Search results for "Acceptor"
showing 10 items of 394 documents
Synthesis and molecular properties of donor–π-spacer–acceptor ynamides with up to four conjugated alkyne units
2010
A set of push-pull ynamides with up to four conjugated triple bonds has been synthesized and the molecular properties of these new carbon rods have been characterised showing effective intramolecular charge transfers and high values for the change of the electrical dipole moment after transition from the ground to the Franck-Condon excited state.
Unusual conformations of 1,3-dialkoxythiacalix[4]arenes in the solid state
2006
The structures of three syn-1,3-dialkoxythiacalix[4]arenes with unusual conformations in the solid state are reported. The pinched cone conformation of syn-2 2 ,4 2 -dihydroxy-1 2 ,3 2 -bis-(prop-2-enyloxy)thiacalix[4]arene, C 30 H 24 O 4 S 4 , (3a), is stabilized by two intramolecular hydrogen bonds, remarkably formed from both OH groups to the same ether O atom. In syn-22,42-dihydroxy-1 5 ,2 5 ,3 5 ,4 5 -tetranitro-12,32-bis(prop-2-enyloxy)thiacalix[4]arene acetone disolvate, C 30 H 20 N 4 O 12 S 4 ·-2C 3 H 6 O, (3b1), the molecule is found in the 1,3-alternate conformation. The crystallographic C2 symmetry is due to a twofold rotation axis running through the centre of the calixarene rin…
Evolution of arginine deiminase (ADI) pathway genes
2002
We have analyzed the evolution of the three genes encoding structural enzymes of the arginine deiminase (ADI) pathway, arginine deiminase (ADI), ornithine transcarbamoylase (OTC), and carbamate kinase (CK) in a wide range of organisms, including Archaea, Bacteria, and Eukarya. This catabolic route was probably present in the last common ancestor to all the domains of life. The results obtained indicate that these genes have undergone a complex evolutionary history, including horizontal transfer events, duplications, and losses. Therefore, these genes are not adequate to infer organismal relationships at deep branching levels, but they provide an insight into how catabolic genes evolved and …
Defect reactions of implanted Li in ZnSe observed by β-NMR
2001
Abstract Using β-radiation detected nuclear magnetic resonance (β-NMR), we investigated the microscopic behavior of implanted 8 Li in nominally undoped ZnSe crystals. From the temperature-dependent amplitudes of high-resolution NMR spectra we conclude a gradual interstitial-to-substitutional site change between 200 and 350 K . This is in accordance with earlier emission channeling results. We argue that this conversion proceeds via Lii++VZn2−→LiZn− and involves implantation related Zn vacancies.
Plasmon-Induced Direct Hot-Carrier Transfer at Metal-Acceptor Interfaces.
2019
Plasmon-induced hot-carrier transfer from a metal nanostructure to an acceptor is known to occur via two key mechanisms: (i) indirect transfer, where the hot carriers are produced in the metal nanostructure and subsequently transferred to the acceptor, and (ii) direct transfer, where the plasmons decay by directly exciting carriers from the metal to the acceptor. Unfortunately, an atomic-level understanding of the direct-transfer process, especially with regard to its quantification, remains elusive even though it is estimated to be more efficient compared to the indirect-transfer process. This is due to experimental challenges in separating direct from indirect transfer as both processes o…
A Novel Gas Sensor Transducer Based on Phthalocyanine Heterojunction Devices
2007
Abstract: Experimental data concerning the changes in the current-voltage (I-V) perfor-mances of a molecular material-based heterojunction consisting of hexadecafluorinated nickel phthalocyanine (Ni(F 16 Pc)) and nickel phthalocyanine (NiPc), (Au|Ni(F 16 Pc)|NiPc|Al) are introduced as an unprecedented principle of transduction for gas sensing performances. The respective n - and p -type doped-insulator behaviors of the respective materials are supported, owing to the observed changes in surface potential (using the Kelvin probe method) after submission to electron donor (ammonia) and electron acceptor gases (ozone). On the other hand, the bilayer device exhibits strong variations in the bui…
Nitrogen and sulfur co-doped carbon nanodots toward bovine hemoglobin: A fluorescence quenching mechanism investigation
2018
A deep understanding of the molecular interactions of carbon nanodots with biomacromolecules is essential for wider applications of carbon nanodots both in vitro and in vivo. Herein, nitrogen and sulfur co-doped carbon dots (N,S-CDs) with a quantum yield of 16% were synthesized by a 1-step hydrothermal method. The N,S-CDs exhibited a good dispersion, with a graphite-like structure, along with the fluorescence lifetime of approximately 7.50 ns. Findings showed that the fluorescence of the N,S-CDs was effectively quenched by bovine hemoglobin as a result of the static fluorescence quenching. The mentioned quenching mechanism was investigated by the Stern-Volmer equation, temperature-dependent…
Tetrathiafulvalene-Polychlorotriphenylmethyl Dyads: Influence of Bridge and Open-Shell Characteristics on Linear and Nonlinear Optical Properties
2017
Three conjugated donor-π-acceptor radical systems (1 a–1 c) were prepared by bridging a tetrathiafulvalene (TTF) electron-donor unit to a polychlorotriphenylmethyl (PTM) electron-acceptor radical through vinylene units of different lengths. The dependence of the intramolecular charge transfer on the length of the conjugated bridge has been analyzed by different electrochemical and spectroscopic techniques. Linear optical properties and the second-order nonlinear optical (NLO) response of these derivatives have been computed by comparing systems 1 a–1 c with the non-radical analogues (2 a–2 c). Interestingly, an enhanced NLO response is predicted for dyads 1 a–1 c with PTM in the radical for…
Gamma-X-ray coincidence Mössbauer emission spectroscopy on57Co/CoO
1994
The time integral Mossbauer emission spectrum of a57Co/Co1−xO source (x ≈ 10−5) at RT consists of two single Lorentzian lines of an Fe2+ (76%) charge state and an Fe3+ (24%) aliovalent charge state. The spectrum measured by γ-X-ray coincidence spectrpscopy shows the same fraction of the aliovalent charge state, contrary to the expectation derived from the competing acceptor model as successfully applied by Tejada and Parak [1], who could explain the dependence of the formation of aliovalent charge states after the nuclear transformation on the stoichiometric parameterx. The consequences of this unexpected behaviour for the competing acceptor model are discussed.
Magnetic resonance investigations of oxygen-related luminescence centres in AlN ceramics
2001
Abstract The structure of oxygen-related luminescence centres in nominally undoped and Y2O3-doped AIN ceramics were investigated by electron paramagnetic resonance (EPR), electron nuclear double resonance (ENDOR) and optically-detected EPR. The photoluminescence-detected EPR lines having g values of 1.990 and 2.008 were attributed to neighbouring donor and acceptor pairs causing the recombination luminescence excited in the ultraviolet. The two EPR lines at g = 1.987 and g = 2.003, detected via the recombination luminescence in the afterglow, are thought to be due to a recombination between the same, but more distant donor and acceptor pairs. The donor is supposed to be an electron trapped …