Model systems for studying cell adhesion and biomimetic actin networks

• Dorothea Brüggemann,
• Johannes P. Frohnmayer and
• Joachim P. Spatz

Beilstein J. Nanotechnol. 2014, 5, 1193–1202, doi:10.3762/bjnano.5.131

• concentration and surface charge density of the lipid monolayer the adsorbed, filamentous actin film had a thickness between 69 and 84 Å [58]. When self-assembled actin networks were encaged in electroformed GUVs, different actin cortex structures were obtained in dependence of the GUV size: for vesicle

The study of surface wetting, nanobubbles and boundary slip with an applied voltage: A review

• Yunlu Pan,
• Bharat Bhushan and
• Xuezeng Zhao

Beilstein J. Nanotechnol. 2014, 5, 1042–1065, doi:10.3762/bjnano.5.117

• this review, the influence of an applied voltage on the surface wettability, nanobubbles, surface charge density and slip length are discussed. The contact angle (CA) and contact angle hysteresis (CAH) of a droplet of deionized (DI) water on a hydrophobic polystyrene (PS) surface were measured with

• applied direct current (DC) and alternating current (AC) voltages. The nanobubbles in DI water and three kinds of saline solution on a PS surface were imaged when a voltage was applied. The influence of the surface charge density on the nanobubbles was analyzed. Then the slip length and the electrostatic

• , boundary slip and the drag of liquid flow are summarized. With a smaller surface charge density which could be achieved by applying a voltage on the surface, larger and fewer nanobubbles, a larger slip length and a smaller drag of liquid flow could be found. Keywords: atomic force microscopy; boundary

Double layer effects in a model of proton discharge on charged electrodes

• Johannes Wiebe and
• Eckhard Spohr

Beilstein J. Nanotechnol. 2014, 5, 973–982, doi:10.3762/bjnano.5.111

• range of surface charge densities that could be simulated, an approximately exponential (or Tafel like) dependence of the microscopically defined rate on the surface charge density was found. Also, comparing a similarly constructed model for the Ag(111) surface showed that the corresponding rates for

• charge density of the platinum electrode was chosen such that discharge reactions take place on a time scale suitable for MD simulations (within a few tens or hundreds of picoseconds). Here now we augment the simulated systems by introducing one or two Na+ or Cl− ions into the aqueous double layer on the

• surface charge in contact with the pure water film was −5e, homogeneously distributed over the area of the slab (A = 2.22 × 1.923 nm2), which corresponds to a surface charge density of σ = −18.8 μC cm−2. Here, e = |e| is defined as the (positive) absolute value of the electron charge. In the systems with

Change of the work function of platinum electrodes induced by halide adsorption

• Florian Gossenberger,
• Tanglaw Roman,
• Katrin Forster-Tonigold and
• Axel Groß

Beilstein J. Nanotechnol. 2014, 5, 152–161, doi:10.3762/bjnano.5.15

• , bromine and iodine on Pt(111). The high value for the 0.5 ML calculation of iodine is due to a double layer structure of the adsorbates, caused by the larger size of iodine atoms. Charge density difference Δλ(z) for the adsorption of fluorine, chlorine, bromine, and iodine on Pt(111) at the fcc hollow

Quantum size effects in TiO₂ thin films grown by atomic layer deposition

• Massimo Tallarida,
• Chittaranjan Das and
• Dieter Schmeisser

Beilstein J. Nanotechnol. 2014, 5, 77–82, doi:10.3762/bjnano.5.7

• covalency in that model, charge transfer (CT) (from oxygen to TM) is usually adopted in order to include the atomic configurations of the TM with an extra charge density that results from hybridization. For example the purely 3d0 atomic multiplet of TiO2 is substituted by a combination of configurations, in

