanoparticle belong to a family known as the nitroxides, which are among the most promising alternatives to the metallic agents often injected into patients prior to undergoing MRIs.

But antioxidants in the body typically begin breaking down nitroxides within minutes, limiting how long they can enhance the contrast of an MRI. And the team’s molecule of interest — a so-called organic radical — has just a single electron, a fact that normally inhibits how much contrast it can produce.

Gadolinium and other metals possess multiple electrons that help them influence how the magnetic waves produced by an MRI interact with water molecules in tissue. This magnetic influence, or relaxivity, ultimately dictates the strength of contrast signals that get converted into the familiar multicolored MRIs.

So Nebraska chemist Andrzej Rajca began collaborating with colleagues at MIT to design a metal-free nanoparticle that would exhibit stability and relaxivity comparable to gadolinium’s. Rajca previously designed a nitroxide that, when embedded within relatively small nanoparticles, displayed a relaxivity several times greater than its predecessors.

This time around, MIT researchers incorporated Rajca’s nitroxide into a large nanoparticle known as a brush-arm star polymer. The process involved assembling polymers into a spherical structure with a water-attracting core and water-repelling shell, then squeezing multitudes of nitroxide molecules between that core and shell.

The team found that packing so many nitroxides into such tight quarters effectively multiplied their individual relaxivity values, resulting in a nanoparticle with a relaxivity about 40 times higher than a typical nitroxide.

“You don’t need much of the (new) contrast agent to see a good image,” said Rajca, Charles Bessey Professor of chemistry.

The nanoparticle’s polymer shell also helped slow the advance of the disruptive antioxidants enough to prolong the nitroxides’ lifespan from roughly two hours to 20. By injecting mice with their agent, the researchers showed that the nanoparticle’s longevity and large size allow it to reach tumors and differentiate them from normal tissue. Even in doses larger than those typically needed for MRIs, the team’s contrast agent showed no signs of toxicity in human cells or mice.

Source: University of Nebraska-Lincoln

Harnessing the Functionality and ‘Power’ of Perovskites for Better Solar and LED’s



Originally a mineral, the perovskite used in today’s technology is quite different from the rock found in the Earth mantle. 

A “perovskite structure” uses a different combination of atoms but keep the general 3-dimensional structure originally observed in the mineral, which possesses superb optoelectronic properties such as strong light absorption and facilitated charge transport. These advantages qualify the perovskite structure as particularly suited for the design of electronic devices, from solar cells to lights.

The accelerating progress in perovskite technology over the past few years suggest new perovskite-based devices will soon outperform current technology in the energy sector. 

The Energy Materials and Surface Sciences Unit at OIST led by Prof. Yabing Qi is at the forefront of this development, with now two new scientific publications focusing on the improvement of perovskite solar cells and a cheaper and smarter way to produce emerging perovskite-based LED lights.

An extra layer in a solar cell “sandwich”

Perovskite-based solar cells is a rising technology forecast to replace the classic photovoltaic cells currently dominating the industry. 




In just seven years of development, the efficiency of perovskite solar cells increased to almost rival – and is expected to soon overtake – commercial photovoltaic cells, but the perovskite structure still plagued by a short lifespan due to stability issues. 


OIST
scientists have made constant baby steps in improving the cells stability, identifying the degradations factors and providing solutions towards better solar cell architecture.

The new finding, reported in the Journal of Physical Chemistry B (“Engineering Interface Structure to Improve Efficiency and Stability of Organometal Halide Perovskite Solar Cells”), suggests interactions between components of the solar cell itself are responsible for the rapid degradation of the device. 

More precisely, the titanium oxide layer extracting electrons made available through solar energy – effectively creating an electric current – causes unwanted deterioration of the neighboring perovskite layer. 

Imagine the solar cell as a multi-layered club sandwich: if not properly assembled, fresh and juicy vegetables in contact with the bread slices will make the bread very soggy in a matter of hours. 

But if you add a layer of ham or turkey between the vegetables and the bread, then your sandwich stays crisp all day in the lunchroom refrigerator.


