Search results for "bonding"
showing 10 items of 996 documents
Short hydrogen bonds enhance nonaromatic protein-related fluorescence
2021
Significance Intrinsic fluorescence of nonaromatic amino acids is a puzzling phenomenon with an enormous potential in biophotonic applications. The physical origins of this effect, however, remain elusive. Herein, we demonstrate how specific hydrogen bond networks can modulate fluorescence. We highlight the key role played by short hydrogen bonds, present in the protein structure, on the ensuing fluorescence. We provide detailed experimental and molecular evidence to explain these unusual nonaromatic optical properties. Our findings should benefit the design of novel optically active biomaterials for applications in biosensing and imaging.
Adhesion trends and growth mode of ultra-thin copper films on MgO
2004
Ab initio simulations are performed for Cu atoms adsorbed on the perfect MgO(001) substrate, with an ordered metal coverage varied from 1 monolayer (ML), i.e. almost single atoms, up t o1M L. As trong dependence of the adhesion energy and the sub-monolayer film distance from the substrate on the surface coverage and adsorbate positions (Mg 2+ or O 2− )i s discussed. The nature of interfacial bonding at all coverages is physisorption .W hen increasing Cu atomic fraction, a decrease of the substrate-induced polarization of adatoms accompanied by an increase of both in-plane metallic bonding and the interfacial distance has been found. Combining results of ab initio calculations with thermodyn…
Studies of structures and properties of polymeric systems containing bis-(hydroxy-arylidene)alkanones as NLO-active chromophores
2002
Abstract NLO-properties of polymer systems containing bis-(hydroxy-arylidene)alkanone chromophores were studied experimentally and analyzed using ab initio quantum chemical calculations. A monoclinic crystal structure (space group P2111) of the polyester containing fragments of such chromophores in the backbone was simulated and a reasonable agreement between the experimental and simulated X-ray powder diffraction patterns was achieved. Ab initio quantum-mechanical estimations of the SHG-observable macroscopic second-order non-linearity tensor coefficients, obtained for the polymer crystal structure at the HF SCF level, led to the major dXZZ-coefficient of 1.9 pm/V. Films of ionic complexes…
Anomalous Kinetics of Diffusion-Controlled Defect Annealing in Irradiated Ionic Solids
2017
The authors thanks A. Ch. Lushchik, M. Izerrouken, and V. Lisitsyn for stimulating discussions. This work has been carried out within the framework of the EUROfusion Consortium and has received funding from the Euroatom research and training programme 2014-2018 under Grant Agreement No. 633053. The views and opinions expressed herein do not necessarily reflect those of the European Commission. R.V. acknowledges the financial support by the MEIC (Ministerio de Economa, Industria y Competitivad; Project ENE2015-70300-C3-1-R). The calculations were performed using facilities of the Stuttgart Supercomputer Center (Project DEFTD 12939).
ChemInform Abstract: Weak Interactions Between Trivalent Pnictogen Centers: Computational Analysis of Bonding in Dimers X3E···EX3(E: Pnictogen, X: Ha…
2009
The nature of weak interactions in dimers X3E···EX3 (E = N−Bi, X = F−I) was investigated by wave function and density functional theory (DFT)-based methods. Out of the 20 systems studied, 10 are found to be bound at the CP-MP2 and LMP2 levels of theory. Detailed partition of the interaction energy into different components revealed that dispersion is the primary force holding the dimers together but there also exists an important ionic component whose contribution increases with increasing halogen size. As expected, standard density functionals fail to describe bonding in the studied systems. However, the performance of DFT methods can be easily improved via empirical dispersion correction …
Operational Mechanism of Conjugated Polyelectrolytes
2014
Conjugated polyelectrolytes (CPEs) are versatile materials used in a range of organic optoelectronic applications. Because of their ionic/electronic nature, characterizing these materials is nontrivial, and their operational mechanism is not fully understood. In this work we use a methodology that combines constant-voltage-driven current-density transient measurements with fast current vs voltage scans to allow decoupling of ionic and electronic phenomena. This technique is applied to diodes prepared with cationic CPEs having different charge-compensating anions. Our results indicate that the operational mechanism of these devices is governed by electrochemical doping of the CPE. On the bas…
Synergistic effect of ligating and ionic functions, prearranged on a calix[4]arene.
2006
The covalent attachment of two CMPO-functions and two anionic Cosan groups to the narrow rim of tert-butylcalix[4]arene leads to a dramatic increase of the extraction efficiency for the cone isomer; Am(3+) is removed from 5 x 10(-8) M solution to more than 99% by a single extraction step with a 3 x 10(-6) M solution of the calixarene.
Electrochemical capacitance spectroscopy and capacitive relaxation of the changeover process in iron hexacyanoferrate molecular compound
2010
Abstract In this work it was proposed the use electrochemical capacitance spectroscopy (ECS) to evaluate the storage process during changeover in FeHCF compound. The approach is equivalent to electrochemical impedance spectroscopy (EIS) albeit from such analysis it was possible to focus attention on the capacitive and dielectric relaxation instead of the dispersive relaxation related to charge transfer. From such approach it was possible to obtain complementary information on the role played by [Fe 2+ (CN) 6 ] 4− vacancies during the changeover process. It was observed that Fe 3+ (NC) 5 OH − clusters located in these vacancies mediate an electronic and ionic coupled trapping/detrapping proc…
Effect of cationic polyamidoamine dendrimers on ionic transport through nanochannels
2021
Abstract The effect of polyamidoamine (PAMAM) dendrimers (generations G0–G3) on the ion transport properties of nanochannels (conical and cylindrical) is studied either by surface functionalization or by addition to the electrolyte solution. Surface functionalization with cationic dendrimers lead to inversion of the ion current rectification, indicating the anion selectivity of the modified nanochannels. This anion selectivity increases by immobilizing higher-generation dendrimers, as expected for an increase in the surface density of amino groups. However, compared to PAMAM G2, functionalization with PAMAM G3 results in higher cation and lower anion fluxes. Diffusion experiments of charged…
Recent advances in light-emitting electrochemical cells
2011
Light-emitting electrochemical cells (LECs) are solution-processable thin-film electroluminescent devices consisting of a luminescent material in an ionic environment. The simplest type of LEC is based on only one material, ionic transition-metal complexes (iTMCs). These materials are of interest for different scientific fields such as chemistry, physics, and technology as selected chemical modifications of iTMCs resulted in crucial breakthroughs for the performance of LECs. This short review highlights the different strategies used to design these compounds with the aim to enhance the performances of LECs.