Spin-orbit-coupled Bose-Einstein condensates of rotating polar molecules

Science.gov (United States)

Deng, Y.; You, L.; Yi, S.

2018-05-01

An experimental proposal for realizing spin-orbit (SO) coupling of pseudospin 1 in the ground manifold 1Σ (υ =0 ) of (bosonic) bialkali polar molecules is presented. The three spin components are composed of the ground rotational state and two substates from the first excited rotational level. Using hyperfine resolved Raman processes through two select excited states resonantly coupled by a microwave, an effective coupling between the spin tensor and linear momentum is realized. The properties of Bose-Einstein condensates for such SO-coupled molecules exhibiting dipolar interactions are further explored. In addition to the SO-coupling-induced stripe structures, the singly and doubly quantized vortex phases are found to appear, implicating exciting opportunities for exploring novel quantum physics using SO-coupled rotating polar molecules with dipolar interactions.

Chip-based microtrap arrays for cold polar molecules

Science.gov (United States)

Hou, Shunyong; Wei, Bin; Deng, Lianzhong; Yin, Jianping

2017-12-01

Compared to the atomic chip, which has been a powerful platform to perform an astonishing range of applications from rapid Bose-Einstein condensate (BEC) production to the atomic clock, the molecular chip is only in its infant stages. Recently a one-dimensional electric lattice was demonstrated to trap polar molecules on a chip. This excellent work opens up the way to building a molecular chip laboratory. Here we propose a two-dimensional (2D) electric lattice on a chip with concise and robust structure, which is formed by arrays of squared gold wires. Arrays of microtraps that originate in the microsize electrodes offer a steep gradient and thus allow for confining both light and heavy polar molecules. Theoretical analysis and numerical calculations are performed using two types of sample molecules, N D3 and SrF, to justify the possibility of our proposal. The height of the minima of the potential wells is about 10 μm above the surface of the chip and can be easily adjusted in a wide range by changing the voltages applied on the electrodes. These microtraps offer intriguing perspectives for investigating cold molecules in periodic potentials, such as quantum computing science, low-dimensional physics, and some other possible applications amenable to magnetic or optical lattice. The 2D adjustable electric lattice is expected to act as a building block for a future gas-phase molecular chip laboratory.

[Progress in sample preparation and analytical methods for trace polar small molecules in complex samples].

Science.gov (United States)

Zhang, Qianchun; Luo, Xialin; Li, Gongke; Xiao, Xiaohua

2015-09-01

Small polar molecules such as nucleosides, amines, amino acids are important analytes in biological, food, environmental, and other fields. It is necessary to develop efficient sample preparation and sensitive analytical methods for rapid analysis of these polar small molecules in complex matrices. Some typical materials in sample preparation, including silica, polymer, carbon, boric acid and so on, are introduced in this paper. Meanwhile, the applications and developments of analytical methods of polar small molecules, such as reversed-phase liquid chromatography, hydrophilic interaction chromatography, etc., are also reviewed.

Unconventional superfluids of fermionic polar molecules in a bilayer system

Energy Technology Data Exchange (ETDEWEB)

Boudjemâa, Abdelâali, E-mail: a.boudjemaa@univhb-chlef.dz

2017-05-25

We study unconventional superfluids of fermionic polar molecules in a two-dimensional bilayer system with dipoles are head-to-tail across the layers. We analyze the critical temperature of several unconventional pairings as a function of different system parameters. The peculiar competition between the d- and the s-wave pairings is discussed. We show that the experimental observation of such unconventional superfluids requires ultralow temperatures, which opens up new possibilities to realize several topological phases. - Highlights: • Investigation of novel superfluids of fermionic polar molecules in a bilayer geometry. • Solving the gap equation and the l-wave interlayer scattering problem. • Calculation of the critical temperature of several competing pairings using the BCS approach.

Polarization dependent effects in photo-fragmentation dynamics of free molecules

International Nuclear Information System (INIS)

Mocellin, A.; Marinho, R.R.T.; Coutinho, L.H.; Burmeister, F.; Wiesner, K.; Naves de Brito, A.

2003-01-01

We present multicoincidence spectra of nitrogen, formic acid and methyl methacrylate. We demonstrate how to probe the local symmetry of molecular orbitals from molecules core excited with linearly polarized synchrotron radiation. The intensity distribution of the photoelectron photo-ion photo-ion coincidence (PEPIPICO) spectrum reflects the selectivity and localization of core excitation by polarized light. By simulating the spectra the angular dependence of the fragmentation is determined

Polarization dependent effects in photo-fragmentation dynamics of free molecules

Energy Technology Data Exchange (ETDEWEB)

Mocellin, A.; Marinho, R.R.T.; Coutinho, L.H.; Burmeister, F.; Wiesner, K.; Naves de Brito, A

2003-04-01

We present multicoincidence spectra of nitrogen, formic acid and methyl methacrylate. We demonstrate how to probe the local symmetry of molecular orbitals from molecules core excited with linearly polarized synchrotron radiation. The intensity distribution of the photoelectron photo-ion photo-ion coincidence (PEPIPICO) spectrum reflects the selectivity and localization of core excitation by polarized light. By simulating the spectra the angular dependence of the fragmentation is determined.

Biradical and triradical organic magnetic molecules as spin filters and rectifiers

International Nuclear Information System (INIS)

Zhu, L.; Yao, K.L.; Liu, Z.L.

2012-01-01

Graphical abstract: (a) Negative differential resistance (NDR) characteristic and antiparallel spin-current (ASC) rectification; (b) spin-current (SC) rectification and charge-current (CC) rectification properties Display Omitted Highlights: ► Organic magnetic molecules at gold electrodes as spin/charge rectifier. ► Spin diode/rectification stems from length and asymmetry of molecular framework. ► Negative differential resistance, spin-filtering and switching evidenced. - Abstract: We have theoretically investigated the spin-polarized transport properties of molecular junctions consisting of biradical and triradical organic magnetic molecules sandwiched between two symmetric gold electrodes, respectively. It shows that these junctions function as a spin rectifier or a combination of spin and charge rectifiers with high spin rectification ratios exceeding 100, wherein the spin diode/rectification effect stems from the conjugated length and asymmetry of the molecular framework, which is the pre-requisite for electronic asymmetry of the adsorbed species. The negative differential resistance, spin-filtering and switching properties are also unveiled. In particular, it is revealed that the strong couplings between the electrodes and molecules are responsible for the negative differential resistance.

Origin of the Strong Interaction between Polar Molecules and Copper(II) Paddle-Wheels in Metal Organic Frameworks.

Science.gov (United States)

Ongari, Daniele; Tiana, Davide; Stoneburner, Samuel J; Gagliardi, Laura; Smit, Berend

2017-07-20

The copper paddle-wheel is the building unit of many metal organic frameworks. Because of the ability of the copper cations to attract polar molecules, copper paddle-wheels are promising for carbon dioxide adsorption and separation. They have therefore been studied extensively, both experimentally and computationally. In this work we investigate the copper-CO 2 interaction in HKUST-1 and in two different cluster models of HKUST-1: monocopper Cu(formate) 2 and dicopper Cu 2 (formate) 4 . We show that density functional theory methods severely underestimate the interaction energy between copper paddle-wheels and CO 2 , even including corrections for the dispersion forces. In contrast, a multireference wave function followed by perturbation theory to second order using the CASPT2 method correctly describes this interaction. The restricted open-shell Møller-Plesset 2 method (ROS-MP2, equivalent to (2,2) CASPT2) was also found to be adequate in describing the system and used to develop a novel force field. Our parametrization is able to predict the experimental CO 2 adsorption isotherms in HKUST-1, and it is shown to be transferable to other copper paddle-wheel systems.

Modeling self-organization of novel organic materials

Science.gov (United States)

Sayar, Mehmet

In this thesis, the structural organization of oligomeric multi-block molecules is analyzed by computational analysis of coarse-grained models. These molecules form nanostructures with different dimensionalities, and the nanostructured nature of these materials leads to novel structural properties at different length scales. Previously, a number of oligomeric triblock rodcoil molecules have been shown to self-organize into mushroom shaped noncentrosymmetric nanostructures. Interestingly, thin films of these molecules contain polar domains and a finite macroscopic polarization. However, the fully polarized state is not the equilibrium state. In the first chapter, by solving a model with dipolar and Ising-like short range interactions, we show that polar domains are stable in films composed of aggregates as opposed to isolated molecules. Unlike classical molecular systems, these nanoaggregates have large intralayer spacings (a ≈ 6 nm), leading to a reduction in the repulsive dipolar interactions that oppose polar order within layers. This enables the formation of a striped pattern with polar domains of alternating directions. The energies of the possible structures at zero temperature are computed exactly and results of Monte Carlo simulations are provided at non-zero temperatures. In the second chapter, the macroscopic polarization of such nanostructured films is analyzed in the presence of a short range surface interaction. The surface interaction leads to a periodic domain structure where the balance between the up and down domains is broken, and therefore films of finite thickness have a net macroscopic polarization. The polarization per unit volume is a function of film thickness and strength of the surface interaction. Finally, in chapter three, self-organization of organic molecules into a network of one dimensional objects is analyzed. Multi-block organic dendron rodcoil molecules were found to self-organize into supramolecular nanoribbons (threads) and

Spectroscopic imaging studies of nanoscale polarity and mass transport phenomena in self-assembled organic nanotubes.

Science.gov (United States)

Xu, Hao; Nagasaka, Shinobu; Kameta, Naohiro; Masuda, Mitsutoshi; Ito, Takashi; Higgins, Daniel A

2017-08-02

Synthetic organic nanotubes self-assembled from bolaamphiphile surfactants are now being explored for use as drug delivery vehicles. In this work, several factors important to their implementation in drug delivery are explored. All experiments are performed with the nanotubes immersed in ethanol. First, Nile Red (NR) and a hydroxylated Nile Red derivative (NR-OH) are loaded into the nanotubes and spectroscopic fluorescence imaging methods are used to determine the apparent dielectric constant of their local environment. Both are found in relatively nonpolar environments, with the NR-OH molecules preferring regions of relatively higher dielectric constant compared to NR. Unique two-color imaging fluorescence correlation spectroscopy (imaging FCS) measurements are then used along with the spectroscopic imaging results to deduce the dielectric properties of the environments sensed by mobile and immobile populations of probe molecules. The results reveal that mobile NR molecules pass through less polar regions, likely within the nanotube walls, while immobile NR molecules are found in more polar regions, possibly near the nanotube surfaces. In contrast, mobile and immobile NR-OH molecules are found to locate in environments of similar polarity. The imaging FCS results also provide quantitative data on the apparent diffusion coefficient for each dye. The mean diffusion coefficient for the NR dye was approximately two-fold larger than that of NR-OH. Slower diffusion by the latter could result from its additional hydrogen bonding interactions with polar triglycine, amine, and glucose moieties near the nanotube surfaces. The knowledge gained in these studies will allow for the development of nanotubes that are better engineered for applications in the controlled transport and release of uncharged, dipolar drug molecules.

Organizing and addressing magnetic molecules.

Science.gov (United States)

Gatteschi, Dante; Cornia, Andrea; Mannini, Matteo; Sessoli, Roberta

2009-04-20

Magnetic molecules ranging from simple organic radicals to single-molecule magnets (SMMs) are intensively investigated for their potential applications in molecule-based information storage and processing. The goal of this Article is to review recent achievements in the organization of magnetic molecules on surfaces and in their individual probing and manipulation. We stress that the inherent fragility and redox sensitivity of most SMM complexes, combined with the noninnocent role played by the substrate, ask for a careful evaluation of the structural and electronic properties of deposited molecules going beyond routine methods for surface analysis. Detailed magnetic information can be directly obtained using X-ray magnetic circular dichroism or newly emerging scanning probe techniques with magnetic detection capabilities.

Engineering and control of cold molecules. Making manipulating and exploiting ultra-cold polar molecules

International Nuclear Information System (INIS)

Bigelow, N.P.; Haimberger, C.; Kleinert, J.; Tscherneck, M.; Holmes, M.E.

2005-01-01

In the last 12 months several groups have demonstrated the use of photo association to create cold heteronuclear (polar) molecules. We report on the formation of translationally cold NaCs molecules starting from a laser-cooled atomic vapor of Na and Cs atoms. Colliding atoms are transferred into bound molecular states in a two-step photoactivated process. We find a translational temperature of T ≅ 260 mK. To increase the density and number of trapped atoms, dark-spot techniques are used on the MOT and a Zeeman slowed sodium beam is used to load the sodium atoms into the trap. Spectroscopy of these molecules is underway using time-of-flight ion detection and trap-loss. Initial REMPI measurements indicate that both singlet and triplet states are being populated by the spontaneous-decay driven process. We measure a rate constant for molecule formation of K NaCs = 7.43 · 10 15 cm 3 s -1 . (author)

Prospects for quantum computing with an array of ultracold polar paramagnetic molecules.

Science.gov (United States)

Karra, Mallikarjun; Sharma, Ketan; Friedrich, Bretislav; Kais, Sabre; Herschbach, Dudley

2016-03-07

Arrays of trapped ultracold molecules represent a promising platform for implementing a universal quantum computer. DeMille [Phys. Rev. Lett. 88, 067901 (2002)] has detailed a prototype design based on Stark states of polar (1)Σ molecules as qubits. Herein, we consider an array of polar (2)Σ molecules which are, in addition, inherently paramagnetic and whose Hund's case (b) free-rotor pair-eigenstates are Bell states. We show that by subjecting the array to combinations of concurrent homogeneous and inhomogeneous electric and magnetic fields, the entanglement of the array's Stark and Zeeman states can be tuned and the qubit sites addressed. Two schemes for implementing an optically controlled CNOT gate are proposed and their feasibility discussed in the face of the broadening of spectral lines due to dipole-dipole coupling and the inhomogeneity of the electric and magnetic fields.

Three dimensional alignment of molecules using elliptically polarized laser fields

DEFF Research Database (Denmark)

Larsen, J.J.; Bjerre, N.; Hald, K.

2000-01-01

We demonstrate, theoretically and experimentally, that an intense, elliptically polarized, nonresonant laser field can simultaneously force all three axes of a molecule to align along given axes fixed in space, thus inhibiting the free rotation in all three Euler angles. Theoretically, the effect...

A density-dependent switch drives stochastic clustering and polarization of signaling molecules.

Directory of Open Access Journals (Sweden)

Alexandra Jilkine

2011-11-01

Full Text Available Positive feedback plays a key role in the ability of signaling molecules to form highly localized clusters in the membrane or cytosol of cells. Such clustering can occur in the absence of localizing mechanisms such as pre-existing spatial cues, diffusional barriers, or molecular cross-linking. What prevents positive feedback from amplifying inevitable biological noise when an un-clustered "off" state is desired? And, what limits the spread of clusters when an "on" state is desired? Here, we show that a minimal positive feedback circuit provides the general principle for both suppressing and amplifying noise: below a critical density of signaling molecules, clustering switches off; above this threshold, highly localized clusters are recurrently generated. Clustering occurs only in the stochastic regime, suggesting that finite sizes of molecular populations cannot be ignored in signal transduction networks. The emergence of a dominant cluster for finite numbers of molecules is partly a phenomenon of random sampling, analogous to the fixation or loss of neutral mutations in finite populations. We refer to our model as the "neutral drift polarity model." Regulating the density of signaling molecules provides a simple mechanism for a positive feedback circuit to robustly switch between clustered and un-clustered states. The intrinsic ability of positive feedback both to create and suppress clustering is a general mechanism that could operate within diverse biological networks to create dynamic spatial organization.

3D-Printed Beam Splitter for Polar Neutral Molecules

Science.gov (United States)

Gordon, Sean D. S.; Osterwalder, Andreas

2017-04-01

We describe a macroscopic beam splitter for polar neutral molecules. A complex electrode structure is required for the beam splitter which would be very difficult to produce with traditional manufacturing methods. Instead, we make use of a nascent manufacturing technique: 3D printing of a plastic piece, followed by electroplating. This fabrication method opens a plethora of avenues for research, since 3D printing imposes practically no limitations on possible shapes, and the plating produces chemically robust, conductive construction elements with an almost free choice of surface material. It has the added advantage of dramatically reduced production cost and time. Our beam splitter is an electrostatic hexapole guide that smoothly transforms into two bent quadrupoles. We demonstrate the correct functioning of this device by separating a supersonic molecular beam of ND3 into two correlated fractions. It is shown that this device can be used to implement experiments with differential detection wherein one of the fractions serves as a probe and the other as a reference. Reverse operation would allow the merging of two beams of polar neutral molecules.

Biradical and triradical organic magnetic molecules as spin filters and rectifiers

Energy Technology Data Exchange (ETDEWEB)

Zhu, L. [School of Physics, School of Optoelectronics Science and Engineering, Wuhan Pulsed Magnetic Field Center, Huazhong University of Science and Technology, Wuhan 430074 (China); Yao, K.L., E-mail: klyao@hust.edu.cn [School of Physics, School of Optoelectronics Science and Engineering, Wuhan Pulsed Magnetic Field Center, Huazhong University of Science and Technology, Wuhan 430074 (China); International Center of Materials Physics, Chinese Academy of Science, Shengyang 110015 (China); Liu, Z.L. [School of Physics, School of Optoelectronics Science and Engineering, Wuhan Pulsed Magnetic Field Center, Huazhong University of Science and Technology, Wuhan 430074 (China)

2012-03-13

Graphical abstract: (a) Negative differential resistance (NDR) characteristic and antiparallel spin-current (ASC) rectification; (b) spin-current (SC) rectification and charge-current (CC) rectification properties Display Omitted Highlights: Black-Right-Pointing-Pointer Organic magnetic molecules at gold electrodes as spin/charge rectifier. Black-Right-Pointing-Pointer Spin diode/rectification stems from length and asymmetry of molecular framework. Black-Right-Pointing-Pointer Negative differential resistance, spin-filtering and switching evidenced. - Abstract: We have theoretically investigated the spin-polarized transport properties of molecular junctions consisting of biradical and triradical organic magnetic molecules sandwiched between two symmetric gold electrodes, respectively. It shows that these junctions function as a spin rectifier or a combination of spin and charge rectifiers with high spin rectification ratios exceeding 100, wherein the spin diode/rectification effect stems from the conjugated length and asymmetry of the molecular framework, which is the pre-requisite for electronic asymmetry of the adsorbed species. The negative differential resistance, spin-filtering and switching properties are also unveiled. In particular, it is revealed that the strong couplings between the electrodes and molecules are responsible for the negative differential resistance.

Polar and non-polar organic aerosols from large-scale agricultural-waste burning emissions in Northern India: Implications to organic mass-to-organic carbon ratio.

Science.gov (United States)

Rajput, Prashant; Sarin, M M

2014-05-01

This study focuses on characteristics of organic aerosols (polar and non-polar) and total organic mass-to-organic carbon ratio (OM/OC) from post-harvest agricultural-waste (paddy- and wheat-residue) burning emissions in Northern India. Aerosol samples from an upwind location (Patiala: 30.2°N, 76.3°E) in the Indo-Gangetic Plain were analyzed for non-polar and polar fractions of organic carbon (OC1 and OC2) and their respective mass (OM1 and OM2). On average, polar organic aerosols (OM2) contribute nearly 85% of the total organic mass (OM) from the paddy- and wheat-residue burning emissions. The water-soluble-OC (WSOC) to OC2 ratio, within the analytical uncertainty, is close to 1 from both paddy- and wheat-residue burning emissions. However, temporal variability and relatively low WSOC/OC2 ratio (Av: 0.67±0.06) is attributed to high moisture content and poor combustion efficiency during paddy-residue burning, indicating significant contribution (∼30%) of aromatic carbon to OC2. The OM/OC ratio for non-polar (OM1/OC1∼1.2) and polar organic aerosols (OM2/OC2∼2.2), hitherto unknown for open agricultural-waste burning emissions, is documented in this study. The total OM/OC ratio is nearly identical, 1.9±0.2 and 1.8±0.2, from paddy- and wheat-residue burning emissions. Copyright © 2013 Elsevier Ltd. All rights reserved.

Impact of molecular packing on electronic polarization in organic crystals: the case of pentacene vs TIPS-pentacene.

Science.gov (United States)

Ryno, Sean M; Risko, Chad; Brédas, Jean-Luc

2014-04-30

Polarization energy corresponds to the stabilization of the cation or anion state of an atom or molecule when going from the gas phase to the solid state. The decrease in ionization energy and increase in electron affinity in the solid state are related to the (electronic and nuclear) polarization of the surrounding atoms and molecules in the presence of a charged entity. Here, through a combination of molecular mechanics and quantum mechanics calculations, we evaluate the polarization energies in two prototypical organic semiconductors, pentacene and 6,13-bis(2-(tri-isopropylsilyl)ethynyl)pentacene (TIPS-pentacene). Comparison of the results for the two systems reveals the critical role played by the molecular packing configurations in the determination of the polarization energies and provides physical insight into the experimental data reported by Lichtenberger and co-workers (J. Amer. Chem. Soc. 2010, 132, 580; J. Phys. Chem. C 2010, 114, 13838). Our results underline that the impact of packing configurations, well established in the case of the charge-transport properties, also extends to the polarization properties of π-conjugated materials.

Ground state of the polar alkali-metal-atom-strontium molecules: Potential energy curve and permanent dipole moment

International Nuclear Information System (INIS)

Guerout, R.; Aymar, M.; Dulieu, O.

2010-01-01

In this study, we investigate the structure of the polar alkali-metal-atom-strontium diatomic molecules as possible candidates for the realization of samples of ultracold polar molecular species not yet investigated experimentally. Using a quantum chemistry approach based on effective core potentials and core polarization potentials, we model these systems as effective three-valence-electron systems, allowing for calculation of electronic properties with full configuration interaction. The potential curve and the permanent dipole moment of the 2 Σ + ground state are determined as functions of the internuclear distance for LiSr, NaSr, KSr, RbSr, and CsSr molecules. These molecules are found to exhibit a significant permanent dipole moment, though smaller than those of the alkali-metal-atom-Rb molecules.

Photodegradation and polarization properties of vertical external surface-emitting organic laser

International Nuclear Information System (INIS)

Leang, Tatiana

2014-01-01

Although organic solid-state dye lasers can provide wavelength tunability in the whole visible spectrum and offers perspectives of low-cost compact lasers, they are still limited by several drawbacks, especially photodegradation. The geometry of a Vertical External Cavity Surface-emitting Organic Laser (VECSOL) enables organic lasers to reach high energies, excellent conversion efficiencies and good beam quality, it also enables an external control on many parameters, a feature that we have used here to study the photodegradation phenomenon as well as some polarization properties of organic solid-state lasers. In the first part of this thesis, we studied the lifetime of the laser upon varying several parameters (pump pulse-width, repetition rate, output coupling,...) and we found that the intracavity laser intensity, independently of the pump intensity, had a major on photodegradation rate. Moreover, we observed that the profile of the laser beam was also degrading with time: while it is Gaussian in the beginning it gradually shifts to an annular shape. In the second part, we investigated the polarization properties of VECSOLs, with a special emphasis on fluorescence properties of some typical dyes used in lasers. The crucial role played by resonant non-radiative energy transfers between dye molecules (HOMO-FRET) is evidenced and enables explaining the observed fluorescence depolarization, compared to the expected limiting fluorescence anisotropy. Energy transfers happen to play a negligible role above laser threshold, as the organic laser beam is shown to be linearly polarized in a wide range of experimental conditions when excitation occurs in the first singlet state. (author) [fr

Rate coefficients for the reactions of ions with polar molecules at interstellar temperatures

International Nuclear Information System (INIS)

Adams, N.G.; Smith, D.; Clary, D.C.

1985-01-01

A theory has been developed recently which predicts that the rate coefficients, k, for the reactions of ions with polar molecules at low temperatures will be much greater than the canonical value of 10 -9 cm 3 s -1 . The new theory indicates that k is greatest for low-lying rotational sates and increases rapidly with decreasing temperature. We refer to recent laboratory measurements which validate the theory, present calculated values of k for the reactions of H + 3 ions with several polar molecules, and discuss their significance to interstellar chemistry. For the reactions of ions with molecules having large dipole moments, we recommend that k values as large as 10 -7 cm 3 s -1 should be used in ion-chemical models of low-temperature interstellar clouds

Cross sections and spin polarizations of electrons elastically scattered from oriented molecules (CH3I)

International Nuclear Information System (INIS)

Fink, M.; Ross, A.W.; Fink, R.J.

1989-01-01

Elastic differential cross sections and spin polarizations for electrons elastically scattered from CH 3 I are calculated using the independent atom model. Three molecular orientations with respect to the incident electron wavevector are considered - first, the molecule is oriented randomly, second, the electron wave front and molecular bond are parallel, and third, the wavefront and the bond axis are perpendicular. It will be seen to what extent orientational averaging weakens features of the cross section and spin polarization. The calculations show that cross section and spin polarization measurements are a possible tool for determining the degree of molecular orientation. There is no degeneracy between I-C and C-I in cross section and spin polarization measurements. The results presented here for 200 eV and 600 eV electrons scattered by CH 3 I should be considered as a case study and it should be possible to find molecules and electron energies for which even more dramatic differences between the various orientations between the molecules and the electrons can be expected. (orig.)

Our Galactic Neighbor Hosts Complex Organic Molecules

Science.gov (United States)

Hensley, Kerry

2018-03-01

For the first time, data from the Atacama Large Millimeter/submillimeter Array (ALMA) reveal the presence of methyl formate and dimethyl ether in a star-forming region outside our galaxy. This discovery has important implications for the formation and survival of complex organic compounds importantfor the formation of life in low-metallicity galaxies bothyoung and old.No Simple Picture of Complex Molecule FormationALMA, pictured here with the Magellanic Clouds above, has observed organic molecules in our Milky Way Galaxy and beyond. [ESO/C. Malin]Complex organic molecules (those with at least six atoms, one or more of which must be carbon) are the precursors to the building blocks of life. Knowing how and where complex organic molecules can form is a key part of understanding how life came to be on Earth and how it might arise elsewhere in the universe. From exoplanet atmospheres to interstellar space, complex organic molecules are ubiquitous in the Milky Way.In our galaxy, complex organic molecules are often found in the intense environments of hot cores clumps of dense molecular gas surrounding the sites of star formation. However, its not yet fully understood how the complex organic molecules found in hot cores come to be. One possibility is that the compounds condense onto cold dust grains long before the young stars begin heating their natal shrouds. Alternatively, they might assemble themselves from the hot, dense gas surrounding the blazing protostars.Composite infrared and optical image of the N 113 star-forming region in the LMC. The ALMA coverage is indicated by the gray line. Click to enlarge. [Sewio et al. 2018]Detecting Complexity, a Galaxy AwayUsing ALMA, a team of researchers led by Marta Sewio (NASA Goddard Space Flight Center) recently detected two complex organic molecules methyl formate and dimethyl ether for the first time in our neighboring galaxy, the Large Magellanic Cloud (LMC). Previous searches for organic molecules in the LMC detected

Organic small molecule semiconducting chromophores for use in organic electronic devices

Energy Technology Data Exchange (ETDEWEB)

Welch, Gregory C.; Hoven, Corey V.; Nguyen, Thuc-Quyen

2018-02-13

Small organic molecule semi-conducting chromophores containing a pyridalthiadiazole, pyridaloxadiazole, or pyridaltriazole core structure are disclosed. Such compounds can be used in organic heterojunction devices, such as organic small molecule solar cells and transistors.

Permanent and induced dipole requirements in ab initio calculations of electron affinities of polar molecules

International Nuclear Information System (INIS)

Garrett, W.R.

1979-01-01

Through the use of a molecular pseudopotential method, we determine the a approximate magnitudes of errors that result when electron affinity determinations of polar negative ions are made through ab initio calculations in which the use of a given basis set yields inappropriate values for permanent and induced dipole moments of the neutral molecule. These results should prove useful in assessing the adequacy of basis sets in ab initio calculations of molecular electron affinities for simple linear polar molecules

Interface properties of organic molecules on metal surfaces; Grenzflaecheneigenschaften organischer Molekuele auf Metalloberflaechen

Energy Technology Data Exchange (ETDEWEB)

Karacuban, Hatice

2010-01-28

In this work, the growth of the archetype molecules CuPc and PTCDA was investigated on Cu(111). PTCDA was also studied on NaCl/Cu(111). The main experiments were carried out with a scanning tunneling microscope. Structural analysis of CuPc on Cu (111) is only possible at low temperatures, since at room temperature the molecules exhibit a high surface mobility. For the investigation of these structures and especially to enable scanning tunneling spectroscopy, a low-temperature scanning tunneling microscope was developed. Using this home built STM the experiments could be carried out at about 10 K. After the adsorption of CuPc on Cu (111) a substrate-induced symmetry reduction of the molecules can be observed in scanning tunneling microscopy. When the occupied states of the molecules are imaged, a switching between two distinct levels is found. These modifications are determined by the adsorption geometry of the molecules. Based on high resolution STM data, an on-top adsorption geometry of the CuPc-molecules on Cu (111)-substrate can be deducted. At low temperatures, two new superstructures of PTCDA on Cu(111) are observed. The molecules within these superstructures are tilted with respect to the substrate. Intermolecular interactions may be the crucial factor for the realignment of the molecules. If PTCDA molecules are adsorbed on a NaCl/Cu (111) substrate, at room temperature, also two new superstructures on the copper substrate were found. They indicate the formation of a metall-organic-complex. On top of the NaCl layer the molecules exclusively grow at polar NaCl step edges. This is an indication for electrostatic interaction between the PTCDA molecules and the NaCl layer. When the molecule density is further increased, a Vollmer-Weber growth sets in. If both molecules PTCDA and CuPc are present on the sample at the same time, local spectroscopy provides information on the metal-organic interface in direct comparison. The STS-results of CuPc/PTCDA on Cu (111

Complex organic molecules in organic-poor massive young stellar objects

DEFF Research Database (Denmark)

Fayolle, Edith C.; Öberg, Karin I.; Garrod, Robin T.

2015-01-01

to search for complex organic molecules over 8-16 GHz in the 1 mm atmospheric window toward three MYSOs with known ice abundances, but without luminous molecular hot cores. Results. Complex molecules are detected toward all three sources at comparable abundances with respect to CH3OH to classical hot core......Context. Massive young stellar objects (MYSOs) with hot cores are classic sources of complex organic molecules. The origins of these molecules in such sources, as well as the small-and large-scale differentiation between nitrogen-and oxygen-bearing complex species, are poorly understood. Aims. We...... aim to use complex molecule abundances toward a chemically less explored class of MYSOs with weak hot organic emission lines to constrain the impact of hot molecular cores and initial ice conditions on the chemical composition toward MYSOs. Methods. We use the IRAM 30 m and the Submillimeter Array...

Oriented Polar Molecules in a Solid Inert-Gas Matrix: A Proposed Method for Measuring the Electric Dipole Moment of the Electron

Directory of Open Access Journals (Sweden)

A. C. Vutha

2018-01-01

Full Text Available We propose a very sensitive method for measuring the electric dipole moment of the electron using polar molecules embedded in a cryogenic solid matrix of inert-gas atoms. The polar molecules can be oriented in the z ^ -direction by an applied electric field, as has recently been demonstrated by Park et al. The trapped molecules are prepared into a state that has its electron spin perpendicular to z ^ , and a magnetic field along z ^ causes precession of this spin. An electron electric dipole moment d e would affect this precession due to the up to 100 GV/cm effective electric field produced by the polar molecule. The large number of polar molecules that can be embedded in a matrix, along with the expected long coherence times for the precession, allows for the possibility of measuring d e to an accuracy that surpasses current measurements by many orders of magnitude. Because the matrix can inhibit molecular rotations and lock the orientation of the polar molecules, it may not be necessary to have an electric field present during the precession. The proposed technique can be applied using a variety of polar molecules and inert gases, which, along with other experimental variables, should allow for careful study of systematic uncertainties in the measurement.

Thermodynamic characteristics of the adsorption of organic molecules on modified MCM-41 adsorbents

Science.gov (United States)

Gus'kov, V. Yu.; Sukhareva, D. A.; Salikhova, G. R.; Karpov, S. I.; Kudasheva, F. Kh.; Roessner, F.; Borodina, E. V.

2017-07-01

The adsorption of a number of organic molecules on samples of MCM-41 adsorbent modified with dichloromethylphenylsilane and subsequently treated with sulfuric acid (MDCS) and N-trimethoxysilylpropyl- N, N, N-trimethylammonium chloride (MNM) is studied. Specific retention volumes equal to the Henry constant are determined by means of inverse gas chromatography at infinite dilution. The thermodynamic characteristics of adsorption, the dispersive and specific components of the Helmholtz energy of adsorption, and the increment of the methyl group to the heat of adsorption are calculated. It is shown that the grafting of aminosilane and phenylsilane groups enhances the forces of dispersion and reduces specific interactions. A greater drop in polarity is observed for MDCS than for MNM, due to the stronger polarity of amoinosilane; the enthalpy factor makes the main contribution to the adsorption of organic compounds on the investigated adsorbents. It is found that the MNM sample is capable of the irreversible adsorption of alcohols.

Influence of intrinsic decoherence on tripartite entanglement and bipartite fidelity of polar molecules in pendular states

Energy Technology Data Exchange (ETDEWEB)

Han, Jia-Xing; Hu, Yuan; Jin, Yu [Key Laboratory of Micro-Nano Measurement-Manipulation and Physics (Ministry of Education), School of Physics and Nuclear Energy Engineering, Beihang University, Xueyuan Road No. 37, Beijing 100191 (China); Zhang, Guo-Feng, E-mail: gf1978zhang@buaa.edu.cn [Key Laboratory of Micro-Nano Measurement-Manipulation and Physics (Ministry of Education), School of Physics and Nuclear Energy Engineering, Beihang University, Xueyuan Road No. 37, Beijing 100191 (China); State Key Laboratory of Software Development Environment, Beihang University, Xueyuan Road No. 37, Beijing 100191 (China); State Key Laboratory of Low-Dimensional Quantum Physics, Tsinghua University, Beijing 100084 (China); Key Laboratory of Quantum Information, University of Science and Technology of China, Chinese Academy of Sciences, Hefei 230026 (China)

2016-04-07

An array of ultracold polar molecules trapped in an external electric field is regarded as a promising carrier of quantum information. Under the action of this field, molecules are compelled to undergo pendular oscillations by the Stark effect. Particular attention has been paid to the influence of intrinsic decoherence on the model of linear polar molecular pendular states, thereby we evaluate the tripartite entanglement with negativity, as well as fidelity of bipartite quantum systems for input and output signals using electric dipole moments of polar molecules as qubits. According to this study, we consider three typical initial states for both systems, respectively, and investigate the temporal evolution with variable values of the external field intensity, the intrinsic decoherence factor, and the dipole-dipole interaction. Thus, we demonstrate the sound selection of these three main parameters to obtain the best entanglement degree and fidelity.

Oriented Polar Molecules in a Solid Inert-Gas Matrix: A Proposed Method for Measuring the Electric Dipole Moment of the Electron

Science.gov (United States)

Vutha, A.; Horbatsch, M.; Hessels, E.

2018-01-01

We propose a very sensitive method for measuring the electric dipole moment of the electron using polar molecules embedded in a cryogenic solid matrix of inert-gas atoms. The polar molecules can be oriented in the $\\hat{\\rm{z}}$ direction by an applied electric field, as has recently been demonstrated by Park, et al. [Angewandte Chemie {\\bf 129}, 1066 (2017)]. The trapped molecules are prepared into a state which has its electron spin perpendicular to $\\hat{\\rm{z}}$, and a magnetic field along $\\hat{\\rm{z}}$ causes precession of this spin. An electron electric dipole moment $d_e$ would affect this precession due to the up to 100~GV/cm effective electric field produced by the polar molecule. The large number of polar molecules that can be embedded in a matrix, along with the expected long coherence times for the precession, allows for the possibility of measuring $d_e$ to an accuracy that surpasses current measurements by many orders of magnitude. Because the matrix can inhibit molecular rotations and lock the orientation of the polar molecules, it may not be necessary to have an electric field present during the precession. The proposed technique can be applied using a variety of polar molecules and inert gases, which, along with other experimental variables, should allow for careful study of systematic uncertainties in the measurement.

Effects of Perchlorate on Organic Molecules under Simulated Mars Conditions

Science.gov (United States)

Carrier, B. L.; Kounaves, S. P.

2014-12-01

Perchlorate (ClO4-) was discovered in the northern polar region of Mars by the Mars Phoenix Lander in 2008 and has also been recently detected by the Curiosity Rover in Gale Crater [1,2]. Perchlorate has also been shown to be formed under current Mars conditions via the oxidation of mineral chlorides, further supporting the theory that perchlorate is present globally on Mars [3]. The discovery of perchlorate on Mars has raised important questions about the effects of perchlorate on the survival and detection of organic molecules. Although it has been shown that pyrolysis in the presence of perchlorate results in the alteration or destruction of organic molecules [4], few studies have been conducted on the potential effects of perchlorate on organic molecules under martian surface conditions. Although perchlorate is typically inert under Mars-typical temperatures [5], perchlorate does absorb high energy UV radiation, and has been shown to decompose to form reactive oxychlorine species such as chlorite (ClO2-) when exposed to martian conditions including UV or ionizing radiation [6,7]. Here we investigate the effects of perchlorate on the organic molecules tryptophan, benzoic acid and mellitic acid in order to determine how perchlorate may alter these compounds under Mars conditions. Experiments are performed in a Mars Simulation Chamber (MSC) capable of reproducing the temperature, pressure, atmospheric composition and UV flux found on Mars. Soil simulants are prepared consisting of SiO2 and each organic, as well as varying concentrations of perchlorate salts, and exposed in the MSC. Subsequent to exposure in the MSC samples are leached and the leachate analyzed by HPLC and LC-MS to determine the degree of degradation of the original organic and the identity of any potential decomposition products formed by oxidation or chlorination. References: [1] Kounaves et al., J. Geophys. Res. Planets, Vol. 115, p. E00E10, 2010 [2] Glavin et al., J. Geophys. Res. Planets, Vol

A molecular beam machine for the measurement of the scattering of polar diatomic molecules

International Nuclear Information System (INIS)

Everdij, J.J.

1976-01-01

This thesis describes an experimental method to determine the long range, angular dependent part of the intermolecular potential between a polar diatomic molecule and a spherical symmetric partner. The method contains the study of the scattering behaviour of the molecules in a crossed beam experiment. The primary beam consisting of polar diatomic molecules at thermal velocities (approximately 0.1 eV), is selected in a specified rotational state by means of an electrostatic, inhomogeneous field before the scattering center, where it crosses the (supersonic) secondary beam under an angle of 90 0 . By means of a second state selector, followed by a velocity selector and a particle detector, the consequences are studied of the scattering process on the primary beam, i.e. the behaviour of the total and differential elastic cross sections plus the transition probability of a collision induced transition to another rotational state. (Auth.)

Polarization measurement for internal polarized gaseous targets

International Nuclear Information System (INIS)

Ye Zhenyu; Ye Yunxiu; Lv Haijiang; Mao Yajun

2004-01-01

The authors present an introduction to internal polarized gaseous targets, polarization method, polarization measurement method and procedure. To get the total nuclear polarization of hydrogen atoms (including the polarization of the recombined hydrogen molecules) in the target cell, authors have measured the parameters relating to atomic polarization and polarized hydrogen atoms and molecules. The total polarization of the target during our measurement is P T =0.853 ± 0.036. (authors)

Impact of Molecular Orientation and Packing Density on Electronic Polarization in the Bulk and at Surfaces of Organic Semiconductors

KAUST Repository

Ryno, Sean

2016-05-16

The polarizable environment surrounding charge carriers in organic semiconductors impacts the efficiency of the charge transport process. Here, we consider two representative organic semiconductors, tetracene and rubrene, and evaluate their polarization energies in the bulk and at the organic-vacuum interface using a polarizable force field that accounts for induced-dipole and quadrupole interactions. Though both oligoacenes pack in a herringbone motif, the tetraphenyl substituents on the tetracene backbone of rubrene alter greatly the nature of the packing. The resulting change in relative orientations of neighboring molecules is found to reduce the bulk polarization energy of holes in rubrene by some 0.3 eV when compared to tetracene. The consideration of model organic-vacuum interfaces highlights the significant variation in the electrostatic environment for a charge carrier at a surface although the net change in polarization energy is small; interestingly, the environment of a charge even just one layer removed from the surface can be viewed already as representative of the bulk. Overall, it is found that in these herringbone-type layered crystals the polarization energy has a much stronger dependence on the intralayer packing density than interlayer packing density.

The electron-spin--nuclear-spin interaction studied by polarized neutron scattering.

Science.gov (United States)

Stuhrmann, Heinrich B

2007-11-01

Dynamic nuclear spin polarization (DNP) is mediated by the dipolar interaction of paramagnetic centres with nuclear spins. This process is most likely to occur near paramagnetic centres at an angle close to 45 degrees with respect to the direction of the external magnetic field. The resulting distribution of polarized nuclear spins leads to an anisotropy of the polarized neutron scattering pattern, even with randomly oriented radical molecules. The corresponding cross section of polarized coherent neutron scattering in terms of a multipole expansion is derived for radical molecules in solution. An application using data of time-resolved polarized neutron scattering from an organic chromium(V) molecule is tested.

Molecular simulation of polar molecules interaction with MOFs family materials

International Nuclear Information System (INIS)

De Toni, M.

2012-01-01

The topic of this thesis is the adsorption of simple molecular fluids in nano-porous materials. Many industrial processes are based on this phenomenon, including ionic exchange, selective separation and heterogeneous catalysis. I used molecular simulation to study the adsorption properties of polar molecules of industrial interest (CO 2 and H 2 O) in a new class of crystalline microporous hybrid organic-inorganic materials called Metal-Organic Frameworks (MOFs). They have exceptional adsorption properties due to their topological variety and their versatility, allowed by the large range of possibilities offered by organic and coordination chemistry and functionalizations. I first studied the adsorption of CO 2 in a family of materials called IRMOFs, which share the same topology but have different porous volume, in order to characterize the effect of confinement on their adsorption performance. In particular, a general behavior has been highlighted: the critical temperature decreases when the confinement increases. Then, I looked at a recently synthesized cationic MOF called Zn2(CBTACN). After having localized the extra-framework halogen anions in the unit cell of the material, something which was not possible experimentally, I characterized CO 2 adsorption in this system first as a pure gas and then as a component of different mixtures. Finally, I was interested in the hydrothermal stability of MOFs, a crucial issue for their use in industrial applications. I observed the hydration mechanism of system that is analogous to the MOF-5 (IRMOF-0h) and shed light on some collaborative effects of the attack of water that were unknown to in the literature. (author)

Spectral simulations of polar diatomic molecules immersed in He clusters: application to the ICl (X) molecule

International Nuclear Information System (INIS)

Villarreal, P; Lara-Castells, M P de; Prosmiti, R; Delgado-Barrio, G; Lopez-Duran, D; Gianturco, F A; Jellinek, J

2007-01-01

A recently developed quantum-chemistry-like methodology to study molecules solvated in atomic clusters is applied to the ICl (iodine chloride) polar diatomic molecule immersed in clusters of He atoms. The atoms of the solvent clusters are treated as the 'electrons' and the solvated molecule as a structured 'nucleus' of the combined solvent-solute system. The helium-helium and helium-dopant interactions are represented by parametrized two-body and ab initio three-body potentials, respectively. The ground-state wavefunctions are used to compute the infrared (IR) spectra of the solvated molecule. In agreement with the experimental observations, the computed spectra exhibit considerable differences depending on whether the solvent cluster is comprised of bosonic ( 4 He) or fermionic ( 3 He) atoms. The source of these differences is attributed to the different spin-statistics of the solvent clusters. The bosonic versus fermionic nature of the solvent is reflected in the IR absorption selection rules. Only P and R branches with single state transitions appear in the spectrum when the molecule is solvated in a bosonic cluster. On the other hand, when the solvent represents a fermionic environment, quasi-degenerate multiplets of spin states contribute to each branch and, in addition, the Q-branch becomes also allowed. Combined, these two factors explain the more congested nature of the spectrum in the fermionic case

Organic- and molecule-based magnets

Indian Academy of Sciences (India)

The discovery of organic- and molecule-based magnets has led to design and synthesis of several families with magnetic ordering temperatures as high as ∼ 125° C. Examples of soft and hard magnets with coercivities as high as 27 kOe have also been reported. Examples from our laboratory of organic-based magnets ...

Organic Molecules in Meteorites

Science.gov (United States)

Martins, Zita

2015-08-01

Carbonaceous meteorites are primitive samples from the asteroid belt, containing 3-5wt% organic carbon. The exogenous delivery of organic matter by carbonaceous meteorites may have contributed to the organic inventory of the early Earth. The majority (>70%) of the meteoritic organic material consist of insoluble organic matter (IOM) [1]. The remaining meteoritic organic material (meteorites contain soluble organic molecules with different abundances and distributions, which may reflect the extension of aqueous alteration or thermal metamorphism on the meteorite parent bodies. Extensive aqueous alteration on the meteorite parent body may result on 1) the decomposition of α-amino acids [5, 6]; 2) synthesis of β- and γ-amino acids [2, 6-9]; 3) higher relative abundances of alkylated polycyclic aromatic hydrocarbons (PAHs) [6, 10]; and 4) higher L-enantiomer excess (Lee) value of isovaline [6, 11, 12].The soluble organic content of carbonaceous meteorites may also have a contribution from Fischer-Tropsch/Haber-Bosch type gas-grain reactions after the meteorite parent body cooled to lower temperatures [13, 14].The analysis of the abundances and distribution of the organic molecules present in meteorites helps to determine the physical and chemical conditions of the early solar system, and the prebiotic organic compounds available on the early Earth.[1] Cody and Alexander (2005) GCA 69, 1085. [2] Cronin and Chang (1993) in: The Chemistry of Life’s Origin. pp. 209-258. [3] Martins and Sephton (2009) in: Amino acids, peptides and proteins in organic chemistry. pp. 1-42. [4] Martins (2011) Elements 7, 35. [5] Botta et al. (2007) MAPS 42, 81. [6] Martins et al. (2015) MAPS, in press. [7] Cooper and Cronin (1995) GCA 59, 1003. [8] Glavin et al. (2006) MAPS. 41, 889. [9] Glavin et al. (2011) MAPS 45, 1948. [10] Elsila et al. (2005) GCA 5, 1349. [11] Glavin and Dworkin (2009) PNAS 106, 5487. [12] Pizzarello et al. (2003) GCA 67, 1589. [13] Chan et al. (2012) MAPS. 47, 1502

Implementation of quantum logic gates using polar molecules in pendular states.

Science.gov (United States)

Zhu, Jing; Kais, Sabre; Wei, Qi; Herschbach, Dudley; Friedrich, Bretislav

2013-01-14

We present a systematic approach to implementation of basic quantum logic gates operating on polar molecules in pendular states as qubits for a quantum computer. A static electric field prevents quenching of the dipole moments by rotation, thereby creating the pendular states; also, the field gradient enables distinguishing among qubit sites. Multi-target optimal control theory is used as a means of optimizing the initial-to-target transition probability via a laser field. We give detailed calculations for the SrO molecule, a favorite candidate for proposed quantum computers. Our simulation results indicate that NOT, Hadamard and CNOT gates can be realized with high fidelity, as high as 0.985, for such pendular qubit states.

Mapping the local organization of cell membranes using excitation-polarization-resolved confocal fluorescence microscopy.

Science.gov (United States)

Kress, Alla; Wang, Xiao; Ranchon, Hubert; Savatier, Julien; Rigneault, Hervé; Ferrand, Patrick; Brasselet, Sophie

2013-07-02

Fluorescence anisotropy and linear dichroism imaging have been widely used for imaging biomolecular orientational distributions in protein aggregates, fibrillar structures of cells, and cell membranes. However, these techniques do not give access to complete orientational order information in a whole image, because their use is limited to parts of the sample where the average orientation of molecules is known a priori. Fluorescence anisotropy is also highly sensitive to depolarization mechanisms such as those induced by fluorescence energy transfer. A fully excitation-polarization-resolved fluorescence microscopy imaging that relies on the use of a tunable incident polarization and a nonpolarized detection is able to circumvent these limitations. We have developed such a technique in confocal epifluorescence microscopy, giving access to new regions of study in the complex and heterogeneous molecular organization of cell membranes. Using this technique, we demonstrate morphological changes at the subdiffraction scale in labeled COS-7 cell membranes whose cytoskeleton is perturbed. Molecular orientational order is also seen to be affected by cholesterol depletion, reflecting the strong interplay between lipid-packing regions and their nearby cytoskeleton. This noninvasive optical technique can reveal local organization in cell membranes when used as a complement to existing methods such as generalized polarization. Copyright © 2013 Biophysical Society. Published by Elsevier Inc. All rights reserved.

Toxicology of organic-inorganic hybrid molecules: bio-organometallics and its toxicology.

Science.gov (United States)

Fujie, Tomoya; Hara, Takato; Kaji, Toshiyuki

2016-01-01

Bio-organometallics is a research strategy of biology that uses organic-inorganic hybrid molecules. The molecules are expected to exhibit useful bioactivities based on the unique structure formed by interaction between the organic structure and intramolecular metal(s). However, studies on both biology and toxicology of organic-inorganic hybrid molecules have been incompletely performed. There can be two types of toxicological studies of bio-organometallics; one is evaluation of organic-inorganic hybrid molecules and the other is analysis of biological systems from the viewpoint of toxicology using organic-inorganic hybrid molecules. Our recent studies indicate that cytotoxicity of hybrid molecules containing a metal that is nontoxic in inorganic forms can be more toxic than that of hybrid molecules containing a metal that is toxic in inorganic forms when the structure of the ligand is the same. Additionally, it was revealed that organic-inorganic hybrid molecules are useful for analysis of biological systems important for understanding the toxicity of chemical compounds including heavy metals.

Polarization Nonlinear Optics of Quadratically Nonlinear Azopolymers

International Nuclear Information System (INIS)

Konorov, S.O.; Akimov, D.A.; Ivanov, A.A.; Petrov, A.N.; Alfimov, M.V.; Yakimanskii, A.V.; Smirnov, N.N.; Ivanova, V.N.; Kudryavtsev, V.V.; Podshivalov, A.A.; Sokolova, I.M.; Zheltikov, A.M.

2005-01-01

The polarization properties of second harmonic and sum-frequency signals generated by femtosecond laser pulses in films of polymers containing covalent groups of an azobenzothiazole chromophore polarized by an external electric field are investigated. It is shown that the methods of polarization nonlinear optics make it possible to determine the structure of oriented molecular dipoles and reveal important properties of the motion of collectivized πelectrons in organic molecules with strong optical nonlinearities. The polarization measurements show that the tensor of quadratic nonlinear optical susceptibility of chromophore fragments oriented by an external field in macromolecules of the noted azopolymers has a degenerate form. This is indicative of a predominantly one-dimensional character of motion of collectivized π electrons along an extended group of atoms in such molecules

Electric moments in molecule interferometry

International Nuclear Information System (INIS)

Eibenberger, Sandra; Gerlich, Stefan; Arndt, Markus; Tuexen, Jens; Mayor, Marcel

2011-01-01

We investigate the influence of different electric moments on the shift and dephasing of molecules in a matter wave interferometer. Firstly, we provide a quantitative comparison of two molecules that are non-polar yet polarizable in their thermal ground state and that differ in their stiffness and response to thermal excitations. While C 25 H 20 is rather rigid, its larger derivative C 49 H 16 F 52 is additionally equipped with floppy side chains and vibrationally activated dipole moment variations. Secondly, we elucidate the role of a permanent electric dipole momentby contrasting the quantum interference pattern of a (nearly) non-polar and a polar porphyrin derivative. We find that a high molecular polarizability and even sizeable dipole moment fluctuations are still well compatible with high-contrast quantum interference fringes. The presence of permanent electric dipole moments, however, can lead to a dephasing and rapid degradation of the quantum fringe pattern already at moderate electric fields. This finding is of high relevance for coherence experiments with large organic molecules, which are generally equipped with strong electric moments.

Electronic structures of spinterface for thiophene molecule adsorbed at Co, Fe, and Ni electrode: First principles calculations

Energy Technology Data Exchange (ETDEWEB)

Cai, Linlin; Tian, Yanli; Yuan, Xiaobo; Hu, Guichao; Ren, Junfeng, E-mail: renjf@sdnu.edu.cn

2016-12-15

Highlights: • Thiophene molecule could be spin polarized when adsorbed at Co(001), Fe(100), and Ni(111) surfaces. • The biggest spin polarization will be obtained when the thiophene molecule adsorbed at the Fe(100) surface. • The spin polarization is originated from the interfacial orbital hybridizations between the 3d orbital of ferromagnetic electrodes and the 2p orbital of the thiophene molecule. - Abstract: First principles calculations are adopted to study the spin polarization properties of thiophene molecule which adsorbed at the Co, Fe, and Ni electrode surfaces. The density of states, spin-polarized density distributions as well as the differential charge density distributions are obtained. It is found that the p orbital of the thiophene molecule will interact with the d orbital of the ferromagnetic electrodes, which will generate new spin coupling states and lead to obvious spin polarization in the thiophene molecule. Different electrodes induce different spin polarization properties, and in which the Fe electrode will bring the biggest spin polarization of the thiophene molecule. People can selectively and efficiently inject spin polarized electrons into molecules by choosing suitable ferromagnetic electrodes in organic spintronic devices.

Spin-polarized light-emitting diodes based on organic bipolar spin valves

Science.gov (United States)

Vardeny, Zeev Valentine; Nguyen, Tho Duc; Ehrenfreund, Eitan Avraham

2017-10-25

Spin-polarized organic light-emitting diodes are provided. Such spin-polarized organic light-emitting diodes incorporate ferromagnetic electrodes and show considerable spin-valve magneto-electroluminescence and magneto-conductivity responses, with voltage and temperature dependencies that originate from the bipolar spin-polarized space charge limited current.

Polarization-Independent Electrically Tunable Holographic Polymer Dispersed Liquid Crystals Grating Doped with Chiral Molecules

Directory of Open Access Journals (Sweden)

Hui LI

2017-08-01

Full Text Available This study proposes a holographic grating made of polymer dispersed liquid crystal (PDLC, with a small amount of chiral molecules doped into PDLC material. The major advantage of this grating is that it is independent of light polarization. This characteristic was verified by applying the interference beam intensity of a He-Cd laser at 150 mW/cm2, with an incidence angle between the two interference beams of 24°, for an irradiation curing duration of 120 s. The observed periodic structure of the grating is consistent with the theoretical value. As chiral molecules are doped, nematic-LC experiences a phase-change in the grating. However, the electro-optical features are only slightly affected. This proposed grating has greatly potential in 3D imaging because of its polarization-independent feature.DOI: http://dx.doi.org/10.5755/j01.ms.23.2.16312

Enantiomeric separation of complex organic molecules produced from irradiation of interstellar/circumstellar ice analogs

Science.gov (United States)

Nuevo, M.; Meierhenrich, U. J.; D'Hendecourt, L.; Muñoz Caro, G. M.; Dartois, E.; Deboffle, D.; Thiemann, W. H.-P.; Bredehöft, J.-H.; Nahon, L.

Irradiation of interstellar/circumstellar ice analogs by ultraviolet (UV) light followed by warm up in the laboratory leads to the formation of complex organic molecules, stable at room temperature. Hydrolysis of the room temperature residue releases amino acids, the building blocks of proteins. These amino acids exist in two different forms (L and D), but proteins encountered in living beings consist exclusively of L enantiomers. The origin of this property, called homochirality, is still unknown. Amino acids can be detected and quantified by chemical techniques such as chiral gas chromatography coupled with mass spectrometry (GC-MS). Enantiomers of chiral organics are also known to interact selectively with circularly polarized light (CPL), leading to a selective production or destruction of the final compounds. This paper describes how we settled an experiment where amino acids are formed by irradiation of interstellar/circumstellar ice analogs with ultraviolet (UV) CPL, produced by a synchrotron radiation beamline, which allowed us to quantify the effect of such polarized light on the production of amino acids. These results can be compared to the enantiomeric excesses measured in primitive meteorites such as Murchison.

Thermodynamics of organic molecule adsorption on sorbents modified with 5-hydroxy-6-methyluracil by inverse gas chromatography.

