Publications in 2021
Clathrate Adhesion Induced by Quasi-Liquid Layer,Ngoc N. Nguyen✉, Rüdiger Berger✉, Michael Kappl, Hans-Jürgen Butt,
Journal of Physical Chemistry C (2021). https://doi.org/10.1021/acs.jpcc.1c06997
The adhesive force of clathrates to surfaces is a century-old problem of pipeline blockage
for the energy industry. Here, we provide new physical insight into the origin of this force
by accounting for the existence of a quasi-liquid layer (QLL) on clathrate surfaces. To gain
this insight, we measure the adhesive force between a tetrahydrofuran clathrate and a solid
sphere. We detect a strong adhesion, which originates from a capillary bridge that is formed
from a nanometer-thick QLL on the clathrate surface. The curvature of this capillary bridge is
nanoscaled, causes a large negative Laplace pressure, and leads to a strong capillary attraction.
"Liquid-like" Water in Clathrates Induced by Host-Guest Hydrogen,Ngoc N. Nguyen✉, Rüdiger Berger✉, Manfred Wagner, Jürgen Thiel, Hans-Jürgen Butt, Rober Graf✉,
Journal of Physical Chemistry C 125, 15751-15757 (2021). https://DOI: 10.1021/acs.jpcc.1c05531
In this contribution we discuss the stability of clathrate structures. Clathrates are water molecules which form a host lattice structure
and encapsulates guest molecules. Up to now, all water molecules in the host lattice are considered ice-like crystallized. Here,
we discovered the occurrence of "liquid-like" water molecules and the resulting defects in (polar) tetrahydrofuran clathrates by
liquid-state 1H-NMR experiments.
Revisiting Solvent Additives for the Fabrication of Polymer: Fullerene Solar Cells: Exploring a Series of Benzaldehydes,C. Sprau, J. Kattenbusch, Y. Li, E. Müller, D. Gerthsen, R. Berger, J. J. Michels, A. Colsmann✉,
Solar Rapid Research Letters 5, 2100238 (2021). https://doi.org/10.1002/solr.202100238
The power conversion effciencies of organic solar cells delicately depend on the morphology of the light-harvesting
bulk heterojunctions. Upon deposition from solution, the formation of tailored bicontinuous networks
of polymers and fullerenes is often achieved using combinations of solvents and solvent additives. In order to
differentiate material phases by molecular fingerprints, we used a novel combination of infrared (IR) absorption
Adaptation of a styrene-acrylic acid copolymer surface to water,Xiaomei Li, Simon Silge, Alexander Saal, Gunnar Kircher, Kaloian Koynov, Rüdiger Berger✉, Hans-Jürgen Butt,
Langmuir 37, 1571-1577 (2021). https://doi.org/10.1021/acs.langmuir.0c03226
Solid surfaces, in particular polymer surfaces, are able to adapt upon contact with a liquid. Adaptation results
in an increase in contact angle hysteresis and influences the mobility of sliding drops on surfaces. To study
adaptation and its kinetics, we investigated a random copolymer composed of styrene and acrylic acid (PS/PAA).
By applying the latest adaptation theory (Butt et al. Langmuir 2018, 34, 11292), we estimated the time constant
of this adaptation process to be significant smaller than 1 s.
Treffen sich drei Phasen...Hans-Jürgen Butt und Rüdiger Berger,
Physik Journal 20 Nr. 4, 29-34 (2021). Physik Journal Ausgabe April 2021
In diesem Beitrag wenden wir uns an Physikinteressierte aus allen Bereichen der akademischen Forschung, Wirtschaft und Lehre.
In den letzten 200 Jahren ist es gelungen, wesentliche Aspekte von Benetzungsphänomenen im Gleichgewicht zu verstehen und
damit die Benetzung in vielen Fällen zu kontrollieren. Aber es liegt in weiter Ferne, dynamische Benetzung qualitativ zu
verstehen oder sogar quantitativ vorherzusagen. Um beispielsweise die Bewegung eines Tropfens auf einer schiefen Ebene
zu beschreiben, sind immer noch mehrere ad-hoc-Parameter notwendig. Es ist nicht geklärt, wie es zur Kontaktwinkelhysterese
kommt und wie sich diese kontrollieren und vorhersagen lässt. Wir beschreiben den Stand der Forschung der dynamischen Benetzung. Um diese besser zu verstehen ist es notwendig, die Physik
nahe der Kontaktlinie, an der Flüssigkeit, Festkörper und Gas aufeinandertreffen, zu betrachten.
