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Friday, August 1, 2014

Scientists use light to stitch ‘invisible’ nanoparticles together


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Image: The University of Cambridge

Tuesday, 29 July 2014
A team working on invisibility cloak technology has come up with a new technique that uses light to thread long chains of nanoparticles into light-refracting material.

At the centre of this new technique are tiny blocks made from ‘metamaterials’ - a special type of artificial material engineered to have properties unlike anything found in nature. These nanoparticle building blocks are just a few billionths of a metre wide, and researchers from the University of Cambridge in the UK have figured out how to control the way light flows through them. 
Controlling the way light interacts with a material is a key element of any ‘invisibility’ technology, and these metamaterials have been designed to refract light in a direction that renders them invisible to the naked eye.
In order to do this, the researchers needed to 'stitch' the metamaterial nanoparticles together into several long strings, which they did by placing the metamaterials in some water and blasting them with an unfocused laser light. "These strings can then be stacked into layers one on top of the other, similar to LEGO bricks," they say in a press release. "The method makes it possible to produce materials in much higher quantities than can be made through current techniques.”
Now, what we really want to know is… when do we get our invisibility cloaks? The next step is figuring out how to build bridges between the nanoparticles so they can be produced in larger quantities. "There is a knack to doing this," says Katie Collins at Wired UK, "and it involves spacing the material blocks carefully and accurately using barrel-shaped molecules called cucurbiturils so that it's as easy as possible to retain control over the process."

The researchers published their results in the journal Nature Communications.

Solar energy: Dyes help harvest light

July 30, 2014
A new dye-sensitized solar cell absorbs a broad range of visible and infrared wavelengths. Dye-sensitized solar cells rely on dyes that absorb light to mobilize a current of electrons and are a promising source of clean energy. Scientists have now developed zinc porphyrin dyes that harvest light in both the visible and near-infrared parts of the spectrum. Their research suggests that chemical modification of these dyes could enhance the energy output of DSSCs.
DSSCs are easier and cheaper to manufacture than conventional silicon solar cells, but they currently have a lower efficiency. Ruthenium-based dyes have been traditionally used in DSSCs, but in 2011 researchers developed a more efficient dye based on a zinc atom surrounded by a ring-shaped molecule called a porphyrin. Solar cells using this new dye, called YD2-o-C8, convert visible light into electricity with an efficiency of up to 12.3 per cent. Wu's team aimed to improve that efficiency by developing a zinc porphyrin dye that can also absorb infrared light.
The most successful dyes developed by Wu's team, WW-5 and WW-6, unite a zinc porphyrin core with a system of fused carbon rings bridged by a nitrogen atom, known as an N-annulated perylene group. Solar cells containing these dyes absorbed more infrared light than YD2-o-C8 and had efficiencies of up to 10.5 per cent, matching the performance of an YD2-o-C8 cell under the same testing conditions (see image).
Theoretical calculations indicate that connecting the porphyrin and perylene sections of these dyes by a carbon-carbon triple bond, which acts as an electron-rich linker, improved the flow of electrons between them. This bond also reduced the light energy needed to excite electrons in the molecule, boosting the dye's ability to harvest infrared light.
Adding bulky chemical groups to the dyes also improved their solubility and prevented them from aggregating -- something that tends to reduce the efficiency of DSSCs.
However, both WW-5 and WW-6 are slightly less efficient than YD2-o-C8 at converting visible light into electricity, and they also produce a lower voltage. "We are now trying to solve this problem through modifications based on the chemical structure of WW-5 and WW-6," says Wu.
Comparing the results from more perylene-porphyrin dyes should indicate ways to overcome these hurdles, and may even extend light absorption further into the infrared. "The top priority is to improve the power conversion efficiency," says Wu. "Our target is to push the efficiency to more than 13 per cent in the near future."