Science.gov (United States)

Gus'kov, Vladimir Yu; Gainullina, Yulia Yu; Ivanov, Sergey P; Kudasheva, Florida Kh

2014-08-22

The thermodynamic features of organic molecule adsorption from the gaseous phase of sorbents modified with 5-hydroxy-6-methyluracil (HMU) were studied. Molar internal energy and entropy of adsorption variation analyses showed that with every type surface, except for silica gel, layers of supramolecular structure have cavities equal in size with the ones revealed in HMU crystals by X-ray diffraction. Adsorption thermodynamics on HMU-modified sorbents depended on the amount of impregnated HMU and on the polarity, but not the porosity, of the initial sorbent. Polarity of the modified surface increased as a function of HMU quantity and initial sorbent mean pore size, but become appreciably lower if the initial surface is capable of hydrogen bonding. Copyright © 2014 Elsevier B.V. All rights reserved.

Spin-polarized transport through single-molecule magnet Mn6 complexes

KAUST Repository

Cremades, Eduard; Pemmaraju, C. D.; Sanvito, Stefano; Ruiz, Eliseo

2013-01-01

The coherent transport properties of a device, constructed by sandwiching a Mn6 single-molecule magnet between two gold surfaces, are studied theoretically by using the non-equilibrium Green's function approach combined with density functional theory. Two spin states of such Mn6 complexes are explored, namely the ferromagnetically coupled configuration of the six MnIII cations, leading to the S = 12 ground state, and the low S = 4 spin state. For voltages up to 1 volt the S = 12 ground state shows a current one order of magnitude larger than that of the S = 4 state. Furthermore this is almost completely spin-polarized, since the Mn6 frontier molecular orbitals for S = 12 belong to the same spin manifold. As such the high-anisotropy Mn6 molecule appears as a promising candidate for implementing, at the single molecular level, both spin-switches and low-temperature spin-valves. © 2013 The Royal Society of Chemistry.

Spin-polarized transport through single-molecule magnet Mn6 complexes

KAUST Repository

Cremades, Eduard

2013-01-01

The coherent transport properties of a device, constructed by sandwiching a Mn6 single-molecule magnet between two gold surfaces, are studied theoretically by using the non-equilibrium Green\\'s function approach combined with density functional theory. Two spin states of such Mn6 complexes are explored, namely the ferromagnetically coupled configuration of the six MnIII cations, leading to the S = 12 ground state, and the low S = 4 spin state. For voltages up to 1 volt the S = 12 ground state shows a current one order of magnitude larger than that of the S = 4 state. Furthermore this is almost completely spin-polarized, since the Mn6 frontier molecular orbitals for S = 12 belong to the same spin manifold. As such the high-anisotropy Mn6 molecule appears as a promising candidate for implementing, at the single molecular level, both spin-switches and low-temperature spin-valves. © 2013 The Royal Society of Chemistry.

Fascinating Organic Molecules from Nature

Indian Academy of Sciences (India)

Home; Journals; Resonance – Journal of Science Education; Volume 18; Issue 5. Fascinating Organic Molecules from Nature - Using a Natural ... Road Banashankari 2nd Stage Bangalore 560 070, India. Department of Chemistry Sri Sathya Sai Institute of Higher Learning Brindavan Campus Bangalore 560 067, India.

Fascinating Organic Molecules from Nature

Indian Academy of Sciences (India)

Home; Journals; Resonance – Journal of Science Education; Volume 18; Issue 7. Fascinating Organic Molecules from Nature - Sweet Stimulants of ... Road Banashankari 2nd Stage Bangalore 560 070, India. Department of Chemistry Sri Sathya Sai Institute of Higher Learning Brindavan Campus Bangalore 560 067, India.

Solvation study of the non-specific lipid transfer protein from wheat by intermolecular NOEs with water and small organic molecules

International Nuclear Information System (INIS)

Liepinsh, Edvards; Sodano, Patrick; Tassin, Severine; Marion, Didier; Vovelle, Francoise; Otting, Gottfried

1999-01-01

Intermolecular nuclear Overhauser effects (NOEs) were measured between the protons of various small solvent or gas molecules and the non-specific lipid transfer protein (ns-LTP) from wheat. Intermolecular NOEs were observed with the hydrophobic pocket in the interior of wheat ns-LTP, which grew in intensity in the order cyclopropane (saturated solution) < methane (140 bar) < ethane (40 bar) < acetonitrile (5% in water) < cyclohexane (saturated solution) < benzene (saturated solution). No intermolecular NOEs were observed with dioxane (5% in water). The intermolecular NOEs were negative for all of the organic molecules tested. Intermolecular NOEs between wheat ns-LTP and water were weak or could not be distinguished from exchange-relayed NOEs. As illustrated by the NOEs with cyclohexane versus dioxane, the hydrophobic pocket in wheat ns-LTP preferably binds non-polar molecules. Yet, polar molecules like acetonitrile can also be accommodated. The pressure dependence of the NOEs between methane and wheat ns-LTP indicated incomplete occupancy, even at 190 bar methane pressure. In general, NOE intensities increased with the size of the ligand molecule and its vapor pressure. NMR of the vapor phase showed excellent resolution between the signals from the gas phase and those from the liquid phase. The vapor concentration of cyclohexane was fivefold higher than that of the dioxane solution, supporting the binding of cyclohexane versus uptake of dioxane

Polarization effects on the electric properties of urea and thiourea molecules in solid phase

International Nuclear Information System (INIS)

Santos, O. L.; Fonseca, T. L.; Sabino, J. R.; Georg, H. C.; Castro, M. A.

2015-01-01

We present theoretical results for the dipole moment, linear polarizability, and first hyperpolarizability of the urea and thiourea molecules in solid phase. The in-crystal electric properties were determined by applying a supermolecule approach in combination with an iterative electrostatic scheme, in which the surrounding molecules are represented by point charges. It is found for both urea and thiourea molecules that the influence of the polarization effects is mild for the linear polarizability, but it is marked for the dipole moment and first hyperpolarizability. The replacement of oxygen atoms by sulfur atoms increases, in general, the electric responses. Our second-order Møller–Plesset perturbation theory based iterative scheme predicts for the in-crystal dipole moment of urea and thiourea the values of 7.54 and 9.19 D which are, respectively, increased by 61% and 58%, in comparison with the corresponding isolated values. The result for urea is in agreement with the available experimental result of 6.56 D. In addition, we present an estimate of macroscopic quantities considering explicit unit cells of urea and thiourea crystals including environment polarization effects. These supermolecule calculations take into account partially the exchange and dispersion effects. The results illustrate the role played by the electrostatic interactions on the static second-order nonlinear susceptibility of the urea crystal

Organic light emitting diodes with spin polarized electrodes

NARCIS (Netherlands)

Arisi, E.; Bergenti, I.; Dediu, V.; Loi, M.A.; Muccini, M.; Murgia, M.; Ruani, G.; Taliani, C.; Zamboni, R.

2003-01-01

Electrical and optical properties of Alq3 based organic light emitting diodes with normal and spin polarized electrodes are presented. Epitaxial semitransparent highly spin polarized La0.7Sr0.3MnO3 were used as hole injector, substituting the traditional indium tin oxide electrode. A comparison of

Force microscopy on insulators: imaging of organic molecules

International Nuclear Information System (INIS)

Pfeiffer, O; Gnecco, E; Zimmerli, L; Maier, S; Meyer, E; Nony, L; Bennewitz, R; Diederich, F; Fang, H; Bonifazi, D

2005-01-01

So far, most of the high resolution scanning probe microscopy studies of organic molecules were restricted to metallic substrates. Insulating substrates are mandatory when the molecules need to be electrically decoupled in a electronic circuit. In such a case, atomic force microscopy is required. In this paper we will discuss our recent studies on different organic molecules deposited on KBr surfaces in ultra-high vacuum, and then imaged by AFM at room temperature. The distance between tip and surface was controlled either by the frequency-shift of the cantilever resonance or by the excitation signal required to keep the oscillation amplitude constant. Advantages and drawbacks of both techniques are discussed. The high mobility of the molecules, due to their weak interaction with the substrate, hinders the formation of regular self assembled structures. To overcome this problem we created artificial structures on the surface by annealing and by electron irradiation, which made possible the growth of the molecules onto step edges and their confinement into rectangular pits

Effect of organic molecules on hydrolysis of peptide bond: A DFT study

International Nuclear Information System (INIS)

Makshakova, Olga; Ermakova, Elena

2013-01-01

Highlights: ► DFT study of the effects of small organic molecules on the hydrolysis reactions of peptide bonds. ► Organic molecules can activate nonenzymatic hydrolysis reaction. ► Influence of organic acids on activation energy barrier correlates with their electronegativity. - Abstract: The activation and inhibition effects of small organic molecules on peptide hydrolysis have been studied using a model compound dialanine and DFT approach. Solvent-assisted and non-assisted concerted mechanisms were analyzed. Several transition states for the systems: alanine dipeptide–water molecule in complexes with alcohol molecules, acetonitrile, dimethylsulfoxide, propionic, lactic and pyruvic acids and water molecules were localized. The formation of hydrogen bonds between dipeptide, reactive water molecule and molecules of solvents influences the activation energy barrier of the peptide bond hydrolytic reaction. Strong effect of organic acids on the activation energy barrier correlates with their electronegativity. Acetonitrile can act as an inhibitor of reaction. Mechanisms of regulation of the activation energy barrier are discussed in the terms of donor-acceptor interactions

Halopentacenes: Promising Candidates for Organic Semiconductors

International Nuclear Information System (INIS)

Gong-He, Du; Zhao-Yu, Ren; Ji-Ming, Zheng; Ping, Guo

2009-01-01

We introduce polar substituents such as F, Cl, Br into pentacene to enhance the dissolubility in common organic solvents while retaining the high charge-carrier mobilities of pentacene. Geometric structures, dipole moments, frontier molecule orbits, ionization potentials and electron affinities, as well as reorganization energies of those molecules, and of pentacene for comparison, are successively calculated by density functional theory. The results indicate that halopentacenes have rather small reorganization energies (< 0.2 eV), and when the substituents are in position 2 or positions 2 and 9, they are polarity molecules. Thus we conjecture that they can easily be dissolved in common organic solvents, and are promising candidates for organic semiconductors. (condensed matter: electronicstructure, electrical, magnetic, and opticalproperties)

X-ray characterization of solid small molecule organic materials

Science.gov (United States)

Billinge, Simon; Shankland, Kenneth; Shankland, Norman; Florence, Alastair

2014-06-10

The present invention provides, inter alia, methods of characterizing a small molecule organic material, e.g., a drug or a drug product. This method includes subjecting the solid small molecule organic material to x-ray total scattering analysis at a short wavelength, collecting data generated thereby, and mathematically transforming the data to provide a refined set of data.

Organic molecules with abnormal geometric parameters

International Nuclear Information System (INIS)

Komarov, Igor V

2001-01-01

Organic molecules, the structural parameters of which (carbon-carbon bond lengths, bond and torsion angles) differ appreciably from the typical most frequently encountered values, are discussed. Using many examples of 'record-breaking' molecules, the limits of structural distortions in carbon compounds and their unusual chemical properties are demonstrated. Particular attention is devoted to strained compounds not yet synthesised whose properties have been predicted using quantum-chemical calculations. Factors that ensure the stability of such compounds are outlined. The bibliography includes 358 references.

Spin polarized electron tunneling and magnetoresistance in molecular junctions.

Science.gov (United States)

Szulczewski, Greg

2012-01-01

This chapter reviews tunneling of spin-polarized electrons through molecules positioned between ferromagnetic electrodes, which gives rise to tunneling magnetoresistance. Such measurements yield important insight into the factors governing spin-polarized electron injection into organic semiconductors, thereby offering the possibility to manipulate the quantum-mechanical spin degrees of freedom for charge carriers in optical/electrical devices. In the first section of the chapter a brief description of the Jullière model of spin-dependent electron tunneling is reviewed. Next, a brief description of device fabrication and characterization is presented. The bulk of the review highlights experimental studies on spin-polarized electron tunneling and magnetoresistance in molecular junctions. In addition, some experiments describing spin-polarized scanning tunneling microscopy/spectroscopy on single molecules are mentioned. Finally, some general conclusions and prospectus on the impact of spin-polarized tunneling in molecular junctions are offered.

Optically stimulated slowing of polar heavy-atom molecules with a constant beat phase

Science.gov (United States)

Yin, Yanning; Xu, Supeng; Xia, Meng; Xia, Yong; Yin, Jianping

2018-04-01

Polar heavy-atom molecules have been well recognized as promising candidates for precision measurements and tests of fundamental physics. A much slower molecular beam to increase the interaction time should lead to a more sensitive measurement. Here we theoretically demonstrate the possibility of the stimulated longitudinal slowing of heavy-atom molecules by the coherent optical bichromatic force with a constant beat phase. Taking the YbF meolecule as an example, we show that a rapid and short-distance deceleration of heavy molecules by a phase-compensation method is feasible with moderate conditions. A molecular beam of YbF with a forward velocity of 120 m/s can be decelerated below 10 m/s within a distance of 3.5 cm and with a laser irradiance for each traveling wave of 107.2 W/cm 2 . Our proposed slowing method could be a promising approach to break through the space constraint or the limited capture efficiency of molecules loadable into a magneto-optical trap in traditional deceleration schemes, opening the possibility for a significant improvement of the precision measurement sensitivity.

Classical study of the rovibrational dynamics of a polar diatomic molecule in static electric fields

Energy Technology Data Exchange (ETDEWEB)

Inarrea, Manuel, E-mail: manuel.inarrea@unirioja.e [Area de Fisica, Universidad de la Rioja, E-26006 Logrono (Spain); Salas, J. Pablo [Area de Fisica, Universidad de la Rioja, E-26006 Logrono (Spain); Gonzalez-Ferez, Rosario [Instituto ' Carlos I' de Fisica Teorica y Computacional, Universidad de Granada, E-18071 Granada (Spain); Departamento de Fisica Atomica, Molecular y Nuclear, Universidad de Granada, E-18071 Granada (Spain); Schmelcher, Peter [Theoretische Chemie, Physikalisch-Chemisches Institut, D-69120 Heidelberg (Germany); Physikalisches Institut, Universitaet Heidelberg, D-69120 Heidelberg (Germany)

2010-01-04

We study the classical dynamics of a polar diatomic molecule in the presence of a strong static homogeneous electric field. Our full rovibrational investigation includes the interaction with the field due to the permanent electric dipole moment and the polarizability of the molecule. Using the LiCs molecule as a prototype, we explore the stability of the equilibrium points and their bifurcations as the field strength is increased. The phase space structure and its dependence on the energy and field strength are analyzed in detail. We demonstrate that depending on the field strength and on the energy, the phase space is characterized either by regular features or by small stochastic layers of chaotic motion.

Charge-Transfer States in Organic Solar Cells: Understanding the Impact of Polarization, Delocalization, and Disorder

KAUST Repository

Zheng, Zilong; Tummala, Naga Rajesh; Fu, Yao-Tsung; Coropceanu, Veaceslav; Bredas, Jean-Luc

2017-01-01

pentacene molecules and three C60 molecules allows us to take explicitly into account the electronic polarization effects. These complexes are extracted from a bilayer architecture modeled by molecular dynamics simulations and evaluated by means

Tuning Interfacial States Using Organic Molecules as Spin Filters

Science.gov (United States)

Deloach, Andrew; Wang, Jingying; Papa, Christopher M.; Myahkostupov, Mykhaylo; Castellano, Felix N.; Dougherty, Daniel B.; Jiang, Wei; Liu, Feng

Organic semiconductors are known to have long spin relaxation times which makes them a good candidate for spintronics. However, an issue with these materials is that at metal-organic interfaces there is a conductivity mismatch problem that suppresses spin injection. To overcome this, orbital mixing at the interface can be tuned with an organic spacer layer to promote the formation of spin polarized interface states. These states act as a ``spin filters'' and have been proposed as an explanation for the large tunneling magnetoresistance seen in devices using tris-(8-hydroxyquinolate)-aluminum(Alq3). Here, we show that the spin polarized interface states can be tuned from metallic to resistive by subtle changes in molecular orbitals. This is done using spin polarized scanning tunneling microscopy with three different tris-(8-hydroxyquinolate) compounds: aluminum, chromium, and iron. Differences in d-orbital mixing results in different mechanisms of interfacial coupling, giving rise to metallic or resistive interface states. Supported by the U.S. DoE award No. DE-SC0010324.

Desorption of large organic molecules by laser-induced plasmon excitation

International Nuclear Information System (INIS)

Lee, I.; Callcott, T.A.

1991-01-01

Ejection of large organic molecules from surfaces by laser-induced electronic-excited desorption has attracted considerable interest in recent years. In addition to the importance of this effect for fundamental investigations of the ejection process, this desorption technique has been applied to the study of large, fragile molecules by mass spectrometry. In this paper, we present a new method to induce electronic excitation on the metal surface for the desorption of large organic molecules. 3 refs., 3 figs

Radiation-induced transformations of isolated organic molecules in solid rare gas matrices

International Nuclear Information System (INIS)

Feldman, V.I.

1998-01-01

Complete text of publication follows. The studies of radiation-chemical behaviour of isolated organic molecules in rigid inert media are of considerable interest for radiation chemistry and general structural chemistry. Previous efforts were limited to the ESR studies of radicals resulting from some small hydrocarbon molecules in frozen rare gas solutions. Recently, we developed an approach to the radiation chemistry of isolated organic molecules using classic matrix isolation procedure for sample preparation and a combination of ESR and IR spectroscopy for characterization of paramagnetic and diamagnetic species resulting form electron irradiation or organic molecules in solid rare gas matrices at 10-15 K. The results obtained reveal high efficiency of energy transfer from rare gas matrix to organic molecules. The total radiation-chemical yields of degradation of organic molecules in argon and xenon matrices were measured directly by IR spectroscopy. The studies of the effect of electron scavengers on the radiolysis of organic molecules in solid rare gases show that the main primary process is positive hole transfer from matrix to additive molecule. ESR spectra of a number of radical cations (alkanes, ethers, arenes) were first characterized in a low-disturbing environment. It was found that the electronic characteristics (IP, polarizability) of the matrix used had crucial effect on trapping and degradation of primary organic radical cations. Using matrices with various IP provides an unique possibility to examine the chemical meaning of excess energy resulting from exothermic positive hole transfer, that is, to follow the fate of excited cations in condensed phase

The influence of polarity of additive molecules on micelle structures of polystyrene-block-poly(4-vinylpyridine) in the fabrication of nano-porous templates.

Science.gov (United States)

Chua, Kee Sze; Koh, Ai Peng; Lam, Yeng Ming

2010-11-01

Block copolymers are useful for in situ synthesis of nanoparticles as well as producing nanoporous templates. As such, the effects of precursors on the block copolymer micelle structure is important. In this study, we investigate the effects of polarity of molecules introduced into block copolymer micelle cores on the micelle structure. The molecular dipole moment of the additive molecules has been evaluated and their effects on the block copolymer micelles investigated using light scattering spectroscopy, small-angle X-ray scattering, transmission electron microscopy and atomic force microscopy. The molecule with the largest dipole moment resulted in spherical structures with a polydispersity of less than 0.06 in a fully translational diffusion system. Surprisingly, the less polar additive molecules produced elongated micelles and the aspect ratio increases with decreasing polarity. The change in structure from spherical to elongated structure was attributed to P4VP chain extension, where compounds with polarity most similar to P4VP induce the most chain extension. The second virial coefficients of the solutions with elongated micelles are lower than that for spherical micelle systems by up to one order in magnitude, indicating a strong tendency for micelles to coalesce. On rinsing the spin-cast films, pores were obtained from spherical micelles and ridges from elongated micelles, suggesting a viable alternative for morphology modification using mild conditions where external annealing treatments to the film are not preferred. The knowledge of polarity effects of additive molecules on micelle structure has wider implications for supramolecular block copolymer systems where, depending on the application requirements, changes to the shape of the micelle structure can be induced or avoided. Copyright 2010 Elsevier Inc. All rights reserved.

Microtubule dynamics of the centrosome-like polar organizers from the basal land plant Marchantia polymorpha.

Science.gov (United States)

Buschmann, Henrik; Holtmannspötter, Michael; Borchers, Agnes; O'Donoghue, Martin-Timothy; Zachgo, Sabine

2016-02-01

The liverwort Marchantia employs both modern and ancestral devices during cell division: it forms preprophase bands and in addition it shows centrosome-like polar organizers. We investigated whether polar organizers and preprophase bands cooperate to set up the division plane. To this end, two novel green fluorescent protein-based microtubule markers for dividing cells of Marchantia were developed. Cells of the apical notch formed polar organizers first and subsequently assembled preprophase bands. Polar organizers were formed de novo from multiple mobile microtubule foci localizing to the nuclear envelope. The foci then became concentrated by bipolar aggregation. We determined the comet production rate of polar organizers and show that microtubule plus ends of astral microtubules polymerize faster than those found on cortical microtubules. Importantly, it was observed that conditions increasing polar organizer numbers interfere with preprophase band formation. The data show that polar organizers have much in common with centrosomes, but that they also have specialized features. The results suggest that polar organizers contribute to preprophase band formation and in this way are involved in controlling the division plane. Our analyses of the basal land plant Marchantia shed new light on the evolution of plant cell division. © 2015 The Authors. New Phytologist © 2015 New Phytologist Trust.

Challenges for single molecule electronic devices with nanographene and organic molecules. Do single molecules offer potential as elements of electronic devices in the next generation?

Science.gov (United States)

Enoki, Toshiaki; Kiguchi, Manabu

2018-03-01

Interest in utilizing organic molecules to fabricate electronic materials has existed ever since organic (molecular) semiconductors were first discovered in the 1950s. Since then, scientists have devoted serious effort to the creation of various molecule-based electronic systems, such as molecular metals and molecular superconductors. Single-molecule electronics and the associated basic science have emerged over the past two decades and provided hope for the development of highly integrated molecule-based electronic devices in the future (after the Si-based technology era has ended). Here, nanographenes (nano-sized graphene) with atomically precise structures are among the most promising molecules that can be utilized for electronic/spintronic devices. To manipulate single small molecules for an electronic device, a single molecular junction has been developed. It is a powerful tool that allows even small molecules to be utilized. External electric, magnetic, chemical, and mechanical perturbations can change the physical and chemical properties of molecules in a way that is different from bulk materials. Therefore, the various functionalities of molecules, along with changes induced by external perturbations, allows us to create electronic devices that we cannot create using current top-down Si-based technology. Future challenges that involve the incorporation of condensed matter physics, quantum chemistry calculations, organic synthetic chemistry, and electronic device engineering are expected to open a new era in single-molecule device electronic technology.

CO₂ Binding Organic Liquids Gas Capture with Polarity Swing Assisted Regeneration

Energy Technology Data Exchange (ETDEWEB)

Heldebrant, David [Battelle Memorial Institute, Columbus, OH (United States)

2014-05-31

This report outlines the comprehensive bench-scale testing of the CO₂-binding organic liquids (CO₂BOLs) solvent platform and its unique Polarity Swing Assisted Regeneration (PSAR). This study outlines all efforts on a candidate CO₂BOL solvent molecule, including solvent synthesis, material characterization, preliminary toxicology studies, and measurement of all physical, thermodynamic and kinetic data, including bench-scale testing. Equilibrium and kinetic models and analysis were made using Aspen Plus™. Preliminary process configurations, a technoeconomic assessment and solvent performance projections for separating CO₂ from a subcritical coal-fired power plant are compared to the U.S. Department of Energy's Case 10 monoethanolamine baseline.

Crystallization of Organic Semiconductor Molecules in Nanosized Cavities

DEFF Research Database (Denmark)

Milita, Silvia; Dionigi, Chiara; Borgatti, Francesco

2008-01-01

The crystallization of an organic semiconductor, viz., tetrahexil-sexithiophene (H4T6) molecules, confined into nanosized cavities of a self-organized polystyrene beads template, has been investigated by means of in situ grazing incidence X-ray diffraction measurements, during the solvent evapora...

Spin Coulomb Dragging Inhibition of Spin-Polarized Electric Current Injecting into Organic Semiconductors

International Nuclear Information System (INIS)

Jun-Qing, Zhao; Shi-Zhu, Qiao; Zhen-Feng, Jia; Ning-Yu, Zhang; Yan-Ju, Ji; Yan-Tao, Pang; Ying, Chen; Gang, Fu

2008-01-01

We introduce a one-dimensional spin injection structure comprising a ferromagnetic metal and a nondegenerate organic semiconductor to model electric current polarizations. With this model we analyse spin Coulomb dragging (SCD) effects on the polarization under various electric fields, interface and conductivity conditions. The results show that the SCD inhibits the current polarization. Thus the SCD inhibition should be well considered for accurate evaluation of current polarization in the design of organic spin devices

Transfers of Colloidal Silica from Water into Organic Solvents of Intermediate Polarities

Science.gov (United States)

Kasseh; Keh

1998-01-15

Dispersions of discrete metal-oxide submicroparticles in organic solvents of medium polarities are uneasy to generate and weakly documented. We address this topic along two general methods focusing on silica. Successive transfers of colloidal particles from water into n-propanol and then into 1,2-dichloroethane by azeotropic distillation yield a stable organosol. The particles are found to be propanol-coated by surface esterification to the extent of 0.40 nm2 per molecule. Alternatively, centrifugation-redispersion cycles make it possible to obtain stable suspensions of unaltered silica in methanol and acetonitrile starting from an aqueous silicasol. Particles are characterized by various methods including nitrogen adsorption, transmission electron microscopy, dynamic light scattering, and electrophoresis. The stabilities of these suspensions in various organic solvents are investigated with special concern for the role of residual water. Stabilization of silica in methanol is inconspicuously related to solvent permittivity and prominently dependent on the presence of adsorbed water. In contrast, the acetonitrile silicasol, which is unaffected by residual water, displays electrophoretic behavior compatible with electrostatic stabilization. Copyright 1998 Academic Press. Copyright 1998Academic Press

Prediction of Physicochemical Properties of Organic Molecules Using Semi-Empirical Methods

International Nuclear Information System (INIS)

Kim, Chan Kyung; Kim, Chang Kon; Kim, Miri; Lee, Hai Whang; Cho, Soo Gyeong

2013-01-01

Prediction of physicochemical properties of organic molecules is an important process in chemistry and chemical engineering. The MSEP approach developed in our lab calculates the molecular surface electrostatic potential (ESP) on van der Waals (vdW) surfaces of molecules. This approach includes geometry optimization and frequency calculation using hybrid density functional theory, B3LYP, at the 6-31G(d) basis set to find minima on the potential energy surface, and is known to give satisfactory QSPR results for various properties of organic molecules. However, this MSEP method is not applicable to screen large database because geometry optimization and frequency calculation require considerable computing time. To develop a fast but yet reliable approach, we have re-examined our previous work on organic molecules using two semi-empirical methods, AM1 and PM3. This new approach can be an efficient protocol in designing new molecules with improved properties

Beam broadening of polar molecules and clusters in deflection experiments.

Science.gov (United States)

Bulthuis, J; Kresin, V V

2012-01-07

A beam of rotating dipolar particles (molecules or clusters) will broaden when passed through an electric or magnetic field gradient region. This broadening, which is a common experimental observable, can be expressed in terms of the variance of the distribution of the resulting polarization orientation (the direction cosine). Here, the broadening for symmetric-top and linear rotors is discussed. These two types of rotors have qualitatively different low-field orientation distribution functions, but behave similarly in a strong field. While analytical expressions for the polarization variance can be derived from first-order perturbation theory, for experimental guidance it is important to identify the applicability and limitations of these expressions, and the general dependence of the broadening on the experimental parameters. For this purpose, the analytical results are compared with the full diagonalization of the rotational Stark-effect matrices. Conveniently for experimental estimations, it is found that for symmetric tops, the dependence of the broadening parameter on the rotational constant, the axial ratio, and the field strength remains similar to the analytical expression even outside of the perturbative regime. Also, it is observed that the shape envelope, the centroid, and the width of the orientation distribution function for a symmetric top are quite insensitive to the value of its rotational constant (except at low rotational temperatures).

Sorption of polar and nonpolar organic contaminants by oil-contaminated soil.

Science.gov (United States)

Chen, Hong; Chen, Shuo; Quan, Xie; Zhao, Huimin; Zhang, Yaobin

2008-12-01

Sorption of nonpolar (phenanthrene and butylate) and polar (atrazine and diuron) organic chemicals to oil-contaminated soil was examined to investigate oil effects on sorption of organic chemicals and to derive oil-water distribution coefficients (K(oil)). The resulting oil-contaminated soil-water distribution coefficients (K(d)) for phenanthrene demonstrated sorption-enhancing effects at both lower and higher oil concentrations (C(oil)) but sorption-reducing (competitive) effects at intermediate C(oil) (approximately 1 g kg(-1)). Rationalization of the different dominant effects was attempted in terms of the relative aliphatic carbon content which determines the accessibility of the aromatic cores to phenanthrene. Little or no competitive effect occurred for butylate because its sorption was dominated by partitioning. For atrazine and diuron, the changes in K(d) at C(oil) above approximately 1 g kg(-1) were negligible, indicating that the presently investigated oil has little or no effect on the two tested compounds even though the polarity of the oil is much less than soil organic matter (SOM). Therefore, specific interactions with the active groups (aromatic and polar domains) are dominantly responsible for the sorption of polar sorbates, and thus their sorption is controlled by available sorption sites. This study showed that the oil has the potential to be a dominant sorptive phase for nonpolar pollutants when compared to SOM, but hardly so for polar compounds. The results may aid in a better understanding of the role of the aliphatic and aromatic domains in sorption of nonpolar and polar organic pollutants.

Fgf8-related secondary organizers exert different polarizing planar instructions along the mouse anterior neural tube.

Science.gov (United States)

Crespo-Enriquez, Ivan; Partanen, Juha; Martinez, Salvador; Echevarria, Diego

2012-01-01

Early brain patterning depends on proper arrangement of positional information. This information is given by gradients of secreted signaling molecules (morphogens) detected by individual cells within the responding tissue, leading to specific fate decisions. Here we report that the morphogen FGF8 exerts initially a differential signal activity along the E9.5 mouse neural tube. We demonstrate that this polarizing activity codes by RAS-regulated ERK1/2 signaling and depends on the topographical location of the secondary organizers: the isthmic organizer (IsO) and the anterior neural ridge (anr) but not on zona limitans intrathalamica (zli). Our results suggest that Sprouty2, a negative modulator of RAS/ERK pathway, is important for regulating Fgf8 morphogenetic signal activity by controlling Fgf8-induced signaling pathways and positional information during early brain development.

Photoinduced electric currents in ring-shaped molecules by circularly polarized laser pulses

International Nuclear Information System (INIS)

Nobusada, Katsuyuki; Yabana, Kazuhiro

2007-01-01

We have theoretically demonstrated that circularly polarized laser pulses induce electric currents and magnetic moments in ring-shaped molecules Na 10 and benzene. The time-dependent adiabatic local density approximation is employed for this purpose, solving the time-dependent Kohn-Sham equation in real space and real time. It has been found that the electric currents are induced efficiently and persist continuously even after the laser pulses were switched off provided the frequency of the applied laser pulse is in tune with the excitation energy of the electronic excited state with the dipole strength for each molecular system. The electric currents are definitely revealed to be a second-order nonlinear optical response to the magnitude of the electric field. The magnetic dipole moments inevitably accompany the ring currents, so that the molecules are magnetized. The production of the electric currents and the magnetic moments in the present procedure is found to be much more efficient than that utilizing static magnetic fields

Effects of humic acid and heavy metals on the sorption of polar and apolar organic pollutants onto biochars

International Nuclear Information System (INIS)

Wang, Fei; Sun, Hongwen; Ren, Xinhao; Liu, Yarui; Zhu, Hongkai; Zhang, Peng; Ren, Chao

2017-01-01

The effects of humic acid (HA) and heavy metals (Cu 2+ and Ag + ) on the sorption of polar and apolar organic pollutants onto biochars that were produced at temperatures of 200 °C (BC200) and 700 °C (BC700) were studied. Due to the plentiful polar functional groups on BC200, cationic propranolol exhibited higher levels of sorption than naphthalene on BC200 while naphthalene and propranolol showed similar sorption capacities on BC700. HA changed the characteristics of biochars and generally inhibited the sorption of target organic pollutants on biochars; however, enhancement occurred in some cases depending on the pollutants involved and their concentrations, biochars used and the addition sequences and concentrations of HA. On BC200, HA modifications mainly influenced sorption by decreasing its polarity and increasing its aromaticity, while on BC700, the surface area and pore volume greatly decreased due to the pore-blocking effects of HA. Residue dissolved HA in solution may also contribute to sorption inhibition. Complexation between polar functional groups on BC200 and heavy metals slightly enhanced the sorption of neutral naphthalene and significantly enhanced that of anionic 4-nitro-1-naphtol, while limited the sorption of cationic propranolol. Heavy metals together with their associated water molecules decreased the sorption of target chemicals on BC700 via pore-filling or pore-mouth-covering. Inhibition of heavy metals for 4-nitro-1-naphthol was found to be the weakest due to the bridge effects of heavy metals between 4-nitro-1-naphtol and BC700. The higher polarizability of Ag + led to the increase of its sorption on biochars in the presence of organic aromatic pollutants. The results of the present study shed light on the sorption mechanisms of bi-solute systems and enable us to select suitable biochar sorbents when chemicals co-exist. - Highlights: • Polar functional groups on low-temperature biochar enhanced propranolol sorption. • Humic acid

Enhancement of molecular NMR signal induced by polarization transfer from laser-polarized 129Xe

International Nuclear Information System (INIS)

Sun Xianping

2001-01-01

There is a large non-equilibrium nuclear polarization and a longer relaxation time in the laser-polarized 129 Xe produced by means of optical pumping and spin exchange. The characteristics of the laser-polarized 129 Xe permit the transfer of the polarization to enhance the atomic nuclear spin in liquid, solid and surface of solid molecules. Therefore, the sensitivity in nuclear magnetic resonance measurements for the molecules is enhanced and applications in the investigations of materials and surface sciences are expanded. The progress in the investigations of materials and surface sciences are expanded. The progress in the investigations of the polarization transfer between laser-polarized 129 Xe and the atomic nuclei in the molecules, the relative physics and the measurement of some parameters are introduced

Inorganic-Organic Molecules and Solids with Nanometer-Sized Pores

Energy Technology Data Exchange (ETDEWEB)

Maverick, Andrew W

2011-12-17

We are constructing porous inorganic-organic hybrid molecules and solids, many of which contain coordinatively unsaturated metal centers. In this work, we use multifunctional ²-diketone ligands as building blocks to prepare extended-solid and molecular porous materials that are capable of reacting with a variety of guest molecules.

Conjugated donor-acceptor-acceptor (D-A-A) molecule for organic nonvolatile resistor memory.

Science.gov (United States)

Dong, Lei; Li, Guangwu; Yu, An-Dih; Bo, Zhishan; Liu, Cheng-Liang; Chen, Wen-Chang

2014-12-01

A new donor-acceptor-acceptor (D-A-A) type of conjugated molecule, N-(4-(N',N'-diphenyl)phenylamine)-4-(4'-(2,2-dicyanovinyl)phenyl) naphthalene-1,8-dicarboxylic monoimide (TPA-NI-DCN), consisting of triphenylamine (TPA) donors and naphthalimide (NI)/dicyanovinylene (DCN) acceptors was synthesized and characterized. In conjunction with previously reported D-A based materials, the additional DCN moiety attached as end group in the D-A-A configuration can result in a stable charge transfer (CT) and charge-separated state to maintain the ON state current. The vacuum-deposited TPA-NI-DCN device fabricated as an active memory layer was demonstrated to exhibit write-once-read-many (WORM) switching characteristics of organic nonvolatile memory due to the strong polarity of the TPA-NI-DCN moiety. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Multiorbital effects in strong-field ionization and dissociation of aligned polar molecules CH3I and CH3Br

Science.gov (United States)

Luo, Sizuo; Zhou, Shushan; Hu, Wenhui; Li, Xiaokai; Ma, Pan; Yu, Jiaqi; Zhu, Ruihan; Wang, Chuncheng; Liu, Fuchun; Yan, Bing; Liu, Aihua; Yang, Yujun; Guo, Fuming; Ding, Dajun

2017-12-01

Controlling the molecular axis offers additional ways to study molecular ionization and dissociation in strong laser fields. We measure the ionization and dissociation yields of aligned polar CH3X (X =I , Br) molecules in a linearly polarized femtosecond laser field. The current data show that maximum ionization occurs when the laser polarization is perpendicular to the molecular C -X axis, and dissociation prefers to occur at the laser polarization parallel to the C -X axis. The observed angular distributions suggest that the parent ions are generated by ionization from the HOMO. The angular distribution of fragment ions indicates that dissociation occurs mainly from an ionic excited state produced by ionization from the HOMO-1.

In Situ Detection of Organic Molecules on the Martian Surface With the Mars Organic Molecule Analyzer (MOMA) on Exomars 2018

Science.gov (United States)

Li, Xiang; Brinckerhoff, William B.; Pinnick, Veronica T; van Amerom, Friso H. W.; Danell, Ryan M.; Arevalo, Ricardo D., Jr.; Getty, Stephanie; Mahaffy, Paul R.

2015-01-01

The Mars Organic Molecule Analyzer (MOMA) investigation on the 2018 ExoMars rover will examine the chemical composition of samples acquired from depths of up to two meters below the martian surface, where organics may be protected from radiative and oxidative degradation. The MOMA instrument is centered around a miniaturized linear ion trap (LIT) that facilitates two modes of operation: i) pyrolysisgas chromatography mass spectrometry (pyrGC-MS); and, ii) laser desorptionionization mass spectrometry (LDI-MS) at ambient Mars pressures. The LIT also enables the structural characterization of complex molecules via complementary analytical capabilities, such as multi-frequency waveforms (i.e., SWIFT) and tandem mass spectrometry (MSMS). When combined with the complement of instruments in the rovers Pasteur Payload, MOMA has the potential to reveal the presence of a wide range of organics preserved in a variety of mineralogical environments, and to begin to understand the structural character and potential origin of those compounds.

Manipulation and control of the interfacial polarization in organic light-emitting diodes by dipolar doping

Directory of Open Access Journals (Sweden)

Lars Jäger

2016-09-01

Full Text Available Most of the commonly used electron transporting materials in organic light-emitting diodes exhibit interfacial polarization resulting from partially aligned permanent dipole moments of the molecules. This property modifies the internal electric field distribution of the device and therefore enables an earlier flat band condition for the hole transporting side, leading to improved charge carrier injection. Recently, this phenomenon was studied with regard to different materials and degradation effects, however, so far the influence of dilution has not been investigated. In this paper we focus on dipolar doping of the hole transporting material 4,4-bis[N-(1-naphthyl-N-phenylamino]-biphenyl (NPB with the polar electron transporting material tris-(8-hydroxyquinolate aluminum (Alq3. Impedance spectroscopy reveals that changes of the hole injection voltage do not scale in a simple linear fashion with the effective thickness of the doped layer. In fact, the measured interfacial polarization reaches a maximum value for a 1:1 blend. Taking the permanent dipole moment of Alq3 into account, an increasing degree of dipole alignment is found for decreasing Alq3 concentration. This observation can be explained by the competition between dipole-dipole interactions leading to dimerization and the driving force for vertical orientation of Alq3 dipoles at the surface of the NPB layer.

Manipulation and control of the interfacial polarization in organic light-emitting diodes by dipolar doping

Science.gov (United States)

Jäger, Lars; Schmidt, Tobias D.; Brütting, Wolfgang

2016-09-01

Most of the commonly used electron transporting materials in organic light-emitting diodes exhibit interfacial polarization resulting from partially aligned permanent dipole moments of the molecules. This property modifies the internal electric field distribution of the device and therefore enables an earlier flat band condition for the hole transporting side, leading to improved charge carrier injection. Recently, this phenomenon was studied with regard to different materials and degradation effects, however, so far the influence of dilution has not been investigated. In this paper we focus on dipolar doping of the hole transporting material 4,4-bis[N-(1-naphthyl)-N-phenylamino]-biphenyl (NPB) with the polar electron transporting material tris-(8-hydroxyquinolate) aluminum (Alq3). Impedance spectroscopy reveals that changes of the hole injection voltage do not scale in a simple linear fashion with the effective thickness of the doped layer. In fact, the measured interfacial polarization reaches a maximum value for a 1:1 blend. Taking the permanent dipole moment of Alq3 into account, an increasing degree of dipole alignment is found for decreasing Alq3 concentration. This observation can be explained by the competition between dipole-dipole interactions leading to dimerization and the driving force for vertical orientation of Alq3 dipoles at the surface of the NPB layer.

A rapid and sensitive method for the simultaneous analysis of aliphatic and polar molecules containing free carboxyl groups in plant extracts by LC-MS/MS

Directory of Open Access Journals (Sweden)

Bonaventure Gustavo

2009-11-01

Full Text Available Abstract Background Aliphatic molecules containing free carboxyl groups are important intermediates in many metabolic and signalling reactions, however, they accumulate to low levels in tissues and are not efficiently ionized by electrospray ionization (ESI compared to more polar substances. Quantification of aliphatic molecules becomes therefore difficult when small amounts of tissue are available for analysis. Traditional methods for analysis of these molecules require purification or enrichment steps, which are onerous when multiple samples need to be analyzed. In contrast to aliphatic molecules, more polar substances containing free carboxyl groups such as some phytohormones are efficiently ionized by ESI and suitable for analysis by LC-MS/MS. Thus, the development of a method with which aliphatic and polar molecules -which their unmodified forms differ dramatically in their efficiencies of ionization by ESI- can be simultaneously detected with similar sensitivities would substantially simplify the analysis of complex biological matrices. Results A simple, rapid, specific and sensitive method for the simultaneous detection and quantification of free aliphatic molecules (e.g., free fatty acids (FFA and small polar molecules (e.g., jasmonic acid (JA, salicylic acid (SA containing free carboxyl groups by direct derivatization of leaf extracts with Picolinyl reagent followed by LC-MS/MS analysis is presented. The presence of the N atom in the esterified pyridine moiety allowed the efficient ionization of 25 compounds tested irrespective of their chemical structure. The method was validated by comparing the results obtained after analysis of Nicotiana attenuata leaf material with previously described analytical methods. Conclusion The method presented was used to detect 16 compounds in leaf extracts of N. attenuata plants. Importantly, the method can be adapted based on the specific analytes of interest with the only consideration that the

Collective phenomena in a quasi-two-dimensional system of fermionic polar molecules: Band renormalization and excitons

International Nuclear Information System (INIS)

Babadi, Mehrtash; Demler, Eugene

2011-01-01

We theoretically analyze a quasi-two-dimensional system of fermionic polar molecules trapped in a harmonic transverse confining potential. The renormalized energy bands are calculated by solving the Hartree-Fock equation numerically for various trap and dipolar interaction strengths. The intersubband excitations of the system are studied in the conserving time-dependent Hartree-Fock (TDHF) approximation from the perspective of lattice modulation spectroscopy experiments. We find that the excitation spectrum consists of both intersubband particle-hole excitation continua and antibound excitons whose antibinding behavior is associated to the anisotropic nature of dipolar interactions. The excitonic modes are shown to capture the majority of the spectral weight. We evaluate the intersubband transition rates in order to investigate the nature of the excitonic modes and find that they are antibound states formed from particle-hole excitations arising from several subbands. We discuss the sum rules in the context of lattice modulation spectroscopy experiments and utilize them to check the consistency of the obtained results. Our results indicate that the excitonic effects persist for interaction strengths and temperatures accessible in the current experiments with polar molecules.

Simultaneous atomization and ionization of large organic molecules using femtosecond laser ablation

International Nuclear Information System (INIS)

Kurata-Nishimura, Mizuki; Tokanai, Fuyuki; Matsuo, Yukari; Kobayashi, Tohru; Kawai, Jun; Kumagai, Hiroshi; Midorikawa, Katsumi; Tanihata, Isao; Hayashizaki, Yoshihide

2002-01-01

We have experimentally demonstrated femtosecond laser ablation for simultaneous atomization and ionization (fs-SAI) of organic molecules on solid substrates. We find most of the constituent atoms of organic molecules are atomized and ionized non-resonantly by femtosecond laser ablation. This observation is in contrast with that for the photoionization of cyclic aromatic hydrocarbons by femtosecond laser in the gas phase where little fragmentation has been observed. Crucial contribution of ablation plasma of solid sample to fs-SAI process is suggested. The ratio of natural abundance of stable isotopes contained in sample molecules is well reproduced, which confirms fs-SAI can be applied to the quantitative chemical analysis of isotope-labeled large organic molecules

Bifunctional Pt-Si Alloys for Small Organic Molecule Electro-oxidation

DEFF Research Database (Denmark)

Permyakova, Anastasia Aleksandrovna; Suntivich, Jin; Han, Binghong

Designing highly active catalysts for electro-oxidation of small organic molecules can help to reduce the anodic overpotential for more efficient utilization of hydrocarbon fuels. The challenge in developing more active electrocatalysts for electro-oxidation reactions is to satisfy the stringent...... adsorption site. We will discuss the enhanced activity of Pt-Si alloys for small organic molecule oxidation, which can be attributed to the improved CO electro-oxidation kinetics on Pt-Si....

Inorganics in Organics: Tracking down the Intrinsic Equilibriums between Organic Molecules and Trace Elements in Oceanic Waters

Science.gov (United States)

Lechtenfeld, O. J.; Koch, B. P.; Kattner, G.

2010-12-01

Recent developments in analytical instrumentation enable to describe biogeochemical processes in oceanic waters on a molecular level. This is the prerequisite to integrate biological and geochemical parameters and to develop chemical cycles on a global perspective. The state-of-the-art Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) applications for dissolved organic matter (DOM) focus mainly on carbon, hydrogen, oxygen and nitrogen isotopes. Implementation of sulfur and especially phosphorus in the molecular formula assignment has been questionable because of ambiguous calculated elemental formulas. On the other hand, many compounds bearing these elements are well known to occur in the dissolved state as part of the permanent recycling processes (e.g. phospholipids, phosphonates) but analytics of dissolved organic phosphorus (DOP) and sulfur (DOS) are often hampered by the large inorganic P and S pools. Even less is known about complexation characteristics of the DOM moieties. Although electrochemical methods provide some information about trace metal speciation, the high amount of organic molecules and its insufficient description as chemical functional classes prevent the assignment of trace metals to ligand classes. Nevertheless, it is undoubtful that a varying but extensive amount of transition metals is bond in form of organic complexes. Hyphenation of reversed phase high performance liquid chromatography (RP-HPLC) with high resolution inductively coupled plasma mass spectrometry (HR-ICP-MS) is a valuable tool to study these metal-organic interactions in a qualitative and quantitative approach. We established a desolvation method that allows direct transfer of high organic solvent loads into the plasma. Thus, in combination with internal standardization and external calibration, the investigation of a broad polarity scale was possible. This approach overcomes previous restrictions to non-organic solvent separation techniques like size

Organic Nanowires

DEFF Research Database (Denmark)

Balzer, Frank; Schiek, Manuela; Al-Shamery, Katharina

Single crystalline nanowires from fluorescing organic molecules like para-phenylenes or thiophenes are supposed to become key elements in future integrated optoelectronic devices [1]. For a sophisticated design of devices based on nanowires the basic principles of the nanowire formation have...... atomic force microscopy and from polarized far-field optical microscopy for various prototypical molecules are reproduced by electrostatic and Monte Carlo calculations. Based on the crystal structure, predictions on the growth habit from other conjugated molecules become in reach....

Preparation of translationally cold neutral molecules.

Science.gov (United States)

Di Domenicantonio, Giulia; Bertsche, Benjamin; Osterwalder, Andreas

2011-01-01

Efforts at EPFL to obtain translationally cold neutral molecules are described. Active deceleration of polar molecules is performed by confining the molecules in moving three-dimensional electrostatic traps, and by appropriately choosing the velocity of those traps. Alternatively, cold molecules can be obtained by velocity filtering. Here, the velocity of the molecules is not changed, but instead the cold molecules are extracted from a thermal sample by using the competition between the electrostatic force and the centrifugal force inside a bent electrostatic guide for polar molecules.

M-CARS and EFISHG study of the influence of a static electric field on a non-polar molecule

Science.gov (United States)

Capitaine, E.; Louot, C.; Ould-Moussa, N.; Lefort, C.; Kaneyasu, J. F.; Kano, H.; Pagnoux, D.; Couderc, V.; Leproux, P.

2016-03-01

The influence of a static electric field on a non-polar molecule has been studied by means of multiplex coherent anti-Stokes Raman scattering (M-CARS). A parallel measurement of electric field induced second harmonic generation (EFISHG) has also been led. Both techniques suggest a reorientation of the molecule due to the presence of an electric field. This phenomenon can be used to increase the chemical selectivity and the signal to non-resonant background ratio, namely, the sensitivity of the M-CARS spectroscopy.

Self-organizing periodicity in development: organ positioning in plants.

Science.gov (United States)

Bhatia, Neha; Heisler, Marcus G

2018-02-08

Periodic patterns during development often occur spontaneously through a process of self-organization. While reaction-diffusion mechanisms are often invoked, other types of mechanisms that involve cell-cell interactions and mechanical buckling have also been identified. Phyllotaxis, or the positioning of plant organs, has emerged as an excellent model system to study the self-organization of periodic patterns. At the macro scale, the regular spacing of organs on the growing plant shoot gives rise to the typical spiral and whorled arrangements of plant organs found in nature. In turn, this spacing relies on complex patterns of cell polarity that involve feedback between a signaling molecule - the plant hormone auxin - and its polar, cell-to-cell transport. Here, we review recent progress in understanding phyllotaxis and plant cell polarity and highlight the development of new tools that can help address the remaining gaps in our understanding. © 2018. Published by The Company of Biologists Ltd.

Polarized nuclear target based on parahydrogen induced polarization

OpenAIRE

Budker, D.; Ledbetter, M. P.; Appelt, S.; Bouchard, L. S.; Wojtsekhowski, B.

2012-01-01

We discuss a novel concept of a polarized nuclear target for accelerator fixed-target scattering experiments, which is based on parahydrogen induced polarization (PHIP). One may be able to reach a 33% free-proton polarization in the ethane molecule. The potential advantages of such a target include operation at zero magnetic field, fast ($\\sim$100 Hz) polarization reversal, and operation with large intensity of an electron beam.

Rotational state dependence of ion-polar molecule reactions at very low temperature

International Nuclear Information System (INIS)

Dubernet, M.L.; McCarroll, R.

1989-01-01

The adiabatic rotational state method is used to investigate the rotational state dependence of the rate coefficients for ion-polar molecule reactions in the very low temperature regime characteristic of interstellar molecular clouds. Results obtained for the systems H 3 + +HCl and H 3 + +HCN indicate that all the methods based on the adiabatic separation of the rotational and radial motion of the collision complex - adiabatic capture centrifugal sudden approximation (ACCSA), statistical adiabatic channel model, classical adiabatic invariance method - agree very satisfactorily in the low temperature limit. Discrepancies observed between some of the published data would appear to arise from numerical inaccuracies rather than from any defect of the theory. (orig.)

Structure and Structure-activity Relationship of Functional Organic Molecules

Institute of Scientific and Technical Information of China (English)

2011-01-01

@@ Research theme The group is made up of junior scientists from the State Key Laboratory of Elemento-organic Chemistry, Nankai University.The scientists focus their studis on the structure and structure-activity relationship of functional organic molecules not only because it has been the basis of their research, but also because the functional study of organic compounds is now a major scientific issue for organic chemists around the world.

Photoluminescence of CdSe/ZnS/TOPO nanocrystals expanded on silica glass substrates: Adsorption and desorption effects of polar molecules on nanocrystal surfaces

International Nuclear Information System (INIS)

Oda, Masaru; Tsukamoto, Junpei; Hasegawa, Atsushi; Iwami, Noriya; Nishiura, Ken; Hagiwara, Izumi; Ando, Naohisa; Horiuchi, Hiromi; Tani, Toshiro

2006-01-01

We have investigated photoluminescence (PL) properties of CdSe/ZnS/TOPO nanocrystals (NCs) in various kinds of gases at one atmospheric pressure. Increase of PL intensity with spectral shift is observed under 488 nm cw light irradiation in all cases. Especially, the PL intensity increases more than twice after 1200 s irradiation in nitrogen gases saturated with vapor of polar molecules, such as H 2 O and NH 3 . The increased PL intensity with the spectral shift mostly recovers to its previous values when the sample is evacuated under continuous light irradiation. These results indicate that photo-adsorption of the polar molecules onto NC surfaces provides some reversible restoring functions to the PL quenching defects or trap sites on or near the surfaces. The existence of the trap sites on NC surfaces is already widely introduced for describing e.g., blinking phenomena. Assuming part of these traps being charged, we propose the photo-induced effects can be understood as charge-compensated inactivation of the trap sites due to the adsorption of the polar molecules consistently

Tuning polarity and improving charge transport in organic semiconductors

Science.gov (United States)

Oh, Joon Hak; Han, A.-Reum; Yu, Hojeong; Lee, Eun Kwang; Jang, Moon Jeong

2013-09-01

Although state-of-the-art ambipolar polymer semiconductors have been extensively reported in recent years, highperformance ambipolar polymers with tunable dominant polarity are still required to realize on-demand, target-specific, high-performance organic circuitry. Herein, dithienyl-diketopyrrolopyrrole (TDPP)-based polymer semiconductors with engineered side-chains have been synthesized, characterized and employed in ambipolar organic field-effect transistors, in order to achieve controllable and improved electrical properties. Thermally removable tert-butoxycarbonyl (t-BOC) groups and hybrid siloxane-solubilizing groups are introduced as the solubilizing groups, and they are found to enable the tunable dominant polarity and the enhanced ambipolar performance, respectively. Such outstanding performance based on our molecular design strategies makes these ambipolar polymer semiconductors highly promising for low-cost, large-area, and flexible electronics.

Desorption of large organic molecules induced by keV projectiles

International Nuclear Information System (INIS)

Delcorte, A.; Garrison, B.J.

2001-01-01

In order to understand the emission of organic molecules in sputtering, classical molecular dynamics (MD) is used to model the 5 keV Ar atom bombardment of polystyrene oligomers adsorbed on Ag{1 1 1}. The analysis of the results shows that a significant fraction of the trajectories generates high action events in the sample. These events are characterized by the simultaneous motion of several hundreds of substrate atoms and, oftentimes, by high emission yields of substrate atoms, clusters and polystyrene molecules. Collision trees representing the energetic part of the cascades confirm that high sputtering yields of molecules occur when a large portion of the primary particle energy is quickly dissipated in the upper layers of the silver substrate. This class of events where high action occurs in the surface region might explain the ejection of organic species with a mass of several kilodaltons such as biomolecules and synthetic polymers. In the simulation, these events are capable of desorbing polystyrene molecules of ∼2 kDa

Spin- and energy-dependent tunneling through a single molecule with intramolecular spatial resolution.

Science.gov (United States)

Brede, Jens; Atodiresei, Nicolae; Kuck, Stefan; Lazić, Predrag; Caciuc, Vasile; Morikawa, Yoshitada; Hoffmann, Germar; Blügel, Stefan; Wiesendanger, Roland

2010-07-23

We investigate the spin- and energy-dependent tunneling through a single organic molecule (CoPc) adsorbed on a ferromagnetic Fe thin film, spatially resolved by low-temperature spin-polarized scanning tunneling microscopy. Interestingly, the metal ion as well as the organic ligand show a significant spin dependence of tunneling current flow. State-of-the-art ab initio calculations including also van der Waals interactions reveal a strong hybridization of molecular orbitals and substrate 3d states. The molecule is anionic due to a transfer of one electron, resulting in a nonmagnetic (S=0) state. Nevertheless, tunneling through the molecule exhibits a pronounced spin dependence due to spin-split molecule-surface hybrid states.

Toxicity of natural mixtures of organic pollutants in temperate and polar marine phytoplankton

KAUST Repository

Echeveste, Pedro

2016-07-26

Semivolatile and persistent organic pollutants (POPs) undergo atmospheric transport before being deposited to the oceans, where they partition to phytoplankton organic matter. The goal of this study was to determine the toxicity of naturally occurring complex mixtures of organic pollutants to temperate and polar phytoplankton communities from the Mediterranean Sea, the North East (NE) Atlantic, and Southern Oceans. The cell abundance of the different phytoplankton groups, chlorophyll a concentrations, viability of the cells, and growth and decay constants were monitored in response to addition of a range of concentrations of mixtures of organic pollutants obtained from seawater extracts. Almost all of the phytoplankton groups were significantly affected by the complex mixtures of non-polar and polar organic pollutants, with toxicity being greater for these mixtures than for single POPs or simple POP mixtures. Cocktails\\' toxicity arose at concentrations as low as tenfold the field oceanic levels, probably due to a higher chemical activity of the mixture than of simple POPs mixtures. Overall, smaller cells were the most affected, although Mediterranean picophytoplankton was significantly more tolerant to non-polar POPs than picophytoplankton from the Atlantic Ocean or the Bellingshausen Sea microphytoplankton. © 2016 Elsevier B.V.

