H J Kreuzer

Publications (58)97.82 Total impact

• Article: Quantitative phase and refractive index measurements with point-source digital in-line holographic microscopy.

  M H Jericho, H J Kreuzer, M Kanka, R Riesenberg
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  ABSTRACT: Point-source digital in-line holographic microscopy with numerical reconstruction is ideally suited for quantitative phase measurements to determine optical path lengths and to extract changes in refractive index within accuracy close to 0.001 on the submicrometer length scale. This is demonstrated with simulated holograms and with detailed measurements on a number of different micrometer-sized samples such as suspended drops, optical fibers, as well as organisms of biological interest such as E. coli bacteria, HeLa cells, and fibroblast cells.
  Applied Optics 04/2012; 51(10):1503-15. · 1.41 Impact Factor
• Article: Water whiskers in high electric fields.

  M Karahka, H J Kreuzer
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  ABSTRACT: In electrostatic fields of the order of volts per Angstrom long whiskers of up to 12 water molecules form that have been observed in the field ion microscope. Here we present a detailed analysis on the basis of the density functional theory that substantiates the earlier claims. We present whisker structures and energetics, lower and upper threshold fields, and fragmentation patterns.
  Physical Chemistry Chemical Physics 06/2011; 13(23):11027-33. · 3.57 Impact Factor
• Article: Variation of the Binding Energy due to High Electrostatic Fields (NO on Rh(111))

  R. P. Madenach, G. Abend, H. J. Kreuzer, J. H. Block
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  ABSTRACT: The influence of high electrostatic field strengths (V/nm to V/A) on the binding energy has been studied by pulsed field desorption mass spectrometry (PFDMS). For this purpose the equilibrium between adsorption and thermal desorption of NO on Rh(111) has been observed as a function of temperature and field strength. — We obtained 102.6 kJ/mol for the binding energy of NO on Rh(111) which is in good agreement with TPD measurements of Bugyi and Solymosi [1]. With a negative field strength of 3 V/nm the binding energy increases about 10%, and a decrease of about the same amount was observed for a positive field of 3 V/nm. — In an attempt to understand the effect of high field strengths on binding energy, calculations of the change in electron density due to various field strengths have been performed. These calculations were carried out within density functional theory using a nonlocal spin density approximation. The change of the electron density involved in the bonding will be shown.
  Berichte der Bunsengesellschaft für physikalische Chemie. 05/2010; 97(3):353 - 355.
• Article: Reconstruction of high-resolution holographic microscopic images.

  M Kanka, R Riesenberg, H J Kreuzer
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  ABSTRACT: In in-line holographic microscopy a pinhole illuminates an object and a CCD-detector directly records the hologram in a pixel-pitch-dependent distance. A rapidly calculating exact reconstruction technique using a reorganized hologram with a low number of pixels, the tile superposition technique, is presented. The algorithm is applied on imaging of a 2 microm bead cluster, and it is compared with other reconstruction techniques. The high-contrast image corresponds to an NA of 0.7. A full 4 megapixel reconstruction with a resolution approaching the diffraction limit is possible in less than a minute. The technique is a base for high-resolution wide-field imaging by multispot illumination.
  Optics Letters 05/2009; 34(8):1162-4. · 3.40 Impact Factor
• Article: Collective diffusion in two-dimensional systems: exact analysis based on the kinetic lattice gas model.

  S H Payne, H J Kreuzer
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  ABSTRACT: Using a gradient expansion of the local microscopic particle current, in the long-time and large-scale limit, we derive an exact analytical expression for the density and temperature dependence of the diffusivity in terms of the density dependence of correlation functions on a rectangular lattice. The latter are calculated by transfer matrix methods, generalized to an adsorbate with lateral interactions and subjected to an external field. This allows an examination of the effects of generalized hopping kinetics. Where both initial and final state interactions are involved, the Reed-Ehrlich factorization, commonly assumed, cannot apply.
  Journal of Physics Condensed Matter 04/2009; 21(13):134013. · 2.55 Impact Factor
• Article: Dimerization boosts one-dimensional mobility of conformationally adapted porphyrins on a hexagonal surface atomic lattice.