A perovskite-based layer includes many layers, including for example the electrodes on both sides, and the perovskite in the middle. The addition of a polystyrene layer in-between prevents the titanium oxide layer to deteriorate the perovskite, but does not affect the overall power conversion efficiency. (© American Chemical Society)

This is exactly what the OIST researchers achieved: they inserted in the solar cell an additional layer made from a polymer to prevent direct contact between the titanium oxide and the perovskite layers. 
This polymer layer is insulating but very thin, which means it lets the electron current tunnel through yet does not diminish the overall efficiency of the solar cell, while efficiently protecting the perovskite structure.

“We added a very thin sheet, only a few nanometers wide, of polystyrene between the perovskite layer and the titanium oxide layer,” explained Dr. Longbin Qiu. 

“Electrons can still tunnel cross this new layer and it does not affect the light absorption of the cell. This way, we were able to extend the lifetime of the cell four-fold without loss in energy conversion efficiency”.

The lifespan of the new perovskite device was extended to over 250 hours – still not enough to compete with commercial photovoltaic cells regarding stability, but an important step forward toward fully functional perovskite solar cells.

Manufacturing LED lights from gasses

The bipolar electronic properties of the perovskite structure not only confer them the ability to generate electricity from solar energy but also can convert electricity into vivid light. Light-Emitting Diode – LED – technology, omnipresent in our daily life from laptop and smartphone screens to car lights and ceiling tubes, currently relies on semi-conductors that are difficult and expensive to manufacture. Perovskite LEDs are envisaged to become the new industry standard in the near future due to the lower cost and their efficiency to convert power into light. Moreover, by changing the atomic composition in the perovskite structure, perovskite LED can be easily tuned to emit specific colors.

The manufacturing of these perovskite LEDs is currently based on dipping or covering the targeted surface with liquid chemicals, a process which is difficult to setup, limited to small areas and with low consistency between samples. To overcome this issue, OIST researchers reported in the Journal of Physical Chemistry Letters (“Methylammonium Lead Bromide Perovskite Light-Emitting Diodes by Chemical Vapor Deposition”) the first perovskite LED assembled with gasses, a process called chemical vapor deposition or CVD.

“Chemical vapor deposition is already compatible with the industry, so in principle it would be easy to use this technology to produce LEDs,” commented Prof. Yabing Qi. “The second advantage in using CVD is a much lower variation from batch to batch compared to liquid-based techniques. Finally, the last point is scalability: CVD can achieve a uniform surface over very large areas”.

Like the solar cell, the perovskite LED also comprises many layers working in synergy. First, an indium tin oxide glass sheet and a polymer layer allow electrons into the LED. The chemicals required for the perovskite layer – lead bromide and methylammonium bromide – are then successively bound to the sample using CVD, in which the sample is exposed to gasses in order to convert to perovskite instead of typically solution-coating processes with liquid. In this process, the perovskite layer is composed of nanometer-small grains, whose sizes play a critical role in the efficiency of the device. Finally, the last step involves the deposition of two additional layers and a gold electrode, forming a complete LED structure. The LED can even form specific patterns using lithography during the manufacturing process.

Perovskite LED fabrication


Top: the perovskite LED sits in a furnace, where the Methylammonium Bromide (MABr) in gaseous form will be introduced into the system and deposit on the LED surface. Bottom left: a glass-based LED, glowing green when electricity is applied. Bottom right: size and shapes of the perovskite grains on the surface of the LED. (© American Chemical Society)

“With large grains, the surface of the LED is rough and less efficient in emitting light. The smaller the grain size, the higher the efficiency and the brighter the light,” explained Dr. Lingqiang Meng. “By changing the assembly temperature, we can now control the growth process and the size of the grains for the best efficiency”.

Controlling the grain size is not the only challenge for this first-of-its-kind assembling technique of LED lights.

“Perovskite is great, but the choice in the adjacent layers is really important too,” added Dr. Luis K. Ono. “To achieve high electricity-to-light conversion rates, every layer should be working in harmony with the others.”

The result is a flexible, thick film-like LED with a customizable pattern. The luminance, or brightness, currently reaches 560 cd/m2, while a typical computer screen emits 100 to 1000 cd/m2 and a ceiling fluorescent tube around 12,000 cd/m2.

