NIS 2014 - Swiss Nanoscience Institute

NIS 2014
Assembly and Investigation of Electrochemically Triggered Molecular Muscles
Yves Aeschi*, Sylvie Drayss-Orth and Marcel Mayor
Swiss Nanoscience Institute, Department of Physics, University of Basel
An amphiphilic molecular rod consisting of a hydrophilic cyclophane attached to an OPE rod has
shown to form [c2]daisy chains in polar solvents at very low concentrations [1]. To make further use of
this recognition motif and inspired by electrochemically switchable host-guest systems[2][3], a
cyclophane linked to an electroactive, hydrophobic rod bearing a TTF moiety has been designed. It is
expected to form electrochemically switchable dimers, which can contract and elongate upon
oxidation/reduction and thus act as molecular muscles. By functionalization of the hydrophobic rod
with a TMS protected acetylene these dimers are processable further by acetylene-azide click
reactions[4] to give different nano-devices such as macrocycles with electrochemically switchable
dimensions or end-capped, mechanically interlocked thiol-functionalized dimers which can be
attached to gold surfaces. This new approach enables the synthesis of novel carbon-based materials
at the nanoscale in a modular and highly flexible way.
[1] J. Rotzler, S. Drayss, O. Hampe, D. Häussinger, M. Mayor, Chem Eur J., 2013, 19, 2089-2101
[2] A. Trabolsi, A.C. Fahrenbach, S.K. Dey, A. I. Share, D. C. Friedman, S. Basu, T. B. Gasa, N. M.Khashab, S. Saha,
.
I. Aprahamian, H.A. Khatib, A. H. Flood, J.F. Stoddart, Chem Commun., 2010, 46, 871-873
[3] V. Balzani, A. Credi, G. Mattersteig, O. A. Matthews, F. M. Raymo, J. F. Stoddart, M Venturi, A. J. White,
.
D. J. Williams, J. Org. Chem., 2000, 65, 1924-1936
[4] C.R. Becer, R. Hoogenboom, U. S. Schubert, Angew. Chem. Int. Ed., 2009, 48, 4900
* Email address of presenting author
[email protected]
NIS 2014 Nano‐conditioner and dispenser for single‐cell analysis and nanocrystals deposition Stefan A. Arnold*, and T. Braun Center for Cellular Imaging and Nano Analytics (C‐CINA), Biozentrum, University of Basel, Basel, Switzerland
We have developed a new tool for the automated handling and conditioning of nanoliter volumes, and their deposition on electron permeable supports for subsequent analysis by electron micro‐
scopy (EM) 1. This new instrument is used for the following applications: i.
Single‐cell analysis: Here we combine live‐cell imaging, single‐cell lysis and visual prote‐
omics. Individual adherent eukaryotic cells are lysed by a series of electrical pulses 2; the cellular content is conditioned and “written” on EM grids. Images are recorded in the elec‐
tron microscope and analyzed to identify protein ultrastructures. ii.
Conditioning and writing of 2D and 3D nanocrystals: The setup can be used with 96‐well plates. Crystallization screens carried out in such plates can be assessed using the integrated light microscope. The nano‐conditioning and dispensing tool is then able to collect and con‐
dition minute amounts of sample from selected wells and deposit each as homogenous lay‐
er on an electron permeable support for analysis in the electron microscope or x‐ray beam line. The developed setup and the control software will be presented. Furthermore, initial results from single‐cell analysis and nanocrystals deposition experiments will be shown. 1
Kemmerling et al. J Struct Biol. 2012; 177(1):128–34 2 Arnold and Kemmerling et al., J Struct Biol. 2013; 183(3):467–73 * Email address of presenting author [email protected]
NIS 2014 Modeling catalysts on the nanometer scale: Theoretical investigation of
d‐metal dimers in their interaction with the MgO(100) surface M. Baljozović*,1, I. Pašti and S. Mentus∆ University of Belgrade, Faculty of Physical Chemistry, Studentski trg 12‐16, 11158 Belgrade, Serbia, ∆
Serbian Academy of Sciences and Arts, Knez Mihajlova 35, 11000 Belgrade, Serbia Heterogeneous catalysis embraces a vast number of processes which can be catalyzed at interfaces and which are therefore investigated both theoretically and experimentally. The interaction of bimetallic dimers, in particular of transition metals on oxide surfaces, has not been investigated systematically. Only clusters and dimers consisting of Au and Ag model catalysts were investigated. I will present data obtained through a systematic DFT study of the interaction between Ru, Rh, Ir, Pd and Pt dimers and the MgO(100) surface. Adsorption trends, the electronic structure and the mobility of the dimers have been taken into account. In regard of the established models of surface reactivity we conclude that it is possible to adjust the electronic structure and consequent reactivity of the dimers toward specific molecules or molecular fragments by choice of their composition. Our results show unequivocally the ability to optimize the interaction strength, the catalytic activity and the mobility of these dimers on the MgO(100) surface by simple modification of their composition. * Email address of presenting author [email protected]
1
Currently working on spin switching in magnetic molecules at the Laboratory for Micro and Nanotechnology, Paul Scherrer Institute. NIS 2014 Nanome
echanical Oscillatorrs for Diam
mond Spin
n‐Optomeechanics A.. Barfuss*, J. Teissier, E. N
Neu and P. M
Maletinsky Sw
wiss Nanoscien
nce Institute, D
Department o
of Physics, Uniiversity of Bassel This PhD
D project add
dresses the crossover beetween quantum mecha
anics and thee classical w
world. Its main go
oal is the co
ombination of high quaality nanome
echanical osscillators andd isolated quantum q
systems,, aiming at the preparatiion and subssequent analysis of non‐classical stattes of a macroscopic system. Nanomeechanical osccillators mad
de out of di amond fulfill requireme
ents for the preparation of high quality o
oscillators ass diamond iss characterizzed by low mass m
densityy, high mechhanical stiffn
ness and outstand
ding crystalline purity. Additionally
A
diamond hosts nitroge
en‐vacancy ((NV) centerss, which confine ssingle spins aand are charracterized byy sharp optical and spin rresonances. Both of these charaacteristics arre essential ffor successffully coupling
g nanomechhanical oscillators to the spin degree of freedom in N
NV centers. O
Our experiments exploit the responsse of an NV center’s internal states to cryystal strain, induced by the oscillato
ory motion o
of the diamoond nanomechanical oscillator. We aim at demonstra
ating this co upling for th
he first time with the gooal to determ
mine the strength
h of the coheerent spin‐strrain‐couplingg. We repo
ort on the deesign and fab
brication of ddiamond osciillators with dimensions down to the
e nanoscale and charaacterize theirr mechanical properties. Static strain experimentts at room temperaature exhibit clear signatures in the ooptical prope
erties of the ccoupled NV ccenters and allow a first quantification of the couplin
ng strength α
α. In agreement with theory, additionnal resonancces – so‐
called sid
debands ‐ arre observed ffor resonanttly driven nan
nomechanica
al oscillatorss. Observatio
ons of these sid
debands constitute a Hallmark for a ccoupled spin
n‐oscillator syystem and alllows for an additional, independ
dent determiination of α.