Electrospun nanocomposite fibers from lignin and iron oxide as supercapacitor material,Pichitchai Butnoi, Autchara Pangon, Rüdiger Berger, Hans-Jürgen Butt, Varol Intasanta✉,
Journal of Materials Research and Technology 12, 2153-2167 (2021). https://doi.org/10.1016/j.jmrt.2021.04.017
Control of Electronic Properties of Functional Organic and Inorganic Materials Through Nano-Confinement,Jongkuk Ko, Rüdiger Berger, Hyemin Lee, Hyunsik Yoon✉, Jinhan Cho✉, and Kookheon Char,
Chem. Soc. Review 50, 3585-3628 (2021). https://doi.org/10.1039/D0CS01501F
How Tuning of Liquid Crystals Controls the Lateral Adhesion Force of Drop,Chia-Ming Chang✉, Alexander Saal, Rüdiger Berger✉, Hans-Jürgen Butt, Yi Hsin Lin ✉, 😨.
Publications in 2020
When and how self-cleaning of superhydrophobic surfaces works,Florian Geyer, Maria D'Acunzi, Azadeh Sharifi, Alexander Saal, Nan Gao, Anke Kaltbeitzel, Tim-Frederik Sloot, Rüdiger Berger, Hans-Jürgen Butt✉, Doris Vollmer✉, Science Advances 6, eaaw9727 (2020). doi: 10.1126/sciadv.aaw9727
We clarify how contamintations are removed from surfaces by sliding drops. We monitored the removal of individual contaminant
particles on the micron scale by confocal microscopy. We correlate this space- and time-resolved information with
measurements of the lateral friction force of the sliding drop. Hydrophilic and hydrophobic particles hardly
influence superhydrophobicity provided that the particle size
exceeds the pore size, or the thickness of the contamination falls below the height of the protrusions.
These detailed insights into self-cleaning allow the rational design of superhydrophobic surfaces that resist contamination
as demonstrated by outdoor environmental and industrial standardized contamination experiments.
⬅ The movie shows a friction force measurement of a sliding drop over a contaminated surface.
Enhanced Vertical Charge Transport of Homo- and Blended Semiconducting Polymers by Nanoconfinement,Jongkuk Ko, Youngkeol Kim, Jin Soo Kang, Rüdiger Berger✉, Hyunsik Yoon✉, and Kookheon Char✉, Advanced Materials 1908087 (2020). doi: 10.1002/adma.201908087
Here we employed the self-assembly of homo- and blended conjugated polymers in confined in nanostructures.
The resulting structures lead to high charge mobility along vertical direction for both homo- and blended conjugated polymers.
Both semicrystalline and amorphous polymers show highly increased population of face-on crystallite despite intrinsic
crystallinity of polymers. They result in more than two orders of magnitude enhanced charge mobility along vertical direction revealed
by nanoscale conductive scanning force microscopy and macroscale IV characteristic measurements.