  M Eichberger, M Marschall, J Reichert, A Weber-Bargioni, W Auwärter, R L C Wang, H J Kreuzer, Y Pennec, A Schiffrin, J V Barth
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  ABSTRACT: We employed temperature-controlled fast-scanning tunneling microscopy to monitor the diffusion of tetrapyridylporphyrin molecules on the Cu(111) surface. The data reveal unidirectional thermal migration of conformationally adapted monomers in the 300-360 K temperature range. Surprisingly equally oriented molecules spontaneously form dimers that feature a drastically increased one-dimensional diffusivity. The analysis of the bonding and mobility characteristics indicates that this boost is driven by a collective transport mechanism of a metallosupramolecular complex.
  Nano Letters 01/2009; 8(12):4608-13. · 13.20 Impact Factor
• Article: High resolution Talbot self-imaging applied to structural characterization of self-assembled monolayers of microspheres.

  J Garcia-Sucerquia, D C Alvarez-Palacio, H J Kreuzer
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  ABSTRACT: We report the observation of the Talbot self-imaging effect in high resolution digital in-line holographic microscopy (DIHM) and its application to structural characterization of periodic samples. Holograms of self-assembled monolayers of micron-sized polystyrene spheres are reconstructed at different image planes. The point-source method of DIHM and the consequent high lateral resolution allows the true image (object) plane to be identified. The Talbot effect is then exploited to improve the evaluation of the pitch of the assembly and to examine defects in its periodicity.
  Applied Optics 10/2008; 47(26):4723-8. · 1.41 Impact Factor
• Article: Conformational transitions in single polymer molecules modeled with a complete energy landscape: continuous two-state model.

  F Hanke, H J Kreuzer
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  ABSTRACT: An extension of the two-state Freely Jointed Chain model is presented in which the discrete energies of the two conformers are replaced by continuous functions of the conformer length. The statistical mechanics is initially developed in the Gibbs ensemble and leads to a conformational multi-state model. This is used to fit the equilibrium force-extension curve for Dextran. The continuous model also allows the use of Transfer Matrix methods to calculate all statistical properties in the Helmholtz ensemble, including thermal fluctuations. The latter are obtained with near perfect agreement to experiment.
  The European Physical Journal E 03/2007; 22(2):163-9. · 1.94 Impact Factor
• Article: Stretching of single polymer strands: A first-principles theory

  H. J. Kreuzer, M. Grunze
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  ABSTRACT: A first-principles theory based on 1) ab initio quantum-mechanical calculations of the potential energy surfaces of the polymer conformers, and 2) the proper statistical mechanics, allows the parameter-free calculation of the thermodynamic properties of single polymer strands. Applied to poly (ethylene glycol) molecules, we achieve quantitative agreement with experimental data, for both hexadecane and water solvents.
  EPL (Europhysics Letters) 01/2007; 55(5):640. · 2.17 Impact Factor
• Article: Growth of a dense polymer brush layer from solution

  M. Himmelhaus, T. Bastuck, S. Tokumitsu, M. Grunze, L. Livadaru, H. J. Kreuzer
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  ABSTRACT: The chemical grafting of alkanethiol-terminated poly(ethylene glycol) to a gold substrate from dimethylformamide solution was monitored by in situ ellipsometry for several molar concentrations. In the initial stage a layer of mushroom-like moieties forms and, on a much longer time scale, is followed by conformational conversion (and further adsorption) to a dense brush of stretched polymers. A statistical mechanical theory is presented that allows for a nonuniform grafting density and conformational conversion. It accounts fully for all observed details.
  EPL (Europhysics Letters) 01/2007; 64(3):378. · 2.17 Impact Factor
• Article: Theoretical modeling and interpretation of X-ray absorption spectra of liquid water.