a) b)
b
Fig. 1: aa) Single NV
V centers (exemplarily i ndicated byy two red ciircles) are loocated on diamond d
nanomechanical osccillators. The cantilevers can be strain
ned staticallyy or driven eexternally. b)) Driving a cantileever at its meechanical eiggenfrequenccy leads to th
he observatio
on of additioonal resonan
nces, the so‐called
d sidebands ((marked by a
arrows). * Email aaddress of pre
esenting autho
or arne.bbarfuss@unib
bas.ch
NIS 2014 Polymeric Nanoreactor for Theranostic Applications Patric Baumann1*, V. Balasubramanian1, O. Onaca‐Fischer1, A. Sienkiewicz2 and C.G. Palivan1 1
Department of Chemistry, University of Basel
2
Institute of Complex Matter, EPFL Theranostic is a modern approach in medicine, which profits from its dual‐functionality – combining diagnostic with treatment. Polymeric compartments encapsulating active molecules, which serve both to detect and treat a pathologic condition act as efficient multifunctional nanoreactors. The exchange of desired molecules through the compartment membrane, a feature essential for an in situ reaction of nanoreactors, is obtained by a selective permeable membrane. A smart combination of stimulus‐responsive polymer compartments, and encapsulated active molecules supports a nanoreactor activity ‘on demand’, when the stimulus is present in their environment. We present here stimulus‐responsive nanoreactors based on encapsulated photosensitive conjugates in polymer vesicles with sizes in the nanometer domain. Upon irradiation with a specific wavelength, the photosensitive conjugates produce in situ reactive oxygen species (ROS) serving for photodynamic therapy [1]. Encapsulation of rose bengal conjugated to bovine serum albumin inside the cavity of polymer vesicles served to: i. improve the local concentration of photosensitizer, ii. protect the photosensitizer from degradation, iii. decrease its intrinsic toxicity, and iii. support the detection via the fluorescence signal of rose bengal. We selected as polymer compartments polymethyloxazoline‐b‐polydimethylsiloxane‐b‐polymethyloxazoline (PDMS‐PMOXA) because these polymer vesicles were up‐taken by various cell lines without being toxic, and possess a ROS permeable membrane [2]. ROS production was turned on/off by irradiation with a wavelength specific to the photosensitizer. ROS amount in HeLa cells increased significantly due to the activity of the nanoreactor, and induced cell death in the region where the nanoreactors were irradiated. Figure 1. Schematic representation of a stimulus responsive polymer nanoreactor serving as a source of ROS “on demand” inside HeLa cells. References: 1. P. Baumann et al; Nanoscale. 2013, 5, 217. 2. F. Axthelm et al., J. Phys. Chem. B, 2008, 112, 8211. * Email address of presenting author [email protected]
NIS 2014 Contact resonance force microscopy to determine local elastic properties
A.Bubendorf, M. Kisiel, B. Eren, P.Hümbeli, T. Glatzel, E. Meyer Department of Physics, University of Basel
The characterization of devices at the micro‐ and nanoscale, for example NEMS (Nano‐
elecromechanical systems), under stress conditions like ambient pressure or shocks but also the research of new methods for diagnosing cancerogenetic cells require fast and reliable methods with a high resolution for determining it. The common static method [1], consisting of making several indentations in the sample surfaces to get a load versus distance curve suffers from a leak of speed and spatial resolution but also destroys the sample by indentation. Alternatively, a dynamical method, the contact resonance force microscopy, is used, where the interaction of the tip of a cantilever and the surface of the sample is represented by a normal and a lateral stiffness [2], [3]. The determination of both by following the variation of the normal and lateral contact resonances by means of a PLL gives maps of the elastic properties with high resolution at reasonable speeds. [1] W.C. Oliver and G.M. Pharr, J. Mater. Res.7,1564 (1992) [2] U. Rabe 2006 Applied Scanning Probe Methods II, ed B. Bhushan and H. Fuchs(Springer) pp37–90 [3] Hurley D C and Turner J A 2007 J. Appl. Phys. 102 033509 [email protected]
NIS 2014 High‐Sensitivity Scanning Probe Microscopy With Nanowire Cantilevers
D.Cadeddu, M. Poggio, R. Warburton
Swiss Nanoscience Institute, Department of Physics, University of Basel The exquisite control on the growth of bottom‐up nanowires reached in the last years opens the door to the development of nanowire‐based devices for a wide range of applications. The possibility of obtaining long and thin nanowires with a flawless structure makes them in principle very suitable as ultra‐sensitive force transducers; such bottom‐up structures should have a much higher sensitivity than state‐of‐the‐art top‐down mechanical transducers. With the aid of a polarization‐enhanced interferometry technique, we aim to detect the thermal motion of such nanowires and thus produce thermally limited sensors with force resolutions well below the aN/(Hz)1/2. Subsequently these sensors will be integrated into a new scanning probe microscope customized for the use of nanowire cantilevers, allowing the implementation of new generation ultra‐
sensitive Scanning Probe Microscopy with possible applications including non‐contact AFM or nano‐MRI. [email protected]
NIS 2014
Design of polymer nanoreactors with triggered activity
T. Einfalt, C.G. Palivan
Department of Chemistry, University of Basel, Klingelbergstrasse 80, Basel
An efficient way to overcome many of today’s challenges in domains such as medicine, food science,
catalysis, and environmental sciences is to design and use nanoreactors as reaction spaces for active
compounds (enzymes, proteins, mimics) encapsulated/inserted in supramolecular polymer
assemblies (micelles, spheres, vesicles). In this way the active compounds are simultaneously
protected and active in situ in the confined reaction space.