Shuffling gait motion of an aerodynamically driven wall-bound drop,Alexander Saal, Patrick M. Seiler, Daniel Rettenmaier, Michael Ade, Ilia V. Roisman✉, Rüdiger Berger, Hans-Jürgen Butt, and Cameron Tropea,
Phys. Rev. Fluids 5, 094006 (2021). https://doi.org/10.1103/PhysRevFluids.5.094006
Hygroscopic Properties of NaCl Nanoparticles on the Surface: A Scanning Force Microscopy Study,Xiaoxiang Wang, Haozhi Lei, Rüdiger Berger✉, Yi Zhang, Hang Su, Yafang Cheng✉, Phys. Chem. Chem. Phys., 22, 9967 - 9973 (2020). doi: 10.1039/D0CP00155D
Adaptive Wetting of Polydimethylsiloxane,William S.Y. Wong, Lukas Hauer, Abhinav Naga, Anke Kaltbeitzel, Philipp Baumli, Rüdiger Berger, Maria D‘Acunzi, Doris Vollmer, and Hans-Jürgen Butt✉, Langmuir, 36, 7236 - 7245 (2020). doi: 10.1021/acs.langmuir.0c00538
Vitamin C loaded polyethylene - synthesis and properties of precise polyethylene with vitamin C defects via acyclic diene metathesis polycondensation,Oksana Suraev, Carole Champanha, Frederik R. Wurm, Henning Weiss, Rüdiger Berger, Markus Mezger, Katharina Landfester, Ingo Lieberwirth✉, Macromolecules, 53, 2932 - 2941 (2020). https://doi.org/10.1021/acs.macromol.0c00086
Entangled Azobenzene-Containing Polymers with Photoinduced Reversible Solid-to-Liquid Transitions for Healable and Reprocessable Photoactuators,Mingsen Chen, Bingjian Yao, Michael Kappl, Senyang Liu, Jinying Yuan, Rüdiger Berger, Faai Zhang✉, Hans-Jürgen Butt, Yuanli Liu, Si Wu✉, Advanced Functional Materials, 30, 1906752 (2020). doi: 10.1002/adfm.201906752
Premelting-Induced Agglomeration of Hydrates: Theoretical Analysis and Modelling,Ngoc Nguyen✉, Rüdiger Berger, Hans-Jürgen Butt✉, ACS Appl. Mater. Interfaces, 12, 14599 - 14606 (2020). https://doi.org/10.1021/acsami.0c00636
Publications in 2019
Book Review:Berger, R. (2019). Kelvin Probe Force Microscopy: From Single Charge Detection to Device Characterization, Second Volume Sascha Sadewasser and Thilo Glatzel (Eds.), Springer Series in Surface Sciences, Book 65, 2018, 521 pp. ISBN: 9783319756868. Microscopy and Microanalysis, 25(6), 1509-1510. doi:10.1017/S1431927619015083, Microscopy and Microanalysis 25(6), 1509-1510 (2019). doi:10.1017/S1431927619015083
When you hold this 1 kg heavy book in your hand you may say: "It is so thick and heavy, is it worth the effort of carrying the book home and reading it? Why bother?
After all, this is only a book describing Kelvin probe force microscopy. Yet another mode from the plethora
of modes that are known for scanning force microscopy. No one should care!"
My daughter liked it and I like the book.
⬅ thanks to Katharina Maisenbacher (MPI-P) for the drawing. I like it!
Surface Pre-melting and Interfacial Interactions of Clathrate Hydrate,Ngoc N. Nguyen✉, Rüdiger Berger, Hans-Jürgen Butt✉, J. Phys. Chem. C 123, 39, 24080 - 24086 (2019). doi: 10.1021/acs.jpcc.9b06376
We measured the forces between a semi-clathrate hydrate formed by tetrabutyl ammonium bromide and a silica microsphere
in air and in undecane. Significantly, the analyses of jump-in (attractive) and pull-off (adhesive) forces in
force-distance curves indicate the presence of a quasi-liquid layer (QLL) on the hydrate surface resulting from
interfacial premelting. We have shown that interfacial forces between the sphere and the hydrate surface are dominated
by the capillary formation between the QLL and the sphere. The thickness of the QLL on the hydrate surface is around 11 nm
at -4 °C.
Two-Stage Collapse of PNIPAM Brushes: Viscoelastic Changes Revealed by an Interferometric Laser Technique,David van Duinen, Hans-Jürgen Butt, and Rüdiger Berger✉, Langmuir 35, 15776 - 15783 (2019). doi: 10.1021/acs.langmuir.9b03205
We studied the viscoelastic changes of a poly(N-isopropylacryamide) (PNIPAM) brush layers (51 ± 3 nm thick) with an interferometric laser
method at different temperatures. With this method we were able to investigate the two-stage collapse of beads coated with a
polymer brush layer. The change of the Brownian motion spectrum with temperature indicates two transitions of the PNIPAM brush
layer, one at 36 °C and one at 46 °C. We attribute the first transition to the LCST volume collapse of PNIPAM. The second
transition is dominated by a stiffening of the brush layer.
