Search results for "iTED"
showing 10 items of 2408 documents
Surface-Specific Spectroscopy of Water at a Potentiostatically Controlled Supported Graphene Monolayer
2019
Knowledge of the structure of interfacial water molecules at electrified solid materials is the first step toward a better understanding of important processes at such surfaces, in, e.g., electrochemistry, atmospheric chemistry, and membrane biophysics. As graphene is an interesting material with multiple potential applications such as in transistors or sensors, we specifically investigate the graphene–water interface. We use sum-frequency generation spectroscopy to investigate the pH- and potential-dependence of the interfacial water structure in contact with a chemical vapor deposited (CVD) grown graphene surface. Our results show that the SFG signal from the interfacial water molecules a…
Excited-state non-radiative decay in stilbenoid compounds: An: Ab initio quantum-chemistry study on size and substituent effects
2019
In the framework of optoelectronic luminescent materials, non-radiative decay mechanisms are relevant to interpret efficiency losses. These radiationless processes are herein studied theoretically for a series of stilbenoid derivatives, including distyrylbenzene (DSB) and cyano-substituted distyrylbenzene (DCS) molecules in vacuo. Given the difficulties of excited-state reaction path determinations, a simplified computational strategy is defined based on the exploration of the potential energy surfaces (PES) along the elongation, twisting, and pyramidalization of the vinyl bonds. For such exploration, density functional theory (DFT), time-dependent (TD)DFT, and complete-active-space self-co…
Laser-Calorimetric Study of Fundamental Absorption Edge in Pb,La(ZrTi)O3 (PLZT) Perovskite Ceramics
2000
The values of the light absorption coefficient of PLZT 10/65/35 ceramics at selected wavelengths have been obtained by laser calorimetric measurements. The absorption coefficient of the PLZT ceramics is an exponential function of the photon energy. Two values of characteristic Urbach energy have been found ΔE1 = 106 meV and ΔE2 = 238 meV. The first one is a characteristic of the potential of electron-phonon interaction of the optically excited transitions from the valence band to the conduction band and does not depend on lattice defects or admixtures. The other characterises the electron-phonon interaction at optical transitions between two localized electron states in the energy gap separ…
BiI3 nanoclusters in melt-grown CdI2 crystals studied by optical absorption spectroscopy
2013
Optical absorption spectroscopy of CdI2–BiI3 layered crystals has been performed in the temperature range of 77–300 K. The main absorption, observed in these crystals at 2.59 eV is related to quantum confined exciton absorption of bimolecular BiI3 cluster. Low energy absorption peaks at 2.38 eV, 2.06 eV and 1.94 eV can be tentatively assigned to larger clusters composed of 4, 6 or more BiI3 molecules. In ultra-thin samples of CdI2–BiI3 several bands at 2.84 eV, 3.03 eV and 3.27 eV were observed which are ascribed to higher excited states of the excitons in bimolecular BiI3 cluster.
Exciton interaction with Ce3+ and Ce4+ ions in (LuGd)3(Ga,Al)5O12 ceramics
2021
The authors acknowledge the expert help of the staff of MAX IV Laboratory. The research leading to this result has been supported by the project CALIPSOplus under the Grant Agreement 730872 from the EU Framework Programme for Research and Innovation HORIZON 2020. I.V. acknowledges the support of Russian Foundation for Basic Research # 20-52-S52001.
Calculation of vibrationally resolved absorption and fluorescence spectra of the rylenes
2020
A generating function method was used to simulate the vibrationally resolved absorption and emission spectra of perylene, terrylene and quaterrylene. This method operates on the basis of adiabatic excitation energies and electronic ground and excited state vibrational frequencies. These parameters were calculated using density functional theory with the PBE0 functional for perylene and terrylene and with the BH-LYP functional for quaterrylene. The vertical excitation energies of the lower excited states were calculated using functionals with differing amounts of Hartree-Fock exchange. The optimal functional for each molecule was chosen by comparing these energies to literature excitation en…
X-ray excited luminescence of SrAl2O4:Eu,Dy at low temperatures
2018
This research project was supported financially by ERDF Project No 1.1.1.1/16/A/182.
Molecular Ruby under Pressure
2018
The intensely luminescent chromium(III) complexes [Cr(ddpd)2 ]3+ and [Cr(H2 tpda)2 ]3+ show surprising pressure-induced red shifts of up to -15 cm-1 kbar-1 for their sharp spin-flip emission bands (ddpd=N,N'-dimethyl-N,N'-dipyridine-2-yl-pyridine-2,6-diamine; H2 tpda=2,6-bis(2-pyridylamino)pyridine). These shifts surpass that of the established standard, ruby Al2 O3 :Cr3+ , by a factor of 20. Beyond the common application in the crystalline state, the very high quantum yield of [Cr(ddpd)2 ]3+ enables optical pressure sensing in aqueous and methanolic solution. These unique features of the molecular rubies [Cr(ddpd)2 ]3+ and [Cr(H2 tpda)2 ]3+ pave the way for highly sensitive optical pressu…
Halloysite Nanotubes: Interfacial Properties and Applications in Cultural Heritage
2020
The peculiar surfaces of halloysite nanotubes and their biocompatibility are attracting the interest of researchers based on the wide range of attainable applications. The large aspect ratio of this nanotubular material ensures promising properties as a reinforcing agent in polymeric matrixes, such as cellulose and its derivatives, that entail strengthening due to, for instance, aging-induced degradation. The halloysite cavity has a suitable size for hosting a large variety of active species such as deacidifying (calcium hydroxide) and flame retardant agents (fluorinated surfactants) for a controlled and sustained release relevant to the conservation of cultural heritage. Additionally, anio…
Electronic Structure of Oxygen Dangling Bond in GlassySiO2: The Role of Hyperconjugation
2003
The electronic structure and the nature of optical transitions in oxygen dangling bond in silica glass, the nonbridging oxygen hole center (NBOHC), were calculated. The calculation reproduced well the peak positions and oscillator strengths of the well-known optical absorption bands at 2.0 and 4.8 eV, and of the recently discovered absorption band at 6.8 eV. The 2.0 eV band was attributed to transition from the $\ensuremath{\sigma}$ bond between Si and dangling oxygen to nonbonding $\ensuremath{\pi}$ orbital on the dangling oxygen. The uniquely small electron-phonon coupling associated with the 2.0 eV transition is explained by stabilization of Si-O bond in the excited state by hyperconjuga…