The role of long-lived dark states in the photoluminescence dynamics of poly(phenylene vinylene) conjugated polymers. II. Excited-state quenching versus ground-state depletion

2003 ◽  
Vol 118 (9) ◽  
pp. 4297-4305 ◽  
Author(s):  
S.-H. Lim ◽  
T. G. Bjorklund ◽  
C. J. Bardeen
Keyword(s):  
Excited State ◽  
Conjugated Polymers ◽  
Ground State ◽  
Phenylene Vinylene ◽  
Excited State Quenching

A meta-analysis and review examining a possible role for oxidative stress and singlet oxygen in diverse diseases

2017 ◽  
Vol 474 (16) ◽  
pp. 2713-2731 ◽  
Author(s):  
Athinoula L. Petrou ◽  
Athina Terzidaki
Keyword(s):  
Oxidative Stress ◽  
Excited State ◽  
Singlet Oxygen ◽  
Ground State ◽  
Meta Analysis ◽  
Common Mechanism ◽  
High Electron ◽  
A Value ◽  
First Excited State

From kinetic data (k, T) we calculated the thermodynamic parameters for various processes (nucleation, elongation, fibrillization, etc.) of proteinaceous diseases that are related to the β-amyloid protein (Alzheimer's), to tau protein (Alzheimer's, Pick's), to α-synuclein (Parkinson's), prion, amylin (type II diabetes), and to α-crystallin (cataract). Our calculations led to ΔG≠ values that vary in the range 92.8–127 kJ mol−1 at 310 K. A value of ∼10–30 kJ mol−1 is the activation energy for the diffusion of reactants, depending on the reaction and the medium. The energy needed for the excitation of O2 from the ground to the first excited state (1Δg, singlet oxygen) is equal to 92 kJ mol−1. So, the ΔG≠ is equal to the energy needed for the excitation of ground state oxygen to the singlet oxygen (1Δg first excited) state. The similarity of the ΔG≠ values is an indication that a common mechanism in the above disorders may be taking place. We attribute this common mechanism to the (same) role of the oxidative stress and specifically of singlet oxygen, (1Δg), to the above-mentioned processes: excitation of ground state oxygen to the singlet oxygen, 1Δg, state (92 kJ mol−1), and reaction of the empty π* orbital with high electron density regions of biomolecules (∼10–30 kJ mol−1 for their diffusion). The ΔG≠ for cases of heat-induced cell killing (cancer) lie also in the above range at 310 K. The present paper is a review and meta-analysis of literature data referring to neurodegenerative and other disorders.

Investigations of a Metastable Dependence on the Ionization of Sputtered Species in Neon Glow Discharges

1991 ◽  
Vol 45 (10) ◽  
pp. 1656-1664 ◽  
Author(s):  
D. Serxner ◽  
R. L. Smith ◽  
K. R. Hess
Keyword(s):  
Excited State ◽  
Glow Discharge ◽  
Ground State ◽  
Copper Ion ◽  
Penning Ionization ◽  
Glow Discharges ◽  
Discharge Gas ◽  
Discharge Pressure ◽  
Ion Emission

Optical investigations of a low-pressure (0.3–4.0 Torr), low-current (1–4 mA), coaxial geometry glow discharge operating with neon as the fill gas are described. Studies were designed to experimentally illustrate the role of neon metastable atoms in the population of selected excited-state ion levels of copper atoms sputtered from a brass cathode. Methane was employed as a quenching agent to reduce the neon metastable population, and ion emission signals from a variety of copper ion transitions showed a decrease in intensity corresponding to the introduction of methane to the plasma. In addition, with variations in discharge pressure, a correlation between the number of neon metastables and the strength of the ion emission signals was observed. These results provide evidence that Penning ionization is an important mechanism for the ionization of sputtered atoms in neon glow discharges, similar to the results obtained for an argon system. Finally, a brief comparison of the neon and argon systems was made which showed the neon discharge gas to be more efficient at populating the monitored copper ion levels. This is most likely due to the higher energy of the neon metastables, which permits the direct population of these ion levels from the copper ground state.

The role of long-lived dark states in the photoluminescence dynamics of phenylene vinylene conjugated polymers

2002 ◽  
Vol 117 (1) ◽  
pp. 454-461 ◽  
Author(s):  
Sang-Hyun Lim ◽  
Thomas G. Bjorklund ◽  
Kevin M. Gaab ◽  
Christopher J. Bardeen
Keyword(s):  
Conjugated Polymers ◽  
Phenylene Vinylene

Perturbation of the fuchsone chromophore by 3,5-methyl substitution. Sterically crowded exocyclic double bond

1981 ◽  
Vol 46 (10) ◽  
pp. 2540-2556 ◽  
Author(s):  
Bohumír Koutek ◽  
Lubomír Musil ◽  
Jiří Velek ◽  
Antonín Lyčka ◽  
Dobroslav Šnobl ◽  
...  
Keyword(s):  
Dipole Moment ◽  
Excited State ◽  
Ground State ◽  
Bathochromic Shift ◽  
Exocyclic Double Bond ◽  
Wavelength Band ◽  
Methyl Substitution ◽  
Steric Crowding ◽  
Hypochromic Effect

Several 3,5-methyl substituted fuchsones have been synthesized and characterized by means of UV and NMR spectroscopy as well as dipole moment measurements. Two basic types of behaviour of the longest wavelength band have been found for these derivatives in comparison to 2,6-substituted analogues i.e. hypochromic effect and bathochromic shift. These effects can be attributed to a steric crowding of the C(4)-C(7) double bonds. The role of the steric interactions in the ground state and in the excited state is discussed.

scholarly journals Correction: Role of solute-solvent hydrogen bonds on the ground state and the excited state proton transfer in 3-hydroxyflavone. A systematic spectrophotometric study

2020 ◽  
Vol 19 (6) ◽  
pp. 858-859
Author(s):  
Simone Lazzaroni ◽  
Daniele Dondi ◽  
Alberto Mezzetti ◽  
Stefano Protti
Keyword(s):  
Excited State ◽  
Hydrogen Bonds ◽  
Proton Transfer ◽  
Ground State ◽  
Spectrophotometric Study ◽  
Excited State Proton Transfer

Correction for ‘Role of solute-solvent hydrogen bonds on the ground state and the excited state proton transfer in 3-hydroxyflavone. A systematic spectrophotometric study’ by Simone Lazzaroni et al., Photochem. Photobiol. Sci., 2018, 17, 923–933, DOI: 10.1039/C8PP00053K.

Intramolecular excited-state charge-transfer interactions and the role of ground-state conformations

1980 ◽  
Vol 84 (21) ◽  
pp. 2696-2698 ◽  
Author(s):  
Ying Wang ◽  
Michael K. Crawford ◽  
Kenneth B. Eisenthal
Keyword(s):  
Excited State ◽  
Charge Transfer ◽  
Ground State ◽  
State Charge
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