  R L C Wang, H J Kreuzer, M Grunze
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  ABSTRACT: We report extensive calculations to examine the capability of theory to explain the XAS spectra of liquid water. Several aspects that enter the theoretical model are addressed, such as the quantum mechanical methods, the statistics and the XAS model. As input into our quantum mechanical calculations we will use structural information on liquid water obtained from first principles and from classical molecular dynamics simulations. As XAS models, we will examine the full core hole and the half core hole approximations to transition state theory. The quantum mechanics is performed on the basis of density functional theory. We conclude from this study that recent experimental results are fully consistent with, and can be completely explained by, present day theory, in particular, the pre-edge peak is reproduced. We also find that the average bond coordination in liquid water is 3.1 and that the assertion in a recent paper that the hydrogen bond number is much less than that cannot be substantiated. Our calculations emphasize that further advances in our understanding of water can only be made by more sophisticated spectroscopy with significantly increased resolution.
  Physical Chemistry Chemical Physics 12/2006; 8(41):4744-51. · 3.57 Impact Factor
• Article: Comment on "Reconstruction algorithm for high-numerical-aperture holograms with diffraction-limited resolution".

  J Garcia-Sucerquia, D C Alvarez-Palacio, M H Jericho, H J Kreuzer
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  ABSTRACT: We comment on a recent Letter by Zhang et al. [Opt. Lett. 31, 1633 (2006)] in which the authors proposed a reconstruction algorithm for high-numerical-aperture (NA) holograms. Such an algorithm has been available for in-line holography for more than a decade. The authors' "achievement" of high NA for digital in-line holography, NA=0.17, is below what was reported already several years ago (NA=0.30) and is considerably lower than what is routinely achieved now. We present reconstructions of holograms acquired with NAs above 0.4 in which we show maximal achievable resolution.
  Optics Letters 11/2006; 31(19):2845-7: discussion 2848. · 3.40 Impact Factor
• Source

  Available from: Norbert Kruse

  Article: Field-induced CO adsorption and formation of carbonyl waves on gold nanotips.

  T Visart de Bocarmé, N Kruse, P Gaspard, H J Kreuzer
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  ABSTRACT: We report a study of the adsorption and reaction of CO on a gold nanotip in high electrostatic fields. Field ion microscopy is used to investigate the emergence of a Au-carbonyl wave that is made visible with oxygen as the imaging gas. We set up a simple kinetic model that reproduces the adsorption wave and confirms that the presence of oxygen merely serves as an imaging gas and does not lead to field-induced oxidation of CO.
  The Journal of Chemical Physics 09/2006; 125(5):054704. · 3.33 Impact Factor
• Article: Oxygen adsorption on gold nanofacets and model clusters.

  T Visart de Bocarmé, T-D Chau, F Tielens, J Andrés, P Gaspard, R L C Wang, H J Kreuzer, N Kruse
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  ABSTRACT: We have studied oxygen interaction with Au crystals (field emitter tips) using time-resolved (atom-probe) field desorption mass spectrometry. The results demonstrate no adsorption to take place on clean Au facets under chosen conditions of pressures (p < 10(-4) m/bar) and temperatures (T = 300-350 K). Steady electric fields of 6 V/nm do not allow dissociating the oxygen molecule. The measured O2+ intensities rather reflect ionization of O2 molecules at critical distances above the Au tip surface. Certain amounts of Au-O2 complex ions can be found at the onset of Au field evaporation. Calculations by density functional theory (DFT) show weak oxygen end-on interaction with Au10 clusters (Delta E = 0.023 eV) and comparatively stronger interaction with Au1/Au(100) model surfaces (Delta E = 0.25 eV). No binding is found on {210} facets. Including (positive) electric fields in the DFT calculations leads to an increase of the activation energy for oxygen dissociation thus providing an explanation for the absence of atomic oxygen ions from the field desorption mass spectra.
  The Journal of Chemical Physics 08/2006; 125(5):054703. · 3.33 Impact Factor
• Article: Immersion digital in-line holographic microscopy.

  J Garcia-Sucerquia, Wenbo Xu, M H Jericho, H J Kreuzer
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  ABSTRACT: Digital in-line holographic microscopy is a promising new tool for high resolution imaging. We demonstrate, by using latex beads, that a considerable increase in numerical aperture, and, therefore, resolution can be achieved if the space between a source and a CCD camera chip is filled with a high refractive index medium. The high refractive index medium implies a shorter effective wavelength so that submicrometer resolution can be obtained with laser light in the visible range.
  Optics Letters 06/2006; 31(9):1211-3. · 3.40 Impact Factor
• Article: Submersible digital in-line holographic microscope