Here we go one step further by designing nanoreactors with triggered activity, which are able to act
“on demand”, when a specific stimulus is present in their environment. The nanoreactors are
generated by encapsulation of enzymes in polymer vesicles with membrane permeabilized by
insertion of channel proteins specifically modified to serve as “gates”. The gates open their pore in
the presence of a stimulus, as for example acidic pH, known to be specific for inflamed and
cancerous tissue. OmpF channel protein pore is modified via EDC/Sulfo-NHS coupling, and a
hydrazone linker to serve as a pH responsive cap. Channel proteins inserted into polymer membrane
of nanoreators support the triggered activity.
[email protected]
NIS 2014 Sympathetic cooling of a micromechanical membrane via ultracold atoms
A. Faber*, A.Jöckel, M.Korppi, T.Lauber, T.Kampschulte and P.Treutlein Swiss Nanoscience Institute, Department of Physics, University of Basel In the last years hybrid quantum systems started to attract interest as potential interfaces in new quantum technologies. A mechanical element in such a system could act as a transducer between different quantum systems or might be used for metrology applications. In our experiment we create a hybrid system by coupling the motion of ultracold atoms to the vibrations of a Si3N4 membrane inside an optical cavity. The coupling is mediated by a laser beam that couples to the cavity and, at the same time, creates an optical lattice for the atoms, see Fig.1. The motion of the membrane shifts the phase of the reflected light and thereby displaces the lattice potential for the atoms. Conversely, when the atoms oscillate in the lattice they modulate the radiation pressure and thereby act on the membrane. We use this coupling to sympathetically cool the fundamental mode of the membrane down to two Kelvin by laser cooling the atoms. With cryogenic pre‐cooling and suppression of laser noise, cooling of the membrane to the quantum ground state should be feasible [1]. [1] B.Vogell et al., Phys.Rev.A 87 , 023816 (2013) Fig. 1. Membrane inside a cavity coupled to a distant atomic ensemble via a laser beam * Email address of presenting author [email protected]
NIS 2014 Nanofluidic devices for biomolecules
Michael A. Gerspach*+°, Dr. Nassir Mojarad°, Dr. Yasin Ekinci° and Prof. Thomas Pfohl+ +Department of Physical Chemistry, University of Basel
°Laboratory for Micro and Nanotechnology, Paul Scherrer Institute Nanofluidic systems can be used for various applications in biology such as sorting, fractionation, mass spectroscopy, etc. In comparison to standard microfluidic systems, nanofluidic devices provide the advantage of operation and control of smaller objects. This becomes specifically important for handling biological entities with typical dimensions of below 100 nm. In this PhD project we aim to make such devices for carrying out experiments of studying macromolecules in a controlled way. Such devices consist of channels that are several microns wide but sub micron in the axial dimension. Several complications exist in operating these systems, namely nanofabrication, optical detection, and the possibility to integrate the system for involved operations. The nanofabrication is done on Silicon dioxide, where the channels are patterned using electron‐beam lithography and etched using reactive ion etching. Optical detection is done using a coherent detection scheme called iSCAT as well as fluorescent imaging. We also plan to possibly use pumping systems for controlling the solutions that enter and exit the channels. * [email protected] NIS 2014
THE DEVELOPMENT OF A MOLECULAR HOOVER
R. Goers*, W. Meier and D. Müller
Swiss Nanoscience Institute, Department of Physics, University of Basel
The emerging field of synthetic biology aims for the creation of novel devices with functionalities not
found in nature. The NANOCELL project targets at the creation of a light-driven device which
resembles a molecular hoover.
Over the last decade, several artificial devices have emerged in research functioning as nanoreactors.
Nevertheless, the transport of molecular compounds into their reaction compartment was achieved
by passive
diffusion. By reconstitution of light-driven proton pumps together with transport proteins which
utilize the proton gradient, a fully controllable device would be achieved.
The parts required to assemble such a device are an artificial membrane, composed of coblock
polymers, exhibiting a superior mechanical stability compared to lipids, and the required membrane
proteins.