Critical analysis of Micro-Thermogravimetry of CuSO4 · 5H2O crystals using heatable Microcantilevers,Nikhilendu Tiwary, Marjan Zakerin, Filipe Natalio, Eugen Biegler, Fritzsche Marco, Hermann Kaubitzsch, Apurba Laha, Rüdiger Berger✉, V. Ramgopal Rao✉, Journal of Micromechanics and Microengineering 29, 105009 (2019). doi:10.1088/1361-6439/ab30a3
We have critically analysed Micro/nano thermogravimetry (TG) method.
In cooperation with the Indian Institute of Technology we have designed and fabricated a microelectromechanical
thermogravimetric device (MMTG) with integrated microheaters and temperature sensors. The final mass
loss ratio corresponds to the theoretically expected value, although the obtained TG curve deviated
from the standard TG curve of CuSO4 · 5H2O crystals obtained from commercial TG
instruments. We attributed the deviation to the inherent temperature non-uniformity, non-isothermal conditions and
temperature gradients of metallicwire based microheaters.
⬅ The image shows a red glowing microelectromechanical thermogravimetric device.
Removal of Surface Oxygen Vacancies increases Conductance through TiO2 Thin Films for Perovskite Solar CellsAlexander Klasen, Phillip Baumli, Qu Sheng, Ewald Johannes, Simon A. Bretschneider, Ilka M. Hermes, Victor W. Bergmann, Christopher Gort, Amilie Axt, Stefan A.L. Weber, Heejae Kim, Hans-Jürgen Butt, Wolfgang Tremel, Rüdiger Berger✉,
Journal of Physical Chemistry 123, 22, 13458 - 13466 (2019). doi:10.1021/acs.jpcc.9b02371
We report that UV-ozone treatment of TiO2 anatase thin films is an efficient method to increase the
conductance through the film by more than one order of magnitude. The increase in conductance is quantified via conductive
scanning force microscopy on freshly annealed and UV-ozone treated TiO2 anatase thin films on fluorine-doped
tin oxide substrates. The increased conductance of TiO2 anatase thin films results in a 2 % increase
of the average power conversion efficiency (PCE) of methylammonium lead iodide based perovskite solar cells.
PCE values up to 19.5 % for mesoporous solar cells are realized. The additional UV-ozone treatment results in a
reduced number of oxygen vacancies at the surface, inferred from X-ray photoelectron spectroscopy (XPS). These
oxygen vacancies at the surface act as charge carrier traps and hinder charge extraction from the adjacent material.
Wie sich Tropfen bewegenFlorian Geyer, Patrick M. Seiler, Doris Vollmer, Rüdiger Berger✉,
Physik in Unserer Zeit 2, 90-96 (2019).
In diesem Beitrag wenden wir uns an Physikinteressierte aus allen Bereichen der akademischen Forschung, Wirtschaft und Lehre.
Wir beschreiben, wie Reibung zwischen einem Flüssigkeitstropfen und einer festen Oberfläche gemessen und berechnet werden kann. Im
Rahmen des Sonderforschungsbereichs 1194 Wechselseitige Beeinflussung
von Transport- und Benetzungsvorgängen erläutern wir, wie diese Grundlagenforschung mit angwandter Forschung der Automobilindustrie
Scanning probe microscopy for energy-related materialsRüdiger Berger✉, Benjamin Grévin✉, Philippe Leclère✉ and Yi Zhang✉,
Beilstein J. Nanotechnol. 10, 132-134 (2019). doi:10.3762/bjnano.10.12
The term "energy applications" refers to materials that are used for energy conversion, energy transport and
energy storage. In particular, material properties on the nanometer scale play a major role. The understanding
of these nanoscale phenomena occurring at material interfaces is therefore essential. Furthermore, these
interface phenomena are strongly linked to material properties such as grain size, roughness, mechanical
properties and work function. In an attempt to address the diversity of phenomena on the nanoscale, scanning
probe microscopy (SPM) methods play an significant role for the in-operando characterization. SPM methods
offer a plethora of operation modes beyond topography imaging, which is well reflected in the articles of
this thematic issue.
