Graphene saves the day again?'clumps' out radioactive waste from solution

Removing radioactive waste from water, especially in cases of nuclear disasters such as that in Fukushima, has been a cause of concern for long now, due to the multifold harmful effects that it has. But the wonder molecule, Graphene, again promises to be the savior, as researched by scientists from Houston's Rice University and Lomonosov Moscow State University, which causes radionuclides (that is the ions) to clump , which can be filtered off, making the water clean.

Presently , betonite and activated carbon are used to clean contaminated water, but graphene flakes are much more effective, due to their larger surface area. In a test, the one atom thick flakes were added to uranium and plutonium containing water, along with calcium and sodium (which actually hamper the cleaning process). Graphene was still able to condense out the toxins, irrespective of pH of water.

(left vial containing graphene flakes in solution, right vial with
clumping having occurred)

“Where you have huge pools of radioactive material, like at Fukushima, you add graphene oxide and get back a solid material from what were just ions in a solution,” said Rice chemist James Tour, heading the reasearch, along with moscow's Stepan Kalmikov. “Then you can skim it off and burn it. Graphene oxide burns very rapidly and leaves a cake of radioactive material you can then reuse.”"Graphene oxide’s large surface area defines its capacity to adsorb toxins, Kalmykov said. “So the high retention properties are not surprising to us,” he said. “What is astonishing is the very fast kinetics of sorption, which is key."

This research could surely prove to be a boon for people of areas living near nuclear plants, and disaster struck areas as well,  with graphene providing a cheap, biodegradable  solution to the polluted water problem


Source: Rice University via Gizmag

Stanford University creates peel-and-stick solar cells

Traditionally, thin-film solar cells are made with rigid glass substrates, limiting their potential applications. Flexible versions do exist, although they require special production techniques and/or materials. Now, however, scientists from Stanford University have created thin, flexible solar cells that are made from standard materials – and they can applied to just about any surface, like a sticker.

To make the peel-and-stick cells, the researchers started by applying a 300-nanometer layer of nickel onto a rigid silicon/silicon dioxide wafer. Using standard fabrication techniques, thin-film solar cells were then deposited onto the nickel. A protective polymer was then applied over the cells, followed by a layer of thermal release tape being applied over it.

The resulting sandwich of material was then submerged in room-temperature water and one edge of the tape was peeled back, letting water seep in between the nickel layer and the wafer. Once the nickel completely separated from the wafer, the researchers were left with a bare wafer, and the tape with everything else still clinging to it.

The tape and its contents were then heated to 90ºC (194ºF) for several seconds, adhesive was applied to the non-tape side, and the whole thing was applied to a chosen surface. When the tape was subsequently peeled off, all that was left were the polymer-covered cells, adhered like a decal.

The cells have been successfully applied to a variety of both flat and curved surfaces – including glass, plastic and paper – without any loss of efficiency.

Not only does the new process allow for solar cells to applied to things like mobile devices, helmets, dashboards or windows, but the stickers are reportedly both lighter and less costly to make than equivalent-sized traditional photovoltaic panels. There’s also no waste involved, as the silicon/silicon dioxide wafers can be reused.

According to assistant professor of mechanical engineering Xiaolin Zheng, the process could likely also be used to create peel-and-stick thin-film electronics, such as printed circuits or LCDs.

“Obviously, a lot of new products – from 'smart' clothing to new aerospace systems – might be possible by combining both thin-film electronics and thin-film solar cells,” she said. “And for that matter, we may be just at the beginning of this technology. The peel-and-stick qualities we're researching probably aren't restricted to Ni/SiO2 [nickel/silicon dioxide]. It's likely many other material interfaces demonstrate similar qualities, and they may have certain advantages for specific applications. We have a lot left to investigate.”

A paper on the research was published this Thursday in the journalScientific Reports.

Source: Stanford University , Gizmag

Ibasei's Cappa provides hydroelectricity on a small scale

The Cappa compact hydropower generator can deliver 250 W of electricity

Despite being the most widely used form of renewable energy worldwide, hydroelectricity is generally reserved for large-scale commercial installations built around massive dams. Japanese company Ibasei has shrunk things down and removed the need to build a dam with its Cappa compact hydropower generator – a system that's designed to be installed along a river or waterway.

The basic design of the Cappa is nothing new – blades rotate as the water flows through the unit, which drives a turbine to generate electricity. However, the unit is encased in a special diffuser that is designed to increase the velocity of the water at the point where it passes over the blades, thereby increasing the unit’s electrical output.
A company spokesman tells DigInfo that a water flow of 2 m/s (6.5 ft/s) will see one unit produce 250 W of electricity, while five units together will generate about 1 kW, taking control losses into account. The unit produces 100 V AC electricity at 50/60 Hz, so it can be used to power appliances around the home. The unit itself is also 100 percent recyclable and has an uptime of virtually 100 percent.

