14.1.2019 MatSEC meeting in Chorin
Once a year the PhD students in the graduate school MatSEC and their supervisors meet for a two-day retreat near Berlin. The students have to present their projects to the others and the supervisors give more or less helpful suggestions and recommendations. This year we all met in lovely Chorin – roughly 60 kilometers Northeast of Berlin. This municipality is famous for its more than 700 years old abbey. Although the schedule was very tight, we used some time of our lunch break to have a short visit of this monastery.
20.12.2018 Our article about the nature of water interactions with anatase titanium dioxide nanoparticles has been published in the Journal of Materials Chemistry A
Together with our collaborators from FHI, we investigated by soft X-ray PES, which molecular species exist at the titanium dioxide nanoparticle / aqueous solution interface as a function of solution pH. This solved a long-standing question whether water adsorbs dissociatively, molecularly, or mixed at the TiO2 interface. Our resonant photoemission results indicate that water adsorbs molecularly at low pH, and dissociatively at the TiO2 nanoparticle surface at basic pH. Water and OH- adsorb at the titanium sites, and no oxygen defects exist. For more details click here
29.11.2018 Solvated electrons in liquid ammonia measured
After a successful beamtime in May this year, where we recorded first-ever photoelectron spectra of liquid ammonia we went this beamtime one step further: together with our collaborators from Prague, FHI, and Los Angeles we dissolved lithium and sodium metal in liquid ammonia and studied the solvated electrons generated during this process. Unlike in water solvated electrons in liquid ammonia are stable for hours and the concentrations can be in the molar regime. Pavel, Phil, and Tillmann from Prague set up their customized liquid-ammonia preparation kit and liquid-jet system onto our SOL³ experimental station. After some troublesome first attempts, during the second night shift, we finally recorded it – the ground state energy of the solvated electron! Well done everyone!
27.11.2018 Our paper on organosulfur surfactants at the aqueous solution – vapor interface has been published in The Journal of Physical Chemistry C
Together with our collaborators from UC Irvine, California, and our ex-pat Stephan Thürmer in Japan we published a paper about the spatial arrangement of dimethyl sulfoxide, dimethyl sulfone, and dimethyl sulfite in water. It is part of the Hans-Joachim Freund and Joachim Sauer Festschrift in The Journal of Physical Chemistry C. Here, we present for the first time photoelectron angular distribution (PAD) measurements of solutes in water (so far we only published solvent PAD data) – these data are invaluable to understand how the DMSOx molecules coexist near the water surface in mixed equimolar aqueous solutions. The exceptionally large surface propensity of dimethyl sulfite is recognized by a narrow, gasphase-like photoelectron spectrum, revealing that dimethyl sulfite experiences very few hydration interactions. Experimentally observed trends in surface activity for the different molecules, which are complemented by molecular dynamics simulations, agree with findings obtained with other surface-sensitive techniques. For more details click here
1.11.2018 Our paper about how much ions do affect the electronic structure of liquid water has been published in Chemical Science
It is amazing – we are studying liquid water by more than 10 years now and still cannot answer so many of its mysteries. However, one question that bothered the community has been finally answered: What is the effect of solutes to the electronic-structure of liquid water? In other words: Do water’s electrons care about electrolytes? Together with our theory-collaborators from Prague (Eva, Štĕpán, and Petr), and the experimental groups from FHI (Heba, Marvin, and Bernd) and HZB (Iain) we investigated carefully how the binding energies of the liquid water peaks shift when increasing the concentration of sodium iodide from 0 to 8 molar. Surprisingly, the photoelectron spectrum is only mildly affected, with the largest (negative) shifts of ~370 meV for the 1b2 orbital and a narrowing of the flat-top shape orbital 3a1 of up to 450 meV. Most importantly, our calculations as well as our experiments show that due to electronic screening the 1b1 binding energy is only minimal shifted (by less than 60 meV) even at highest electrolyte concentrations, which makes this water peak a robust energetic reference for aqueous liquid microjet photoemission studies. For more details click here
16.10.2018 Lifting up our electron analyzer to replace a metal adapter
To solve some issues with our magnetic field compensation we replaced a 13.5 cm long adapter flange between the drift stage of our analyzer and the main chamber by a component of same length made of µ-metal. To get access, we had to lift up the analyzer with the BESSY crane and to remove parts of the Helmholtz-coils. The whole procedure went well and also thanks to updated lens tables, first measurements show an improvement in electron transmission, especially for lower kinetic energies.
