That's particularly true where the global warming potential of the chemicals is concerned, says a new study by NASA and Purdue University researchers.
The study offers at least a partial recipe that industrial chemists could use in developing alternatives with less global warming potential than materials commonly used today. The study was published in the Proceedings of the National Academy of Sciences.
"What we're hoping is that these additional requirements for minimizing global warming will be used by industry as design constraints for making materials that have, perhaps, the most green chemistry," says Joseph Francisco, a Purdue chemistry and earth and atmospheric sciences professor.
The classes of chemicals examined in the study are widely used in air conditioning and the manufacturing of electronics, appliances and carpets. Other uses range from applications as a blood substitute to tracking leaks in natural gas lines.
The chemicals include fluorine atom-containing compounds such as hydro fluorocarbons, per fluorocarbons, hydrofluoroethers, hydrofluoroolefins, and sulfur and nitrogen fluorides.
In a 2009 study, Francisco and NASA collaborators Timothy Lee and Partha Bera examined the molecular qualities that make fluorinated compounds even more powerful warming promoters than chemicals emitted in greater quantities, such as carbon dioxide and methane.
The fluorinated compounds proved to be far more efficient at blocking radiation -- or heat -- in the atmospheric window. The atmospheric window is the frequency range in the infrared region of the electromagnetic spectrum through which radiation from Earth is released into space. This helps cool the planet. When that radiation is trapped instead of being released, a greenhouse effect results, warming the planet.
The new study looked at a broader class of chemicals to identify molecular-level features that make them more or less efficient at trapping radiation in the atmospheric window. The study employed results from atomic-scale quantum chemistry calculations done on computers from NASA and Information Technology at Purdue (ITaP), Purdue's central information technology organization.
"We specifically looked at molecules that we felt would have potential for industrial use as replacements for chlorofluorocarbons," says Francisco, whose research focuses on the chemistry of molecules in the atmosphere.
Among other things, the study looked at how the number and placement of electronegative atoms in a molecule's structure affects its radiative efficiency. The number and placement of fluorine atoms proved to be a key factor because they're very electronegative and form highly polar bonds with carbon and sulfur.
Fluorine atoms thus tend to change the bond-polarity of the molecules -- modifying the bonds holding the atoms in the structure. This, in turn, affects how a molecule will absorb infrared radiation that normally passes through Earth's atmosphere and into space.
“The polarity change is what makes for an efficient absorber of infrared radiation,” says Lee, chief of the Space Science and Astrobiology Division at NASA Ames Research Center.One message from the study: Avoid allowing fluorines to bunch up in a molecular structure. “In other words, don't put them all on one atom,” Francisco says. “Spread them out.”
The fluorinated compounds also persist longer in the atmosphere than carbon dioxide and other major global warming agents, Lee and Francisco note. Even if emitted in lower quantities, fluorine-containing chemicals might have a powerful cumulative effect. Some don't break down for thousands of years.
Writer: Greg Kline, science and technology writer, Information Technology at Purdue (ITaP), 765-494-8167, firstname.lastname@example.orgSources:
Greg Kline | EurekAlert!
The personality factor: How to foster the sharing of research data
06.09.2017 | ZBW – Leibniz-Informationszentrum Wirtschaft
Europe’s Demographic Future. Where the Regions Are Heading after a Decade of Crises
10.08.2017 | Berlin-Institut für Bevölkerung und Entwicklung
At the productronica trade fair in Munich this November, the Fraunhofer Institute for Laser Technology ILT will be presenting Laser-Based Tape-Automated Bonding, LaserTAB for short. The experts from Aachen will be demonstrating how new battery cells and power electronics can be micro-welded more efficiently and precisely than ever before thanks to new optics and robot support.
Fraunhofer ILT from Aachen relies on a clever combination of robotics and a laser scanner with new optics as well as process monitoring, which it has developed...
Plants and algae use the enzyme Rubisco to fix carbon dioxide, removing it from the atmosphere and converting it into biomass. Algae have figured out a way to increase the efficiency of carbon fixation. They gather most of their Rubisco into a ball-shaped microcompartment called the pyrenoid, which they flood with a high local concentration of carbon dioxide. A team of scientists at Princeton University, the Carnegie Institution for Science, Stanford University and the Max Plank Institute of Biochemistry have unravelled the mysteries of how the pyrenoid is assembled. These insights can help to engineer crops that remove more carbon dioxide from the atmosphere while producing more food.
A warming planet
Our brains house extremely complex neuronal circuits, whose detailed structures are still largely unknown. This is especially true for the so-called cerebral cortex of mammals, where among other things vision, thoughts or spatial orientation are being computed. Here the rules by which nerve cells are connected to each other are only partly understood. A team of scientists around Moritz Helmstaedter at the Frankfiurt Max Planck Institute for Brain Research and Helene Schmidt (Humboldt University in Berlin) have now discovered a surprisingly precise nerve cell connectivity pattern in the part of the cerebral cortex that is responsible for orienting the individual animal or human in space.
The researchers report online in Nature (Schmidt et al., 2017. Axonal synapse sorting in medial entorhinal cortex, DOI: 10.1038/nature24005) that synapses in...
Whispering gallery mode (WGM) resonators are used to make tiny micro-lasers, sensors, switches, routers and other devices. These tiny structures rely on a...
Using ultrafast flashes of laser and x-ray radiation, scientists at the Max Planck Institute of Quantum Optics (Garching, Germany) took snapshots of the briefest electron motion inside a solid material to date. The electron motion lasted only 750 billionths of the billionth of a second before it fainted, setting a new record of human capability to capture ultrafast processes inside solids!
When x-rays shine onto solid materials or large molecules, an electron is pushed away from its original place near the nucleus of the atom, leaving a hole...
19.09.2017 | Event News
12.09.2017 | Event News
06.09.2017 | Event News
25.09.2017 | Power and Electrical Engineering
25.09.2017 | Health and Medicine
25.09.2017 | Physics and Astronomy