Here is a link to the full thematic issue: Scanning probe microscopy for energy-related materials
Thermodynamic approach to tailor porosity in piezoelectric polymer fibers for application in nanogenerators,Mohammad Mahdi Abolhasani, Minoo Naebe, Kamyar Shirvanimoghaddam, Hossein Fashandi, Hamid Khayyam, Matthew Joordens, Achilleas Pipertzis, Saleem Anwar, Rüdiger Berger, George Floudas, Jasper Michels, Kamal Asadi✉,
Nano Energy, 62, 594 - 600 (2019). doi: 10.1016/j.nanoen.2019.05.044
Publications in 2018
How the Formation of Interfacial Charge Causes Hysteresis in Perovskite Solar Cells,S.A.L. Weber✉, I.M. Hermes, S.H. Turren Cruz, C. Gort, V.W. Bergmann, L. Gilson, A. Hagfeldt, M. Grätzel, W. Tress, W and R. Berger,
Energy Environmental Science, 11, 2404 - 2413 (2018). doi: 10.1039/C8EE01447G
The underlying mechanism of the current-voltage hysteresis in a hybrid lead-halide perovskite
solar cell is still sketchy. We have developed a method based on Kelvin probe force microscopy that enables mapping charge
redistribution in an operating device upon a voltage- or light pulse with sub-millisecond resolution.
We observed the formation of a localized interfacial charge at the anode interface, which screened
most of the electric field in the cell. Our observation of a time-dependent ion concentration in the
perovskite layer suggests that iodide ions adsorbed and became neutralized at the hole-selective spiro-OMeTAD
electrode. Thus the formation and the release of interfacial charges is the dominating factor for
How drops start sliding over solid surfaces,Nan Gao, Florian Geyer, Dominik W. Pilat, Sanghyuk Wooh, Doris Vollmer, Hans-Jürgen Butt, Rüdiger Berger✉,
Nature Physics, 14, 191 - 196 (2018). doi: 10.1038/NPHYS4305
It has been known for more than 200 years that the maximum static friction force between
two solid surfaces is usually greater than the kinetic friction force. In contrast to solid-solid friction,
there is a lack of understanding of liquid-solid friction, i.e. the forces that impede the lateral motion of
a drop of liquid on a solid surface. Here, we report that the lateral adhesion force between a liquid drop
and a solid can be divided into a static and a kinetic regime. This striking analogy with solid-solid friction
is a generic phenomenon that holds for liquids of different polarities and surface tensions on smooth, rough
and structured surfaces.
Response of public media: Süddeutsche Zeitung, Max Planck Society, Inside Science, Wissenschaft Aktuell
Adaptive Wetting - Adaptation in Wetting,Hans-Jürgen Butt✉, Rüdiger Berger, Werner Steffen , Doris Vollmer, and Stefan A. L. Weber,
Langmuir, 34, 11292 - 11304 (2018). 10.1021/acs.langmuir.8b01783
Young's modulus of plasma-polymerized allylamine films using micromechanical cantilever sensor and laser-based surface acoustic wave techniques,Masaya Toda✉, Koji Miyake, Liqiang Chu, Marjan Zakerin, Renate Förch, Rüdiger Berger✉, Akiko N. Itakura✉,
Plasma Process Polym., e1800083 (2018). doi: 10.1002/ppap.201800083
Genetically encoded lipid-polypeptide hybrid biomaterials that exhibit temperature-triggered hierarchical self-assembly,Davoud Mozhdehi, Kelli M. Luginbuhl, Joseph R. Simon, Michael Dzuricky, Rüdiger Berger, H. Samet Varol, Fred C. Huang, Kristen L. Buehne, Nicholas R. Mayne, Isaac Weitzhandler, Mischa Bonn, Sapun H. Parekh and Ashutosh Chilkoti✉,
Nature Chemistry, 10, 496 - 505 (2018). doi.org/10.1038/s41557-018-0005-z
Spatially resolved solid-state reduction of graphene oxide thin films,Maria Morant-Minana✉, Jonas Heidler, Gunnar Glasser, Hao Lu, Rüdiger Berger, Nerea Gil-Gonzalez, Klaus Müllen, Dago de Leeuw, Kamal Asadi✉,
Materials Horizons, 5, 1176-1184 (2018). doi: 10.1039/c8mh00895g
Calcium-Induced Molecular Rearrangement of Peptide Folds Enables Biomineralization of Vaterite Calcium Carbonate,Hao Lu, Helmut Lutz, Steven J. Roeters, Matthew A. Hood, Arne Schäfer, Rafael Munoz-Espi, Rüdiger Berger, Mischa Bonn and Tobias Weidner✉,
Journal of the American Chemical Society, 140, 2793 - 2796 (2018). doi: 10.1021/jacs.8b00281
Pico-thermogravimetric material properties analysis using a diamond cantilever beam,Ioana Voiculescu✉, Meiyong Liao, Marjan Zakerin, Rüdiger Berger, Takahito Ono, Masaya Toda✉,
Sensors and Actuators A, 271, 356-363 (2018). doi: 10.1016/j.sna.2018.01.004
Engineering Proteins at Interfaces: From Complementary Characterization to Material Surfaces with Designed Functions,Svenja Morsbach, Grazia Gonella, Volker Mailänder, Seraphine Wegner, Si Wu, Tobias Weidner, Rüdiger Berger, Kaloian Koynov, Doris Vollmer, Noemi Encinas, Seah Ling Kuan, Tanja Weil, Mischa Bonn, Hans-Jürgen Butt and Katharina Landfester✉,
Angewandte Chemie, 57, 12626 - 12648 (2018).
Publications in 2017
Thiolated Lysine-Leucine Peptides Self-Assemble into Biosilica Nucleation Pits on Gold Surfaces,Hao Lu, Yeneneh Yimer, Rüdiger Berger, Mischa Bonn, Jim Pfaendtner, Tobias Weidner✉
Advanced Materials Interfaces, 4, 1700399 (2017). doi: 10.1002/admi.201700399
Thermal Characterization of Dynamic Silicon Cantilever Array Sensors by Digital Holographic Microscopy,Marjan Zakerin, Antonin Novak, Masaya Toda, Yves Emery, Filipe Natalio, Hans-Jürgen Butt, Rüdiger Berger✉
Sensors, 17, 1191 (2017). doi: 10.3390/s17061191
Photoswitching of glass transition temperatures of azobenzene-containing polymers induces reversible solid-to-liquid transitions,Hongwei Zhou, Changguo Xue, Philipp Weis, Yasuhito Suzuki, Shilin Huang, Kaloian Koynov, Günter K. Auernhammer, Rüdiger Berger, Hans-Jürgen Butt and Si Wu✉,
Nature Chemistry 9, 145 - 151 (2017). doi: 10.1038/nchem.2625
Energy Dissipation of Moving Drops on Superhydrophobic and Superoleophobic Surfaces,Hans-Jürgen Butt✉, Nan Gao, Periklis Papadopoulos, Werner Steffen, Michael Kappl, Rüdiger Berger,
Langmuir 33, 107 - 116 (2017). doi 10.1021/acs.langmuir.6b03792
Reliable Work Function Determination of Multicomponent Surfaces and Interfaces: The Role of Electrostatic Potentials in Ultraviolet Photoelectron Spectroscopy,Thorsten Schultz, Thomas Lenz, Naresh Kotadiya, Georg Heimel, Gunnar Glasser, Rüdiger Berger, Paul Blom, Patrick Amsalem, Dago de Leeuw, Norbert Koch✉,
Advanced Materials Interfaces 4, 1700324 (2017). 10.1002/admi.201700324
Publications in 2016
Local Time-Dependent Charging in a Perovskite Solar Cell,Victor Bergmann, Yunlong Guo, Hideyuki Tanaka, Ilka Hermes, Dan Li, Alexander Klasen, Simon Bretschneider, Eiichi Nakamura, Rüdiger Berger✉, Stefan Weber✉, ACS Applied Materials & Interfaces, 8 (30), 19402 - 19409 (2016). doi: 10.1021/acsami.6b04104
Efficient charge extraction within solar cells explicitly depends on the optimization of
the internal interfaces. In the case of perovskite solar cells, slow processes
happening on timescales of seconds cause hysteresis in the current-voltage characteristics. Here, we localized
and investigated these slow processes with frequency modulation Kelvin probe force microscopy (FM-KPFM) on cross
sections of planar methylammonium lead iodide (MAPI) perovskite solar cells. FM-KPFM can map the charge density
distribution and its dynamics at internal interfaces. Upon illumination, space charge layers were forming at the
interfaces to the MAPI layer within several seconds. We observed distinct differences in the charging dynamics at
interfaces of the MAPI to adjacent layers. Our results attest that more than one process is involved in
Stability of a Split-RNA-Aptamer, Capable of Streptomycin Binding,Thomas A. Nick, Tiago E. de Oliveira, Dominik W. Pilat, Felix Spenkuch, Hans-Jürgen Butt, Mark Helm✉, Paulo A. Netz✉, and Rüdiger Berger✉, Journal of Physical Chemistry Part B, 120 (27), 6479 - 6489 (2016). doi: 10.1021/acs.jpcb.6b02440
In this paper we investigated the stability of an aptamer, which is formed by two RNA-strands
and binds the antibiotic streptomycin. Molecular dynamics simulations in aqueous solution confirmed the geometry and
the pattern of hydrogen bond interactions that was derived from the crystal-structure. The result of umbrella
sampling simulations indicated a favored streptomycin-binding. Experimentally, the increase in oligonucleotide
stability upon binding of streptomycin was probed by single-molecule force spectroscopy. Rate dependent force
spectroscopy measurements revealed a decrease in the natural off-rate for the aptamer-streptomycin complex
compared to the aptamer having an empty binding pocket. The simulated binding pattern and the experimental results
led to the conclusion that hydrogen-bonds between both RNA strands mainly contribute to the decrease in natural-off
Controlled Mutual Diffusion between Fullerene and Conjugated Polymer Nanopillars in Ordered Heterojunction Solar Cells,Jongkuk Ko, Jiyun Song, Hyunsik Yoon, Taeyong Kim, Changhee Lee, Rüdiger Berger✉ and Kookheon Char✉, Advanced Materials Interfaces, 1600264 (2016). doi: 10.1002/admi.201600264
This paper descibes a new approach to control the nanomorphology of organic solar cells
in a predictable, controllable, and easily-scalable way. In particular, the nanomorphology was studied in nanostructural and
electrical properties of the pillar samples using scanning probe microscopy. Conductive scanning force microscopy
in quantitative imaging mode, applied to the pillar-based samples for the first time, allows us to establish a
clear relationship between nanomorphology, nanoelectrical property, and macroscale device performance.
Surface forces between colloidal particles at high hydrostatic pressure,D. W. Pilat, B. Pouligny, A. Best, T. A. Nick, R. Berger✉, and H.-J. Butt,
Physical Review E, 022608 (2016). doi: 10.1103/PhysRevE.93.022608
It was recently suggested that the electrostatic double-layer force between colloidal particles
might weaken at high hydrostatic pressure encountered, for example, in deep seas or during oil recovery. We have addressed
this issue by means of a specially designed optical trapping setup that allowed us to explore the interaction of a micrometer-sized
glass bead and a solid glass wall in water at hydrostatic pressures of up to 1 kbar. The setup allowed us to measure the distance
between bead and wall with a subnanometer resolution. We have determined the Debye lengths in water for salt concentrations
of 0.1 and 1 mM. We found that in the pressure range from 1 bar to 1 kbar the maximum variation of the Debye lengths was
smaller than 1 nm for both salt concentrations. Furthermore, the magnitude of the zeta potentials of the glass surfaces in water showed
no dependency on pressure.
Humidity-induced grain boundaries in MAPbI3 perovskite films,Dan Li, Simon A. Bretschneider, Victor W. Bergmann, Ilka M. Hermes, Julian Mars, Alexander Klasen, Wolfgang Tremel, Markus Mezger, Hans-Jürgen Butt, Stefan A. L. Weber, Rüdiger Berger✉,
Journal of Physical Chemistry C, 120, 6363 - 6368 (2016). doi: 10.1021/acs.jpcc.6b00335
Methylammonium halide perovskites (MAPbI3) are sensitive to humidity environments. We performed
in-situ scanning force microscope and in-situ X-ray diffraction measurements on MAPbI3 films to track changes in the film morphology
and crystal structure upon repeated exposure to a high relative humidity of 80%. The appearance of mono-hydrate diffraction peaks
(MAPbI3 H2O) coincided with the appearance of additional grain boundaries outlined as black lines in the left handed sketch. Prolonged
exposure to humidity induced more steps in the MAPbI3 films and the peak intensities of the mono-hydrated phase increased.
The mono hydrated phase was not stable under dry atmosphere and could be reversed to MAPbI3. However, the humidity induced grain boundaries
persisted. The presence of these additional grain boundaries is most likely the reason for an increase in hysteresis in JV behavior.
Nanoscale heterogeniety and workfunction variations in ZnO thin films,Anirudh Sharma, Maria Untch, Jamie S. Quinton, Rüdiger Berger✉, Gunther Andersson, David A. Lewis✉,
Applied Surface Science, 363, 516 - 521 (2016). doi: 10.1016/j.apsusc.2015.11.190
Nano-roughened, sol-gel derived polycrystalline ZnO thin films prepared by a thermal ramping procedure
were found to exhibit different work function values on a sub-micrometer scale. By Kelvin probe force microscopy (KPFM)
two distinct nanoscale regions with work function differing by over 0.1 eV were detected which did not coincide with
the nano-roughened surface topography. Such heterogeneity in the electronic properties of materials in thin film devices
can significantly influence the interfacial charge transport across materials.
Influence of the mixed organic cation ratio in lead iodide based perovskite on the performance of solar cells,Manuel Salado, Laura Calio, Rüdiger Berger, Samrana Kazim✉ and Shahzada Ahmad✉,
Physical Chemistry Chemical Physics 18, 27148 - 27157 (2016). doi: 10.1039/C6CP03851D
Ferroelastic Fingerprints in Methylammonium Lead Iodide Perovskite,Ilka Hermes, Simon Bretschneider, Victor Bergmann, Dan Li, Alexander Klasen, Julian Mars, Wolfgang Tremel, Frederik Laquai, Hans-Jürgen Butt, Markus Mezger, Rüdiger Berger, Brian Rodriguez, Stefan Weber✉,
Journal of Physical Chemistry C 10, 5724 - 5731 (2016). doi 10.1021/acs.jpcc.5b11469
Bottom-up Fabrication of Nanopatterned Polymers on DNA Origami by In-situ Atom Transfer Radical Polymerization,Yu Tokura, Yanyan Jiang, Alexander Welle, Martina H. Stenzel, Katarzyna Krzemien, Jens Michaelis, Rüdiger Berger, Christopher Barner-Kowollik, Yuzhou Wu and Tanja Weil✉,
Angewandte Chemie 128, 5786 - 5791 (2016). doi 10.1002/ange.201511761
Semifluorinated Alkanes at the Air-Water Interface: Tailoring Structure and Rheology at the Molecular Scale,Antigoni Theodoratou, Ulrich Jonas, Benoit Loppinet, Thomas Geue, Rene Stangenberg, Rabea Keller, Dan Li, Rüdiger Berger, Jan Vermant, Dimitris Vlassopoulos✉,
Langmuir 32, 3139 - 3151 (2016). doi 10.1021/acs.langmuir.5b04744