Perovskite-LED


This large perovskite-LED was produced using chemical vapor deposition and connect to a 5V current, illuminating through an OIST pattern etched on the surface. (© American Chemical Society)

“Our next step is to improve the luminance a thousand-fold or more,” concluded Dr. Meng. “In addition, we have achieved a CVD-based LED emitting green light but we are now trying to repeat the process with different combinations of perovskite to obtain a vivid blue or red light”.

Source: By Wilko Duprez, Okinawa Institute of Technology

Rice University (NEWT) / China team use phage-enhanced nanoparticles to kill bacteria that foul water treatment systems


Clusters of nanoparticles with phage viruses attached find and kill Escherichia coli bacteria in a lab test at Rice University. 

Abstract:
Magnetic nanoparticle clusters have the power to punch through biofilms to reach bacteria that can foul water treatment systems, according to scientists at Rice University and the University of Science and Technology of China.
Magnetized viruses attack harmful bacteria: Rice, China team uses phage-enhanced nanoparticles to kill bacteria that foul water treatment systems.

Researchers at Rice and the University of Science and Technology of China have developed a combination of antibacterial phages and magnetic nanoparticle clusters that infect and destroy bacteria that are usually protected by biofilms in water treatment systems. (Credit: Alvarez Group/Rice University)

The nanoclusters developed through Rice’s Nanotechnology-Enabled Water Treatment (NEWT) Engineering Research Center carry bacteriophages – viruses that infect and propagate in bacteria – and deliver them to targets that generally resist chemical disinfection.

Without the pull of a magnetic host, these “phages” disperse in solution, largely fail to penetrate biofilms and allow bacteria to grow in solution and even corrode metal, a costly problem for water distribution systems.

The Rice lab of environmental engineer Pedro Alvarez and colleagues in China developed and tested clusters that immobilize the phages. A weak magnetic field draws them into biofilms to their targets.

The research is detailed in the Royal Society of Chemistry’s Environmental Science: Nano.
“This novel approach, which arises from the convergence of nanotechnology and virology, has a great potential to treat difficult-to-eradicate biofilms in an effective manner that does not generate harmful disinfection byproducts,” Alvarez said.

Biofilms can be beneficial in some wastewater treatment or industrial fermentation reactors owing to their enhanced reaction rates and resistance to exogenous stresses, said Rice graduate student and co-lead author Pingfeng Yu. “However, biofilms can be very harmful in water distribution and storage systems since they can shelter pathogenic microorganisms that pose significant public health concerns and may also contribute to corrosion and associated economic losses,” he said.

The lab used phages that are polyvalent – able to attack more than one type of bacteria – to target lab-grown films that contained strains of Escherichia coli associated with infectious diseases and Pseudomonas aeruginosa, which is prone to antibiotic resistance.

The phages were combined with nanoclusters of carbon, sulfur and iron oxide that were further modified with amino groups. The amino coating prompted the phages to bond with the clusters head-first, which left their infectious tails exposed and able to infect bacteria.

The researchers used a relatively weak magnetic field to push the nanoclusters into the film and disrupt it. Images showed they effectively killed E. coli and P. aeruginosa over around 90 percent of the film in a test 96-well plate versus less than 40 percent in a plate with phages alone.

The researchers noted bacteria may still develop resistance to phages, but the ability to quickly disrupt biofilms would make that more difficult. Alvarez said the lab is working on phage “cocktails” that would combine multiple types of phages and/or antibiotics with the particles to inhibit resistance.

Graduate student Ling-Li Li of the University of Science and Technology of China, Hefei, is co-lead author of the paper. Co-authors are graduate student Sheng-Song Yu and Han-Qing Yu, a professor at the University of Science and Technology of China, and graduate student Xifan Wang and temporary research scientist Jacques Mathieu of Rice.


The National Science Foundation and its Rice-based NEWT Engineering Research Center supported the research.

UC Berkeley Labs: A Semiconductor That Can Beat the Heat



Berkeley Lab, UC Berkeley scientists discover unique thermoelectric properties in cesium tin iodide

JULY 31, 2017

A newly discovered collective rattling effect in a type of crystalline semiconductor blocks most heat transfer while preserving high electrical conductivity – a rare pairing that scientists say could reduce heat buildup in electronic devices and turbine engines, among other possible applications.

A team led by scientists at the Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) discovered these exotic traits in a class of materials known as halide perovskites, which are also considered promising candidates for next-generation solar panels, nanoscale lasers, electronic cooling, and electronic displays.