Story Source:  The Agency for Science, Technology and Research (A*STAR)
 

Monday, July 28, 2014

Nano-supercapacitors for electric cars

July 24, 2014
Innovative nano-material based supercapacitors are set to bring mass market appeal a good step closer to the lukewarm public interest in Germany. This movement is currently being motivated by the advancements in the state-of-the-art of this device.
Electric cars are very much welcomed in Norway and they are a common sight on the roads of the Scandinavian country -- so much so that electric cars topped the list of new vehicle registrations for the second time. This poses a stark contrast to the situation in Germany, where electric vehicles claim only a small portion of the market. Of the 43 million cars on the roads in Germany, only a mere 8000 are electric powered. The main factors discouraging motorists in Germany from switching to electric vehicles are the high investments cost, their short driving ranges and the lack of charging stations. Another major obstacle en route to the mass acceptance of electric cars is the charging time involved. The minutes involved in refueling conventional cars are so many folds shorter that it makes the situation almost incomparable. However, the charging durations could be dramatically shortened with the inclusion of supercapacitors.
These alternative energy storage devices are fast charging and can therefore better support the use of economical energy in electric cars. Taking traditional gasoline-powered vehicles for instance, the action of braking converts the kinetic energy into heat which is dissipated and unused. Per contra, generators on electric vehicles are able to tap into the kinetic energy by converting it into electricity for further usage. This electricity often comes in jolts and requires storage devices that can withstand high amount of energy input within a short period of time. In this example, supercapacitors with their capability in capturing and storing this converted energy in an instant fits in the picture wholly. Unlike batteries that offer limited charging/discharging rates, supercapacitors require only seconds to charge and can feed the electric power back into the air-conditioning systems, defogger, radio, etc. as required.
Rapid energy storage devices are distinguished by their energy and power density characteristics -- in other words, the amount of electrical energy the device can deliver with respect to its mass and within a given period of time. Supercapacitors are known to possess high power density, whereby large amounts of electrical energy can be provided or captured within short durations, albeit at a short-coming of low energy density. The amount of energy in which supercapacitors are able to store is generally about 10% that of electrochemical batteries (when the two devices of same weight are being compared).
This is precisely where the challenge lies and what the "ElectroGraph" project is attempting to address. ElectroGraph is a project supported by the EU and its consortium consists of ten partners from both research institutes and industries. One of the main tasks of this project is to develop new types of supercapacitors with significantly improved energy storage capacities. As the project is approaches its closing phase in June, the project coordinator at Fraunhofer Institute for Manufacturing Engineering and Automation IPA in Stuttgart, Carsten Glanz explained the concept and approach taken en route to its successful conclusion: "during the storage process, the electrical energy is stored as charged particles attached on the electrode material." "So to store more energy efficiently, we designed light weight electrodes with larger, usable surfaces."
Graphene electrodes significantly improve energy efficiency
In numerous tests, the researcher and his team investigated the nano-material graphene, whose extremely high specific surface area of up to 2,600 m2/g and high electrical conductivity practically cries out for use as an electrode material. It consists of an ultrathin monolayer lattice made of carbon atoms. When used as an electrode material, it greatly increases the surface area with the same amount of material. From this aspect, graphene is showing its potential in replacing activated carbon -- the material that has been used in commercial supercapacitors to date -- which has a specific surface area between 1000 and 1800 m2/g.
"The space between the electrodes is filled with a liquid electrolyte," revealed Glanz. "We use ionic liquids for this purpose. Graphene-based electrodes together with ionic liquid electrolytes present an ideal material combination where we can operate at higher voltages." "By arranging the graphene layers in a manner that there is a gap between the individual layers, the researchers were able to establish a manufacturing method that efficiently uses the intrinsic surface area available of this nano-material. This prevents the individual graphene layers from restacking into graphite, which would reduce the storage surface and consequently the amount of energy storage capacity.
"Our electrodes have already surpassed commercially available one by 75 percent in terms of storage capacity," emphasizes the engineer. "I imagine that the cars of the future will have a battery connected to many capacitors spread throughout the vehicle, which will take over energy supply during high-power demand phases during acceleration for example and ramming up of the air-conditioning system. These capacitors will ease the burden on the battery and cover voltage peaks when starting the car. As a result, the size of massive batteries can be reduced."
In order to present the new technology, the ElectroGraph consortium developed a demonstrator consisting of supercapacitors installed in an automobile side-view mirror and charged by a solar cell in an energetically self-sufficient system.

