scholarly journals Role of Fe substitution and quenching rate on the formation of various quasicrystalline and related phases

2001 ◽  
Vol 24 (3) ◽  
pp. 257-264 ◽  
Author(s):  
Varsha Khare ◽  
R. S. Tiwari ◽  
O. N. Srivastava
Keyword(s):  
Quenching Rate ◽  
Fe Substitution

scholarly journals Спектральное исследование фотодинамических процессов в системе C-=SUB=-60-=/SUB=--(н-метилпирролидон)-кислород

2021 ◽  
Vol 129 (12) ◽  
pp. 1493
Author(s):  
И.М. Кисляков ◽  
И.М. Белоусова ◽  
В.М. Киселев ◽  
И.В. Багров ◽  
А.М. Стародубцев ◽  
...  
Keyword(s):  
Quantum Yield ◽  
Singlet Oxygen ◽  
Transient Absorption ◽  
Rapid Quenching ◽  
Quenching Rate ◽  
Broadband Absorption ◽  
Laser Pumping ◽  
Time Dependencies ◽  
Quenching Rate Constant

The processes of photoexcitation and energy transfer in an air-saturated solution of fullerene C60 in n-methylpyrrolidone are studied. With femtosecond laser pumping at a wavelength л(p) = 520 nm, transient absorption spectra were obtained in the range 470-750 nm. Broadband absorption is observed at л > 650 nm as a result of aggregation of fullerene molecules, characterized by a short decay time of the picosecond scale. The analysis of the time dependencies indicates the presence of several processes. Within the proposed interpretation, we state a remarkable reduction in the time of singlet-triplet intersystem crossing with an increase of nanocluster size while the rapid quenching of the singlet state varies only slightly. The quantum yield of the triplet state can therefore increase, reaching 0.14. The phosphorescence spectra of singlet oxygen with a maximum at л = 1276 nm were measured with LED excitation at various wavelengths in the range 370-625 nm. The lifetime and quenching rate constant of singlet oxygen in n-methylpyrrolidone are determined. The combined quantum yield of triplet fullerene and singlet oxygen in n-methylpyrrolidone is estimated as 0.74. The efficiency spectra of the singlet oxygen photosensibilization in the C60-(n-methylpyrrolidone)-oxygen system are obtained, indicating the increasing role of large nanoclusters in this process during aging of the solution.

scholarly journals Role of Fe substitution on the anomalous magnetocaloric and magnetoresistance behaviour in Tb(Ni1−xFex)2compounds

2006 ◽  
Vol 18 (48) ◽  
pp. 10775-10786 ◽  
Author(s):  
Niraj K Singh ◽  
K G Suresh ◽  
D S Rana ◽  
A K Nigam ◽  
S K Malik
Keyword(s):  
Fe Substitution

Exploring the role of Fe substitution on electronic, structural, and magnetic properties of La2NiMnO6 double perovskites

2021 ◽  
Vol 127 (3) ◽  
Author(s):  
Mohammad Nasir ◽  
Mahmud Khan ◽  
E. G. Rini ◽  
Sunday Arome Agbo ◽  
Somaditya Sen
Keyword(s):  
Magnetic Properties ◽  
Double Perovskites ◽  
Structural And Magnetic Properties ◽  
Fe Substitution

Quenching of the excitation energy of coumarin dyes by aniline

2013 ◽  
Vol 91 (11) ◽  
pp. 976-980 ◽  
Author(s):  
D. Nagaraja ◽  
R.M. Melavanki ◽  
N.R. Patil ◽  
R.A. Kusanur ◽  
J. Thipperudrappa ◽  
...  
Keyword(s):  
Activation Energy ◽  
Steady State ◽  
Rate Parameter ◽  
Quenching Mechanism ◽  
Quenching Rate ◽  
Time Resolved ◽  
Quenching Mechanisms ◽  
Activation Energy Of Diffusion ◽  
Coumarin Dyes