Prospects for reconstructing paleoenvironmental conditions from organic compounds in polar snow and ice

Science.gov (United States)

Giorio, Chiara; Kehrwald, Natalie; Barbante, Carlo; Kalberer, Markus; King, Amy C.F.; Thomas, Elizabeth R.; Wolff, Eric W.; Zennaro, Piero

2018-01-01

Polar ice cores provide information about past climate and environmental changes over periods ranging from a few years up to 800,000 years. The majority of chemical studies have focused on determining inorganic components, such as major ions and trace elements as well as on their isotopic fingerprint. In this paper, we review the different classes of organic compounds that might yield environmental information, discussing existing research and what is needed to improve knowledge. We also discuss the problems of sampling, analysis and interpretation of organic molecules in ice. This review highlights the great potential for organic compounds to be used as proxies for anthropogenic activities, past fire events from different types of biomass, terrestrial biogenic emissions and marine biological activity, along with the possibility of inferring past temperature fluctuations and even large-scale climate variability. In parallel, comprehensive research needs to be done to assess the atmospheric stability of these compounds, their ability to be transported long distances in the atmosphere, and their stability in the archive in order to better interpret their fluxes in ice cores. In addition, specific decontamination procedures, analytical methods with low detection limits (ng/L or lower), fast analysis time and low sample requests need to be developed in order to ensure a good time resolution in the archive.

Prospects for reconstructing paleoenvironmental conditions from organic compounds in polar snow and ice

Science.gov (United States)

Giorio, Chiara; Kehrwald, Natalie; Barbante, Carlo; Kalberer, Markus; King, Amy C. F.; Thomas, Elizabeth R.; Wolff, Eric W.; Zennaro, Piero

2018-03-01

Polar ice cores provide information about past climate and environmental changes over periods ranging from a few years up to 800,000 years. The majority of chemical studies have focused on determining inorganic components, such as major ions and trace elements as well as on their isotopic fingerprint. In this paper, we review the different classes of organic compounds that might yield environmental information, discussing existing research and what is needed to improve knowledge. We also discuss the problems of sampling, analysis and interpretation of organic molecules in ice. This review highlights the great potential for organic compounds to be used as proxies for anthropogenic activities, past fire events from different types of biomass, terrestrial biogenic emissions and marine biological activity, along with the possibility of inferring past temperature fluctuations and even large-scale climate variability. In parallel, comprehensive research needs to be done to assess the atmospheric stability of these compounds, their ability to be transported long distances in the atmosphere, and their stability in the archive in order to better interpret their fluxes in ice cores. In addition, specific decontamination procedures, analytical methods with low detection limits (ng/L or lower), fast analysis time and low sample requests need to be developed in order to ensure a good time resolution in the archive.

An Estimation of Hybrid Quantum Mechanical Molecular Mechanical Polarization Energies for Small Molecules Using Polarizable Force-Field Approaches.

Science.gov (United States)

Huang, Jing; Mei, Ye; König, Gerhard; Simmonett, Andrew C; Pickard, Frank C; Wu, Qin; Wang, Lee-Ping; MacKerell, Alexander D; Brooks, Bernard R; Shao, Yihan

2017-02-14

In this work, we report two polarizable molecular mechanics (polMM) force field models for estimating the polarization energy in hybrid quantum mechanical molecular mechanical (QM/MM) calculations. These two models, named the potential of atomic charges (PAC) and potential of atomic dipoles (PAD), are formulated from the ab initio quantum mechanical (QM) response kernels for the prediction of the QM density response to an external molecular mechanical (MM) environment (as described by external point charges). The PAC model is similar to fluctuating charge (FQ) models because the energy depends on external electrostatic potential values at QM atomic sites; the PAD energy depends on external electrostatic field values at QM atomic sites, resembling induced dipole (ID) models. To demonstrate their uses, we apply the PAC and PAD models to 12 small molecules, which are solvated by TIP3P water. The PAC model reproduces the QM/MM polarization energy with a R 2 value of 0.71 for aniline (in 10,000 TIP3P water configurations) and 0.87 or higher for other 11 solute molecules, while the PAD model has a much better performance with R 2 values of 0.98 or higher. The PAC model reproduces reference QM/MM hydration free energies for 12 solute molecules with a RMSD of 0.59 kcal/mol. The PAD model is even more accurate, with a much smaller RMSD of 0.12 kcal/mol, with respect to the reference. This suggests that polarization effects, including both local charge distortion and intramolecular charge transfer, can be well captured by induced dipole type models with proper parametrization.

Spin-polarization reversal at the interface between benzene and Fe(100)

KAUST Repository

Goumri-Said, Souraya

2013-01-03

The spin-polarization at the interface between Fe(100) and a benzene is investigated theoretically using density functional theory for two positions of the organic molecule: planar and perpendicular with respect to the substrate. The electronic and magnetic properties as well as the spin-polarization close to the Fermi level strongly depend on the benzene position on the iron surface. An inversion of the spin-polarization is induced by p-d hybridization and charge transfer from the iron to the carbon sites in both configurations.

Spin-polarization reversal at the interface between benzene and Fe(100)

KAUST Repository

Goumri-Said, Souraya; Benali Kanoun, Mohammed; Manchon, Aurelien; Schwingenschlö gl, Udo

2013-01-01

The spin-polarization at the interface between Fe(100) and a benzene is investigated theoretically using density functional theory for two positions of the organic molecule: planar and perpendicular with respect to the substrate. The electronic and magnetic properties as well as the spin-polarization close to the Fermi level strongly depend on the benzene position on the iron surface. An inversion of the spin-polarization is induced by p-d hybridization and charge transfer from the iron to the carbon sites in both configurations.

Polarization-induced transport in organic field-effect transistors: the role of ferroelectric dielectrics

Science.gov (United States)

Guha, Suchismita; Laudari, Amrit

2017-08-01

The ferroelectric nature of polymer ferroelectrics such as poly(vinylidene fluoride) (PVDF) has been known for over 45 years. However, its role in interfacial transport in organic/polymeric field-effect transistors (FETs) is not that well understood. Dielectrics based on PVDF and its copolymers are a perfect test-bed for conducting transport studies where a systematic tuning of the dielectric constant with temperature may be achieved. The charge transport mechanism in an organic semiconductor often occurs at the intersection of band-like coherent motion and incoherent hopping through localized states. By choosing two small molecule organic semiconductors - pentacene and 6,13 bis(triisopropylsilylethynyl)pentacene (TIPS-pentacene) - along with a copolymer of PVDF (PVDF-TrFe) as the dielectric layer, the transistor characteristics are monitored as a function of temperature. A negative coefficient of carrier mobility is observed in TIPS-pentacene upwards of 200 K with the ferroelectric dielectric. In contrast, TIPS-pentacene FETs show an activated transport with non-ferroelectric dielectrics. Pentacene FETs, on the other hand, show a weak temperature dependence of the charge carrier mobility in the ferroelectric phase of PVDF-TrFE, which is attributed to polarization fluctuation driven transport resulting from a coupling of the charge carriers to the surface phonons of the dielectric layer. Further, we show that there is a strong correlation between the nature of traps in the organic semiconductor and interfacial transport in organic FETs, especially in the presence of a ferroelectric dielectric.

Functional Fixedness and Functional Reduction as Common Sense Reasonings in Chemical Equilibrium and in Geometry and Polarity of Molecules.

Science.gov (United States)

Furio, C.; Calatayud, M. L.; Barcenas, S. L.; Padilla, O. M.

2000-01-01

Focuses on learning difficulties in procedural knowledge, and assesses the procedural difficulties of grade 12 and first- and third-year university students based on common sense reasoning in two areas of chemistry--chemical equilibrium and geometry, and polarity of molecules. (Contains 55 references.) (Author/YDS)

Exploring the aqueous vertical ionization of organic molecules by molecular simulation and liquid microjet photoelectron spectroscopy.

Science.gov (United States)

Tentscher, Peter R; Seidel, Robert; Winter, Bernd; Guerard, Jennifer J; Arey, J Samuel

2015-01-08

To study the influence of aqueous solvent on the electronic energy levels of dissolved organic molecules, we conducted liquid microjet photoelectron spectroscopy (PES) measurements of the aqueous vertical ionization energies (VIEaq) of aniline (7.49 eV), veratrole alcohol (7.68 eV), and imidazole (8.51 eV). We also reanalyzed previously reported experimental PES data for phenol, phenolate, thymidine, and protonated imidazolium cation. We then simulated PE spectra by means of QM/MM molecular dynamics and EOM-IP-CCSD calculations with effective fragment potentials, used to describe the aqueous vertical ionization energies for six molecules, including aniline, phenol, veratrole alcohol, imidazole, methoxybenzene, and dimethylsulfide. Experimental and computational data enable us to decompose the VIEaq into elementary processes. For neutral compounds, the shift in VIE upon solvation, ΔVIEaq, was found to range from ≈-0.5 to -0.91 eV. The ΔVIEaq was further explained in terms of the influence of deforming the gas phase solute into its solution phase conformation, the influence of solute hydrogen-bond donor and acceptor interactions with proximate solvent molecules, and the polarization of about 3000 outerlying solvent molecules. Among the neutral compounds, variability in ΔVIEaq appeared largely controlled by differences in solute-solvent hydrogen-bonding interactions. Detailed computational analysis of the flexible molecule veratrole alcohol reveals that the VIE is strongly dependent on molecular conformation in both gas and aqueous phases. Finally, aqueous reorganization energies of the oxidation half-cell ionization reaction were determined from experimental data or estimated from simulation for the six compounds aniline, phenol, phenolate, veratrole alcohol, dimethylsulfide, and methoxybenzene, revealing a surprising constancy of 2.06 to 2.35 eV.

Characterization of microenvironment polarity and solvent accessibility of polysilsesquioxane xerogels by the fluorescent probe technique

Energy Technology Data Exchange (ETDEWEB)

Shea, K.J.; Zhu, H.D. [Univ., of California, Irvine, CA (United States). Dept. of Chemistry; Loy, D.A. [Sandia National Labs., Albuquerque, NM (United States)

1995-05-01

Poly (1, 4 bis(triethoxysilyl)benzene) (PTESB), a representative of a new type of organic-inorganic hybrid polysilsesquioxane material, was characterized by fluorescence spectroscopy for both microenvironmental polarity and solvent accessibility. A dansyl fluorescent molecule was incorporated into the bulk as well as onto the surface of both PTESB and silica materials. Information about the microenvironment polarity and accessibility of PTESB to various organic solvents was determined and compared to that of silica gel. This study found that both the bulk and surface of PTESB are less polar than that of the silica material. The silica material is accessible to polar solvents and water, while YMB is accessible to polar solvents but not to water. The hydrophobicity of PTESB differentiates these new materials from silica gel.

Effects of humic acid and heavy metals on the sorption of polar and apolar organic pollutants onto biochars.

Science.gov (United States)

Wang, Fei; Sun, Hongwen; Ren, Xinhao; Liu, Yarui; Zhu, Hongkai; Zhang, Peng; Ren, Chao

2017-12-01

The effects of humic acid (HA) and heavy metals (Cu 2+ and Ag + ) on the sorption of polar and apolar organic pollutants onto biochars that were produced at temperatures of 200 °C (BC200) and 700 °C (BC700) were studied. Due to the plentiful polar functional groups on BC200, cationic propranolol exhibited higher levels of sorption than naphthalene on BC200 while naphthalene and propranolol showed similar sorption capacities on BC700. HA changed the characteristics of biochars and generally inhibited the sorption of target organic pollutants on biochars; however, enhancement occurred in some cases depending on the pollutants involved and their concentrations, biochars used and the addition sequences and concentrations of HA. On BC200, HA modifications mainly influenced sorption by decreasing its polarity and increasing its aromaticity, while on BC700, the surface area and pore volume greatly decreased due to the pore-blocking effects of HA. Residue dissolved HA in solution may also contribute to sorption inhibition. Complexation between polar functional groups on BC200 and heavy metals slightly enhanced the sorption of neutral naphthalene and significantly enhanced that of anionic 4-nitro-1-naphtol, while limited the sorption of cationic propranolol. Heavy metals together with their associated water molecules decreased the sorption of target chemicals on BC700 via pore-filling or pore-mouth-covering. Inhibition of heavy metals for 4-nitro-1-naphthol was found to be the weakest due to the bridge effects of heavy metals between 4-nitro-1-naphtol and BC700. The higher polarizability of Ag + led to the increase of its sorption on biochars in the presence of organic aromatic pollutants. The results of the present study shed light on the sorption mechanisms of bi-solute systems and enable us to select suitable biochar sorbents when chemicals co-exist. Copyright © 2017. Published by Elsevier Ltd.

Dark states in spin-polarized transport through triple quantum dot molecules

Science.gov (United States)

Wrześniewski, K.; Weymann, I.

2018-02-01

We study the spin-polarized transport through a triple-quantum-dot molecule weakly coupled to ferromagnetic leads. The analysis is performed by means of the real-time diagrammatic technique, including up to the second order of perturbation expansion with respect to the tunnel coupling. The emphasis is put on the impact of dark states on spin-resolved transport characteristics. It is shown that the interplay of coherent population trapping and cotunneling processes results in a highly nontrivial behavior of the tunnel magnetoresistance, which can take negative values. Moreover, a super-Poissonian shot noise is found in transport regimes where the current is blocked by the formation of dark states, which can be additionally enhanced by spin dependence of tunneling processes, depending on the magnetic configuration of the device. The mechanisms leading to those effects are thoroughly discussed.

Plasma-polymerized films providing selective affinity to the polarity of vaporized organic solvents

International Nuclear Information System (INIS)

Akimoto, Takuo; Ikeshita, Yusuke; Terashima, Ryo; Karube, Isao

2009-01-01

Plasma-polymerized films (PPFs) were fabricated as recognition membranes for a vapor-sensing device, and their affinity to vaporized organic solvents was evaluated with surface plasmon resonance. The affinity we intended to create is the selective sorption of the vaporized organic solvents depending on their polarity. For this purpose, acetonitrile, ethylenediamine (EDA), styrene, hexamethyldisiloxane (HMDSO), and hexamethyldisilazane were used to fabricate PPFs. Vaporized methanol, ethanol, and 1-propanol were used as high-polar solvents to be analyzed. Hexane, toluene, and p-xylene were used as low-polar solvents. As a result, the HMDSO-PPF with 97.3 o of contact angle was found to provide affinity to the low-polar solvents. In contrast, the EDA-PPF with 7.1 o of contact angle provided affinity to the high-polar solvents. Observations of the surface morphology of the HMDSO- and EDA-PPFs with a scanning electron microscope revealed that they are composed of nano-scale islands.

Mechanism of anterior-posterior polarity control in planarians

Energy Technology Data Exchange (ETDEWEB)

Lange, C.S.; Steele, V.E.

1978-01-01

The substance which inhibits brain formation in the regenerating planarian Dugesia etrusca was found to be a large molecule, at least in part protein, which electrophoreses as an electronegative moiety in pH 6.8 buffer. A model is presented, based on this finding and previous studies, which proposes an electrochemical mechanism for the control of polarity and possibly for the maintenance of tissue organization in planarians. It is proposed that a bioelectric field exists and moves the electronegative brain-inhibiting substance in a posterior direction, establishing polarity. This model explains the polarity reversal experiments using external fields and many of the previously unexplained classical planarian experiments. Data are presented demonstrating the existence, magnitude, and polarity of this bioelectric field, which is not greatly altered upon decapitation, all in accord with predictions of the model.

Exotic helium molecules; Molecules exotiques d'helium

Energy Technology Data Exchange (ETDEWEB)

Portier, M

2007-12-15

We study the photo-association of an ultracold cloud of magnetically trapped helium atoms: pairs of colliding atoms interact with one or two laser fields to produce a purely long range {sup 4}He{sub 2}(2{sup 3}S{sub 1}-2{sup 3}P{sub 0}) molecule, or a {sup 4}He{sub 2}(2{sup 3}S{sub 1}-2{sup 3}S{sub 1}) long range molecule. Light shifts in one photon photo-association spectra are measured and studied as a function of the laser polarization and intensity, and the vibrational state of the excited molecule. They result from the light-induced coupling between the excited molecule, and bound and scattering states of the interaction between two metastable atoms. Their analysis leads to the determination of the scattering length a = (7.2 {+-} 0.6) ruling collisions between spin polarized atoms. The two photon photo-association spectra show evidence of the production of polarized, long-range {sup 4}He{sub 2}(2{sup 3}S{sub 1}-2{sup 3}S{sub 1}) molecules. They are said to be exotic as they are made of two metastable atoms, each one carrying a enough energy to ionize the other. The corresponding lineshapes are calculated and decomposed in sums and products of Breit-Wigner and Fano profiles associated to one and two photon processes. The experimental spectra are fit, and an intrinsic lifetime {tau} = (1.4 {+-} 0.3) {mu}s is deduced. It is checked whether this lifetime could be limited by spin-dipole induced Penning autoionization. This interpretation requires that there is a quasi-bound state close to the dissociation threshold in the singlet interaction potential between metastable helium atoms for the theory to match the experiment. (author)

Maintained expression of the planar cell polarity molecule Vangl2 and reformation of hair cell orientation in the regenerating inner ear.

Science.gov (United States)

Warchol, Mark E; Montcouquiol, Mireille

2010-09-01

The avian inner ear possesses a remarkable ability to regenerate sensory hair cells after ototoxic injury. Regenerated hair cells possess phenotypes and innervation that are similar to those found in the undamaged ear, but little is known about the signaling pathways that guide hair cell differentiation during the regenerative process. The aim of the present study was to examine the factors that specify the orientation of hair cell stereocilia bundles during regeneration. Using organ cultures of the chick utricle, we show that hair cells are properly oriented after having regenerated entirely in vitro and that orientation is not affected by surgical removal of the striolar reversal zone. These results suggest that the orientation of regenerating stereocilia is not guided by the release of a diffusible morphogen from the striolar reversal zone but is specified locally within the regenerating sensory organ. In order to determine the nature of the reorientation cues, we examined the expression patterns of the core planar cell polarity molecule Vangl2 in the normal and regenerating utricle. We found that Vangl2 is asymmetrically expressed on cells within the sensory epithelium and that this expression pattern is maintained after ototoxic injury and throughout regeneration. Notably, treatment with a small molecule inhibitor of c-Jun-N-terminal kinase disrupted the orientation of regenerated hair cells. Both of these results are consistent with the hypothesis that noncanonical Wnt signaling guides hair cell orientation during regeneration.

The effect of polarized light on the organization of collagen secreted by fibroblasts.

Science.gov (United States)

Akilbekova, Dana; Boddupalli, Anuraag; Bratlie, Kaitlin M

2018-04-01

Recent studies have demonstrated the beneficial effect of low-power lasers and polarized light on wound healing, inflammation, and the treatment of rheumatologic and neurologic disorders. The overall effect of laser irradiation treatment is still controversial due to the lack of studies on the biochemical mechanisms and the optimal parameters for the incident light that should be chosen for particular applications. Here, we study how NIH/3T3 fibroblasts respond to irradiation with linearly polarized light at different polarization angles. In particular, we examined vascular endothelial growth factor (VEGF) secretion, differentiation to myofibroblasts, and collagen organization in response to 800 nm polarized light at 0°, 45°, 90°, and 135° with a power density of 40 mW/cm 2 for 6 min every day for 6 days. Additional experiments were conducted in which the polarization angle of the incident was changed every day to induce an isotropic distribution of collagen. The data presented here shows that polarized light can upregulate VEGF production, myofibroblast differentiation, and induce different collagen organization in response to different polarization angles of the incident beam. These results are encouraging and demonstrate possible methods for controlling cell response through the polarization angle of the laser light, which has potential for the treatment of wounds.

Spin selection at organic spinterface by anchoring group

Energy Technology Data Exchange (ETDEWEB)

Zhang, Zhao; Qiu, Shuai; Miao, Yuan-yuan; Ren, Jun-feng; Wang, Chuan-kui [School of Physics and Electronics, Shandong Normal University, Jinan 250014 (China); Hu, Gui-chao, E-mail: hgc@sdnu.edu.cn [School of Physics and Electronics, Shandong Normal University, Jinan 250014 (China); Institute of Theoretical Physics, Technische Universität Dresden, 01062 Dresden (Germany)

2017-07-01

Highlights: • The sign of interfacial spin polarization can be selected by using different anchoring groups. • A sp{sup 3}-d or sp-d hybridization may occur and induce spin polarization when the anchoring group changes. • Interfacial spin polarization depends on both the type of the outer orbital of the anchoring atom as well as its energy. - Abstract: Control of organic interfacial spin polarization is crucial in organic spintronics. Based on ab initio theory, here we proposed a spin selection at organic interface via anchoring group by adsorbing an organic molecule onto Ni(111) surface. The results demonstrate that either a positive or negative interfacial spin polarization may be obtained by choosing different anchoring groups. The orbital analysis via the projected density of states shows that the interfacial spin polarization is sensitive to the hybridization of the outer orbital of the anchoring atom as well as its energy relative to the d orbital of the ferromagnetic atom. The work indicates a feasible way to realize spin selection at the organic spinterface by anchoring group.

Nonadiabatic dynamics of electron injection into organic molecules

International Nuclear Information System (INIS)

Zhu Li-Ping; Qiu Yu; Tong Guo-Ping

2012-01-01

We numerically investigate the injection process of electrons from metal electrodes to one-dimensional organic molecules by combining the extended Su—Schrieffer—Heeger (SSH) model with a nonadiabatic dynamics method. It is found that a match between the Fermi level of electrodes and the highest occupied molecular orbital (HOMO) or the lowest unoccupied molecular orbital (LUMO) of organic molecules can be greatly affected by the length of the organic chains, which has a great impact on electron injection. The correlation between oligomers and electrodes is found to open more efficient channels for electron injection as compared with that in polymer/electrode structures. For oligomer/electrode structures, we show that the Schottky barrier essentially does not affect the electron injection as the electrode work function is smaller than a critical value. This means that the Schottky barrier is pinned for a small work-function electrode. For polymer/electrode structures, we find that it is possible for the Fermi level of electrodes to be pinned to the polaronic level. The condition under which the Fermi level of electrodes exceeds the polaronic level of polymers is shown to not always lead to spontaneous electron transfer from electrodes to polymers. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

Evidence of thermal transport anisotropy in stable glasses of vapor deposited organic molecules

Science.gov (United States)

Ràfols-Ribé, Joan; Dettori, Riccardo; Ferrando-Villalba, Pablo; Gonzalez-Silveira, Marta; Abad, Llibertat; Lopeandía, Aitor F.; Colombo, Luciano; Rodríguez-Viejo, Javier

2018-03-01

Vapor deposited organic glasses are currently in use in many optoelectronic devices. Their operation temperature is limited by the glass transition temperature of the organic layers and thermal management strategies become increasingly important to improve the lifetime of the device. Here we report the unusual finding that molecular orientation heavily influences heat flow propagation in glassy films of small molecule organic semiconductors. The thermal conductivity of vapor deposited thin-film semiconductor glasses is anisotropic and controlled by the deposition temperature. We compare our data with extensive molecular dynamics simulations to disentangle the role of density and molecular orientation on heat propagation. Simulations do support the view that thermal transport along the backbone of the organic molecule is strongly preferred with respect to the perpendicular direction. This is due to the anisotropy of the molecular interaction strength that limits the transport of atomic vibrations. This approach could be used in future developments to implement small molecule glassy films in thermoelectric or other organic electronic devices.

Study of the electronic properties of organic molecules within a metal-molecule-metal junction

International Nuclear Information System (INIS)

Lambert, Mathieu

2003-01-01

This ph-D thesis is about electronic transport through organic molecules inserted in a metal molecule-metal junction. We describe first a simple process to prepare sub-3 nm gaps by controllable breakage (under an electrical stress) of gold wires lithographed on a SiO 2 Si substrate at low temperature (4.2 K). We show that the involved mechanism is thermally assisted electromigration. We observe that current-voltage (I-V) characteristics of resulting electrodes are stable up to ∼5 V. which gives access to the well-known Fowler-Nordheim regime in the I-V, allowing an accurate characterisation of the gap size. The average gap is found lo be between 1.5 nm in width and 2.5 eV in height. Molecules and nanoparticles have then been inserted in the junction in the case of nanoparticles for example. The resulting IV clearly shows the suppression of electrical current at low bias known as Coulomb blockade. Characteristic of single-electron tunnelling through nanometer-sized structures, finally we fabricated a single-electron tunneling device based on Au nanoparticles connected to the electrodes via terthiophene (T3) molecule. We use the silicon substrate, separated from the planar structure by a silicon oxide of 200 nm, as an electrostatic gate and observed clear current modulation with possible signature of the transport properties of the terthiophene molecules. (author) [fr

On the origin of organic molecules in interstellar space and some of its consequences

International Nuclear Information System (INIS)

Johansson, K.L.V.

1981-01-01

The possible sources of complex organic molecules observed in the interstellar space are discussed. It is found that a leakage from lifebearing planets cannot possibly explain the observed amounts of complex organic molecules. They are probably formed in interstellar clouds, either free in space or on the surface of grains. This opens the possibility that planets (also the earth) moving through such clouds may have collected appreciable amounts of complex organic molecules. It would therefore be feasible to perform experiments like the Urey-Miller's, starting with a considerably more complex mixture than the traditional one. (Auth.)

Small organic molecule based flow battery

Science.gov (United States)

Huskinson, Brian; Marshak, Michael; Aziz, Michael J.; Gordon, Roy G.; Betley, Theodore A.; Aspuru-Guzik, Alan; Er, Suleyman; Suh, Changwon

2018-05-08

The invention provides an electrochemical cell based on a new chemistry for a flow battery for large scale, e.g., gridscale, electrical energy storage. Electrical energy is stored chemically at an electrochemical electrode by the protonation of small organic molecules called quinones to hydroquinones. The proton is provided by a complementary electrochemical reaction at the other electrode. These reactions are reversed to deliver electrical energy. A flow battery based on this concept can operate as a closed system. The flow battery architecture has scaling advantages over solid electrode batteries for large scale energy storage.

Investigation of the atmospheric behavior of dicarboxylic acids and other polar organic aerosol constituents

International Nuclear Information System (INIS)

Limbeck, A.

2001-05-01

The objective of the present work was to improve the present knowledge about the atmospheric behavior of polar organic aerosol constituents with special respect to dicarboxylic acids. To enable the simultaneous determination of polar organic compounds in atmospheric samples like aerosol or precipitation samples (atmospheric hydrometeors) a new GCMS method was developed. Almost all classes of oxygenated organic compounds like mono- and dicarboxylic acids, aldehydes, alcohols or polar aromatic compounds like phthalates could be determined with only one sample preparation scheme. The separation into two classes of organic compounds with different polarity was performed using solid phase extraction. After a sample pre-treatment of the derived fractions, including esterification of the acids and extraction with cyclohexane, the samples were analyzed with a GCMS system. The new method was applied for the analysis of simultaneously collected interstitial aerosol and cloud water samples from a continental background site in Central Europe (Sonnblick Observatory, located at 3106-m elevation in the Austrian Alps). In all samples a large variety of mono- and dicarboxylic acids were identified and quantified, together with some aldehydes, alcohols and aromatic compounds. Using the obtained data set, for the first time in-cloud scavenging efficiencies for dicarboxylic acids, monocarboxylic acids, and other polar organic compounds were calculated. The results were compared to sulfate, which exhibited an average scavenging efficiency of 0.94. In the last part of the present work the results from laboratory and field investigations conducted with the intention to yield an improved sampling technique for the correction of the positive sampling artifact (adsorption of gas phase organics onto the filter substrate) were presented. (author)

Spin-Polarized Hybridization at the interface between different 8-hydroxyquinolates and the Cr(001) surface

Science.gov (United States)

Wang, Jingying; Deloach, Andrew; Dougherty, Daniel B.; Dougherty Lab Team

Organic materials attract a lot of attention due to their promising applications in spintronic devices. It is realized that spin-polarized metal/organic interfacial hybridization plays an important role to improve efficiency of organic spintronic devices. Hybridized interfacial states help to increase spin injection at the interface. Here we report spin-resolved STM measurements of single tris(8-hydroxyquinolinato) aluminum molecules adsorbed on the antiferromagnetic Cr(001). Our observations show a spin-polarized interface state between Alq3 and Cr(001). Tris(8-hydroxyquinolinato) chromium has also been studied and compared with Alq3, which exhibits different spin-polarized hybridization with the Cr(001) surface state than Alq3. We attribute the differences to different character of molecular orbitals in the two different quinolates.

Structural and electronic properties of single molecules and organic layers on surfaces

NARCIS (Netherlands)

Sotthewes, Kai

2016-01-01

Single molecules and organic layers on well-defined solid surfaces have attracted tremendous attention owing to their interesting physical and chemical properties. The ultimate utility of single molecules or self-assembled monolayers (SAMs) for potential applications is critically dependent on the

Exotic helium molecules; Molecules exotiques d'helium

Energy Technology Data Exchange (ETDEWEB)

Portier, M

2007-12-15

We study the photo-association of an ultracold cloud of magnetically trapped helium atoms: pairs of colliding atoms interact with one or two laser fields to produce a purely long range {sup 4}He{sub 2}(2{sup 3}S{sub 1}-2{sup 3}P{sub 0}) molecule, or a {sup 4}He{sub 2}(2{sup 3}S{sub 1}-2{sup 3}S{sub 1}) long range molecule. Light shifts in one photon photo-association spectra are measured and studied as a function of the laser polarization and intensity, and the vibrational state of the excited molecule. They result from the light-induced coupling between the excited molecule, and bound and scattering states of the interaction between two metastable atoms. Their analysis leads to the determination of the scattering length a = (7.2 {+-} 0.6) ruling collisions between spin polarized atoms. The two photon photo-association spectra show evidence of the production of polarized, long-range {sup 4}He{sub 2}(2{sup 3}S{sub 1}-2{sup 3}S{sub 1}) molecules. They are said to be exotic as they are made of two metastable atoms, each one carrying a enough energy to ionize the other. The corresponding lineshapes are calculated and decomposed in sums and products of Breit-Wigner and Fano profiles associated to one and two photon processes. The experimental spectra are fit, and an intrinsic lifetime {tau} = (1.4 {+-} 0.3) {mu}s is deduced. It is checked whether this lifetime could be limited by spin-dipole induced Penning autoionization. This interpretation requires that there is a quasi-bound state close to the dissociation threshold in the singlet interaction potential between metastable helium atoms for the theory to match the experiment. (author)

Surface functionalization of aluminosilicate nanotubes with organic molecules

Directory of Open Access Journals (Sweden)

Wei Ma

2012-02-01

Full Text Available The surface functionalization of inorganic nanostructures is an effective approach for enriching the potential applications of existing nanomaterials. Inorganic nanotubes attract great research interest due to their one-dimensional structure and reactive surfaces. In this review paper, recent developments in surface functionalization of an aluminosilicate nanotube, “imogolite”, are introduced. The functionalization processes are based on the robust affinity between phosphate groups of organic molecules and the aluminol (AlOH surface of imogolite nanotubes. An aqueous modification process employing a water soluble ammonium salt of alkyl phosphate led to chemisorption of molecules on imogolite at the nanotube level. Polymer-chain-grafted imogolite nanotubes were prepared through surface-initiated polymerization. In addition, the assembly of conjugated molecules, 2-(5’’-hexyl-2,2’:5’,2’’-terthiophen-5-ylethylphosphonic acid (HT3P and 2-(5’’-hexyl-2,2’:5’,2’’-terthiophen-5-ylethylphosphonic acid 1,1-dioxide (HT3OP, on the imogolite nanotube surface was achieved by introducing a phosphonic acid group to the corresponding molecules. The optical and photophysical properties of these conjugated-molecule-decorated imogolite nanotubes were characterized. Moreover, poly(3-hexylthiophene (P3HT chains were further hybridized with HT3P modified imogolite to form a nanofiber hybrid.

Effect of Polarization on the Mobility of C₆₀

DEFF Research Database (Denmark)

Volpi, Riccardo; Kottravel, Sathish; Nørby, Morten Steen

2016-01-01

We present a study of mobility field and temperature dependence for C60 with Kinetic Monte Carlo simulations. We propose a new scheme to take into account polarization effects in organic materials through atomic induced dipoles on nearby molecules. This leads to an energy correction for the singl...

Triton - Stratospheric molecules and organic sediments

Science.gov (United States)

Thompson, W. Reid; Singh, Sushil K.; Khare, B. N.; Sagan, Carl

1989-01-01

Continuous-flow plasma discharge techniques show production rates of hydrocarbons and nitriles in N2 + CH4 atmospheres appropriate to the stratosphere of Titan, and indicate that a simple eddy diffusion model together with the observed electron flux quantitatively matches the Voyager IRIS observations for all the hydrocarbons, except for the simplest ones. Charged particle chemistry is very important in Triton's stratosphere. In the more CH4-rich case of Titan, many hydrocarbons and nitriles are produced in high yield. If N2 is present, the CH4 fraction is low, but hydrocarbons and nitriles are produced in fair yield, abundances of HCN and C2H2 in Triton's stratosphere exceed 10 to the 19th molecules/sq cm per sec, and NCCN, C3H4, and other species are predicted to be present. These molecules may be detected by IRIS if the stratosphere is as warm as expected. Both organic haze and condensed gases will provide a substantial UV and visible opacity in Triton's atmosphere.

Separation of polar compounds using a flexible metal-organic framework

NARCIS (Netherlands)

Motkuri, R.K.; Thallapally, P.K.; Annapureddy, H.V.R.; Dang, L.X.; Krishna, R.; Nune, S.K.; Fernandez, C.A.; Liu, J.; McGrail, B.P.

2015-01-01

A flexible metal-organic framework constructed from a flexible linker is shown to possess the capability of separating mixtures of polar compounds (propanol isomers) by exploiting the differences in the saturation capacities of the constituents. Transient breakthrough simulations show that these

Quantum interference experiments with complex organic molecules

International Nuclear Information System (INIS)

Eibenberger, S. I.

2015-01-01

Matter-wave interference with complex particles is a thriving field in experimental quantum physics. The quest for testing the quantum superposition principle with highly complex molecules has motivated the development of the Kapitza-Dirac-Talbot-Lau interferometer (KDTLI). This interferometer has enabled quantum interference with large organic molecules in an unprecedented mass regime. In this doctoral thesis I describe quantum superposition experiments which we were able to successfully realize with molecules of masses beyond 10 000 amu and consisting of more than 800 atoms. The typical de Broglie wavelengths of all particles in this thesis are in the order of 0.3-5 pm. This is significantly smaller than any molecular extension (nanometers) or the delocalization length in our interferometer (hundreds of nanometers). Many vibrational and rotational states are populated since the molecules are thermally highly excited (300-1000 K). And yet, high-contrast quantum interference patterns could be observed. The visibility and position of these matter-wave interference patterns is highly sensitive to external perturbations. This sensitivity has opened the path to extensive studies of the influence of internal molecular properties on the coherence of their associated matter waves. In addition, it enables a new approach to quantum-assisted metrology. Quantum interference imprints a high-contrast nano-structured density pattern onto the molecular beam which allows us to resolve tiny shifts and dephasing of the molecular beam. I describe how KDTL interferometry can be used to investigate a number of different molecular properties. We have studied vibrationally-induced conformational changes of floppy molecules and permanent electric dipole moments using matter-wave deflectometry in an external electric field. We have developed a new method for optical absorption spectroscopy which uses the recoil of the molecules upon absorption of individual photons. This allows us to

Polarization: A must for fusion

Directory of Open Access Journals (Sweden)

Didelez J.-P.

2013-11-01

Full Text Available The complete polarization of DT fuel would increase the fusion reactivity by 50% in magnetic as well as in inertial confinements. The persistence of polarization in a fusion process could be tested, using a terawatt laser hitting a polarized HD target. The polarized deuterons heated in the plasma induced by the laser can fuse producing a 3He and a neutron in the final state. The angular distribution of the emitted neutrons and the change in the corresponding total Cross Section (CS can sign the polarization persistence. The polarization of solid H2, D2 or T2 Hydrogen isotopes is very difficult. However, it has been possible to polarize HD, a hetero-molecular form of Hydrogen, by static polarization, at very low temperature and very high field. The radioactivity of DT molecules forbids there high polarization by the static method, therefore one has to develop the Dynamic Nuclear Polarization (DNP by RF transitions. The DNP of HD has been investigated in the past. The magnetic properties of HD and DT molecules are very similar, it is therefore expected that any polarization result obtained with HD could be extrapolated to DT.

Theoretical study on magnetism induced by H vacancy in isolated Alq3 and Gaq3 molecules

Science.gov (United States)

Ju, Lin; Xu, Tongshuai; Zhang, Yongjia; Sun, Li

2017-10-01

The magnetism induced by H vacancy in isolated Alq3 and Gaq3 molecules has been studied based on density functional theory. The isolated stoichiometric Alq3 and Gaq3 molecules are non-magnetic. With an H vacancy, both Alq3 and Gaq3 molecules could show magnetism, which are mainly due to the polarization of the C 2p electrons and the magnetic moments are mainly distributed at most nearby C atoms of H vacancies. This is because the unpaired electron on the C atom appears, when the H atom nearby is removed. Six cases of the H vacancy introduced in the Alq3 and Gaq3 molecules are considered, respectively. By comparing the relative defect formation energy, the V H3 vacancy is most likely to appear in the two kinds of molecules. In addition, for the ground state configuration of isolated Alq3 and Gaq3 molecules with two H vacancies, the energy of the ferromagnetic state is lower than that of the antiferromagnetic state, which means that the ferromagnetic state is stable. The ferromagnetic mechanism can be explained by the Heisenberg direct exchange interaction between two the polarized C atoms. Our work opens a new way to synthesize organic magnetic materials and perfects the theory of organic ferromagnetism by introducing the d 0 ferromagnetism.

Characterization of Interstellar Organic Molecules

International Nuclear Information System (INIS)

Gencaga, Deniz; Knuth, Kevin H.; Carbon, Duane F.

2008-01-01

Understanding the origins of life has been one of the greatest dreams throughout history. It is now known that star-forming regions contain complex organic molecules, known as Polycyclic Aromatic Hydrocarbons (PAHs), each of which has particular infrared spectral characteristics. By understanding which PAH species are found in specific star-forming regions, we can better understand the biochemistry that takes place in interstellar clouds. Identifying and classifying PAHs is not an easy task: we can only observe a single superposition of PAH spectra at any given astrophysical site, with the PAH species perhaps numbering in the hundreds or even thousands. This is a challenging source separation problem since we have only one observation composed of numerous mixed sources. However, it is made easier with the help of a library of hundreds of PAH spectra. In order to separate PAH molecules from their mixture, we need to identify the specific species and their unique concentrations that would provide the given mixture. We develop a Bayesian approach for this problem where sources are separated from their mixture by Metropolis Hastings algorithm. Separated PAH concentrations are provided with their error bars, illustrating the uncertainties involved in the estimation process. The approach is demonstrated on synthetic spectral mixtures using spectral resolutions from the Infrared Space Observatory (ISO). Performance of the method is tested for different noise levels.

Third phase formation in organic solutions in the extraction of mono-acids by tertiary trialcoyl-amines diluted in very slightly polar organic solvents

International Nuclear Information System (INIS)

Robaglia, Michele

1973-01-01

The phenomena of third phase formation which can occur during the extraction of an acid with a tertiary amine diluted in a low polarity diluent are studied. In the first part a system including water (TnOA - C 6 H 12 - HCl - H 2 O) is compared with an anhydrous system (TnOA - C 6 H 12 - HCl - N 2 ). There are two kinds of gaps. One during amine salification, another one during the extraction of excess acid. The important part of the water content of the organic phase is demonstrated. The presence of water enhances the gaps. The polar water molecules are dissolved inside the tri-octylamine salt micelles. The heavy phase is formed by aggregates, the light phase represents the solubility of the non soluble species in the medium. In the second part are studied the influence of some parameters (like nature of diluent, acid, amine and temperature) on the gaps formation and on the extraction of excess acid and water. In every cases the part played by water remains the same. Finally some comparisons are made between tertiary systems and binary systems which formed them. The binary systems were studied by the mean of crystallization curves. (author) [fr

Resolving the Framework Position of Organic Structure-Directing Agents in Hierarchical Zeolites via Polarized Stimulated Raman Scattering.

Science.gov (United States)

Fleury, Guillaume; Steele, Julian A; Gerber, Iann C; Jolibois, F; Puech, P; Muraoka, Koki; Keoh, Sye Hoe; Chaikittisilp, Watcharop; Okubo, Tatsuya; Roeffaers, Maarten B J

2018-04-05

The direct synthesis of hierarchically intergrown silicalite-1 can be achieved using a specific diquaternary ammonium agent. However, the location of these molecules in the zeolite framework, which is critical to understand the formation of the material, remains unclear. Where traditional characterization tools have previously failed, herein we use polarized stimulated Raman scattering (SRS) microscopy to resolve molecular organization inside few-micron-sized crystals. Through a combination of experiment and first-principles calculations, our investigation reveals the preferential location of the templating agent inside the linear pores of the MFI framework. Besides illustrating the attractiveness of SRS microscopy in the field of material science to study and spatially resolve local molecular distribution as well as orientation, these results can be exploited in the design of new templating agents for the preparation of hierarchical zeolites.

Adsorption of organic molecules may explain growth of newly nucleated clusters and new particle formation

Science.gov (United States)

Wang, Jian; Wexler, Anthony S.

2013-05-01

New particle formation consists of formation of thermodynamically stable clusters from trace gas molecules (homogeneous nucleation) followed by growth of these clusters to a detectable size. Because of the large coagulation rate of clusters smaller than 3 nm with the preexisting aerosol population, for new particle formation to take place, these clusters need to grow sufficiently fast to escape removal by coagulation. Previous studies have indicated that condensation of low-volatility organic vapor may play an important role in the initial growth of the clusters. However, due to the relatively high vapor pressure and partial molar volume of even highly oxidized organic compounds, the strong Kelvin effect may prevent typical ambient organics from condensing on these small clusters. Earlier studies did not consider that adsorption of organic molecules on the cluster surface, due to the intermolecular forces between the organic molecule and cluster, may occur and substantially alter the growth process under sub-saturated conditions. Using the Brunauer-Emmett-Teller (BET) isotherm, we show that the adsorption of organic molecules onto the surface of clusters may significantly reduce the saturation ratio required for condensation of organics to occur, and therefore may provide a physico-chemical explanation for the enhanced initial growth by condensation of organics despite the strong Kelvin effect.

Integrated organic electronic based optochemical sensors using polarization filters

International Nuclear Information System (INIS)

Kraker, Elke; Haase, Anja; Lamprecht, Bernhard; Jakopic, Georg; Konrad, Christian; Koestler, Stefan

2008-01-01

A compact, integrated photoluminescence based oxygen and pH sensor, utilizing an organic light emitting device (OLED) as the light source and an organic photodiode (OPD) as the detection unit, is described. The main challenge in such an integrated sensor is the suppression of the excitation light at the detector, which is typically by many orders of magnitude higher in intensity than the emitted fluorescence. In our approach, we refrain from utilizing edge filters which require narrow band excitation sources and dyes with an adequate large Stokes shift. We rather developed an integrated sensor concept relying on two polarizers to separate the emission and excitation light. One polarizer is located right after the OLED, while the other one, oriented at 90 deg. to the first, is placed in front of the OPD. The main advantage of this solution is that any combination of excitation and emission light is acceptable, even if the two signals overlap spectrally. This is especially important for the use of OLEDs as the excitation sources, as these devices typically exhibit a broad spectral emission

Genetic control of organ shape and tissue polarity.

Directory of Open Access Journals (Sweden)

Amelia A Green

2010-11-01

Full Text Available The mechanisms by which genes control organ shape are poorly understood. In principle, genes may control shape by modifying local rates and/or orientations of deformation. Distinguishing between these possibilities has been difficult because of interactions between patterns, orientations, and mechanical constraints during growth. Here we show how a combination of growth analysis, molecular genetics, and modelling can be used to dissect the factors contributing to shape. Using the Snapdragon (Antirrhinum flower as an example, we show how shape development reflects local rates and orientations of tissue growth that vary spatially and temporally to form a dynamic growth field. This growth field is under the control of several dorsoventral genes that influence flower shape. The action of these genes can be modelled by assuming they modulate specified growth rates parallel or perpendicular to local orientations, established by a few key organisers of tissue polarity. Models in which dorsoventral genes only influence specified growth rates do not fully account for the observed growth fields and shapes. However, the data can be readily explained by a model in which dorsoventral genes also modify organisers of tissue polarity. In particular, genetic control of tissue polarity organisers at ventral petal junctions and distal boundaries allows both the shape and growth field of the flower to be accounted for in wild type and mutants. The results suggest that genetic control of tissue polarity organisers has played a key role in the development and evolution of shape.

Stability of organic molecules against shocks in the young Solar nebula

NARCIS (Netherlands)

Kamp, Inga; Milosavljevic, Milica; Stempels, E

2009-01-01

One of the fundamental astrobiology questions is how life has formed in our Solar System. In this context the formation and stability of abiotic organic molecules such as CH(4), formic acid and amino acids, is important for understanding how organic material has formed and survived shocks and

A Self-Perpetuating Catalyst for the Production of Complex Organic Molecules in Protostellar Nebulae

Science.gov (United States)

Nuth, Joseph A.; Johnson, N. M.

2010-01-01

The formation of abundant carbonaceous material in meteorites is a long standing problem and an important factor in the debate on the potential for the origin of life in other stellar systems. Many mechanisms may contribute to the total organic content in protostellar nebulae, ranging from organics formed via ion-molecule and atom-molecule reactions in the cold dark clouds from which such nebulae collapse, to similar ion-molecule and atom-molecule reactions in the dark regions of the nebula far from the proto star, to gas phase reactions in sub-nebulae around growing giant planets and in the nebulae themselves. The Fischer-Tropsch-type (FTT) catalytic reduction of CO by hydrogen was once the preferred model for production of organic materials in the primitive solar nebula. The Haber-Bosch catalytic reduction of N2 by hydrogen was thought to produce the reduced nitrogen found in meteorites. However, the clean iron metal surfaces that catalyze these reactions are easily poisoned via reaction with any number of molecules, including the very same complex organics that they produce and both reactions work more efficiently in the hot regions of the nebula. We have demonstrated that many grain surfaces can catalyze both FTT and HB-type reactions, including amorphous iron and magnesium silicates, pure silica smokes as well as several minerals. Although none work as well as pure iron grains, and all produce a wide range of organic products rather than just pure methane, these materials are not truly catalysts.

Organization of central synapses by adhesion molecules.

Science.gov (United States)

Tallafuss, Alexandra; Constable, John R L; Washbourne, Philip

2010-07-01

Synapses are the primary means for transmitting information from one neuron to the next. They are formed during the development of the nervous system, and the formation of appropriate synapses is crucial for the establishment of neuronal circuits that underlie behavior and cognition. Understanding how synapses form and are maintained will allow us to address developmental disorders such as autism, mental retardation and possibly also psychological disorders. A number of biochemical and proteomic studies have revealed a diverse and vast assortment of molecules that are present at the synapse. It is now important to untangle this large array of proteins and determine how it assembles into a functioning unit. Here we focus on recent reports describing how synaptic cell adhesion molecules interact with and organize the presynaptic and postsynaptic specializations of both excitatory and inhibitory central synapses. © The Authors (2010). Journal Compilation © Federation of European Neuroscience Societies and Blackwell Publishing Ltd.

UP-scaling of inverted small molecule based organic solar cells

DEFF Research Database (Denmark)

Patil, Bhushan Ramesh; Madsen, Morten

Organic solar cells (OSC), in spite of being a promising technology, still face challenges regarding large-scale fabrication. Although efficiencies of up to 12 % has been reached for small molecule OSC, their performance, both in terms of device efficiency and stability, is significantly reduced...... during up-scaling processes. The work presented here is focused on an approach towards up-scaling of small molecule based OSC with inverted device configuration. Bilayer OSC from Tetraphenyldibenzoperiflanthene (DBP) and Fullerenes (C70), as electron donor and acceptor respectively, with cell area...

Organic molecules based on dithienyl-2,1,3-benzothiadiazole as new donor materials for solution-processed organic photovoltaic cells

Energy Technology Data Exchange (ETDEWEB)

Wu, Zhonglian; Fan, Benhu; Ouyang, Jianyong [Department of Materials Science and Engineering, National University of Singapore, Singapore 117574 (Singapore); Xue, Feng [Department of Chemistry, National University of Singapore, Singapore 117573 (Singapore); Adachi, Chihaya [Center for Future Chemistry, Kyushu University, 744 Motooka, Nishi, Fukuoka 819-0395 (Japan)

2010-12-15

Polymers based on dithienyl-2,1,3-benzothiadiazole (TBT) have received strong attention as the donor materials of polymer photovoltaic cells (PVs), since they can have a low band gap. But soluble small organic molecules based on TBT have been rarely studied. This paper reports the synthesis of two small organic molecules based on TBT and their application as the donor materials of solution-processed bulk heterojunction organic photovoltaic cells (OPVs). These compounds were soluble in common organic solvents, such as chloroform, chlorobenzene and tetrahydrofuran. They have band gaps comparable to poly(3-hexylthiophene) (P3HT) and lower HOMO and LUMO (HOMO: highest occupied molecular orbital, LUMO: lowest unoccupied molecular orbital) levels than P3HT. These molecules and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) were used as the donors and acceptor to fabricate bulk heterojunction OPVs through solution processing. After optimization of the experimental conditions, power conversion efficiency (PCE) of 0.66% was achieved on the solution-processed OPVs under AM 1.5G, 100 mW cm{sup -2} illumination. (author)

Inducing elliptically polarized high-order harmonics from aligned molecules with linearly polarized femtosecond pulses

DEFF Research Database (Denmark)

Etches, Adam; Madsen, Christian Bruun; Madsen, Lars Bojer

2010-01-01

A recent paper reported elliptically polarized high-order harmonics from aligned N2 using a linearly polarized driving field [X. Zhou et al., Phys. Rev. Lett. 102, 073902 (2009)]. This observation cannot be explained in the standard treatment of the Lewenstein model and has been ascribed to many...

Structural Design Principle of Small-Molecule Organic Semiconductors for Metal-Free, Visible-Light-Promoted Photocatalysis.

Science.gov (United States)

Wang, Lei; Huang, Wei; Li, Run; Gehrig, Dominik; Blom, Paul W M; Landfester, Katharina; Zhang, Kai A I

2016-08-08

Herein, we report on the structural design principle of small-molecule organic semiconductors as metal-free, pure organic and visible light-active photocatalysts. Two series of electron-donor and acceptor-type organic semiconductor molecules were synthesized to meet crucial requirements, such as 1) absorption range in the visible region, 2) sufficient photoredox potential, and 3) long lifetime of photogenerated excitons. The photocatalytic activity was demonstrated in the intermolecular C-H functionalization of electron-rich heteroaromates with malonate derivatives. A mechanistic study of the light-induced electron transport between the organic photocatalyst, substrate, and the sacrificial agent are described. With their tunable absorption range and defined energy-band structure, the small-molecule organic semiconductors could offer a new class of metal-free and visible light-active photocatalysts for chemical reactions. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Stability of polarization in organic ferroelectric metal-insulator-semiconductor (MIS) structures

Energy Technology Data Exchange (ETDEWEB)

Kalbitz, Rene; Fruebing, Peter; Gerhard, Reimund [Department of Physics and Astronomy, University of Potsdam, Karl-Liebknecht-Strasse 24-25, 14476, Potsdam (Germany); Taylor, Martin [School of Electronic Engineering, Bangor University, Dean Street, Bangor Gwynedd, LL57 1UT (United Kingdom)

2011-07-01

Ferroelectric field effect transistors (FeFETs) offer the prospect of an organic-based memory device. Since the charge transport in such devices is confined to the interface between the insulator and the semiconductor, the focus of the present study was on the investigation of this region. Capacitance-voltage (C-V) measurements of all-organic MIS devices with poly(vinylidenefluoride- trifluoroethylene) (P(VDF-TrFE)) as gate insulator and poly(3-hexylthiophene)(P3HT) as semiconductor were carried out. When the structure was driven into depletion, a positive flat-band voltage shift was observed arising from the change in polarization state of the ferroelectric insulator. When driven into accumulation, the polarization was reversed. It is shown that both polarization states are stable. However, negative charge trapped at the interface during the depletion cycle masks the negative shift in flat-band voltage expected during the sweep to accumulation voltages. Measurements on P(VDF-TrFE)/P3HT based FeFETs yield further evidence for fixed charges at the interface. Output characteristics suggest the injection of negative charges into the interface region when a depletion voltage is applied between source and gate contact.

Exotic helium molecules

International Nuclear Information System (INIS)

Portier, M.

2007-12-01

We study the photo-association of an ultracold cloud of magnetically trapped helium atoms: pairs of colliding atoms interact with one or two laser fields to produce a purely long range 4 He 2 (2 3 S 1 -2 3 P 0 ) molecule, or a 4 He 2 (2 3 S 1 -2 3 S 1 ) long range molecule. Light shifts in one photon photo-association spectra are measured and studied as a function of the laser polarization and intensity, and the vibrational state of the excited molecule. They result from the light-induced coupling between the excited molecule, and bound and scattering states of the interaction between two metastable atoms. Their analysis leads to the determination of the scattering length a = (7.2 ± 0.6) ruling collisions between spin polarized atoms. The two photon photo-association spectra show evidence of the production of polarized, long-range 4 He 2 (2 3 S 1 -2 3 S 1 ) molecules. They are said to be exotic as they are made of two metastable atoms, each one carrying a enough energy to ionize the other. The corresponding lineshapes are calculated and decomposed in sums and products of Breit-Wigner and Fano profiles associated to one and two photon processes. The experimental spectra are fit, and an intrinsic lifetime τ = (1.4 ± 0.3) μs is deduced. It is checked whether this lifetime could be limited by spin-dipole induced Penning autoionization. This interpretation requires that there is a quasi-bound state close to the dissociation threshold in the singlet interaction potential between metastable helium atoms for the theory to match the experiment. (author)

Anchoring of organic molecules to a metal surface: HtBDC on Cu(110)

DEFF Research Database (Denmark)

Schunack, M.; Petersen, L.; Kuhnle, A.

2001-01-01

The interaction of largish molecules with metal surfaces has been studied by combining the imaging and manipulation capabilities of the scanning tunneling microscope (STM). At the atomic scale, the STM results directly reveal that the adsorption of a largish organic molecule can induce...

Organic Materials in the Undergraduate Laboratory: Microscale Synthesis and Investigation of a Donor-Acceptor Molecule

Science.gov (United States)

Pappenfus, Ted M.; Schliep, Karl B.; Dissanayake, Anudaththa; Ludden, Trevor; Nieto-Ortega, Belen; Lopez Navarrete, Juan T.; Ruiz Delgado, M. Carmen; Casado, Juan

2012-01-01

A series of experiments for undergraduate courses (e.g., organic, physical) have been developed in the area of small molecule organic materials. These experiments focus on understanding the electronic and redox properties of a donor-acceptor molecule that is prepared in a convenient one-step microscale reaction. The resulting intensely colored…

Latest polarization and beam characterization results of the Orsay polarized electron source

International Nuclear Information System (INIS)

Arianer, J.; Cohen, S.; Essabaa, S.; Frascaria, R.; Zerhouni, O.

1995-01-01

The Orsay polarized electron source based on the chemi-ionization of aligned He(2 3 S 1 ) atoms and CO 2 molecules is briefly described. The latest results concerning electron polarization and beam emittance are presented. The present development status is also discussed. (K.A.)

The effect of organic contaminants on the spectral induced polarization response of porous media - mechanistic approach

Science.gov (United States)

Schwartz, N.; Huisman, J. A.; Furman, A.

