discovered_01_2016

WWW.HZDR.DE discovered 01.16 TITLE Lasers plus acoustics Not all radionuclides are suitable for fluorescence spectroscopy. Neptunium and plutonium species, for example, do not respond to excitation by producing an emission. For these samples HZDR researchers chose a different procedure: laser-induced photoacoustic spectroscopy. Here, too, a laser pulse is directed at a sample, but the system responds differently. "At the point where the laser pulse impacts, the temperature of the sample increases. It is a tiny effect but we are able to measure this local warming," Geipel explains, "because it creates a pressure wave which we can convert into an electric signal using a piezoceramic sensor." The sample is irradiated with laser pulses of differing wavelengths. If it responds to a certain wavelength, the researchers get a meaningful absorption spectrum. The measuring process is highly sensitive: recently, HZDR analyzed leachate from mining residues in which the scientists identified nuclides at a concentration of less than 2 ppm. In addition to his lab work, Gerhard Geipel currently has other tasks on his plate as well: he was organizing the international BioMetals Symposium that took place in Dresden in July. This expert conference, which is held every two years, brings together specialists in the interaction of metals in biology. The fact that Dresden has been chosen as the venue for the symposium for the first time, underscores the expertise of the HZDR researchers. PUBLICATIONS: G. Geipel: "Some aspects of actinide speciation by laser- induced spectroscopy", in Coordination Chemistry 2006 (DOI: 10.1016/j.ccr.2005.11.007) G. Geipel, K. Viehweger: "Speciation of uranium in compartments of living cells", in Biometals 2015 (DOI: 10.1007/s10534-015-9836-x) Y. Wang, M. Frutschi, E. Suvorova, V. Phrommavanh, M. Descostes, A. A.A. Osman, G. Geipel, R. Bernier-Latmani: "Mobile uranium(IV)-bearing colloids in a mining-impacted wetland", in Nature Communications 2013 (DOI: 10.1038/ ncomms3942) CONTACT _Institute of Resource Ecology at HZDR Dr. Gerhard Geipel g.geipel@hzdr.de FLUID: The wavelength and the duration of the transmitted light not only reveal which radionuclide is involved but also which species. Photo: Oliver Killig

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