Story Source:   Fraunhofer-Gesellschaft.

Nanoparticle 'alarm clock' tested to awaken immune systems put to sleep by cancer

July 25, 2014
Researchers are exploring ways to wake up the immune system so it recognizes and attacks invading cancer cells. One pioneering approach uses nanoparticles to jumpstart the body’s ability to fight tumors. Nanoparticles are too small to imagine. One billion could fit on the head of a pin. This makes them stealthy enough to penetrate cancer cells with therapeutic agents such as antibodies, drugs, vaccine type viruses, or even metallic particles.
One pioneering approach, discussed in a review article published this week in WIRE's Nanomedicine and Nanobiotechnology, uses nanoparticles to jumpstart the body’s ability to fight tumors. Nanoparticles are too small to imagine. One billion could fit on the head of a pin. This makes them stealthy enough to penetrate cancer cells with therapeutic agents such as antibodies, drugs, vaccine type viruses, or even metallic particles. Though small, nanoparticles can pack large payloads of a variety of agents that have different effects that activate and strengthen the body’s immune system response against tumors.
There is an expanding array of nanoparticle types being developed and tested for cancer therapy. They are primarily being used to package and deliver the current generation of cancer cell killing drugs and progress is being made in that effort.
“ Our lab’s approach differs from most in that we use nanoparticles to stimulate the immune system to attack tumors and there are a variety of potential ways that can be done,” said Steve Fiering, PhD, Norris Cotton Cancer Center researcher and professor of Microbiology and Immunology, and of Genetics at the Geisel School of Medicine at Dartmouth. “Perhaps the most exciting potential of nanoparticles is that although very small, they can combine multiple therapeutic agents.”
The immune therapy methods limit a tumor’s ability to trick the immune system. It helps it to recognize the threat and equip it to effectively attack the tumor with more “soldier” cells. These approaches are still early in development in the laboratory or clinical trials.
“Now that efforts to stimulate anti-tumor immune responses are moving from the lab to the clinic, the potential for nanoparticles to be utilized to improve an immune-based therapy approach is attracting a lot of attention from both scientists and clinicians. And clinical usage does not appear too distant,” said Fiering.
Fiering is testing the use of heat in combination with nanoparticles. An inactive metallic nanoparticle containing iron, silver, or gold is absorbed by a cancer cell. Then the nanoparticle is activated using magnetic energy, infrared light, or radio waves. The interaction creates heat that kills cancer cells. The heat, when precisely applied, can prompt the immune system to kill cancer cells that have not been heated. The key to this approach is minimizing healthy tissue damage while maximizing cancerous tumor destruction of the sort that improves recognition of the tumor by the immune system.
Fiering cautions that there is a great deal of research and many technical variables that should be explored to find the most effective ways to use nanoparticles to heat tumors and stimulate anti-tumor immunity.
According to Fiering, this approach is far from new, “The use of heat to treat cancer was first recorded by ancient Egyptians. But has reemerged with high tech modern systems as a contributor to the new paradigm of fighting cancer with the patients’ own immune system.”