Many-body effects in semiconducting single-wall silicon nanotubes

• Wei Wei and
• Timo Jacob

Beilstein J. Nanotechnol. 2014, 5, 19–25, doi:10.3762/bjnano.5.2

• ), (6,6) (b) and (10,0) (c). The Fermi level is set at the top of valence band, and the arrows indicate the k point where the inter band transitions occur. Charge density of the last valence band (a) and the first conduction band (b) of (4,4) SiNT at the k point at which point direct transitions occurrs

Some reflections on the understanding of the oxygen reduction reaction at Pt(111)

• Ana M. Gómez-Marín,
• Ruben Rizo and
• Juan M. Feliu

Beilstein J. Nanotechnol. 2013, 4, 956–967, doi:10.3762/bjnano.4.108

• surface disordering kinetics has been widely studied [2][3][4][7] and the charge density data have been well approximated by a consecutive reaction mechanism that is slightly influenced by an autocatalytic step [2][3]. With this procedure, it was observed that the disordering kinetics on Pt(111) is faster

Surface passivation and optical characterization of Al₂O₃/a-SiC_x stacks on c-Si substrates

• Gema López,
• Pablo R. Ortega,
• Cristóbal Voz,
• Isidro Martín,
• Mónica Colina,
• Anna B. Morales,
• Albert Orpella and
• Ramón Alcubilla

Beilstein J. Nanotechnol. 2013, 4, 726–731, doi:10.3762/bjnano.4.82

• −1cm−2), and (ii) field-effect passivation due to a high negative fixed-charge density, Qfix (≈1012 cm−2) [5][6][7][8], which acts as an electrostatic shielding and significantly reduces the density of one type of charge carrier at the interface c-Si/Al2O3 [9][10]. In order to achieve the lowest

• authors have demonstrated that a thin interfacial SiOx layer between the c-Si and the Al2O3 film and generated during the Al2O3 deposition process, plays an important role in the formation of the negative fixed-charge density [26][27][28][29][30]. Optical properties of Al2O3 and the Al2O3/a-SiCx stack The

Large-scale atomistic and quantum-mechanical simulations of a Nafion membrane: Morphology, proton solvation and charge transport

• Pavel V. Komarov,
• Pavel G. Khalatur and
• Alexei R. Khokhlov

Beilstein J. Nanotechnol. 2013, 4, 567–587, doi:10.3762/bjnano.4.65

• to increase the size of simulated systems and use rather complex variants of DFT. We used a recently modified version of the code CP2K/Quickstep [85], which is a numerical implementation of the Gaussian and plane waves (GPW) method [90] based on the Kohn–Sham formulation of DFT. The electronic charge

• density was expanded in an auxiliary plane-wave basis at the Γ-point up to a kinetic energy cutoff of 280 Ry. The high-precision "molecular-optimized" (MOLOPT) triple basis set with a supplementary set of polarization functions (TZVP-MOLOPT-GTH) [91] was employed. This basis set was specifically optimized

3D nano-structures for laser nano-manipulation

• Gediminas Seniutinas,
• Lorenzo Rosa,
• Gediminas Gervinskas,
• Etienne Brasselet and
• Saulius Juodkazis

Beilstein J. Nanotechnol. 2013, 4, 534–541, doi:10.3762/bjnano.4.62

• , the component of E parallel to the interface is continuous. The component of D perpendicular to the interface must also be continuous, which means the perpendicular component of E must be discontinuous and generate a charge density ρ = ρb + ρf. When calculating the charge density, ρ, through the

A highly pH-sensitive nanowire field-effect transistor based on silicon on insulator

• Denis E. Presnov,
• Sergey V. Amitonov,
• Pavel A. Krutitskii,
• Valentina V. Kolybasova,
• Igor A. Devyatov,
• Vladimir A. Krupenin and
• Igor I. Soloviev

Beilstein J. Nanotechnol. 2013, 4, 330–335, doi:10.3762/bjnano.4.38

• potential inside the nanowire where σ is the surface charge density at the oxide–electrolyte interface, ρ1 is the nanowire radius, I0 the modified Bessel function of the first kind to zeroth order, and C is the off-diagonal coefficient of the capacitance matrix [18] that is responsible for the change in

