Development of high-voltage pulse-slicer unit with variable pulse duration for pulse radiolysis system

Upadhyay, J.; Sharma, Mrinalini; Navathe, C. P.; Toley, Madhu; Shinde, Suhashine; Nadkarni, Shirish A.; Sarkar, S.K.

doi:10.1063/1.3685245

Cited by 10 publications

(5 citation statements)

References 10 publications

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“…Pulse radiolysis experiments were carried out with high-energy electron pulses (7 MeV, 500 ns) obtained from a linear electron accelerator, and the details are given elsewhere. , The transient species formed on pulse radiolysis were detected by the optical absorption method. An aerated aqueous solution of KSCN (1 × 10 –2 M) was used for determining the dose delivered per pulse, monitoring the transient (SCN) 2 •– at 475 nm, using Gε 475nm = 2.59 × 10 –4 m 2 /J.…”

Section: Methodsmentioning

confidence: 99%

Radical Cations of Aromatic Selenium Compounds: Role of Se···X Nonbonding Interactions

Singh¹,

Thomas²,

Sawant³

et al. 2013

J. Phys. Chem. A

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Selenium centered radical cations in aliphatic selenium compounds are stabilized by formation of two-center-three electron (2c-3e) hemi bonds either with nearby heteroatoms forming monomer radicals or with selenium atoms of the parent molecules forming dimer radicals. Such radicals in aromatic selenium compounds would generally be stabilized as monomers by the delocalization of the spin density along the aromatic ring. To test the assumption if aromatic selenides having Se···X nonbonding interactions can show different types of radical cations, we have performed pulse radiolysis studies of three structurally related aromatic selenium compounds and the results have been substantiated with cyclic voltammetry and quantum chemical calculations. The three aromatic selenium compounds have functional groups like -CH2N(CH3)2 (1), -CH2OH (2), and -CH3 (3) at ortho position to the -SeCH3 moiety. The energy of Se···X nonbonding interactions (E(nb)) for these compounds is in the order 1 (Se···N) > 2 (Se···O) > 3 (Se···H). Radical cations, 1(•+), 2(•+) and 3(•+) were produced by the one-electron oxidation of 1, 2 and 3 by radiolytically generated (•)OH and Br2(•-) radicals. Results on transient spectra, lifetime, and secondary reactions of 1(•+), 2(•+), and 3(•+) indicated that 1(•+) shows a significantly different absorption spectrum, longer lifetime, and less oxidizing power compared to those of 2(•+) or 3(•+). Quantum chemical calculations suggested that 1(•+) is stabilized by the formation of a 2c-3e bond between Se and N atoms, whereas 2(•+) and 3(•+) acquire stability through the delocalization of the spin density on the aromatic ring. These results provide evidence for the first time that stronger nonbonding interactions between Se···N in the ground state, facilitate the formation of stabilized radical cations, which can significantly influence the redox chemistry and the biological activity of aromatic selenium compounds.

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Section: Methodsmentioning

confidence: 99%

Radical Cations of Aromatic Selenium Compounds: Role of Se···X Nonbonding Interactions

Singh¹,

Thomas²,

Sawant³

et al. 2013

J. Phys. Chem. A

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“…37 Aerated aqueous solution of KSCN (1 Â 10 À2 M) was used for determining the dose delivered per pulse, monitoring the transient (SCN) 2 c À at 475 nm, using G3 475 ¼ 2.59 Â 10 À4 m 2 J À1 . 37 Aerated aqueous solution of KSCN (1 Â 10 À2 M) was used for determining the dose delivered per pulse, monitoring the transient (SCN) 2 c À at 475 nm, using G3 475 ¼ 2.59 Â 10 À4 m 2 J À1 .…”

Section: Methodsmentioning

confidence: 99%

“…Pulse radiolysis experiments were carried out with highenergy electron pulses (7 MeV, 100 ns) obtained from a linear electron accelerator and the details are given elsewhere. 37 Aerated aqueous solution of KSCN (1 Â 10 À2 M) was used for determining the dose delivered per pulse, monitoring the transient (SCN) 2 c À at 475 nm, using G3 475 ¼ 2.59 Â 10 À4 m 2 J À1 . Here, G denotes the radiation chemical yield in mol J À1 and 3 denotes the molar extinction coefficient in m 2 mol À1 .…”