How to power California with wind, water and sun


July 24, 2014
New research outlines the path to a possible future for California in which renewable energy creates a healthier environment, generates jobs and stabilizes energy prices.
Imagine a smog-free Los Angeles, where electric cars ply silent freeways, solar panels blanket rooftops and power plants run on heat from beneath the Earth, from howling winds and from the blazing desert sun.
A new Stanford study finds that it is technically and economically feasible to convert California's all-purpose energy infrastructure to one powered by clean, renewable energy. Published in Energy, the plan shows the way to a sustainable, inexpensive and reliable energy supply in California that could create tens of thousands of jobs and save billions of dollars in pollution-related health costs.
"If implemented, this plan will eliminate air pollution mortality and global warming emissions from California, stabilize prices and create jobs -- there is little downside," said Mark Z. Jacobson, the study's lead author and a Stanford professor of civil and environmental engineering. He is also the director of Stanford's Atmosphere/Energy Program and a senior fellow with the Stanford Woods Institute for the Environment and the Precourt Institute for Energy.
Jacobson's study outlines a plan to fulfill all of the Golden State's transportation, electric power, industry, and heating and cooling energy needs with renewable energy by 2050. It calculates the number of new devices and jobs created, land and ocean areas required, and policies needed for infrastructure changes. It also provides new estimates of air pollution mortality and morbidity impacts and costs based on multiple years of air quality data. The plan is analogous to one that Jacobson and other researchers developed for New York state.
The study concludes that, while a wind, water and sunlight conversion may result in initial capital cost increases, such as the cost of building renewable energy power plants, these costs would be more than made up for over time by the elimination of fuel costs. The overall switch would reduce California's end-use power demand by about 44 percent and stabilize energy prices, since fuel costs would be zero, according to the study.
It would also create a net gain, after fossil-fuel and nuclear energy job losses are accounted for, of about 220,000 manufacturing, installation and technology construction and operation jobs. On top of that, the state would reap net earnings from these jobs of about $12 billion annually.
According to the researchers' calculations, one scenario suggests that all of California's 2050 power demands could be met with a mix of sources, including:
  • 25,000 onshore 5-megawatt wind turbines
  • 1,200 100-megawatt concentrated solar plants
  • 15 million 5-kilowatt residential rooftop photovoltaic systems
  • 72 100-megawatt geothermal plants
  • 5,000 0.75-megawatt wave devices
  • 3,400 1-megawatt tidal turbines
The study states that if California switched to wind, water and sunlight for renewable energy, air pollution-related deaths would decline by about 12,500 annually and the state would save about $103 billion, or about 4.9 percent of the state's 2012 gross domestic product, in related health costs every year. The study also estimates that resultant emissions decreases would reduce global climate change costs in 2050 -- such as coastal erosion and extreme weather damage -- by about $48 billion per year.
"I think the most interesting finding is that the plan will reduce social costs related to air pollution and climate change by about $150 billion per year in 2050, and that these savings will pay for all new energy generation in only seven years," said study co-author Mark Delucchi of the University of California, Davis.
"The technologies needed for a quick transition to an across-the-board, renewables-based statewide energy system are available today," said Anthony Ingraffea, a Cornell University engineering professor and study co-author. "Like New York, California has a clear choice to make: Double down on 20th-century fossil fuels or accelerate toward a clean, green energy future."
Currently, most of California's energy comes from oil, natural gas, nuclear power and small amounts of coal. Under the plan that Jacobson and his fellow researchers advance, 55.5 percent of the state's energy for all purposes would come from solar, 35 percent from wind and the remainder from a combination of hydroelectric, geothermal, tidal and wave energy.
All vehicles would run on battery-electric power and/or hydrogen fuel cells. Electricity-powered air- and ground-source heat pumps, geothermal heat, heat exchangers and backup electric resistance heaters would replace natural gas and oil for home heating and air-conditioning. Air- and ground-source heat pump water heaters powered by electricity and solar hot water preheaters would provide hot water for homes. High temperatures for industrial processes would be obtained with electricity and hydrogen combustion.
To ensure grid reliability, the plan outlines several methods to match renewable energy supply with demand and to smooth out the variability of wind, water and sunlight resources. These include a grid management system to shift times of demand to better match with timing of power supply; and "over-sizing" peak generation capacity to minimize times when available power is less than demand. The study refers to a previously published analysis that demonstrated that California could provide a reliable grid with nearly 100 percent clean, renewable energy.
The footprint on the ground for the new energy infrastructure would be about 0.9 percent of California's land area, mostly for solar power plants. The spacing area between wind turbines, which could be used for multiple purposes, including agriculture and rangeland, is another 2.77 percent.
"I believe that with these plans, the people and political leaders of California and New York can chart a new way forward for our country and for the world," said study co-author Robert Howarth, a Cornell University professor of ecology and environmental biology.
The study's authors are developing similar plans for all U.S. states. They took no funding from any interest group, company or government agency for this study.