While you’d need quite a few of these things to completely power the average household – and I don’t know a lot of people with steadily flowing rivers running through their backyards, Ibasei anticipates the device could come in handy for providing power to remote communities and tourist attractions and in the event of natural disasters – floods in particular seem like a good fit for the technology.
While larger blades have the potential to deliver more power, their optimum size is determined by the size, width and speed of the river in which they are placed. For this reason, Ibasei would like to survey each river in which a unit is to be placed to customize a system for each customer.
The company is currently in the final development and testing stage and hopes to have the Cappa available for purchase in 2013. The 250 W model is expected to be priced at around the cost of a compact car.
Source: DigInfo TV , Gizmag

Plant root used to create eco-friendly lithium-ion battery

Researchers have used a dye extracted from the root of the madder plant to develop a new 'green' lithium ion battery (Photo: Carstor viaWikimedia Commons)

Researchers have found an eco-friendly alternative to the metal ores currently favored in the electrodes of lithium-ion batteries. The new non-toxic and sustainable battery uses purpurin, a red/yellow dye extracted from the root of the madder plant that has been used for dying cloth for at least 3,500 years – meaning the substance can simply be grown rather than mined.

Currently, lithium cobalt oxide (LiCoO₂) is the material of choice for forming the cathode in Li-ion batteries. However, mining the cobalt and combining it with lithium at high temperatures to form the cathode is an expensive and energy-intensive process.

Couple this with the energy used to extract the cobalt at the recycling stage and Dr. Arava Leela Mohana Reddy from Rice University says that for every kilowatt-hour of energy in a Li-ion battery, production and recycling pumps an estimated 72 kg (159 lb) of carbon dioxide into the atmosphere.

Dr. Reddy, along with Rice University colleagues and researchers from The City College of New York and the U.S. Army Research Laboratory, found that purpurin and other biologically based color molecules offer great potential as a more environmentally friendly alternative. This is due to the carbonyl and hydroxyl groups in the molecules that are adept at passing electrons back and forth.

“These aromatic systems are electron-rich molecules that easily coordinate with lithium,” explained City College Professor of Chemistry, George John.

Making the purpurin electrode can be done at room temperature in a simple process which involves dissolving the purpurin in an alcohol solvent and adding lithium salt. After the solution turns from reddish yellow to pink, indicating the salt’s lithium ions have bonded with the purpurin, the solvent can be removed and the electrode is ready.

The team claims the purpurin is less complicated to use than the one or two other organic molecules being examined for use in batteries. Additionally, growing madder or other biomass crops would help remove carbon dioxide from the atmosphere. The resulting batteries would also be non-toxic, making them easier to dispose of.

Using purpurin, with 20 percent carbon added to improve conductivity, the research team built a half-battery cell with a capacity of 90 milliamp hours per gram after 50 charge/discharge cycles.

The researchers are confident their green Li-ion battery will be commercially produced in the next few years. This takes into account the time needed to improve purpurin’s efficiency or find and synthesize similar molecules.

“We can say it is definitely going to happen, and sometime soon, because in this case we are fully aware of the mechanism,” said Professor John.

The team’s research appears in Nature’s online and open access publication, Scientific Reports.

Source: City College of New York, Rice University

Nano-sandwich material claimed to boost solar cell efficiency by 175 percent

The nanoscale metal mesh that makes up the top layer of the sandwich-like PlaCSH material

One of the main reasons that solar cells aren’t more efficient at converting sunlight into electricity is because much of that sunlight is reflected off the cell, or can’t be fully absorbed by it. A new sandwich-like material created by researchers at Princeton University, however, is claimed to dramatically address that problem – by minimizing reflection and increasing absorption, it reportedly boosts the efficiency of organic solar cells by 175 percent.

Developed by a team led by electrical engineer Prof. Stephen Chou, the material is known as a “plasmonic cavity with subwavelength hole array” or PlaCSH.

It consists of five very thin layers. On top is the “window layer” through which the sunlight first passes. It’s made from an extremely fine metal mesh, the diameter and spacing of its holes being measured in nanometers. Next is a layer of transparent plastic, followed by a layer of semiconductive material – although Chou used a plastic semiconductor, other materials could be used. This is followed by a layer of titanium oxide, with a layer of aluminum sitting at the bottom of the stack.

The combined thickness of all five layers is just 230 nanometers. This distance, along with the spacing and diameter of the holes in the mesh, is shorter than the wavelength of the sunlight itself. According to Chou, it is this property that allows only four percent of the light to be reflected, and up to 96 percent to be absorbed.

When it comes to converting direct sunlight into electricity, this translates into a 52 percent increase in efficiency over conventional organic solar cells. PlaCSH is also superior at capturing sunlight coming at steep angles, however. This ups its efficiency by an additional 81 percent, which when combined with other factors brings the total percentage of improvement to 175.

A comparison of sunlight reflected off a conventional organic solar cell and one using PlaCSH

PlaCSH could reportedly be cost-effectively manufactured in large sheets. Besides providing greater efficiency, the material could also replace the costly indium-tin-oxide (ITO) electrodes in conventional organic solar cells, bringing their price down. As PlaCSH is more flexible than ITO, it should also make the cells less fragile.

