Scientific Highlights from PSI's research divisions


Condensed Matter Research with Neutrons and Muons (NUM)

4 March 2016

Stratified Micellar Multilayers - Toward Nanostructured Photoreactors

Polyelectrolyte multilayers (PEMs) with stratification of the internal structure were assembled from statistical amphiphilic copolyelectrolytes of opposite charges. These polyelectrolytes organize in aqueous solutions into micellar structures with fluoroalkyl and aromatic nanodomains, respectively, that were also preserved after deposition as thin films via layer-by-layer (LbL) electrostatic self-assembly. The unimolecular micelles, formed due to statistical compositions of amphiphilic polyelectrolytes used, were shown to suppress chain interdiffusion between adjacent layers in resulting micellar PEMs, as evidenced by spectroscopic ellipsometry, atomic force microscopy (AFM), and neutron reflectometry (NR) measurements. Additionally, hydrophobic cores of the micelles were used as hosts for photoactive molecules, namely, ferrocene and perfluorinated magnesium phthalocyanine. Stratified micellar multilayers were then deposited as hollow capsules using CaCO3 microparticles as templates. Photoinduced electron transfer (PET) between ferrocene and phthalocyanine solubilized in the polymer micelles was demonstrated to occur efficiently inside the stratified, polyelectrolyte walls of the capsules, due to the polarity gradient created by the incompatible aromatic and fluoroalkyl domains. The obtained results present a new approach to construct well-organized, self-assembled nanostructured materials for solar energy conversion.
Facility: SINQ

Reference: M. Kopec et al, Chemistry of Materials 28, 2219 (2016)

Read full article: here

Synchrotron Radiation and Nanotechnology (SYN)

11 April 2016

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Researchers find key to zinc rich plants to combat malnutrition

The diet in many developing countries is lacking zinc, but researchers have just solved the riddle of how to get more zinc into crop seeds. The discovery has been published in Nature Plants, and the research was led by University of Copenhagen.

By Johanne Uhrenholt Kusnitzoff

30 March 2016

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Watching lithium move in battery materials

In order to understand limitations in current battery materials and systematically engineer better ones, it is helpful to be able to directly visualize the lithium dynamics in materials during battery charge and discharge. Researchers at ETH Zurich and Paul Scherrer Institute have demonstrated a way to do this.

7 March 2016

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High-performance thermoelectric nanocomposites from nanocrystal building blocks

Using an assembly of colloidal nanocrystals a Ag-PbS nanocomposite was produced with increased thermoelectic figures of merit up to 1.7K at 850 K. EXAFS spectroscopy at the Ag K-edge was essential to show that Ag does not dissolve in PbS nanoparticles but preserved the individual nanodomains. This reduces the PbS intergrain energy barriers for charge transport
General Energy (ENE)

SwissFEL

First lasing in SwissFEL test facility

On the 15th of January 2014, first lasing was achieved in the SwissFEL injector test facility. This is a great success on the way towards SwissFEL, the future hard x-ray free-electron laser that is currently under construction at PSI. It proves the successful functioning of many key components together in a larger system as required for SwissFEL. Furthermore, this is the very first operation of a free-electron laser in Switzerland. Since 2010, PSI has been operating a test facility to study and optimize the electron source for SwissFEL. Over the last years, the test facility was advanced to one of the most brilliant electron sources in the world, and during the last shutdown end of 2013, a first undulator - a highly precise periodic array of magnets - was installed in the facility. This innovative type of undulator is an in-vacuum design with a very small period length of only 15 mm, that was specifically developed for SwissFEL. During the very first beam time after the installation of the undulator, the electron beam could be successfully tuned to pass the undulator with low losses - this is very important to prevent radiation damage to the sensitive 1060 permanent magnets of the undulator. The electrons generate spontaneous radiation when passing the undulator, and this radiation was detected with scintillator screen monitors. In a next step, the electron beam was strongly compressed in a bunch compressor chicane to generate a very large charge density, which is required for the FEL process. This initiated the free-electron lasing process, leading to an exponential increase of the emitted radiation along the undulator. An electron beam with an energy of 220 MeV and a bunch charge of 200 pC was used in that process, and first lasing was detected at a wavelength of around 80 nm. By adjusting the gap of the undulator, the wavelength of the emitted laser light could be tuned over one octave from around 45 to 90 nm
Facility: SwissFEL
Reference: Hans Braun; hans.braun@psi.ch; Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland