Hydrogen could be a clean, abundant energy source, but it’s difficult to store in bulk. In new research, materials scientists at Rice University have made the surprising discovery that tiny carbon capsules called buckyballs are so strong they can hold volumes of hydrogen nearly as dense as those at the center of Jupiter.

“Based on our calculations, it appears that some buckyballs are capable of holding volumes of hydrogen so dense as to be almost metallic,” said lead researcher Boris Yakobson, professor of mechanical engineering and materials science at Rice. “It appears they can hold about 8 percent of their weight in hydrogen at room temperature, which is considerably better than the federal target of 6 percent.”

The Department of Energy has devoted more than $1 billion to developing technologies for hydrogen-powered automobiles, including technologies to cost-effectively store hydrogen for use in cars. Hydrogen is the lightest element in the universe, and it is very difficult to store in bulk. For hydrogen cars to be competitive with gasoline-powered cars, they need a comparable range and a reasonably compact fuel system. It’s estimated that a hydrogen-powered car with a suitable range will require a storage system with densities greater than those found in pure, liquid hydrogen.

Yakobson said scientists have long argued the merits of storing hydrogen in tiny, molecular containers like buckyballs, and experiments have shown that it’s possible to store small volumes of hydrogen inside buckyballs. The new research by Yakobson and former postdoctoral researchers Olga Pupysheva and Amir Farajian offers the first method of precisely calculating how much hydrogen a buckyball can hold before breaking.

Buckyballs, which were discovered at Rice more than 20 years ago, are part of a family of carbon molecules called fullerenes. The family includes carbon nanotubes, the typical 60-atom buckyball and larger buckyballs composed of 2,000 or more atoms.

“Bonds between carbon atoms are among the strongest chemical bonds in nature,” Yakobson said. “These bonds are what make diamond the hardest known substance, and our research showed that it takes an enormous amount of internal pressure to deform and break the carbon-carbon bonds in a fullerene.”

Using a computer model, Yakobson’s research team has tracked the strength of each atomic bond in a buckyball and simulated what happened to the bonds as more hydrogen atoms were packed inside. Yakobson said the model promises to be particularly useful because it is scalable, that is it can calculate exactly how much hydrogen a buckyball of any given size can hold, and it can also tell scientists how overstuffed buckyballs burst open and release their cargo.

If a feasible way to produce hydrogen-filled buckyballs is developed, Yakobson said, it might be possible to store them as a powder.

“They will likely assemble into weak molecular crystals or form a thin powder,” he said. “They might find use in their whole form or be punctured under certain conditions to release pure hydrogen for fuel cells or other types of engines.”

The research appears on the March 2008 cover of the American Chemical Society’s journal Nano Letters.

The research was supported by the Office of Naval Research and the Department of Energy.

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University of Saskatchewan Canada Research Chair John Tse and colleagues in Germany have identified a new family of superconductors – research that could eventually lead to the design of better superconducting materials for a wide variety of industrial uses.

In an article published in the journal Science, the team has produced the first experimental proof that superconductivity can occur in hydrogen compounds known as molecular hydrides.

“We can show that if you put hydrogen in a molecular compound and apply high pressure, you can get superconductivity,” said Tse. “Validation of this hypothesis and understanding of the mechanism are initial steps for design of better super-conducting materials.”

Superconductors conduct electricity without creating friction or heat loss. An electric current can therefore flow in a loop of superconducting wire indefinitely with no power source. Examples of existing superconducting materials include magnets used in MRI machines and the magnets that enable high-speed trains to float above the track without friction or energy loss as heat.

Team member Mikhail Eremets of the Max Plank Institute in Germany did the laboratory work in detecting superconductivity in the hydrogen compound silane, while Tse and his graduate student Yansun Yao provided the theoretical basis for understanding the mechanism involved and identified the key chemical structures.

Most commercial superconducting materials have to operate at very low temperatures which requires expensive super-cooling equipment.

“Our research in this area is aimed at improving the critical temperature for superconductivity so that new superconductors can be operated at higher temperatures, perhaps without a refrigerant,” said Tse.

It has long been hypothesized that hydrogen, the simplest of the elements, may be able to conduct electricity without creating friction or heat loss (superconductive behavior) if it’s compressed into a very dense solid form. Though many researchers have tried using pure hydrogen, they have not been able to achieve the necessary hydrogen density to produce superconductivity.

Instead of using pure hydrogen, the Germany-Canada team, following an earlier suggestion by Prof. Neil Ashcroft at Cornell University, compressed hydrogen-rich molecules (hydrides). They were able to reach the necessary density for superconductivity at much lower pressure than with pure hydrogen – an achievement that will shed greater understanding on the fundamental nature of superconductivity.

The U of S work, funded by NSERC and the Canada Research Chairs program, involved extensive calculations – some taking as long as a month – at the WestGrid computing facility and with the Canada Foundation for Innovation-funded high-performance computing facility at the U of S.

In related research, Tse’s team is using the Canadian Light Source synchrotron to study high pressure structures of other hydrides systems on potential superconductivity and making use of them to store hydrogen for fuel cells.