These interrelated thermal and electrical (or “thermoelectric”) properties were found in nanoscale wires of cesium tin iodide (CsSnI3). The material was observed to have one of the lowest levels of heat conductivity among materials with a continuous crystalline structure.


Image – Rattling structures of halide perovskites: cesium tin iodide (left) and cesium lead iodide (right). (Credit: Berkeley Lab/UC Berkeley)

This so-called single-crystal material can also be more easily produced in large quantities than typical thermoelectric materials, such as silicon-germanium, researchers said.

“Its properties originate from the crystal structure itself. It’s an atomic sort of phenomenon,” said Woochul Lee, a postdoctoral researcher at Berkeley Lab who was the lead author of the study, published the week of July 31 in the Proceedings of the National Academy of Sciences journal. These are the first published results relating to the thermoelectric performance of this single crystal material.

Researchers earlier thought that the material’s thermal properties were the product of “caged” atoms rattling around within the material’s crystalline structure, as had been observed in some other materials. Such rattling can serve to disrupt heat transfer in a material.

“We initially thought it was atoms of cesium, a heavy element, moving around in the material,” said Peidong Yang, a senior faculty scientist at Berkeley Lab’s Materials Sciences Division who led the study.

Jeffrey Grossman, a researcher at the Massachusetts Institute of Technology, then performed some theory work and computerized simulations that helped to explain what the team had observed. 

Researchers also used Berkeley Lab’s Molecular Foundry, which specializes in nanoscale research, in the study.

“We believe there is essentially a rattling mechanism, not just with the cesium. It’s the overall structure that’s rattling; it’s a collective rattling,” Yang said. “The rattling mechanism is associated with the crystal structure itself,” and is not the product of a collection of tiny crystal cages. “It is group atomic motion,” he added.

Within the material’s crystal structure, the distance between atoms is shrinking and growing in a collective way that prevents heat from easily flowing through.

But because the material is composed of an orderly, single-crystal structure, electrical current can still flow through it despite this collective rattling. Picture its electrical conductivity is like a submarine traveling smoothly in calm underwater currents, while its thermal conductivity is like a sailboat tossed about in heavy seas at the surface.

Yang said two major applications for thermoelectric materials are in cooling, and in converting heat into electrical current. For this particular cesium tin iodide material, cooling applications such as a coating to help cool electronic camera sensors may be easier to achieve than heat-to-electrical conversion, he said.

A challenge is that the material is highly reactive to air and water, so it requires a protective coating or encapsulation to function in a device.

Cesium tin iodide was first discovered as a semiconductor material decades ago, and only in recent years has it been rediscovered for its other unique traits, Yang said. “It turns out to be an amazing gold mine of physical properties,” he noted.


SEM images of suspended micro-island devices. Individual AIHP NW is suspended between two membranes. (Credit: Berkeley Lab/UC Berkeley)

To measure the thermal conductivity of the material, researchers bridged two islands of an anchoring material with a cesium tin iodide nanowire. The nanowire was connected at either end to micro-islands that functioned as both a heater and a thermometer. 
Researchers heated one of the islands and precisely measured how the nanowire transported heat to the other island.

They also performed scanning electron microscopy to precisely measure the dimensions of the nanowire. They used these dimensions to provide an exacting measure of the material’s thermal conductivity. The team repeated the experiment with several different nanowire materials and multiple nanowire samples to compare thermoelectric properties and verify the thermal conductivity measurements.

“A next step is to alloy this (cesium tin iodide) material,” Lee said. “This may improve the thermoelectric properties.”

Also, just as computer chip manufacturers implant a succession of elements into silicon wafers to improve their electronic properties – a process known as “doping” – scientists hope to use similar techniques to more fully exploit the thermoelectric traits of this semiconductor material. This is relatively unexplored territory for this class of materials, Yang said.

The research team also included other scientists from Berkeley Lab’s Materials Sciences Division and the Molecular Foundry, the Kavli Energy NanoScience Institute at UC Berkeley and Berkeley Lab, and UC Berkeley’s Department of Chemistry.

The Molecular Foundry is a DOE Office of Science User Facility that provides free access to state-of-the-art equipment and multidisciplinary expertise in nanoscale science to visiting scientists from all over the world.