Story Source:  Stanford University.
 

Friday, July 25, 2014

Central University of Jharkhand - Even Semester Results


Even Semester Result-2014
1. Centre for Business Administration- Xth Semester
2. Centre for English Studies-Xth Semester
3. Centre for Land Resource Management -IV Semester (2 Years)
4. CENTRE FOR EDUCATION (BABED) - SEMESTER - II
5. CENTRE FOR ENVIRONMENTAL SCIENCES-SEMESTER- IV
6. CENTRE FOR FAR EAST LANGUAGE-CHINESE-SEMESTER-II,SEMESTER-IV
7. CENTRE FOR APPLIED CHEMISTRY-SEMESTER-IV,SEMESTER-VI,SEMESTER-VIII
8. CENTRE FOR LIFE SCIENCES-SEMESTER-IV,SEMESTER-VI
9. CENTRE FOR BUSINESS ADMINISTRATION -SEMESTER -II,SEMESTER-IV,SEMESTER- VI,SEMESTER -VIII
10. CENTRE FOR MASS COMMUNICATION-SEMESTER-II,SEMESTER-IV,SEMESTER-VIII
11. CENTRE FOR NANOTECHNOLOGY-SEMESTER-IV ,SEMESTER-VI,SEMESTER-VIII
12. CENTRE FOR WATER ENGINEERING AND MANAGEMENT-SEMESTER-IV,SEMESTER-VI,SEMESTER-VIII
13. CENTRE FOR LAND RESOURCE MANAGEMENT-SEMESTER-II,M.Sc. SEMESTER-IV
14. CENTRE FOR EDUCATION (BSCBED) SEMESTER-II
15. BPA-SEMESTER-II
16. FEL (Korean) 1st Sem ertificate Course 12- 2013
17. FEL (Korean) 1st Sem ertificate Course 2013
18. FELK 2nd Semester 2014
19. FELK 4th Semester 2014
20. FELK Diploma 2nd Semester 2012- 13 batch
21. FELK Diploma 2nd Semester 2013- 14 batch
22. FELT 2nd Even Sem 2014 Notice Board
23. Geoinformatics 2nd SEM M.Sc
24. IAC 2nd Even Sem 2014
25. IAM 2nd Sem Even 2014
26. IAM 4th Sem Even 2014
27. IAM 6th Sem 2014
28. IAM 8th Sem 2014
29. IAP 2nd Even Sem 2014
30. IAP 4th Even Sem 2014
31. IAP 8th Even Sem 2014
32. ICS 8th Even Sem 2014
33. IEE 2nd Even Sem 2014
34. IEE 4th Even Sem 2014
35. IEE 6th Even Sem 2014
36. IEN 2nd Even Sem 2014
37. IEN 4th Even Sem 2014
38. IEN 6th Even Sem 2014
39. IEN 8th Even Sem 2014
40. ILS 2nd Even Sem 2014
41. ILS 8th Even Sem 2014
42. INT 2nd Even Sem 2014
43. IR 2nd Sem 2014
44. IR 4th Sem 2014
45. IWEM 2nd Even Sem 2014
46. LRM 2nd SEM 5yr Integrated
47. IAM X sem 2014
48. HRCM 2nd Sem 2014
49. IMC X sem 2014
50. IMC VI sem 2014
51. ICS II Sem
52. ICS IV Sem
53. ICS VI Sem
54. Mobile Computing II Sem

Source : www.cuj.ac.in

Steam energy from the sun: New spongelike structure converts solar energy into steam

July 24, 2014
A new material structure generates steam by soaking up the sun. The structure -- a layer of graphite flakes and an underlying carbon foam -- is a porous, insulating material structure that floats on water. When sunlight hits the structure's surface, it creates a hotspot in the graphite, drawing water up through the material's pores, where it evaporates as steam. The brighter the light, the more steam is generated.