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Crop scientists have cloned a gene that controls the shape of tomatoes, a discovery that could help unravel the mystery behind the huge morphological differences among edible fruits and vegetables, as well as provide new insight into mechanisms of plant development.

The gene, dubbed SUN, is only the second ever found to play a significant role in the elongated shape of various tomato varieties, said Esther van der Knaap, lead researcher in the study and assistant professor of horticulture and crop science at Ohio State University’s Ohio Agricultural Research and Development Center (OARDC) in Wooster.

One of the most diverse vegetable crops in terms of shape and size variations, tomatoes have evolved from a very small, round wild ancestor into the wide array of cultivated varieties — some large and segmented, some pear-shaped, some oval, some resembling chili peppers — available through most seed catalogs and for sale in supermarkets. However, very little is known about the genetic basis for such transformations in tomatoes, and virtually nothing has been discerned about morphological changes in other fruits and vegetables.

“Tomatoes are the model in this emerging field of fruit morphology studies,” van der Knaap pointed out. “We are trying to understand what kind of genes caused the enormous increase in fruit size and variation in fruit shape as tomatoes were domesticated. Once we know all the genes that were selected during that process, we will be able to piece together how domestication shaped the tomato fruit — and gain a better understanding of what controls the shape of other very diverse crops, such as peppers, cucumbers and gourds.”

One of the first pieces in van der Knaap’s fruit-development puzzle is SUN, which takes its name from the “Sun 1642″ cultivated variety where it was found — an oval-shaped, roma-type tomato with a pointy end. The gene also turned out to be very common in elongated heirloom varieties, such as the Poblano pepper-like “Howard German” tomato.

“After looking at the entire collection of tomato germplasm we could find, we noticed that there were some varieties that had very elongated fruit shape,” van der Knaap explained. “By genetic analysis, we narrowed down the region of the genome that controls this very elongated fruit shape, and eventually narrowed down that region to a smaller section that we could sequence to find what kind of genes were present at that location.

“In doing that,” van der Knaap continued, “we identified one key candidate gene that was turned on at high levels in the tomato varieties carrying the elongated fruit type, while the gene was turned off in round fruit. And after we confirmed that observation in several other varieties, we found that this gene was always very highly expressed in varieties that carry very elongated fruit.”

Once SUN was identified, the next step involved proving whether this gene was actually responsible for causing changes in fruit shape. To do so, van der Knaap and her team conducted several plant-transformation experiments. When the SUN gene was introduced into wild, round fruit-bearing tomato plants, they ended up producing extremely elongated fruit. And when the gene was “knocked out” of elongated fruit-bearing plants, they produced round fruit similar to the wild tomatoes.

“SUN doesn’t tell us exactly how the fruit-shape phenotype is altered, but what we do know is that turning the gene on is very critical to result in elongated fruit,” van der Knaap said. “We can now move forward and ask the question: Does this same gene, or a gene that is closely related in sequence, control fruit morphology in other vegetables and fruit crops?”

Something else van der Knaap and her team found out is that SUN encodes a member of the IQ67 domain of plant proteins, called IQD12, which they determined to be sufficient — on its own — to make tomatoes elongated instead of round during the plant transformation experiments.

IQD12 belongs to a family of proteins whose discovery is relatively new in the world of biology. So new that IQD12 is only the second IQ67 protein-containing domain whose function in plants has been identified. The other one is AtIQD1, discovered in the plant model Arabidopsis thaliana, which belongs to the same family as broccoli and cabbage. In Arabidopsis, AtIQD1 increases levels of glucosinolate, a metabolite that Ohio State researchers are studying in broccoli for its possible role in inhibiting cancer (http://researchnews.osu.edu/archive/goodbroc.htm).

“Unlike AtIQD1, SUN doesn’t seem to be affecting glucosinolate levels in tomato, since these metabolites are not produced in plants of the Solanaceous family (which includes tomato, peppers, eggplant and other popular crops),” van der Knaap explained. “But there appears to be a common link between the two genes, which is that they may be regulating tryptophan levels in the plant. Thus, SUN may be telling us more about the whole process of diversification in fruits and across plant species, perhaps through its impact on plant hormones and/or secondary metabolites levels.”

In the process of identifying and cloning SUN, van der Knaap’s team was also able to trace the origin of this gene and the process by which it came to reside in the tomato genome.

Another unique characteristic of the SUN gene is that it affects fruit shape after pollination and fertilization, with the most significant morphological differences found in developing fruit five days after plant flowering. The only other fruit-shape gene previously identified — OVATE, a discovery by Cornell University plant breeder Steven Tanksley, van der Knaap’s advisor while she was a post-doctoral associate there — influences the future look of a fruit before flowering, early in the ovary development.

The discovery was reported, as the cover article, in the March 14 issue of the journal Science.

Co-authors in the Science paper include Eric Stockinger, associate professor of horticulture and crop science at OARDC; Han Xiao, a postdoctoral researcher in horticulture and crop science at Ohio State; Ning Jiang, assistant professor of horticulture at Michigan State University; and Erin Schaffner, a former undergraduate student from the College of Wooster who conducted her independent study in van der Knaap’s lab.

Funding for this research came from the National Science Foundation (NSF).

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