For the first time, a team of scientists has succeeded in capturing in real time the first few milliseconds in the life of a gold coating as it forms on a polymer. The team used DESY’s high-brilliance X-ray source PETRA III to observe the earliest stages in the growth of a metal-polymer hyb ... more
Scientists measure soot particles in flight
For the first time, air-polluting soot particles have been imaged in flight down to nanometre resolution. Pioneering a new technique, the international team, including researchers from DESY, snapped the most detailed images yet of airborne aerosols. “For the first time we can actually see the structure of individual aerosol particles floating in air, their 'native habitat',” said DESY scientist Henry Chapman from the Center for Free-Electron Laser Science (CFEL) in Hamburg. “This will have important implications for various fields from climate modelling to human health.” CFEL is a joint venture of Deutsches Elektronen-Synchrotron DESY, the German Max Planck Society and the University of Hamburg.
Aerosol particles like soot play important roles in a wide range of fields from toxicology to climate science. Despite their importance, their properties are surprisingly difficult to measure: Visible light doesn't provide the necessary resolution, X-ray sources are usually not bright enough to image single particles, and for electron microscopy particles have to be collected onto a substrate, which potentially alters their structure and encourages agglomeration.
Using the world´s most powerful X-ray laser LCLS at the U.S. SLAC National Accelerator Laboratory in Stanford (California), the team captured images of single soot particles floating through the laser beam. “We now have a richer imaging tool to explore the connections between their toxicity and internal structure,” said SLAC's Duane Loh, lead author of the study appearing in this week´s scientific journal “Nature”. Free-electron lasers like LCLS or the European XFEL currently being built in Hamburg consist of particle accelerators that send unbound (free) electrons on a tight slalom course where they emit X-ray light.
The study focused on particles less than 2.5 micrometres in diameter. This is the size range of particles that efficiently transport into the human lungs and constitute the second most important contribution to global warming. Microscopic soot particles were generated with electric sparks from a graphite block and fed with a carrier gas of argon and nitrogen into a device called an aerodynamic lens, that produces a thin beam of air with entrained soot particles. This aerosol beam intercepted the pulsed laser beam. Whenever an X-ray laser pulse hit a soot particle, it produced a characteristic diffraction pattern that was recorded by a detector. From this pattern, the scientists were able to reconstruct the soot particle´s structure.
“The structure of soot determines how it scatters light, which is an important part of understanding how the energy of the sun is absorbed by the earth's atmosphere. This is a key factor in models of the earth's climate,” explained co-author Andrew Martin from DESY. “There also are many links between airborne particles around two micrometres in size and adverse health effects. Using the free-electron laser we are now able to measure the shape and composition of individual airborne particles. This may lead to a better understanding of how these particles interfere with the function of cells in the lungs.”
The team recorded patterns from 174 individual soot particles and measured their compactness, using a property called fractal dimension. “We've seen that the fractal dimension is higher than what was thought,” said Chapman. “This means that soot in the air is compact, which has implications for the modelling of climate effects.” Also, the structure of the airborne soot seems to be surprisingly variable. “There is quite some variation in the fractal dimension, which implies that a lot of rearrangement is going on in the air,” explains Chapman.
A primary long-term goal of the research is to take snapshots of airborne particles as they change their size, shape and chemical make-up in response to their environment, explained Michael Bogan from SLAC, who led the research. “Scientists can now imagine being able to watch the evolution of soot formation in combustion engines from their molecular building blocks, or maybe even view the first steps of ice crystal formation in clouds.”
In real-world settings soot is seldom pure. To see the effects of mixing with other aerosols, the researchers added salt spray to the soot particles, resulting in larger particles with soot attached to the tiny salt crystals. Such composite particles might form in coastal cities and are expected to have a much larger climate effect than soot alone. Composite aerosols are more difficult to analyse, but the new technique could clearly discern between soot, salt and mixtures of both. As the aerosol particles are vaporized by the intense X-ray laser pulse, the researchers could use mass spectroscopy to examine the composition of each individual particle imaged.
Even though the aerosol particles are destroyed by the X-ray laser pulse, the pulse is so short that it out-runs this destruction. Therefore the diffraction patterns are of high quality and represent the undamaged object. The novel X-ray technique can find wide application to study all sorts of aerosols and can also be extended to resolve the static and dynamic morphology of general ensembles of disordered particles, the researchers state.
“We are now able to study the structure of soot by measuring individual particles in a large ensemble,” explains Martin. “Biological samples, like cells and large proteins, have a similar size to the soot particles we studied and also lack a fixed, reproducible structure. In the future it may be possible to extend these techniques beyond aerosols, to study the structural variations in biological systems.”
The research team included contributors from SLAC, DESY, Lawrence Berkeley National Laboratory, the Max Planck Institutes, the National Energy Research Scientific Computing Center, Lawrence Livermore National Laboratory, Cornell University, the University of Hamburg, Synchrotron Trieste and Uppsala University. LCLS is supported by DOE’s Office of Science.
- X-ray lasers
An interdisciplinary team of scientists has used ultrashort X-ray pulses to image extremely rapidly exploding jets of water. The experiments, carried out at the European X-ray laser facility European XFEL, aim to study ultrafast events that occur in a very small region by means of X-ray hol ... more
A novel kind of microscope is able to detect tiny protein crystals, which are beyond the imaging power of even modern light microscopes. The innovative technique relies on various non-linear optical effects to image even nanocrystals, which are increasingly being used for protein structure ... more
Hard X-ray free-electron lasers (XFELs) have delivered intense, ultrashort X-ray pulses for over a decade. One of the most promising applications of XFELs is in biology, where researchers can capture images down to the atomic scale even before the radiation damage destroys the sample. In ph ... more
An international team of scientists, led by Kartik Ayyer from the MPSD, has obtained some of the sharpest possible 3D images of gold nanoparticles. The resuts lay the foundation for obtaining high resolution images of macromolecules. The study was carried out at the European XFEL’s Single P ... more
The water on Earth makes our planet inhabitable. It absorbs the Sun’s energy and releases it in the form of heat. An international research collaboration headed by the Max Planck Institute for Polymer Research (MPI-P) has now shown how and how fast the stored energy in the water molecules i ... more
Many of the molecular building blocks of life have two versions that are mirror images of one another, known as enantiomers. Although seemingly identical, the two enantiomers can have completely different chemical behaviour – a fact that has major implications in our day-to-day lives. For e ... more
Researchers from the Department of Atomically Resolved Dynamics of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) at the Center for Free-Electron Laser Science in Hamburg, the University of Hamburg and the European Molecular Biology Laboratory (EMBL) outstation in ... more
What happens when a chemical bond is broken? That question was recently answered with the help of a so-called free electron x-ray laser, which makes it possible to follow in real time how bindings in a molecule are changed and broken. The study, published in Science, found, among other thin ... more
- 1Detect neurodegenerative diseases such as Alzheimer's by a simple eye scan?
- 2Fluorescence microscopy at highest spatial and temporal resolution
- 3The Mechanics of the Immune System
- 4Resolve Biosciences Launches New Era in Single-Cell Spatial Analysis
- 5Quick look under the skin
- 6New ion trap to create the world's most accurate mass spectrometer
- 7How does your computer smell?
- 8Clocking electron movements inside an atom
- 9Sartorius closes 2020 with strong growth
- 10A clear path to better insights into biomolecules