Scientists Capture First Images of Molecules Before and After Reaction

May 30, 2013 — Every chemist's dream -- to snap an atomic-scale picture of a chemical before and after it reacts -- has now come true, thanks to a new technique developed by chemists and physicists at the University of California, Berkeley.

Using a state-of-the-art atomic force microscope, the scientists have taken the first atom-by-atom pictures, including images of the chemical bonds between atoms, clearly depicting how a molecule's structure changed during a reaction. Until now, scientists have only been able to infer this type of information from spectroscopic analysis.

"Even though I use these molecules on a day to day basis, actually being able to see these pictures blew me away. Wow!" said lead researcher Felix Fischer, UC Berkeley assistant professor of chemistry. "This was what my teachers used to say that you would never be able to actually see, and now we have it here."

The ability to image molecular reactions in this way will help not only chemistry students as they study chemical structures and reactions, but will also show chemists for the first time the products of their reactions and help them fine-tune the reactions to get the products they want. Fischer, along with collaborator Michael Crommie, a UC Berkeley professor of physics, captured these images with the goal of building new graphene nanostructures, a hot area of research today for materials scientists because of their potential application in next-generation computers.

"However, the implications go far beyond just graphene," Fischer said. "This technique will find application in the study of heterogeneous catalysis, for example," which is used widely in the oil and chemical industries. Heterogeneous catalysis involves the use of metal catalysts like platinum to speed reactions, as in the catalytic converter of a car.

"To understand the chemistry that is actually happening on a catalytic surface, we need a tool that is very selective and tells us which bonds have actually formed and which ones have been broken," he added. "This technique is unique out there right now for the accuracy with which it gives you structural information. I think it's groundbreaking."

"The atomic force microscope gives us new information about the chemical bond, which is incredibly useful for understanding how different molecular structures connect up and how you can convert from one shape into another shape," said Crommie. "This should help us to create new engineered nanostructures, such as bonded networks of atoms that have a particular shape and structure for use in electronic devices. This points the way forward."

Fischer and Crommie, along with other colleagues at UC Berkeley, in Spain and at the Lawrence Berkeley National Laboratory (LBNL), published their findings online May 30 in the journal Science Express.

From shadow to snapshot

Traditionally, Fischer and other chemists conduct detailed analyses to determine the products of a chemical reaction, and even then, the actual three-dimensional arrangement of atoms in these products can be ambiguous.

"In chemistry you throw stuff into a flask and something else comes out, but you typically only get very indirect information about what you have," Fischer said. "You have to deduce that by taking nuclear magnetic resonance, infrared or ultraviolet spectra. It is more like a puzzle, putting all the information together and then nailing down what the structure likely is. But it is just a shadow. Here we actually have a technique at hand where we can look at it and say this is exactly the molecule. It's like taking a snapshot of it."

Fischer is developing new techniques for making graphene nanostructures that display unusual quantum properties that could make them useful in nano-scale electronic devices. The carbon atoms are in a hexagonal arrangement like chicken wire. Rather than cutting up a sheet of pure carbon -- graphene -- he hopes to place a bunch of smaller molecules onto a surface and induce them to zip together into desired architectures. The problem, he said, is how to determine what has actually been made.

That's when he approached Crommie, who uses atomic force microscopes to probe the surfaces of materials with atomic resolution and even move atoms around individually on a surface. Working together, they devised a way to chill the reaction surface and molecules to the temperature of liquid helium -- about 4 Kelvin, or 270 degrees Celsius below zero -- which stops the molecules from jiggling around. They then used a scanning tunneling microscope to locate all the molecules on the surface, and zeroed in on several to probe more finely with the atomic force microscope. To enhance the spatial resolution of their microscope they put a single carbon monoxide molecule on the tip, a technique called non-contact AFM first used by Gerhard Meyer and collaborators at IBM Zurich to image molecules several years ago.

After imaging the molecule -- a "cyclic" structure with several hexagonal rings of carbon that Fischer created especially for this experiment -- Fischer, Crommie and their colleagues heated the surface until the molecule reacted, and then again chilled the surface to 4 Kelvin and imaged the reaction products.

"By doing this on a surface, you limit the reactivity but you have the advantage that you can actually look at a single molecule, give that molecule a name or number, and later look at what it turns into in the products," he said.

"Ultimately, we are trying to develop new surface chemistry that allows us to build higher ordered architectures on surfaces, and these might lead into applications such as building electronic devices, data storage devices or logic gates out of carbon materials."

The research is coauthored by Dimas G. de Oteyza, Yen-Chia Chen, Sebastian Wickenburg, Alexander Riss, Zahra Pedramrazi and Hsin-Zon Tsai of UC Berkeley's Department of Physics; Patrick Gorman and Grisha Etkin of the Department of Chemistry; and Duncan J. Mowbray and Angel Rubio from research centers in San Sebastián, Spain. Crommie, Fischer, Chen and Wickenburg also have appointments at Lawrence Berkeley National Laboratory.

The work is sponsored by the Office of Naval Research, the Department of Energy and the National Science Foundation.

Facebook Profiles Raise Users' Self-Esteem and Affect Behavior+

May 31, 2013 — A Facebook profile is an ideal version of self, full of photos and posts curated for the eyes of family, friends and acquaintances. A new study shows that this version of self can provide beneficial psychological effects and influence behavior.

Catalina Toma, a UW-Madison assistant professor of communication arts, used the Implicit Association Test to measure Facebook users' self-esteem after they spent time looking at their profiles, the first time the social psychology research tool has been used to examine the effects of Facebook. The test showed that after participants spent just five minutes examining their own Facebook profiles, they experienced a significant boost in self-esteem. The test measures how quickly participants associate positive or negative adjectives with words such as me, my, I and myself.