Proteorhodopsin, a type I microbial rhodopsin, pumps protons upon illumination, similar to the well
known bacteriorhodopsin. The assembly of such a device requires the use of membrane
reconstitution techniques.
In this work, a strategy relying on the subsequent solubilization of liposomes was adapted to
polymersomes and the characteristics and functionality of the resulting proteopolymersomes was
investigated using light scattering, fluorescence correlation spectroscopy and pH monitoring
techniques.
Solubilization of the polymer vesicles revealed a different mechanism compared to liposomes
governing the process. Saturation of the vesicle membrane with detergent was not observed, but a
subsequent solubilization takes place.
Proteorhodopsin was reconstituted into the polymersomes, however, a clear statement about the
functionality and orientation of the protein cannot be made.
Therefore, the adaptation of a reconstitution strategy to polymersomes, verifies its viability and
points out further strategies to improve the product.
* Email address of presenting author
[email protected]
NIS 2014 Kelvin Probe Force Microscopy Analysis of Dye Sensitised Solar Cells
G. Günzburger*a, R. Jöhra, H. Hugb, E. Meyera and T. Glatzela a) Department of Physics, University of Basel
b) DSM Nutritional Products Ltd., NRD CH, Kaiseraugst, Switzerland Dye sensitised solar cells (DSCs) are an alternative promising kind of solar cells based on the sensitation of a nanostructured wide band‐gap semiconductor with a light absorbing dye. Their advantages are inexpensive fabrication, low embodied energy and high efficiency despite indirect light irradiation. Even though DSCs are commonly based on nanoporous titania layers, studies at the nanoscale are rare. We report the investigation of bare as well as sensitised nanoporous titania‐layers for application in DSCs by Kelvin probe force microscopy (KPFM). KPFM is an advanced scanning probe microscopy technique allowing the determination of local work function variations on the nanoscale (Fig. 1). We prepared layers sensitised with the work‐standard ruthenium‐based dye (N719) and crocetin, a natural organic dye. Upon adsorption the two dyes show distinct surface‐dipoles of opposite orientation (towards the TiO2 for N719) which might explain the superior performance of N719. Furthermore, the work function of the bare‐ and the sensitised titania shows spacial variations which can be related to chemi‐ or physisorbed solvent and water present despite of the dry glove‐
box environment. Future plans include measuring of the dye TiO2 system in its native electrolyte environment instead of a dry nitrogen surrounding. This will enable us to grasp interactions and processes taking place in a DSC. Furthermore the influence of illumination on the surface charge will be studied. Figure 1: Topography (left) and work function data (right) of a TiO2 layer sensitised with crocetin. * Email address of presenting author [email protected]
NIS 2014
Realization of a Veselago Lense in ultraclean suspended graphene
Clevin Handschin*
Department of Physics, University of Basel
Graphene, a single layer of graphite, exhibits many exceptional properties, such as extreme
mechanical strength, unexpectedly high opacity, high thermal conductivity and unique electrical
properties. However, it was not before 2004 when graphene was proven to exist.
Especially the massles Dirac electrons (linear energy dispersion of the charge carriers around the Kpoint) in graphene attract a great deal of attraction. The zero effective mass of the charge carriers in
combination with a quasi-ballistic transport (a mean free path of up to several µm in pristine
graphene) allows the comparison with photons. As a consequence, effects which are known from
optics can be replicated in graphene using charge carriers instead of photons. Possible effects are
Fabry-Pérot interferometer, beam splitters or electronic lenses.
Suspending graphene has always been a tool of choice to reduce extrinsic influences in graphene
such as e.g. potential fluctuation from the SiO2, which make the Dirac point physics inaccessible.
Recent developments in suspending graphene, based on a technique using polymers (LOR) rather
than the well established, but more complicated wet-etching process of SiO2 with HF, paved the
road to more complex device designs.
Here we present the possibility to establish the electronic analogy of an optical lens having a
negative refraction index - the so called Veselago Lense. Suspended top-gates, creating a p-n
junction, are used to focus the charge carriers in the graphene.
