Research on matter waves is a thriving field of quantum physics and has recently stimulated many investigations with electrons 1 , neutrons 2 , atoms 3 , Bose-condensed ensembles 4 , cold clusters 5 and hot molecules 6 . Coherence experiments with complex objects are of interest for exploring the transition to classical physics 7-9 , for measuring molecular properties 10 , and they have even been proposed for testing new models of space-time 11 . For matter-wave experiments with complex molecules, the strongly dispersive effect of the interaction between the diffracted molecule and the grating wall is a major challenge because it imposes enormous constraints on the velocity selection of the molecular beam 12 . Here, we describe the first experimental realization of a new set-up that solves this problem by combining the advantages of a so-called Talbot-Lau interferometer 13 with the benefits of an optical phase grating.Several methods have been developed in the past for the coherent manipulation of matter waves with de Broglie wavelengths in the nanometre and picometre range. For instance, free-standing material gratings were used in the diffraction of electrons 14 , atoms 15,16 and molecules 5,6,17 . In addition, coherent beam splitting at non-resonant standing light waves, often designated the KapitzaDirac effect, has been observed for all of these species [18][19][20] . Recent implementations of near-field interferometry 13,[21][22][23] underlined the particular advantages of the Talbot-Lau concept for experiments with massive objects: the required grating period scales only weakly (d ∼ √ l) with the de Broglie wavelength, and the design accepts beams of low spatial coherence, which makes high signals possible even for weak sources.A symmetric Talbot-Lau interferometer (TLI) consists of three identical gratings. The first one prepares the transverse coherence of the weakly collimated beam. Quantum near-field diffraction at the second nanostructure generates a periodic molecular density distribution at the position of the third mask, which represents a self-image of the second grating, if the grating separation equals a multiple of the Talbot length L T = d 2 /l. The mask can be laterally shifted to transform the molecular interference pattern into a modulation of the molecular beam intensity that is recorded behind the interferometer.In the established TLI design with three nanofabricated gratings 23 , the molecule-wall interaction with the grating bars imprints a further phase shift ϕ on the matter wave, which depends on the molecular polarizability α, the velocity v z and the distance r to the wall within the grating slit. Because of its strongly nonlinear r-dependence, this interaction restricts the interference contrast to very narrow bands of de Broglie wavelengths, as we show in Fig. 1a for the example of the fullerene C 70 . In this simulation, we use the full Casimir-Polder potential 24 , even though the long-distance (retarded) approximation, decaying as α/r 4 , closely reproduces the results. The sha...

We investigate the influence of thermally activated internal molecular dynamics on the phase shifts of matter waves inside a molecule interferometer. While de Broglie physics generally describes only the center-of-mass motion of a quantum object, our experiment demonstrates that the translational quantum phase is sensitive to dynamic conformational state changes inside the diffracted molecules. The structural flexibility of tailor-made organic particles is sufficient to admit a mixture of strongly fluctuating dipole moments. These modify the electric susceptibility and through this the quantum interference pattern in the presence of an external electric field. Detailed molecular dynamics simulations combined with density-functional theory allow us to quantify the time-dependent structural reconfigurations and to predict the ensemble-averaged square of the dipole moment which is found to be in good agreement with the interferometric result. The experiment thus opens a different perspective on matter wave interferometry, as we demonstrate here that it is possible to collect structural information about molecules even if they are delocalized over more than 100 times their own diameter. [3,4]. A quest for potential limits of the quantum superposition principle [5] has recently led to the development of near-field interferometers for complex molecules [6][7][8]. The term de Broglie interference usually describes the physics of the center-of-mass motion of a quantum particle. This is why earlier work often emphasized the need for an effective decoupling of the internal states from the external motion [9,10].The phase of the translational wave function can, however, also be influenced by the interaction between the particle's electromagnetic properties and the environment: Matter waves were successfully used for characterizing the van der Waals forces in the diffraction of atoms [11,12] a way to measure, for instance, the scalar static [16] and optical polarizability of large molecules [17,18].In our present work we demonstrate the influence of the internal configurational dynamics of switchable and flexible long molecules on the interference fringe shift inside a nearfield matter wave interferometer. We investigate, in particular, the relevance of the thermally activated internal dynamics for the de Broglie phase evolution in an inhomogeneous electric field.The general outline of the experiment is as follows: A perfluoroalkyl-functionalized azobenzene, C 30 H 12 F 30 N 2 O 4 , is tailor made to prepare objects of high mass, high vapor pressure, and high structural flexibility. The purified compound is characterized by nuclear magnetic resonance spectroscopy, mass spectrometry, and UV/vis-and IR-spectroscopy [8]. The neutral molecules are then evaporated in an effusive source at T = 470 ± 5 K which determines the mean velocity, the average internal energy, and the molecular folding dynamics in the beam. We use a gravitational filtering scheme [19] to select a near-Gaussian velocity distribution that corresponds to a ...