  S. K. Jericho, J. Garcia-Sucerquia, Wenbo Xu, M. H. Jericho, H. J. Kreuzer
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  ABSTRACT: Few instruments exist that can image microscopic marine organisms in their natural environment so that their locomotion mechanisms, feeding habits, and interactions with surfaces, such as biofouling, can be investigated in situ. We describe here the design and performance of a simple submersible digital in-line holographic microscope that can image organisms and their motion with micron resolution and that can be deployed from small vessels. Holograms and reconstructed images of several microscopic aquatic organisms were successfully obtained down to a depth of 20 m. Important microscope characteristics such as the effect of camera pixel size on lateral and depth resolutions as well as the maximum sample volume that can be imaged with a given resolution are discussed in detail.
  Review of Scientific Instruments 04/2006; 77(4):043706-043706-10. · 1.37 Impact Factor
• Article: ICO20:Biomedical Optics

  J. Garcia-Sucerquia, W. Xu, S. K. Jericho, M. H. Jericho, I. Tamblyn, H. J. Kreuzer
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  ABSTRACT: In recent years, in-line holography as originally proposed by Gabor, supplemented with numerical reconstruction, has been perfected to the point at which wavelength resolution both laterally and in depth is routinely achieved with light by using digital in-line holographic microscopy (DIHM). The advantages of DIHM are: (1) simplicity of the hardware (laser- pinhole-CCD camera), (2) magnification is obtained in the numerical reconstruction, (3) maximum information of the 3-D structure with a depth of field of millimeters, (4) changes in the specimen and the simultaneous motion of many species, can be followed in 4-D at the camera frame rate. We present results obtained with DIHM in biological and microfluidic applications. By taking advantage of the large depth of field and the plane-to-plane reconstruction capability of DIHM, we can produce 3D representations of the paths followed by micron-sized objects such as suspensions of microspheres and biological samples (cells, algae, protozoa, bacteria). Examples from biology include a study of the motion of bacteria in a diatom and the track of algae and paramecium. In microfluidic applications we observe micro-channel flow, motion of bubbles in water and evolution in electrolysis. The paper finishes with new results from an underwater version of DIHM.© (2006) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
  01/2006;
• Article: Physics and chemistry in high electric fields

  H. J. Kreuzer
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  ABSTRACT: Progress is reviewed in our understanding of the effects of high electrostatic fields (of the order of volts per angstrom) on the adsorption and reaction of atoms and molecules on metal surfaces. New results are presented for polymers in high fields, reporting a large electrostriction for oligo(ethylene glycol). The discovery by Block and his collaborators close to two decades ago that polymerized sulphur can be extracted from an adsorbed sulphur multilayer using high electric fields is analysed on the basis of density functional calculations. Copyright © 2004 John Wiley & Sons, Ltd.
  Surface and Interface Analysis 06/2004; 36(5‐6):372 - 379. · 1.18 Impact Factor
• Article: Confinement of a polymer chain in a tube

  L Livadaru, H J Kreuzer
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  ABSTRACT: We have adapted the transfer matrix method to the confinement of a single polymer molecule in tube-like cavities. The method is exact and numerically efficient for realistic polymer models such as the freely rotating chain and the rotational isomeric chain models. It allows us to calculate the chain end distribution function from which the longitudinal end-to-end distance and the free energy are obtained. The confinement is modelled as a cylindrical potential with soft walls or as a harmonic potential. Known scaling laws are recovered for long chains and strong confinement and new scaling behaviour is found in the intermediate regime. The effect of anchoring one chain end to a base plate of a semi-infinite tube is also studied.
  New Journal of Physics 07/2003; 5(1):95. · 4.18 Impact Factor
• Article: Tracking particles in four dimensions with in-line holographic microscopy.

  W Xu, M H Jericho, H J Kreuzer, I A Meinertzhagen
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  ABSTRACT: We describe a simple holographic method that has enabled us to capture as a single data set the trajectories of micrometer-sized objects suspended in water. By subtracting consecutive holograms of a particle suspension and then adding these difference holograms, we constructed a final data set that contains the time evolution of the particle trajectories free from spurious background interference effects. The method is illustrated by a recording of the motion of 5-10-microm diameter algae in water.
  Optics Letters 03/2003; 28(3):164-6. · 3.40 Impact Factor