Microsecond-resolved views by SAXS and WAXS on the very early stages of quantum dot formation

Wednesday, April 26, 2017 - 3:00pm

SLAC, Kavli 3rd Floor Conference Room

Speaker:  Andreas Magerl, University Erlangen-Nürnberg (UEN)

Program Description

To access the very early stages of nucleation and growth of particles in liquid media, we have developed a free liquid jet setup, where the reactants are pushed by high power syringe pumps through a Y-shaped micromixer and immediately ejected as a free jet. This provides access to reaction times as short as 10 μs. In the seminar results from SAXS and simultaneous WAXS data of non-stabilized and ligand-decorated CdS in aqueous solution as a prototype example for quantum dot formation will be discussed.

The SAXS data taken between 10 and 2500 μs show, that the CdS quantum dot formation in aqueous solutions follows a two-step pathway starting with a rapid formation of primary clusters driven by the fast diffusion of cadmium and sulfur ions. Further growth is by cluster attachment where the diffusion of the primary clusters appears as the limiting factor. From the WAXS data it becomes evident, that the particles at this early stage are not yet crystalline. This is also supported by ab initio theoretical calculations.

 

Curriculum vitae

1968 - 1974 Study of physics at the Technical University of Munich, Germany
                    Diploma degree in physics (equivalent to M. Sc.)
1974 - 1979 Doctorate in physics at the Technical University of Munich on the subject „Phonons
                    in metal-hydrogen systems“
03.1979 - 09.1980 Guest researcher at the National Institute of Standards and Technology (NIST),
                              Maryland, USA with a scholarship from the German Science Foundation (DFG) for
                              9 months followed by an employment by NBS
10. 1980 - 01.1981 Visiting research associate professorship at the Department of Physics and Astronomy,
                               University of Maryland, Maryland, USA
02. 1981 Employment as a physicist at the Institute Max von Laue – Paul Langevin (ILL),
              Grenoble, France
1984 Staff scientist at the ILL
1988 Group leader at the ILL
07. 1993 Habilitation in experimental physics at the Ruhr University of Bochum, Germany,
               on the subject „High-resolution inelastic neutron spectroscopy – new methods
               and applications”.
06 1994 Guest professorship at the Ruhr University, Bochum
Since 10. 1997 Professorship for crystallography and structural physics (chair) at the University
                         Erlangen-Nürnberg
10. 2006 09. 2009 Head of the physics department at the University Erlangen-Nürnberg
Since April 2015 Retired with part-time employment at the University Erlangen-Nürnberg

 

 

Microsecond-resolved views by SAXS and WAXS on the very early stages of quantum dot formation
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