"If you have high self-esteem, then you can very quickly associate words related to yourself with positive evaluations but have a difficult time associating words related to yourself with negative evaluations," Toma says. "But if you have low self-esteem, the opposite is true."

Toma opted to use the Implicit Association Test because it cannot be faked, unlike more traditional self-reporting tools.

"Our culture places great value on having high self-esteem. For this reason, people typically inflate their level of self-esteem in self-report questionnaires," she says. "The Implicit Association Test removes this bias."

Additionally, Toma investigated whether exposure to one's own Facebook profile affects behavior.

"We wanted to know if there are any additional psychological effects that stem from viewing your own self-enhancing profile," says Toma, whose work will be published in the June issue ofMedia Psychology. "Does engaging with your own Facebook profile affect behavior?"

The behavior examined in the study was performance in a serial subtraction task, assessing how quickly and accurately participants could count down from a large number by intervals of seven. Toma found that self-esteem boost that came from looking at their profiles ultimately diminished participants' performance in the follow-up task by decreasing their motivation to perform well.

After people spent time on their own profile they attempted fewer answers during the allotted time than people in a control group, but their error rate was not any worse. Toma says the results are consistent with self-affirmation theory, which claims that people constantly try to manage their feelings of self-worth.

"Performing well in a task can boost feelings of self-worth," Toma says. "However, if you already feel good about yourself because you looked at your Facebook profile, there is no psychological need to increase your self-worth by doing well in a laboratory task."

But Toma cautions against drawing broad conclusions about Facebook's impact on motivation and performance based on this particular study, as it examines just one facet of Facebook use.

"This study shows that exposure to your own Facebook profile reduces motivation to perform well in a simple, hypothetical task," she says. "It does not show that Facebook use negatively affects college students' grades, for example. Future work is necessary to investigate the psychological effects of other Facebook activities, such as examining others' profiles or reading the newsfeed."

Elevated Carbon Dioxide Making Arid Regions Greener

May 31, 2013 — Scientists have long suspected that a flourishing of green foliage around the globe, observed since the early 1980s in satellite data, springs at least in part from the increasing concentration of carbon dioxide in Earth's atmosphere. Now, a study of arid regions around the globe finds that a carbon dioxide "fertilization effect" has, indeed, caused a gradual greening from 1982 to 2010.

Focusing on the southwestern corner of North America, Australia's outback, the Middle East, and some parts of Africa, Randall Donohue of the Commonwealth Scientific and Industrial Research Organization (CSIRO) in Canberra, Australia and his colleagues developed and applied a mathematical model to predict the extent of the carbon-dioxide (CO₂) fertilization effect. They then tested this prediction by studying satellite imagery and teasing out the influence of carbon dioxide on greening from other factors such as precipitation, air temperature, the amount of light, and land-use changes.

The team's model predicted that foliage would increase by some 5 to 10 percent given the 14 percent increase in atmospheric CO₂ concentration during the study period. The satellite data agreed, showing an 11 percent increase in foliage after adjusting the data for precipitation, yielding "strong support for our hypothesis," the team reports.

"Lots of papers have shown an average increase in vegetation across the globe, and there is a lot of speculation about what's causing that," said Donohue of CSIRO's Land and Water research division, who is lead author of the new study. "Up until this point, they've linked the greening to fairly obvious climatic variables, such as a rise in temperature where it is normally cold or a rise in rainfall where it is normally dry. Lots of those papers speculated about the CO₂ effect, but it has been very difficult to prove."

He and his colleagues present their findings in an article that has been accepted for publication in Geophysical Research Letters, a journal of the American Geophysical Union.

The team looked for signs of CO₂ fertilization in arid areas, Donohue said, because "satellites are very good at detecting changes in total leaf cover, and it is in warm, dry environments that the CO₂ effect is expected to most influence leaf cover." Leaf cover is the clue, he added, because "a leaf can extract more carbon from the air during photosynthesis, or lose less water to the air during photosynthesis, or both, due to elevated CO₂." That is the CO₂ fertilization effect.

But leaf cover in warm, wet places like tropical rainforests is already about as extensive as it can get and is unlikely to increase with higher CO₂ concentrations. In warm, dry places, on the other hand, leaf cover is less complete, so plants there will make more leaves if they have enough water to do so. "If elevated CO₂ causes the water use of individual leaves to drop, plants will respond by increasing their total numbers of leaves, and this should be measurable from satellite," Donohue explained.

To tease out the actual CO₂ fertilization effect from other environmental factors in these regions, the researchers first averaged the greenness of each location across 3-year periods to account for changes in soil wetness and then grouped that greenness data from the different locations according to their amounts of precipitation. The team then identified the maximum amount of foliage each group could attain for a given precipitation, and tracked variations in maximum foliage over the course of 20 years. This allowed the scientists to remove the influence of precipitation and other climatic variations and recognize the long-term greening trend.

In addition to greening dry regions, the CO₂ fertilization effect could switch the types of vegetation that dominate in those regions. "Trees are re-invading grass lands, and this could quite possibly be related to the CO₂ effect," Donohue said. "Long lived woody plants are deep rooted and are likely to benefit more than grasses from an increase in CO₂."

"The effect of higher carbon dioxide levels on plant function is an important process that needs greater consideration," said Donohue. "Even if nothing else in the climate changes as global CO₂ levels rise, we will still see significant environmental changes because of the CO₂ fertilization effect."

This study was funded by CSIRO's Sustainable Agriculture Flagship, Water for a Healthy Country Flagship, the Australian Research Council and Land & Water Australia.