1.9.2018 New Manipulators
Two new manipulators arrived and are ready to be used in the upcoming beamtimes for our users. The small one (a CF-40 with 5 cm translation) will replace our old liquid-jet manipulator, which served well the last eight (!) years. The big one comes with automated micrometer-adjustable xyz translation (up to 40 cm) and full rotation. It is meant for large sample(holders), transmission-cells, including (photo-)electrochemical cells with electron-transparent membranes and other bulky objects with up to 9.8 cm diameter that need to be investigated by photoelectron spectroscopy.
1.6.2018 Welcome Garlef Wartner!
PhD candidate Garlef Wartner from Stade, Lower Saxony, joined our team. A very warm welcome!
2.5.2018 First liquid ammonia spectra taken with our SOL³ setup
After many attempts at FHI and at BESSY we finally got a stable liquid ammonia jet running in our SOL³ setup under vacuum conditions. Phil and Tillmann managed to enhance the duration of the running jet to almost 8 hours – enough time to measure the valence band, core levels, angular photoelectron dependencies, salts dissolved in liquid ammonia at good statistics, and ultimatively, high-concentrated solvated electrons from dissolved Lithium metal in liquid ammonia. Please watch this video on Youtube and share the moment where we collected our first liquid ammonia photoelectron spectrum.
1.5.2018 Welcome Dennis Hein!
PhD candidate Dennis Hein from Aalen, Baden-Württemberg, joined our team. A very warm welcome!
30.4.2018 Our article about the water dissociation at the surface of hematite nanoparticles has been published in Chemical Science
Together with our colleagues from FHI we investigated the hematite nanoparticle – water interface by (resonant) liquidjet photoelectron spectroscopy. This method is sufficiently sensitive for the detection of adsorbed hydroxyl species, resulting from the water dissociation at the nanoparticle surface in aqueous solution. For more information click here
26.4.2018 First photoelectron spectra from a flat-jet
Bernd Winter and his team from FHI tested for the first time their new flat-jet assembly in our SOL³ setup under vacuum conditions. When two (identical) liquid-jets hit under a certain angle with the same flow a flat leaf-shaped liquid surface will form, which thickness can be adjusted to less than a micrometer. Bernds team also managed to get the first photoelectron spectra of liquid water from a flat-jet. Well done!
17.3.2018 Rotating the machine to magic angle
Over the weekend we needed to rotate our electron analyzer to 54.7° relative to the polarization axis of the synchrotron light at the U49/2-PGM-1 beamline of BESSY. At this so-called magic angle we can determine relative intensities from different solute species in aqueous solution from a liquid jet, which are then only depending on probing depth and ionization cross section, ignoring complex photoelectron angular distribution functions. We used this geometry of our electron analyzer to determine the depth-depending dissociation constant of HSO4-/SO42- in water as a function of concentration and kinetic energy. Rotating the machine only takes 10 minutes using a pulley assembly. All seven turbomolecular pumps of the HIPP-2 R4000 electron analyzer are off during the rotation, but the roughing pumps are still running, allowing for a fast run-up of the experiments compared to a complete venting.
14.3.2018 Dr. Stephan Thürmer from The University of Kyoto visited us
During his Europe-tour, Stephan Thürmer, very welcomed long-term expat and designer of the previous liquidjet experimental setup, the LiquidjetPES at BESSY, joined us for one day in our commissioning beamtime. As in the good-old times, Stephan got immediately familiar with our new SOL³ system and gave valuable input to improve the lens tables of our hemispherical electron analyzer, pushing the electron transmission to new highs.