Snell's law in optics:
sin( )
=
=
sin( )
Snell's law in electronics:
sin( )
=−
∝ √
= ℎ
sin( )
* Email address of presenting author
[email protected]
NIS 2014 Molecular diffusion in polymeric membranes F. Itel*, M. Chami2, A. Najer, D. Wu, S. Lörcher, A. Dinu, C. Palivan and W. Meier 2
Department of Physical Chemistry, University of Basel
C‐CINA Center for Cellular Imaging and Nano Analytics, University of Basel Membranes provide barriers to protect and keep active‐entities in a confined space for proper function. Artificial polymeric membranes provide several advantages over biological lipid membranes: better chemical and mechanical stability, and lower permeability over water and solutes. Even though these polymeric membranes are up to five times thicker than lipid bilayers, we are able to incorporate membrane proteins to tune the membrane for specific functions. In order to provide more detailed insight into the structural aspects, a library of amphiphilic copolymers consisting of polymethyloxazoline ‐ block ‐ polydimethylsiloxane (PMOXA‐b‐PDMS) with two different block configurations (triblock and diblock) was synthesized. In this study, giant unilamellar vesicles are used as model membranes in order to determine their membrane thicknesses and lateral diffusion of single molecules within the membrane. Fluorescence correlation spectroscopy (FCS), a single‐molecule detection method, is used to conclude about the membrane complexity at the nanoscale of by measuring polymer dynamics. Results reveal that hindered diffusion is dominating with increasing molecular weight, while free diffusion is observed for small molecular weights. In addition, the study showed that the triblock polymers are oriented in a stretched I‐
shape, while the diblock polymers form a bilayer structure. These dynamical parameters give important information about interactions at the molecular level and therefore providing conclusions when dealing with mixed protein‐polymer‐lipid systems in the future, for synthesis and applications. Figure 1. Illustration of a polymeric membrane and the diffusion of the polymeric molecules within the membrane. The amphiphilic block copolymers are composed of PMOXA‐b‐PDMS and arranged in a triblock and diblock conformation. * Email address of presenting author [email protected]
NIS 2014 Investigation of interfacial processes in dye‐sensitized solar cells by means of electrochemical impedance spectroscopy R. Jöhr*, J. Nussbaum, S. Freund, E.Meyer and T. Glatzel Department of Physics, University of Basel
Dye‐sensitized solar cells (DSCs) consist of a mesoporous titania layer that is sensitized with a dye, and an electrolyte. Both are sandwiched between two conducting glass slides. The key for the understanding of these devices lies in the interfacial processes. The surface modification of the titania causes changes in its material properties like e.g. the conduction band level. Hence, in order to investigate the interfacial processes the corresponding material combinations have to be tested under operating conditions. Impedance spectroscopy is the method of choice for this task. For interpretation and fitting of the spectra the device is described using an electrical equivalent circuit (see Fig. 1). The material parameters can then be simply extracted or calculated from the fit to the recorded spectrum. We applied impedance spectroscopy for the investigation of complete DSCs. Furthermore, we tested counter electrodes alone by using dummy cells that contained a second counter electrode instead of the photo anode. We could resolve that the difference in conversion efficiency between DSCs with the carotenoid sensitizers bixin, crocetin and torularhodin are only partially explained by conduction band shifts. The main difference was found to be the electron injection efficiency from the dye to the titania. EIS on the counter electrodes showed that the stability of the cell does not only depend on the sensitized interface but also on the counter electrode and the electrolyte species. Figure 1 : DSC device structure with the equivalent circuit used for fitting of the impedance spectroscopy data. * Email address of presenting author Res.Jö[email protected]
NIS 2014 Hydrogen production from formic acid inside E. Coli using an artificial metaloenzyme S. Keller*, M. Ringenberg, C. Tagwerker and T. Ward Swiss Nanoscience Institute, Department of Physics, University of Basel Since fossil fuel stocks are declining, society must find alternative energy sources to maintain its living standards. Renewable energies are growing, yet the storage and transport of energy is still a big issue. While living organisms use glucose as an energy source, it is not adapted as a substitute for the societal addiction to fossil fuel. Indeed, glucose is a solid and the current infrastructure to dispatch energy is based on liquids or gases. This project aims at engineering E. Coli, to convert glucose into hydrogen, Scheme 1. For this purpose, several natural enzymes are being engineered in E. Coli to produce formic acid from glucose. The decomposition of formic acid into hydrogen and carbon dioxide is most efficiently catalyzed by a man‐made catalyst. We are developing a biohybrid catalyst relying on the affinity of biotin for streptavidin. Since biotin is actively taken up by E. Coli, biotinylated metal catalysts are uptaken by bacteria and bind to streptavidin in the periplasm. The resulting metalloenzyme can be fine tuned by mutagenesis. Thus far, a biotinylated catalyst has been developed that shows reactivity in streptavidin. Current efforts are aimed at : i) implementing the reaction cascade leading from glucose to formic acid in E. coli ii) carrying out the formate decomposition in the periplasm using the biohybrid catalyst The net result of the catalytic cycle performed by the engineered E. Coli is the chemical decomposition of water into its constituents oxygen and hydrogen. Scheme 1 Engineered E. Coli cells for the production of hydrogen from glucose. The biohybrid for formate decomposition consists of mutated streptavidin combined with a biotinylated pianostool complex (left). Formate results from an enzyme cascade starting from glucose. It is exported to the periplasm where the bioyhbrid decomposes it to hydrogen and carbon dioxide (right). * Email address of presenting author [email protected]