• potential at the nanowire–oxide interface due to the variation in surface charge density at the oxide–electrolyte interface. This capacitance is defined by geometrical and electrical parameters of the system: where ε1, ε2, and ε3 are the relative permittivities in regions 1, 2, and 3, respectively, ρ2 = ρ1

• Equation 7. It should be noted that the response of the transistor to variation of the surface charge density in this mode is exponential [17]. Considering the estimation for the mobility of charge carriers in the inversion channel from [10] for our measurements (Figure 2) we get λ1 >> ρ1, so our

Electrospinning preparation and electrical and biological properties of ferrocene/poly(vinylpyrrolidone) composite nanofibers

• Ji-Hong Chai and
• Qing-Sheng Wu

Beilstein J. Nanotechnol. 2013, 4, 189–197, doi:10.3762/bjnano.4.19

• points and dielectric characteristics of the solvents. It has been reported that a higher charge density can be induced on the jet surface by a larger solvent dielectric constant, which fully stretches the solution jet and yields more uniform and thinner nanofibers under the electrical field [30]. The

Characterization and properties of micro- and nanowires of controlled size, composition, and geometry fabricated by electrodeposition and ion-track technology

• Maria Eugenia Toimil-Molares

Beilstein J. Nanotechnol. 2012, 3, 860–883, doi:10.3762/bjnano.3.97

Pure hydrogen low-temperature plasma exposure of HOPG and graphene: Graphane formation?

• Baran Eren,
• Dorothée Hug,
• Laurent Marot,
• Rémy Pawlak,
• Marcin Kisiel,
• Roland Steiner,
• Dominik M. Zumbühl and
• Ernst Meyer

Beilstein J. Nanotechnol. 2012, 3, 852–859, doi:10.3762/bjnano.3.96

• valence-band structure, which suggests double-sided hydrogenation. With the scanning tunneling microscopy technique, various atomic-scale charge-density patterns were observed, which may be associated with different C–H conformers. Hydrogen-LTP-exposed graphene on SiO2 has a Raman spectrum in which the D

• . Scanning tunneling microscopy In order to corroborate the discussions of spectroscopy results further, scanning tunneling microscopy (STM) was utilized. STM image of pristine HOPG consists of a hexagonal pattern generated by the charge density of the electrons [37]. After exposure to hydrogen plasma, the

Strong spin-filtering and spin-valve effects in a molecular V–C₆₀–V contact

• Mohammad Koleini and
• Mads Brandbyge

Beilstein J. Nanotechnol. 2012, 3, 589–596, doi:10.3762/bjnano.3.69

• ) present in methods with atomic orbitals basis sets, we have used plane-wave (PW) formalism as implemented in [31] for total energy calculations. In these calculations, we have been using ultrasoft pseudopotentials, with 30/300 Ry cutoff for wavefunction/charge density. Results and Discussion As an initial

Spontaneous dissociation of Co₂(CO)₈ and autocatalytic growth of Co on SiO₂: A combined experimental and theoretical investigation

• Kaliappan Muthukumar,
• Harald O. Jeschke,
• Roser Valentí,
• Evgeniya Begun,
• Johannes Schwenk,
• Fabrizio Porrati and
• Michael Huth

Beilstein J. Nanotechnol. 2012, 3, 546–555, doi:10.3762/bjnano.3.63

• C5 configurations are required. Moreover, the calculated charge density for the highest occupied valence band of Co2(CO)8 adsorbed on FOH-SiO2 and POH-SiO2 confirms that the molecule retains its character on FOH-SiO2 (compare Figure 5c and Figure 8a), but is strongly altered on the POH-SiO2 surfaces

• represent silicon, cobalt, oxygen and carbon atoms, respectively. Band decomposed charge density for the valence band maximum for Co2(CO)8 on the (a) FOH-SiO2 and (b) POH-SiO2 surfaces. Calculated adsorption energies (in eV) of Co2(CO)8 on SiO2 surfaces. Configurations marked with an asterisk change as a

