Contact: Lynn Yarris (510) 486-5375; [email protected]
Berkeley Lab scientists delivered more than 100 presentations at the American Chemical Society’s Spring 2009 national meeting in Salt Lake City which took place March 22-29, 2009. Below are some of the highlights reported by Lab during the week of the meeting.
Catalysis Past, Present and Future
Given Energy Secretary Steve Chu’s announcement of $1.2 billion in American Recovery and Reinvestment Act funds to catalyze research in DOE’s Office of Science, it was fitting that catalysis was a major focus for the first full day of the ACS Spring 2009 national meeting. It’s been said that a society’s standard of living can be measured by the sophistication of its catalytic technologies. This is because all manufacturing processes (and most biological ones) start off with a catalyst – a substance that speeds up or slows down a chemical reaction without itself participating in the reaction. Several ACS sessions on Monday were devoted to catalysis and making multiple presentations was one of Berkeley’s finest.
Gabor Somorjai, a chemist who holds joint appointments with Berkeley Lab and UC Berkeley, has been called the “father of modern catalysis,” and his accomplishments have earned him a plethora of awards including the National Medal of Science, American’s highest scientific achievement. Somorjai opened Monday’s proceedings with what was essentially a retrospective on the advances in catalysis and surface chemistry (all catalysis takes place on the surfaces of materials) that have been made over the past several decades through the combined efforts of theorists and experimentalists.
“Experimental discoveries were followed by theoretical interpretations of these discoveries that in turn paved the way for further advances by experimentalists,” Somorjai said. “This was a pattern that generated enormous advances in surface chemistry and catalysis.”
Among the examples that followed this pattern cited by Somorjai was the experimental discovery of the chemical reactivity that occurs around surface defects. In their work to explain this phenomenon, theorists gained an understanding of the electronic structure of active sites in catalysis. This led experimentalists to find promising combinations of catalyst formulation on transition metal surfaces. Somorjai was speaking at a symposium to honor Jens Nørskovs, a chemist at the University of Denmark and winner of the Gabor A. Somorjai Award for Creative Research in Catalysis.
Somorjai also addressed another symposium on the future of nanocatalysis. In a talk entitled, “The nanoscience revolution of catalysis science,” Somorjai noted that all catalysts are nanoparticles. “Nature is telling us something, if you want to do effective catalysis you must work with nanoparticles,” he said.
There have been three revolutions in catalysis over the past 100 years, Somorjai said, starting with the synthesis of industrial ammonia – the “Alwin Mittasch” catalyst – at the start of the 20th century, the advent of the industrial reforming catalyst at the century’s midway point, and now the nanoscience revolution, where understanding of chemistry at the molecular level is pointing the way to catalysis by design. Somorjai’s own crystal ball seems to be telling him that dendrimers – those branched molecules that resemble a worm’s eye view of a tree’s root system – hold the key to the future of catalysis.
“Dendrimers represent a new way of doing catalysis,” Somorjai said, explaining that under the right condition, when a nanoparticle is encapsulated within the branches of a dendrimer, the branches will catalyze the nanoparticle’s growth.
Somorjai also had advice for students interested in a future career in nanocatalysis. For too long, he said, students have specialized in only one of the key aspects of catalysis research – characterization, reaction turnover or selectivity. Somorjai called for future graduate and postdoctoral students to combine all of three aspects into a unified field of study. He dubbed this new field: “Homo Catalyticus.”
Somorjai also used his crystal ball to predict the fabrication of “core shell structures” in which metal nanoparticles are surrounded by an inorganic cap of mesoporous silica or some other oxide to provide higher thermal stability. He also predicted that selectivity in catalytic reactions, which is demanded by green chemistry to eliminate undesirable byproducts, will require the use of controlled nanoparticle catalyst fabrication with highly selective size and shape.
“This will revolutionize catalyst fabrication technology and promises to be an important direction of research in the 21st Century,” Somorjai predicted.