The synthesis of a series of shape-persistent macrocycles (SPMs) (1-4 and 6) comprising different numbers and/or spatial arrangement of meta-substituted tetrafluorobenzene and benzene subunits interlinked with diacetylenes is described. To increase their solubility, all five SPMs were functionalized by four peripheral hexyl chains. These SPMs were assembled from common diacetylene building blocks by a modular synthetic strategy based on palladium and/or copper catalyzed versions of acetylene coupling reactions (oxidative acetylene coupling and Cadiot-Chodkiewicz coupling). The aggregation properties in chloroform of SPMs 1-6 were investigated by concentration- and temperature-dependent 1H-NMR investigations and by vapour pressure osmometry studies. Aggregation constants and thermodynamic data of the process were obtained by least-squares fitting of the NMR data and by van't Hoff analysis respectively. Aggregation was only observed for SPMs 2-6 comprising electron deficient tetrafluorobenzene corner units. While dimerization was the major aggregation process for SPMs 3-6, the formation of larger aggregates in solution was only observed for SPM 2. The formation of aggregates is in all cases enthalpically driven. As the largest and the smallest enthalpic contribution and entropic loss in the series of aggregating SPMs were found for the two SPMs 3 and 4, each comprising two fluorinated corner units, the spatial arrangement of these subunits within the macrocycle seems to be at least equally important as the ratio of tetrafluorobenzene and benzene moieties. Interestingly, micro-scaled hexagonal rods were formed from SPM 3 upon heating in toluene, presumably consisting of mixtures of oligomers arising from covalently interlinked macrocycles.

International audienceDue to the increasing importance of modified electrodes for many applications in nanotechnology, including molecular electronics, bioelectronics, and sensors, there is a need to find ways to chemically attach suitable molecular films onto the electrodes. Combining the electroreduction of aryl diazonium salts with the Sonogashira cross-coupling reaction, a new modular technique to modify electrodes is presented. The new technique allows a wide range of functional groups to be introduced onto electrode surfaces with high surface coverage by the functional subunit. Various organic subunits, including redox chromophores, are successfully attached to platinum electrodes. The corresponding films are characterized using cyclic voltammetry, X-ray photoelectron spectroscopy, atomic force microscopy, and contact-angle measurements. The electroreduction of diazonium salts is successfully achieved on a broad variety of conducting and semiconducting surfaces, which shows that the technique is applicable to a broad variety of substrates

The synthesis of four shape‐switchable macrocycles comprising different peripheral substituents is described. The macrocycles 1–4 consist of m‐terphenyl semicircles interlinked by two azo joints. These macrocycles were assembled from nitro‐functionalized m‐terphenyl moieties through reductive dimerization. The semicircles were assembled through Suzuki cross‐coupling reactions. The molecular weights of the macrocycles were determined by vapour pressure osmometry, because mass spectrometry failed in the cases of 2 and 3. The E → Z photoisomerization reactions were analysed by UV/Vis spectroscopy complemented by 1H NMR studies. A very slow thermal back‐reaction indicated considerable stabilization of the Z isomer. The reduced efficiency of the thermal back‐reaction probably arises from the reduced degree of freedom due to the mechanical interlinking of the two azo groups. The photostationary state consisted of all‐Z (85 %) and all‐E isomers (15 %). The E → Z transformation induced by irradiation displayed simple exponential kinetics, which indicates pairwise switching of the two azo groups in a macrocycle, at least on the timescale under investigation. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)

The contactless conductivity detector was connected to ion chromatographs operating in both, the non-suppressed and suppressed modes and the analytical parameters of the contactless and the conventional commercial contact detectors were compared by using solutions of standards. The performance of the contactless detector in terms of reproducibility, linearity of calibration curve and detection limit was found to be largely identical to the commercial detectors in both systems. The usefulness of the new detector was further demonstrated with some real samples (tap, mineral and rain water). The contactless conductivity detector, which does not show electrode fouling and is simple in design and inexpensive, was thus found to be a suitable substitute for conventional detectors in ion chromatography.