NIS 2014 pH‐responsive nanoreactors by insertion of peptide biopores in polymer membranes M. Lomora*, P. Tanner, S. Lörcher and C.G. Palivan Department of Chemistry, University of Basel, Switzerland
Ion channel peptides play a key role in cell membranes, the control of the cell’s ion in‐ and outflux and thus, serve to maintain the stability of the cell’s internal environment, or provide specific signalling functions. Following a biomimetic approach, stimuli‐responsive nanoreactors based on polymeric supramolecular assemblies (polymersomes) can respond to changes of the environment in which they reside, such as variations of pH. Here we present our approach to engineer pH‐
responsive nanoreactors by encapsulation of active compounds inside the cavity of polymer nanovesicles, and insertion of biopores in their membrane for a rapid exchange with the environment. The first step was to insert pore forming polypeptide gramicidin (gA) in the synthetic membrane (Figure 1) of the polymer vesicles. We successfully reconstituted gA as established by a time driven fluorescence method combined with stopped‐flow spectroscopy. The second step was to encapsulate pH‐sensitive molecules in the polymer vesicles, which were simultaneously protected and active in situ (Palivan, et al.), upon the pH change inside the vesicles cavity, mediated by insertion of biopores in polymer membrane. Figure 1. Schematic representation of gramicidin (gA) functionality within the membrane of polymer vesicles containing pyranine as pH‐sensitive compound. References: C.G. Palivan; 2012; Chemical Society Reviews; 7:2800‐23. * Email address of presenting author [email protected]
NIS 2014 High efficiency stacked zone plate optics for multi‐keV X‐ray focusing 1
I. Mohacsi*, 1P. Karvinen, 1I. Vartiainen, 1V. A. Guzenko, 2A. Somogyi, 2C. M. Kewish, 2P. Mercere, 1F. Nolting, 1C. David 1
Paul Scherrer Institut, Laboratory for Micro and Nanotechnology, Villigen PSI 2
Synchrotron SOLEIL, Nanoscopium beamline, L'Orme des Merisiers Fresnel zone plate lenses are widely used optics for high resolution X‐ray nanofocusing at synchrotron light sources. Typical zone plates are fabricated with binary profile, which fundamentally limits their achievable diffraction efficiency to less than 40% ‐ in practice typically 10‐
20% is achieved. We demonstrate high efficiency nanofocusing of hard X‐rays using stacked multilevel Fresnel zone plate lens with smallest zone width of 200 nm. Our approach is to maximize the diffraction efficiency by approximating the ideal parabolic lens profile with 2, 3, 4 and 6 level zone plates. The required high aspect‐ratio nanostructures were patterned by the direct writing of PMMA by electron beam lithography and filling the mold via electroplating. To overcome manufacturing difficulties of multilevel zone plates, we stack binary and three level zone plates with an additional binary zone plate to double the number of steps. This allows us to achieve 4 and 6 level profiles, in the optical transmission function respectively. We experimentally obtained focusing efficiencies up to 53.7% with 6.5 keV photons using a compact alignment apparatus based on piezoelectric actuators. Figure 1: Left: With the near field stacking of Fresnel zone plate lens we can double the number of steps in the optical transmission function to achieve superior focusing efficiency. Right: Fabricated multilevel nickel Fresnel zone plate with 200 nm half pitch and 2.6 micron structure height. * Email address of presenting author [email protected]
NIS 2014 Chirality Transfer in 1D self‐assemblies
T. Nijs*, A. Shchyrba, …. and T.A. Jung Department of Physics, University of Basel
We performed a study via STM, XPS and DFT of the chiral molecule dicyano[7]helicene, where the cyano‐functionalization directs the on‐surface self‐assembly into 1D. We are able to change the intermolecular binding motive, from H‐bonding to metal‐coordination by the supply of the coordination centers. Moreover, the helix of the molecule flexes upon stronger binding motif and thereby affects the chirality transfer in the metal‐coordinated chains. Investigation of both enantiomers reveals a mirroring of the self‐assembly for the H‐bonded chains, however no difference is observed for the metal‐coordinated ones. These chiral building blocks are a good model system for the investigation of the chirality transfer and its control in the on‐surface self‐assemblies. * Email address of presenting author [email protected]
NIS 2014 Nuclear refrigeration for cooling electronic nanostructures on a cryogen‐free dilution refrigerator M.Palma*, D.Maradan, L. Casparis and D. Zumbühl Swiss Nanoscience Institute SNI and Department of Physics, University of Basel In the last years, many theoretical articles foreshadow the possibility to investigate new physics in semiconductor structures at ultralow temperatures. For instance, it is predicted to observe a nuclear spin ferromagnetic phase transition in GaAs interacting 2D electron systems (2DEG)[1,2]. Also full thermodynamic nuclear polarization [3] is possible at temperatures below 1 mK in an external magnetic field of 10 T. However, cooling of nanoscale devices below 1 mK is a real challenge. The main obstacles that we need to overcome to reach ultralow temperatures are the poor thermal conductance of the electrical leads at these temperatures, intrinsic heat leaks and other source of heating. To reach our goal, we designed an advanced network of 16 parallel nuclear refrigerator operated on a BlueFors pulse‐tube dilution refrigerator platform (cryogen‐free, dry system) and demonstrate nuclear refrigeration. In addition, another important issue is to develop thermometers which are able to measure the electron temperature of the 2DEG. For this reason, we are testing and implementing noise thermometers and Coulomb blockade thermometers [4]. References: [1] P. Simon and D. Loss, Phys. Rev. Lett. 98, 156401 (2007). [2] P. Simon, B. Braunecker, and D. Loss, Phys. Rev. B 77, 045108 (2008). [3] S. Chesi and D. Loss, Phys. Rev. Lett. 101, 146803 (2008). [4] L. Casparis, M. Meschke, D. Maradan, A. C. Clark, C. P. Scheller, Schwarzwälder, J. P. Pekola, and D. M. Zumbühl, Rev. Sci. Instr. 83, 083903 (2012). * [email protected]
NIS 2014 Coupling of a single nitrogen vacancy centre in diamond to a tuneable