2012-12-01

In recent years, there is a growing interest in using geophysical methods in general and spectral induced polarization (SIP) in particular as a tool to detect and monitor organic contaminants within the subsurface. The general idea of the SIP method is to inject alternating current through a soil volume and to measure the resultant potential in order to obtain the relevant soil electrical properties (e.g. complex impedance, complex conductivity/resistivity). Currently, a complete mechanistic understanding of the effect of organic contaminants on the SIP response of soil is still absent. In this work, we combine laboratory experiments with modeling to reveal the main processes affecting the SIP signature of soil contaminated with organic pollutant. In a first set of experiments, we investigate the effect of non-aqueous phase liquids (NAPL) on the complex conductivity of unsaturated porous media. Our results show that addition of NAPL to the porous media increases the real component of the soil electrical conductivity and decreases the polarization of the soil (imaginary component of the complex conductivity). Furthermore, addition of NAPL to the soil resulted in an increase of the electrical conductivity of the soil solution. Based on these results, we suggest that adsorption of NAPL to the soil surface, and exchange process between polar organic compounds in the NAPL and inorganic ions in the soil are the main processes affecting the SIP signature of the contaminated soil. To further support our hypothesis, the temporal change of the SIP signature of a soil as function of a single organic cation concentration was measured. In addition to the measurements of the soil electrical properties, we also measured the effect of the organic cation on the chemical composition of both the bulk and the surface of the soil. The results of those experiments again showed that the electrical conductivity of the soil increased with increasing contaminant concentration. In addition

Continuous centrifuge decelerator for polar molecules.

Science.gov (United States)

Chervenkov, S; Wu, X; Bayerl, J; Rohlfes, A; Gantner, T; Zeppenfeld, M; Rempe, G

2014-01-10

Producing large samples of slow molecules from thermal-velocity ensembles is a formidable challenge. Here we employ a centrifugal force to produce a continuous molecular beam with a high flux at near-zero velocities. We demonstrate deceleration of three electrically guided molecular species, CH3F, CF3H, and CF3CCH, with input velocities of up to 200  m s(-1) to obtain beams with velocities below 15  m s(-1) and intensities of several 10(9)  mm(-2) s(-1). The centrifuge decelerator is easy to operate and can, in principle, slow down any guidable particle. It has the potential to become a standard technique for continuous deceleration of molecules.

Functional fixedness and functional reduction as common sense reasonings in chemical equilibrium and in geometry and polarity of molecules

Science.gov (United States)

Furió, C.; Calatayud, M. L.; Bárcenas, S. L.; Padilla, O. M.

2000-09-01

Many of the learning difficulties in the specific domain of chemistry are found not only in the ideas already possessed by students but in the strategic and procedural knowledge that is characteristic of everyday thinking. These defects in procedural knowledge have been described as functional fixedness and functional reduction. This article assesses the procedural difficulties of students (grade 12 and first and third year of university) based on common sense reasoning in two areas of chemistry: chemical equilibrium and geometry and polarity of molecules. In the first area, the theme of external factors affecting equilibria (temperature and concentration change) was selected because the explanations given by the students could be analyzed easily. The existence of a functional fixedness where Le Chatelier's principle was almost exclusively applied by rote could be observed, with this being the cause of the incorrect responses given to the proposed items. Functional fixedness of the Lewis structure also led to an incorrect prediction of molecular geometry. When molecular geometry was correctly determined by the students, it seemed that other methodological or procedural difficulties appeared when the task was to determine molecular polarity. The students showed a tendency, in many cases, to reduce the factors affecting molecular polarity in two possible ways: (a) assuming that polarity depends only on shape (geometric functional reduction) or (b) assuming that molecular polarity depends only on the polarity of bonds (bonding functional reduction).

Trapping molecules in two and three dimensions

International Nuclear Information System (INIS)

Pinkse, PW.H.; Junglen, T.; Rieger, T.; Rangwala, S.A.; Windpassinger, P.; Rempe, G.

2005-01-01

Full text: Cold molecules offer a new testing ground for quantum-physical effects in nature. For example, producing slow beams of large molecules could push experiments studying the boundary between quantum interference and classical particles up towards ever heavier particles. Moreover, cold molecules, in particular YbF, seem an attractive way to narrow down the constraints on the value of the electron dipole moment and finally, quantum information processing using chains of cold polar molecules or vibrational states in molecules have been proposed. All these proposals rely on advanced production and trapping techniques, most of which are still under development. Therefore, novel production and trapping techniques for cold molecules could offer new possibilities not found in previous methods. Electric traps hold promise for deep trap potentials for neutral molecules. Recently we have demonstrated two-dimensional trapping of polar molecules in a four-wire guide using electrostatic and electrodynamic trapping techniques. Filled from a thermal effusive source, such a guide will deliver a beam of slow molecules, which is an ideal source for interferometry experiments with large molecules, for instance. Here we report about the extension of this work to three-dimensional trapping. Polar molecules with a positive Stark shift can be trapped in the minimum of an electrostatic field. We have successfully tested a large volume electrostatic trap for ND3 molecules. A special feature of this trap is that it can be loaded continuously from an electrostatic guide, at a temperature of a few hundred mK. (author)

In-situ Evaluation of Soil Organic Molecules: Functional Group Chemistry Aggregate Structures, Metal and Surface Complexation Using Soft X-Ray

International Nuclear Information System (INIS)

Myneni, Satish C.

2008-01-01

Organic molecules are common in all Earth surface environments, and their composition and chemistry play an important role in a variety of biogeochemical reactions, such as mineral weathering, nutrient cycling and the solubility and transport of contaminants. However, most of what we know about the chemistry of these molecules comes from spectroscopy and microscopy studies of organic molecules extracted from different natural systems using either inorganic or organic solvents. Although all these methods gave us clues about the composition of these molecules, their composition and structure change with the extraction and the type of ex-situ analysis, their true behavior is less well understood. The goal of this project is to develop synchrotron instrumentation for studying natural organics, and to apply these recently developed synchrotron X-ray spectroscopy and microscopy techniques for understanding the: (1) functional group composition of naturally occurring organic molecules; (2) macromolecular structures of organic molecules; and (3) the nature of interactions of organic molecules with mineral surfaces in different environmental conditions.

Effect of Polarization on the Mobility of C60: A Kinetic Monte Carlo Study.

Science.gov (United States)

Volpi, Riccardo; Kottravel, Sathish; Nørby, Morten Steen; Stafström, Sven; Linares, Mathieu

2016-02-09

We present a study of mobility field and temperature dependence for C60 with Kinetic Monte Carlo simulations. We propose a new scheme to take into account polarization effects in organic materials through atomic induced dipoles on nearby molecules. This leads to an energy correction for the single site energies and to an external reorganization happening after each hopping. The inclusion of polarization allows us to obtain a good agreement with experiments for both mobility field and temperature dependence.

Liquid Adsorption of Organic Compounds on Hematite α-Fe2O3 Using ReaxFF.

Science.gov (United States)

Chia, Chung-Lim; Avendaño, Carlos; Siperstein, Flor R; Filip, Sorin

2017-10-24

ReaxFF-based molecular dynamics simulations are used in this work to study the effect of the polarity of adsorbed molecules in the liquid phase on the structure and polarization of hematite (α-Fe 2 O 3 ). We compared the adsorption of organic molecules with different polarities on a rigid hematite surface and on a flexible and polarizable surface. We show that the displacements of surface atoms and surface polarization in a flexible hematite model are proportional to the adsorbed molecule's polarity. The increase in electrostatic interactions resulting from charge transfer in the outermost solid atoms in a flexible hematite model results in better-defined adsorbed layers that are less ordered than those obtained assuming a rigid solid. These results suggest that care must be taken when parametrizing empirical transferable force fields because the calculated charges on a solid slab in vacuum may not be representative of a real system, especially when the solid is in contact with a polar liquid.

Simultaneously 'pushing' and 'pulling' graphene oxide into low-polar solvents through a designed interface.

Science.gov (United States)

Liu, Zhen; Liu, Jingquan; Wang, Yichao; Razal, Joselito M; Francis, Paul S; Biggs, Mark J; Barrow, Colin J; Yang, Wenrong

2018-08-03

Dispersing graphene oxide (GO) in low-polar solvents can realize a perfect self-assembly with functional molecules and application in removal of organic impurities that only dissolve in low-polar solvents. The surface chemistry of GO plays an important role in its dispersity in these solvents. The direct transfer of hydrophilic GO into low-polar solvents, however, has remained an experimental challenge. In this study, we design an interface to transfer GO by simultaneously 'pushing and pulling' the nanosheets into low-polar solvents. Our approach is outstanding due to the ability to obtain monolayers of chemically reduced GO (CRGO) with designed surface properties in the organic phase. Using the transferred GO or CRGO dispersions, we have fabricated GO/fullerene nanocomposites and assessed the ability of CRGOs for dye adsorption. We hope our work can provide a universal approach for the phase transfer of other nanomaterials.

Nanocoating of titanium implant surfaces with organic molecules. Polysaccharides including glycosaminoglycans

DEFF Research Database (Denmark)

Gurzawska, Katarzyna Aleksandra; Svava, Rikke; Jørgensen, Niklas Rye

2012-01-01

Long-term stability of titanium implants are dependent on a variety of factors. Nanocoating with organic molecules is one of the method used to improve osseointegration. Nanoscale modification of titanium implants affects surface properties, such as hydrophilicity, biochemical bonding capacity...... and roughness. This influences cell behaviour on the surface such as adhesion, proliferation and differentiation of cells as well as the mineralization of the extracellular matrix at the implant surfaces. The aim of the present systematic review was to describe organic molecules used for surface nanocoating...... nanocoatings. The included in vivo studies, showed improvement of bone interface reactions measured as increased Bone-to-Implant Contact length and Bone Mineral Density adjacent to the polysaccharide coated surfaces. Based on existing literature, surface modification with polysaccharide and glycosaminoglycans...

Dynamic spin filtering at the Co/Alq3 interface mediated by weakly coupled second layer molecules

Science.gov (United States)

Droghetti, Andrea; Thielen, Philip; Rungger, Ivan; Haag, Norman; Großmann, Nicolas; Stöckl, Johannes; Stadtmüller, Benjamin; Aeschlimann, Martin; Sanvito, Stefano; Cinchetti, Mirko

2016-08-01

Spin filtering at organic-metal interfaces is often determined by the details of the interaction between the organic molecules and the inorganic magnets used as electrodes. Here we demonstrate a spin-filtering mechanism based on the dynamical spin relaxation of the long-living interface states formed by the magnet and weakly physisorbed molecules. We investigate the case of Alq3 on Co and, by combining two-photon photoemission experiments with electronic structure theory, show that the observed long-time spin-dependent electron dynamics is driven by molecules in the second organic layer. The interface states formed by physisorbed molecules are not spin-split, but acquire a spin-dependent lifetime, that is the result of dynamical spin-relaxation driven by the interaction with the Co substrate. Such spin-filtering mechanism has an important role in the injection of spin-polarized carriers across the interface and their successive hopping diffusion into successive molecular layers of molecular spintronics devices.

The Kinesin Adaptor Calsyntenin-1 Organizes Microtubule Polarity and Regulates Dynamics during Sensory Axon Arbor Development

Directory of Open Access Journals (Sweden)

Mary C. Halloran

2017-04-01

Full Text Available Axon growth and branching, and development of neuronal polarity are critically dependent on proper organization and dynamics of the microtubule (MT cytoskeleton. MTs must organize with correct polarity for delivery of diverse cargos to appropriate subcellular locations, yet the molecular mechanisms regulating MT polarity remain poorly understood. Moreover, how an actively branching axon reorganizes MTs to direct their plus ends distally at branch points is unknown. We used high-speed, in vivo imaging of polymerizing MT plus ends to characterize MT dynamics in developing sensory axon arbors in zebrafish embryos. We find that axonal MTs are highly dynamic throughout development, and that the peripheral and central axons of sensory neurons show differences in MT behaviors. Furthermore, we show that Calsyntenin-1 (Clstn-1, a kinesin adaptor required for sensory axon branching, also regulates MT polarity in developing axon arbors. In wild type neurons the vast majority of MTs are directed in the correct plus-end-distal orientation from early stages of development. Loss of Clstn-1 causes an increase in MTs polymerizing in the retrograde direction. These misoriented MTs most often are found near growth cones and branch points, suggesting Clstn-1 is particularly important for organizing MT polarity at these locations. Together, our results suggest that Clstn-1, in addition to regulating kinesin-mediated cargo transport, also organizes the underlying MT highway during axon arbor development.

Self-organized lattice of ordered quantum dot molecules

International Nuclear Information System (INIS)

Lippen, T. von; Noetzel, R.; Hamhuis, G.J.; Wolter, J.H.

2004-01-01

Ordered groups of InAs quantum dots (QDs), lateral QD molecules, are created by self-organized anisotropic strain engineering of a (In,Ga)As/GaAs superlattice (SL) template on GaAs (311)B in molecular-beam epitaxy. During stacking, the SL template self-organizes into a two-dimensionally ordered strain modulated network on a mesoscopic length scale. InAs QDs preferentially grow on top of the nodes of the network due to local strain recognition. The QDs form a lattice of separated groups of closely spaced ordered QDs whose number can be controlled by the GaAs separation layer thickness on top of the SL template. The QD groups exhibit excellent optical properties up to room temperature

Peculiarities of spin polarization inversion at a thiophene/cobalt interface

KAUST Repository

Wang, Xuhui

2013-03-20

We perform ab initio calculations to investigate the spin polarization at the interface between a thiophene molecule and cobalt substrate. We find that the reduced symmetry in the presence of a sulfur atom (in the thiophene molecule) leads to a strong spatial dependence of the spin polarization of the molecule. The two carbon atoms far from the sulfur acquire a polarization opposite to that of the substrate, while the carbon atoms bonded directly to sulfur possess the same polarization as the substrate. We determine the origin of this peculiar spin interface property as well as its impact on the spin transport.

C. elegans STRADalpha and SAD cooperatively regulate neuronal polarity and synaptic organization.

Science.gov (United States)

Kim, Joanne S M; Hung, Wesley; Narbonne, Patrick; Roy, Richard; Zhen, Mei

2010-01-01

Neurons are polarized cells with morphologically and functionally distinct axons and dendrites. The SAD kinases are crucial for establishing the axon-dendrite identity across species. Previous studies suggest that a tumour suppressor kinase, LKB1, in the presence of a pseudokinase, STRADalpha, initiates axonal differentiation and growth through activating the SAD kinases in vertebrate neurons. STRADalpha was implicated in the localization, stabilization and activation of LKB1 in various cell culture studies. Its in vivo functions, however, have not been examined. In our present study, we analyzed the neuronal phenotypes of the first loss-of-function mutants for STRADalpha and examined their genetic interactions with LKB1 and SAD in C. elegans. Unexpectedly, only the C. elegans STRADalpha, STRD-1, functions exclusively through the SAD kinase, SAD-1, to regulate neuronal polarity and synaptic organization. Moreover, STRD-1 tightly associates with SAD-1 to coordinate its synaptic localizations. By contrast, the C. elegans LKB1, PAR-4, also functions in an additional genetic pathway independently of SAD-1 and STRD-1 to regulate neuronal polarity. We propose that STRD-1 establishes neuronal polarity and organizes synaptic proteins in a complex with the SAD-1 kinase. Our findings suggest that instead of a single, linear genetic pathway, STRADalpha and LKB1 regulate neuronal development through multiple effectors that are shared in some cellular contexts but distinct in others.

Organic Semiconductor-Containing Supramolecules: Effect of Small Molecule Crystallization and Molecular Packing

KAUST Repository

Rancatore, Benjamin J.

2016-01-21

© 2016 American Chemical Society. Small molecules (SMs) with unique optical or electronic properties provide an opportunity to incorporate functionality into block copolymer (BCP)-based supramolecules. However, the assembly of supramolecules based on these highly crystalline molecules differs from their less crystalline counterparts. Here, two families of organic semiconductor SMs are investigated, where the composition of the crystalline core, the location (side- vs end-functionalization) of the alkyl solubilizing groups, and the constitution (branched vs linear) of the alkyl groups are varied. With these SMs, we present a systematic study of how the phase behavior of the SMs affects the overall assembly of these organic semiconductor-based supramolecules. The incorporation of SMs has a large effect on the interfacial curvature, the supramolecular periodicity, and the overall supramolecular morphology. The crystal packing of the SM within the supramolecule does not necessarily lead to the assembly of the comb block within the BCP microdomains, as is normally observed for alkyl-containing supramolecules. An unusual lamellar morphology with a wavy interface between the microdomains is observed due to changes in the packing structure of the small molecule within BCP microdomains. Since the supramolecular approach is modular and small molecules can be readily switched out, present studies provide useful guidance toward access supramolecular assemblies over several length scales using optically active and semiconducting small molecules.

Formation of tilted smectic-C liquid crystal phase in polar Gay-Berne molecules

International Nuclear Information System (INIS)

Saha, J.; Bose, T.R.; Ghosh, D.; Saha, M.

2005-01-01

We perform molecular dynamics simulation for a system of Gay-Berne molecules having two terminal dipole moments to generate tilted smectic-C liquid crystal phase. We investigate the effect of dipolar orientation with respect to the long molecular axis on phase behaviour. The study indicates that larger dipolar angle can give rise to greater tilt in molecular organization within a layer

Organohalogen concentrations and a gross and histologic assessment of multiple organ systems in East Greenland polar bears (Ursus maritimus)

DEFF Research Database (Denmark)

Sonne, C.

To investigate the relation between biological parameters, not earlier investigated in the polar bear, and organohalogen pollution in East Greenland polar bears, we initiated a sampling of adipose tissue, internal organs and skulls from more than 100 free-ranging polar bears killed by local...... in the adipose tissue and pathological changes in skulls and internal organs. Our results suggested a decrease in adipose tissue concentrations of organohalogens in East Greenland polar bears from 1990 to 1999-2001. Two of the biological effect parameters (FA and enlarged clitoris) did not indicate a link......, infectious agents, season and meaby chronic exposure to organohalogens. These result fill out an existing knowledge gap in potential effects of environmental, organic contaminants on fluctuating asymmetry, bone mineral density and functional anatomy (histology) in the polar bear. In addition, the results may...

EVAPORATION: a new vapour pressure estimation methodfor organic molecules including non-additivity and intramolecular interactions

Directory of Open Access Journals (Sweden)

S. Compernolle

2011-09-01

Full Text Available We present EVAPORATION (Estimation of VApour Pressure of ORganics, Accounting for Temperature, Intramolecular, and Non-additivity effects, a method to predict (subcooled liquid pure compound vapour pressure p⁰ of organic molecules that requires only molecular structure as input. The method is applicable to zero-, mono- and polyfunctional molecules. A simple formula to describe log₁₀p⁰(T is employed, that takes into account both a wide temperature dependence and the non-additivity of functional groups. In order to match the recent data on functionalised diacids an empirical modification to the method was introduced. Contributions due to carbon skeleton, functional groups, and intramolecular interaction between groups are included. Molecules typically originating from oxidation of biogenic molecules are within the scope of this method: aldehydes, ketones, alcohols, ethers, esters, nitrates, acids, peroxides, hydroperoxides, peroxy acyl nitrates and peracids. Therefore the method is especially suited to describe compounds forming secondary organic aerosol (SOA.

Luminescence stability of porous Si terminated by hydrophilic organic molecules

Science.gov (United States)

Matsumoto, Kimihisa; Kamiguchi, Masao; Kamiya, Kazuhide; Nomura, Takashi; Suzuki, Shinya

2016-02-01

The effects of the surface termination of a porous Si surface by propionic acid and by undecylenic acid on their hydrophilicity and luminescence stability were studied. In the measurements of the contact angle of water droplets on porous Si films, the hydrophilicity of porous Si is improved by the surface termination each types of organic molecule. The PL intensity of as-prepared porous Si decreased with increasing aging time in ambient air. As PL quenching involves PL blue shift and increasing Si-O bonds density, nonradiative recombination centers are formed in the surface oxide. After the hydrosilylation process of propionic acid and undecylenic acid, PL intensity decreased and became 30% that of as-prepared porous Si film. However, the PL intensity was stable and exceeded that of the as-prepared film after 1000 min of aging in the ambient air. The PL stabilities are contributed to the termination by organic molecules that inhibits surface oxidation.

Organic molecule fluorescence as an experimental test-bed for quantum jumps in thermodynamics.

Science.gov (United States)

Browne, Cormac; Farrow, Tristan; Dahlsten, Oscar C O; Taylor, Robert A; Vlatko, Vedral

2017-08-01

We demonstrate with an experiment how molecules are a natural test bed for probing fundamental quantum thermodynamics. Single-molecule spectroscopy has undergone transformative change in the past decade with the advent of techniques permitting individual molecules to be distinguished and probed. We demonstrate that the quantum Jarzynski equality for heat is satisfied in this set-up by considering the time-resolved emission spectrum of organic molecules as arising from quantum jumps between states. This relates the heat dissipated into the environment to the free energy difference between the initial and final state. We demonstrate also how utilizing the quantum Jarzynski equality allows for the detection of energy shifts within a molecule, beyond the relative shift.

EDITORIAL: Focus on Cold and Ultracold Molecules FOCUS ON COLD AND ULTRACOLD MOLECULES

Science.gov (United States)

Carr, Lincoln D.; Ye, Jun

2009-05-01

Cold and ultracold molecules are the next wave of ultracold physics, giving rise to an exciting array of scientific opportunities, including many body physics for novel quantum phase transitions, new states of matter, and quantum information processing. Precision tests of fundamental physical laws benefit from the existence of molecular internal structure with exquisite control. The study of novel collision and reaction dynamics will open a new chapter of quantum chemistry. Cold molecules bring together researchers from a variety of fields, including atomic, molecular, and optical physics, chemistry and chemical physics, quantum information science and quantum simulations, condensed matter physics, nuclear physics, and astrophysics, a truly remarkable synergy of scientific explorations. For the past decade there have been steady advances in direct cooling techniques, from buffer-gas cooling to cold molecular beams to electro- and magneto-molecular decelerators. These techniques have allowed a large variety of molecules to be cooled for pioneering studies. Recent amazing advances in experimental techniques combining the ultracold and the ultraprecise have furthermore brought molecules to the point of quantum degeneracy. These latter indirect cooling techniques magnetically associate atoms from a Bose-Einstein condensate and/or a quantum degenerate Fermi gas, transferring at 90% efficiency highly excited Fano-Feshbach molecules, which are on the order of 10 000 Bohr radii in size, to absolute ground state molecules just a few Bohr across. It was this latter advance, together with significant breakthroughs in internal state manipulations, which inspired us to coordinate this focus issue now, and is the reason why we say the next wave of ultracold physics has now arrived. Whether directly or indirectly cooled, heteronuclear polar molecules offer distinct new features in comparison to cold atoms, while sharing all of their advantages (purity, high coherence

Generating highly polarized nuclear spins in solution using dynamic nuclear polarization

DEFF Research Database (Denmark)

Wolber, J.; Ellner, F.; Fridlund, B.

2004-01-01

A method to generate strongly polarized nuclear spins in solution has been developed, using Dynamic Nuclear Polarization (DNP) at a temperature of 1.2K, and at a field of 3.354T, corresponding to an electron spin resonance frequency of 94GHz. Trityl radicals are used to directly polarize 13C...... and other low-γ nuclei. Subsequent to the DNP process, the solid sample is dissolved rapidly with a warm solvent to create a solution of molecules with highly polarized nuclear spins. Two main applications are proposed: high-resolution liquid state NMR with enhanced sensitivity, and the use...

A-π-D-π-A Electron-Donating Small Molecules for Solution-Processed Organic Solar Cells: A Review.

Science.gov (United States)

Wang, Zhen; Zhu, Lingyun; Shuai, Zhigang; Wei, Zhixiang

2017-11-01

Organic solar cells based on semiconducting polymers and small molecules have attracted considerable attention in the last two decades. Moreover, the power conversion efficiencies for solution-processed solar cells containing A-π-D-π-A-type small molecules and fullerenes have reached 11%. However, the method for designing high-performance, photovoltaic small molecules still remains unclear. In this review, recent studies on A-π-D-π-A electron-donating small molecules for organic solar cells are introduced. Moreover, the relationships between molecular properties and device performances are summarized, from which inspiration for the future design of high performance organic solar cells may be obtained. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Reversible multi-electron redox chemistry of π-conjugated N-containing heteroaromatic molecule-based organic cathodes

Science.gov (United States)

Peng, Chengxin; Ning, Guo-Hong; Su, Jie; Zhong, Guiming; Tang, Wei; Tian, Bingbing; Su, Chenliang; Yu, Dingyi; Zu, Lianhai; Yang, Jinhu; Ng, Man-Fai; Hu, Yong-Sheng; Yang, Yong; Armand, Michel; Loh, Kian Ping

2017-07-01

Even though organic molecules with well-designed functional groups can be programmed to have high electron density per unit mass, their poor electrical conductivity and low cycle stability limit their applications in batteries. Here we report a facile synthesis of π-conjugated quinoxaline-based heteroaromatic molecules (3Q) by condensation of cyclic carbonyl molecules with o-phenylenediamine. 3Q features a number of electron-deficient pyrazine sites, where multiple redox reactions take place. When hybridized with graphene and coupled with an ether-based electrolyte, an organic cathode based on 3Q molecules displays a discharge capacity of 395 mAh g-1 at 400 mA g-1 (1C) in the voltage range of 1.2-3.9 V and a nearly 70% capacity retention after 10,000 cycles at 8 A g-1. It also exhibits a capacity of 222 mAh g-1 at 20C, which corresponds to 60% of the initial specific capacity. Our results offer evidence that heteroaromatic molecules with multiple redox sites are promising in developing high-energy-density, long-cycle-life organic rechargeable batteries.

Mechanochemical synthesis of small organic molecules

Directory of Open Access Journals (Sweden)

Tapas Kumar Achar

2017-09-01

Full Text Available With the growing interest in renewable energy and global warming, it is important to minimize the usage of hazardous chemicals in both academic and industrial research, elimination of waste, and possibly recycle them to obtain better results in greener fashion. The studies under the area of mechanochemistry which cover the grinding chemistry to ball milling, sonication, etc. are certainly of interest to the researchers working on the development of green methodologies. In this review, a collection of examples on recent developments in organic bond formation reactions like carbon–carbon (C–C, carbon–nitrogen (C–N, carbon–oxygen (C–O, carbon–halogen (C–X, etc. is documented. Mechanochemical syntheses of heterocyclic rings, multicomponent reactions and organometallic molecules including their catalytic applications are also highlighted.

Conduction mechanism in assemblies of metal nanoparticles linked by organic molecules

International Nuclear Information System (INIS)

Mueller, K.-H.; Herrmann, J.; Raguse, B.; Baxter, G.; Reda, T.

2002-01-01

Full text: We have investigated theoretically and experimentally electron transport through thin films of gold nanoparticles which are linked by alkanedithiol molecules of different chain lengths. We find that conduction between neighbouring nanoparticles takes place by electron tunnelling along weakly conducting organic linker molecules. Using a tight binding model for the alkanedithiol molecules to describe the tunnelling process we predict the conductivity to decrease exponentially with the length of the molecules. During tunnelling the electron has to overcome a charging energy due to the electron-hole interaction between tunnelling electrons and the corresponding holes left behind on the donor nanoparticle. Experimentally we find that large applied voltages cause nonlinear I-V characteristics and that the temperature dependence of the conductivity does not show Arrhenius behaviour but instead is of the form exp[-(E o /kT) 1/2 ]. Using percolation theory for a network of metal nanoparticles separated by barriers we show that strong disorder caused by variations in nanoparticle size and linker length as well as randomly trapped electric charges on the linker molecules can well explain our experimental data

Electrocatalytic hydrogenation of organic molecules on conductive new catalytic material

Energy Technology Data Exchange (ETDEWEB)

Tountian, D. [Louis Pasteur Univ., Strasbourg (France). Laboratoire d' Electrochimie et de Chimie Physique du Corps Solide; Sherbrooke Univ., Sherbrooke, PQ (Canada). Dept. de Chimie, Centre de Recherche en Electrochimie et Electrocatalyse; Brisach-Wittmeyer, A.; Menard, H. [Sherbrooke Univ., Sherbrooke, PQ (Canada). Dept. de Chimie, Centre de Recherche en Electrochimie et Electrocatalyse; Nkeng, P.; Poillerat, G. [Louis Pasteur Univ., Strasbourg (France). Laboratoire d' Electrochimie et de Chimie Physique du Corps Solide

2008-07-01

Electrocatalytic hydrogenation (ECH) of organic molecules is a process where chemisorbed hydrogen is produced by electroreduction of water which reacts with the species in bulk. Greater emphasis is being placed on improving the nature of the building material of the electrodes in order to increase ECH efficiency. The effectiveness of the ECH is known to be linked to the nature of electrode materials used and their adsorption properties. This work presented the effect of conductive support material on ECH. The conductive catalysts were obtained from tin dioxide which is chemically stable. Palladium was the catalytic metal used in this study. The production of chemisorbed hydrogen was shown to depend on the quantity of metallic nanoaggregates in electrical contact with the reticulated vitreous carbon use as electrode. The conductive support, F-doped tin dioxide, was obtained by the sol-gel method. The electrocatalysts were characterized by different methods as resistivity measurements, linear sweep voltammetry, XRD, SEM, TGA/DSC, and FTIR analysis. The effects of temperature and time of calcination were also investigated. The study showed that the F-doped SnO2 electrocatalyst appeared to increase the rate of phenol electrohydrogenation. It was concluded that the improved electrocatalytic activity of Pd/F-doped SnO2 can be attributed to the simultaneous polarization of all the metallic Pd nanoaggregates present on the surface as well as in the pores of the matrix by contact with RVC. This results in a better production of chemisorbed atomic hydrogen with a large number of adlienation points. 9 refs., 3 figs.

Room-temperature spin-polarized organic light-emitting diodes with a single ferromagnetic electrode

Energy Technology Data Exchange (ETDEWEB)

Ding, Baofu, E-mail: b.ding@ecu.edu.au; Alameh, Kamal, E-mail: k.alameh@ecu.edu.au [Electron Science Research Institute, Edith Cowan University, 270 Joondalup Drive, Joondalup WA 6027 Australia (Australia); Song, Qunliang [Institute for Clean Energy and Advanced Materials, Southwest University, Chongqing 400715 (China)

2014-05-19

In this paper, we demonstrate the concept of a room-temperature spin-polarized organic light-emitting diode (Spin-OLED) structure based on (i) the deposition of an ultra-thin p-type organic buffer layer on the surface of the ferromagnetic electrode of the Spin-OLED and (ii) the use of oxygen plasma treatment to modify the surface of that electrode. Experimental results demonstrate that the brightness of the developed Spin-OLED can be increased by 110% and that a magneto-electroluminescence of 12% can be attained for a 150 mT in-plane magnetic field, at room temperature. This is attributed to enhanced hole and room-temperature spin-polarized injection from the ferromagnetic electrode, respectively.

Single-molecule fluorescence polarization study of conformational change in archaeal group II chaperonin.

Directory of Open Access Journals (Sweden)

Ryo Iizuka

Full Text Available Group II chaperonins found in archaea and in eukaryotic cytosol mediate protein folding without a GroES-like cofactor. The function of the cofactor is substituted by the helical protrusion at the tip of the apical domain, which forms a built-in lid on the central cavity. Although many studies on the change in lid conformation coupled to the binding and hydrolysis of nucleotides have been conducted, the molecular mechanism of lid closure remains poorly understood. Here, we performed a single-molecule polarization modulation to probe the rotation of the helical protrusion of a chaperonin from a hyperthermophilic archaeum, Thermococcus sp. strain KS-1. We detected approximately 35° rotation of the helical protrusion immediately after photorelease of ATP. The result suggests that the conformational change from the open lid to the closed lid state is responsible for the approximately 35° rotation of the helical protrusion.

Phase-coherent electron transport through metallic atomic-sized contacts and organic molecules

Energy Technology Data Exchange (ETDEWEB)

Pauly, F.

2007-02-02

This work is concerned with the theoretical description of systems at the nanoscale, in particular the electric current through atomic-sized metallic contacts and organic molecules. In the first part, the characteristic peak structure in conductance histograms of different metals is analyzed within a tight-binding model. In the second part, an ab-initio method for quantum transport is developed and applied to single-atom and single-molecule contacts. (orig.)

Laser-induced desorption of organic molecules from front- and back-irradiated metal foils

International Nuclear Information System (INIS)

Zinovev, Alexander V.; Veryovkin, Igor V.; Pellin, Michael J.

2009-01-01

Laser-Induced Acoustic Desorption (LIAD) from thin metal foils is a promising technique for gentle and efficient volatilization of intact organic molecules from surfaces of solid substrates. Using the Single Photon Ionization (SPI) method combined with time-of-flight mass-spectrometry (TOF MS), desorbed flux in LIAD was examined and compared to that from direct laser desorption (LD). Molecules of various organic dyes were used in experiments. Translational velocities of the desorbed intact molecules did not depend on the desorbing laser intensity, which implies the presence of more sophisticated mechanism of energy transfer than the direct mechanical or thermal coupling between the laser pulse and the adsorbed molecules. The results of our experiments indicate that the LIAD phenomenon cannot be described in terms of a simple mechanical shake-off nor the direct laser desorption. Rather, they suggest that multi-step energy transfer processes are involved. Possible qualitative mechanism of LIAD that are based on formation of non-equilibrium energy states in the adsorbate-substrate system are proposed and discussed.

Hydrogen transfer reactions of interstellar Complex Organic Molecules

Science.gov (United States)

Álvarez-Barcia, S.; Russ, P.; Kästner, J.; Lamberts, T.

2018-06-01

Radical recombination has been proposed to lead to the formation of complex organic molecules (COMs) in CO-rich ices in the early stages of star formation. These COMs can then undergo hydrogen addition and abstraction reactions leading to a higher or lower degree of saturation. Here, we have studied 14 hydrogen transfer reactions for the molecules glyoxal, glycoaldehyde, ethylene glycol, and methylformate and an additional three reactions where CHnO fragments are involved. Over-the-barrier reactions are possible only if tunneling is invoked in the description at low temperature. Therefore the rate constants for the studied reactions are calculated using instanton theory that takes quantum effects into account inherently. The reactions were characterized in the gas phase, but this is expected to yield meaningful results for CO-rich ices due to the minimal alteration of reaction landscapes by the CO molecules. We found that rate constants should not be extrapolated based on the height of the barrier alone, since the shape of the barrier plays an increasingly larger role at decreasing temperature. It is neither possible to predict rate constants based only on considering the type of reaction, the specific reactants and functional groups play a crucial role. Within a single molecule, though, hydrogen abstraction from an aldehyde group seems to be always faster than hydrogen addition to the same carbon atom. Reactions that involve heavy-atom tunneling, e.g., breaking or forming a C-C or C-O bond, have rate constants that are much lower than those where H transfer is involved.

Magnesium Sulfate as a Key Mineral for the Detection of Organic Molecules on Mars Using Pyrolysis

Science.gov (United States)

Francois, P.; Szopa, C.; Buch, A.; Coll, P.; McAdam, A. C.; Mahaffy, P. R.; Freissinet, C.; Glavin, D. P.; Navarro-Gonzalez, R.; Cabane, M.

2016-01-01

Pyrolysis of soil or rock samples is the preferred preparation technique used on Mars to search for organic molecules up today. During pyrolysis, oxichlorines present in the soil of Mars release oxidant species that alter the organic molecules potentially contained in the samples collected by the space probes.This process can explain the difficulty experienced by in situ exploration probes to detect organic materials in Mars soil samples until recently. Within a few months, the Curiosity rover should reach and analyze for the first time soils rich in sulfates which could induce a different behavior of the organics during the pyrolysis compared with the types of soils analyzed up today. For this reason, we systematically studied the pyrolysis of organic molecules trapped in magnesium sulfate, in the presence or absence of calcium perchlorate. Our results show that organics trapped in magnesium sulfate can undergo some oxidation and sulfuration during the pyrolysis. But these sulfates are also shown to protect organics trapped inside the crystal lattice and/or present in fluid inclusions from the oxidation induced by the decomposition of calcium perchlorate and probably other oxychlorine phases currently detected on Mars. Trapped organics may also be protected from degradation processes induced by other minerals present in the sample, at least until these organics are released from the pyrolyzed sulfate mineral (700C in our experiment). Hence, we suggest magnesium sulfate as one of the minerals to target in priority for the search of organic molecules by the Curiosity and ExoMars 2018 rovers.

Calibration and use of the polar organic chemical integrative sampler--a critical review.

Science.gov (United States)

Harman, Christopher; Allan, Ian John; Vermeirssen, Etiënne L M

2012-12-01

The implementation of strict environmental quality standards for polar organic priority pollutants poses a challenge for monitoring programs. The polar organic chemical integrative sampler (POCIS) may help to address the challenge of measuring low and fluctuating trace concentrations of such organic contaminants, offering significant advantages over traditional sampling. In the present review, the authors evaluate POCIS calibration methods and factors affecting sampling rates together with reported environmental applications. Over 300 compounds have been shown to accumulate in POCIS, including pesticides, pharmaceuticals, hormones, and industrial chemicals. Polar organic chemical integrative sampler extracts have been used for both chemical and biological analyses. Several different calibration methods have been described, which makes it difficult to directly compare sampling rates. In addition, despite the fact that some attempts to correlate sampling rates with the properties of target compounds such as log K(OW) have been met with varying success, an overall model that can predict uptake is lacking. Furthermore, temperature, water flow rates, salinity, pH, and fouling have all been shown to affect uptake; however, there is currently no robust method available for adjusting for these differences. Overall, POCIS has been applied to a wide range of sampling environments and scenarios and has been proven to be a useful screening tool. However, based on the existing literature, a more mechanistic approach is required to increase understanding and thus improve the quantitative nature of the measurements. Copyright © 2012 SETAC.

Influence of thermocleavable functionality on organic field-effect transistor performance of small molecules

Science.gov (United States)

Mahale, Rajashree Y.; Dharmapurikar, Satej S.; Chini, Mrinmoy Kumar; Venugopalan, Vijay

2017-06-01

Diketopyrrolopyrrole based donor-acceptor-donor conjugated small molecules using ethylene dioxythiophene as a donor was synthesized. Electron deficient diketopyrrolopyrrole unit was substituted with thermocleavable (tert-butyl acetate) side chains. The thermal treatment of the molecules at 160 °C eliminated the tert-butyl ester group results in the formation of corresponding acid. Optical and theoretical studies revealed that the molecules adopted a change in molecular arrangement after thermolysis. The conjugated small molecules possessed p-channel charge transport characteristics in organic field effect transistors. The charge carrier mobility was increased after thermolysis of tert-butyl ester group to 5.07 × 10-5 cm2/V s.

Quantum transport through organic molecules

International Nuclear Information System (INIS)

Maiti, Santanu K.

2007-01-01

We investigate the electronic transport for the model of benzene-1, 4-dithiolate (BDT) molecule and some other geometric models of benzene molecule attached with two semi-infinite metallic electrodes by the use of Green's function technique. An analytic approach for the electronic transport through the molecular bridges is presented, based on the tight-binding model. Transport of electrons in such molecular bridges is strongly affected by the geometry of the molecules and their coupling strength with the electrodes. Conductance (g) shows resonance peaks associated with the molecular energy eigenstates. In the weak molecule-to-electrodes coupling limit current (I) passing through the molecules shows staircase-like behavior with sharp steps, while, it varies quite continuously in the limit of strong molecular coupling with the applied bias voltage (V). In presence of the transverse magnetic field conductance gives oscillatory behavior with flux φ, threaded by the molecular ring, showing φ 0 ( = ch/e) flux-quantum periodicity. Though conductance changes with the application of transverse magnetic field, but the current-voltage characteristics remain same in presence of this magnetic field for these molecular bridge systems

Sugar-Based Polyamides: Self-Organization in Strong Polar Organic Solvents.

Science.gov (United States)

Rosu, Cornelia; Russo, Paul S; Daly, William H; Cueto, Rafael; Pople, John A; Laine, Roger A; Negulescu, Ioan I

2015-09-14

Periodic patterns resembling spirals were observed to form spontaneously upon unassisted cooling of d-glucaric acid- and d-galactaric acid-based polyamide solutions in N-methyl-N-morpholine oxide (NMMO) monohydrate. Similar observations were made in d-galactaric acid-based polyamide/ionic liquid (IL) solutions. The morphologies were investigated by optical, polarized light and confocal microscopy assays to reveal pattern details. Differential scanning calorimetry was used to monitor solution thermal behavior. Small- and wide-angle X-ray scattering data reflected the complex and heterogeneous nature of the self-organized patterns. Factors such as concentration and temperature were found to influence spiral dimensions and geometry. The distance between rings followed a first-order exponential decay as a function of polymer concentration. Fourier-Transform Infrared Microspectroscopy analysis of spirals pointed to H-bonding between the solvent and the pendant hydroxyl groups of the glucose units from the polymer backbone. Tests on self-organization into spirals of ketal-protected d-galactaric acid polyamides in NMMO monohydrate confirmed the importance of the monosaccharide's pendant free hydroxyl groups on the formation of these patterns. Rheology performed on d-galactaric-based polyamides at high concentration in NMMO monohydrate solution revealed the optimum conditions necessary to process these materials as fibers by spinning. The self-organization of these sugar-based polyamides mimics certain biological materials.

Distilling two-center-interference information during tunneling of aligned molecules with orthogonally polarized two-color laser fields

Science.gov (United States)

Gao, F.; Chen, Y. J.; Xin, G. G.; Liu, J.; Fu, L. B.

2017-12-01

When electrons tunnel through a barrier formed by the strong laser field and the two-center potential of a diatomic molecule, a double-slit-like interference can occur. However, this interference effect can not be probed directly right now, as it is strongly coupled with other dynamical processes during tunneling. Here, we show numerically and analytically that orthogonally polarized two-color (OTC) laser fields are capable of resolving the interference effect in tunneling, while leaving clear footprints of this effect in photoelectron momentum distributions. Moreover, this effect can be manipulated by changing the relative field strength of OTC fields.

Photo- and radiation-chemical stability of molecules. Reactions of monomolecular hydrogen atom splitting off

International Nuclear Information System (INIS)

Plotnikov, V.G.; Ovchinnikov, A.A.

1978-01-01

In the review of works published up to 1978 one of the main problems of radiation chemistry is discussed, namely the relationship between the structure of organic molecules and their resistance to the effect of ionizing radiation. Theoretical aspects of this problem are considered for reactions of monomolecular hydrogen atom splitting off. It is shown that the radical yield in low-temperature radiation-chemical experiments is connected with the position of lower triplet states of molecules, ionization potentials, polarity of medium and the energy of C-H bonds in cation radicals

Permeability of uncharged organic molecules in reverse osmosis desalination membranes.

Science.gov (United States)

Dražević, Emil; Košutić, Krešimir; Svalina, Marin; Catalano, Jacopo

2017-06-01

Reverse osmosis (RO) membranes are primarily designed for removal of salts i.e. for desalination of brackish and seawater, but they have also found applications in removal of organic molecules. While it is clear that steric exclusion is the dominant removal mechanism, the fundamental explanation for how and why the separation occurs remains elusive. Until recently there was no strong microscopic evidences elucidating the structure of the active polyamide layers of RO membranes, and thus they have been conceived as "black boxes"; or as an array of straight capillaries with a distribution of radii; or as polymers with a small amount of polymer free domains. The knowledge of diffusion and sorption coefficients is a prerequisite for understanding the intrinsic permeability of any organic solute in any polymer. At the same time, it is technically challenging to accurately measure these two fundamental parameters in very thin (20-300 nm) water-swollen active layers. In this work we have measured partition and diffusion coefficients and RO permeabilities of ten organic solutes in water-swollen active layers of two types of RO membranes, low (SWC4+) and high flux (XLE). We deduced from our results and recent microscopic studies that the solute flux of organic molecules in polyamide layer of RO membranes occurs in two domains, dense polymer (the key barrier layer) and the water filled domains. Copyright © 2017 Elsevier Ltd. All rights reserved.

Solution processable organic polymers and small molecules for bulk-heterojunction solar cells: A review

International Nuclear Information System (INIS)

Sharma, G. D.

2011-01-01

Solution processed bulk heterojunction (BHJ) organic solar cells (OSCs) have gained wide interest in past few years and are established as one of the leading next generation photovoltaic technologies for low cost power production. Power conversion efficiencies up to 6% and 6.5% have been reported in the literature for single layer and tandem solar cells, respectively using conjugated polymers. A recent record efficiency about 8.13% with active area of 1.13 cm 2 has been reported. However Solution processable small molecules have been widely applied for photovoltaic (PV) devices in recent years because they show strong absorption properties, and they can be easily purified and deposited onto flexible substrates at low cost. Introducing different donor and acceptor groups to construct donor--acceptor (D--A) structure small molecules has proved to be an efficient way to improve the properties of organic solar cells (OSCs). The power conversion efficiency about 4.4 % has been reported for OSCs based on the small molecules. This review deals with the recent progress of solution processable D--A structure small molecules and discusses the key factors affecting the properties of OSCs based on D--A structure small molecules: sunlight absorption, charge transport and the energy level of the molecules.

The Role of the Clathrin Adaptor AP-1: Polarized Sorting and Beyond

Directory of Open Access Journals (Sweden)

Fubito Nakatsu

2014-11-01

Full Text Available The selective transport of proteins or lipids by vesicular transport is a fundamental process supporting cellular physiology. The budding process involves cargo sorting and vesicle formation at the donor membrane and constitutes an important process in vesicular transport. This process is particularly important for the polarized sorting in epithelial cells, in which the cargo molecules need to be selectively sorted and transported to two distinct destinations, the apical or basolateral plasma membrane. Adaptor protein (AP-1, a member of the AP complex family, which includes the ubiquitously expressed AP-1A and the epithelium-specific AP-1B, regulates polarized sorting at the trans-Golgi network and/or at the recycling endosomes. A growing body of evidence, especially from studies using model organisms and animals, demonstrates that the AP-1-mediated polarized sorting supports the development and physiology of multi-cellular units as functional organs and tissues (e.g., cell fate determination, inflammation and gut immune homeostasis. Furthermore, a possible involvement of AP-1B in the pathogenesis of human diseases, such as Crohn’s disease and cancer, is now becoming evident. These data highlight the significant contribution of AP-1 complexes to the physiology of multicellular organisms, as master regulators of polarized sorting in epithelial cells.

Strategies for monitoring the emerging polar organic contaminants in water with emphasis on integrative passive sampling.

Science.gov (United States)

Söderström, Hanna; Lindberg, Richard H; Fick, Jerker

2009-01-16

Although polar organic contaminants (POCs) such as pharmaceuticals are considered as some of today's most emerging contaminants few of them are regulated or included in on-going monitoring programs. However, the growing concern among the public and researchers together with the new legislature within the European Union, the registration, evaluation and authorisation of chemicals (REACH) system will increase the future need of simple, low cost strategies for monitoring and risk assessment of POCs in aquatic environments. In this article, we overview the advantages and shortcomings of traditional and novel sampling techniques available for monitoring the emerging POCs in water. The benefits and drawbacks of using active and biological sampling were discussed and the principles of organic passive samplers (PS) presented. A detailed overview of type of polar organic PS available, and their classes of target compounds and field of applications were given, and the considerations involved in using them such as environmental effects and quality control were discussed. The usefulness of biological sampling of POCs in water was found to be limited. Polar organic PS was considered to be the only available, but nevertheless, an efficient alternative to active water sampling due to its simplicity, low cost, no need of power supply or maintenance, and the ability of collecting time-integrative samples with one sample collection. However, the polar organic PS need to be further developed before they can be used as standard in water quality monitoring programs.

Organization of extracting molecules of the diamide type: link with the extracting properties?

International Nuclear Information System (INIS)

Meridiano, Y.

2009-02-01

The aim of these studies is to establish a link between the different organizations of diamide extractants (used in the DIAMEX process) and their extracting properties. The effects of the key parameters leading the liquid-liquid extraction (concentration of extractant, nature of solute, activity of the aqueous phase, nature of the diluent and temperature) are studied: 1) at the supramolecular scale, with the characterization of the extractant organizations by vapor-pressure osmometry (VPO) and small angle neutron and X-ray scattering (SANS/SAXS) experiments; 2) at the molecular scale, with the quantification of the extracted solutes (water, nitric acid, metal nitrate) and the determination of extracted complexes stoichiometries by electro-spray mass spectrometry (ESI-MS) experiments. The DMDOHEMA molecule acts as a classical surfactant and forms aggregates of the reverse micelle type. Taking into account the established supramolecular diagrams, a quantitative link between the extractants structures and their extracting properties has been brought to light. To model the europium nitrate extraction, two approaches have been developed: - an approach based on mass action laws. Extractions equilibria have been proposed taking into account the supramolecular speciation; - an innovative approach considering the extracted ions as adsorbed on a specific surface of the extractant molecule which depends on the extractant organization state. The ion extraction can be considered as a sum of isotherms corresponding to the different states of organization. This approach allows to compare the extraction efficiency of an extracting molecule as a function of its organization state. (author)

Ordered microporous layered lanthanide 1,3,5-benzenetriphosphonates pillared with cationic organic molecules.

Science.gov (United States)

Araki, Takahiro; Kondo, Atsushi; Maeda, Kazuyuki

2015-04-13

Novel isomorphous pillared-layer-type crystalline lanthanide 1,3,5-benzenetriphosphonates were prepared with bpy and dbo as organic pillars (LnBP-bpy and LnBP-dbo; Ln: Ce, Pr, and Nd). Ab initio crystal structure solution using synchrotron X-ray powder diffraction data revealed that the organic pillars do not exist as neutral coordinating ligands but as cationic molecules. Especially the LnBP-dbo phases have ordered interlayer space filled with water molecules between the dbo pillars, and the interlayer water is successfully removed by heating under vacuum with slightly distorted but basically retained pillared layer structures. Microporosity of the materials is confirmed by adsorption of nitrogen, carbon dioxide, and hydrogen gases. Such microporous layered metal phosphonates pillared with cationic molecules should be unprecedented and should offer new strategies to design ordered microporous materials. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

The tritium labelling of organic molecules by heterogeneous catalytic exchange

International Nuclear Information System (INIS)

Angoso, M.; Kaiser, F.

1977-01-01

The influence of the temperature at 65degC and 120degC on the labelling of three organic molecules with tritium was studied. The compounds were: benzoic acid, diphenyl glioxal and 2,3-tetramethylene-4-phenylthien-7-oxodiacetin. The method employed was the heterogeneous catalytic exchange between tritiaded water and the organic compound. The purification was made by thin-layer chromatography and the concentration, purity and specific activity of the products were determined by counting and ultraviolet techniques. The thermal stability and the radiolitic effects on labelled benzoic acid were also considered. (author) [es

Light-emission from in-situ grown organic nanostructures

DEFF Research Database (Denmark)

Oliveira Hansen, Roana Melina de; Kjelstrup-Hansen, Jakob; Rubahn, Horst-Günter

2011-01-01

Organic crystalline nanofibers made from phenylene-based molecules exhibit a wide range of extraordinary optical properties such as intense, anisotropic and polarized luminescence that can be stimulated either optically or electrically, waveguiding and random lasing. For lighting and display...... of morphological characterization and demonstrate how appropriate biasing with an AC gate voltage enables electroluminescence from these in-situ grown organic nanostructures....

Organic spintronics

International Nuclear Information System (INIS)

Naber, W J M; Faez, S; Wiel, W G van der

2007-01-01

We review the emerging field of organic spintronics, where organic materials are applied as a medium to transport and control spin-polarized signals. The contacts for injecting and detecting spins are formed by ferromagnetic metals, oxides, or inorganic semiconductors. First, the basic concepts of spintronics and organic electronics are addressed, and phenomena which are in particular relevant for organic spintronics are highlighted. Experiments using different organic materials, including carbon nanotubes, organic thin films, self-assembled monolayers and single molecules are then reviewed. Observed magnetoresistance points toward successful spin injection and detection, but spurious magnetoresistance effects can easily be confused with spin accumulation. A few studies report long spin relaxation times and lengths, which forms a promising basis for further research. We conclude with discussing outstanding questions and problems. (topical review)

High proton polarization at high temperature with single crystals of aromatic molecules

International Nuclear Information System (INIS)

Iinuma, M.; Takahashi, Y.; Shake, I.; Oda, M.; Masaike, A.; Yabuzaki, T.; Shimizu, H.M.

2004-01-01

Protons in single crystals of naphthalene doped with pentacene and p-terphenyl doped with pentacene have been polarized up to 32% and 18%, respectively. Such polarization has been achieved at liquid nitrogen temperature in a magnetic field of 3 kG by means of microwave-induced optical nuclear polarization. We also measured the polarization by the neutron transmission method. The relaxation time at 77 K in 7 G was found to be about 3 h and the enhancement of the obtained polarization compared with thermal polarization reached 8x10 4 . This method is applicable to neutron experiments

Polarization-dependent NEXAFS study of adsorption of long-chain surfactants on mechanically milled iron powder

Energy Technology Data Exchange (ETDEWEB)

Syugaev, A.V., E-mail: syual@mail.ru; Maratkanova, A.N.

2014-08-15

Highlights: • Plate-like particles modified with surfactant molecules were obtained under high-energy ball milling. • Adsorption layers were studied with polarization-dependent NEXAFS spectroscopy. • For the first time, arrangement of surfactants molecules on the powdered metal surface has been determined. • Tails of surfactant molecules (C-F/C-H) are shown to be oriented perpendicular to the particle surface. • Arrangement of carboxylate groups on the particle surfaces is discussed. - Abstract: In this work we have demonstrated the possibility of using the polarization-dependent NEXAFS spectra to study the structure of organic layers at the surface of powdered materials with plate-like shaped particles. The polarization dependence of the NEXAFS spectra may be easily obtained by just changing the angle between the X-ray beam direction and the substrate onto which the powder particles are set. For the first time, we have carried out a detailed study of the surfactant layers (n-perfluorononanoic and stearic acid), which are formed at the surface of iron plate-like particles under mechanical milling of iron powder with an addition of corresponding surfactants. The surfactant molecules are predominantly oriented perpendicular to the surface of the mechanically milled particles. Such orientation is similar to the arrangement of the molecules in the layers formed under equilibrium conditions, e.g. deposition from solutions. The changes in the chemical environment occurring in the molecule tails (defluorination or dehydrogenation) under mechanochemical treatment, do not result in a significant change in the molecular orientation and disordering of the adsorbed layer.

Behavior of tight-junction, adherens-junction and cell polarity proteins during HNF-4α-induced epithelial polarization

International Nuclear Information System (INIS)

Satohisa, Seiro; Chiba, Hideki; Osanai, Makoto; Ohno, Shigeo; Kojima, Takashi; Saito, Tsuyoshi; Sawada, Norimasa

2005-01-01

We previously reported that expression of tight-junction molecules occludin, claudin-6 and claudin-7, as well as establishment of epithelial polarity, was triggered in mouse F9 cells expressing hepatocyte nuclear factor (HNF)-4α [H. Chiba, T. Gotoh, T. Kojima, S. Satohisa, K. Kikuchi, M. Osanai, N. Sawada. Hepatocyte nuclear factor (HNF)-4α triggers formation of functional tight junctions and establishment of polarized epithelial morphology in F9 embryonal carcinoma cells, Exp. Cell Res. 286 (2003) 288-297]. Using these cells, we examined in the present study behavior of tight-junction, adherens-junction and cell polarity proteins and elucidated the molecular mechanism behind HNF-4α-initiated junction formation and epithelial polarization. We herein show that not only ZO-1 and ZO-2, but also ZO-3, junctional adhesion molecule (JAM)-B, JAM-C and cell polarity proteins PAR-3, PAR-6 and atypical protein kinase C (aPKC) accumulate at primordial adherens junctions in undifferentiated F9 cells. In contrast, CRB3, Pals1 and PATJ appeared to exhibit distinct subcellular localization in immature cells. Induced expression of HNF-4α led to translocation of these tight-junction and cell polarity proteins to beltlike tight junctions, where occludin, claudin-6 and claudin-7 were assembled, in differentiated cells. Interestingly, PAR-6, aPKC, CRB3 and Pals1, but not PAR-3 or PATJ, were also concentrated on the apical membranes in differentiated cells. These findings indicate that HNF-4α provokes not only expression of tight-junction adhesion molecules, but also modulation of subcellular distribution of junction and cell polarity proteins, resulting in junction formation and epithelial polarization

Layers of Cold Dipolar Molecules in the Harmonic Approximation

DEFF Research Database (Denmark)

R. Armstrong, J.; Zinner, Nikolaj Thomas; V. Fedorov, D.

2012-01-01

We consider the N-body problem in a layered geometry containing cold polar molecules with dipole moments that are polarized perpendicular to the layers. A harmonic approximation is used to simplify the hamiltonian and bound state properties of the two-body inter-layer dipolar potential are used...... to adjust this effective interaction. To model the intra-layer repulsion of the polar molecules, we introduce a repulsive inter-molecule potential that can be parametrically varied. Single chains containing one molecule in each layer, as well as multi-chain structures in many layers are discussed...... and their energies and radii determined. We extract the normal modes of the various systems as measures of their volatility and eventually of instability, and compare our findings to the excitations in crystals. We find modes that can be classified as either chains vibrating in phase or as layers vibrating against...