The new material is able to convert 85 percent of incoming solar energy into steam -- a significant improvement over recent approaches to solar-powered steam generation. What's more, the setup loses very little heat in the process, and can produce steam at relatively low solar intensity. This would mean that, if scaled up, the setup would likely not require complex, costly systems to highly concentrate sunlight.
Hadi Ghasemi, a postdoc in MIT's Department of Mechanical Engineering, says the spongelike structure can be made from relatively inexpensive materials -- a particular advantage for a variety of compact, steam-powered applications.
"Steam is important for desalination, hygiene systems, and sterilization," says Ghasemi, who led the development of the structure. "Especially in remote areas where the sun is the only source of energy, if you can generate steam with solar energy, it would be very useful."
Ghasemi and mechanical engineering department head Gang Chen, along with five others at MIT, report on the details of the new steam-generating structure in the journal Nature Communications.
Cutting the optical concentration
Today, solar-powered steam generation involves vast fields of mirrors or lenses that concentrate incoming sunlight, heating large volumes of liquid to high enough temperatures to produce steam. However, these complex systems can experience significant heat loss, leading to inefficient steam generation.
Recently, scientists have explored ways to improve the efficiency of solar-thermal harvesting by developing new solar receivers and by working with nanofluids. The latter approach involves mixing water with nanoparticles that heat up quickly when exposed to sunlight, vaporizing the surrounding water molecules as steam. But initiating this reaction requires very intense solar energy -- about 1,000 times that of an average sunny day.
By contrast, the MIT approach generates steam at a solar intensity about 10 times that of a sunny day -- the lowest optical concentration reported thus far. The implication, the researchers say, is that steam-generating applications can function with lower sunlight concentration and less-expensive tracking systems.
"This is a huge advantage in cost-reduction," Ghasemi says. "That's exciting for us because we've come up with a new approach to solar steam generation."
From sun to steam
The approach itself is relatively simple: Since steam is generated at the surface of a liquid, Ghasemi looked for a material that could both efficiently absorb sunlight and generate steam at a liquid's surface.
After trials with multiple materials, he settled on a thin, double-layered, disc-shaped structure. Its top layer is made from graphite that the researchers exfoliated by placing the material in a microwave. The effect, Chen says, is "just like popcorn": The graphite bubbles up, forming a nest of flakes. The result is a highly porous material that can better absorb and retain solar energy.
The structure's bottom layer is a carbon foam that contains pockets of air to keep the foam afloat and act as an insulator, preventing heat from escaping to the underlying liquid. The foam also contains very small pores that allow water to creep up through the structure via capillary action.
As sunlight hits the structure, it creates a hotspot in the graphite layer, generating a pressure gradient that draws water up through the carbon foam. As water seeps into the graphite layer, the heat concentrated in the graphite turns the water into steam. The structure works much like a sponge that, when placed in water on a hot, sunny day, can continuously absorb and evaporate liquid.
The researchers tested the structure by placing it in a chamber of water and exposing it to a solar simulator -- a light source that simulates various intensities of solar radiation. They found they were able to convert 85 percent of solar energy into steam at a solar intensity 10 times that of a typical sunny day.
Ghasemi says the structure may be designed to be even more efficient, depending on the type of materials used.
"There can be different combinations of materials that can be used in these two layers that can lead to higher efficiencies at lower concentrations," Ghasemi says. "There is still a lot of research that can be done on implementing this in larger systems."


Copper nanowires could become basis for new solar cells

April 23, 2014
By looking at a piece of material in cross section, engineers discovered how copper sprouts grass-like nanowires that could one day be made into solar cells. The researchers worked with copper foil, a simple material similar to household aluminum foil. When most metals are heated, they form a thick metal oxide film. However, a few metals, such as copper, iron and zinc, grow grass-like structures known as nanowires, which are long, cylindrical structures a few hundred nanometers wide by many microns tall. They set out to determine how the nanowires grow.