This work was supported by the Department of Energy’s Office of Basic Energy Sciences.
More information about Peidong Yang’s research group: http://nanowires.berkeley.edu/.

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Lawrence Berkeley National Laboratory addresses the world’s most urgent scientific challenges by advancing sustainable energy, protecting human health, creating new materials, and revealing the origin and fate of the universe. Founded in 1931, Berkeley Lab’s scientific expertise has been recognized with 13 Nobel Prizes. The University of California manages Berkeley Lab for the U.S. Department of Energy’s Office of Science. For more, visit http://www.lbl.gov.
DOE’s Office of Science is the single largest supporter of basic research in the physical sciences in the United States, and is working to address some of the most pressing challenges of our time. For more information, please visit science.energy.gov.

Breakthrough in thin electrically conducting sheets paves way for smaller electronic devices



Through nanotechnology, physicists Dr Raymond McQuaid, Dr Amit Kumar and Professor Marty Gregg from Queen’s University’s School of Mathematics and Physics, have created unique 2-D sheets, called domain walls, which exist within crystalline materials.

The sheets are almost as thin as the wonder-material graphene, at just a few atomic layers. However, they can do something that graphene can’t – they can appear, disappear or move around within the crystal, without permanently altering the crystal itself.

This means that in future, even smaller electronic devices could be created, as electronic circuits could constantly reconfigure themselves to perform a number of tasks, rather than just having a sole function.
Professor Marty Gregg explains: “Almost all aspects of modern life such as communication, healthcare, finance and entertainment rely on microelectronic devices. 

The demand for more powerful, smaller technology keeps growing, meaning that the tiniest devices are now composed of just a few atoms – a tiny fraction of the width of human hair.”


Breakthrough in thin electrically conducting sheets paves way for smaller electronic devices Credit: Queen’s University Belfast

“As things currently stand, it will become impossible to make these devices any smaller – we will simply run out of space. This is a huge problem for the computing industry and new, radical, disruptive technologies are needed. One solution is to make electronic circuits more ‘flexible’ so that they can exist at one moment for one purpose, but can be completely reconfigured the next moment for another purpose.”

The team’s findings, which have been published in Nature Communications, pave the way for a completely new way of data processing.

Professor Gregg says: “Our research suggests the possibility to “etch-a-sketch” nanoscale electrical connections, where patterns of electrically conducting wires can be drawn and then wiped away again as often as required.

“In this way, complete electronic circuits could be created and then dynamically reconfigured when needed to carry out a different role, overturning the paradigm that electronic circuits need be fixed components of hardware, typically designed with a dedicated purpose in mind.”


Breakthrough in thin electrically conducting sheets paves way for smaller electronic devices Credit: Queen’s University Belfast

There are two key hurdles to overcome when creating these 2-D sheets, long straight walls need to be created. These need to effectively conduct electricity and mimic the behavior of real metallic wires. It is also essential to be able to choose exactly where and when the domain walls appear and to reposition or delete them.

 Through the research, the Queen’s researchers have discovered some solutions to the hurdles. Their research proves that long conducting sheets can be created by squeezing the crystal at precisely the location they are required, using a targeted acupuncture-like approach with a sharp needle. The sheets can then be moved around within the crystal using applied electric fields to position them.

Dr Raymond McQuaid, a recently appointed lecturer in the School of Mathematics and Physics at Queen’s University, added: “Our team has demonstrated for the first time that copper-chlorine boracite crystals can have straight conducting walls that are hundreds of microns in length and yet only nanometres thick. 

The key is that, when a needle is pressed into the crystal surface, a jigsaw puzzle-like pattern of structural variants, called “domains”, develops around the contact point. The different pieces of the pattern fit together in a unique way with the result that the conducting walls are found along certain boundaries where they meet.

“We have also shown that these walls can then be moved using applied electric fields, therefore suggesting compatibility with more conventional voltage operated devices. Taken together, these two results are a promising sign for the potential use of conducting walls in reconfigurable nano-electronics.”

 

More information: Raymond G.P. McQuaid et al. Injection and controlled motion of conducting domain walls in improper ferroelectric Cu-Cl boracite, Nature Communications (2017). DOI: 10.1038/ncomms15105

Provided by: Queen’s University Belfast