Interesting tech developments in nanotech, nanostructured materials, etc.
Ken Novak's Weblog
Tuesday, September 30, 2003
ST tackles alternative solar cells
: "The Franco-Italian semiconductor manufacturer ST Microelectronics (ST)
is developing alternative materials to make cheaper solar cells. ... The ST researchers are following two alternative approaches. The first is based on a so-called Graetzel cell (a device invented by Michael Graetzel of the Swiss Federal Institute of Technology in 1990), which uses a method similar in principle to photosynthesis. In the Graetzel cell, an organic dye absorbs light, while a nanoporous metal oxide layer transports electrons. Holes are transported in the reverse direction by a liquid electrolyte. Coffa says that ST is looking to replace these liquid electrolytes with a conductive polymer. "This could lead to further reductions in the cost per Watt, which is the key to making solar energy commercially viable," he said. The second idea that the ST researchers are working on is to use a mixture of fullerene and a copper-based organic compound sandwiched between the cell's two electrodes." More info on the ST site
. Also, a CNN article
quotes targets of $0.20 per watt. 11:24:08 AM
Thursday, September 25, 2003
Nanoscale iron as environmental cleanser: "An ultrafine, "nanoscale" powder made from iron, one of the most abundant metals on Earth, is turning out to be a remarkably effective tool for cleaning up contaminated soil and groundwater--a trillion-dollar problem that encompasses more than 1000 still-untreated Superfund sites in the United States, some 150,000 underground storage tank releases, and a staggering number of landfills, abandoned mines, and industrial sites.
Iron's cleansing power stems from the simple fact that it rusts, or oxidizes, explains [Lehigh University environmental engineer Wei-xian]Zhang. Ordinarily, of course, the only result is the familiar patina of brick-red iron oxide. But when metallic iron oxidizes in the presence of contaminants such as trichloroethene, carbon tetrachloride, dioxins, or PCBs, he says, these organic molecules get caught up in the reactions and broken down into simple carbon compounds that are far less toxic. Likewise with dangerous heavy metals..
[N]anoscale iron particles are some 10 to 1000 times more reactive than conventional iron powders, because their smaller size collectively gives them a much larger surface area, and they can be suspended in a slurry and pumped straight into the heart of a contaminated site like an industrial-scale hypodermic injection. Once there, the particles will flow along with the groundwater to work their decontamination magic in place--a vastly cheaper proposition than digging out the soil..
Laboratory and field tests have confirmed that treatment with nanoscale iron particles can drastically lower contaminant levels around the injection well within a day or two, and will all but eliminate them within a few weeks--reducing them so far that the formerly polluted site will now meet federal groundwater quality standards. The tests also show that the nanoscale iron will remain active in the soil for 6 to 8 weeks, says Zhang, or until what's left of it dissolves in the groundwater. And after that, of course, it will be essentially undetectable against the much higher background of naturally occurring iron.
Finally, says Zhang, the cost of the nanoscale iron treatments is not nearly as big a barrier as it was in 1995, when he and his colleagues first developed a chemical route for making the particles. Then the nanoscale iron cost about $500 a kilogram; now, it's more like $40 to $50 per kilogram. (Decontaminating an area of about 100 square meters using a single injection well requires 11.2 kilograms.) Zhang is currently forming a company to mass-produce the nanoscale iron particles. " Contact: (610)-758-5318, firstname.lastname@example.org. 11:28:47 AM
Monday, September 15, 2003
Economist update on Nanosys nanorod solar cells:
"Japan's leading maker of building materials, Matsushita Electric Works in Osaka. MEW, which is famous for its resin moulding and processing technology, has joined forces with Nanosys, a start-up co-founded by Dr Alivisatos in Palo Alto, California. The partners plan to develop nanorod composite cells for the construction materials industry in Asia. Nanosys and MEW (a subsidiary of Matsushita Electric Industrial, the world's largest consumer electronics maker) hope to release commercial versions of the new solar cells by 2007.
The plan is to incorporate the composite solar cells into decorative roofing tiles or sidings, says Stephen Empedocles, a co-founder and director of business development at Nanosys. .. Dr Alivisatos thinks that if he can get the nanorods to point in a single direction, rather than randomly, he can boost the composite's energy efficiency. If that can be increased to 10%, Nanosys will have the basics for producing solar cells that are easy to work with and cheap to make. In June, the National Science Foundation awarded Nanosys a research grant worth $850,000 to develop the nanocomposite solar cell further. " 4:39:24 PM
More light than heat
: "What is needed is a glass that lets in light but keeps out stifling heat. Such glasses exist but are generally considered a luxury .. One version consists of a thin layer of silver sandwiched between plates of ordinary glass.
Writing in a recent issue of Applied Physics Letters, Stefan Schelm and Geoff Smith of the University of Technology in Sydney, Australia, suggest a handy solution to the problem. The window they have developed consists of a sheet of plastic, rather than silver, sandwiched between plates of glass. The plastic, a standard polyvinyl butyral laminate is doped with nanoparticles of lanthanum hexaboride. This substance was chosen because it absorbs infra-red radiation but very little visible light. Because infra-red wavelengths carry the bulk of the heat, this allows the plastic layer to filter out most of the heat.