Quenching mechanisms of coumarin dyes, namely 6-bromo-3-[1-(4,5-dicarbomethoxy-1,2,3-triazoloacetyl)]coumarin (6BDTC) and 8-methoxy-3-[1-(4,5-dicarbomethoxy-1,2,3-triazoloacetyl)]coumarin (8MDTC), were carried out in toluene by adopting two methods, namely steady-state and time-resolved methods, to understand the role of diffusion in the quenching mechanism. The solute molecules were excited by UV radiation of wavelength 360 and 330 nm. Various quenching parameters like frequency of encounter (kd), probability of quenching per encounter (p and p′), and quenching rate parameter (kq and [Formula: see text]) were experimentally determined in all the solvents. Activation energy of quenching (Ea and [Formula: see text]) was also determined by using the literature values of activation energy of diffusion (Ed). It was found that the values of Ea (and [Formula: see text]) were less than Ed indicating that the quenching reactions are more significantly influenced by diffusion.

The interaction between the excited triplet state of ketones and olefins: the role of triplet exciplexes

1979 ◽  
Vol 57 (3) ◽  
pp. 342-347 ◽  
Author(s):  
Rafik O. Loutfy ◽  
S. K. Dogra ◽  
R. W. Yip
Keyword(s):  
Rate Constants ◽  
Binding Energies ◽  
Acetonitrile Solution ◽  
Important Process ◽  
Quenching Rate ◽  
Triplet Energy ◽  
Excited Triplet ◽  
Triplet Exciplexes ◽  
Diffusion Controlled

The quenching of triplet acetone in degassed acetonitrile solution by electron-rich and electron-deficient olefins has been measured by flash emission technique. With the exception of fumaronitrile, the efficiency of quenching of triplet ketones by olefins is not determined by the triplet energy of the ketone, but by the ability of the excited ketone to donate or accept electrons. The results are consistent with the assumption that back dissociation of the triplet exciplex is an important process in the overall reaction and accounts for quenching rate constants which are less than those for diffusion-controlled reactions. Lifetimes and binding energies of the triplet exciplexes have been estimated.

Oxidation of 1-N2-etheno-2′-deoxyguanosine by singlet molecular oxygen results in 2′-deoxyguanosine: a pathway to remove exocyclic DNA damage?

2018 ◽  
Vol 399 (8) ◽  
pp. 859-867
Author(s):  
Glaucia Regina Martinez ◽  
Hulyana Brum ◽  
Guilherme Lanzi Sassaki ◽  
Lauro Mera de Souza ◽  
Ana Paula de Melo Loureiro ◽  
...  
Keyword(s):  
Molecular Oxygen ◽  
Dna Adducts ◽  
High Performance ◽  
Chemical Reactivity ◽  
Water Soluble ◽  
Modified Nucleosides ◽  
Quenching Rate ◽  
Singlet Molecular Oxygen ◽  
Aldehyde Groups

Abstract Exocyclic DNA adducts are considered as potential tools for the study of oxidative stress-related diseases, but an important aspect is their chemical reactivity towards oxidant species. We report here the oxidation of 1-N2-etheno-2′-deoxyguanosine (1,N2-εdGuo) by singlet molecular oxygen (1O2) generated by a non-ionic water-soluble endoperoxide [N,N′-di(2,3-dihydroxypropyl)-1,4-naphthalenedipropanamide endoperoxide (DHPNO2)] and its corresponding oxygen isotopically labeled [18O]-[N,N′-di(2,3-dihydroxypropyl)-1,4- naphthalenedipropanamide endoperoxide (DHPN18O2)], and by photosensitization with two different photosensitizers [methylene blue (MB) and Rose Bengal (RB)]. Products detection and characterization were achieved using high performance liquid chromatography (HPLC) coupled to ultraviolet and electrospray ionization (ESI) tandem mass spectrometry, and nuclear magnetic resonance (NMR) analyses. We found that dGuo is regenerated via reaction of 1O2 with the ε-linkage, and we propose a dioxetane as an intermediate, which cleaves and loses the aldehyde groups as formate residues, or alternatively, it generates a 1,2-ethanediol adduct. We also report herein the quenching rate constants of 1O2 by 1,N2-εdGuo and other etheno modified nucleosides. The rate constant (kt) values obtained for etheno nucleosides are comparable to the kt of dGuo. From these results, we suggest a possible role of 1O2 in the cleanup of etheno adducts by regenerating the normal base.

scholarly journals Study of Role of Silver Nanoparticles on Spectroscopic Properties of a KetocyanineDye