Doping effect on photoabsorption and charge-separation dynamics in light-harvesting organic molecule

Directory of Open Access Journals (Sweden)

Satoshi Ohmura

2016-01-01

Full Text Available Using ab-initio theoretical methods, we demonstrate possible enhancement of photo-conversion efficiency of an organic solar cell via intentional doping in molecular graphene-fullerene heterojunction [the hexabenzocoronene (HBC-triethylene glycol (TEG–C60 molecule]. Photoabsorption analysis indicates oxygen substitution into HBC leads to an extension of the spectra up to an infrared regime. A quantum-mechanical molecular dynamics simulation incorporating nonadiabatic electronic transitions reveals that a dissociated charge state (D+ and A- in the O-doped system is more stable than the pristine case due to the presence of an effective barrier by the TEG HOMO/LUMO level. We also find that oxygen doping in HBC enhances the intermolecular carrier mobility after charge separation. On the other hand, the pristine molecule undergoes rapid recombination between donor and acceptor charges at the interface. These analyses suggest that the graphene oxidation opens a new window in the application of organic super-molecules to solar cells.

Doping effect on photoabsorption and charge-separation dynamics in light-harvesting organic molecule

Energy Technology Data Exchange (ETDEWEB)

Ohmura, Satoshi, E-mail: s.ohmura.m4@cc.it-hiroshima.ac.jp [Research Center for Condensed Matter Physics, Department of Civil Engineering and Urban Design, Hiroshima Institute of Technology, Hiroshima 731-5193 (Japan); Tsuruta, Kenji [Department of Electrical and Electronic Engineering, Okayama University, Okayama 700-8530 (Japan); Shimojo, Fuyuki [Department of Physics, Kumamoto University, Kumamoto 860-8555 Japan (Japan); Nakano, Aiichiro [Collaboratory for Advanced Computing and Simulations, Department of Computer Science, Department of Physics & Astronomy, Department of Chemical Engineering & Materials Science, Department of Biological Sciences, University of Southern California, CA90089-024 (United States)

2016-01-15

Using ab-initio theoretical methods, we demonstrate possible enhancement of photo-conversion efficiency of an organic solar cell via intentional doping in molecular graphene-fullerene heterojunction [the hexabenzocoronene (HBC)-triethylene glycol (TEG)–C{sub 60} molecule]. Photoabsorption analysis indicates oxygen substitution into HBC leads to an extension of the spectra up to an infrared regime. A quantum-mechanical molecular dynamics simulation incorporating nonadiabatic electronic transitions reveals that a dissociated charge state (D{sup +} and A{sup -}) in the O-doped system is more stable than the pristine case due to the presence of an effective barrier by the TEG HOMO/LUMO level. We also find that oxygen doping in HBC enhances the intermolecular carrier mobility after charge separation. On the other hand, the pristine molecule undergoes rapid recombination between donor and acceptor charges at the interface. These analyses suggest that the graphene oxidation opens a new window in the application of organic super-molecules to solar cells.

Thin-film morphology of inkjet-printed single-droplet organic transistors using polarized Raman spectroscopy: effect of blending TIPS-pentacene with insulating polymer.

Science.gov (United States)

James, David T; Kjellander, B K Charlotte; Smaal, Wiljan T T; Gelinck, Gerwin H; Combe, Craig; McCulloch, Iain; Wilson, Richard; Burroughes, Jeremy H; Bradley, Donal D C; Kim, Ji-Seon

2011-12-27

We report thin-film morphology studies of inkjet-printed single-droplet organic thin-film transistors (OTFTs) using angle-dependent polarized Raman spectroscopy. We show this to be an effective technique to determine the degree of molecular order as well as to spatially resolve the orientation of the conjugated backbones of the 6,13-bis(triisopropylsilylethynyl)pentacene (TIPS-Pentacene) molecules. The addition of an insulating polymer, polystyrene (PS), does not disrupt the π-π stacking of the TIPS-Pentacene molecules. Blending in fact improves the uniformity of the molecular morphology and the active layer coverage within the device and reduces the variation in molecular orientation between polycrystalline domains. For OTFT performance, blending enhances the saturation mobility from 0.22 ± 0.05 cm(2)/(V·s) (TIPS-Pentacene) to 0.72 ± 0.17 cm(2)/(V·s) (TIPS-Pentacene:PS) in addition to improving the quality of the interface between TIPS-Pentacene and the gate dielectric in the channel, resulting in threshold voltages of ∼0 V and steep subthreshold slopes.

Organic Semiconductor-Containing Supramolecules: Effect of Small Molecule Crystallization and Molecular Packing

KAUST Repository

Rancatore, Benjamin J.; Kim, BongSoo; Mauldin, Clayton E.; Frechet, Jean; Xu, Ting

2016-01-01

on these highly crystalline molecules differs from their less crystalline counterparts. Here, two families of organic semiconductor SMs are investigated, where the composition of the crystalline core, the location (side- vs end-functionalization) of the alkyl

Charge-Transfer States in Organic Solar Cells: Understanding the Impact of Polarization, Delocalization, and Disorder

KAUST Repository

Zheng, Zilong

2017-05-08

We investigate the impact of electronic polarization, charge delocalization, and energetic disorder on the charge-transfer (CT) states formed at a planar C60/pentacene interface. The ability to examine large complexes containing up to seven pentacene molecules and three C60 molecules allows us to take explicitly into account the electronic polarization effects. These complexes are extracted from a bilayer architecture modeled by molecular dynamics simulations and evaluated by means of electronic-structure calculations based on long-range-separated functionals (ωB97XD and BNL) with optimized range-separation parameters. The energies of the lowest charge-transfer states derived for the large complexes are in very good agreement with the experimentally reported values. The average singlet-triplet energy splittings of the lowest CT states are calculated not to exceed 10 meV. The rates of geminate recombination as well as of dissociation of the triplet excitons are also evaluated. In line with experiment, our results indicate that the pentacene triplet excitons generated through singlet fission can dissociate into separated charges on a picosecond time scale, despite the fact that their energy in C60/pentacene heterojunctions is slightly lower than the energies of the lowest CT triplet states.

The tritium labelling of organic molecules by heterogeneous catalytic exchange

International Nuclear Information System (INIS)

Angoso Marina, M.; Kaiser Ruiz del Olmo, F.

1977-01-01

The influence of the temperature at 65 degree centigree and 120 degree centigree on the labelling of three organic molecules with tritium was studied. The compounds were: benzoic acid, de phenyl glyoxal and 2,3-tetramethylene-4-pantothenyl-7-oxo diacetin.The method employed was the heterogeneous catalytic exchange between tritiated water and the organic compound. The purification was made by thin-layer chromatography and the concentration, purity and specific activity of the products were determined by counting and ultraviolet techniques. The thermal stability and the radiolytic effects on labelled benzoic acid were also considered. (Author) 9 refs

Polarization in free electron lasers

Energy Technology Data Exchange (ETDEWEB)

Papadichev, V.A. [Lebedev Physical Institute, Moscow (Russian Federation)

1995-12-31

Polarization of electromagnetic radiation is required very often in numerous scientific and industrial applications: studying of crystals, molecules and intermolecular interaction high-temperature superconductivity, semiconductors and their transitions, polymers and liquid crystals. Using polarized radiation allows to obtain important data (otherwise inaccessible) in astrophysics, meteorology and oceanology. It is promising in chemistry and biology for selective influence on definite parts of molecules in chain synthesis reactions, precise control of various processes at cell and subcell levels, genetic engineering etc. Though polarization methods are well elaborated in optics, they can fail in far-infrared, vacuum-ultraviolet and X-ray regions because of lack of suitable non-absorbing materials and damaging of optical elements at high specific power levels. Therefore, it is of some interest to analyse polarization of untreated FEL radiation obtained with various types of undulators, with and without axial magnetic field. The polarization is studied using solutions for electron orbits in various cases: plane or helical undulator with or without axial magnetic field, two plane undulators, a combination of right- and left-handed helical undulators with equal periods, but different field amplitudes. Some examples of how a desired polarization (elliptical circular or linear) can be obtained or changed quickly, which is necessary in many experiments, are given.

Xenoendocrine pollutants may reduce size of sexual organs in East Greenland polar bears (Ursus maritimus)

DEFF Research Database (Denmark)

Sonne, Christian; Leifsson, Páll Skuli; Dietz, Rune

2006-01-01

Reproductive organs from 55 male and 44 female East Greenland polar bears were examined to investigate the potential negative impact from organohalogen pollutants (OHCs). Multiple regressions normalizing for age showed a significant inverse relationship between OHCs and testis length and baculum.......01) and uterine horn length and HCB (p = 0.02). The study suggests thatthere is an impact from xenoendocrine pollutants on the size of East Greenland polar bear genitalia. This may pose a riskto this polar bear subpopulation in the future because of reduced sperm and egg quality/quantity and uterus and penis size...

Electrical properties of in-situ grown and transferred organic nanofibers

DEFF Research Database (Denmark)

Oliveira Hansen, Roana Melina de; Madsen, Morten; Kjelstrup-Hansen, Jakob

2010-01-01

Para-hexaphenylene (p6P) molecules have the ability to self-assemble into organic nanofibers, which exhibit a range of interesting optical and optoelectronic properties such as intense, polarized luminescence, waveguiding and lasing. The nanofibers are typically grown on specific single...

Molecular electron recollision dynamics in intense circularly polarized laser pulses

Science.gov (United States)

Bandrauk, André D.; Yuan, Kai-Jun

2018-04-01

Extreme UV and x-ray table top light sources based on high-order harmonic generation (HHG) are focused now on circular polarization for the generation of circularly polarized attosecond pulses as new tools for controlling electron dynamics, such as charge transfer and migration and the generation of attosecond quantum electron currents for ultrafast magneto-optics. A fundamental electron dynamical process in HHG is laser induced electron recollision with the parent ion, well established theoretically and experimentally for linear polarization. We discuss molecular electron recollision dynamics in circular polarization by theoretical analysis and numerical simulation. The control of the polarization of HHG with circularly polarized ionizing pulses is examined and it is shown that bichromatic circularly polarized pulses enhance recollision dynamics, rendering HHG more efficient, especially in molecules because of their nonspherical symmetry. The polarization of the harmonics is found to be dependent on the compatibility of the rotational symmetry of the net electric field created by combinations of bichromatic circularly polarized pulses with the dynamical symmetry of molecules. We show how the field and molecule symmetry influences the electron recollision trajectories by a time-frequency analysis of harmonics. The results, in principle, offer new unique controllable tools in the study of attosecond molecular electron dynamics.

Mechanism of formation of humus coatings on mineral surfaces 3. Composition of adsorbed organic acids from compost leachate on alumina by solid-state 13C NMR

Science.gov (United States)

Wershaw, R. L.; Llaguno, E.C.; Leenheer, J.A.

1996-01-01

The adsorption of compost leachate DOC on alumina is used as a model for elucidation of the mechanism of formation of natural organic coatings on hydrous metal oxide surfaces in soils and sediments. Compost leachate DOC is composed mainly of organic acid molecules. The solid-state 13C NMR spectra of these organic acids indicate that they are very similar in composition to aquatic humic substances. Changes in the solid-state 13C NMR spectra of compost leachate DOC fractions adsorbed on alumina indicate that the DOC molecules are most likely adsorbed on metal oxide surfaces through a combination of polar and hydrophobic interaction mechanisms. This combination of polar and hydrophobic mechanism leads to the formation of bilayer coatings of the leachate molecules on the oxide surfaces.

Development of new methods in modern selective organic synthesis: preparation of functionalized molecules with atomic precision

International Nuclear Information System (INIS)

Ananikov, V P; Khemchyan, L L; Ivanova, Yu V; Dilman, A D; Levin, V V; Bukhtiyarov, V I; Sorokin, A M; Prosvirin, I P; Romanenko, A V; Simonov, P A; Vatsadze, S Z; Medved'ko, A V; Nuriev, V N; Nenajdenko, V G; Shmatova, O I; Muzalevskiy, V M; Koptyug, I V; Kovtunov, K V; Zhivonitko, V V; Likholobov, V A

2014-01-01

The challenges of the modern society and the growing demand of high-technology sectors of industrial production bring about a new phase in the development of organic synthesis. A cutting edge of modern synthetic methods is introduction of functional groups and more complex structural units into organic molecules with unprecedented control over the course of chemical transformation. Analysis of the state-of-the-art achievements in selective organic synthesis indicates the appearance of a new trend — the synthesis of organic molecules, biologically active compounds, pharmaceutical substances and smart materials with absolute selectivity. Most advanced approaches to organic synthesis anticipated in the near future can be defined as 'atomic precision' in chemical reactions. The present review considers selective methods of organic synthesis suitable for transformation of complex functionalized molecules under mild conditions. Selected key trends in the modern organic synthesis are considered including the preparation of organofluorine compounds, catalytic cross-coupling and oxidative cross-coupling reactions, atom-economic addition reactions, methathesis processes, oxidation and reduction reactions, synthesis of heterocyclic compounds, design of new homogeneous and heterogeneous catalytic systems, application of photocatalysis, scaling up synthetic procedures to industrial level and development of new approaches to investigation of mechanisms of catalytic reactions. The bibliography includes 840 references

Electrochemical behavior of uranyl in anhydrous polar organic media

Energy Technology Data Exchange (ETDEWEB)

Burn, Adam G.; Nash, Kenneth L. [Washington State Univ., Pullmann, WA (United States). Dept. of Chemistry

2017-09-01

Weak complexes between pentavalent and hexavalent actinyl cations have been reported to exist in acidic, non-complexing high ionic strength aqueous media. Such ''cation-cation complexes'' were first identified in the context of actinide-actinide redox reactions in acidic aqueous media relevant to solvent extraction-based separation systems, hence their characterization is of potential interest for advanced nuclear fuel reprocessing. This chemistry could be relevant to efforts to develop advanced actinide separations based on the upper oxidation states of americium, which are of current interest. In the present study, the chemical behavior of pentavalent uranyl was examined in non-aqueous, aprotic polar organic solvents (propylene carbonate and acetonitrile) to determine whether UO{sub 2}{sup +} cations generated at the reducing working electrode surface would interact with the UO{sub 2}{sup 2+} cations in the bulk phase to form cation-cation complexes in such media. In magnesium perchlorate media, the electrolyte adsorbed onto the working electrode surface and interfered with the uranyl reduction/diffusion process through an ECE (electron transfer/chemical reaction/electron transfer) mechanism. In parallel studies of uranyl redox behavior in tetrabutylammonium hexafluorophosphate solutions, an EC (electron transfer/chemical reaction) mechanism was observed in the cyclic voltammograms. Ultimately, no conclusive electrochemical evidence demonstrated uranyl cation-cation interactions in the non-aqueous, aprotic polar organic solvent solutions, though the results reported do not completely rule out the presence of UO{sub 2}{sup +}.UO{sub 2}{sup 2+} complexes.

Spatial and temporal variation in size of polar bear (Ursus maritimus) sexual organs and its use in pollution and climate change studies.

Science.gov (United States)

Sonne, Christian; Dietz, Rune; Born, Erik W; Riget, Frank F; Leifsson, Pall S; Bechshøft, Thea Ø; Kirkegaard, Maja

2007-11-15

Sexual organs and their development are susceptible to atmospheric transported environmental xenoendocrine pollutants and climate change (food availability). We therefore investigated sexual organs from 55 male and 44 female East Greenland polar bears (Ursus maritimus) to obtain information about growth/size and sexual maturity. Then, the genitalia size was compared with those previously reported from Canadian and Svalbard polar bears. Growth models showed that East Greenland male polar bears reached sexual maturity around 7 years of age and females around 4 years of age. When comparing East Greenland and Svalbard polar bears, the size of baculum and uterus were significantly lower in the East Greenland polar bears (ANOVA: all p polar bears, a similar baculum pattern was found for East Greenland vs. Canadian polar bears. It is speculated whether this could be a result of the general high variation in polar bear body size, temporal distribution patterns of anthropogenic long-range transported persistent organic pollutants or climate change (decreasing food availability). The present investigation represents conservation and background data for future spatial and temporal assessments of hunting, pollution and climate change scenarios.

Passive sampling of selected endocrine disrupting compounds using polar organic chemical integrative samplers

International Nuclear Information System (INIS)

Arditsoglou, Anastasia; Voutsa, Dimitra

2008-01-01

Two types of polar organic chemical integrative samplers (pharmaceutical POCIS and pesticide POCIS) were examined for their sampling efficiency of selected endocrine disrupting compounds (EDCs). Laboratory-based calibration of POCISs was conducted by exposing them at high and low concentrations of 14 EDCs (4-alkyl-phenols, their ethoxylate oligomers, bisphenol A, selected estrogens and synthetic steroids) for different time periods. The kinetic studies showed an integrative uptake up to 28 days. The sampling rates for the individual compounds were obtained. The use of POCISs could result in an integrative approach to the quality status of the aquatic systems especially in the case of high variation of water concentrations of EDCs. The sampling efficiency of POCISs under various field conditions was assessed after their deployment in different aquatic environments. - Calibration and field performance of polar organic integrative samplers for monitoring EDCs in aquatic environments

Prediction of molecular separation of polar-apolar mixtures on heterogeneous metal-organic frameworks: HKUST-1.

Science.gov (United States)

Van Assche, Tom R C; Duerinck, Tim; Van der Perre, Stijn; Baron, Gino V; Denayer, Joeri F M

2014-07-08

Due to the combination of metal ions and organic linkers and the presence of different types of cages and channels, metal-organic frameworks often possess a large structural and chemical heterogeneity, complicating their adsorption behavior, especially for polar-apolar adsorbate mixtures. By allocating isotherms to individual subunits in the structure, the ideal adsorbed solution theory (IAST) can be adjusted to cope with this heterogeneity. The binary adsorption of methanol and n-hexane on HKUST-1 is analyzed using this segregated IAST (SIAST) approach and offers a significant improvement over the standard IAST model predictions. It identifies the various HKUST-1 cages to have a pronounced polar or apolar adsorptive behavior.

Intercalation of organic molecules into SnS2 single crystals

International Nuclear Information System (INIS)

Toh, M.L.; Tan, K.J.; Wei, F.X.; Zhang, K.K.; Jiang, H.; Kloc, C.

2013-01-01

SnS 2 is a layered semiconductor with a van der Waals gap separating the covalently bonded layers. In this study, post-synthesis intercalation of donor organic amine molecules, such as ethylenediamine (en), into tin disulfide and secondary intercalation of p-phenylenediamine (PPD) and 1, 5-naphthalenediamine (NDA) into SnS 2e n have been verified with X-ray diffraction. PPD and NDA did not intercalate directly even during prolonged annealing but replaced en readily if en was already present in the van der Waals gap. The c-lattice dilation is proportional to the intercalant size. Unit cell lattices of intercalated products were determined from the positions of the X-ray diffraction peaks. Optical images taken during the intercalation showed that intercalation progressed from the periphery towards the interior of the crystal. TEM diffraction patterns in the [0 0 1] direction of SnS 2 after intercalation revealed defects and stacking mismatches among the SnS 2 layers caused by the intercalation. UV–Vis absorption studies showed a red shift in the band edge of the SnS 2 material after intercalation. The band edge was 2.2 eV for pristine SnS 2 ; after intercalation with en or PPD, the absorbance spectra band edges shifted to approximately 0.7 eV or 0.5 eV, respectively. - Graphical Abstract: SnS 2 single crystals were intercalated with organic amine molecules such as ethylenediamine, phenylenediamine and naphthalenediamine. Absorption studies showed red shift of band edge after intercalation, which was consistent with optical observations. X-ray diffraction indicated lattice dilation in the c-lattice of SnS 2 after intercalation. Highlights: ► Organic molecules intercalated inhomogenously between covalently bonded SnS 2 layers. ► Ethylenediamine (en) intercalate directly into SnS 2 . ► Phenylenediamine (PPD) and naphthalenediamine (NDA) can be intercalated into SnS 2 secondary. ► In a secondary intercalation the bonds between layers are weakened by direct

Density Functional Investigation of Graphene Doped with Amine-Based Organic Molecules

Directory of Open Access Journals (Sweden)

Yeun Hee Hwang

2015-01-01

Full Text Available To improve the electronic properties of graphene, many doping techniques have been studied. Herein, we investigate the electronic and molecular structure of doped graphene using density functional theory, and we report the effects of amine-based benzene dopants adsorbed on graphene. Density functional theory (DFT calculations were performed to determine the role of amine-based aromatic compounds in graphene doping. These organic molecules bind to graphene through long-range interactions such as π-π interactions and C-H⋯π hydrogen bonding. We compared the electronic structures of pristine graphene and doped graphene to understand the electronic structure of doped graphene at the molecular level. Also, work functions of doped graphene were obtained from electrostatic potential calculations. A decrease in the work function was observed when the amine-based organic compounds were adsorbed onto graphene. Because these systems are based on physisorption, there was no obvious band structure change at point K at the Fermi level after doping. However, the amine-based organic dopants did change the absolute Fermi energy levels. In this study, we showed that the Fermi levels of the doped graphene were affected by the HOMO energy level of the dopants and by the intermolecular charge transfer between the adsorbed molecules and graphene.

Single-molecule tracking of small GTPase Rac1 uncovers spatial regulation of membrane translocation and mechanism for polarized signaling

Science.gov (United States)

Das, Sulagna; Yin, Taofei; Yang, Qingfen; Zhang, Jingqiao; Wu, Yi I.; Yu, Ji

2015-01-01

Polarized Rac1 signaling is a hallmark of many cellular functions, including cell adhesion, motility, and cell division. The two steps of Rac1 activation are its translocation to the plasma membrane and the exchange of nucleotide from GDP to GTP. It is, however, unclear whether these two processes are regulated independent of each other and what their respective roles are in polarization of Rac1 signaling. We designed a single-particle tracking (SPT) method to quantitatively analyze the kinetics of Rac1 membrane translocation in living cells. We found that the rate of Rac1 translocation was significantly elevated in protrusions during cell spreading on collagen. Furthermore, combining FRET sensor imaging with SPT measurements in the same cell, the recruitment of Rac1 was found to be polarized to an extent similar to that of the nucleotide exchange process. Statistical analysis of single-molecule trajectories and optogenetic manipulation of membrane lipids revealed that Rac1 membrane translocation precedes nucleotide exchange, and is governed primarily by interactions with phospholipids, particularly PI(3,4,5)P3, instead of protein factors. Overall, the study highlights the significance of membrane translocation in spatial Rac1 signaling, which is in addition to the traditional view focusing primarily on GEF distribution and exchange reaction. PMID:25561548

Polarization Selectivity of Artificial Anisotropic Structures Based on DNA-Like Helices

International Nuclear Information System (INIS)

Semchenko, I. V.; Khakhomov, S. A.; Balmakov, A. P.

2010-01-01

Currently, 2D and 3D structures of different symmetries can be formed from DNA molecules. The electromagnetic properties of this new natural chiral material can be changed by metalizing DNA. Spatial structures of this type can be used in nanotechnology to prepare metamaterials for the far-UV region. It is shown by the example of an octahedron and a cube composed of DNA-like helices that these structures may exhibit polarization selectivity to electromagnetic radiation. In addition, it is suggested that the effect of the polarization selectivity of DNA-like artificial structures may also occur in the soft X-ray region for all living organisms in nature due to the universal DNA form.

Theory of photoelectron spectroscopy for organic molecules and their crystals

International Nuclear Information System (INIS)

Fujikawa, Takashi; Niki, Kaori; Sakuma, Hiroto

2015-01-01

Highlights: • Some specific features in photoemission theory from organic solids are reviewed. • Extrinsic and intrinsic effects are discussed. • Photoemission from extended levels is compared with that from core levels. • First principle many-body theories are discussed on the basis of nonequilibrium Green's functions. - Abstract: In this short review we discuss recent progress in photoemission theory for organic molecules and their crystals. We discuss some important features in Keldysh Green's function theory for the photoemission. We briefly discuss many-body aspects in photoemission from core and extended levels. In particular phonon effects are investigated in more detail since organic solids are typically soft where electron–phonon interaction is important. Debye–Waller factor suppresses the interference effects of photoelectron waves which makes ARPES analyses useless, particularly in high energy region.

Nucleation of Organic Molecules via a Hot Precursor State: Pentacene on Amorphous Mica

Science.gov (United States)

2013-01-01

Organic thin films have attracted considerable interest due to their applicability in organic electronics. The classical scenario for thin film nucleation is the diffusion-limited aggregation (DLA). Recently, it has been shown that organic thin film growth is better described by attachment-limited aggregation (ALA). However, in both cases, an unusual relationship between the island density and the substrate temperature was observed. Here, we present an aggregation model that goes beyond the classical DLA or ALA models to explain this behavior. We propose that the (hot) molecules impinging on the surface cannot immediately equilibrate to the substrate temperature but remain in a hot precursor state. In this state, the molecules can migrate considerable distances before attaching to a stable or unstable island. This results in a significantly smaller island density than expected by assuming fast equilibration and random diffusion. We have applied our model to pentacene film growth on amorphous Muscovite mica. PMID:24340130

Adsorption of organic molecules on mineral surfaces studied by first-principle calculations: A review.

Science.gov (United States)

Zhao, Hongxia; Yang, Yong; Shu, Xin; Wang, Yanwei; Ran, Qianping

2018-04-09

First-principle calculations, especially by the density functional theory (DFT) methods, are becoming a power technique to study molecular structure and properties of organic/inorganic interfaces. This review introduces some recent examples on the study of adsorption models of organic molecules or oligomers on mineral surfaces and interfacial properties obtained from first-principles calculations. The aim of this contribution is to inspire scientists to benefit from first-principle calculations and to apply the similar strategies when studying and tailoring interfacial properties at the atomistic scale, especially for those interested in the design and development of new molecules and new products. Copyright © 2017. Published by Elsevier B.V.

Diffusion and retention of organic anions in Callovian-Oxfordian clay rock

International Nuclear Information System (INIS)

Rasamimanana, Sabrina

2016-01-01

The Callovo-Oxfordian mud-stone (CO_x) is studied as a possible host rock for a deep disposal of radioactive waste (Cigeo project). Indeed, besides being very weakly permeable, it presents a high content of clayey minerals, capable of retaining radionuclides under cationic form and to delay strongly their transport. Nevertheless, some waste packages may release a significant amount of organic molecules, capable of complexing these radionuclides and drastically increase their mobility. So, the objective of this work was to better understand the diffusive behavior of several organic molecules of interest in this mudstone, by investigating at first their affinity with the host rock. The retention of organic molecules under anionic form (acetate, phthalate, adipate, benzoate, and citrate) was quantified on to the dispersed CO_x mudstone using adsorption/desorption batch experiments. Experiments on de-carbonated rock and clay fraction only (≤ 2μm) were also performed to identify solid phases and chemical functions responsible for the retention. a correlation of the intensity of retention, R_d, was pointed out whit the dipole moment μ(Orga.), providing a qualitative estimate of retention capacity for polar hydrophilic organic molecules. So, phthalate, slightly polar, displays a reversible retention (R_d ≅1,6 L.kg"-"1), mainly on clayey phases. Citrate, very polar and strongly adsorbed (R_d ≅ 40 L.kg"-"1), displays a persistent desorption hysteresis and an affinity to different solid phases (clayey minerals and minor oxides). Lastly, acetate, adipate and benzoate, weakly polar, display a lower affinity with rock (R_d ≤ 0,2 L.kg"-"1). The diffusive behavior in compact rock of these organic anions was then studied. The effective diffusion coefficient and retardation factor values were quantified. The low diffusivity, [D_e/D_0](Organic Anions) ≅ 0,1 a0,25 * [D_e/D_0](Water) evidences an effect of anionic exclusion, with a same intensity as that observed for

A Nonfullerene Small Molecule Acceptor with 3D Interlocking Geometry Enabling Efficient Organic Solar Cells.

Science.gov (United States)

Lee, Jaewon; Singh, Ranbir; Sin, Dong Hun; Kim, Heung Gyu; Song, Kyu Chan; Cho, Kilwon

2016-01-06

A new 3D nonfullerene small-molecule acceptor is reported. The 3D interlocking geometry of the small-molecule acceptor enables uniform molecular conformation and strong intermolecular connectivity, facilitating favorable nanoscale phase separation and electron charge transfer. By employing both a novel polymer donor and a nonfullerene small-molecule acceptor in the solution-processed organic solar cells, a high-power conversion efficiency of close to 6% is demonstrated. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Circular polarization analyzer with polarization tunable focusing of surface plasmon polaritons

Energy Technology Data Exchange (ETDEWEB)

Wang, Sen; Zhang, Yan, E-mail: yzhang@mail.cnu.edu.cn [Department of Physics, Harbin Institute of Technology, Harbin 150001 (China); Beijing Key Laboratory for Metamaterials and Devices, and Key Laboratory of Terahertz Optoelectronics, Ministry of Education, Department of Physics, Capital Normal University, Beijing 100048 (China); Wang, Xinke [Beijing Key Laboratory for Metamaterials and Devices, and Key Laboratory of Terahertz Optoelectronics, Ministry of Education, Department of Physics, Capital Normal University, Beijing 100048 (China); Kan, Qiang [State Key Laboratory for Integrated Optoelectronics, Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083 (China); Qu, Shiliang [Optoelectronics Department, Harbin Institute of Technology at Weihai, Weihai 264209 (China)

2015-12-14

A practical circular polarization analyzer (CPA) that can selectively focus surface plasmon polaritons (SPPs) at two separate locations, according to the helicity of the circularly polarized light, is designed and experimentally verified in the terahertz frequency range. The CPA consists of fishbone-slit units and is designed using the simulated annealing algorithm. By differentially detecting the intensities of the two SPPs focuses, the helicity of the incident circularly polarized light can be obtained and the CPA is less vulnerable to the noise of incident light. The proposed device may also have wide potential applications in chiral SPPs photonics and the analysis of chiral molecules in biology.

Complex organic molecules in the Galactic Centre: the N-bearing family

Science.gov (United States)

Zeng, S.; Jiménez-Serra, I.; Rivilla, V. M.; Martín, S.; Martín-Pintado, J.; Requena-Torres, M. A.; Armijos-Abendaño, J.; Riquelme, D.; Aladro, R.

2018-05-01

We present an unbiased spectral line survey toward the Galactic Centre (GC) quiescent giant molecular cloud (QGMC), G+0.693 using the GBT and IRAM 30 telescopes. Our study highlights an extremely rich organic inventory of abundant amounts of nitrogen (N)-bearing species in a source without signatures of star formation. We report the detection of 17 N-bearing species in this source, of which 8 are complex organic molecules (COMs). A comparison of the derived abundances relative to H2 is made across various galactic and extragalactic environments. We conclude that the unique chemistry in this source is likely to be dominated by low-velocity shocks with X-rays/cosmic rays also playing an important role in the chemistry. Like previous findings obtained for O-bearing molecules, our results for N-bearing species suggest a more efficient hydrogenation of these species on dust grains in G+0.693 than in hot cores in the Galactic disk, as a consequence of the low dust temperatures coupled with energetic processing by X-ray/cosmic ray radiation in the GC.

Light incoupling in small molecule organic solar cells

Energy Technology Data Exchange (ETDEWEB)

Allinger, Nikola; Meiss, Jan; Riede, Moritz; Leo, Karl [Institut fuer Angewandte Photophysik, Technische Universitaet Dresden, 01069 Dresden (Germany); Gnehr, Wolf-Michael [Heliatek GmbH, Liebigstrasse 26, 01187 Dresden (Germany)

2008-07-01

Light incoupling is an essential topic for optimization of organic solar cells. In our group, we examine light incoupling of different kinds of transparent contacting materials as well as external dielectric coatings, using optical simulation of thin film systems and experimental methods. Thin films of small molecules are prepared by thermal evaporation in a multi-chamber UHV system. Complex refraction indices of various materials are calculated from reflection and transmission measurements of monolayers. For modelling of optical properties of thin film systems, we developed a numerical simulation program based on the transfer matrix method. The cell structures investigated consist of nanolayers of small molecules, using ZnPc/C60 as an acceptor-donor heterojunction. As contact materials, we compare the expensive standard material indium tin oxide (ITO) with more cost-efficient alternatives like thin Ag layers or spin-coated layers of the polymer PEDOT:PSS, and discuss the resulting cell properties. Additional dielectric layers of varying materials, like tris(8-hydroxy-quinolinate)-aluminum (Alq3) or N,N'-tetrakis(4-methoxyphenyl)-benzidine (MeO-TPD), are deposited on top of the stack and their influence on cell efficiencies is investigated.

Investigation of Multiconfigurational Short-Range Density Functional Theory for Electronic Excitations in Organic Molecules

DEFF Research Database (Denmark)

Hubert, Mickaël; Hedegård, Erik D.; Jensen, Hans Jørgen Aa

2016-01-01

-srDFT for a selected benchmark set of electronic excitations of organic molecules, covering the most common types of organic chromophores. This investigation confirms the expectation that the MC-srDFT method is accurate for a broad range of excitations and comparable to accurate wave function methods such as CASPT2......Computational methods that can accurately and effectively predict all types of electronic excitations for any molecular system are missing in the toolbox of the computational chemist. Although various Kohn-Sham density-functional methods (KS-DFT) fulfill this aim in some cases, they become...... and double excitations have been promising, it is nevertheless important that the accuracy of MC-srDFT is at least comparable to the best KS-DFT methods also for organic molecules that are typically of single-reference character. In this paper we therefore systematically investigate the performance of MC...

Control of π-Electron Rotations in Chiral Aromatic Molecules Using Intense Laser Pulses

Science.gov (United States)

Kanno, Manabu; Kono, Hirohiko; Fujimura, Yuichi

Our recent theoretical studies on laser-induced π-electron rotations in chiral aromatic molecules are reviewed. π electrons of a chiral aromatic molecule can be rotated along its aromatic ring by a nonhelical, linearly polarized laser pulse. An ansa aromatic molecule with a six-membered ring, 2,5-dichloro[n](3,6) pyrazinophane, which belongs to a planar-chiral molecule group, and its simplified molecule 2,5-dichloropyrazine are taken as model molecules. Electron wavepacket simulations in the frozen-molecular-vibration approximation show that the initial direction of π-electron rotation depends on the polarization direction of a linearly polarized laser pulse applied. Consecutive unidirectional rotation can be achieved by applying a sequence of linearly polarized pump and dump pulses to prevent reverse rotation. Optimal control simulations of π-electron rotation show that another controlling factor for unidirectional rotation is the relative optical phase between the different frequency components of an incident pulse in addition to photon polarization direction. Effects of nonadiabatic coupling between π-electron rotation and molecular vibrations are also presented, where the constraints of the frozen approximation are removed. The angular momentum gradually decays mainly owing to nonadiabatic coupling, while the vibrational amplitudes greatly depend on their rotation direction. This suggests that the direction of π-electron rotation on an attosecond timescale can be identified by detecting femtosecond molecular vibrations.

Organic Optoelectronic Devices Employing Small Molecules

Science.gov (United States)

Fleetham, Tyler Blain

Organic optoelectronic devices have remained a research topic of great interest over the past two decades, particularly in the development of efficient organic photovoltaics (OPV) and organic light emitting diodes (OLED). In order to improve the efficiency, stability, and materials variety for organic optoelectronic devices a number of emitting materials, absorbing materials, and charge transport materials were developed and employed in a device setting. Optical, electrical, and photophysical studies of the organic materials and their corresponding devices were thoroughly carried out. Two major approaches were taken to enhance the efficiency of small molecule based OPVs: developing material with higher open circuit voltages or improved device structures which increased short circuit current. To explore the factors affecting the open circuit voltage (VOC) in OPVs, molecular structures were modified to bring VOC closer to the effective bandgap, DeltaE DA, which allowed the achievement of 1V VOC for a heterojunction of a select Ir complex with estimated exciton energy of only 1.55eV. Furthermore, the development of anode interfacial layer for exciton blocking and molecular templating provide a general approach for enhancing the short circuit current. Ultimately, a 5.8% PCE was achieved in a single heterojunction of C60 and a ZnPc material prepared in a simple, one step, solvent free, synthesis. OLEDs employing newly developed deep blue emitters based on cyclometalated complexes were demonstrated. Ultimately, a peak EQE of 24.8% and nearly perfect blue emission of (0.148,0.079) was achieved from PtON7dtb, which approaches the maximum attainable performance from a blue OLED. Furthermore, utilizing the excimer formation properties of square-planar Pt complexes, highly efficient and stable white devices employing a single emissive material were demonstrated. A peak EQE of over 20% for pure white color (0.33,0.33) and 80 CRI was achieved with the tridentate Pt complex, Pt

Luminescence of Rubrene and DCJTB molecules in organic light-emitting devices

Energy Technology Data Exchange (ETDEWEB)

Moon, Chang-Bum, E-mail: cbmoon@hoseo.edu [Department of Display Engineering, Hoseo University, Sechul-Ri 160, Baebang, Asan, Chung-Nam 336-795 (Korea, Republic of); Department of Engineering Physics, McMaster University, Hamilton, Ontario, Canada L8S4L7 (Canada); Song, Wook; Meng, Mei; Kim, Nam Ho; Yoon, Ju-An [Department of Display Engineering, Hoseo University, Sechul-Ri 160, Baebang, Asan, Chung-Nam 336-795 (Korea, Republic of); Kim, Woo Young, E-mail: wykim@hoseo.edu [Department of Display Engineering, Hoseo University, Sechul-Ri 160, Baebang, Asan, Chung-Nam 336-795 (Korea, Republic of); Wood, Richard; Mascher, Peter [Department of Engineering Physics, McMaster University, Hamilton, Ontario, Canada L8S4L7 (Canada)

2014-02-15

We investigated the optical properties of light emission based on the resonance energy transfer mechanism between two molecules in the host–dopant systems. For this purpose, we fabricated the organic light-emitting devices with the different doped emissive layers. The host matrices were made of 4,4′,4″-tris(carbasol-l-nyl)triphenylamine (TCTA) and 2-methyl-9,10-di(2-naphthyl)anthracene (MADN) molecules and the doped molecules were 5,6,11,12-tetraphenylnaphtacene (Rubrene) and 4-(Dicyanomethylene)-2-tert-butyl-6- (1,1,7,7-tetramethyljulolidin-4-yl-vinyl)-4H-pyran (DCJTB). The concentrations of the doped molecules were 0.1%, 0.3%, 0.5%, and 0.8%. Through spectroscopic analysis using multi-peak fits with a Gaussian function to the emission spectra, we obtained the relative light intensity of the two dopants according to the doping concentrations and examined the relations between the molecular excited energy states and the nature of energy transfer in the host and dopant systems. We show that the luminous efficiency of the devices has a strong correlation between the energy transfer owing to the individual molecular intrinsic properties and the electrical characteristics associated with the bulky properties in the devices. -- Highlights: • Fabrication and characterization of the OLEDs with a host–dopant system in the emissive layer. • Investigation of the optical properties of light emission based on the resonance energy transfer mechanism between the dopant molecules. • EL and PL spectroscopic study for the structure of the molecular energy levels in the dopant molecules.

Single Molecule Spectroelectrochemistry of Interfacial Charge Transfer Dynamics In Hybrid Organic Solar Cell

Energy Technology Data Exchange (ETDEWEB)

Pan, Shanlin [Univ. of Alabama, Tuscaloosa, AL (United States)

2014-11-16

Our research under support of this DOE grant is focused on applied and fundamental aspects of model organic solar cell systems. Major accomplishments are: 1) we developed a spectroelectorchemistry technique of single molecule single nanoparticle method to study charge transfer between conjugated polymers and semiconductor at the single molecule level. The fluorescence of individual fluorescent polymers at semiconductor surfaces was shown to exhibit blinking behavior compared to molecules on glass substrates. Single molecule fluorescence excitation anisotropy measurements showed the conformation of the polymer molecules did not differ appreciably between glass and semiconductor substrates. The similarities in molecular conformation suggest that the observed differences in blinking activity are due to charge transfer between fluorescent polymer and semiconductor, which provides additional pathways between states of high and low fluorescence quantum efficiency. Similar spectroelectrochemistry work has been done for small organic dyes for understand their charge transfer dynamics on various substrates and electrochemical environments; 2) We developed a method of transferring semiconductor nanoparticles (NPs) and graphene oxide (GO) nanosheets into organic solvent for a potential electron acceptor in bulk heterojunction organic solar cells which employed polymer semiconductor as the electron donor. Electron transfer from the polymer semiconductor to semiconductor and GO in solutions and thin films was established through fluorescence spectroscopy and electroluminescence measurements. Solar cells containing these materials were constructed and evaluated using transient absorption spectroscopy and dynamic fluorescence techniques to understand the charge carrier generation and recombination events; 3) We invented a spectroelectorchemistry technique using light scattering and electroluminescence for rapid size determination and studying electrochemistry of single NPs in an

Polarization: A Must for Fusion

Directory of Open Access Journals (Sweden)

Guidal M.

2012-10-01

Full Text Available Recent realistic simulations confirm that the polarization of the fuel would improve significantly the DT fusion efficiency. We have proposed an experiment to test the persistence of the polarization in a fusion process, using a terawatt laser hitting a polarized HD target. The polarized deuterons heated in the plasma induced by the laser can fuse producing a 3He and a neutron in the final state. The angular distribution of the neutrons and the change in the corresponding total cross section are related to the polarization persistence. The experimental polarization of DT fuel is a technological challenge. Possible paths for Magnetic Confinement Fusion (MCF and for Inertial Confinement Fusion (ICF are reviewed. For MCF, polarized gas can be used. For ICF, cryogenic targets are required. We consider both, the polarization of gas and the polarization of solid DT, emphasizing the Dynamic Nuclear polarization (DNP of HD and DT molecules.

Oxidative addition of C--H bonds in organic molecules to transition metal centers

International Nuclear Information System (INIS)

Bergman, R.G.

1989-04-01

Alkanes are among the most chemically inert organic molecules. They are reactive toward a limited range of reagents, such as highly energetic free radicals and strongly electrophilic and oxidizing species. This low reactivity is a consequence of the C--H bond energies in most saturated hydrocarbons. These values range from 90 to 98 kcal/mole for primary and secondary C--H bonds; in methane, the main constituent of natural gas, the C--H bond energy is 104 kcal/mole. This makes methane one of the most common but least reactive organic molecules in nature. This report briefly discusses the search for metal complexes capable of undergoing the C--H oxidative addition process allowing alkane chemistry to be more selective than that available using free radical reagents. 14 refs

Current-induced switching of magnetic molecules on topological insulator surfaces

Science.gov (United States)

Locane, Elina; Brouwer, Piet W.

2017-03-01

Electrical currents at the surface or edge of a topological insulator are intrinsically spin polarized. We show that such surface or edge currents can be used to switch the orientation of a molecular magnet weakly coupled to the surface or edge of a topological insulator. For the edge of a two-dimensional topological insulator as well as for the surface of a three-dimensional topological insulator the application of a well-chosen surface or edge current can lead to a complete polarization of the molecule if the molecule's magnetic anisotropy axis is appropriately aligned with the current direction. For a generic orientation of the molecule a nonzero but incomplete polarization is obtained. We calculate the probability distribution of the magnetic states and the switching rates as a function of the applied current.

Core Level Spectra of Organic Molecules Adsorbed on Graphene

Directory of Open Access Journals (Sweden)

Abhilash Ravikumar

2018-03-01

Full Text Available We perform first principle calculations based on density functional theory to investigate the effect of the adsorption of core-excited organic molecules on graphene. We simulate Near Edge X-ray absorption Fine Structure (NEXAFS and X-ray Photoemission Spectroscopy (XPS at the N and C edges for two moieties: pyridine and the pyridine radical on graphene, which exemplify two different adsorption characters. The modifications of molecular and graphene energy levels due to their interplay with the core-level excitation are discussed. We find that upon physisorption of pyridine, the binding energies of graphene close to the adsorption site reduce mildly, and the NEXAFS spectra of the molecule and graphene resemble those of gas phase pyridine and pristine graphene, respectively. However, the chemisorption of the pyridine radical is found to significantly alter these core excited spectra. The C 1s binding energy of the C atom of graphene participating in chemisorption increases by ∼1 eV, and the C atoms of graphene alternate to the adsorption site show a reduction in the binding energy. Analogously, these C atoms also show strong modifications in the NEXAFS spectra. The NEXAFS spectrum of the chemisorbed molecule is also modified as a result of hybridization with and screening by graphene. We eventually explore the electronic properties and magnetism of the system as a core-level excitation is adiabatically switched on.

Polar transport in plants mediated by membrane transporters: focus on mechanisms of polar auxin transport.

Science.gov (United States)

Naramoto, Satoshi

2017-12-01

Directional cell-to-cell transport of functional molecules, called polar transport, enables plants to sense and respond to developmental and environmental signals. Transporters that localize to plasma membranes (PMs) in a polar manner are key components of these systems. PIN-FORMED (PIN) auxin efflux carriers, which are the most studied polar-localized PM proteins, are implicated in the polar transport of auxin that in turn regulates plant development and tropic growth. In this review, the regulatory mechanisms underlying polar localization of PINs, control of auxin efflux activity, and PIN abundance at PMs are considered. Up to date information on polar-localized nutrient transporters that regulate directional nutrient movement from soil into the root vasculature is also discussed. Copyright © 2017 Elsevier Ltd. All rights reserved.

Self-organized pattern formation upon femtosecond laser ablation by circularly polarized light

International Nuclear Information System (INIS)

Varlamova, Olga; Costache, Florenta; Reif, Juergen; Bestehorn, Michael

2006-01-01

Surface ripples generation upon femtosecond laser ablation is attributed to self-organized structure formation from instability. We report that linear arrangements are observed not only for linearly polarized light but also for ablation with circularly polarized light. Long ordered chains of spherical nanoparticles, reminding of bead-strings are almost parallel but exhibit typical non-linear dynamics features such as bifurcations. In a first attempt to understand the self-assembly, we rely on models recently developed for the description of similar structures upon ion beam erosion and for the simulation of instabilities in thin liquid films. Our picture describes an unstable surface layer, non-uniformly eroded through Coulomb repulsion between individual positive charges

Theory of photoelectron spectroscopy for organic molecules and their crystals

Energy Technology Data Exchange (ETDEWEB)

Fujikawa, Takashi, E-mail: tfujikawa@faculty.chiba-u.jp; Niki, Kaori; Sakuma, Hiroto

2015-10-01

Highlights: • Some specific features in photoemission theory from organic solids are reviewed. • Extrinsic and intrinsic effects are discussed. • Photoemission from extended levels is compared with that from core levels. • First principle many-body theories are discussed on the basis of nonequilibrium Green's functions. - Abstract: In this short review we discuss recent progress in photoemission theory for organic molecules and their crystals. We discuss some important features in Keldysh Green's function theory for the photoemission. We briefly discuss many-body aspects in photoemission from core and extended levels. In particular phonon effects are investigated in more detail since organic solids are typically soft where electron–phonon interaction is important. Debye–Waller factor suppresses the interference effects of photoelectron waves which makes ARPES analyses useless, particularly in high energy region.

EU-wide survey of polar organic persistent pollutants in European river waters

International Nuclear Information System (INIS)

Loos, Robert; Gawlik, Bernd Manfred; Locoro, Giovanni; Rimaviciute, Erika; Contini, Serafino; Bidoglio, Giovanni

2009-01-01

This study provides the first EU-wide reconnaissance of the occurrence of polar organic persistent pollutants in European river waters. More than 100 individual water samples from over 100 European rivers from 27 European Countries were analysed for 35 selected compounds, comprising pharmaceuticals, pesticides, PFOS, PFOA, benzotriazoles, hormones, and endocrine disrupters. Around 40 laboratories participated in this sampling exercise. The most frequently and at the highest concentration levels detected compounds were benzotriazole, caffeine, carbamazepine, tolyltriazole, and nonylphenoxy acetic acid (NPE 1 C). Only about 10% of the river water samples analysed could be classified as 'very clean' in terms of chemical pollution. The rivers responsible for the major aqueous emissions of PFOS and PFOA from the European Continent could be identified. For the target compounds chosen, we are proposing 'indicative warning levels' in surface waters, which are (for most compounds) close to the 90th percentile of all water samples analysed. - More than 100 river water samples from 27 European Countries were analysed for 35 selected polar organic contaminants

EU-wide survey of polar organic persistent pollutants in European river waters

Energy Technology Data Exchange (ETDEWEB)

Loos, Robert [European Commission, Joint Research Centre, Institute for Environment and Sustainability, Via Enrico Fermi, 21020 Ispra (Italy)], E-mail: robert.loos@jrc.it; Gawlik, Bernd Manfred; Locoro, Giovanni; Rimaviciute, Erika; Contini, Serafino; Bidoglio, Giovanni [European Commission, Joint Research Centre, Institute for Environment and Sustainability, Via Enrico Fermi, 21020 Ispra (Italy)

2009-02-15

This study provides the first EU-wide reconnaissance of the occurrence of polar organic persistent pollutants in European river waters. More than 100 individual water samples from over 100 European rivers from 27 European Countries were analysed for 35 selected compounds, comprising pharmaceuticals, pesticides, PFOS, PFOA, benzotriazoles, hormones, and endocrine disrupters. Around 40 laboratories participated in this sampling exercise. The most frequently and at the highest concentration levels detected compounds were benzotriazole, caffeine, carbamazepine, tolyltriazole, and nonylphenoxy acetic acid (NPE{sub 1}C). Only about 10% of the river water samples analysed could be classified as 'very clean' in terms of chemical pollution. The rivers responsible for the major aqueous emissions of PFOS and PFOA from the European Continent could be identified. For the target compounds chosen, we are proposing 'indicative warning levels' in surface waters, which are (for most compounds) close to the 90th percentile of all water samples analysed. - More than 100 river water samples from 27 European Countries were analysed for 35 selected polar organic contaminants.

Realization and utilization of a harmonic light scattering experiment to select new molecules with great optical nonlinearity

International Nuclear Information System (INIS)

Dhenaut, Christophe

1995-01-01

Conception of new organic materials for nonlinear optics is generally driven by a molecular engineering approach. The usual technique for determining the quadratic hyper polarizability of designed molecules is the electric field induced second harmonic (EFISH) experiment. However this technique is limited to neutral molecules with a permanent dipole moment. We have realized an harmonic light scattering (HLS) experiment which allow the measurement of any kind of molecules, polar or non polar, neutral or ionic. Using this technique we have been able to demonstrate experimentally the validity of the octupole concept (molecules without dipole moment) which has been proposed recently. We have studied molecules corresponding to various octupolar geometries. Nonlinearities are found to be comparable to those of the best dipolar compounds. We have also investigated other molecular families with different symmetry such as polyenes, sub-phthalocyanines and phthalocyanines by EFISH and HLS techniques. We have confronted results obtained by the two experiments. It appears that these results are not easy to compare, the tensorial components accessible by each experiment being different. The two experiments seems complementary. HLS experiments allow the observation of a quadratic hyper polarizability for centrosymmetric molecules. This surprising observation could be explained by the contribution of a vibration al part to the hyper polarizability measured by HLS (but not present in EFISH). Interpretation of this dynamic process is still in progress. (author) [fr

Quantum switching of π-electron rotations in a nonplanar chiral molecule by using linearly polarized UV laser pulses.

Science.gov (United States)

Mineo, Hirobumi; Yamaki, Masahiro; Teranishi, Yoshiaki; Hayashi, Michitoshi; Lin, Sheng Hsien; Fujimura, Yuichi

2012-09-05

Nonplanar chiral aromatic molecules are candidates for use as building blocks of multidimensional switching devices because the π electrons can generate ring currents with a variety of directions. We employed (P)-2,2'-biphenol because four patterns of π-electron rotations along the two phenol rings are possible and theoretically determine how quantum switching of the π-electron rotations can be realized. We found that each rotational pattern can be driven by a coherent excitation of two electronic states under two conditions: one is the symmetry of the electronic states and the other is their relative phase. On the basis of the results of quantum dynamics simulations, we propose a quantum control method for sequential switching among the four rotational patterns that can be performed by using ultrashort overlapped pump and dump pulses with properly selected relative phases and photon polarization directions. The results serve as a theoretical basis for the design of confined ultrafast switching of ring currents of nonplanar molecules and further current-induced magnetic fluxes of more sophisticated systems.

CARBON DIOXIDE INFLUENCE ON THE THERMAL FORMATION OF COMPLEX ORGANIC MOLECULES IN INTERSTELLAR ICE ANALOGS

Energy Technology Data Exchange (ETDEWEB)

Vinogradoff, V.; Fray, N.; Bouilloud, M.; Cottin, H. [LISA Laboratoire Interuniversitaire des Systèmes Atmosphériques, UMR CNRS 7583, Université Paris Est Créteil (UPEC), Université Paris Diderot (UPD), Institut Pierre Simon Laplace, Labex ESEP, Paris (France); Duvernay, F.; Chiavassa, T., E-mail: vvinogradoff@mnhn.fr [PIIM, Laboratoire de Physique des Interactions Ioniques et Moléculaires, Université Aix-Marseille, UMR CNRS 7345, Marseille (France)

2015-08-20

Interstellar ices are submitted to energetic processes (thermal, UV, and cosmic-ray radiations) producing complex organic molecules. Laboratory experiments aim to reproduce the evolution of interstellar ices to better understand the chemical changes leading to the reaction, formation, and desorption of molecules. In this context, the thermal evolution of an interstellar ice analogue composed of water, carbon dioxide, ammonia, and formaldehyde is investigated. The ice evolution during the warming has been monitored by IR spectroscopy. The formation of hexamethylenetetramine (HMT) and polymethylenimine (PMI) are observed in the organic refractory residue left after ice sublimation. A better understanding of this result is realized with the study of another ice mixture containing methylenimine (a precursor of HMT) with carbon dioxide and ammonia. It appears that carbamic acid, a reaction product of carbon dioxide and ammonia, plays the role of catalyst, allowing the reactions toward HMT and PMI formation. This is the first time that such complex organic molecules (HMT, PMI) are produced from the warming (without VUV photolysis or irradiation with energetic particles) of abundant molecules observed in interstellar ices (H{sub 2}O, NH{sub 3}, CO{sub 2}, H{sub 2}CO). This result strengthens the importance of thermal reactions in the ices’ evolution. HMT and PMI, likely components of interstellar ices, should be searched for in the pristine objects of our solar system, such as comets and carbonaceous chondrites.

CARBON DIOXIDE INFLUENCE ON THE THERMAL FORMATION OF COMPLEX ORGANIC MOLECULES IN INTERSTELLAR ICE ANALOGS

International Nuclear Information System (INIS)

Vinogradoff, V.; Fray, N.; Bouilloud, M.; Cottin, H.; Duvernay, F.; Chiavassa, T.

2015-01-01

Interstellar ices are submitted to energetic processes (thermal, UV, and cosmic-ray radiations) producing complex organic molecules. Laboratory experiments aim to reproduce the evolution of interstellar ices to better understand the chemical changes leading to the reaction, formation, and desorption of molecules. In this context, the thermal evolution of an interstellar ice analogue composed of water, carbon dioxide, ammonia, and formaldehyde is investigated. The ice evolution during the warming has been monitored by IR spectroscopy. The formation of hexamethylenetetramine (HMT) and polymethylenimine (PMI) are observed in the organic refractory residue left after ice sublimation. A better understanding of this result is realized with the study of another ice mixture containing methylenimine (a precursor of HMT) with carbon dioxide and ammonia. It appears that carbamic acid, a reaction product of carbon dioxide and ammonia, plays the role of catalyst, allowing the reactions toward HMT and PMI formation. This is the first time that such complex organic molecules (HMT, PMI) are produced from the warming (without VUV photolysis or irradiation with energetic particles) of abundant molecules observed in interstellar ices (H 2 O, NH 3 , CO 2 , H 2 CO). This result strengthens the importance of thermal reactions in the ices’ evolution. HMT and PMI, likely components of interstellar ices, should be searched for in the pristine objects of our solar system, such as comets and carbonaceous chondrites

Complex organic molecules toward low-mass and high-mass star forming regions

Science.gov (United States)

Favre, C.; Ceccarelli, C.; Lefloch, B.; Bergin, E.; Carvajal, M.; Brouillet, N.; Despois, D.; Jørgensen, J.; Kleiner, I.

2016-12-01

One of the most important questions in molecular astrophysics is how, when, and where complex organic molecules, COMs (≥ 6 atoms) are formed. In the Interstellar-Earth connection context, could this have a bearing on the origin of life on Earth? Formation mechanisms of COMs, which include potentially prebiotic molecules, are still debated and may include grain-mantle and/or gas-phase chemistry. Understanding the mechanisms that lead to the interstellar molecular complexification, along with the involved physicochemical processes, is mandatory to answer the above questions. In that context, active researches are ongoing in theory, laboratory experiment, chemical modeling and observations. Thanks to recent progress in radioastronomy instrumentation for both single-dish and millimeter array (e.g. Herschel, NOEMA, ALMA), new results have been obtained. I will review some notable results on the detection of COMs, including prebiotic molecules, towards star forming regions.