The nanoparticles do not even have to be particularly pure. Any contaminants created during production are so small, and fortunately transparent, as not to matter. The doped plastic transmits only 5% of the infra-red light, even when the concentration of nanoparticles is as low as 0.02%. The only side-effect is that the glass has a very slight blue-green tinge. .. Mr Schelm did not just happen upon lanthanum hexaboride, but chose it after modelling how conducting nanoparticles absorb light. By adjusting the size of the nanoparticles, or perhaps choosing a slightly different material, Mr Schelm may eventually get rid of the blue-green tinge." I wonder if this can be combined with concentrators and high-efficiency PVs -- like from spectrolabs, yielding >25% up to 400 suns -- to make PVs pay? 4:33:56 PM
Thursday, September 11, 2003
Sandia Nanocrystal Research Unraveling Nature's Secrets: ""Biominerals" is the term the team uses to describe complex natural materials that are composed of simple minerals, such as calcium, but that are organized in complex three-dimensional nanostructures. The team's first thrust was to uncover the mechanisms by which such complex crystals are induced into growing at selected sites. For instance, the biominerals in both macroscopic seashells and microscopic diatoms are synthesized in nature when the organism extracts dissolved ions of calcium and silicate from ocean water and uses proteins to reorganize them into nanostructures. "We've found that nature uses protein molecules to precisely control the orientation and morphology of biominerals. As a result, these materials are much stronger than normal man-made versions," said Voigt. .. 10:12:29 PM
Using computer models, the team designed simple experiments using organic molecules that bind to crystals, thereby directing and controlling their growth. By proving the concept in that way, Liu's team embarked on the long journey toward understanding how nature directs organic growth and translating that into a set of general rules guiding the manufacturing of atomically perfect nanomaterials. Currently the team is codifying its findings into a set of laboratory tools for controlling the delivery, diffusion and transport of the chemical "species" in its aqueous reaction chambers. The team plans to leverage Sandia's microfluidic platforms to provide a precise mechanism for altering the parameters of its experiments. The team predicts that its findings will result in manufacturing methodologies that are environmentally benign but that enable superior nanoparticles, nanowires and complexly nanostructured films. "
Booze to Fuel Gadget Batteries: St Louis University researchers create an alchohol-powered fuel cell using enzymes. "The team behind the new battery has produced a constant current from its biofuel cell that is still going strong after two months. .. Prior experiments have used methanol, another type of alcohol, as fuel. The Saint Louis team chose ethanol. "A big advantage is that ethanol is not toxic like methanol, so it is easier to deal with," said team leader and assistant professor of chemistry Shelley Minteer. ..
"The enzymes we use are called dehydrogenase," Akers said. "We chose these because they strip protons from alcohol, and this is the reaction we need to get electricity." Enzymes are not alive like cells or bacteria, but they have to be active for the biofuel cell to work. Keeping the sensitive catalysts active has caused problems in the past. "Enzymes are fairly fragile and can be denatured if there are any changes in temperature or in the pH level (acidity or alkalinity)," Minteer said. .. Minteer and her team overcame this conundrum by coating the biofuel cell's electrodes with a polymer that contains tailored micelles, or pores, which provide an ideal microenvironment for the enzymes to thrive. ..
Minteer said the team is working on ways to increase their biofuel cell's power density. Currently the team's battery can produce 2 milliwatts of power per effective square centimeter. The average cell phone requires 500 milliwatts to operate. The team is also looking at ways to produce a battery designed to fit today's portables that can also produce the necessary power output. "It's like a radiator in car," Akers said. "It's folded, and all those ridges and folds give it a high surface area so the effective surface area becomes tremendously huge. You can do this on a micro scale so that the effective surface area of the electrodes is enormous. This is what we are doing in the designing process."
Akers is confident the team will have a working prototype in a year, and that the finished product will hit store shelves a year later. " 9:53:47 PM
New technique for organic solar cells
: "researchers have pursued organic photovoltaic films for many years, but have been plagued with problems of efficiency, said [Princeton researcher] Forrest. The first organic solar cell, developed in 1986, was 1 percent efficient -- that is, it converted only 1 percent of the available light energy into electrical energy. "And that number stood for about 15 years," said Forrest.
Forrest and colleagues recently broke that barrier by changing the organic compounds used to make their solar cells, yielding devices with efficiencies of more than 3 percent. The most recent advance reported in Nature involves a new method for forming the organic film, which increased the efficiency by 50 percent. Researchers in Forrest's lab are now planning to combine the new materials and techniques. Doing so could yield at least 5 percent efficiency, which would make the technology attractive to commercial manufacturers. With further commercial development, organic solar devices would be viable in the marketplace with 5 to 10 percent efficiency, the researchers estimated. "We think we have pathway for using this and other tricks to get to 10 percent reasonably quickly," Forrest said. By comparison, conventional silicon chip-based solar cells are about 24 percent efficient. "Organic solar cells will be cheaper to make, so in the end the cost of a watt of electricity will be lower than that of conventional materials," said Peumans.
The technique the researchers discovered also opens new areas of materials science that could be applied to other types of technology, the researchers said. Solar cells are made of two types of materials sandwiched together, one that gives up electrons and another that attracts them, allowing a flow of electricity. The Princeton researchers figured out how to make those two materials mesh together like interlocking fingers so there is more opportunity for the electrons to transfer. The key to this advance was to apply a metal cap to the film of material as it is being made. The cap allowed the surface of the material to stay smooth and uniform while the internal microstructure changed and meshed together, which was an unexpected result, said Forrest. The researchers then developed a mathematical model to explain the behavior, which will likely prove useful in creating other micromaterials, Forrest said." 3:07:32 PM