Although Chou’s research regarding the use of PlaCSH in inorganic solar cells is not yet complete, he believes that the material should also allow them to achieve much greater efficiency. Additionally, because it could supposedly reduce the thickness of the silicon semiconductor in such cells by a thousand-fold, it should make them cheaper and more flexible.

A paper on the research was recently published in the journal Optics Express.

Source: Princeton University , Gizmag

Australian researchers develop promising new approach to hydrogen storage

Scientists at the University of New South Wales (UNSW), Australia, are developing a novel way to store hydrogen that could help turn it into a viable portable fuel source. The research centers on using synthesized nanoparticles of the compound sodium borohydride (NaBH₄ for those who love chemistry), which when encased inside nickel shells exhibits surprising and practical storage properties including the ability to reabsorb hydrogen and release it at much lower temperatures than previously observed, making it an attractive proposition for transport applications.

Hydrogen is a clean burning fuel that can be extracted from sources including natural gas, biomass, coal and water. One of the major problems in making it a viable alternative fuel is storage – the atoms are so tiny that they can easily escape from many kinds of containers. Also, hydrogen is more volatile than petrol. It can burn like blazes and can react badly to other substances. As no one wants to have a car that can burst into flames when you switch on the engine, this problem has drawn the attention of scientists around the world.

When researchers from the UNSW Materials Energy Research Laboratory synthesized nanoparticles of the sodium borohydride and encased these inside nickel shells, the findings took them by surprise. Borohydrides (including lithium and sodium compounds) are known to be effective storage materials, but it was believed that once the energy was released it could not be reabsorbed. As a result, there has been little focus on sodium borohydride.

The new findings indicate that by controlling the size and architecture of these structures, their properties can be made reversible. In other words, NaBH4 absorbs the hydrogen like a sponge and then releases it, making it useful for application in vehicles. In its bulk form, sodium borohydride requires temperatures above 550°C just to release hydrogen. It’s pretty much the same even on the nano-scale, but this core-shell nanostructure saw energy release happening at just 50°C, and significant release at 350°C.

Dr Kondo-Francois Aguey-Zinsou from the School of Chemical Engineering at UNSW says this is a real breakthrough and his team hopes to have it commercialized in three to five years’ time. “No one has ever tried to synthesize these particles at the nanoscale because they thought it was too difficult, and couldn’t be done," he said. "We’re the first to do so, and demonstrate that energy in the form of hydrogen can be stored with sodium borohydride at practical temperatures and pressures.’’

The findings are published in the Journal ACS Nano.

Source: UNSW , Gizmag

The streets of Vancouver are paved with ... recycled plastic

According to the Economist Intelligence Unit's latest Global Liveability Report, the beautiful city of Vancouver in Canada is a pretty decent place to live, ranking third in the world. Its environmental footprint is currently unsustainable, though, prompting officials to hatch an ambitious plan to have Vancouver crowned the greenest city in the world by 2020. Helping things along nicely is a new warm mix paving process that makes use of the kind of waste plastic placed in blue household recycling boxes by conscientious citizens, reducing greenhouse gases and improving air quality along the way.

A team of city officials, including Peter Bremner and Jeff Markovic from Kent Services, has been working with Toronto's GreenMantra to develop an innovative new process that coverts 100 percent post-consumer recycled plastic waste into a wax that can be mixed into warm mix asphalt.

"Warm mix asphalt is not all that new, but what is unique in our application is using a wax that was derived from recycled plastics," Karyn Magnusson from Vancouver's Engineering Services told Gizmag. "We have been trialing warm mix since 2008 with different kinds of additives designed to reduce the viscosity to make placement easier at lower temperatures. We have now paved three sections of Vancouver roads with this latest trial."

"The mix was a 19 mm Superpave, surface coarse warm-mix, with 20 percent reclaimed asphalt pavement and wax derived from blue box plastics," added Markovic. "The temperature was reduced from our typical 320°F [160ºC] to 250°F [121ºC], there's a significant reduction in VOC and CO readings at the plant, and visible reductions in fumes at the both the paver and the plant."

Other benefits revealed in the lab and road trials include 20 percent savings on gas used to heat the mix. Additionally, the City of Vancouver says that there is potential for additional grinding and re-using cycles of pavement, as the wax helps prevent aging of asphaltic oils. Mixing at lower temperatures allows for increased use of recycled asphalt content and lower use of virgin asphaltic oils.

"Paving season is now coming to a close, but next spring we will do some more trials and go back to look at the in-situ performance of the placed material," said Magnusson. "We have some work to do yet evaluating this trial, but if our testing continues to show the benefits we were anticipating then we would love to embrace this as the norm rather than as a special mix. Ideally we will also see somebody begin to produce this wax locally. The material we have used to date was created by a company in Toronto, it would be nice to see Vancouver plastic waste going into Vancouver roads."

Although the new development currently carries a three percent premium over typical hot mix, the developers believe this extra cost will disappear in the near future as a result of an ample supply of waste plastics.

Source: City of Vancouver , Gizmag