Berkeley Lab Goes to the ACS Awards Symposia Day
Awards symposia were in the spotlight on Tuesday at the ACS Spring 2009 national meeting and Berkeley Lab was well represented by a trio of scientists who know more than a little something about award-winning research. Berkeley Lab physical chemist Graham Fleming gave the Joel Henry Hildebrand Award Address on the “Theoretical and Experimental Chemistry of Liquids.” His theme was the dynamics of liquids and polar salvation, but his message was “Time-scales time-scales time-scales!” In discussing his own research over the past 25 years, significant progress was made thanks to the development of increasingly sophisticated optical spectroscopy technologies operating at increasingly faster time-scales. As a prime example, Fleming cited his studies of the enna-Matthews-Olson (FMO) photosynthetic light-harvesting protein, using a spectroscopy technique his group developed that works on a femtosecond time-scale (millionth of a billionth of a second). These studies revealed that nature’s long-held secret behind the ability to instantaneously transfer energy from one molecular system to another during photosynthesis was quantum mechanics.
Berkeley Lab chemist Richard Saykally began his Peter Debye Award in Physical Chemistry address with a jolt of classical music blasting from an amplified speaker. By way of explanation, Saykally said his experiences teaching freshmen chemistry classes the day before the start of Spring break had prepared him well for giving an end-of-the-day talk. Saykally’s theme was “X-ray absorption spectroscopy of liquid microjets: A new probe of ion hydration.” Again employing various types of music for emphasis, he explained how the incorporation of liquid microjet technology into soft X-ray spectroscopy experiments has provided critical new insights into the nature of ions in liquid water. You would think that if chemists could agree upon anything it would be water but no – there’s been a long-standing argument as to how water molecules arrange themselves in a liquid drop. Saykally and his collaborators, using theory combined with experiments that capitalized on the ultrabright x-ray beams at Berkeley Lab’s Advanced Light Source, have provided strong support for what is called the continuum model of water, in which the hydrogen bonds in liquid water are continually breaking and reforming and moving around. His work would seem to have ended the controversy once and for all but then Saykally concluded his talk with another blast of music – the Beatles’ song “Lies!” “Everything I have just told you could be a complete lie,” he said when the music stopped, explaining that interpretations of experimental results are based on theories that for the nature of ions in water remain incomplete.
For pure inspiration to students and young scientists who happen to be female, the true highlight of the day surely came from Berkeley Lab nuclear chemist Darleane Hoffman who discussed the progress women have made in chemistry over the past 60 years as personally witnessed by her. Hoffman, a protégé of the late great Glenn Seaborg and only the second woman ever to win the Priestly Award, the ACS’ highest honor, was speaking at a symposium for Mary Singleton, a retired chemist from Lawrence Livermore National Laboratory, who was the recipient of this year’s ACS Award for Encouraging Women into Careers in the Chemical Sciences. The room was packed with women who – judging by the applause before and after her talk – were admirers of Hoffman.
When she began her graduate studies in 1948 at Iowa State University, Hoffman said she and other women were referred to as “loophole chemists” because during World War II, the shortage of men resulted in women being recruited into non-traditional fields, including the sciences. Before the war, she noted woman teachers in public schools and universities had to resign if they married. Hoffman was able to take advantage of the fact that the newness of the nuclear chemistry field made it easier to break into and an “old boys club” had yet to be established.
Hoffman presented statistics showing that whereas 60 years ago, less than 14-percent of the students receiving B.S. degrees in chemistry, and only 4-percent of those earning PhDs were women. Today those figures are closer to 51-percent and 34-percent respectively. And yet, she pointed out, today women fill less than 15-percent of tenure-track positions at the top 50 universities!
“Academia has been slow to change,” Hoffman said. She encouraged women of the ASC to be good mentors to their students and junior colleagues, supportive of their peers and seek out and nominate qualified women and minorities for awards, honors and advancement. “Such recognitions lead to positions of leadership and as women we need to create a critical mass in leadership,” Hoffman concluded.
Smaller and Smaller, Faster and Faster: Nanocrystal Solar Cells, Biomimetic Nanpatterns, and Attosecond Beamlines
Applying nanocrystals to solar energy, borrowing from nature to direct the construction of nanostructures, and the study of nanoparticles in action with bursts of light almost too fast for comprehension were among the Berkeley Lab highlights on Wednesday at the American Chemical Society’s national meeting in Salt Lake City.