micro‐cavity D. Riedel* 1) 2), L. Greuter 2), S. Starosielec 2), E. Neu 3), P. Maletinsky 3) and R. J. Warburton 2) 1) Swiss Nanoscience Institute, Department of Physics, University of Basel 2) Nano Photonics Group, Department of Physics, University of Basel 3) Quantum Sensing Group, Department of Physics, University of Basel A single spin in the solid‐state has potential applications in nano‐magnetometry, quantum communication and quantum information processing. The key requirements are that the spin retains its coherence over long periods of time and that there are efficient initialization, control and readout mechanisms. The electron spin associated with the nitrogen vacancy (NV) centre embedded in diamond has remarkable coherence times up to a millisecond even at room temperature. The spin can be initialized and read out by optical means, while microwaves allow for a deterministic spin‐
manipulation. However, for further advances certain drawbacks have to be overcome. The photon extraction efficiency from diamond is poor and only a small fraction of the emission occurs in the relevant zero‐phonon line, the purely electronic transition. Furthermore, the radiative recombination time is rather long. Figure 1: (a) Concept of the optical cavity: A thin membrane of single crystal diamond containing well separated NV centres is embedded in a miniaturized Fabry‐Perot cavity, consisting of two highly reflecting dielectric Bragg reflector (DBR) mirrors. The cavity mode is fed by external optical excitation using a confocal microscope, which at the same time enables detection of NV photoluminescense light. Tuneability is assured by piezo‐positioning: in z for the wavelength, in (x, y) for the antinode position. (b) Laser confocal microscope measurement of a template for the curved mirror fabricated by laser ablation on a glass substrate. The crater in the substrate is 1 µm deep with a 10 µm diameter and 10 µm radius of curvature. We propose to resolve these issues by embedding the NV in a highly miniaturized cavity of the Fabry‐
Perot type (Fig.1a), coupling the optical transition to the fundamental resonator mode. Dielectric Bragg reflector coatings induce a high reflectivity for the curved (Fig.1b) and plane cavity‐mirrors. Significantly, the micro‐cavity is tuneable in both wavelength and anti‐node position. The project involves the fabrication of ultra‐thin, ultra‐smooth membranes of single crystalline diamond containing NVs with narrow optical line widths. Constituting the active layer, this membrane will be employed for the development of a low volume, high‐Q factor and tuneable micro‐cavity. This cavity system allows for laser spectroscopy demonstrations of the cavity‐enhanced light‐matter interaction. Our project will pave the way to future spin‐photon and spin‐spin entanglements. * [email protected]
NIS 2014 Towards a hybrid Atom‐Ion trap on a chip
I. Rouse*, P. Treutlein and S. Willitsch Department of Chemistry, University of Basel
The fields of ultracold chemistry and physics have been greatly advanced by the development of miniaturized atom and ion trapping chips [1,2] allowing for previously inaccessible temperatures of trapped particles to be investigated. At present, these devices only facilitate the separate trapping of either neutral or charged particles. Macroscale hybrid systems allowing for simultaneous trapping of both neutral atoms and ions have been demonstrated allowing for the investigation of ion‐atom interactions at the milliKelvin scale. [3] A microscale trap on a chip would allow for the construction of a hybrid atom‐ion trap such that interactions between the trapped species occur at low temperatures closer to the motional ground state. Such a device also holds prospects for implementing more complex trapping architectures, considerably enhancing the scope of hybrid trap experiments. Work towards this goal is currently in the development stage, with simulations performed to design and optimise the individual components of the trap, confirm their ability to trap populations of atoms and ions and investigate how they interact with the aim of providing a useable design for experimental work. Figure 1: Schematic of the upper surface of the hybrid chip trap References: [1] Atom Chips, ed. J. Reichel and V. Vuletic, Wiley‐VCH, Weinheim, 2011 [2] M. D. Hughes, B. Lekitsch, J. A. Broersma and W. K. Hensinger, Contemporary Physics, 2011, 52, 505‐529 [3] F. H. J. Hall and S. Willitsch, Phys. Rev. Lett, 2012, 109, 233202 * Email address of presenting author [email protected]
NIS 2014
Probing the Initial Steps of Bacterial Biofilm Formation: Dynamic and
Molecular Principles of Surface Based Cell Motility and Mechanosensation
N. Sauter*, T. Pfohl and U. Jenal
Swiss Nanoscience Institute, Department of Physics, University of Basel
The asymmetric cell division of Caulobacter crescentus produces two different daughter cells: a
motile swarmer cell and a sessile stalked cell. The swarmer cell has a flagellum and a chemosensory
apparatus, while the stalked cell strongly adheres to surfaces via an exopolysaccharide adhesin.
During its life cycle, the swarmer cell differentiates into a stalked cell, causing Caulobacter to
oscillate between two different developmental and reproductive stages and making it a model
organism for the study of the molecular and cellular basis of the motile-sessile transition and surface
based growth. These transitions are highly relevant for growth and persistence of many bacteria, for
example surface colonization and biofilm formation.
Earlier studies indicate that pili and the flagellum play a critical role in the motile-sessile transition.
Also, surface attachment depends on the second messenger cyclic di-GMP. These studies led to a
model where mechanical sensing occurs by pili-mediated obstruction of the rotary motor in close
proximity to the surface. Motor obstruction is then sensed through some unknown mechanism and
transferred to the cell interior where the cyclic di-GMP level is increased and the holdfast synthesis
machinery is activated. We are using a microfluidic based optical tweezers set-up consisting of two
optical traps to probe this model and gain further insight into mechanosensation. One optical trap
will be used to catch swarmer cells and approach them to the surface of a colloidal particle which is
hold by the second trap.