Banerjee, assistant professor of materials science and an expert in working with nanomaterials, Fei Wu, graduate research assistant, and Yoon Myung, PhD, a postdoctoral research associate, also took a step toward making solar cells and more cost-effective.
Banerjee and his team worked with copper foil, a simple material similar to household aluminum foil. When most metals are heated, they form a thick metal oxide film. However, a few metals, such as copper, iron and zinc, grow grass-like structures known as nanowires, which are long, cylindrical structures a few hundred nanometers wide by many microns tall. They set out to determine how the nanowires grow.
"Other researchers look at these wires from the top down," Banerjee says. "We wanted to do something different, so we broke our sample and looked at it from the side view to see if we got different information, and we did."
Results of the research were recently published in CrystEngComm. Washington University's International Center for Advanced Renewable Energy & Sustainability (I-CARES) and the McDonnell Academy Global Energy and Environment Partnership (MAGEEP) provided funding for the research.
The team used Raman spectroscopy, a technique that uses light from a laser beam to interact with molecular vibrations or other movements. They found an underlying thick film made up of two different copper oxides (CuO and Cu2O) that had narrow, vertical columns of grains running through them. In between these columns, they found grain boundaries that acted as arteries through which the copper from the underlying layer was being pushed through when heat was applied, creating the nanowires.
"We're now playing with this ionic transport mechanism, turning it on and off and seeing if we can get some different forms of wires," says Banerjee, who runs the Laboratory for Emerging and Applied Nanomaterials (L.E.A.N.).
Like solar cells, the nanowires are single crystal in structure, or a continuous piece of material with no grain boundaries, Banerjee says.
"If we could take these and study some of the basic optical and electronic properties, we could potentially make solar cells," he says. "In terms of optical properties, copper oxides are well-positioned to become a solar energy harvesting material."
The find may also benefit other engineers who want to use single crystal oxides in scientific research. Manufacturing single crystal Cu2O for research is very expensive, Banerjee says, costing up to about $1,500 for one crystal.
"But if you can live with this form that's a long wire instead of a small crystal, you can really use it to study basic scientific phenomena," Banerjee says.
Banerjee's team also is looking for other uses for the nanowires, including acting as a semiconductor between two materials, as a photocatalyst, a photovoltaic or an electrode for splitting water.

Atomic switcheroo explains origins of thin-film solar cell mystery

April 23, 2014
Treating cadmium-telluride (CdTe) solar cell materials with cadmium-chloride improves their efficiency, but researchers have not fully understood why.Now, an atomic-scale examination of the thin-film solar cells led by the Department of Energy's Oak Ridge National Laboratory has answered this decades-long debate about the materials' photovoltaic efficiency increase after treatment.
A research team from ORNL, the University of Toledo and DOE's National Renewable Energy Laboratory used electron microscopy and computational simulations to explore the physical origins of the unexplained treatment process. The results are published in Physical Review Letters (PRL).
Thin-film CdTe solar cells are considered a potential rival to silicon-based photovoltaic systems because of their theoretically low cost per power output and ease of fabrication. Their comparatively low historical efficiency in converting sunlight into energy, however, has limited the technology's widespread use, especially for home systems.
Research in the 1980s showed that treating CdTe thin films with cadmium-chloride significantly raises the cell's efficiency, but scientists have been unable to determine the underlying causes. ORNL's Chen Li, first author on the PRL study, explains that the answer lay in investigating the material at an atomic level.
"We knew that chlorine was responsible for this magical effect, but we needed to find out where it went in the material's structure," Li said. "Only by understanding the structure can we understand what's wrong in this solar cell -- why the efficiency is not high enough, and how can we push it further."
By comparing the solar cells before and after chlorine treatment, the researchers realized that atom-scale grain boundaries were implicated in the enhanced performance. Grain boundaries are tiny defects that that normally act as roadblocks to efficiency, because they inhibit carrier collection which greatly reduces the solar cell power.
Using state of the art electron microscopy techniques to study the thin films' structure and chemical composition after treatment, the researchers found that chlorine atoms replaced tellurium atoms within the grain boundaries. This atomic substitution creates local electric fields at the grain boundaries that boost the material's photovoltaic performance instead of damaging it.
The research team's finding, in addition to providing a long-awaited explanation, could be used to guide engineering of higher-efficiency CdTe solar cells. Controlling the grain boundary structure, says Li, is a new direction that could help raise the cell efficiencies closer to the theoretical maximum of 32 percent light-to-energy conversion. Currently, the record CdTe cell efficiency is only 20.4 percent.
"We think that if all the grain boundaries in a thin film material could be aligned in same direction, it could improve cell efficiency even further," Li said.