2016 ◽  
Vol 15 (1) ◽  
pp. 1-16
Author(s):  
Thipperudrappa J
Keyword(s):  
Silver Nanoparticles ◽  
Chemical Reduction ◽  
Spectroscopic Properties ◽  
Chemical Reduction Method ◽  
Quenching Rate ◽  
Number Of Binding Sites ◽  
Volmer Plot ◽  
Quenching Mechanisms ◽  
Static Part

The role of silver nanoparticles on spectroscopic properties of the ketocyaninedye 2,5-di[(E)-1-(4- dimethylaminophenyl) methylidine]-1-cyclopentanone (2,5-DMAPMC) has been investigated using absorption and fluorescence spectroscopy. Silver nanoparticles are synthesized by chemical reduction method and estimated size from SEM measurements is 22 nm. The changes in absorption spectrum of dye in the presence of silver nanoparticles suggest the possible interaction with silver nanoparticles. The Stern-Volmer plot of fluorescence quenching is found to be nonlinear showing positive deviation. The magnitude of quenching rate parameter and fluorescence lifetime measurements indicates the presence of both collisional and static quenching mechanisms. The binding constant and number of binding sites for static part of the quenching have been

Fluorescence quenching of 6BDTC by aniline in different solvents

2013 ◽  
Vol 91 (11) ◽  
pp. 966-970 ◽  
Author(s):  
D. Nagaraja ◽  
R.M. Melavanki ◽  
N.R. Patil
Keyword(s):  
Activation Energy ◽  
Coumarin Derivative ◽  
Rate Parameter ◽  
Quenching Mechanism ◽  
Quenching Rate ◽  
Steady State Method ◽  
Quenching Mechanisms ◽  
State Method ◽  
Activation Energy Of Diffusion

Quenching mechanisms of coumarin derivative 6-bromo-3-[1-(4,5-dicarbomethoxy-1,2,3-triazoloacetyl)]coumarin (6BDTC) were carried out in different solvents using the steady-state method to understand the role of diffusion in the quenching mechanism. The solute was excited by UV radiation of wavelength 360 nm. Various quenching parameters like frequency of encounter, kd; probability of quenching per encounter, p; and quenching rate parameter, kq, were experimentally determined for all solvents. Activation energies of quenching, Ea, were also determined by using the literature values of activation energy of diffusion, Ed. It was found that the values of Ea were less than Ed in all solvents indicating that the quenching reactions are more significantly influenced by material diffusion.

scholarly journals Studies of Li2Fe0.9M0.1SO Antiperovskite Materials for Lithium–Ion Batteries: The Role of Partial Fe2+ to M2+ Substitution

2021 ◽  
Vol 9 ◽  
Author(s):  
Mikhail V. Gorbunov ◽  
Salvatore Carocci ◽  
Ignacio G. Gonzalez Martinez ◽  
Volodymyr Baran ◽  
Daria Mikhailova
Keyword(s):  
Electrochemical Performance ◽  
Specific Capacity ◽  
Lithium Ion ◽  
X Ray Diffraction ◽  
X Ray ◽  
Jahn Teller ◽  
Current Densities ◽  
X Ray Absorption ◽  
Fe Substitution

Cubic Li2Fe0.9M0.1SO antiperovskites with M–Co2+, or Mn2+ were successfully synthesized by a solid-state technique, and studied as cathode materials in Li-batteries. The influence of the Co, and Mn cation substitution of Fe in Li2FeSO on the resulting electrochemical performance was evaluated by galvanostatic cycling, while the reaction mechanism was explored by applying operando X-ray absorption and X-ray diffraction techniques using synchrotron radiation facilities. Even 10% Fe-substitution by these metals completely changes the structural behavior of the material upon Li-removal and insertion, in comparison to Li2FeSO. The Co-substitution significantly improves cyclability of the material at high current densities in comparison to the non-substituted material, reaching a specific capacity of 250 mAh/g at 1C current density. In contrast, the Mn-substitution leads to deterioration of the electrochemical performance because of the impeded kinetics, which may be caused by the appearance of a second isostructural phase due to formation of Jahn-Teller Mn3+ cations upon delithiation.

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