References
1. P. D. Curtis, Y. V. Brun, Microbiol Mol Biol Rev 74, 13 (2010).
2. T. Schirmer, U. Jenal, Nature Rev Microbiology 7, 724 (2009).
3. A. Böhm et al., Cell 141, 107 (2010).
4. S. Furukawa, S. L. Kuchma, G. A. O'Toole, J Bacteriol 188, 1211 (2006).
5. M. Engstler et al., NNFM 119, 43 (2012); E. Stellamanns, PhD-Thesis, University of Göttingen (2011).
6. M. Koch, A. Rohrbach, Nature Photonics 6, 680 (2012).
* Email address of presenting author
[email protected]
NIS 2014
Graphene Metrology
Kishan Thodkar*, Cornelia Nef, Wangyang Fu and Michel Calame
Department of Physics, University of Basel
Graphene, a two dimensional material with sp2 hybridized carbon atoms arranged in a
honey comb lattice possesses unique electronic and mechanical properties. It is single atom thick
with zero band gap and is semi-metallic. Due to its unique properties it is possible to observe
Quantum Hall effect in graphene at room temperature (RT) [1]. The Quantum hall plateaus in
graphene have large spacing between the Landau levels in comparison to other 2DEGs; which makes
it an ideal material for quantum resistance standard defined by electron charge and Planck’s
constant. In our work we aim to explore the Quantum Hall effect (QHE) in chemically vapor
deposited (CVD) graphene. The fabricated samples are characterized using Raman spectroscopy and
electrical transport measurements. CVD graphene samples have polymeric residues due to
processing which affects its mobility. In-order to circumvent the latter mentioned drawback we plan
to perform high temperature and current annealing of samples; since annealing is helpful in
desorbing residues on graphene. We also plan to study QHE in suspended graphene samples and
draw an electrical comparison with non-suspended samples. Moreover, it is also exciting to know
that spin orbit coupling (SOC) can be observed in graphene under uniaxial strain. Theoretical studies
show that the SOC leads to internal magnetization in uniaxially strained graphene thus leading to
the manipulation of anomalous QHE [2]. The electrical and Raman characterization of one of the
Hall bar sample is as shown in figure 1a) and b).
Scale bar 5µm
a)
b)
Figure 1a) R(Ω) v/s Vg of a Hall bar sample,
1b) Raman spectrum of the sample and its 2D spectrum (inset)
References:[1] Alexander Tzalenchuk et. el, Towards a quantum resistance standard based on epitaxial graphene Nature
Nanotechnology DOI: 10.1038/NNANO.2009.474
[2] Ginetom S. Diniz, Marcos R. Guassi and Fanyao Qu, Strain Engineering of the Quantum Anomalous Hall
Effect in Graphene, arXiv:1310.4468v1 (2013).
* [email protected]
NIS 2014 Gabapentin polymorphism control using calixarene‐based monolayers a
L. Tullia,*, N. Moridia, W. Wangb, K. Hettulnenc, M. Neuburgerd, D. Vakninb and P. Shahgaldiana Institute of Chemistry and Bioanalytics, School of Life Sciences, University of Applied Sciences Northwestern Switzerland, Gründenstrasse 40, Muttenz CH‐4132, Switzerland b
Division of Material Sciences and Engineering, Iowa State University, A500 Zaffarano Hall, Ames, Iowa, USA c
Department of Chemistry, Nanoscience Center, University of Jyväskylä, P.O. Box 35, Jyväskylä FI‐40014, Finland d
Department of Chemistry, University of Basel, Klingelbergstrasse 80, Basel 4056, Switzerland Solid‐state polymorphism has a pivotal role in pharmaceutical science. Distinct polymorphic forms of active pharmaceutical ingredients (APIs) may show different physicochemical properties; this has a decisive effect on the formulation and bioavailability of drugs. Besides the modulation of the physical and chemical crystallization conditions, heterogeneous nucleation may represent an additional parameter for the control over the polymorphism of APIs. Langmuir monolayers have been widely exploited as “seeds” for the interfacial crystallization of inorganic molecules; the polymorphism of CaCO3 can be readily controlled by varying the nature of the amphiphile at the interface.1,2 Recently, we demonstrated that the compression rate of a p‐carboxycalix[4]arene‐
based monolayer markedly influences the size of the produced acetaminophen crystals.3 In this work, for the first time, we showed that the modulation of the packing density of a tetra‐dodecyl‐p‐
carboxy‐calix[4]arene monolayer allows controlling the polymorphism of gabapentin, an API used to relieve neuropathic pain. The partially compressed monolayer acts as template for the nucleation of the polymorph ɣ while the fully compressed monolayer kicks off the crystallization of the polymorph α. The 2D monolayer structure was investigated by grazing incidence X‐ray diffraction. The measurements revealed that the fully compressed monolayer possesses domains of high degree of crystallinity: this suggests that the nucleation process is driven by epitaxial growth. * Email address of presenting author [email protected]
1
Mann, S.; Heywood, B. R.; Rajam, S.; Birchall, J. D. Nature 1988, 334, 692. Volkmer, D.; Fricke, M.; Agena, C.; Mattay, J. Chem. Mater. 2004, 14, 2249. 3
Moridi, N.; Elend, D.; Danylyuk, O.; Suwinska, K.; Shahgaldian, P. Langmuir 2011, 27, 9116. 2
NIS 2014 Intermolecular stacking in isocyanide molecular junctions A.Vladyka*, M. Gantenbein†, M. Mayor†, M.Calame Department of Physics, University of Basel
† Department of Chemistry, University of Basel The field of molecular electronics is lying at the edge of physics, chemistry and biology. Single molecules are promising objects for the future nanoscale electronics. Usually molecular junctions are formed as a bridge between two metallic contacts and have only one plateau in the conductance traces, which corresponds to one peak in the conductance histogram. We investigate electrical properties of individual molecular junctions of 1,4‐diisocyanidebenzene using mechanically controllable break junction technique. Measurements demonstrate the existence of two states with almost 100% reproducibility in traces and conductance values approximately 0.01 G0 and 0.0002 G0. Two models were proposed to describe these plateaus: formation of molecular chains due to intermolecular stacking and pulling additional gold atoms from the contact due to very strong affinity of isocyano group to gold. To discover the nature of these 2 states a similar isocyanide compound with two tert‐butyl groups was synthesized and studied. Tert‐
butyl groups prevent π‐π interactions between molecules. The substituted isocyanide shows only one plateau in the corresponding histograms supporting the stacking hypothesis. However, the conductance is significantly less than expected from the length of this molecule (approx. 0.0003 G0). Figure 1. Overview of conductance of 1,4‐
diisocyanidebenzene: 1D‐histogram, conductance‐displacement histogram and selected traces. * Email address of presenting author [email protected]