Section: Methodsmentioning

confidence: 99%

Effect of alkyl chain length on one-electron oxidation of bis(alkyl carboxylic acid) selenides: implication on their antioxidant ability

et al. 2015

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One-electron redox reactions of three bis(alkyl carboxylic acid) selenide (SeC) derivatives viz., seleno bis(butanoic acid) (SeBA), seleno bis(propanoic acid) (SePA) and seleno bis(ethanoic acid) (SeEA), were carried out in aqueous solutions using nanosecond pulse radiolysis and the resultant transients were detected by absorption spectroscopy. SeC reacted with cOH radicals to form hydroxyl selenouranyl radicals (pSerOH) which subsequently gave different transient species, like the selenium centered radical cation (SeCc + ), dimer radical cation (pSerSe) + , or a selenium-carboxyl oxygen stabilized monomer radical (pSerO). The relative yield of these transient species depended on pH, concentration of SeC and position of the carboxylate functional group. SeEA and SeBA gave exclusively (pSerSe) + absorbing at 490 nm, while in the case of SePA, along with (pSerSe) + , (pSerO) was also formed. The stability of (pSerSe) + was estimated in terms of the equilibrium constant and was in the order SeBA > SeEA > SePA. Secondary electron transfer reactions of the transients were performed with 2,2 0 -azinobis(3-ethylbenzthiazoline-6-sulphonic acid), thionine and methyl viologen. The study showed that SeCc + undergoes decarboxylation with the formation of the corresponding a-(alkylseleno)alkyl radical and the yield of CO 2 formed was in the order SeEA < SeBA < SePA. The formation of a stabilised monomer radical cation in SePA is responsible for its lower yield of CO 2 and the same is reflected in its higher free radical scavenging antioxidant activity, established by comparing the rate constants for scavenging of peroxyl radicals.

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“…32 The pulse radiolysis system using 7 MeV electrons has been described elsewhere, 33 which had been further modified to obtain a variable pulse duration using a high-voltage pulseslicer unit. 34 In brief, the light beam after passing through the sample and a combination of lens and mirror is focused onto the entrance slit of the monochromator (Kratos Analytical Instruments Inc., model GMA 252) through an appropriate long-pass filter (in the present case, a 530 nm filter is used). The exit slit of the monochromator is attached to a photomultiplier tube (PMT-Hamamatsu TV Co., Japan, model R-955).…”

Section: ■ Introductionmentioning

confidence: 99%

Direct Observation of Solvated Electrons in Deep Eutectic Solvents: Efficient Capture of Presolvated Electrons by DNA Base

Das

Adhikari

2018

J. Phys. Chem. B

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The solvated electron being the simplest form of an extremely reactive intermediate is of great fundamental interest in chemistry, physics, and biology since its discovery. Recently, deep eutectic solvents (DESs) have been in focus as biodegradable and cost-effective alternative to ionic liquids (ILs) for different applications. These include areas where electron transport and transfer processes are involved. Herein, we present the first report on the existence, yield, and properties of solvated electrons in three deep eutectic solvents, reline, ethaline, and glyceline, composed of choline chloride as a hydrogen bond acceptor and urea, ethylene glycol, and glycerol (Gly) as hydrogen bond donors, respectively, at a molar ratio of 1:2. The varied transient absorption spectra of solvated electrons in these DESs have been explained on the basis of polarity, hydrogen-bonding effect, and the moieties responsible for creating the environment for solvation. The yield and average lifetime follow the trends in viscosity as well as the reactivity of electrons with the components. The C value, a measure of the efficiency of scavenging presolvated electrons, is the highest in ethaline in the case of nitrate ions, which indicates the slowest solvation process in this DES. The presolvated electron capture by a DNA base, an aspect considered to be important in cancer radiotherapy, could be monitored conveniently in these liquids at a much longer time scale compared to that reported in aqueous solutions. Bimolecular rate constants for the reaction of solvated electrons with nitrate and the DNA base have been calculated and compared in the three DESs. Unlike in ILs, these experimentally obtained values are comparable to the diffusion-controlled rate constants in DESs.

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Development of high-voltage pulse-slicer unit with variable pulse duration for pulse radiolysis system

Cited by 10 publications

References 10 publications

Radical Cations of Aromatic Selenium Compounds: Role of Se···X Nonbonding Interactions

Radical Cations of Aromatic Selenium Compounds: Role of Se···X Nonbonding Interactions

Effect of alkyl chain length on one-electron oxidation of bis(alkyl carboxylic acid) selenides: implication on their antioxidant ability

Direct Observation of Solvated Electrons in Deep Eutectic Solvents: Efficient Capture of Presolvated Electrons by DNA Base

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