Macromolecular shape and interactions in layer-by-layer assemblies within cylindrical nanopores

• Thomas D. Lazzara,
• K. H. Aaron Lau,
• Wolfgang Knoll,
• Andreas Janshoff and
• Claudia Steinem

Beilstein J. Nanotechnol. 2012, 3, 475–484, doi:10.3762/bjnano.3.54

• behavior, similar to that for a flat surface (Figure 1). Some deviations were observed for the initial deposition steps for the linear-PEs due to differences in the initial surface charge density, i.e., the number of positively charged silanes on alumina versus negatively charged thiols on gold [38]. Then

Reduced electron recombination of dye-sensitized solar cells based on TiO₂ spheres consisting of ultrathin nanosheets with [001] facet exposed

• Hongxia Wang,
• Meinan Liu,
• Cheng Yan and
• John Bell

Beilstein J. Nanotechnol. 2012, 3, 378–387, doi:10.3762/bjnano.3.44

• characteristic temperature that reflects the profile of the charge distribution in TiO2. Therefore, comparison of the change of τn and Dn in DSCs due to the different material composition should be made by using the density of charge as the reference, provided that the distribution profile of charge density is

• TiO2 material. The identical Dn also suggests that the diffusion coefficient of the free electron is the same for the two materials, according to Equation 2 [13]. It also justifies the assumption that the profile of the distribution of charge density is the same in the two types of TiO2 film. In

• kinetics of electron transport and back reaction of the corresponding DSCs is investigated. Figure 5a illustrates the chemical capacitance density of the DSCs made from paste B with and without TiCl4 treatment, as a function of the voltage. It is found that, at a constant charge density, the voltage of the

Effect of the tip state during qPlus noncontact atomic force microscopy of Si(100) at 5 K: Probing the probe

• Adam Sweetman,
• Sam Jarvis,
• Rosanna Danza and
• Philip Moriarty

Beilstein J. Nanotechnol. 2012, 3, 25–32, doi:10.3762/bjnano.3.3

• ), which is suggestive of two atoms terminating the tip and exhibiting radically different interactions with the surface, either due to different elemental composition, or a structurally distorted charge density. It should be noted that thermal drift during these scans was negligible (much less than one

Towards quantitative accuracy in first-principles transport calculations: The GW method applied to alkane/gold junctions

• Mikkel Strange and
• Kristian S. Thygesen

Beilstein J. Nanotechnol. 2011, 2, 746–754, doi:10.3762/bjnano.2.82

• effect than the HOMO–2, which can be understood from the fact that its charge density is located closer to the metallic surfaces. In the limit of an infinitely long wire the HOMO–2 will be spread out over the entire molecule and the image-charge effect should vanish. On the other hand, in this limit the

• HOMO would stay localized near the surface and therefore approach a nonzero constant image charge potential. If we model the HOMO charge density as a point charge of half an electron on each of the amine groups we can estimate this limiting constant to be 3.6/(2d) (eV·Å), where d is the distance to the

Platinum nanoparticles from size adjusted functional colloidal particles generated by a seeded emulsion polymerization process

• Nicolas Vogel,
• Ulrich Ziener,
• Achim Manzke,
• Alfred Plettl,
• Paul Ziemann,
• Johannes Biskupek,
• Clemens K. Weiss and
• Katharina Landfester

Beilstein J. Nanotechnol. 2011, 2, 459–472, doi:10.3762/bjnano.2.50

• dispersion [25][26]. On the other hand, several particle nuclei can cluster together to form a stable particle when the charge density on their surface becomes sufficiently high [25][27][29]. This particle, termed the secondary particle (shown in green color) now participates in the reaction as a new seed

Simulation of bonding effects in HRTEM images of light element materials

• Simon Kurasch,
• Jannik C. Meyer,
• Daniela Künzel,
• Axel Groß and
• Ute Kaiser

