Search results for "Dimer"
showing 10 items of 558 documents
Electronic Properties of Discotic LC-Materials
1996
Abstract We have made extensive studies of the charge-carrier mobilities in the discotic hexagonal mesophases of triphenylene-based discotic liquid crystals. Using the time-of-flight technique, transient photocurrents were measured yielding charge-carrier mobilities for various electric fields and temperatures. Starting from promising results obtained with the monomeric discotic liquid crystalline model compound hexapentyloxytriphenylene (H5T), we synthesized a “discotic twin” with two triphenylene units linked together by a suitable spacer. Additionally, we synthesized a discotic liquid crystalline oligomer consisting of four triphenylene units which are bound to a flexible cyclosiloxane r…
Exact solution of ‘‘hot dimer’’ adsorption in one-dimensional lattices
1993
An analytical solution for the kinetics of the ``hot-dimer'' adsorption in a one-dimensional lattice is reported. Hot dimers are molecules that dissociate after deposition, and each of the remaining monomers fly apart up to a maximum distance R from the original adsorption sites. The kinetics of this process is strongly dependent on the flying distance R. We find a particular behavior of the jamming coverage as a function of R. Monte Carlo simulation results are in agreement with such a calculation.
Photophysical properties of the triangular [Au(HNCOH)]3 complex and its dimer
2020
Rate constants for radiative and non-radiative transitions of the [Au(HNCOH)]3 complex and its dimer were calculated within the Herzberg–Teller approximation based on quantum mechanical principles. A high triplet quantum yield was estimated for the monomer. Internal conversion (IC) was found to be the major competing process to the intersystem crossing (ISC) from the lowest excited singlet state (S1) to the lowest triplet state (T1). ISC and IC from the spin-mixed 1 state also dominate the triplet relaxation process resulting in a negligible phosphorescence quantum yield for the monomer. The IC and ISC rate constants of the dimer are considerably smaller due to much lower Franck–Condon fact…
Nitrogen Gas on Graphene: Pairwise Interaction Potentials
2018
We investigate different types of potential parameters for the graphene-nitrogen interaction. Interaction energies calculated at DFT level are fitted with the semi-emperical Improved Lennard-Jones potential. Both a pseudo-atom potential and a full atomistic potential are considered. Furthermore, we consider the influence of the electrostatic part on the parameters using different charge schemes found in the literature as well as optimizing the charges ourselves. We have obtained parameters for both the nitrogen dimer and the graphene-nitrogen system. For the former, the four-charges Cracknell scheme reproduces with high precision the CCSD(T) interaction energy as well as the experimental di…
Mechanical Coupling in Gold Nanoparticles Supermolecules Revealed by Plasmon-Enhanced Ultralow Frequency Raman Spectroscopy
2016
International audience; Acoustic vibrations of assemblies of gold nanoparticles were investigated using ultralow frequency micro-Raman scattering and finite element simulations. When exciting the assemblies resonantly with the surface plasmon resonance of electromagnetically coupled nano-particles, Raman spectra present an ultralow frequency band whose frequency lies below the lowest Raman active Lamb mode of single nanoparticles that was observed. This feature was ascribed to a Raman vibration mode of gold nanoparticle " supermolecules " , that is, nanoparticles mechanically coupled by surrounding polymer molecules. Its measured frequency is inversely proportional to the nanoparticle diame…
Atomic-resolution imaging of clean and hydrogen-terminated C(100)-(2×1)diamond surfaces using noncontact AFM
2010
Received 22 April 2010; published 14 May 2010High-purity, type IIa diamond is investigated by noncontact atomic force microscopy NC-AFM .Wepresent atomic-resolution images of both the electrically conducting hydrogen-terminated C 100 - 2 1 :Hsurface and the insulating C 100 - 2 1 surface. For the hydrogen-terminated surface, a nearly square unitcell is imaged. In contrast to previous scanning tunneling microscopy experiments, NC-AFM imaging allowsboth hydrogen atoms within the unit cell to be resolved individually, indicating a symmetric dimer alignment.Upon removing the surface hydrogen, the diamond sample becomes insulating. We present atomic-resolutionimages, revealing individual C-C dim…
Time-Resolved Fourier-Transform Infrared Spectroscopy on the Inter- and Intramolecular Orientational Dynamics in Ferroelectric Liquid Crystalline Dim…
1997
On a base of time-resolved step-scan IR-spectroscopy data, we present a detailed model of the segmental reorientation during the ferroelectric and electroclinic switching of a chiral liquid crystalline dimer. We detected that the magnitude of the motion of the molecular segments differ from each other: The tilt angle is maximal for the mesogens and minimal for the ``virtual polysiloxane backbone.'' In contrast to a recently published conjecture, we prove that in the \ensuremath{\mu}s scale the responses of different molecular segments are unambiguously synchronous with each other.
Supramolecular Packing Drives Morphological Transitions of Charged Surfactant Micelles
2020
Abstract The shape and size of self‐assembled structures upon local organization of their molecular building blocks are hard to predict in the presence of long‐range interactions. Combining small‐angle X‐ray/neutron scattering data, theoretical modelling, and computer simulations, sodium dodecyl sulfate (SDS), over a broad range of concentrations and ionic strengths, was investigated. Computer simulations indicate that micellar shape changes are associated with different binding of the counterions. By employing a toy model based on point charges on a surface, and comparing it to experiments and simulations, it is demonstrated that the observed morphological changes are caused by symmetry br…
Covalently linked multimers of gold nanoclusters Au102(p-MBA)44and Au∼250(p-MBA)n
2016
We present the synthesis, separation, and characterization of covalently-bound multimers of para-mercaptobenzoic acid (p-MBA) protected gold nanoclusters. The multimers were synthesized by performing a ligand-exchange reaction of a pre-characterized Au102(p-MBA)44 nanocluster with biphenyl-4,4′-dithiol (BPDT). The reaction products were separated using gel electrophoresis yielding several distinct bands. The bands were analyzed by transmission electron microscopy (TEM) revealing monomer, dimer, and trimer fractions of the nanocluster. TEM analysis of dimers in combination with molecular dynamics simulations suggest that the nanoclusters are covalently bound via a disulfide bridge between BP…
The soluble loop BC region guides, but not dictates, the assembly of the transmembrane cytochrome b6
2017
Studying folding and assembly of naturally occurring α-helical transmembrane proteins can inspire the design of membrane proteins with defined functions. Thus far, most studies have focused on the role of membrane-integrated protein regions. However, to fully understand folding pathways and stabilization of α–helical membrane proteins, it is vital to also include the role of soluble loops. We have analyzed the impact of interhelical loops on folding, assembly and stability of the heme-containing four-helix bundle transmembrane protein cytochrome b6 that is involved in charge transfer across biomembranes. Cytochrome b6 consists of two transmembrane helical hairpins that sandwich two heme mol…