Berkeley Lab interim director Paul Alivisatos led off the symposium on New Developments in Energy Conversion and Light-Harvesting with a talk entitled: “Multicomponent nanocrystals for solar photovoltaics and photocatalysts.”
In this talk he described how the ability to control the composition and spatial arrangements of interconnected nanocrystals has substantially improved in recent years.
“It is now possible to prepare multi-component nanoparticles with designed optical and electronic properties, and with defined topologies,” he said.
Alivisatos focused on two specific designs, one for a nanoparticle-based photovoltaic system, and one for a photocatalyst. The photovoltaic system consisted of a cadmium sulfide/copper sulfide segmented nanorod. The photocatalyst consisted of a cadmium sulfide tetrapod with particles of platinum deposited on the ends. In both cases, he said, the nanocrystals performed better than would have been expected based on conventional scientific wisdom which holds that granularity as a result of using nanocrystals in thin film solar cells leads to the trapping of electrical charges, which in turn degrades the film’s performance.
Alivisatos said that a review of the literature shows the research into potential photovoltaic materials that began in the 1960s collapsed into a very narrow focus in the aftermath of the 1970s oil crisis because people were looking for a quick fix to the energy problem. This time, he said, “Let’s be more patient and not rush to judgment until we have a better understanding of these materials.”
Berkeley Lab chemist and acclaimed nanoscientist Peidong Yang followed the Alivisatos talk with a discussion on semiconductor nanowires for solar energy harvesting.
Semiconductor nanowires represent an important class of nanostructure building block for photovoltaics as well as for direct solar-to-fuel applications because of their high surface area, tunable bandgap and efficient charge transport and collection, Yang said. His lab has been testing semiconductor nanowires as both a means of harvesting solar energy in a solar cell and a means of splitting water molecules – converting sunlight into hydrogen through water splitting is one of the most promising clean, sustainable and renewable alternatives to fossil fuels and is now considered to be the new Holy Grail of chemistry. The successes of the Yang group with nanowires fashioned from alloys, such as indium gallium nitride, bolster Alivisatos’ call for patience and suggest that such patience will be rewarded.
James De Yoreo of The Molecular Foundry, a national DOE nanoscience center located at Berkeley Lab, spoke at the symposium on Chemical Methods of Nanofabrication. His talk, titled “Using biomimetics as nanostructure templates,” described the use of proteins as scaffolds upon which the fabrication of inorganic nanostructures can be templated.
“At the Molecular Foundry efforts are underway to mimic nature’s strategy by creating nanometer-scale chemical templates, which direct the organization of engineered macromolecules and complexes, such as RNA, proteins and viruses, into micron-scale patterns,” De Yoreo said.
De Yoreo illustrated his talk with videos embedded in power points that often resembled wind-blown grains of sand sweeping across a desert surface but were actually molecular-scale resolution images showing inorganic crystal growth across a peptide surface. De Yoreo concluded his talk as he began it by reminding his audience that The Molecular Foundry is a national user facility and its unique capabilities are available to all qualified researchers.
In the blink of an eye, more attoseconds have expired than the age of Earth measured in – minutes. A lot more. To be precise, an attosecond is one billionth of a billionth of a second. Hard as that may be to wrap your mind around, the attosecond time-scale is where you’ll find the electron action that is the starting point of all of chemistry. Not surprisingly, chemists are most eager to explore it. Berkeley Lab chemist and director of its Chemical Sciences Division Dan Neumark described a collaborative effort with Berkeley Lab’s Steve Leone to develop an attosecond beamline at Berkeley Lab’s Advanced Light Source.
“Our goal is to apply the new capabilities of this beamline to the study of attosecond dynamics in molecules and clusters, thus building on the atomic experiments done in other laboratories,” Neumark said.
After describing how to achieve attosecond pulses of light and detailing some successful experiments with metal nanoparticles and small molecular systems, Neumark left his audience with this promise: “More experiments in the attosecond time-scale are on the way!”