Story Source:   Oak Ridge National Laboratory.

Synthesized 'solar' jet fuel: Renewable kerosene from sunlight, water and carbon dioxide

May 3, 2014
With the first ever production of synthesized "solar" jet fuel, the EU-funded SOLAR-JET project has successfully demonstrated the entire production chain for renewable kerosene obtained directly from sunlight, water and carbon dioxide, therein potentially revolutionizing the future of aviation. This process has also the potential to produce any other type of fuel for transport applications, such as diesel, gasoline or pure hydrogen in a more sustainable way.
Several notable research organizations from academia through to industry (ETH Zürich, Bauhaus Luftfahrt, Deutsches Zentrum für Luft- und Raumfahrt (DLR), ARTTIC and Shell Global Solutions) have explored a thermochemical pathway driven by concentrated solar energy. A new solar reactor technology has been pioneered to produce liquid hydrocarbon fuels suitable for more sustainable transportation.
"Increasing environmental and supply security issues are leading the aviation sector to seek alternative fuels which can be used interchangeably with today's jet fuel, so-called drop-in solutions," states Dr. Andreas Sizmann, the project coordinator at Bauhaus Luftfahrt. "With this first-ever proof-of-concept for 'solar' kerosene, the SOLAR-JET project has made a major step towards truly sustainable fuels with virtually unlimited feedstocks in the future.
The SOLAR-JET project demonstrated an innovative process technology using concentrated sunlight to convert carbon dioxide and water to a so-called synthesis gas (syngas). This is accomplished by means of a redox cycle with metal-oxide based materials at high temperatures. The syngas, a mixture of hydrogen and carbon monoxide, is finally converted into kerosene by using commercial Fischer-Tropsch technology.
"The solar reactor technology features enhanced radiative heat transfer and fast reaction kinetics, which are crucial for maximizing the solar-to-fuel energy conversion efficiency" said Professor Aldo Steinfeld, leading the fundamental research and development of the solar reactor at ETH Zürich.
Although the solar-driven redox cycle for syngas production is still at an early stage of development, the processing of syngas to kerosene is already being deployed by companies, including Shell, on a global scale. This combined approach has the potential to provide a secure, sustainable and scalable supply of renewable aviation fuel and more generally for transport applications. Moreover, Fischer-Tropsch derived kerosene is already approved for commercial aviation.
"This is potentially a very interesting novel pathway to liquid hydrocarbon fuels using focussed solar power," said Professor Hans Geerlings at Shell. "Although the individual steps of the process have previously been demonstrated at various scales, no attempt had been made previously to integrate the end-to-end system. We look forward to working with the project partners to drive forward research and development in the next phase of the project on such an ambitious emerging technology."
SOLAR-JET (Solar chemical reactor demonstration and Optimization for Long-term Availability of Renewable JET fuel) was launched in June 2011 and is receiving financial support from the European Union within the 7th Framework Programme for a duration of four years. In a first step, the technical feasibility of producing solar kerosene was proven. In the next phase of the project, the partners will optimise the solar reactor and assess the techno-economic potential of industrial scale implementation. The outcomes of SOLAR-JET will put Europe to the forefront of research, innovation and production of sustainable fuels directly from concentrated solar energy.

Story Source:  ETH Zürich