Isotope-selective high-order interferometry with large organic molecules in free fall

Science.gov (United States)

Rodewald, Jonas; Dörre, Nadine; Grimaldi, Andrea; Geyer, Philipp; Felix, Lukas; Mayor, Marcel; Shayeghi, Armin; Arndt, Markus

2018-03-01

Interferometry in the time domain has proven valuable for matter-wave based measurements. This concept has recently been generalized to cold molecular clusters using short-pulse standing light waves which realized photo-depletion gratings, arranged in a time-domain Talbot–Lau interferometer (OTIMA). Here we extend this idea further to large organic molecules and demonstrate a new scheme to scan the emerging molecular interferogram in position space. The capability of analyzing different isotopes of the same monomer under identical conditions opens perspectives for studying the interference fringe shift as a function of time in gravitational free fall. The universality of OTIMA interferometry allows one to handle a large variety of particles. In our present work, quasi-continuous laser evaporation allows transferring fragile organic molecules into the gas phase, covering more than an order of magnitude in mass between 614 amu and 6509 amu, i.e. 300% more massive than in previous OTIMA experiments. For all masses, we find about 30% fringe visibility.

On structure of some laminated crystals with organic molecules

International Nuclear Information System (INIS)

Volodina, G.F.; Ivanova, V.Ya.; Malinovskij, T.I.

1982-01-01

A survey is made of papers dealing with intercalation of organic molecules into crystals of dihalcogenides of some transition metals (TaS 2 , TiS 2 , NbS 2 , ZrS 2 , TaSe 2 ), variation of their structure and physical properties. Among the used intercalates ammonia, pyridine, aniline and other aromatic amines proved to be most satisfactory from the viewpoint of reaction rate and product stability. A possibility is discussed of intercalation into PbI 2 and CdI 2 crystals that are of the same structural type as dihalcogenides

Acenes, Heteroacenes and Analogous Molecules for Organic Photovoltaic and Field Effect Transistor Applications

Science.gov (United States)

Granger, Devin Benjamin

Polycyclic aromatic hydrocarbons composed of benzenoid rings fused in a linear fashion comprise the class of compounds known as acenes. The structures containing three to six ring fusions are brightly colored and possess band gaps and charge transport efficiencies sufficient for semiconductor applications. These molecules have been investigated throughout the past several decades to assess their optoelectronic properties. The absorption, emission and charge transport properties of this series of molecules has been studied extensively to elucidate structure-property relationships. A wide variety of analogous molecules, incorporating heterocycles in place of benzenoid rings, demonstrate similar properties to the parent compounds and have likewise been investigated. Functionalization of acene compounds by placement of groups around the molecule affects the way in which molecules interact in the solid state, in addition to the energetics of the molecule. The use of electron donating or electron withdrawing groups affects the frontier molecular orbitals and thus affects the optical and electronic gaps of the molecules. The use of bulky side groups such as alkylsilylethynyl groups allows for crystal engineering of molecular aggregates, and changing the volume and dimensions of the alkylsilyl groups affects the intermolecular interactions and thus changes the packing motif. In chapter 2, a series of tetracene and pentacene molecules with strongly electron withdrawing groups is described. The investigation focuses on the change in energetics of the frontier molecular orbitals between the base acene and the nitrile and dicyanovinyl derivatives as well as the differences between the pentacene and tetracene molecules. The differences in close packing motifs through use of bulky alkylsilylethynyl groups is also discussed in relation to electron acceptor material design and bulk heterojunction organic photovoltaic characteristics. Chapter 3 focuses on molecular acceptor and

Polarization Effects in Attosecond Photoelectron Spectroscopy

DEFF Research Database (Denmark)

Baggesen, Jan Conrad; Madsen, Lars Bojer

2010-01-01

following the field instead. We show that polarization effects may lead to an apparent temporal shift that needs to be properly accounted for in the analysis. The effect may be isolated and studied by angle-resolved photoelectron spectroscopy from oriented polar molecules. We also show that polarization...... effects will lead to an apparent temporal shift of 50 as between photoelectrons from a 2p and 1s state in atomic hydrogen....

Quantum coherent π-electron rotations in a non-planar chiral molecule induced by using a linearly polarized UV laser pulse

Science.gov (United States)

Mineo, Hirobumi; Fujimura, Yuichi

2015-06-01

We propose an ultrafast quantum switching method of π-electron rotations, which are switched among four rotational patterns in a nonplanar chiral aromatic molecule (P)-2,2’- biphenol and perform the sequential switching among four rotational patterns which are performed by the overlapped pump-dump laser pulses. Coherent π-electron dynamics are generated by applying the linearly polarized UV pulse laser to create a pair of coherent quasidegenerated excited states. We also plot the time-dependent π-electron ring current, and discussed ring current transfer between two aromatic rings.

Theoretical study on the ground state of the polar alkali-metal-barium molecules: Potential energy curve and permanent dipole moment

International Nuclear Information System (INIS)

Gou, Dezhi; Kuang, Xiaoyu; Gao, Yufeng; Huo, Dongming

2015-01-01

In this paper, we systematically investigate the electronic structure for the 2 Σ + ground state of the polar alkali-metal-alkaline-earth-metal molecules BaAlk (Alk = Li, Na, K, Rb, and Cs). Potential energy curves and permanent dipole moments (PDMs) are determined using power quantum chemistry complete active space self-consistent field and multi-reference configuration interaction methods. Basic spectroscopic constants are derived from ro-vibrational bound state calculation. From the calculations, it is shown that BaK, BaRb, and BaCs molecules have moderate values of PDM at the equilibrium bond distance (BaK:1.62 D, BaRb:3.32 D, and BaCs:4.02 D). Besides, the equilibrium bond length (4.93 Å and 5.19 Å) and dissociation energy (0.1825 eV and 0.1817 eV) for the BaRb and BaCs are also obtained

Incorporation of metal-organic framework HKUST-1 into porous polymer monolithic capillary columns to enhance the chromatographic separation of small molecules.

Science.gov (United States)

Yang, Shengchao; Ye, Fanggui; Lv, Qinghui; Zhang, Cong; Shen, Shufen; Zhao, Shulin

2014-09-19

Metal-organic framework (MOF) HKUST-1 nanoparticles have been incorporated into poly(glycidyl methacrylate-co-ethylene dimethacrylate) (HKUST-1-poly(GMA-co-EDMA)) monoliths to afford stationary phases with enhanced chromatographic performance of small molecules in the reversed phase capillary liquid chromatography. The effect of HKUST-1 nanoparticles in the polymerization mixture on the performance of the monolithic column was explored in detail. While the bare poly(GMA-co-EDMA) monolith exhibited poor resolution (RsHKUST-1 nanoparticles to the polymerization mixture provide high increased resolution (Rs≥1.3) and high efficiency ranged from 16,300 to 44,300plates/m. Chromatographic performance of HKUST-1-poly(GMA-co-EDMA) monolith was demonstrated by separation of various analytes including polycyclic aromatic hydrocarbons, ethylbenzene and styrene, phenols and aromatic acids using a binary polar mobile phase (CH3CN/H2O). The HKUST-1-poly(GMA-co-EDMA) monolith displayed enhanced hydrophobic and π-π interaction characteristics in the reversed phase separation of test analytes compared to the bare poly(GMA-co-EDMA) monolith. The experiment results showed that HKUST-1-poly(GMA-co-EDMA) monoliths are an alternative to enhance the chromatographic separation of small molecules. Copyright © 2014 Elsevier B.V. All rights reserved.

Crystalline self-assembly of organic molecules with metal ions at the air-aqueous solution interface. A grazing incidence X-ray scattering study

DEFF Research Database (Denmark)

Weissbuch, I.; Buller, R.; Kjær, K.

2002-01-01

The advent of intense X-rays from synchrotron sources made possible to probe, at the molecular level, the structural aspects of self-assemblies generated at interfaces. Here we present the two-dimensional (2-D) packing arrangements of two-, three- and multi-component organo-metallic self......-assemblies formed via interfacial reaction at the air-aqueous solution interface, as determined by grazing incidence X-ray diffraction (GIRD) and X-ray specular reflectivity techniques. GIXD yields structural information on the crystalline part of the Langmuir film, including the ions and counterions lateral order...... of metal ions bound to the polar head groups of amphipilic molecules; use of bolaamphiphiles to generate oriented thin films with metal ions arranged in periodic layers; delineation of differences in the lateral organization of metal ions at interfaces as induced by racemates and enantiomerically pure...

Simulation of the adsorption capacity of polar organic compounds and dyes from water onto activated carbons: Model development and validation

Directory of Open Access Journals (Sweden)

Warisa Bunmahotama

2018-03-01

Full Text Available A model approach is developed to simulate the adsorption isotherms of low-molecular-weight polar organic compounds (LMWPOCs, halogenated LMWPOCs, and dye molecules onto activated carbons (AC. The models were based on the Dubinin–Astakhov equation, with the limiting pore volume of adsorbent estimated from the pore size distribution data, and the adsorption affinity of the adsorbate described by the molecular connectivity index. The models were used to simulate the adsorption data of 87 LMWPOCs onto six ACs, 25 halogenated LMWPOCs onto two ACs and 22 dyes onto three ACs. The developed models follow the experimental data fairly well, with errors of 49, 33 and 43% for the tested LMWPOCs, halogenated LMWPOCs, and dyes, respectively. This study shows that the developed model approach may provide a simple means for the estimation of adsorption capacity for LMWPOCs and dyes onto ACs in water.

Extensive TD-DFT Benchmark: Singlet-Excited States of Organic Molecules.

Science.gov (United States)

Jacquemin, Denis; Wathelet, Valérie; Perpète, Eric A; Adamo, Carlo

2009-09-08

Extensive Time-Dependent Density Functional Theory (TD-DFT) calculations have been carried out in order to obtain a statistically meaningful analysis of the merits of a large number of functionals. To reach this goal, a very extended set of molecules (∼500 compounds, >700 excited states) covering a broad range of (bio)organic molecules and dyes have been investigated. Likewise, 29 functionals including LDA, GGA, meta-GGA, global hybrids, and long-range-corrected hybrids have been considered. Comparisons with both theoretical references and experimental measurements have been carried out. On average, the functionals providing the best match with reference data are, one the one hand, global hybrids containing between 22% and 25% of exact exchange (X3LYP, B98, PBE0, and mPW1PW91) and, on the other hand, a long-range-corrected hybrid with a less-rapidly increasing HF ratio, namely LC-ωPBE(20). Pure functionals tend to be less consistent, whereas functionals incorporating a larger fraction of exact exchange tend to underestimate significantly the transition energies. For most treated cases, the M05 and CAM-B3LYP schemes deliver fairly small deviations but do not outperform standard hybrids such as X3LYP or PBE0, at least within the vertical approximation. With the optimal functionals, one obtains mean absolute deviations smaller than 0.25 eV, though the errors significantly depend on the subset of molecules or states considered. As an illustration, PBE0 and LC-ωPBE(20) provide a mean absolute error of only 0.14 eV for the 228 states related to neutral organic dyes but are completely off target for cyanine-like derivatives. On the basis of comparisons with theoretical estimates, it also turned out that CC2 and TD-DFT errors are of the same order of magnitude, once the above-mentioned hybrids are selected.

An Approach Toward Replacing Vanadium: A Single Organic Molecule for the Anode and Cathode of an Aqueous Redox-Flow Battery.

Science.gov (United States)

Janoschka, Tobias; Friebe, Christian; Hager, Martin D; Martin, Norbert; Schubert, Ulrich S

2017-04-01

By combining a viologen unit and a 2,2,6,6-tetramethylpiperidin-1-oxyl (TEMPO) radical in one single combi-molecule, an artificial bipolar redox-active material, 1-(4-(((1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl)oxy)carbonyl)benzyl)-1'-methyl-[4,4'-bipyridine]-1,1'-diium-chloride ( VIOTEMP ), was created that can serve as both the anode (-0.49 V) and cathode (0.67 V vs. Ag/AgCl) in a water-based redox-flow battery. While it mimics the redox states of flow battery metals like vanadium, the novel aqueous electrolyte does not require strongly acidic media and is best operated at pH 4. The electrochemical properties of VIOTEMP were investigated by using cyclic voltammetry, rotating disc electrode experiments, and spectroelectrochemical methods. A redox-flow battery was built and the suitability of the material for both electrodes was demonstrated through a polarity-inversion experiment. Thus, an organic aqueous electrolyte system being safe in case of cross contamination is presented.

Boost Up Carrier Mobility for Ferroelectric Organic Transistor Memory via Buffering Interfacial Polarization Fluctuation

Science.gov (United States)

Sun, Huabin; Wang, Qijing; Li, Yun; Lin, Yen-Fu; Wang, Yu; Yin, Yao; Xu, Yong; Liu, Chuan; Tsukagoshi, Kazuhito; Pan, Lijia; Wang, Xizhang; Hu, Zheng; Shi, Yi

2014-11-01

Ferroelectric organic field-effect transistors (Fe-OFETs) have been attractive for a variety of non-volatile memory device applications. One of the critical issues of Fe-OFETs is the improvement of carrier mobility in semiconducting channels. In this article, we propose a novel interfacial buffering method that inserts an ultrathin poly(methyl methacrylate) (PMMA) between ferroelectric polymer and organic semiconductor layers. A high field-effect mobility (μFET) up to 4.6 cm2 V-1 s-1 is obtained. Subsequently, the programming process in our Fe-OFETs is mainly dominated by the switching between two ferroelectric polarizations rather than by the mobility-determined charge accumulation at the channel. Thus, the ``reading'' and ``programming'' speeds are significantly improved. Investigations show that the polarization fluctuation at semiconductor/insulator interfaces, which affect the charge transport in conducting channels, can be suppressed effectively using our method.

Metal-organic extended 2D structures: Fe-PTCDA on Au(111)

International Nuclear Information System (INIS)

Alvarez, Lucia; Caillard, Renaud; MartIn-Gago, Jose A; Mendez, Javier; Pelaez, Samuel; Serena, Pedro A

2010-01-01

In this work we combine organic molecules of 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA) with iron atoms on an Au (111) substrate in ultra-high vacuum conditions at different temperatures. By means of scanning tunnelling microscopy (STM) we study the formation of stable 2D metal-organic structures. We show that at certain growth conditions (temperature, time and coverage) stable 'ladder-like' nanostructures are obtained. These are the result of connecting together two metal-organic chains through PTCDA molecules placed perpendicularly, as rungs of a ladder. These structures, stable up to 450 K, can be extended in a 2D layer covering the entire surface and presenting different rotation domains. STM images at both polarities show a contrast reversal between the two molecules at the unit cell. By means of density functional theory (DFT) calculations, we confirm the stability of these structures and that their molecular orbitals are placed separately at the different molecules.

Effective inclusion of polarization effects in calculations of the oscillator strengths and transition energies in atoms and molecules using the equation-of-motion method

International Nuclear Information System (INIS)

Glushkov, A.V.; Kol'tsova, N.Yu.

1994-01-01

Equations of motion were solved by a modified method in a quasi-particle representation of the density functional taking into account the most important polarization effects, including the so-called 2p-2h two-particle-two-hole interactions. Based on these calculations, spectroscopic data on energies and oscillator strengths of the helium atom (the test computation), carbon monoxide, nitrogen molecule, and ethylene are presented that refine some previously reported experimental and theoretical results. It is shown that in some cases the inclusion of polarization corrections introduced by 2p-2h effects is of basic importance because it provides up to ∼30% contribution to the energies and oscillator strengths. 23 refs., 5 tabs

Molecular MRI based on hyper-polarized xenon

International Nuclear Information System (INIS)

Tassali, Nawal

2012-01-01

Magnetic Resonance Imaging (MRI) has a high importance in medicine as it enables the observation of the organs inside the body without the use of radiative or invasive techniques. However it is known to suffer from poor sensitivity. To circumvent this limitation, a key solution resides in the use of hyper-polarized species. Among the entities with which we can drastically increase nuclear polarization, xenon has very specific properties through its interactions with its close environment that lead to a wide chemical shift bandwidth. The goal is thus to use it as a tracer. This PhD thesis focuses on the concept of 129 Xe MRI-based sensors for the detection of biological events. In this approach, hyper-polarized xenon is vectorized to biological targets via functionalized host systems, and then localized thanks to fast dedicated MRI sequences. The conception and set-up of a spin-exchange optical pumping device is first described. Then studies about the interaction of the hyper-polarized noble gas with new cryptophanes susceptible to constitute powerful host molecules are detailed. Also the implementation of recent MRI sequences optimized for the transient character of the hyper-polarization and taking profit of the xenon in-out exchange is described. Applications of this approach for the detection of metallic ions and cellular receptors are studied. Finally, our first in vivo results on a small animal model are presented. (author) [fr

Retention of U(VI) onto silica in presence of model organic molecules

International Nuclear Information System (INIS)

Pham, T.T.H.; Mercier-Bion, F.; Drot, R.; Lagarde, G.; Simoni, E.; Lambert, J.

2008-01-01

It is well-known that the organic matter influences the retention of ions onto mineral surfaces. However, the major part of concerned studies implies humic substances and complex solids. Another approach for identifying the sorption mechanisms is possible by studying simpler solids than those present in natural medium. So, silica is chosen as mineral surface because of its abundance in soils and of the presence of Si-O groups in clayey minerals. Uranium (VI) is selected as cation. Simple organic molecules like acetic (one carboxylic group) and oxalic (two carboxylic functions) acids are considered as models of the natural organic matter for understanding their role in the retention of U(VI) onto powders and slides of silica. Binary (organics/silica, U(VI)/silica) and ternary systems (organics/silica/U(VI)) are studied by complementary approaches. Sorption edges as function of pH are obtained by liquid scintillation methods and capillary electrophoresis. Different spectroscopic techniques are used to deduce the interactions between the organic matter and U(VI) sorbed onto the silica whose: Time-Resolved Laser induced Fluorescence Spectroscopy (TRLFS), X-ray Photoelectron Spectroscopy (XPS), Nuclear Microprobe Analysis (NMA). The results of the effect of these model organic molecules onto the U(VI) retention showed a good agreement between the different techniques. Concerning the acetic acid, there are not differences in the sorption percentages of uranyl (see the figure). All these results indicate that the uranyl-acetate complexes stay in the aqueous solution rather than sorbing onto the silica. On the contrary, oxalic acid influences the sorption of U(VI) onto the silica surface. The sorption percentage of U(VI) in the ternary system (oxalic acid/silica/U(VI)) is lower than the binary system (U(VI)/silica) (see the figure). So, the presence of oxalic acid decreases the sorption of U(VI) onto the silica surface. (authors)

Direct visualization of polarization reversal of organic ferroelectric memory transistor by using charge modulated reflectance imaging

Science.gov (United States)

Otsuka, Takako; Taguchi, Dai; Manaka, Takaaki; Iwamoto, Mitsumasa

2017-11-01

By using the charge modulated reflectance (CMR) imaging technique, charge distribution in the pentacene organic field-effect transistor (OFET) with a ferroelectric gate insulator [P(VDF-TrFE)] was investigated in terms of polarization reversal of the P(VDF-TrFE) layer. We studied the polarization reversal process and the carrier spreading process in the OFET channel. The I-V measurement showed a hysteresis behavior caused by the spontaneous polarization of P(VDF-TrFE), but the hysteresis I-V curve changes depending on the applied drain bias, possibly due to the gradual shift of the polarization reversal position in the OFET channel. CMR imaging visualized the gradual shift of the polarization reversal position and showed that the electrostatic field formed by the polarization of P(VDF-TrFE) contributes to hole and electron injection into the pentacene layer and the carrier distribution is significantly dependent on the direction of the polarization. The polarization reversal position in the channel region is governed by the electrostatic potential, and it happens where the potential reaches the coercive voltage of P(VDF-TrFE). The transmission line model developed on the basis of the Maxwell-Wagner effect element analysis well accounts for this polarization reversal process in the OFET channel.

Combining polar organic chemical integrative samplers (POCIS) with toxicity testing to evaluate pesticide mixture effects on natural phototrophic biofilms

International Nuclear Information System (INIS)

Pesce, Stephane; Morin, Soizic; Lissalde, Sophie; Montuelle, Bernard; Mazzella, Nicolas

2011-01-01

Polar organic chemical integrative samplers (POCIS) are valuable tools in passive sampling methods for monitoring polar organic pesticides in freshwaters. Pesticides extracted from the environment using such methods can be used to toxicity tests. This study evaluated the acute effects of POCIS extracts on natural phototrophic biofilm communities. Our results demonstrate an effect of POCIS pesticide mixtures on chlorophyll a fluorescence, photosynthetic efficiency and community structure. Nevertheless, the range of biofilm responses differs according to origin of the biofilms tested, revealing spatial variations in the sensitivity of natural communities in the studied stream. Combining passive sampler extracts with community-level toxicity tests offers promising perspectives for ecological risk assessment. - Research highlights: → Polar organic chemical integrative samplers (POCIS) were used for monitoring polar organic pesticides in a contaminated river. → The acute effects of POCIS extracts were tested on natural phototrophic biofilm communities. → POCIS pesticide mixtures affected chlorophyll a fluorescence, photosynthetic efficiency and community structure. → Biofilm responses differed according to origin of the biofilms tested, revealing variations in the sensitivity of natural communities. → Combining passive sampler extracts with community-level toxicity tests offers promising perspectives for ecological risk assessment. - Pesticide mixtures extracted from POCIS can affect chl a fluorescence, photosynthetic efficiency and community structure of natural biofilms.

On the SIMS Ionization Probability of Organic Molecules.

Science.gov (United States)

Popczun, Nicholas J; Breuer, Lars; Wucher, Andreas; Winograd, Nicholas

2017-06-01

The prospect of improved secondary ion yields for secondary ion mass spectrometry (SIMS) experiments drives innovation of new primary ion sources, instrumentation, and post-ionization techniques. The largest factor affecting secondary ion efficiency is believed to be the poor ionization probability (α + ) of sputtered material, a value rarely measured directly, but estimated to be in some cases as low as 10 -5 . Our lab has developed a method for the direct determination of α + in a SIMS experiment using laser post-ionization (LPI) to detect neutral molecular species in the sputtered plume for an organic compound. Here, we apply this method to coronene (C 24 H 12 ), a polyaromatic hydrocarbon that exhibits strong molecular signal during gas-phase photoionization. A two-dimensional spatial distribution of sputtered neutral molecules is measured and presented. It is shown that the ionization probability of molecular coronene desorbed from a clean film under bombardment with 40 keV C 60 cluster projectiles is of the order of 10 -3 , with some remaining uncertainty arising from laser-induced fragmentation and possible differences in the emission velocity distributions of neutral and ionized molecules. In general, this work establishes a method to estimate the ionization efficiency of molecular species sputtered during a single bombardment event. Graphical Abstract GRAPHICAL ABSTRACT TEXT HERE] -->.

Structure of the Buried Metal-Molecule Interface in Organic Thin Film Devices

DEFF Research Database (Denmark)

Hansen, Christian Rein; Sørensen, Thomas Just; Glyvradal, Magni

2009-01-01

By use of specular X-ray reflectivity (XR) the structure of a metal-covered organic thin film device is measured with angstrom resolution. The model system is a Langmuir-Blodgett (LB) film, sandwiched between a silicon substrate and a top electrode consisting of 25 Å titanium and 100 Å aluminum....... By comparison of XR data for the five-layer Pb2+ arachidate LB film before and after vapor deposition of the Ti/Al top electrode, a detailed account of the structural damage to the organic film at the buried metal-molecule interface is obtained. We find that the organized structure of the two topmost LB layers...

Photoexcitation circular dichroism in chiral molecules

Science.gov (United States)

Beaulieu, S.; Comby, A.; Descamps, D.; Fabre, B.; Garcia, G. A.; Géneaux, R.; Harvey, A. G.; Légaré, F.; Mašín, Z.; Nahon, L.; Ordonez, A. F.; Petit, S.; Pons, B.; Mairesse, Y.; Smirnova, O.; Blanchet, V.

2018-05-01

Chiral effects appear in a wide variety of natural phenomena and are of fundamental importance in science, from particle physics to metamaterials. The standard technique of chiral discrimination—photoabsorption circular dichroism—relies on the magnetic properties of a chiral medium and yields an extremely weak chiral response. Here, we propose and demonstrate an orders of magnitude more sensitive type of circular dichroism in neutral molecules: photoexcitation circular dichroism. This technique does not rely on weak magnetic effects, but takes advantage of the coherent helical motion of bound electrons excited by ultrashort circularly polarized light. It results in an ultrafast chiral response and the efficient excitation of a macroscopic chiral density in an initially isotropic ensemble of randomly oriented chiral molecules. We probe this excitation using linearly polarized laser pulses, without the aid of further chiral interactions. Our time-resolved study of vibronic chiral dynamics opens a way to the efficient initiation, control and monitoring of chiral chemical change in neutral molecules at the level of electrons.

APECS: A Model Organization for Bridging Past to Present and Developing a New Generation of Polar Scientists (Invited)

Science.gov (United States)

Timm, K.; Baeseman, J. L.; Membership, Association Of Polar Early Career Scientists

2010-12-01

One of the greatest legacies of the International Polar Year (IPY) is the creation of APECS, the Association of Polar Early Career Scientists. As a grassroots effort, APECS was proposed, formed, and developed by and for early career polar researchers. While the young investigators who founded APECS had talent, ambition, and the desire to make things happen, partnerships with key organizations and experienced leaders in polar science were essential to provide the funding, leadership, and mentorship that has taken the organization well beyond the IPY and to over 2000 members. In four years, APECS has strived to foster the skills of and develop a group of early career interdisciplinary polar scientists through networking and mentoring among themselves and with senior scientists. Through diverse activities including, panel discussions, career development workshops, online seminars, a comprehensive job listing, formal mentoring, meeting travel support, and the APECS Virtual Poster Session, APECS goal is to support the early career researcher being trained to do the science, to become a well-rounded scientist prepared for 21st century careers in science. As part of that training, APECS members are encouraged to participate in activities and training related to science communication, education, and outreach; working with the media; participating in the science / public policy interface; and working with arctic communities and indigenous peoples. During the IPY, APECS members were guest speakers and presenters on International Polar Day activities; they contributed to resources for education and outreach such as the book: Polar Science and Global Climate: An International Resource for Education and Outreach; and they made connections with educators, community groups, the media through in-person presentations, blogs from the field, videos, and much more. Workshops, panels, and online discussions focusing on these activities helped develop the capacity to conduct such

Imaging and manipulation of a polar molecule on Ag(111)

DEFF Research Database (Denmark)

Lin, R.; Braun, K.F.; Tang, H.

2001-01-01

A scanning tunneling microscope (STM) was applied to image and laterally manipulate isolated phosphangulene molecules on Ag(111) at 6 K. Atomic-resolution images clearly revealed three characteristic types of appearances (three-lobed, fish and bump shape) for the adsorbed molecules, which could...

Localized and guided electroluminescence from roll printed organic nanofibres

DEFF Research Database (Denmark)

Tavares, Luciana; Kjelstrup-Hansen, Jakob; Rubahn, Horst-Günter

2012-01-01

injection of holes and electrons into the organic material with subsequent charge carrier recombination and light emission from a small area near the metal-nanofibre interface. The polarization results from the mutually parallel ordering of the molecular constituents, in which the emitting dipole......Here, we report localized, polarized, and waveguidedelectroluminescence (EL) from well aligned organic nanofibres integrated via roll printing on transistor platforms. The localized emission is due to the application of an AC voltage to the transistor gate electrodes, which causes sequential...... that this scheme can facilitate EL from a nanofibre made from a different type of molecule with altered spectral characteristics. The realization of an electrically biased organic nanoscale light-emitter demonstrates the ability to fabricate on-chip light sources with tunable emission spectrum via synthesis...

Cometary delivery of organic molecules to the early earth

Science.gov (United States)

Chyba, Christopher F.; Thomas, Paul J.; Sagan, Carl; Brookshaw, Leigh

1990-01-01

It has long been speculated that earth accreted prebiotic organic molecules important for the origins of life from impacts of carbonaceous asteroids and comets during the period of heavy bombardment 4.5 x 10 to the 9th to 3.8 x 10 to the 9th years ago. A comprehensive treatment of comet-asteroid interaction with the atmosphere, surface impact, and resulting organic pyrolysis demonstrates that organics will not survive impacts at velocities greater than about 10 kilometers per second and that even comets and asteroids as small as 100 meters in radius cannot be aerobraked to below this velocity in 1-bar atmospheres. However, for plausible dense (10-bar carbon dioxide) early atmospheres, it is found that 4.5 x 10 to the 9th years ago earth was accreting intact cometary organics at a rate of at least about 10 to the 6th to 10 to the 7th kilograms per year, a flux that thereafter declined with a half-life of about 10 to the 8th years. These results may be put in context by comparison with terrestrial oceanic and total biomasses, about 3 x 10 to the 12th kilograms and about 6 x 10 to the 14th kilograms, respectively.

Application of the method of continued fractions for electron scattering by linear molecules

International Nuclear Information System (INIS)

Lee, M.-T.; Iga, I.; Fujimoto, M.M.; Lara, O.; Brasilia Univ., DF

1995-01-01

The method of continued fractions (MCF) of Horacek and Sasakawa is adapted for the first time to study low-energy electron scattering by linear molecules. Particularly, we have calculated the reactance K-matrices for an electron scattered by hydrogen molecule and hydrogen molecular ion as well as by a polar LiH molecule in the static-exchange level. For all the applications studied herein. the calculated physical quantities converge rapidly, even for a strongly polar molecule such as LiH, to the correct values and in most cases the convergence is monotonic. Our study suggests that the MCF could be an efficient method for studying electron-molecule scattering and also photoionization of molecules. (Author)

NMR of insensitive nuclei enhanced by dynamic nuclear polarization.

Science.gov (United States)

Miéville, Pascal; Jannin, Sami; Helm, Lothar; Bodenhausen, Geoffrey

2011-01-01

Despite the powerful spectroscopic information it provides, Nuclear Magnetic Resonance (NMR) spectroscopy suffers from a lack of sensitivity, especially when dealing with nuclei other than protons. Even though NMR can be applied in a straightforward manner when dealing with abundant protons of organic molecules, it is very challenging to address biomolecules in low concentration and/or many other nuclei of the periodic table that do not provide as intense signals as protons. Dynamic Nuclear Polarization (DNP) is an important technique that provides a way to dramatically increase signal intensities in NMR. It consists in transferring the very high electron spin polarization of paramagnetic centers (usually at low temperature) to the surrounding nuclear spins with appropriate microwave irradiation. DNP can lead to an enhancement of the nuclear spin polarization by up to four orders of magnitude. We present in this article some basic concepts of DNP, describe the DNP apparatus at EPFL, and illustrate the interest of the technique for chemical applications by reporting recent measurements of the kinetics of complexation of 89Y by the DOTAM ligand.

Late stage crystallization and healing during spin-coating enhance carrier transport in small-molecule organic semiconductors

KAUST Repository

Chou, Kang Wei; Khan, Hadayat Ullah; Niazi, Muhammad Rizwan; Yan, Buyi; Li, Ruipeng; Payne, Marcia M.; Anthony, John Edward; Smilgies, Detlef Matthias; Amassian, Aram

2014-01-01

Spin-coating is currently the most widely used solution processing method in organic electronics. Here, we report, for the first time, a direct investigation of the formation process of the small-molecule organic semiconductor (OSC) 6,13-bis

Atomic-Resolution Transmission Electron Microscopic Movies for Study of Organic Molecules, Assemblies, and Reactions: The First 10 Years of Development.

Science.gov (United States)

Nakamura, Eiichi

2017-06-20

A molecule is a quantum mechanical entity. "Watching motions and reactions of a molecule with our eyes" has therefore been a dream of chemists for a century. This dream has come true with the aid of the movies of atomic-resolution transmission electron microscopic (AR-TEM) molecular images through real-time observation of dynamic motions of single organic molecules (denoted hereafter as single-molecule atomic-resolution real-time (SMART) TEM imaging). Since 2007, we have reported movies of a variety of single organic molecules, organometallic molecules, and their assemblies, which are rotating, stretching, and reacting. Like movies in the theater, the atomic-resolution molecular movies provide us information on the 3-D structures of the molecules and also their time evolution. The success of the SMART-TEM imaging crucially depends on the development of "chemical fishhooks" with which fish (organic molecules) in solution can be captured on a single-walled carbon nanotube (CNT, serving as a "fishing rod"). The captured molecules are connected to a slowly vibrating CNT, and their motions are displayed on a monitor in real time. A "fishing line" connecting the fish and the rod may be a σ-bond, a van der Waals force, or other weak connections. Here, the molecule/CNT system behaves as a coupled oscillator, where the low-frequency anisotropic vibration of the CNT is transmitted to the molecules via the weak chemical connections that act as an energy filter. Interpretation of the observed motions of the molecules at atomic resolution needs us to consider the quantum mechanical nature of electrons as well as bond rotation, letting us deviate from the conventional statistical world of chemistry. What new horizons can we explore? We have so far carried out conformational studies of individual molecules, assigning anti or gauche conformations to each C-C bond in conformers that we saw. We can also determine the structures of van der Waals assemblies of organic molecules

Searching for Bio-Precursors and Complex Organic Molecules in Space using the GBT

Science.gov (United States)

Cordiner, M.; Charnley, S.; Kisiel, Z.

2012-01-01

Using the latest microwave receiver technology, large organic molecules with abundances as low as approx. 10(exp -11) times that of molecular hydrogen are detectable in cold interstellar clouds via their rotational emission line spectra. We report new observations to search for complex molecules, including molecules of possible pre-biotic importance, using the newly-commissioned Kband focal plane array (KFPA) of the NRAO Robert C. Byrd Green Bank Telescope. Spectra are presented of the dense molecular cloud TMC-1, showing strict upper limits on the level of emission from nitrogen-bearing rings pyrimidine, quinoline and iso-quinoline, carbon-chain oxides C60, C70, HC60 and HC70, and the carbon-chain anion C4H-. The typical RMS brightness temperature noise levels we achieved are approx. 1 mK at around 20 GHz.

Resonance-inclined optical nuclear spin polarization of liquids in diamond structures

Science.gov (United States)

Chen, Q.; Schwarz, I.; Jelezko, F.; Retzker, A.; Plenio, M. B.

2016-02-01

Dynamic nuclear polarization (DNP) of molecules in a solution at room temperature has the potential to revolutionize nuclear magnetic resonance spectroscopy and imaging. The prevalent methods for achieving DNP in solutions are typically most effective in the regime of small interaction correlation times between the electron and nuclear spins, limiting the size of accessible molecules. To solve this limitation, we design a mechanism for DNP in the liquid phase that is applicable for large interaction correlation times. Importantly, while this mechanism makes use of a resonance condition similar to solid-state DNP, the polarization transfer is robust to a relatively large detuning from the resonance due to molecular motion. We combine this scheme with optically polarized nitrogen-vacancy (NV) center spins in nanodiamonds to design a setup that employs optical pumping and is therefore not limited by room temperature electron thermal polarization. We illustrate numerically the effectiveness of the model in a flow cell containing nanodiamonds immobilized in a hydrogel, polarizing flowing water molecules 4700-fold above thermal polarization in a magnetic field of 0.35 T, in volumes detectable by current NMR scanners.

Hydrophilicity and Microsolvation of an Organic Molecule Resolved on the Sub-molecular Level by Scanning Tunneling Microscopy.

Science.gov (United States)

Lucht, Karsten; Loose, Dirk; Ruschmeier, Maximilian; Strotkötter, Valerie; Dyker, Gerald; Morgenstern, Karina

2018-01-26

Low-temperature scanning tunneling microscopy was used to follow the formation of a solvation shell around an adsorbed functionalized azo dye from the attachment of the first water molecule to a fully solvated molecule. Specific functional groups bind initially one water molecule each, which act as anchor points for additional water molecules. Further water attachment occurs in areas close to these functional groups even when the functional groups themselves are already saturated. In contrast, water molecules surround the hydrophobic parts of the molecule only when the two-dimensional solvation shell closes around them. This study thus traces hydrophilic and hydrophobic properties of an organic molecule down to a sub-molecular length scale. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Crystal chemistry of uranyl carboxylate coordination networks obtained in the presence of organic amine molecules

Energy Technology Data Exchange (ETDEWEB)

Mihalcea, Ionut; Henry, Natacha; Loiseau, Thierry [Unite de Catalyse et Chimie du Solide (UCCS) - UMR CNRS 8181, Universite de Lille Nord de France, USTL-ENSCL, Villeneuve d' Ascq (France)

2014-03-15

Three uranyl isophthalates (1,3-bdc) and two uranyl pyromellitates (btec) of coordination-polymer type were hydrothermally synthesized (200 C for 24 h) in the presence of different amine-based molecules [1,3-diaminopropane (dap) or dimethylamine (dma) originating from the in situ decomposition of N,N-dimethylformamide]. (UO{sub 2}){sub 2}(OH){sub 2}(H{sub 2}O)(1,3-bdc).H{sub 2}O (1) is composed of inorganic tetranuclear cores, which are linked to each other through the isophthalato ligand to generate infinite neutral ribbons, which are intercalated by free H{sub 2}O molecules. The compounds (UO{sub 2}){sub 1.5}(H{sub 2}O)(1,3-bdc){sub 2}.0.5H{sub 2}dap.1.5H{sub 2}O (2) and UO{sub 2}(1,3-bdc){sub 1.5}.0.5H{sub 2}dap.2H{sub 2}O (3) consist of discrete uranyl-centered hexagonal bipyramids connected to each other by a ditopic linker to form a single-layer network for 2 or a double-layer network for 3. The protonated diamine molecules are located between the uranyl-organic sheets and balance the negative charge of the layered sub-networks. The phase (UO{sub 2}){sub 2}O(btec).2Hdma.H{sub 2}O (4) presents a 2D structure built up from tetranuclear units, which consist of two central sevenfold coordinated uranium centers and two peripheral eightfold coordinated uranium centers. The connection of the resulting tetramers through the pyromellitate molecules generates an anionic layerlike structure, in which the protonated dimethylammonium species are inserted. The compound UO{sub 2}(btec).2Hdma (5) is also a lamellar coordination polymer, which contains isolated eightfold coordinated uranium cations linked through pyromellitate molecules and intercalated by protonated dimethylammonium species. In both phases 4 and 5, the btec linker has non-bonded carboxyl oxygen atoms, which preferentially interact with the protonated amine molecules through a hydrogen-bond network. The different illustrations show the structural diversity of uranyl-organic coordination polymers with organic

Selective adsorption and release of cationic organic dye molecules on mesoporous borosilicates

International Nuclear Information System (INIS)

Paul, Manidipa; Pal, Nabanita; Bhaumik, Asim

2012-01-01

Mesoporous materials can play a pivotal role as a host material for delivery application to a specific part of a system. In this work we explore the selective adsorption and release of cationic organic dye molecules such as safranine T (ST) and malachite green (MG) on mesoporous borosilicate materials. The mesoporous silica SBA-15 and borosilicate materials (MBS) were prepared using non-ionic surfactant Pluronic P123 as template via evaporation induced self-assembly (EISA) method. After template removal the materials show high surface areas and in some cases ordered mesopores of dimensions ca. 6–7 nm. High surface area, mesoporosity and the presence of heteroatom (boron) help this mesoporous borosilicate material to adsorb high amount of cationic dye molecules at its surface from the respective aqueous solutions. Furthermore, the mesoporous borosilicate samples containing higher percentage adsorbed dyes show excellent release of ST or MG dye in simulated body fluid (SBF) solution at physiological pH = 7.4 and temperature 310 K. The adsorption and release efficiency of mesoporous borosilicate samples are compared with reference boron-free mesoporous pure silica material to understand the nature of adsorbate–adsorbent interaction at the surfaces. - Graphical abstract: Highly ordered 2D-hexagonal mesoporous borosilicate materials have been synthesized by using Pluronic P123 as template. The materials show very good adsorption and release of organic cationic dye molecules under physiological conditions. Highlights: ► Highly ordered 2D-hexagonal mesoporous borosilicate. ► Nonionic Pluoronic P123 templated mesoporous material. ► Adsorption of organic dyes at the mesopore surface. ► Controlled release of dyes under physiological pH and temperature. ► Release of safranine T (ST) and malachite green (MG) dyes in simulated body fluids.

The Effects of Perchlorate and its Precursors on Organic Molecules under Simulated Mars Conditions

Science.gov (United States)

Carrier, B. L.; Beegle, L. W.; Bhartia, R.; Abbey, W. J.

2016-12-01

Perchlorate (ClO4-) was first detected on Mars by the Phoenix Lander in 2008 [1] and has subsequently been detected by Curiosity in Gale Crater [2], in Mars meteorite EETA79001 [3], and has been proposed as a possible explanation for results obtained by Viking [4]. Perchlorate has also been shown to be formed under current Mars conditions via the oxidation of mineral chlorides, further supporting the theory that perchlorate is present globally on Mars [5]. The discovery of perchlorate on Mars has raised important questions about its effects on the survival and detection of organic molecules. Although it has been shown that pyrolysis in the presence of perchlorate results in the alteration or destruction of organic molecules [2, 4], few studies have been conducted on the potential effects of perchlorate and its precursors on organic molecules prior to analysis. Perchlorate is typically inert under Mars temperatures and pressures, but it has been shown to decompose to form reactive oxychlorine species such as chlorite (ClO2-), hypochlorite (ClO-) and chlorine dioxide (ClO2) when exposed to Mars conditions including ionizing radiation [6]. The oxidation of chloride to perchlorate also results in the formation of reactive oxychlorine species such as chlorate (ClO3-) [5]. Here we investigate the effects of perchlorate and its oxychlorine precursors on organic molecules. Experiments are performed in a Mars Simulation Chamber (MSC) capable of reproducing the temperature, pressure, atmospheric composition and UV flux found on Mars. Soil simulants are prepared consisting of Mojave Mars Simulant (MMS) [7] and each organic, as well as varying concentrations of perchlorate and/or chloride salts, and exposed in the MSC. Subsequent to exposure in the MSC samples are leached and the leachate analyzed by HPLC and LC-MS to determine the degree of degradation of the original organic and the identity of any potential decomposition products formed by oxidation or chlorination

Effect of polar surfaces on organic molecular crystals

Science.gov (United States)

Sharia, Onise; Tsyshevskiy, Roman; Kuklja, Maija; University of Maryland College Park Team

Polar oxide materials reveal intriguing opportunities in the field of electronics, superconductivity and nanotechnology. While behavior of polar surfaces has been widely studied on oxide materials and oxide-oxide interfaces, manifestations and properties of polar surfaces in molecular crystals are still poorly understood. Here we discover that the polar catastrophe phenomenon, known on oxides, also takes place in molecular materials as illustrated with an example of cyclotetramethylene tetranitramine (HMX) crystals. We show that the surface charge separation is a feasible compensation mechanism to counterbalance the macroscopic dipole moment and remove the electrostatic instability. We discuss the role of surface charge on degradation of polar surfaces, electrical conductivity, optical band-gap closure and surface metallization. Research is supported by the US ONR (Grants N00014-16-1-2069 and N00014-16-1-2346) and NSF. We used NERSC, XSEDE and MARCC computational resources.

Comparison of the sampling rates and partitioning behaviour of polar and non-polar contaminants in the polar organic chemical integrative sampler and a monophasic mixed polymer sampler for application as an equilibrium passive sampler.

Science.gov (United States)

Jeong, Yoonah; Schäffer, Andreas; Smith, Kilian

2018-06-15

In this work, Oasis HLB® beads were embedded in a silicone matrix to make a single phase passive sampler with a higher affinity for polar and ionisable compounds than silicone alone. The applicability of this mixed polymer sampler (MPS) was investigated for 34 aquatic contaminants (log K OW -0.03 to 6.26) in batch experiments. The influence of flow was investigated by comparing uptake under static and stirred conditions. The sampler characteristics of the MPS was assessed in terms of sampling rates (R S ) and sampler-water partition coefficients (K SW ), and these were compared to those of the polar organic chemical integrative sampler (POCIS) as a reference kinetic passive sampler. The MPS was characterized as an equilibrium sampler for both polar and non-polar compounds, with faster uptake rates and a shorter time to reach equilibrium than the POCIS. Water flow rate impacted sampling rates by up to a factor of 12 when comparing static and stirred conditions. In addition, the relative accumulation of compounds in the polyethersulfone (PES) membranes versus the inner Oasis HLB sorbent was compared for the POCIS, and ranged from <1% to 83% depending on the analyte properties. This is indicative of a potentially significant lag-phase for less polar compounds within POCIS. The findings of this study can be used to quantitatively describe the partitioning and kinetic behaviour of MPS and POCIS for a range of aquatic organic contaminants for application in field sampling. Copyright © 2018 Elsevier B.V. All rights reserved.

Application of terahertz spectroscopy for characterization of biologically active organic molecules in natural environment

Science.gov (United States)

Karaliūnas, Mindaugas; Jakštas, Vytautas; Nasser, Kinan E.; Venckevičius, Rimvydas; Urbanowicz, Andrzej; Kašalynas, Irmantas; Valušis, Gintaras

2016-09-01

In this work, a comparative research of biologically active organic molecules in its natural environment using the terahertz (THz) time domain spectroscopy (TDS) and Fourier transform spectroscopy (FTS) systems is carried out. Absorption coefficient and refractive index of Nicotiana tabacum L. leaves containing nicotine, Cannabis sativa L. leaves containing tetrahydrocannabinol, and Humulu lupulus L. leaves containing α-acids, active organic molecules that obtain in natural environment, were measured in broad frequency range from 0.1 to 13 THz at room temperature. In the spectra of absorption coefficient the features were found to be unique for N. tabacum, C. sativa and H. lupulus. Moreover, those features can be exploited for identification of C. sativa sex and N. tabacum origin. The refractive index can be also used to characterize different species.

Expert systems for structure elucidation of organic molecules by spectral methods

International Nuclear Information System (INIS)

Elyashberg, Mikhail E

1999-01-01

The state-of-the-art of the investigations aimed at creating expert systems for establishing the structure of organic molecules from IR, 1 H and 13 C NMR spectra is analysed. Computer methods used for identification of molecular fragments, generation of their structure and spectra prediction are considered. Principles of the creation of modern expert systems and general strategy of solving structural problems are discussed. The bibliography includes 174 references.

Predicting Complex Organic Molecule Emission from TW Hya

Science.gov (United States)

Vissapragada, Shreyas; Walsh, Catherine

2017-01-01

The Atacama Large Millimeter/submillimeter Array (ALMA) has significantly increased our ability to observe the rich chemical inventory of star and planet formation. ALMA has recently been used to detect CH3OH (methanol) and CH3CN (methyl cyanide) in protoplanetary disks; these molecules may be vital indicators of the complex organic ice reservoir in the comet-forming zone. We have constructed a physiochemical model of TW Hya, a well-studied protoplanetary disk, to explore the different formation mechanisms of complex ices. By running our model through a radiative transfer code and convolving with beam sizes appropriate for ALMA, we have obtained synthetic observations of methanol and methyl cyanide. Here, we compare and comment on these synthetic observations, and provide astrochemical justification for their spatial distributions.

Insights into the effects of solvent properties in graphene based electric double-layer capacitors with organic electrolytes

Science.gov (United States)

Zhang, Shuo; Bo, Zheng; Yang, Huachao; Yang, Jinyuan; Duan, Liangping; Yan, Jianhua; Cen, Kefa

2016-12-01

Organic electrolytes are widely used in electric double-layer capacitors (EDLCs). In this work, the microstructure of planar graphene-based EDLCs with different organic solvents are investigated with molecular dynamics simulations. Results show that an increase of solvent polarity could weaken the accumulation of counter-ions nearby the electrode surface, due to the screen of electrode charges and relatively lower ionic desolvation. It thus suggests that solvents with low polarity could be preferable to yield high EDL capacitance. Meanwhile, the significant effects of the size and structure of solvent molecules are reflected by non-electrostatic molecule-electrode interactions, further influencing the adsorption of solvent molecules on electrode surface. Compared with dimethyl carbonate, γ-butyrolactone, and propylene carbonate, acetonitrile with relatively small-size and linear structure owns weak non-electrostatic interactions, which favors the easy re-orientation of solvent molecules. Moreover, the shift of solvent orientation in surface layer, from parallel orientation to perpendicular orientation relative to the electrode surface, deciphers the solvent twin-peak behavior near negative electrode. The as-obtained insights into the roles of solvent properties on the interplays among particles and electrodes elucidate the solvent influences on the microstructure and capacitive behavior of EDLCs using organic electrolytes.

Molecular orientation in aligned electrospun polyimide nanofibers by polarized FT-IR spectroscopy.

Science.gov (United States)

Yang, Haoqi; Jiang, Shaohua; Fang, Hong; Hu, Xiaowu; Duan, Gaigai; Hou, Haoqing

2018-07-05

Quantitative explanation on the improved mechanical properties of aligned electrospun polyimide (PI) nanofibers as the increased imidization temperatures is highly required. In this work, polarized FT-IR spectroscopy is applied to solve this problem. Based on the polarized FT-IR spectroscopy and the molecular model in the fibers, the length of the repeat unit of PI molecule, the angle between the fiber axis and the symmetric stretching direction of carbonyl group on the imide ring, and the angle between the PI molecular axis and fiber axis are all investigated. The Mark-Howink equation is used to calculate the number-average molar mass of PI molecules. The orientation states of PI molecules in the electrospun nanofibers are studied from the number-average molar mass of PI molecules and the average fiber diameter. Quantitative analysis of the orientation factor of PI molecules in the electrospun nanofibers is performed by polarized FT-IR spectroscopy. Copyright © 2018 Elsevier B.V. All rights reserved.

Xenoendocrine pollutants May Reduce Size of Sexual Organs in East Greenland Polar Bears (Ursus Maritimus)

DEFF Research Database (Denmark)

Sonne, Christian; Leifsson, Pall S.; Dietz, Rune

2006-01-01

.01) and uterine horn length and HCB (p = 0.02). The study suggests thatthere is an impact from xenoendocrine pollutants on the size of East Greenland polar bear genitalia. This may pose a riskto this polar bear subpopulation in the future because of reduced sperm and egg quality/quantity and uterus and penis size......Reproductive organs from 55 male and 44 female East Greenland polar bears were examined to investigate the potential negative impact from organohalogen pollutants (OHCs). Multiple regressions normalizing for age showed a significant inverse relationship between OHCs and testis length and baculum...... length and weight, respectively, and was found in both subadults (dichlorodiphenyl trichloroethanes, dieldrin, chlordanes, hexacyclohexanes, polychlorinated biphenyls (PCBs), and polybrominated diphenyl ethers (PBDEs)) and adults (hexachlorobenzene [HCB]) (all p

Functionalization of nanoparticle titanium dioxide with different bifunctional organic molecules and trimers of transition compounds for obtaining new materials

International Nuclear Information System (INIS)

Rivera Martinez, Maria Cinthya

2012-01-01

Functionalization of titanium dioxide in nanoporous anatase phase is investigated for obtaining new nanomaterials. Functionalizations were performed using two heating methods: the conventional of refluxing heating method and microwave irradiation with bifunctional organic molecules is used to study how to anchor molecules and the change in the wettability of the material. Besides, reactions with organic molecules were performed as the derived from nanoproxene. The growth layer by layer is performed using the bifunctional molecules previous for the immobilization of cobalt trimers. Functionalized molecules were characterized by infrared spectroscopy, X-ray diffraction, contact angle, scanning electron microscopy, x-ray elemental analysis, plasma atomic emission spectroscopy coupled inductively, x-ray photoelectron spectroscopy and thermogravimetric analysis. This type of functionalizations on nanoporous titanium dioxide could potentially improve optical sensitivity and activity of this nanomaterial in the visible region. (author) [es

Near-unity mass accommodation coefficient of organic molecules of varying structure.

Science.gov (United States)

Julin, Jan; Winkler, Paul M; Donahue, Neil M; Wagner, Paul E; Riipinen, Ilona

2014-10-21

Atmospheric aerosol particles have a significant effect on global climate, air quality, and consequently human health. Condensation of organic vapors is a key process in the growth of nanometer-sized particles to climate relevant sizes. This growth is very sensitive to the mass accommodation coefficient α, a quantity describing the vapor uptake ability of the particles, but knowledge on α of atmospheric organics is lacking. In this work, we have determined α for four organic molecules with diverse structural properties: adipic acid, succinic acid, naphthalene, and nonane. The coefficients are studied using molecular dynamics simulations, complemented with expansion chamber measurements. Our results are consistent with α = 1 (indicating nearly perfect accommodation), regardless of the molecular structural properties, the phase state of the bulk condensed phase, or surface curvature. The results highlight the need for experimental techniques capable of resolving the internal structure of nanoparticles to better constrain the accommodation of atmospheric organics.

Functionalized Self-Assembled InAs/GaAs Quantum-Dot Structures Hybridized with Organic Molecules

DEFF Research Database (Denmark)

Chen, Miaoxiang Max; Kobashi, K.; Chen, B.

2010-01-01

Low-dimensional III-V semiconductors have many advantages over other semiconductors; however, they are not particularly stable under physiological conditions. Hybridizing biocompatible organic molecules with advanced optical and electronic semiconductor devices based on quantum dots (QDs...

Experimental and theoretical data on ion-molecule-reactions relevant for plasma modelling

International Nuclear Information System (INIS)

Hansel, A.; Praxmarer, C.; Lindinger, W.

1995-01-01

Despite the fact that the rate coefficients of hundreds of ion-molecule-reactions have been published in the literature, much more data are required for the purpose of plasma modelling. Many ion molecule reactions have rate coefficients, k, as large as the collisional limiting value, k c , i.e. the rate coefficients k c at which ion-neutral collision complexes are formed are close to the actual rate coefficients observed. In the case of the interaction of an ion with a non polar molecule, k c , is determined by the Langevin limiting value k L being typically 10 -9 cm 3 s -1 . However, when ions react with polar molecules k c is predicted by the average dipole orientation (ADO) theory. These classical theories yield accurate rate coefficients at thermal and elevated temperatures for practically all proton transfer as well as for many charge transfer and hydrogen abstraction reactions. The agreement between experimental and calculated values is usually better than ±20% and in the case of proton transfer reactions the agreement seems to be even better as recent investigations have shown. Even the interaction of the permanent ion dipole with non polar and polar neutrals can be taken into account to predict reaction rate coefficients as has been shown very recently in reactions of the highly polar ion ArH 3 + with various neutrals

Dynamic Control of Synaptic Adhesion and Organizing Molecules in Synaptic Plasticity

Energy Technology Data Exchange (ETDEWEB)

Rudenko, Gabby (Texas-MED)

2017-01-01

Synapses play a critical role in establishing and maintaining neural circuits, permitting targeted information transfer throughout the brain. A large portfolio of synaptic adhesion/organizing molecules (SAMs) exists in the mammalian brain involved in synapse development and maintenance. SAMs bind protein partners, formingtrans-complexes spanning the synaptic cleft orcis-complexes attached to the same synaptic membrane. SAMs play key roles in cell adhesion and in organizing protein interaction networks; they can also provide mechanisms of recognition, generate scaffolds onto which partners can dock, and likely take part in signaling processes as well. SAMs are regulated through a portfolio of different mechanisms that affect their protein levels, precise localization, stability, and the availability of their partners at synapses. Interaction of SAMs with their partners can further be strengthened or weakened through alternative splicing, competing protein partners, ectodomain shedding, or astrocytically secreted factors. Given that numerous SAMs appear altered by synaptic activity, in vivo, these molecules may be used to dynamically scale up or scale down synaptic communication. Many SAMs, including neurexins, neuroligins, cadherins, and contactins, are now implicated in neuropsychiatric and neurodevelopmental diseases, such as autism spectrum disorder, schizophrenia, and bipolar disorder and studying their molecular mechanisms holds promise for developing novel therapeutics.