Beilstein J. Nanotechnol. 2011, 2, 394–404, doi:10.3762/bjnano.2.45

• ]. Unfortunately it was not possible to extract the total electrostatic potential directly from the pseudopotential calculation as it only offers the self consistent valence charge density but the total charge density is needed. Hence, in a second step, we used the relaxed structure to set up an all electron DFT

• calculation, and therefore we used the WIEN2k [20] DFT software. Furthermore, WIEN2k has the significant advantage that, besides offering access to the total electron charge density and corresponding X-ray scattering factors, in addition, the calculation of the total Coulomb potential (including all electrons

• linearization energies were set automatically. The effect of charge redistribution due to chemical bonding can be studied by comparing the initial charge density (before the first iteration cycle, labeled IAM) and the self-consistent charge density after the WIEN2k calculation has converged (labeled DFT). The

Influence of water on the properties of an Au/Mpy/Pd metal/molecule/metal junction

• Jan Kučera and
• Axel Groß

Beilstein J. Nanotechnol. 2011, 2, 384–393, doi:10.3762/bjnano.2.44

• of the Pdb LDOS is shifted to about −2.35 eV below Ef. Such a strong change of the density of states also indicates a substantial charge transfer between the involved constituents. This is illustrated by the charge density difference isodensity surfaces shown in Figure 5, which correspond to the

• difference between the charge density of the interacting Au/Mpy/Pd/H2O complex and the sum of the charge densities of the isolated Au/Mpy, Pd, and H2O subsystems in the same configuration. There is a strong charge rearrangement along both the N–Pdb and Pdb–O bonds indicative of the covalent character of the

• are marked with arrows. Charge density difference in an isodensity representation calculated as the difference between the charge density of the Au/Mpy/Pd/H2O complex and the sum of the charge densities of the Au/Mpy, Pd, and H2O subsystems. Blue and red surfaces depict the region of charge

The role of the cantilever in Kelvin probe force microscopy measurements

• George Elias,
• Thilo Glatzel,
• Ernst Meyer,
• Alex Schwarzman,
• Amir Boag and
• Yossi Rosenwaks

Beilstein J. Nanotechnol. 2011, 2, 252–260, doi:10.3762/bjnano.2.29

• inhomogeneous sample surface potential. Both the probe and the sample were divided into boundary elements in order to calculate their surface charge density. Unlike our previous work [7], where the probe was divided into conical and spherical elements, here we used commercial software (MSC/Patran®) in order to

• perform fast automatic meshing of an arbitrary probe geometry, including the cantilever as required in this work. The probe charge density was used as the unknown quantity to be determined in order to calculate subsequently the PSF. We use the following notations: (a) A matrix G which is a discrete

• Cinh represents the mutual capacitance density between every pair of surface and probe elements. By inserting the charge density distribution into the Maxwell stress tensor, replacing the probe potential with Vdc(r) + Vac sin(ωt), and extracting the force, we obtained the following expression for the

Defects in oxide surfaces studied by atomic force and scanning tunneling microscopy

• Thomas König,
• Georg H. Simon,
• Lars Heinke,
• Leonid Lichtenstein and
• Markus Heyde

Beilstein J. Nanotechnol. 2011, 2, 1–14, doi:10.3762/bjnano.2.1

• imaged by NC-AFM [25][30] since a color center is a hole in the MgO lattice [22]. The observed attraction of F0 centers originates from the charge density of the two trapped electrons, which are located in the center of the defect site. Due to Coulomb repulsion, the trapped electrons repel each other and

• spill out of the defect site into the vacuum [31]. Therefore, a considerably large charge density is situated above the surface. This charge density is supposed to interact with the tip resulting in a strong attraction, as presented in Figure 7. Since the doubly occupied F0 state is close to the Fermi

• level of the MgO/Ag(001) system [32], the charge density is also responsible for the strong peak in the tunneling current signal. Further insights into the interaction of tip and color center are obtained by periodic supercell DFT calculations at the level of the generalized gradient approximation as