13.12.2017 Dr. Alex Gaiduk from The University of Chicago visited us
Our theory collaborator from Giulia Gallis group at ‘UChi’, Alex Gaiduk, visited our group and took a look at our experimental setups at BESSY. He was impressed by the machines that confirm (and on rare occasions ‘readjust’) his invaluable calculated energies and redox potentials from aqueous salt solutions. He also presented his newest ab-initio calculations on one of the hot topics in the water-community: the precise energy position of liquid water’s conduction band - an important number that is experimentally very hard to derive. For more details on Alex work check out his newest article and the Galli group webpage.
13.11.2017 Our article about the iron-(III)-oxo oligomer formation in aqueous solution is online
Together with the research groups of Franziska Emmerling at the BAM Federal Institute for Materials Research and Testing, Berlin, Ralph Krähnert at the Technical University Berlin, and Bernd Winter at Fritz-Haber-Institut der Max-Planck-Gesellschaft, we looked into the formation process of small iron-oxo oligomers in aqueous solution. This chemical process is crucial for the formation of nanoparticles in aqueous phase. By a combination of Raman spectroscopy, Small Angle X-ray scattering and Liquid-microjet resonant photoelectron spectroscopy we could identify and measure the electronic structure properties of the iron-oxo oligomeric seeds that were produced by adding sodium hydroxide to our iron chloride solution. Our findings have been published in Physical Chemistry Chemical Physics. For more details click here.
28.9.2017 First gas dynamic virtual nozzle measurements with our setup
Together with our collaborators from FHI Berlin and IOM Leipzig we successfully measured for the first time at our setup a liquid jet, surrounded by a strong gas-stream to investigate gas-liquid interactions. Claudia, Bernd, and Sebastian from FHI were interested in the CO2 uptake of monoethanolamine in aqueous solutions and looked for its reaction products with respect to the gas-solution interface, and as a function of pH. An exciting experiment!
31.7.2017 Our new SOL³PES setup goes into user operation
Just in time for the start of the user operation of our new SOL³PES setup we got a technical article accepted in Review of Scientific Instruments, describing in detail its capabilities and features. Click here.
19.7.2017 Emmy-Noether meeting in Potsdam
Robert joined the annual three-day meeting as Emmy-Noether-‘freshman’, which took place for the 16th times. This year the current Emmy-Noether stipend holders and alumni met at the lovely Templiner See in Potsdam to talk about funding opportunities, career options after the Emmy-Noether stipend and the changes to the general social conditions in science and politics. For more details check out this DFG site (in German only).
10.4.2017 Beamtime at the U49/2-PGM-1 beamline at BESSY II
This beamtime we further explored metal oxide nanoparticles in water by liquidjet photoelectron spectroscopy. Arno prepared an Fe3O4 nanoparticle solution in our glove box – it is not an easy experiment. Jet stability and concentration are at their limits (and beyond…).
20.3.2017 Beamtime at UE52-SGM-1 beamline at BESSY II
We measured for the first time with our new SOL³PES setup angle-resolved valence photoelectron spectra of neat water. These measurements are key to derive the so-called anisotropy parameter of the outer water valence orbitals. By comparison with gas phase water anisotropy parameter values we can directly determine elastic and inelastic scattering behavior of the outgoing photoelectrons and indirectly the electron mean free path in water – a very important measure for the probing depth. To get our machine to the UE52-SGM-1 beamline we had to use the BESSY crane.
This beamtime was part of the 1st international photonschool at HZB, where 20 international postdocs, master and Phd students got hands-on experience on several experimental BESSY stations, including our SOL³ setup. See more
9.3.2017 Sensitive Method for Detecting Ion Pairs in Aqueous Solutions
Our work on Electron-Transfer Mediated Decay in aqueous solutions was published in Nature Chemistry. See more
1.3.2017 Welcome Arno Bergmann!
Dr. Arno Bergmann, from TU Berlin, joins the team as a postdoctoral research fellow. A very warm welcome!