Metal-organic and supramolecular architectures based on mechanically interlocked molecules

Science.gov (United States)

Fernando, Isurika Rosini

The focus of this work is on mechanically interlocked molecules (MIMs), which have unusual physicochemical and mechanical properties with potential applications in nano-scale/molecular devices and high strength materials. Rotaxanes, for example, consist of an axle-like molecule threaded through a wheel-like molecule, with bulky groups at the two ends of the axle preventing the wheel from dissociating. The position of the wheel along the axle can be switched in a controllable and reversible manner by applying external stimuli, a feature that might lead to the next generation of computers. Molecularly woven materials (MWMs), another example of molecules with mechanically interlocked features, are predicted to be unprecedentedly strong while being lightweight and flexible. With the ultimate goal of achieving control over the functioning of molecular devices in the solid state, a variety of pseudorotaxane building blocks were prepared and characterized, including a novel, rare blue-colored motif. The temperature-dependent assembly/disassembly of pseudorotaxanes was exploited for the construction of single-wavelength colorimetric temperature sensors over a 100 °C window. Pseudorotaxanes based on aromatic crown ether wheels and disubstituted 4,4'-bipyridinium axles were converted into rotaxanes upon binding to metal complexes (zinc, cadmium, mercury, copper, cobalt), and the formation of ordered crystalline arrays was studied in the solid state. The columnar organization of pseudorotaxanes by Hg2X6 2-- complexes (X = Cl, Br, I), leading to unprecedented dichroic (blue/red) rotaxane crystals, was demonstrated for the first time. From the crystal structures studied it became apparent that negatively charged metal complexes are needed for successful assembly with the positively charged pseudorotaxane units. To be able to use the more common, positively charged metal ions for rotaxane framework construction, neutral and negatively charged pseudorotaxanes were synthesized

Nanoscale contacts to organic molecules based on layered semiconductor substrates

Energy Technology Data Exchange (ETDEWEB)

Strobel, Sebastian

2009-06-15

This work reports on the integration of organic molecules as nanoelectronic device units on semiconductor substrates. Two novel preparation methods for sub-10-nm separated metal electrodes are presented using current microelectronics process technology. The first method utilises AlGaAs/GaAs heterostructures grown by molecular beam epitaxy (MBE) as mold to create planar metal electrodes employing a newly developed, high resolution nanotransfer printing (nTP) process. The second method uses commercially available Silicon-on-Insulator (SOI) substrates as base material for the fabrication of nanogap electrode devices. This sandwich-like material stack consists of a silicon substrate, a thin silicon oxide layer, and a capping silicon layer on top. Electronic transport measurements verified their excellent electrical properties at liquid helium temperatures. Specifically tailored nanogap devices featured an electrode insulation in the GW range even up to room temperature as well as within aqueous electrolyte solution. Finally, the well defined layer architecture facilitated the fabrication of electrodes with gap separations below-10-nm to be directly bridged by molecules. Approximately 12-nm-long conjugated molecules with extended -electron system were assembled onto the devices from solution. A large conductance gap was observed with a steep increase in current at a bias voltage of V{sub T}{approx}{+-}1.5 V. Theoretical calculations based on density functional theory and non-equilibrium Green's function formalism confirmed the measured non-linear IV-characteristics qualitatively and lead to the conclusion that the conductance gap mainly originates from the oxygen containing linker. Temperature dependent investigations of the conductance indicated a hopping charge transport mechanism through the central part of the molecule for bias voltages near but below V{sub T}. (orig.)

Polar ecosystem dynamics: recovery of communities from organic enrichment in McMurdo Sound, Antarctica.

Science.gov (United States)

Kim, Stacy; Hammerstom, Kamille K; Conlan, Kathleen E; Thurber, Andrew R

2010-12-01

Community structure and diversity are influenced by patterns of disturbance and input of food. In Antarctica, the marine ecosystem undergoes highly seasonal changes in availability of light and in primary production. Near research stations, organic input from human activities can disturb the regular productivity regime with a consistent input of sewage. McMurdo Sound has both high-productivity and low-productivity habitats, thereby providing an ideal test bed for community recovery dynamics under polar conditions. We used experimental manipulations of the subtidal communities to test the hypotheses that (1) benthic communities respond differently to disturbance from organic enrichment versus burial and (2) community response also varies in areas with different natural patterns of food supply. Both in low- and high-food habitats, the strongest community response was to organic enrichment and resulted in dominance of typical organic-enrichment specialists. In habitats with highly seasonal productivity, community response was predictable and recovery was rapid. In habitats with low productivity, community variability was high and caging treatments suggested that inconsistencies were due to patchy impacts by scavengers. In areas normally subject to regular organic enrichment, either from primary production or from further up the food web (defecation by marine mammals), recovery of benthic communities takes only years even in a polar system. However, a low-productivity regime is as common in near shore habitats around the continent; under these conditions, recovery of benthic communities from disturbance is likely to be much slower and follow a variable ecological trajectory.

Charge-Dipole Acceleration of Polar Gas Molecules towards Charged Nanoparticles: Involvement in Powerful Charge-Induced Catalysis of Heterophase Chemical Reactions and Ball Lightning Phenomenon

Directory of Open Access Journals (Sweden)

Oleg Meshcheryakov

2010-01-01

Full Text Available In humid air, the substantial charge-dipole attraction and electrostatic acceleration of surrounding water vapour molecules towards charged combustible nanoparticles cause intense electrostatic hydration and preferential oxidation of these nanoparticles by electrostatically accelerated polar water vapour molecules rather than nonaccelerated nonpolar oxygen gas molecules. Intense electrostatic hydration of charged combustible nanoparticles converts the nanoparticle's oxide-based shells into the hydroxide-based electrolyte shells, transforming these nanoparticles into reductant/air core-shell nanobatteries, periodically short-circuited by intraparticle field and thermionic emission. Partially synchronized electron emission breakdowns within trillions of nanoparticles-nanobatteries turn a cloud of charged nanoparticles-nanobatteries into a powerful radiofrequency aerosol generator. Electrostatic oxidative hydration and charge-catalyzed oxidation of charged combustible nanoparticles also contribute to a self-oscillating thermocycling process of evolution and periodic autoignition of inflammable gases near to the nanoparticle's surface. The described effects might be of interest for the improvement of certain nanotechnological heterophase processes and to better understand ball lightning phenomenon.

Van Der Waals Heterostructures between Small Organic Molecules and Layered Substrates

Directory of Open Access Journals (Sweden)

Han Huang

2016-09-01

Full Text Available Two dimensional atomic crystals, like grapheme (G and molybdenum disulfide (MoS2, exhibit great interest in electronic and optoelectronic applications. The excellent physical properties, such as transparency, semiconductivity, and flexibility, make them compatible with current organic electronics. Here, we review recent progress in the understanding of the interfaces of van der Waals (vdW heterostructures between small organic molecules (pentacene, copper phthalocyanine (CuPc, perylene-3,4,9,10-tetracarboxylic dianhydride (PTCDA, and dioctylbenzothienobenzothiophene (C8-BTBT and layered substrates (G, MoS2 and hexagonal boron nitride (h-BN. The influences of the underlying layered substrates on the molecular arrangement, electronic and vibrational properties will be addressed.

Polar Organic Pollutants in Groundwater: Experimental Approaches to Biodegradation During Subsoil Passage

Directory of Open Access Journals (Sweden)

T.P. Knepper

2002-01-01

Full Text Available A selection of polar organic compounds was investigated for their biodegradation on a laboratory scale fixed-bed bioreactor and the decline of the parent compounds besides the formation of metabolites was monitored. Of particular interest was the investigation into the degradation of pesticides, especially isoproturon (IPU, surfactants and industrial by-products of chemical synthesis. The results from the laboratory degradation experiments are compared to findings in groundwater.

Effect of deuteration on the vibrational spectra of organic molecules

International Nuclear Information System (INIS)

Billes, Ferenc; Endredi, Henrietta; Varady, Balazs

2001-01-01

The stable isotope substitution of organic compounds deforms their vibrational spectra. The modifications of the spectra appear as band shifts and changes in intensities and shapes of the bands. The magnitude of the effect depends on the ratio of the masses of the new and old isotopes and on the atom active position. According to these mentioned reasons large effects can be observed only if hydrogen atoms are substituted. With the effect of the substitution we dealt already in a former lecture. In this lecture we concentrate on the effect of the change of hydrogen to deuterium. We investigate the changes both experimentally and theoretically. There are two possibilities: - the hydrogen atom is in an active position, its interaction with the environment is strong, either it can dissociate or move on the skeleton of the molecule (tautomerism, resonance) and it can build hydrogen bond, (e.g. it is connected to nitrogen and oxygen atoms); - the hydrogen atom is in an indifferent position in the molecule, its interaction with the environment is weak (e.g. it joins carbon atom). When building the hydrogen bond besides the hydrogen donors also acceptors exist, namely, oxygen and nitrogen atoms having non-bonded electron pairs. When comparing the experimental and theoretical (calculated) effects of this type of isotope changes one must take into account that the calculations refer to the isolated molecule while the experimental spectra characterize the compound. The hydrogen bond is a very strong intermolecular interaction and produces tremendous changes in the infrared spectrum of the molecule in comparison to the imagined theoretical spectrum of the molecule. Some bands disappear, appear, or shift and deform drastically. The H/D change diminishes these effects. Of course, these changes entail the shift of several bands. The Raman spectrum is less sensitive to the large dipole moment changes therefore the deuteration effect is there less dramatic. Deuteration of hydrogen

Lifetimes of organic photovoltaics: Design and synthesis of single oligomer molecules in order to study chemical degradation mechanisms

DEFF Research Database (Denmark)

Alstrup, J.; Norrman, K.; Jørgensen, M.

2006-01-01

Degradation mechanisms in organic and polymer photovoltaics are addressed through the study of an organic photovoltaic molecule based on a single phenylene-vinylene-type oligomer molecule. The synthesis of such a model compound with different end-groups is presented that allows for assignment...... of degradation products from different parts of the molecule. Photovoltaic devices with and without C(60) have been prepared and their characteristics under AM1.5 conditions are reported. The degradation of the active phenylene-vinylene compound in darkness and after 20h of illumination were investigated using...... a mass spectrometric technique (time-of-flight secondary ion mass spectrometry) allowing elucidation of the oxidative degradation pathways. (c) 2006 Elsevier B.V. All rights reserved....

Single NdPc2 molecules on surfaces. Adsorption, interaction, and molecular magnetism

International Nuclear Information System (INIS)

Fahrendorf, Sarah

2013-01-01

They have huge potential for application in molecular-spin-transistors, molecular-spinvalves, and molecular quantum computing. SMMs are characterized by high spin ground states with zero-field splitting leading to high relaxation barriers and long relaxation times. A relevant class of molecules are the lanthanide double-decker phthalocyanines (LaPc 2 ) with only one metal atom sandwiched between two organic phthalocyanine (Pc) ligands. For envisaged spintronic applications it is important to understand the interaction between the molecules and the substrate and its influence on the electronic and magnetic properties. The subject of this thesis is the investigation of the adsorbed neodymium double-decker phthalocyanine (NdPc 2 ) by means of low temperature scanning tunneling microscopy and spectroscopy (STM and STS). The molecules are deposited by sublimation onto different substrates. It is observed that a large fraction of the double-decker molecules decomposes during deposition. The decomposition probability strongly depends on the chosen substrate. Therefore it is concluded that the substrate modifies the electronic structure of the molecule leading to a stabilization or destabilization of the molecular entity. Charge transfer from the surface to the molecule is identified as a potential stabilizing mechanism. The electronic and magnetic properties are investigated in detail for adsorbed NdPc 2 molecules on Cu(100). The results of the experimental study are compared to state-of-the-art density functional theory calculations performed by our colleagues from the Peter Gruenberg Institute (PGI-1) at the Forschungszentrum Juelich. Interestingly, the lower Pc ring of the molecule hybridizes intensely with the substrate leading to strong chemisorption of the molecule, while the upper Pc ring keeps its molecular type electronic states, which can be energetically shifted by an external electric field. Importantly, it is possible to get direct access to the spin-polarized

A cryofuge for cold-collision experiments with slow polar molecules

Science.gov (United States)

Wu, Xing; Gantner, Thomas; Koller, Manuel; Zeppenfeld, Martin; Chervenkov, Sotir; Rempe, Gerhard

2017-11-01

Ultracold molecules represent a fascinating research frontier in physics and chemistry, but it has proven challenging to prepare dense samples at low velocities. Here, we present a solution to this goal by means of a nonconventional approach dubbed cryofuge. It uses centrifugal force to bring cryogenically cooled molecules to kinetic energies below 1 K × kB in the laboratory frame, where kB is the Boltzmann constant, with corresponding fluxes exceeding 1010 per second at velocities below 20 meters per second. By attaining densities higher than 109 per cubic centimeter and interaction times longer than 25 milliseconds in samples of fluoromethane as well as deuterated ammonia, we observed cold dipolar collisions between molecules and determined their collision cross sections.

"Molecules-in-Medicine": Peer-Evaluated Presentations in a Fast-Paced Organic Chemistry Course for Medical Students

Science.gov (United States)

Kadnikova, Ekaterina N.

2013-01-01

To accentuate the importance of organic chemistry in development of contemporary pharmaceuticals, a three-week unit entitled "Molecules-in-Medicine" was included in the curriculum of a comprehensive one-semester four-credit organic chemistry course. After a lecture on medicinal chemistry concepts and pharmaceutical practices, students…

Calamitic Smectic A-Polar Smectic APA Transition Observed in Bent Molecules with Large Bent-Angle Central Core of 4,6-Dichlorobenzene and Alkylthio Terminal Tail

Science.gov (United States)

Nguyen, Ha; Kang, Sungmin; Tokita, Masatoshi; Watanabe, Junji

2011-07-01

New homologs of bent molecules with a large bent-angle central core of 4,6-dichloro benzene and an alkylthio terminal tail have been synthesized. Although the corresponding alkoxy-tail homologs show only the calamitic phases because of its large bent angles around 160°, the new homologs with an alkylthio tail exhibit the antiferroelectric smectic APA (SmAPA) banana phase that is transformed on cooling from the calamitic smectic A (SmA) phase. The biaxial polar packing of bent molecules in the SmAPA phase is considered to arise from the hindered rotation around the molecular long axis due to the expansion of the mesophase temperatures to a lower temperature region. This study indicates that the bent molecules, even with a large bent angle, have the potential to form a switchable banana phase with a remarkable decrease in its phase temperature range to around 60 °C.

The fabrication of small molecule organic light-emitting diode pixels by laser-induced forward transfer

Science.gov (United States)

Shaw-Stewart, J. R. H.; Mattle, T.; Lippert, T. K.; Nagel, M.; Nüesch, F. A.; Wokaun, A.

2013-01-01

Laser-induced forward transfer (LIFT) is a versatile organic light-emitting diode (OLED) pixel deposition process, but has hitherto been applied exclusively to polymeric materials. Here, a modified LIFT process has been used to fabricate small molecule Alq3 organic light-emitting diodes (SMOLEDs). Small molecule thin films are considerably more mechanically brittle than polymeric thin films, which posed significant challenges for LIFT of these materials. The LIFT process presented here uses a polymeric dynamic release layer, a reduced environmental pressure, and a well-defined receiver-donor gap. The Alq3 pixels demonstrate good morphology and functionality, even when compared to conventionally fabricated OLEDs. The Alq3 SMOLED pixel performances show a significant amount of fluence dependence, not observed with polymerical OLED pixels made in previous studies. A layer of tetrabutyl ammonium hydroxide has been deposited on top of the aluminium cathode, as part of the donor substrate, to improve electron injection to the Alq3, by over 600%. These results demonstrate that this variant of LIFT is applicable for the deposition of functional small molecule OLEDs as well as polymeric OLEDs.

Simultaneously improving optical absorption of both transverse-electric polarized and transverse-magnetic polarized light for organic solar cells with Ag grating used as transparent electrode

Directory of Open Access Journals (Sweden)

Yongbing Long

2014-08-01

Full Text Available Theoretical simulations are performed to investigate optical performance of organic solar cells with Ag grating electrode. It is demonstrated that optical absorption for both transverse-electric (TE polarized and transverse-magnetic(TM polarized light is simultaneously improved when compared with that for the device without the Ag grating. The improvement is respectively attributed to the resonance and the surface plasmon polaritons within the device. After an additional WO3 layer is capped on the Ag grating, absorption of TE-polarized light is further improved due to resonance of double microcavities within the device, and absorption of TM-polarized light is improved by the combined effects of the microcavity resonance and the surface plasmon polaritons. Correspondingly, the short current density for randomly polarized light is improved by 18.1% from that of the device without the Ag grating. Finally, it is demonstrated that high transmission may not be an essential prerequisite for metallic gratings when they are used as transparent electrode since absorption loss caused by low transmission can be compensated by using a capping layer to optimize optical resonance of the WMC structure within the device.

Understanding the effects of electronic polarization and delocalization on charge-transport levels in oligoacene systems

KAUST Repository

Sutton, Christopher; Tummala, Naga Rajesh; Kemper, Travis; Aziz, Saadullah G.; Sears, John; Coropceanu, Veaceslav; Bredas, Jean-Luc

2017-01-01

Electronic polarization and charge delocalization are important aspects that affect the charge-transport levels in organic materials. Here, using a quantum mechanical/ embedded-charge (QM/EC) approach based on a combination of the long-range corrected omega B97X-D exchange-correlation functional (QM) and charge model 5 (CM5) point-charge model (EC), we evaluate the vertical detachment energies and polarization energies of various sizes of crystalline and amorphous anionic oligoacene clusters. Our results indicate that QM/EC calculations yield vertical detachment energies and polarization energies that compare well with the experimental values obtained from ultraviolet photoemission spectroscopy measurements. In order to understand the effect of charge delocalization on the transport levels, we considered crystalline naphthalene systems with QM regions including one or five-molecules. The results for these systems show that the delocalization and polarization effects are additive; therefore, allowing for electron delocalization by increasing the size of the QM region leads to the additional stabilization of the transport levels. Published by AIP Publishing.

Understanding the effects of electronic polarization and delocalization on charge-transport levels in oligoacene systems

KAUST Repository

Sutton, Christopher

2017-06-13

Electronic polarization and charge delocalization are important aspects that affect the charge-transport levels in organic materials. Here, using a quantum mechanical/ embedded-charge (QM/EC) approach based on a combination of the long-range corrected omega B97X-D exchange-correlation functional (QM) and charge model 5 (CM5) point-charge model (EC), we evaluate the vertical detachment energies and polarization energies of various sizes of crystalline and amorphous anionic oligoacene clusters. Our results indicate that QM/EC calculations yield vertical detachment energies and polarization energies that compare well with the experimental values obtained from ultraviolet photoemission spectroscopy measurements. In order to understand the effect of charge delocalization on the transport levels, we considered crystalline naphthalene systems with QM regions including one or five-molecules. The results for these systems show that the delocalization and polarization effects are additive; therefore, allowing for electron delocalization by increasing the size of the QM region leads to the additional stabilization of the transport levels. Published by AIP Publishing.

Strong-field ionization of linear molecules by a bicircular laser field: Symmetry considerations

Science.gov (United States)

Gazibegović-Busuladžić, A.; Busuladžić, M.; Hasović, E.; Becker, W.; Milošević, D. B.

2018-04-01

Using the improved molecular strong-field approximation, we investigate (high-order) above-threshold ionization [(H)ATI] of various linear polyatomic molecules by a two-color laser field of frequencies r ω and s ω (with integer numbers r and s ) having coplanar counter-rotating circularly polarized components (a so-called bicircular field). Reflection and rotational symmetries for molecules aligned in the laser-field polarization plane, analyzed for diatomic homonuclear molecules in Phys. Rev. A 95, 033411 (2017), 10.1103/PhysRevA.95.033411, are now considered for diatomic heteronuclear molecules and symmetric and asymmetric linear triatomic molecules. There are additional rotational symmetries for (H)ATI spectra of symmetric linear molecules compared to (H)ATI spectra of the asymmetric ones. It is shown that these symmetries manifest themselves differently for r +s odd and r +s even. For example, HATI spectra for symmetric molecules with r +s even obey inversion symmetry. For ATI spectra of linear molecules, reflection symmetry appears only for certain molecular orientation angles ±90∘-j r 180∘/(r +s ) (j integer). For symmetric linear molecules, reflection symmetry appears also for the angles -j r 180∘/(r +s ) . For perpendicular orientation of molecules with respect to the laser-field polarization plane, the HATI spectra are very similar to those of the atomic targets, i.e., both spectra are characterized by the same type of the (r +s )-fold symmetry.

Intercalation of organic molecules into SnS{sub 2} single crystals

Energy Technology Data Exchange (ETDEWEB)

Toh, M.L.; Tan, K.J.; Wei, F.X.; Zhang, K.K.; Jiang, H. [School of Materials Science and Engineering, Nanyang Technological University, 50 Nanyang Ave., Singapore 639798 (Singapore); Kloc, C., E-mail: ckloc@ntu.edu.sg [School of Materials Science and Engineering, Nanyang Technological University, 50 Nanyang Ave., Singapore 639798 (Singapore)

2013-02-15

SnS{sub 2} is a layered semiconductor with a van der Waals gap separating the covalently bonded layers. In this study, post-synthesis intercalation of donor organic amine molecules, such as ethylenediamine (en), into tin disulfide and secondary intercalation of p-phenylenediamine (PPD) and 1, 5-naphthalenediamine (NDA) into SnS{sub 2e}n have been verified with X-ray diffraction. PPD and NDA did not intercalate directly even during prolonged annealing but replaced en readily if en was already present in the van der Waals gap. The c-lattice dilation is proportional to the intercalant size. Unit cell lattices of intercalated products were determined from the positions of the X-ray diffraction peaks. Optical images taken during the intercalation showed that intercalation progressed from the periphery towards the interior of the crystal. TEM diffraction patterns in the [0 0 1] direction of SnS{sub 2} after intercalation revealed defects and stacking mismatches among the SnS{sub 2} layers caused by the intercalation. UV-Vis absorption studies showed a red shift in the band edge of the SnS{sub 2} material after intercalation. The band edge was 2.2 eV for pristine SnS{sub 2}; after intercalation with en or PPD, the absorbance spectra band edges shifted to approximately 0.7 eV or 0.5 eV, respectively. - Graphical Abstract: SnS{sub 2} single crystals were intercalated with organic amine molecules such as ethylenediamine, phenylenediamine and naphthalenediamine. Absorption studies showed red shift of band edge after intercalation, which was consistent with optical observations. X-ray diffraction indicated lattice dilation in the c-lattice of SnS{sub 2} after intercalation. Highlights: Black-Right-Pointing-Pointer Organic molecules intercalated inhomogenously between covalently bonded SnS{sub 2} layers. Black-Right-Pointing-Pointer Ethylenediamine (en) intercalate directly into SnS{sub 2}. Black-Right-Pointing-Pointer Phenylenediamine (PPD) and naphthalenediamine (NDA) can be

Recent advance in polar seismology: Global impact of the International Polar Year

Science.gov (United States)

Kanao, Masaki; Zhao, Dapeng; Wiens, Douglas A.; Stutzmann, Éléonore

2015-03-01

The most exciting initiative for the recent polar studies was the International Polar Year (IPY) in 2007-2008. The IPY has witnessed a growing community of seismologists who have made considerable efforts to acquire high-quality data in polar regions. It also provided an excellent opportunity to make significant advances in seismic instrumentation of the polar regions to achieve scientific targets involving global issues. Taking these aspects into account, we organize and publish a special issue in Polar Science on the recent advance in polar seismology and cryoseismology as fruitful achievements of the IPY.

Thermochemolysis: A New Sample Preparation Approach for the Detection of Organic Components of Complex Macromolecules in Mars Rocks via Gas Chromatography Mass Spectrometry in SAM on MSL

Science.gov (United States)

Eugenbrode, J.; Glavin, D.; Dworkin, J.; Conrad, P.; Mahaffy, P.

2011-01-01

Organic chemicals, when present in extraterrestrial samples, afford precious insight into past and modern conditions elsewhere in the Solar System . No single technology identifies all molecular components because naturally occurring molecules have different chemistries (e.g., polar vs. non-polar, low to high molecular weight) and interface with the ambient sample chemistry in a variety of modes (i.e., organics may be bonded, absorbed or trapped by minerals, liquids, gases, or other organics). More than 90% of organic matter in most natural samples on Earth and in meteorites is composed of complex macromolecules (e.g. biopolymers, complex biomolecules, humic substances, kerogen) because the processes that tend to break down organic molecules also tend towards complexation of the more recalcitrant components. Thus, methodologies that tap the molecular information contained within macromolecules may be critical to detecting extraterrestrial organic matter and assessing the sources and processes influencing its nature.

Ellipticity and the offset angle of high harmonics generated by homonuclear diatomic molecules

International Nuclear Information System (INIS)

Odzak, S; Milosevic, D B

2011-01-01

In our recent paper (2010 Phys. Rev. A 82 023412) we introduced a theory of high-order harmonic generation by diatomic molecules exposed to an elliptically polarized laser field and have shown that the nth harmonic emission rate has contributions of the components of the T-matrix element in the direction of the laser-field polarization and in the direction perpendicular to it. Using both components of the T-matrix element we now develop a theoretical approach for calculating ellipticity and the offset angle of high harmonics. We show that the emitted harmonics generated by aligned molecules are elliptically polarized even if the applied field is linearly polarized. Using examples of N 2 , O 2 and Ar 2 molecules we show the existence of extrema and sudden changes of the harmonic ellipticity and the offset angle for particular molecular alignment and explain them by the destructive two-centre interference. Taking into account that the aligned molecules are an anisotropic medium for high harmonic generation, we introduce elliptic dichroism as a measure of this anisotropy, for both components of the T-matrix element. We propose that the measurement of the elliptic dichroism may reveal further information about the molecular structure.

Designing small molecule polyaromatic p- and n-type semiconductor materials for organic electronics

KAUST Repository

Collis, Gavin E.

2015-12-22

By combining computational aided design with synthetic chemistry, we are able to identify core 2D polyaromatic small molecule templates with the necessary optoelectronic properties for p- and n-type materials. By judicious selection of the functional groups, we can tune the physical properties of the material making them amenable to solution and vacuum deposition. In addition to solubility, we observe that the functional group can influence the thin film molecular packing. By developing structure-property relationships (SPRs) for these families of compounds we observe that some compounds are better suited for use in organic solar cells, while others, varying only slightly in structure, are favoured in organic field effect transistor devices. We also find that the processing conditions can have a dramatic impact on molecular packing (i.e. 1D vs 2D polymorphism) and charge mobility; this has implications for material and device long term stability. We have developed small molecule p- and n-type materials for organic solar cells with efficiencies exceeding 2%. Subtle variations in the functional groups of these materials produces p- and ntype materials with mobilities higher than 0.3 cm2/Vs. We are also interested in using our SPR approach to develop materials for sensor and bioelectronic applications.

POLAR ORGANIC CHEMICAL INTEGRATIVE SAMPLING ...

Science.gov (United States)

The purpose of the research presented in this paper is two-fold: (1) to demonstrate the 4 coupling of two state-of-the-art techniques: a time-weighted polar organic integrative sampler (POCIS) and micro-liquid chromatography-electrospray/ion trap mass spectrometry (u-LC-6 ES/ITMS); and (2) the assessment of these methodologies in a real-world environment -wastewater effluent - for detecting six drugs (four prescription and two illicit). In the effluent from three wastewater treatment plants (WWTP), azithromycin was detected at concentrations ranging from 15ng/L to 66ng/L, equivalent to the total annual release of 0.4 -4 kg into the receiving waters. Detected and confirmed in the effluent from two WWTPs were two illicit drugs methamphetamine and methylenedioxymethamphetamine (MDMA), at 2ng/L and 0.5ng/L, respectively. While the ecotoxicological significance of drugs in environmental matrices, particularly water, has not been closely examined, it can only be surmised that these substances have the potential to adversely affect biota that are continuously exposed to them even at very low levels. The potential for chronic affects on human health is also unknown, but of increasing concern due to the multi use character of water, particularly in densely populated arid areas. The research focused on in the subtasks is the development and application of state-of the-art technologies to meet the needs of the public, Office of Water, and ORD in the area of Water Quality

Triplet--Triplet Absorption Spectra of Organic Molecules in Condensed Phases

International Nuclear Information System (INIS)

Carmichael, I.; Hug, G.L.

1986-01-01

We present a compilation of spectral parameters associated with triplet--triplet absorption of organic molecules in condensed media. The wavelengths of maximum absorbance and the corresponding extinction coefficients, where known, have been critically evaluated. Other data, for example, lifetimes, energies and energy transfer rates, relevant to the triplet states of these molecules are included by way of comments but have not been subjected to a similar scrutiny. Work in the gas phase has been omitted, as have theoretical studies. We provide an introduction to triplet state processes in solution and solids, developing the conceptual background and offering an historical perspective on the detection and measurement of triplet state absorption. Techniques employed to populate the triplet state are reviewed and the various approaches to the estimation of the extinction coefficient of triplet--triplet absorption are critically discussed. A statistical analysis of the available data is presented and recommendations for a hierarchical choice of extinction coefficients are made. Data collection is expected to be complete through the end of 1984. Compound name, molecular formula and author indexes are appended

Membrane Transport across Polarized Epithelia.

Science.gov (United States)

Garcia-Castillo, Maria Daniela; Chinnapen, Daniel J-F; Lencer, Wayne I

2017-09-01

Polarized epithelial cells line diverse surfaces throughout the body forming selective barriers between the external environment and the internal milieu. To cross these epithelial barriers, large solutes and other cargoes must undergo transcytosis, an endocytic pathway unique to polarized cell types, and significant for the development of cell polarity, uptake of viral and bacterial pathogens, transepithelial signaling, and immunoglobulin transport. Here, we review recent advances in our knowledge of the transcytotic pathway for proteins and lipids. We also discuss briefly the promise of harnessing the molecules that undergo transcytosis as vehicles for clinical applications in drug delivery. Copyright © 2017 Cold Spring Harbor Laboratory Press; all rights reserved.

Investigating organic molecules responsible of auxin-like activity of humic acid fraction extracted from vermicompost

Energy Technology Data Exchange (ETDEWEB)

Scaglia, Barbara, E-mail: barbara.scaglia@unimi.it [Gruppo Ricicla Labs – DiSAA, Università degli Studi di Milano, Via Celoria 2 (Italy); Nunes, Ramom Rachide; Rezende, Maria Olímpia Oliveira [Laboratório de Química Ambiental, Universidade de São Paulo, Instituto de Química de São Carlos, Avenida Trabalhador São Carlense, 400, São Carlos (Brazil); Tambone, Fulvia [Gruppo Ricicla Labs – DiSAA, Università degli Studi di Milano, Via Celoria 2 (Italy); Adani, Fabrizio, E-mail: fabrizio.adani@unimi.it [Gruppo Ricicla Labs – DiSAA, Università degli Studi di Milano, Via Celoria 2 (Italy)

2016-08-15

This work studied the auxin-like activity of humic acids (HA) obtained from vermicomposts produced using leather wastes plus cattle dung at different maturation stages (fresh, stable and mature). Bioassays were performed by testing HA concentrations in the range of 100–6000 mg carbon L{sup −1}. {sup 13}C CPMAS-NMR and GC–MS instrumental methods were used to assess the effect of biological processes and starting organic mixtures on HA composition. Not all HAs showed IAA-like activity and in general, IAA-like activity increased with the length of the vermicomposting process. The presence of leather wastes was not necessary to produce the auxin-like activity of HA, since HA extracted from a mix of cattle manure and sawdust, where no leather waste was added, showed IAA-like activity as well. CPMAS {sup 13}CNMR revealed that HAs were similar independently of the mix used and that the humification process involved the increasing concentration of pre-existing alkali soluble fractions in the biomass. GC/MS allowed the identification of the molecules involved in IAA-like effects: carboxylic acids and amino acids. The concentration of active molecules, rather than their simple presence in HA, determined the bio-stimulating effect, and a good linear regression between auxin-like activity and active stimulating molecules concentration was found (R{sup 2} = − 0.85; p < 0.01, n = 6). - Highlights: • Vermicomposting converts waste into organic fertilizer. • Vermicomposts can have biostimulating effect for the presence of hormone-like molecules. • Auxine-like activity was associated to the vermicompost humic acid fraction (HA). • HA carboxylic acids and amino acids, were reported to act as auxin-like molecules. • A linear regression was found between molecules and auxin-like activity.

Nonlinear Transport in Organic Thin Film Transistors with Soluble Small Molecule Semiconductor.

Science.gov (United States)

Kim, Hyeok; Song, Dong-Seok; Kwon, Jin-Hyuk; Jung, Ji-Hoon; Kim, Do-Kyung; Kim, SeonMin; Kang, In Man; Park, Jonghoo; Tae, Heung-Sik; Battaglini, Nicolas; Lang, Philippe; Horowitz, Gilles; Bae, Jin-Hyuk

2016-03-01

Nonlinear transport is intensively explained through Poole-Frenkel (PF) transport mechanism in organic thin film transistors with solution-processed small molecules, which is, 6,13-bis(triisopropylsilylethynyl) (TIPS) pentacene. We outline a detailed electrical study that identifies the source to drain field dependent mobility. Devices with diverse channel lengths enable the extensive exhibition of field dependent mobility due to thermal activation of carriers among traps.

Fluorescence Polarization Screening Assays for Small Molecule Allosteric Modulators of ABL Kinase Function.

Science.gov (United States)

Grover, Prerna; Shi, Haibin; Baumgartner, Matthew; Camacho, Carlos J; Smithgall, Thomas E

2015-01-01

The ABL protein-tyrosine kinase regulates intracellular signaling pathways controlling diverse cellular processes and contributes to several forms of cancer. The kinase activity of ABL is repressed by intramolecular interactions involving its regulatory Ncap, SH3 and SH2 domains. Small molecules that allosterically regulate ABL kinase activity through its non-catalytic domains may represent selective probes of ABL function. Here we report a screening assay for chemical modulators of ABL kinase activity that target the regulatory interaction of the SH3 domain with the SH2-kinase linker. This fluorescence polarization (FP) assay is based on a purified recombinant ABL protein consisting of the N-cap, SH3 and SH2 domains plus the SH2-kinase linker (N32L protein) and a short fluorescein-labeled probe peptide that binds to the SH3 domain. In assay development experiments, we found that the probe peptide binds to the recombinant ABL N32L protein in vitro, producing a robust FP signal that can be competed with an excess of unlabeled peptide. The FP signal is not observed with control N32L proteins bearing either an inactivating mutation in the SH3 domain or enhanced SH3:linker interaction. A pilot screen of 1200 FDA-approved drugs identified four compounds that specifically reduced the FP signal by at least three standard deviations from the untreated controls. Secondary assays showed that one of these hit compounds, the antithrombotic drug dipyridamole, enhances ABL kinase activity in vitro to a greater extent than the previously described ABL agonist, DPH. Docking studies predicted that this compound binds to a pocket formed at the interface of the SH3 domain and the linker, suggesting that it activates ABL by disrupting this regulatory interaction. These results show that screening assays based on the non-catalytic domains of ABL can identify allosteric small molecule regulators of kinase function, providing a new approach to selective drug discovery for this important

Fluorescence Polarization Screening Assays for Small Molecule Allosteric Modulators of ABL Kinase Function.

Directory of Open Access Journals (Sweden)

Prerna Grover

Full Text Available The ABL protein-tyrosine kinase regulates intracellular signaling pathways controlling diverse cellular processes and contributes to several forms of cancer. The kinase activity of ABL is repressed by intramolecular interactions involving its regulatory Ncap, SH3 and SH2 domains. Small molecules that allosterically regulate ABL kinase activity through its non-catalytic domains may represent selective probes of ABL function. Here we report a screening assay for chemical modulators of ABL kinase activity that target the regulatory interaction of the SH3 domain with the SH2-kinase linker. This fluorescence polarization (FP assay is based on a purified recombinant ABL protein consisting of the N-cap, SH3 and SH2 domains plus the SH2-kinase linker (N32L protein and a short fluorescein-labeled probe peptide that binds to the SH3 domain. In assay development experiments, we found that the probe peptide binds to the recombinant ABL N32L protein in vitro, producing a robust FP signal that can be competed with an excess of unlabeled peptide. The FP signal is not observed with control N32L proteins bearing either an inactivating mutation in the SH3 domain or enhanced SH3:linker interaction. A pilot screen of 1200 FDA-approved drugs identified four compounds that specifically reduced the FP signal by at least three standard deviations from the untreated controls. Secondary assays showed that one of these hit compounds, the antithrombotic drug dipyridamole, enhances ABL kinase activity in vitro to a greater extent than the previously described ABL agonist, DPH. Docking studies predicted that this compound binds to a pocket formed at the interface of the SH3 domain and the linker, suggesting that it activates ABL by disrupting this regulatory interaction. These results show that screening assays based on the non-catalytic domains of ABL can identify allosteric small molecule regulators of kinase function, providing a new approach to selective drug discovery

Polar Lipids of Burkholderia pseudomallei Induce Different Host Immune Responses

Science.gov (United States)

Gonzalez-Juarrero, Mercedes; Mima, Naoko; Trunck, Lily A.; Schweizer, Herbert P.; Bowen, Richard A.; Dascher, Kyle; Mwangi, Waithaka; Eckstein, Torsten M.

2013-01-01

Melioidosis is a disease in tropical and subtropical regions of the world that is caused by Burkholderia pseudomallei. In endemic regions the disease occurs primarily in humans and goats. In the present study, we used the goat as a model to dissect the polar lipids of B. pseudomallei to identify lipid molecules that could be used for adjuvants/vaccines or as diagnostic tools. We showed that the lipidome of B. pseudomallei and its fractions contain several polar lipids with the capacity to elicit different immune responses in goats, namely rhamnolipids and ornithine lipids which induced IFN-γ, whereas phospholipids and an undefined polar lipid induced strong IL-10 secretion in CD4+ T cells. Autologous T cells co-cultured with caprine dendritic cells (cDCs) and polar lipids of B. pseudomallei proliferated and up-regulated the expression of CD25 (IL-2 receptor) molecules. Furthermore, we demonstrated that polar lipids were able to up-regulate CD1w2 antigen expression in cDCs derived from peripheral blood monocytes. Interestingly, the same polar lipids had only little effect on the expression of MHC class II DR antigens in the same caprine dendritic cells. Finally, antibody blocking of the CD1w2 molecules on cDCs resulted in decreased expression for IFN-γ by CD4+ T cells. Altogether, these results showed that polar lipids of B. pseudomallei are recognized by the caprine immune system and that their recognition is primarily mediated by the CD1 antigen cluster. PMID:24260378

Polar lipids of Burkholderia pseudomallei induce different host immune responses.

Directory of Open Access Journals (Sweden)

Mercedes Gonzalez-Juarrero

Full Text Available Melioidosis is a disease in tropical and subtropical regions of the world that is caused by Burkholderia pseudomallei. In endemic regions the disease occurs primarily in humans and goats. In the present study, we used the goat as a model to dissect the polar lipids of B. pseudomallei to identify lipid molecules that could be used for adjuvants/vaccines or as diagnostic tools. We showed that the lipidome of B. pseudomallei and its fractions contain several polar lipids with the capacity to elicit different immune responses in goats, namely rhamnolipids and ornithine lipids which induced IFN-γ, whereas phospholipids and an undefined polar lipid induced strong IL-10 secretion in CD4(+ T cells. Autologous T cells co-cultured with caprine dendritic cells (cDCs and polar lipids of B. pseudomallei proliferated and up-regulated the expression of CD25 (IL-2 receptor molecules. Furthermore, we demonstrated that polar lipids were able to up-regulate CD1w2 antigen expression in cDCs derived from peripheral blood monocytes. Interestingly, the same polar lipids had only little effect on the expression of MHC class II DR antigens in the same caprine dendritic cells. Finally, antibody blocking of the CD1w2 molecules on cDCs resulted in decreased expression for IFN-γ by CD4(+ T cells. Altogether, these results showed that polar lipids of B. pseudomallei are recognized by the caprine immune system and that their recognition is primarily mediated by the CD1 antigen cluster.

Vibronic coupling in ionized organic molecules: structural distortions and chemical reactions

International Nuclear Information System (INIS)

Williams, Ffrancon

2003-01-01

Ionized organic molecules (radical cations) in radiation chemistry are liable to undergo vibronic coupling whenever there is a relatively small energy gap (∼0.5-1.5 eV) between their ground and excited states. As a result of this mixing, the force constant for the symmetry-allowed vibrational mode that couples these states is lowered in the ground state of the radical cation so that deformation can take place more easily along this specific mode. This pseudo-Jahn-Teller effect can then result in a permanent structural distortion of the radical cation relative to the symmetry of the parent neutral molecule. It can also bring about an energetically favored pathway for a facile chemical rearrangement along a reaction coordinate defined by the coupling mode. Examples taken from matrix-isolation studies are used to illustrate these dramatic consequences of vibronic coupling in radical cations. Thus, the bicyclo[2.2.2]oct-2-ene and tetramethylurea radical cations are found to have twisted structures departing from the C 2v symmetry of their parent molecules, while the oxirane and bicyclo[1.1.1]pentane radical cations undergo ring-opening rearrangements along reaction coordinates that correspond to the deformational modes predicted by the pseudo-Jahn-Teller effect

Organic Semiconductors based on Dyes and Color Pigments.

Science.gov (United States)

Gsänger, Marcel; Bialas, David; Huang, Lizhen; Stolte, Matthias; Würthner, Frank

2016-05-01

Organic dyes and pigments constitute a large class of industrial products. The utilization of these compounds in the field of organic electronics is reviewed with particular emphasis on organic field-effect transistors. It is shown that for most major classes of industrial dyes and pigments, i.e., phthalocyanines, perylene and naphthalene diimides, diketopyrrolopyrroles, indigos and isoindigos, squaraines, and merocyanines, charge-carrier mobilities exceeding 1 cm(2) V(-1) s(-1) have been achieved. The most widely investigated molecules due to their n-channel operation are perylene and naphthalene diimides, for which even values close to 10 cm(2) V(-1) s(-1) have been demonstrated. The fact that all of these π-conjugated colorants contain polar substituents leading to strongly quadrupolar or even dipolar molecules suggests that indeed a much larger structural space shows promise for the design of organic semiconductor molecules than was considered in this field traditionally. In particular, because many of these dye and pigment chromophores demonstrate excellent thermal and (photo-)chemical stability in their original applications in dyeing and printing, and are accessible by straightforward synthetic protocols, they bear a particularly high potential for commercial applications in the area of organic electronics. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Probing into hybrid organic-molecule and InAs quantum-dots nanosystem with multistacked dots-in-a-well units

DEFF Research Database (Denmark)

Chen, Miaoxiang Max; Kobashi, Kazufumi

2012-01-01

Hybridizing air-stable organic-molecules with advanced III-V semiconductor quantum-dots (QDs) structures can be utilized to create a new generation of biochemical sensing devices. In order to enhance their optical performances, the active regions in these QDs structures commonly consist of multis......Hybridizing air-stable organic-molecules with advanced III-V semiconductor quantum-dots (QDs) structures can be utilized to create a new generation of biochemical sensing devices. In order to enhance their optical performances, the active regions in these QDs structures commonly consist...

Vibrational emission analysis of the CN molecules in laser-induced breakdown spectroscopy of organic compounds

Energy Technology Data Exchange (ETDEWEB)

Fernández-Bravo, Ángel; Delgado, Tomás; Lucena, Patricia; Laserna, J. Javier, E-mail: laserna@uma.es

2013-11-01

Laser-induced breakdown spectroscopy (LIBS) of organic materials is based on the analysis of atomic and ionic emission lines and on a few molecular bands, the most important being the CN violet system and the C{sub 2} Swan system. This paper is focused in molecular emission of LIBS plasmas based on the CN (B{sup 2}Σ–X{sup 2}Σ) band, one of the strongest emissions appearing in all carbon materials when analyzed in air atmosphere. An analysis of this band with sufficient spectral resolution provides a great deal of information on the molecule, which has revealed that valuable information can be obtained from the plume chemistry and dynamics affecting the excitation mechanisms of the molecules. The vibrational emission of this molecular band has been investigated to establish the dependence of this emission on the molecular structure of the materials. The paper shows that excitation/emission phenomena of molecular species observed in the plume depend strongly on the time interval selected and on the irradiance deposited on the sample surface. Precise time resolved LIBS measurements are needed for the observation of distinctive CN emission. For the organic compounds studied, larger differences in the behavior of the vibrational emission occur at early stages after plasma ignition. Since molecular emission is generally more complex than that involving atomic emission, local plasma conditions as well as plume chemistry may induce changes in vibrational emission of molecules. As a consequence, alterations in the distribution of the emissions occur in terms of relative intensities, being sensitive to the molecular structure of every single material. - Highlights: • Vibrational emission of CN species in laser-induced plasmas has been investigated. • Distribution of vibrational emission of CN has been found to be time dependent. • Laser irradiance affects the vibrational distribution of the CN molecules. • Plume chemistry controls the excitation mechanisms of CN

Larger spontaneous polarization ferroelectric inorganic-organic hybrids: [PbI3](infinity) chains directed organic cations aggregation to Kagomé-shaped tubular architecture.

Science.gov (United States)

Zhao, Hai-Rong; Li, Dong-Ping; Ren, Xiao-Ming; Song, You; Jin, Wan-Qin

2010-01-13

Four isostructural inorganic-organic hybrid ferroelectric compounds, assembled from achiral 3-R-benzylidene-1-aminopyridiniums (R = NO(2), Br, Cl, or F for 1-4, respectively) and [PbI(3)](-) anions with the chiral Kagomé-shaped tubular aggregating architecture, show larger spontaneous polarizations.

Photoelectron angular distributions from strong-field ionization of oriented molecules

DEFF Research Database (Denmark)

Holmegaard, Lotte; Hansen, Jonas Lerche; Kalhøj, Line

2010-01-01

The combination of ultrafast light sources with detection of molecular-frame photoelectron angular distributions (MFPADs) is setting new standards for detailed interrogation of molecular dynamics. However, until recently measurement of MFPADs relied on determining the molecular orientation after...... ionization, which is limited to species and processes where ionization leads to fragmentation. An alternative is to fix the molecular frame before ionization. The only demonstrations of such spatial orientation involved aligned small linear nonpolar molecules. Here we extend these techniques to the general...... class of polar molecules. Carbonylsulphide and benzonitrile molecules, fixed in space by combined laser and electrostatic fields, are ionized with intense, circularly polarized 30-fs laser pulses. For carbonylsulphide and benzonitrile oriented in one dimension, the MFPADs exhibit pronounced anisotropies...

Theoretical Investigations Regarding Single Molecules

DEFF Research Database (Denmark)

Pedersen, Kim Georg Lind

Neoclassical Valence Bond Theory, Quantum Transport, Quantum Interference, Kondo Effect, and Electron Pumping. Trap a single organic molecule between two electrodes and apply a bias voltage across this "molecular junction". When electrons pass through the molecule, the different electron paths can...... interfere destructively or constructively. Destructive interference effects in electron transport could potentially improve thermo-electrics, organic logic circuits and energy harvesting. We have investigated destructive interference in off-resonant transport through organic molecules, and have found a set...

The cell adhesion molecule Fasciclin2 regulates brush border length and organization in Drosophila renal tubules

DEFF Research Database (Denmark)

Halberg, Kenneth Agerlin; Rainey, Stephanie M.; Veland, Iben Rønn

2016-01-01

Multicellular organisms rely on cell adhesion molecules to coordinate cell-cell interactions, and to provide navigational cues during tissue formation. In Drosophila, Fasciclin 2 (Fas2) has been intensively studied due to its role in nervous system development and maintenance; yet, Fas2 is most...... role for this well-known cell adhesion molecule, and propose that Fas2-mediated intermicrovillar homophilic adhesion complexes help stabilize the brush border....

A potentiometric titration method for the crystallization of drug-like organic molecules.

Science.gov (United States)

Du-Cuny, Lei; Huwyler, Jörg; Fischer, Holger; Kansy, Manfred

2007-09-05

It is generally accepted, that crystalline solids representing a low energy polymorph should be selected for development of oral dosage forms. As a consequence, efficient and robust procedures are needed at an early stage during drug discovery to prepare crystals from drug-like organic molecules. In contrast to the use of supersaturated solutions, we present a potentiometric crystallization procedure where saturated solutions are prepared in a controlled manner by pH-titration. Crystallization is carried out under defined conditions using the sample concentration and experimental pK(a) values as input parameters. Crystals of high quality were obtained for 11 drugs selected to demonstrate the efficiency and applicability of the new method. Technical improvements are suggested to overcome practical limitations and to enhance the possibility of obtaining crystals from molecules in their uncharged form.

Formation of highly oxygenated organic molecules from aromatic compounds

Science.gov (United States)

Molteni, Ugo; Bianchi, Federico; Klein, Felix; El Haddad, Imad; Frege, Carla; Rossi, Michel J.; Dommen, Josef; Baltensperger, Urs

2018-02-01

Anthropogenic volatile organic compounds (AVOCs) often dominate the urban atmosphere and consist to a large degree of aromatic hydrocarbons (ArHCs), such as benzene, toluene, xylenes, and trimethylbenzenes, e.g., from the handling and combustion of fuels. These compounds are important precursors for the formation of secondary organic aerosol. Here we show that the oxidation of aromatics with OH leads to a subsequent autoxidation chain reaction forming highly oxygenated molecules (HOMs) with an O : C ratio of up to 1.09. This is exemplified for five single-ring ArHCs (benzene, toluene, o-/m-/p-xylene, mesitylene (1,3,5-trimethylbenzene) and ethylbenzene), as well as two conjugated polycyclic ArHCs (naphthalene and biphenyl). We report the elemental composition of the HOMs and show the differences in the oxidation patterns of these ArHCs. A potential pathway for the formation of these HOMs from aromatics is presented and discussed. We hypothesize that AVOCs may contribute substantially to new particle formation events that have been detected in urban areas.

Formation of highly oxygenated organic molecules from aromatic compounds

Directory of Open Access Journals (Sweden)

U. Molteni

2018-02-01

Full Text Available Anthropogenic volatile organic compounds (AVOCs often dominate the urban atmosphere and consist to a large degree of aromatic hydrocarbons (ArHCs, such as benzene, toluene, xylenes, and trimethylbenzenes, e.g., from the handling and combustion of fuels. These compounds are important precursors for the formation of secondary organic aerosol. Here we show that the oxidation of aromatics with OH leads to a subsequent autoxidation chain reaction forming highly oxygenated molecules (HOMs with an O : C ratio of up to 1.09. This is exemplified for five single-ring ArHCs (benzene, toluene, o-/m-/p-xylene, mesitylene (1,3,5-trimethylbenzene and ethylbenzene, as well as two conjugated polycyclic ArHCs (naphthalene and biphenyl. We report the elemental composition of the HOMs and show the differences in the oxidation patterns of these ArHCs. A potential pathway for the formation of these HOMs from aromatics is presented and discussed. We hypothesize that AVOCs may contribute substantially to new particle formation events that have been detected in urban areas.

Polarization-induced renormalization of molecular levels at metallic and semiconducting surfaces

DEFF Research Database (Denmark)

García Lastra, Juan Maria; Rostgaard, Carsten; Rubio, A.

2009-01-01

On the basis of first-principles G0W0 calculations we systematically study how the electronic levels of a benzene molecule are renormalized by substrate polarization when physisorbed on different metallic and semiconducting surfaces. The polarization-induced reduction in the energy gap between oc...... find that error cancellations lead to remarkably good agreement between the G0W0 and Kohn-Sham energies for the occupied orbitals of the adsorbed molecule....

Single NdPc{sub 2} molecules on surfaces. Adsorption, interaction, and molecular magnetism

Energy Technology Data Exchange (ETDEWEB)

Fahrendorf, Sarah

2013-01-24

They have huge potential for application in molecular-spin-transistors, molecular-spinvalves, and molecular quantum computing. SMMs are characterized by high spin ground states with zero-field splitting leading to high relaxation barriers and long relaxation times. A relevant class of molecules are the lanthanide double-decker phthalocyanines (LaPc{sub 2}) with only one metal atom sandwiched between two organic phthalocyanine (Pc) ligands. For envisaged spintronic applications it is important to understand the interaction between the molecules and the substrate and its influence on the electronic and magnetic properties. The subject of this thesis is the investigation of the adsorbed neodymium double-decker phthalocyanine (NdPc{sub 2}) by means of low temperature scanning tunneling microscopy and spectroscopy (STM and STS). The molecules are deposited by sublimation onto different substrates. It is observed that a large fraction of the double-decker molecules decomposes during deposition. The decomposition probability strongly depends on the chosen substrate. Therefore it is concluded that the substrate modifies the electronic structure of the molecule leading to a stabilization or destabilization of the molecular entity. Charge transfer from the surface to the molecule is identified as a potential stabilizing mechanism. The electronic and magnetic properties are investigated in detail for adsorbed NdPc{sub 2} molecules on Cu(100). The results of the experimental study are compared to state-of-the-art density functional theory calculations performed by our colleagues from the Peter Gruenberg Institute (PGI-1) at the Forschungszentrum Juelich. Interestingly, the lower Pc ring of the molecule hybridizes intensely with the substrate leading to strong chemisorption of the molecule, while the upper Pc ring keeps its molecular type electronic states, which can be energetically shifted by an external electric field. Importantly, it is possible to get direct access to the

Dystroglycan is required for polarizing the epithelial cells and the oocyte in Drosophila

DEFF Research Database (Denmark)

Deng, Wu-Min; Schneider, Martina; Frock, Richard

2003-01-01

The transmembrane protein Dystroglycan is a central element of the dystrophin-associated glycoprotein complex, which is involved in the pathogenesis of many forms of muscular dystrophy. Dystroglycan is a receptor for multiple extracellular matrix (ECM) molecules such as Laminin, agrin and perlecan......, and plays a role in linking the ECM to the actin cytoskeleton; however, how these interactions are regulated and their basic cellular functions are poorly understood. Using mosaic analysis and RNAi in the model organism Drosophila melanogaster, we show that Dystroglycan is required cell......, possibly by organizing the Laminin ECM. These data suggest that the primary function of Dystroglycan in oogenesis is to organize cellular polarity; and this study sets the stage for analyzing the Dystroglycan complex by using the power of Drosophila molecular genetics....

Aligning molecules with intense nonresonant laser fields

DEFF Research Database (Denmark)

Larsen, J.J.; Safvan, C.P.; Sakai, H.

1999-01-01

Molecules in a seeded supersonic beam are aligned by the interaction between an intense nonresonant linearly polarized laser field and the molecular polarizability. We demonstrate the general applicability of the scheme by aligning I2, ICl, CS2, CH3I, and C6H5I molecules. The alignment is probed...... by mass selective two dimensional imaging of the photofragment ions produced by femtosecond laser pulses. Calculations on the degree of alignment of I2 are in good agreement with the experiments. We discuss some future applications of laser aligned molecules....

Labelled molecules, modern research implements

International Nuclear Information System (INIS)

Pichat, L.; Langourieux, Y.

1974-01-01

Details of the synthesis of carbon 14- and tritium-labelled molecules are examined. Although the methods used are those of classical organic chemistry the preparation of carbon 14-labelled molecules differs in some respects, most noticeably in the use of 14 CO 2 which requires very special handling techniques. For the tritium labelling of organic molecules the methods are somewhat different, very often involving exchange reactions. The following are described in turn: the so-called Wilzbach exchange method; exchange by catalysis in solution; catalytic hydrogenation with tritium; reductions with borotritides. Some applications of labelled molecules in organic chemistry, biochemistry and pharmacology are listed [fr

Flotillins are involved in the polarization of primitive and mature hematopoietic cells.

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Lawrence Rajendran

Full Text Available BACKGROUND: Migration of mature and immature leukocytes in response to chemokines is not only essential during inflammation and host defense, but also during development of the hematopoietic system. Many molecules implicated in migratory polarity show uniform cellular distribution under non-activated conditions, but acquire a polarized localization upon exposure to migratory cues. METHODOLOGY/PRINCIPAL FINDINGS: Here, we present evidence that raft-associated endocytic proteins (flotillins are pre-assembled in lymphoid, myeloid and primitive hematopoietic cells and accumulate in the uropod during migration. Furthermore, flotillins display a polarized distribution during immunological synapse formation. Employing the membrane lipid-order sensitive probe Laurdan, we show that flotillin accumulation in the immunological synapse is concomittant with membrane ordering in these regions. CONCLUSIONS: Together with the observation that flotillin polarization does not occur in other polarized cell types such as polarized epithelial cells, our results suggest a specific role for flotillins in hematopoietic cell polarization. Based on our results, we propose that in hematopoietic cells, flotillins provide intrinsic cues that govern segregation of certain microdomain-associated molecules during immune cell polarization.

FRET structure with non-radiative acceptor provided by dye-linker-glass surface complex and single-molecule photodynamics by TIRFM-polarized imaging

International Nuclear Information System (INIS)

Tani, Toshiro; Mashimo, Kei; Suzuki, Tetsu; Horiuchi, Hiromi; Oda, Masaru

2008-01-01

We present our recent study of microscopic single-molecule imaging on the artificial complex of tetramethylrhodamine linked with a propyl chain onto silica glass surface, i.e. an asymmetric fluorescence resonance energy transfer (FRET) structure with non-radiative acceptor. In the synthesis of the complex, we used a mixture of two kinds of isomers to introduce rather small photodynamic difference among them. This isomeric structure change will provide more or less a distinctive photophysical change in e.g. non-radiative relaxation rate. Our recent observation at room temperatures, so far, shows that such contributions can be discriminated in the histograms of the fluorescent spot intensities; broad but distinctive multi-components appear. To identify the isomeric difference as a cause of structures, some configurational assumptions are necessary. One such basic prerequisite is that the transition dipoles of the chromophores should be oriented almost parallel to the glass surface. In order to make clear the modeling, we also provide preliminary experiments on the polarization dependence of the imaging under rotating polarization in epi-illumination

Communication: Permanent dipoles contribute to electric polarization in chiral NMR spectra

International Nuclear Information System (INIS)

Buckingham, A. David

2014-01-01

Nuclear magnetic resonance spectroscopy is blind to chirality because the spectra of a molecule and its mirror image are identical unless the environment is chiral. However, precessing nuclear magnetic moments in chiral molecules in a strong magnetic field induce an electric polarization through the nuclear magnetic shielding polarizability. This effect is equal and opposite for a molecule and its mirror image but is small and has not yet been observed. It is shown that the permanent electric dipole moment of a chiral molecule is partially oriented through the antisymmetric part of the nuclear magnetic shielding tensor, causing the electric dipole to precess with the nuclear magnetic moment and producing a much larger temperature-dependent electric polarization with better prospects of detection

Biotin conjugated organic molecules and proteins for cancer therapy: A review.

Science.gov (United States)

Maiti, Santanu; Paira, Priyankar

2018-02-10

The main transporter for biotin is sodium dependent multivitamin transporter (SMVT), which is overexpressed in various aggressive cancer cell lines such as ovarian (OV 2008, ID8), leukemia (L1210FR), mastocytoma (P815), colon (Colo-26), breast (4T1, JC, MMT06056), renal (RENCA, RD0995), and lung (M109) cancer cell lines. Furthermore, its overexpression was found higher to that of folate receptor. Therefore, biotin demand in the rapidly growing tumors is higher than normal tissues. Several biotin conjugated organic molecules has been reported here for selective delivery of the drug in cancer cell. Biotin conjugated molecules are showing higher fold of cytotoxicity in biotin positive cancer cell lines than the normal cell. Nanoparticles and polymer surface modified drugs and biotin mediated cancer theranostic strategy was highlighted in this review. The cytotoxicity and selectivity of the drug in cancer cells has enhanced after biotin conjugation. Copyright © 2018 Elsevier Masson SAS. All rights reserved.

Cyclodextrin-supported organic matrix for application of MALDI-MS for forensics. Soft-ionization to obtain protonated molecules of low molecular weight compounds

International Nuclear Information System (INIS)

Yonezawa, Tetsu; Asano, Takashi; Fujino, Tatsuya; Nishihara, Hiroshi

2013-01-01

Highlights: ► MALDI-MS applications for drug identification in forensic science is investigated. ► Cyclodextrin-supported organic matrices strongly suppress the obstacle peaks of organic matrix compounds. ► Cyclodextrin-supported organic matrices also suppress the alkali adducted molecule peaks. ► Sugar units of cyclodextrins work for this specific features. - Abstract: A mass measurement technique for detecting low-molecular-weight drugs with a cyclodextrin-supported organic matrix was investigated. By using cyclodextrin-supported 2,4,6-trihydroxyacetophenone (THAP), the matrix-related peaks of drugs were suppressed. The peaks of protonated molecules of the sample and THAP were mainly observed, and small fragments were detected in a few cases. Despite the Na + and K + peaks were observed in the spectrum, Na + or K + adduct sample molecules were undetected, owing to the sugar units of cyclodextrin. The advantages of MALDI-MS with cyclodextrin-supported matrices as an analytical tool for forensic samples are discussed. The suppression of alkali adducted molecules and desorption process are also discussed

Impulsive Laser Induced Alignment of Molecules Dissolved in Helium Nanodroplets

DEFF Research Database (Denmark)

Pentlehner, Dominik; H. Nielsen, Jens; Slenczka, Alkwin

2013-01-01

We show that a 450 fs nonresonant, moderately intense, linearly polarized laser pulse can induce field-free molecular axis alignment of methyliodide (CH3I) molecules dissolved in a helium nanodroplet. Time-resolved measurements reveal rotational dynamics much slower than that of isolated molecules...

Mechanistic Framework for Establishment, Maintenance, and Alteration of Cell Polarity in Plants

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Pankaj Dhonukshe

2012-01-01

Full Text Available Cell polarity establishment, maintenance, and alteration are central to the developmental and response programs of nearly all organisms and are often implicated in abnormalities ranging from patterning defects to cancer. By residing at the distinct plasma membrane domains polar cargoes mark the identities of those domains, and execute localized functions. Polar cargoes are recruited to the specialized membrane domains by directional secretion and/or directional endocytic recycling. In plants, auxin efflux carrier PIN proteins display polar localizations in various cell types and play major roles in directional cell-to-cell transport of signaling molecule auxin that is vital for plant patterning and response programs. Recent advanced microscopy studies applied to single cells in intact plants reveal subcellular PIN dynamics. They uncover the PIN polarity generation mechanism and identified important roles of AGC kinases for polar PIN localization. AGC kinase family members PINOID, WAG1, and WAG2, belonging to the AGC-3 subclass predominantly influence the polar localization of PINs. The emerging mechanism for AGC-3 kinases action suggests that kinases phosphorylate PINs mainly at the plasma membrane after initial symmetric PIN secretion for eventual PIN internalization and PIN sorting into distinct ARF-GEF-regulated polar recycling pathways. Thus phosphorylation status directs PIN translocation to different cell sides. Based on these findings a mechanistic framework evolves that suggests existence of cell side-specific recycling pathways in plants and implicates AGC3 kinases for differential PIN recruitment among them for eventual PIN polarity establishment, maintenance, and alteration.

Matrix effect on hydrogen-atom tunneling of organic molecules in cryogenic solids

International Nuclear Information System (INIS)

Ichikawa, Tsuneki

2000-01-01

Although the tunneling of atoms through potential energy barriers separating the reactant and reaction systems is not paid much attention in organic reactions, this plays an important role in reactions including the transfer of light atoms. Atomic tunneling is especially important for chemical reactions at low temperatures, since the thermal activation of reactant systems is very slow process in comparison with the tunneling. One of the typical reactions of atomic tunneling is hydrogen-atom abstraction from alkanes in cryogenic solids exposed to high-energy radiation. Irradiation of alkane molecules causes the homolytic cleavage of C-H bonds, which results in the pairwise formation of free hydrogen atoms and organic free radicals. Since the activation energies for the abstraction of hydrogen atoms from alkane molecules by free hydrogen atoms are higher than 5 kcal/mol, the lifetime of free hydrogen atoms at 77 K is estimated from the Arrhenius equation of k=vexp(-E a /RT) to be longer than 10 hrs. However, except for solid methane, free hydrogen atoms immediately convert to alkyl radicals even at 4.2 K by hydrogen-atom tunneling from alkane molecules to the free hydrogen atoms. The rate of hydrogen atom tunneling does not necessary increase with decreasing activation energy or the peak height of the potential energy barrier preventing the tunneling. Although the activation energy is the lowest at the tertiary carbon of alkanes, hydrogen atom tunneling from branched alkanes with tertiary carbon at the antepenultimate position of the carbon skeleton is the fastest at the secondary penultimate carbon. Based on our experimental results, we have proposed that the peculiarity of the hydrogen-atom abstraction in cryogenic solids comes from the steric hindrance by matrix molecules to the deformation of alkane molecules from the initial sp 3 to the final sp 2 configurations. The steric hindrance causes the increase of the height of the potential energy barrier for the

Probing strong-field electron-nuclear dynamics of polyatomic molecules using proton motion

International Nuclear Information System (INIS)

Markevitch, Alexei N.; Smith, Stanley M.; Levis, Robert J.; Romanov, Dmitri A.

2007-01-01

Proton ejection during Coulomb explosion is studied for several structure-related organic molecules (anthracene, anthraquinone, and octahydroanthracene) subjected to 800 nm, 60 fs laser pulses at intensities from 0.50 to 4.0x10 14 W cm -2 . The proton kinetic energy distributions are found to be markedly structure specific. The distributions are bimodal for anthracene and octahydroanthracene and trimodal for anthraquinone. Maximum (cutoff) energies of the distributions range from 50 eV for anthracene to 83 eV for anthraquinone. The low-energy mode (∼10 eV) is most pronounced in octahydroanthracene. The dependence of the characteristic features of the distributions on the laser intensity provides insights into molecular specificity of such strong-field phenomena as (i) nonadiabatic charge localization and (ii) field-mediated restructuring of polyatomic molecules polarized by a strong laser field

Lid opening and conformational stability of T1 Lipase is mediated by increasing chain length polar solvents

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Jonathan Maiangwa

2017-05-01

Full Text Available The dynamics and conformational landscape of proteins in organic solvents are events of potential interest in nonaqueous process catalysis. Conformational changes, folding transitions, and stability often correspond to structural rearrangements that alter contacts between solvent molecules and amino acid residues. However, in nonaqueous enzymology, organic solvents limit stability and further application of proteins. In the present study, molecular dynamics (MD of a thermostable Geobacillus zalihae T1 lipase was performed in different chain length polar organic solvents (methanol, ethanol, propanol, butanol, and pentanol and water mixture systems to a concentration of 50%. On the basis of the MD results, the structural deviations of the backbone atoms elucidated the dynamic effects of water/organic solvent mixtures on the equilibrium state of the protein simulations in decreasing solvent polarity. The results show that the solvent mixture gives rise to deviations in enzyme structure from the native one simulated in water. The drop in the flexibility in H2O, MtOH, EtOH and PrOH simulation mixtures shows that greater motions of residues were influenced in BtOH and PtOH simulation mixtures. Comparing the root mean square fluctuations value with the accessible solvent area (SASA for every residue showed an almost correspondingly high SASA value of residues to high flexibility and low SASA value to low flexibility. The study further revealed that the organic solvents influenced the formation of more hydrogen bonds in MtOH, EtOH and PrOH and thus, it is assumed that increased intraprotein hydrogen bonding is ultimately correlated to the stability of the protein. However, the solvent accessibility analysis showed that in all solvent systems, hydrophobic residues were exposed and polar residues tended to be buried away from the solvent. Distance variation of the tetrahedral intermediate packing of the active pocket was not conserved in organic solvent

Employing exciton transfer molecules to increase the lifetime of phosphorescent red organic light emitting diodes

Science.gov (United States)

Lindla, Florian; Boesing, Manuel; van Gemmern, Philipp; Bertram, Dietrich; Keiper, Dietmar; Heuken, Michael; Kalisch, Holger; Jansen, Rolf H.

2011-04-01

The lifetime of phosphorescent red organic light emitting diodes (OLEDs) is investigated employing either N,N'-diphenyl-N,N'-bis(1-naphthylphenyl)-1,1'-biphenyl-4,4'-diamine (NPB), TMM117, or 4,4',4″-tris(N-carbazolyl)-triphenylamine (TCTA) as hole-conducting host material (mixed with an electron conductor). All OLED (organic vapor phase deposition-processed) show similar efficiencies around 30 lm/W but strongly different lifetimes. Quickly degrading OLED based on TCTA can be stabilized by doping exciton transfer molecules [tris-(phenyl-pyridyl)-Ir (Ir(ppy)3)] to the emission layer. At a current density of 50 mA/cm2 (12 800 cd/m2), a lifetime of 387 h can be achieved. Employing exciton transfer molecules is suggested to prevent the degradation of the red emission layer in phosphorescent white OLED.

On the nucleation and initial film growth of rod-like organic molecules

Science.gov (United States)

Winkler, Adolf

2016-10-01

In this article, some fundamental topics related to the initial steps of organic film growth are reviewed. General conclusions will be drawn based on experimental results obtained for the film formation of oligophenylene and pentacene molecules on gold and mica substrates. Thin films were prepared via physical vapor deposition under ultrahigh-vacuum conditions and characterized in-situ mainly by thermal desorption spectroscopy, and ex-situ by X-ray diffraction and atomic force microscopy. In this short review article the following topics will be discussed: What are the necessary conditions to form island-like films which are either composed of flat-lying or of standing molecules? Does a wetting layer exist below and in between the islands? What is the reason behind the occasionally observed bimodal island size distribution? Can one describe the nucleation process with the diffusion-limited aggregation model? Do the impinging molecules directly adsorb on the surface or rather via a hot-precursor state? Finally, it will be described how the critical island size can be determined by an independent measurement of the deposition rate dependence of the island density and the capture-zone distribution via a universal relationship.

Carbon-13 nuclear magnetic resonance of strained organic molecules: III estimates of steric effects

International Nuclear Information System (INIS)

Seidl, P.R.; Leal, K.Z.; Costa, V.E.U.; Rio Grande do Sul Univ., Porto Alegre

1985-01-01

A study of cyclic organic molecules using carbon-13 NMR spectroscopy is analysed. The preparation of compounds and the use of norbornyl compounds as a basis for chemical shifts, bicyclic, tricyclic and tetracyclic derivatives are compared. Relevant distances, angles and non-bonded interactions are shown. (M.J.C.) [pt

Modelling Polar Self Assembly

Science.gov (United States)

Olvera de La Cruz, Monica; Sayar, Mehmet; Solis, Francisco J.; Stupp, Samuel I.

2001-03-01

Recent experimental studies in our group have shown that self assembled thin films of noncentrosymmetric supramolecular objects composed of triblock rodcoil molecules exhibit finite polar order. These aggregates have both long range dipolar and short range Ising-like interactions. We study the ground state of a simple model with these competing interactions. We find that the competition between Ising-like and dipolar forces yield a periodic domain structure, which can be controlled by adjusting the force constants and film thickness. When the surface forces are included in the potential, the system exhibits a finite macroscopic polar order.

High-resolution internal state control of ultracold 23Na87Rb molecules

Science.gov (United States)

Guo, Mingyang; Ye, Xin; He, Junyu; Quéméner, Goulven; Wang, Dajun

2018-02-01

We report the full internal state control of ultracold 23Na87Rb molecules, including vibrational, rotational, and hyperfine degrees of freedom. Starting from a sample of weakly bound Feshbach molecules, we realize the creation of molecules in single hyperfine levels of both the rovibrational ground and excited states with a high-efficiency and high-resolution stimulated Raman adiabatic passage. This capability brings broad possibilities for investigating ultracold polar molecules with different chemical reactivities and interactions with a single molecular species. Moreover, starting from the rovibrational and hyperfine ground state, we achieve rotational and hyperfine control with one- and two-photon microwave spectroscopy to reach levels not accessible by the stimulated Raman transfer. The combination of these two techniques results in complete control over the internal state of ultracold polar molecules, which paves the way to study state-dependent molecular collisions and state-controlled chemical reactions.

Diffusion as a function of guest molecule length and functionalization in flexible metal–organic frameworks

KAUST Repository

Zheng, B.; Wang, L. L.; Du, L.; Pan, Y.; Lai, Zhiping; Huang, Kuo-Wei; Du, H. L.

2016-01-01

Understanding guest diffusion in nanoporous host-guest systems is crucial in the efficient design of metal-organic frameworks (MOFs) for chemical separation and drug delivery applications. In this work, we investigated the effect of molecule length on the diffusion rate in the zeolitic imidazolate framework 8 (ZIF-8), trying to find a simple and straightforward variable to characterize the complicated guest diffusion. We found that, counter-intuitively, long guest molecules can diffuse as quickly as short molecules; the diffusion coefficient of ethyl acetate for example is of the same order of magnitude as ethane and ethanol, as excludes the existence of a simple relationship between molecule length and diffusion rate. This phenomenon is explained by a study of the contributions of intra- and inter-cage movement to overall transport. Steric confinement limits the degrees of freedom of long guest molecules, shortening their residence time and increasing the efficiency of radial diffusion. In contrast, shorter molecules meander within MOF cages, reducing transport. Furthermore, the energy barrier of inter-cage transport also does not exhibit a simple dependence on a guest molecule length, attributing to the effect of the type of functional group on diffusion. Guests over varying lengths were investigated by using theoretical methods, revealing that the guest diffusion in ZIF-8 depends on the number of contiguous carbon atoms in a molecule, rather than its overall length. Thus, we proposed simple criteria to predict arbitrary guest molecule diffusivity in ZIF-8 without time-consuming experimentation. © 2016 The Royal Society of Chemistry.

Diffusion as a function of guest molecule length and functionalization in flexible metal–organic frameworks

KAUST Repository

Zheng, B.

2016-05-11

Understanding guest diffusion in nanoporous host-guest systems is crucial in the efficient design of metal-organic frameworks (MOFs) for chemical separation and drug delivery applications. In this work, we investigated the effect of molecule length on the diffusion rate in the zeolitic imidazolate framework 8 (ZIF-8), trying to find a simple and straightforward variable to characterize the complicated guest diffusion. We found that, counter-intuitively, long guest molecules can diffuse as quickly as short molecules; the diffusion coefficient of ethyl acetate for example is of the same order of magnitude as ethane and ethanol, as excludes the existence of a simple relationship between molecule length and diffusion rate. This phenomenon is explained by a study of the contributions of intra- and inter-cage movement to overall transport. Steric confinement limits the degrees of freedom of long guest molecules, shortening their residence time and increasing the efficiency of radial diffusion. In contrast, shorter molecules meander within MOF cages, reducing transport. Furthermore, the energy barrier of inter-cage transport also does not exhibit a simple dependence on a guest molecule length, attributing to the effect of the type of functional group on diffusion. Guests over varying lengths were investigated by using theoretical methods, revealing that the guest diffusion in ZIF-8 depends on the number of contiguous carbon atoms in a molecule, rather than its overall length. Thus, we proposed simple criteria to predict arbitrary guest molecule diffusivity in ZIF-8 without time-consuming experimentation. © 2016 The Royal Society of Chemistry.

Study of xenon binding in cryptophane-A using laser-induced NMR polarization enhancement

International Nuclear Information System (INIS)

Luhmer, M.; Goodson, B.M.; Song, Y.Q.; Laws, D.D.; Kaiser, L.; Pines, A.; Lawrence Berkeley National Lab., CA

1999-01-01

Xenon is chemically inert, yet exhibits NMR parameters that are highly sensitive to its chemical environment. Considerable work has therefore capitalized on the utility of 129 Xe (I = 1/2) as a magnetic resonance probe of molecules, materials, and biological systems. In solution, spin-polarization transfer between laser-polarized xenon and the hydrogen nuclei of nearby molecules leads to signal enhancements in the resolved 1 H NMR spectrum, offering new opportunities for probing the chemical environment of xenon atoms. Following binding of laser-polarized xenon to molecules of cryptophane-A, selective enhancements of the 1 H NMR signals were observed. A theoretical framework for the interpretation of such experimental results is provided, and the spin polarization-induced nuclear Overhauser effects are shown to yield information about the molecular environment of xenon. The observed selective 1 H enhancements allowed xenon-proton internuclear distances to be estimated. These distances reveal structural characteristics of the complex, including the preferred molecular conformations adopted by cryptophane-A upon binding of xenon

Intracellular delivery of peptide nucleic acid and organic molecules using zeolite-L nanocrystals.

Science.gov (United States)

Bertucci, Alessandro; Lülf, Henning; Septiadi, Dedy; Manicardi, Alex; Corradini, Roberto; De Cola, Luisa

2014-11-01

The design and synthesis of smart nanomaterials can provide interesting potential applications for biomedical purposes from bioimaging to drug delivery. Manufacturing multifunctional systems in a way to carry bioactive molecules, like peptide nucleic acids able to recognize specific targets in living cells, represents an achievement towards the development of highly selective tools for both diagnosis and therapeutics. This work describes a very first example of the use of zeolite nanocrystals as multifunctional nanocarriers to deliver simultaneously PNA and organic molecules into living cells. Zeolite-L nanocrystals are functionalized by covalently attaching the PNA probes onto the surface, while the channel system is filled with fluorescent guest molecules. The cellular uptake of the PNA/Zeolite-L hybrid material is then significantly increased by coating the whole system with a thin layer of biodegradable poly-L-lysine. The delivery of DAPI as a model drug molecule, inserted into the zeolite pores, is also demonstrated to occur in the cells, proving the multifunctional ability of the system. Using this zeolite nanosystem carrying PNA probes designed to target specific RNA sequences of interest in living cells could open new possibilities for theranostic and gene therapy applications. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Adsorptionof polar organic molecules at oil/water interfaces

Energy Technology Data Exchange (ETDEWEB)

Aveyard, R; Chapman, J

1975-03-15

A study has been made of the adsorption of several esters of dicarboxylic acids at the alkane/water and the air/water interface. The adsorption of n-butanol and n-heptanol at the air/water surface also has been investigated. The surface pressure (pi) -surface area (A) isotherms are compared for the various films, and standard free energies of adsorption have been determined. Attempts have been made to fit the pi, A isotherms using surface equations of state based on the models, of both a 2-dimensional gas and a 2-dimensional solution. The solution model has proved reasonably successful for fairly dilute films at the air/water surface. At higher coverages, an equation derived by Smith for liquid expanded monolayers gives a moderately good description of films of heptanol on water. A simple application of the solution model on adsorbed monolayers at the liquid; liquid interface met with little success. However, it is found that 2-dimensional gas equations describe such systems surprisingly well for fairly low surface concentrations. (20 refs.)

Partition Coefficients of Organic Molecules in Squalane and Water/Ethanol Mixtures by Molecular Dynamics Simulations

DEFF Research Database (Denmark)

Lundsgaard, Rasmus; Kontogeorgis, Georgios; Economou, Ioannis G.

2011-01-01

coefficient can be estimated for both a small hydrophilic and a hydrophobic organic molecules between squalane (used here to mimic low density poly ethylene) and water/ethanol solutes using thermodynamic integration to calculate the free energy of solvation. Molecular dynamics simulations are performed, using...... the GROMACS software, by slowly decoupling of firstly the electrostatic and then the Lennard–Jones interactions between molecules in the simulation box. These calculations depend very much on the choice of force field. Two force fields have been tested in this work, the TraPPE-UA (united-atom) and the OPLS...

Differential Polarization Nonlinear Optical Microscopy with Adaptive Optics Controlled Multiplexed Beams

Directory of Open Access Journals (Sweden)

Virginijus Barzda

2013-09-01

Full Text Available Differential polarization nonlinear optical microscopy has the potential to become an indispensable tool for structural investigations of ordered biological assemblies and microcrystalline aggregates. Their microscopic organization can be probed through fast and sensitive measurements of nonlinear optical signal anisotropy, which can be achieved with microscopic spatial resolution by using time-multiplexed pulsed laser beams with perpendicular polarization orientations and photon-counting detection electronics for signal demultiplexing. In addition, deformable membrane mirrors can be used to correct for optical aberrations in the microscope and simultaneously optimize beam overlap using a genetic algorithm. The beam overlap can be achieved with better accuracy than diffraction limited point-spread function, which allows to perform polarization-resolved measurements on the pixel-by-pixel basis. We describe a newly developed differential polarization microscope and present applications of the differential microscopy technique for structural studies of collagen and cellulose. Both, second harmonic generation, and fluorescence-detected nonlinear absorption anisotropy are used in these investigations. It is shown that the orientation and structural properties of the fibers in biological tissue can be deduced and that the orientation of fluorescent molecules (Congo Red, which label the fibers, can be determined. Differential polarization microscopy sidesteps common issues such as photobleaching and sample movement. Due to tens of megahertz alternating polarization of excitation pulses fast data acquisition can be conveniently applied to measure changes in the nonlinear signal anisotropy in dynamically changing in vivo structures.

New mechanism of semiconductor polarization at the interface with an organic insulator

International Nuclear Information System (INIS)

Yafyasov, A. M.; Bogevolnov, V. B.; Ryumtsev, E. I.; Kovshik, A. P.; Mikhailovski, V. Yu.

2017-01-01

A semiconductor—organic-insulator system with spatially distributed charge is created with a uniquely low density of fast surface states (N_s_s) at the interface. A system with N_s_s ≈ 5 × 10"1"0 cm"–"2 is obtained for the example of n-Ge and the physical characteristics of the interface are measured for this system with liquid and metal field electrodes. For a system with an organic insulator, the range of variation of the surface potential from enrichment of the space-charge region of the semiconductor to the inversion state is first obtained without changing the mechanism of interaction between the adsorbed layer and the semiconductor surface. The effect of enhanced polarization of the space-charge region of the semiconductor occurs due to a change in the spatial structure of mobile charge in the organic dielectric layer. The system developed in the study opens up technological opportunities for the formation of a new generation of electronic devices based on organic film structures and for experimental modeling of the electronic properties of biological membranes.

New mechanism of semiconductor polarization at the interface with an organic insulator

Energy Technology Data Exchange (ETDEWEB)

Yafyasov, A. M., E-mail: yafyasov@gmail.com; Bogevolnov, V. B.; Ryumtsev, E. I.; Kovshik, A. P. [St. Petersburg State University (Russian Federation); Mikhailovski, V. Yu. [Interdisciplinary Resource Center for Nanotechnology at St. Petersburg University (Russian Federation)

2017-02-15

A semiconductor—organic-insulator system with spatially distributed charge is created with a uniquely low density of fast surface states (N{sub ss}) at the interface. A system with N{sub ss} ≈ 5 × 10{sup 10} cm{sup –2} is obtained for the example of n-Ge and the physical characteristics of the interface are measured for this system with liquid and metal field electrodes. For a system with an organic insulator, the range of variation of the surface potential from enrichment of the space-charge region of the semiconductor to the inversion state is first obtained without changing the mechanism of interaction between the adsorbed layer and the semiconductor surface. The effect of enhanced polarization of the space-charge region of the semiconductor occurs due to a change in the spatial structure of mobile charge in the organic dielectric layer. The system developed in the study opens up technological opportunities for the formation of a new generation of electronic devices based on organic film structures and for experimental modeling of the electronic properties of biological membranes.

Peculiarities of spin polarization inversion at a thiophene/cobalt interface

KAUST Repository

Wang, Xuhui; Manchon, Aurelien; Schwingenschlö gl, Udo; Zhu, Zhiyong

2013-01-01

We perform ab initio calculations to investigate the spin polarization at the interface between a thiophene molecule and cobalt substrate. We find that the reduced symmetry in the presence of a sulfur atom (in the thiophene molecule) leads to a

Hyperthermal surface ionization mass spectrometry of organic molecules: monoterpenes

International Nuclear Information System (INIS)

Kishi, Hiroshi; Fujii, Toshihiro.

1997-01-01

This paper describes an experimental study on the influence of kinetic energy of fast monoterpene molecules on the surface ionization efficiency and on the mass spectral patterns, using rhenium oxide (ReO 2 ) surface. Molecular kinetic energy, given to the molecules through the acceleration in the seeded supersonic molecular beam, ranged from 1 to 10 eV. Hyperthermal surface ionization mass spectra (HSIMS) were taken for various incident kinetic energies and surface temperatures. The observed mass spectra were interpreted in a purely empirical way, by means of evidence from the previous investigations, and they were compared with conventional EI techniques and with the thermal energy surface ionization technique (SIOMS; Surface Ionization Organic Mass Spectrometry). Ionization efficiency (β) was also studied. Under hyperthermal surface ionization (HSI) conditions, many kinds of fragment ions, including quite abundant odd electron ions (OE +· ) are observed. HSIMS patterns of monoterpenes are different among 6-isomers, contrary to those of SIOMS and EIMS, where very similar patterns for isomers are observed. HSIMS patterns are strongly dependent on the molecular kinetic energies. The surface temperature does not affect much the spectral patterns, but it controls the total amount of ion formation. We conclude from these mass spectral findings, HSI-mechanism contains an impulsive process of ion formation, followed by the fragmentation process as a results of the internal energies acquired through the collision processes. (author)

Tuning crystal polymorphs of a Π-extended tetrathiafulvalene-based cruciform molecule towards high-performance organic field-effect transistors

DEFF Research Database (Denmark)

Feng, Linlin; Dong, Huanli; Li, Qingyuan

2017-01-01

It is a common phenomenon for organic semiconductors to crystallize in two or more polymorphs, leading to various molecular packings and different charge transport properties. Therefore, it is a crucial issue of tuning molecular crystal polymorphs (i.e., adjusting the same molecule with different......)-based cruciform molecule, named as IF-TTF. The charge carrier mobility of the α-phase IF-TTF crystals was more than one order of magnitude higher than that of β-phase crystals, suggesting the importance of reasonably tuning molecular packing in solid state for the improvement of charge transport in organic...... semiconductors...

Influence of vibrations and rotations of diatomic molecules on their physical properties: II. Refractive index, reactivity and diffusion coefficients

International Nuclear Information System (INIS)

Sharipov, Alexander S; Loukhovitski, Boris I; Starik, Alexander M

2016-01-01

The influence of the excitation of vibrational and rotational states of diatomic molecules (H 2 , N 2 , O 2 , NO, OH, CO, CH, HF and HCl) on refractive index, reactivity and transport coefficients was analyzed by using ab initio calculated data on the effective state-specific dipole moment and static polarizability obtained in the preceding paper of the present series. It has been revealed that, for non-polar molecules, the excitation both of vibrational and rotational degrees of freedom increases the averaged polarizability and, as a consequence, the refractive index. Meanwhile, for polar molecules, the effect of molecule excitation is more complex: it can either increase or decrease the refractive index. It was also shown that the excitation of molecules slightly influences the rate constants of barrierless chemical reactions between neutral particles; whereas, for ion–molecule reactions, this effect can be more pronounced. Analysis of the variation of diffusion coefficients, taking into account the effect of molecule excitation both on the collision diameter and on the well depth of intermolecular potential, exhibited that, for non-polar molecules, the effect associated with the change of collision diameter prevails. However, for polar molecules, the effect of the excitation of vibrational states on the well depth of intermolecular potential can compensate or even exceed the decrease of diffusion coefficient due to the averaged collision diameter rise. (paper)

Cyclodextrin-supported organic matrix for application of MALDI-MS for forensics. Soft-ionization to obtain protonated molecules of low molecular weight compounds

Energy Technology Data Exchange (ETDEWEB)

Yonezawa, Tetsu, E-mail: tetsu@eng.hokudai.ac.jp [Division of Materials Science and Engineering, Faculty of Engineering, Hokkaido University, Kita 13, Nishi 8, Kita-ku, Sapporo, Hokkaido 060-8628 (Japan); Department of Chemistry, School of Science, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan); Asano, Takashi [Division of Materials Science and Engineering, Faculty of Engineering, Hokkaido University, Kita 13, Nishi 8, Kita-ku, Sapporo, Hokkaido 060-8628 (Japan); Criminal Investigation Laboratory, Metropolitan Police Department, 2-1-1 Kasumigaseki, Chiyoda-ku, Tokyo 100-8929 (Japan); Fujino, Tatsuya [Department of Chemistry, Graduate School of Science and Engineering, Tokyo Metropolitan University, 1-1 Minami-Osawa, Hachioji, Tokyo 192-0397 (Japan); Nishihara, Hiroshi [Department of Chemistry, School of Science, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan)

2013-06-20

Highlights: ► MALDI-MS applications for drug identification in forensic science is investigated. ► Cyclodextrin-supported organic matrices strongly suppress the obstacle peaks of organic matrix compounds. ► Cyclodextrin-supported organic matrices also suppress the alkali adducted molecule peaks. ► Sugar units of cyclodextrins work for this specific features. - Abstract: A mass measurement technique for detecting low-molecular-weight drugs with a cyclodextrin-supported organic matrix was investigated. By using cyclodextrin-supported 2,4,6-trihydroxyacetophenone (THAP), the matrix-related peaks of drugs were suppressed. The peaks of protonated molecules of the sample and THAP were mainly observed, and small fragments were detected in a few cases. Despite the Na{sup +} and K{sup +} peaks were observed in the spectrum, Na{sup +} or K{sup +} adduct sample molecules were undetected, owing to the sugar units of cyclodextrin. The advantages of MALDI-MS with cyclodextrin-supported matrices as an analytical tool for forensic samples are discussed. The suppression of alkali adducted molecules and desorption process are also discussed.

Effect of nontronite smectite clay on the chemical evolution of several organic molecules under simulated Mars surface UV radiation conditions

Science.gov (United States)

Poch, Olivier; Dequaire, Tristan; Stalport, Fabien; Jaber, Maguy; Lambert, Jean-François; Szopa, Cyril; Coll, Patrice

2015-04-01

The search for organic carbon-containing molecules at the surface of Mars, as clues of past habitability or remnants of life, is a major scientific goal for Mars exploration. Several lines of evidence, including the detection of phyllosilicates, suggest that early Mars offered favorable conditions for long-term sustaining of water. As a consequence, we can assume that in those days, endogenous chemical processes, or even primitive life, may have produced organic matter on Mars. Moreover, exogenous delivery from small bodies or dust particles is likely to have brought fresh organic molecules to the surface of Mars up today. Organic matter is therefore expected to be present at the surface/subsurface of the planet. But the current environmental conditions at the surface - UV radiation, oxidants and energetic particles - generate physico-chemical processes that may affect organic molecules. On the other hand, on Earth, phyllosilicates are known to accumulate and preserve organic matter. But are phyllosilicates efficient at preserving organic molecules under the current environmental conditions at the surface of Mars? We have monitored the qualitative and quantitative evolutions of glycine, urea and adenine interacting with the Fe3+-smectite clay nontronite, one of the most abundant phyllosilicates present at the surface of Mars, under simulated Martian surface ultraviolet light (190-400 nm), mean temperature (218 ± 2 K) and pressure (6 ± 1 mbar) in a laboratory simulation setup. We have tested organic-rich samples which may be representative of the evaporation of a warm little pond of liquid water having concentrated organics on Mars. For each molecule, we have observed how the nontronite influences the quantum efficiency of its photodecomposition and the nature of its solid evolution products. The results reveal a pronounced photoprotective effect of nontronite on the evolution of glycine and adenine: their efficiencies of photodecomposition are reduced by a factor

Spinterface between tris(8-hydroxyquinoline)metal(III) molecules and magnetic surfaces: a first-principles study

Science.gov (United States)

Jiang, W.; Wang, Jingying; Dougherty, Daniel; Liu, Feng; Feng Liu Team; Daniel Dougherty Team

Using first-principles calculations, we have systematically investigated the hybridization between tris(8-hydroxyquinoline)metal(III) (Mq3, M = Fe, Cr, Al) molecules and magnetic substrates (Co and Cr). Mq3 with different central metal elements but the same organic framework has dramatically different interaction with different magnetic substrates, which affect the interface state significantly. AFM coupling was observed between magnetic Mq3 molecules and ferromagnetic (Co) as well as antiferromagnetic (Cr) substrate, manifested with a superexchange and direct exchange interaction, respectively. Such strong magnetic interfacial coupling may open a gap around the Fermi level and significantly change interface transport properties. Nonmagnetic Alq3 molecule was found to enhance the interface spin polarization due to hybridization between the lowest unoccupied molecular orbitals (LUMO) of Alq3 and metallic surface state. These findings will help better understand spinterface and shed new light on future application of Mq3 molecules in spintronics devices. This work was support by NSF-MRSEC (DMR-1121252) and DOE-BES (DE-FG02-04ER46148).

Femtosecond spectroscopic study of the solvation of amphiphilic molecules by water

NARCIS (Netherlands)

Rezus, Y.L.A.; Bakker, H.J.

2008-01-01

We use polarization-resolved mid-infrared pump-probe spectroscopy to study the aqueous solvation of proline and N-methylacetamide. These molecules serve as models to study the solvation of proteins. We monitor the orientational dynamics of partly deuterated water molecules (HDO) that are present at

Polarization Energies at Organic–Organic Interfaces: Impact on the Charge Separation Barrier at Donor–Acceptor Interfaces in Organic Solar Cells

KAUST Repository

Ryno, Sean

2016-05-31

We probe the energetic landscape at a model pentacene/fullerene-C60 interface to investigate the interactions between positive and negative charges, which are critical to the processes of charge separation and recombination in organic solar cells. Using a polarizable force field, we find that polarization energy, i.e. the stabilization a charge feels due to its environment, is larger at the interface than in the bulk for both a positive and a negative charge. The combination of the charge being more stabilized at the interface and the Coulomb attraction between the charges, results in a barrier to charge separation at the pentacene-C60 interface that can be in excess of 0.7 eV for static configurations of the donor and acceptor locations. However, the impact of molecular motions, i.e., the dynamics, at the interface at room temperature results in a distribution of polarization energies and in charge separation barriers that can be significantly reduced. The dynamic nature of the interface is thus critical, with the polarization energy distributions indicating that sites along the interface shift in time between favorable and unfavorable configurations for charge separation.

Calculation of rate coefficients of some proton-transfer ion-molecule reactions in weakly ionized gases

International Nuclear Information System (INIS)

Stiller, W.

1985-01-01

A classical collision theory is used to describe thermal bimolecular rate coefficeints for reaction between positive and negative ions and polar molecules in a carrier gas. Special attention is paid to ion-molecule reaction in which proton transfer occurs. These reactions play an important role in terrestrial plasma devices, in ionosphere, in planetary atmospheres and in interstellar matter. The equilibrium rate coefficients of the reactions are calculated based on a microscopic reactive cross section derived from a long distance polar molecule-ion potential. The results are compared with experimental values of afterglow measurements. (D.Gy.)

Surface-enhanced resonance Raman scattering spectroscopy of single R6G molecules

Institute of Scientific and Technical Information of China (English)

Zhou Zeng-Hui; Liu Li; Wang Gui-Ying; Xu Zhi-Zhan

2006-01-01

Surface-enhanced resonance Raman scattering (SERRS) of Rhodamine 6G (R6G) adsorbed on colloidal silver clusters has been studied. Based on the great enhancement of the Raman signal and the quench of the fluorescence, the SERRS spectra of R6G were recorded for the samples of dye colloidal solution with different concentrations. Spectral inhomogeneity behaviours from single molecules in the dried sample films were observed with complementary evidences, such as spectral polarization, spectral diffusion, intensity fluctuation of vibrational lines and even "breathing" of the molecules. Sequential spectra observed from a liquid sample with an average of 0.3 dye molecules in the probed volume exhibited the expected Poisson distribution for actually measuring 0, 1 or 2 molecules. Difference between the SERRS spectra of R6G excited by linearly and circularly polarized light were experimentally measured.

Manipulating ultracold polar molecules with microwave radiation: The influence of hyperfine structure

International Nuclear Information System (INIS)

Aldegunde, J.; Hutson, Jeremy M.; Ran Hong

2009-01-01

We calculate the microwave spectra of ultracold 40 K 87 Rb alkali-metal dimers, including hyperfine interactions and in the presence of electric and magnetic fields. We show that microwave transitions may be used to transfer molecules between different hyperfine states, but only because of the presence of nuclear quadrupole interactions. Hyperfine splittings may also complicate the use of ultracold molecules for quantum computing. The spectrum of molecules oriented in electric fields may be simplified dramatically by applying a simultaneous magnetic field.

Marine polar steroids

International Nuclear Information System (INIS)

Stonik, Valentin A

2001-01-01

Structures, taxonomic distribution and biological activities of polar steroids isolated from various marine organisms over the last 8-10 years are considered. The peculiarities of steroid biogenesis in the marine biota and their possible biological functions are discussed. Syntheses of some highly active marine polar steroids are described. The bibliography includes 254 references.

Effect of organic small-molecule hole injection materials on the performance of inverted organic solar cells

Science.gov (United States)

Li, Jie; Zheng, Yifan; Zheng, Ding; Yu, Junsheng

2016-07-01

In this study, the influence of small-molecule organic hole injection materials on the performance of organic solar cells (OSCs) as the hole transport layer (HTL) with an architecture of ITO/ZnO/P3HT:PC71BM/HTL/Ag has been investigated. A significant enhancement on the performance of OSCs from 1.06% to 2.63% is obtained by using N, N‧-bis(1-naphthalenyl)-N, N‧-bis-phenyl-(1, 1‧-biphenyl)-4, 4‧-diamine (NPB) HTL. Through the resistance simulation and space-charge limited current analysis, we found that NPB HTL cannot merely improve the hole mobility of the device but also form the Ohmic contact between the active layer and anode. Besides, when we apply mix HTL by depositing the NPB on the surface of molybdenum oxide, the power conversion efficiency of OSC are able to be further improved to 2.96%.

Solution-processed white organic light-emitting devices based on small-molecule materials

International Nuclear Information System (INIS)

Wang Dongdong; Wu Zhaoxin; Zhang Xinwen; Wang Dawei; Hou Xun

2010-01-01

We investigated solution-processed films of 4,4'-bis(2,2-diphenylvinyl)-1,1'-bibenyl (DPVBi) and its blends with N,N'-bis(3-methylphenyl)-(1,1'-biphenyl)-4,4'-diamine (TPD) by atomic force microscopy (AFM). The AFM result shows that the solution-processed films are pin-free and their morphology is smooth enough to be used in OLEDs. We have developed a solution-processed white organic light-emitting device (WOLEDs) based on small-molecules, in which the light-emitting layer (EML) was formed by spin-coating the solution of small-molecules on top of the solution-processed hole-transporting layer. This WOLEDs, in which the EML consists of co-host (DPVBi and TPD), the blue dopant (4,4'-bis[2-(4-(N,N-diphenylamino)phenyl)vinyl]biphenyl) and the yellow dye (5,6,11,12-tetraphenylnaphtacene), has a current efficiency of 6.0 cd/A at a practical luminance of 1000 cd/m 2 , a maximum luminance of 22500 cd/m 2 , and its color coordinates are quite stable. Our research shows a possible approach to achieve efficient and low-cost small-molecule-based WOLEDs, which avoids the complexities of the co-evaporation process of multiple dopants and host materials in vacuum depositions.

Small organic molecules modulating iodine uptake in thyroid

International Nuclear Information System (INIS)

Ambroise, Y.

2006-01-01

The thyroid gland accumulates large quantities of iodine. This uptake is needed for the production of iodinated hormones (T3 and T4). The first step in the iodine accumulation is a basolateral transport of iodide ions by the cloned 'Natrium Iodide Sym-porter' also called NIS. Using high-throughput screening techniques, we have identified a series of inhibitors of the iodide uptake in thyrocytes. These compounds are of medical significance in case of thyroid deregulation and can also offer solutions for radio-iodine detoxification in case of emergency situations (nuclear industry...). In addition, these small organic molecules can be important tools for the understanding of NIS structure and functions In parallel, we have identified and characterized a single compound capable to strongly enhance the amount of intra-cellular iodide in rat thyrocytes (FRTL5) as well as in HEK293 cells transfected with hNIS (Natrium/Iodide Sym-porter). Preliminary studies show that this effect is NIS dependant, and is induced by alternative and unknown mechanisms. Future work will consist in unraveling the mode of action of this molecule. These informations will help us not only to better understand the iodide pathways in the thyroid, but also to design more active analogues. We will use photo-labelling techniques to identify new proteins involved in the iodide transfer and retention. In addition, preliminary experiments are underway to validate our compound as an anti-cancer agent. Targeted NIS gene delivery into tumors plus radio-iodide injection leads to tumor size regression. Unfortunately, doses of radioactivity are to high for safe treatment. Our compound may lead to enhanced radio-iodide entrapment, thus necessitating lower doses of radioactivity for tumor regression. (author)

Production, Manipulation, and Applications of Ultracold Polar Molecules

Science.gov (United States)

2015-04-30

were added to the MURI, and in some cases , the experiments were carried out on different molecules than originally stated (e.g., laser cooling and...interactions between like homonuclear alkali metal diatoms. J. Chem. Phys., 135:244307, 2011. [21] Jason N. Byrd, H. Harvey Michels, Jr. John A. Montgomery...111:1, 2013. [35] M. I. Fabrikant, Tian Li, N. J. Fitch, N. Farrow, Jonathan D. Weinstein , and H. J. Lewandowski. Method for traveling-wave

Anisotropic charge transport in large single crystals of π-conjugated organic molecules.

Science.gov (United States)

Hourani, Wael; Rahimi, Khosrow; Botiz, Ioan; Koch, Felix Peter Vinzenz; Reiter, Günter; Lienerth, Peter; Heiser, Thomas; Bubendorff, Jean-Luc; Simon, Laurent

2014-05-07

The electronic properties of organic semiconductors depend strongly on the nature of the molecules, their conjugation and conformation, their mutual distance and the orientation between adjacent molecules. Variations of intramolecular distances and conformation disturb the conjugation and perturb the delocalization of charges. As a result, the mobility considerably decreases compared to that of a covalently well-organized crystal. Here, we present electrical characterization of large single crystals made of the regioregular octamer of 3-hexyl-thiophene (3HT)8 using a conductive-atomic force microscope (C-AFM) in air. We find a large anisotropy in the conduction with charge mobility values depending on the crystallographic orientation of the single crystal. The smaller conduction is in the direction of π-π stacking (along the long axis of the single crystal) with a mobility value in the order of 10(-3) cm(2) V(-1) s(-1), and the larger one is along the molecular axis (in the direction normal to the single crystal surface) with a mobility value in the order of 0.5 cm(2) V(-1) s(-1). The measured current-voltage (I-V) curves showed that along the molecular axis, the current followed an exponential dependence corresponding to an injection mode. In the π-π stacking direction, the current exhibits a space charge limited current (SCLC) behavior, which allows us to estimate the charge carrier mobility.

Polarization Raman spectroscopy to explain rodent models of brittle bone

Science.gov (United States)

Makowski, Alexander J.; Nyman, Jeffry S.; Mahadevan-Jansen, Anita

2013-03-01

Activation Transcription Factor 4 (Atf-4) is essential for osteoblast maturation and proper collagen synthesis. We recently found that these bones demonstrate a rare brittleness phenotype, which is independent of bone strength. We utilized a confocal Renishaw Raman microscope (50x objective; NA=.75) to evaluate embedded, polished cross-sections of mouse tibia from both wild-type and knockout mice at 8 weeks of age (24 mice, nmineral and collagen; however, compositional changes did not fully encompass biomechanical differences. To investigate the impact of material organization, we acquired colocalized spectra aligning the polarization angle parallel and perpendicular to the long bone axis from wet intact femurs. To validate our results, we used MMP9-/- mice, which have a brittleness phenotype that is not explained by compositional Raman measures. Polarization angle difference spectra show marked significant changes in orientation of these compositional differences when comparing wild type to knockout bones. Relative to wild-type, Atf4 -/- and MMP9 -/- bones show significant differences (t-test; pbones. Such findings could have alternate interpretations about net collagen orientation or the angular distribution of collagen molecules. Use of polarization specific Raman measurements has implicated a structural profile that furthers our understanding of models of bone brittleness. Polarization content of Raman spectra may prove significant in future studies of brittle fracture and human fracture risk.

Exploring the magnetic and organic microstructures with photoemission electron microscope

Energy Technology Data Exchange (ETDEWEB)

Wei, D.H., E-mail: dhw@nsrrc.org.tw [National Synchrotron Radiation Research Center, Hsinchu Science Park, 30076 Hsinchu, Taiwan (China); Chan, Yuet-Loy; Hsu, Yao-Jane [National Synchrotron Radiation Research Center, Hsinchu Science Park, 30076 Hsinchu, Taiwan (China)

2012-10-15

Highlights: Black-Right-Pointing-Pointer PEEM with polarized photon enables additional image contrasts and physical insights. Black-Right-Pointing-Pointer XMCD-based images reveal the shape-dependent domains in Ni80Fe20 microstructures. Black-Right-Pointing-Pointer XLD-based images confirm the success of molecular orientation controls. Black-Right-Pointing-Pointer The two interfaces in Co-Pn-Co structures are magnetically and chemically different. -- Abstract: We present photoemission electron microscopy (PEEM) studies on geometrically constrained ferromagnetic, organic, and organics-ferromagnet hybrid structures. Powered by an elliptically polarized undulator, the PEEM at Taiwan Light Source (TLS) is capable of recording polarization enhanced X-ray images and has been employed to examine the domain configurations in a lithographically patterned permalloy film as well as the orientations of pentacene molecules adsorbed on self-assembled monolayers (SAMs) modified gold surfaces. In addition, magnetic images acquired on cobalt/pentacene and pentacene/cobalt bilayers reveal that in hybrid structures the order of thin film deposition can lead to distinct domain configurations. Spectroscopic evidence further suggests that there is significant orbital hybridization at the interface where metallic cobalt was deposited directly on organic pentacene.

Single molecule conductance

NARCIS (Netherlands)

Willems, R.

2008-01-01

This thesis represents an excursion into the world of molecular electronics, i.e. the field of research trying to use individual (organic) molecules as electronic components; in this work various experimental methods have been explored to connect individual molecules to metallic contacts and

Concentration polarization in nanochannel DNA electrophoresis

NARCIS (Netherlands)

Dubsky, P.; Das, Siddhartha; van den Berg, Albert; Eijkel, Jan C.T.

2011-01-01

We demonstrate that the large field electrophoresis of a single DNA molecule in nanofluidic systems is accompanied by concentration polarization. We illustrate this phenomena by utilizing our electrophoretic simulation tool SIMUL. First we in-vestigate a simple system with univalent strong

Polarization Dependent Dynamics of CO2 Trapped in AN Optical Centrifuge

Science.gov (United States)

Toro, Carlos; Echebiri, Geraldine; Liu, Qingnan; Mullin, Amy S.

2012-06-01

An optical centrifuge (Yuan {et al}. {PNAS} 2011, 108, 6872) has been employed to prepare carbon dioxide molecules in very high rotational states (``hot'' rotors, J ˜220) in order to investigate how collisions relax ensembles of molecules with an overall angular momentum that is spatially oriented. We have performed polarization-dependent high resolution transient IR absorption measurements to study the spatial dependence of the relaxation dynamics. Our results show that the net angular momentum of the initially centrifuged molecules persists for at least 10 gas kinetic collisions and that the translational energy distributions are dependent on the probe orientation and polarization. These studies indicate that the centrifuged molecules tend to maintain the orientation of their initial angular momentum for the first set of collisions and that relatively large changes in J are involved in the first collisions.

FORMATION AND RECONDENSATION OF COMPLEX ORGANIC MOLECULES DURING PROTOSTELLAR LUMINOSITY OUTBURSTS

International Nuclear Information System (INIS)

Taquet, Vianney; Wirström, Eva S.; Charnley, Steven B.

2016-01-01

During the formation of stars, the accretion of surrounding material toward the central object is thought to undergo strong luminosity outbursts followed by long periods of relative quiescence, even at the early stages of star formation when the protostar is still embedded in a large envelope. We investigated the gas-phase formation and recondensation of the complex organic molecules (COMs) di-methyl ether and methyl formate, induced by sudden ice evaporation processes occurring during luminosity outbursts of different amplitudes in protostellar envelopes. For this purpose, we updated a gas-phase chemical network forming COMs in which ammonia plays a key role. The model calculations presented here demonstrate that ion–molecule reactions alone could account for the observed presence of di-methyl ether and methyl formate in a large fraction of protostellar cores without recourse to grain-surface chemistry, although they depend on uncertain ice abundances and gas-phase reaction branching ratios. In spite of the short outburst timescales of about 100 years, abundance ratios of the considered species higher than 10% with respect to methanol are predicted during outbursts due to their low binding energies relative to water and methanol which delay their recondensation during cooling. Although the current luminosity of most embedded protostars would be too low to produce complex organics in the hot-core regions that are observable with current sub-millimetric interferometers, previous luminosity outburst events would induce the formation of COMs in extended regions of protostellar envelopes with sizes increasing by up to one order of magnitude

Formation and Recondensation of Complex Organic Molecules during Protostellar Luminosity Outbursts

Science.gov (United States)

Taquet, Vianney; Wirström, Eva S.; Charnley, Steven B.

2016-04-01

During the formation of stars, the accretion of surrounding material toward the central object is thought to undergo strong luminosity outbursts followed by long periods of relative quiescence, even at the early stages of star formation when the protostar is still embedded in a large envelope. We investigated the gas-phase formation and recondensation of the complex organic molecules (COMs) di-methyl ether and methyl formate, induced by sudden ice evaporation processes occurring during luminosity outbursts of different amplitudes in protostellar envelopes. For this purpose, we updated a gas-phase chemical network forming COMs in which ammonia plays a key role. The model calculations presented here demonstrate that ion-molecule reactions alone could account for the observed presence of di-methyl ether and methyl formate in a large fraction of protostellar cores without recourse to grain-surface chemistry, although they depend on uncertain ice abundances and gas-phase reaction branching ratios. In spite of the short outburst timescales of about 100 years, abundance ratios of the considered species higher than 10% with respect to methanol are predicted during outbursts due to their low binding energies relative to water and methanol which delay their recondensation during cooling. Although the current luminosity of most embedded protostars would be too low to produce complex organics in the hot-core regions that are observable with current sub-millimetric interferometers, previous luminosity outburst events would induce the formation of COMs in extended regions of protostellar envelopes with sizes increasing by up to one order of magnitude.

FORMATION AND RECONDENSATION OF COMPLEX ORGANIC MOLECULES DURING PROTOSTELLAR LUMINOSITY OUTBURSTS

Energy Technology Data Exchange (ETDEWEB)

Taquet, Vianney [Leiden Observatory, Leiden University, P.O. Box 9513, 2300-RA Leiden (Netherlands); Wirström, Eva S. [Department of Earth and Space Sciences, Chalmers University of Technology, Onsala Space Observatory, SE-439 92 Onsala (Sweden); Charnley, Steven B. [Astrochemistry Laboratory and The Goddard Center for Astrobiology, Mailstop 691, NASA Goddard Space Flight Center, 8800 Greenbelt Road, Greenbelt, MD 20770 (United States)

2016-04-10

During the formation of stars, the accretion of surrounding material toward the central object is thought to undergo strong luminosity outbursts followed by long periods of relative quiescence, even at the early stages of star formation when the protostar is still embedded in a large envelope. We investigated the gas-phase formation and recondensation of the complex organic molecules (COMs) di-methyl ether and methyl formate, induced by sudden ice evaporation processes occurring during luminosity outbursts of different amplitudes in protostellar envelopes. For this purpose, we updated a gas-phase chemical network forming COMs in which ammonia plays a key role. The model calculations presented here demonstrate that ion–molecule reactions alone could account for the observed presence of di-methyl ether and methyl formate in a large fraction of protostellar cores without recourse to grain-surface chemistry, although they depend on uncertain ice abundances and gas-phase reaction branching ratios. In spite of the short outburst timescales of about 100 years, abundance ratios of the considered species higher than 10% with respect to methanol are predicted during outbursts due to their low binding energies relative to water and methanol which delay their recondensation during cooling. Although the current luminosity of most embedded protostars would be too low to produce complex organics in the hot-core regions that are observable with current sub-millimetric interferometers, previous luminosity outburst events would induce the formation of COMs in extended regions of protostellar envelopes with sizes increasing by up to one order of magnitude.

Structural Ordering of Semiconducting Polymers and Small-Molecules for Organic Electronics

Science.gov (United States)

O'Hara, Kathryn Allison

Semiconducting polymers and small-molecules can be readily incorporated into electronic devices such as organic photovoltaics (OPVs), thermoelectrics (OTEs), organic light emitting diodes (OLEDs), and organic thin film transistors (OTFTs). Organic materials offer the advantage of being processable from solution to form flexible and lightweight thin films. The molecular design, processing, and resulting thin film morphology of semiconducting polymers drastically affect the optical and electronic properties. Charge transport within films of semiconducting polymers relies on the nanoscale organization to ensure electronic coupling through overlap of molecular orbitals and to provide continuous transport pathways. While the angstrom-scale packing details can be studied using X-ray scattering methods, an understanding of the mesoscale, or the length scale over which smaller ordered regions connect, is much harder to achieve. Grain boundaries play an important role in semiconducting polymer thin films where the average grain size is much smaller than the total distance which charges must traverse in order to reach the electrodes in a device. The majority of semiconducting polymers adopt a lamellar packing structure in which the conjugated backbones align in parallel pi-stacks separated by the alkyl side-chains. Only two directions of transport are possible--along the conjugated backbone and in the pi-stacking direction. Currently, the discussion of transport between crystallites is centered around the idea of tie-chains, or "bridging" polymer chains connecting two ordered regions. However, as molecular structures become increasingly complex with the development of new donor-acceptor copolymers, additional forms of connectivity between ordered domains should be considered. High resolution transmission electron microscopy (HRTEM) is a powerful tool for directly imaging the crystalline grain boundaries in polymer and small-molecule thin films. Recently, structures