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Auger-emitting radionuclides have potential application in targeted radiotherapy, particularly for metastatic cancers. This possibility, especially, is stemmed from their characteristic short-range (a few μm) in biological systems allowing localization of high dose within small tumours. To explore this potential application, a Geant4 Monte Carlo toolkit has been employed to simulate the energy deposition of different radionuclides in a water model. The Geant4 Monte Carlo toolkit has model packages to simulate the interaction of radiation with matter and with diverse applications such as studies in science and medicine. In this study, the Geant4-DNA package was used to simulate the radiolytic yields induced by some Auger electron-emitting (AE) radionuclides including; I-131, I-125 and Pd-103, In-111, Ru-97 and Rh-103 m in water model. The results showed that the transient yield of the radiolytic species is characterized by the kinetic energies of the emitted electrons. It was observed that almost all the radionuclides, except I-131, deposited more energy in their proximity thereby inducing a high density of spurs to interact in a short time. It is, therefore, important to consider the kinetic energies of the emitted particles in choosing a radionuclide for specified targeted radiotherapy. This means that apart from their toxicity, compatibility with chelator and carrier molecules, and method of production, we can predict radionuclides such as In-111, Ru-97, Pb-103 m and I-125 could be relevant for targeted radiotherapy for the treatment of metastasis lesions, or tiny tumours at the cellular level, and tumours after surgical resection.

The radiolytic method is used to synthesize ultrasmall cobalt ferrite nanoparticles, CoFe2O4, exhibiting superparamagnetic properties.

This study investigates the mechanism of dioxygen reduction catalyzed by gold nanoparticles using two electron donors, sodium ascorbate and hydroethidine, focusing on the potential ROS formation, such as O2˙− and H2O2.

Time-resolved identification of surface-bound intermediates on metallic nanocatalysts is imperative to develop an accurate understanding of the elementary steps of CO2 reduction, but remains challenging in particular for carbon dioxide radical anions, CO2•‒. Herein, we use pulse radiolysis to observe the holistic stabilization process of CO2•‒ radicals on well-defined nanoscale metallic sites. The method allows to identify surface-bound intermediates with characteristic transient absorption and the distinct kinetics for three typical metallic nanocatalysts (Cu, Au, and Ni). The interfacial interactions were further investigated by varying the important factors, such as catalyst size and cation in the electrolyte. The spectral data, combined with molecular simulations, highlighted the selectivity of the critical initial step in the CO2 catalytic reduction mechanism, even before CO2•‒ radical dissociation.

The efficient use of renewable high-energy radiation (X/γ-rays or accelerated e‒) as the energy input for the chemical transformation of carbon dioxide (CO2) and water to energy-rich fuels holds new promise for a carbon-neutral, sustainable energy economy; however, such processes are challenging to implement, and require the assistance of catalysts capable of sensitizing the secondary electron scattering and providing active metal sites to bind intermediates. Herein, we report that atomic Cu-Ni dual-metal-sites embedded in a metal-organic framework matrix enable efficient and selective (~ 98%) conversion of CO2 to CH3OH in irradiated aqueous solutions. The reaction is initiated by the direct generation of CO2•‒ radicals via aqueous electrons attachment, followed by a series of interfacial reactions. We showed that the UiO-66(Hf) matrix serves as a radiation sensitizer to break electron yield limitation in water radiolysis, dramatically promoting CO2 activation and conversion efficiency. With the synergistic metal centers and a hydroxyl radical scavenger, we achieved stable and selective CH3OH production over multiple irradiation cycles. Pulse radiolysis experiments with theoretical calculations revealed the transient kinetics occurred on the nanosecond timescale and cascade hydrogenation steps. Our study highlighted an unprecedented catalytic route to produce CH3OH with CO2 feedstock and introduced a desirable atomic structure to improve performance.

This work shows that S-atom substitution in phosphate, controls the directionality of hole transfer processes between base and sugar-phosphate backbone in DNA systems. The investigation combines synthesis, electron spin resonance (ESR) studies in supercooled homogeneous solution, pulse radiolysis in aqueous solution at ambient temperature and density functional theory (DFT) calculations of in-house synthesized model compound dimethylphosphorothioate (DMTP(O(−))=S) and nucleotide (5’-O-methoxyphosphorothioyl-2’-deoxyguanosine (G-P(O(−))=S)). ESR investigations show that DMTP(O(−))=S reacts with Cl(2)(•−) to form the σ(2)σ*(1) adduct radical -P-S∸Cl which subsequently reacts with DMTP(O(−))=S to produce [-P-S∸S-P-](−). -P-S∸Cl in G-P(O(−))=S undergoes hole transfer to Gua forming the cation radical (G(•+)) via thermally activated hopping. However, pulse radiolysis measurements show that DMTP(O(−))=S forms the thiyl radical (-P-S•) by one-electron oxidation which did not produce [-P-S∸S-P-](−). Gua in G-P(O(−))=S is oxidized unimolecularly by -P-S• intermediate in sub-picosecond range. DFT thermochemical calculations explain the differences in ESR and pulse radiolysis results obtained at different temperatures.

The reactivity of presolvated electrons with CO2 and N2O was studied in the gas pressure range of 1 to 52 bar. To measure this reactivity, a home-made spectroscopic cell with liquid circulation was developed which can work up to 70 bar of gas pressure. The efficiency of presolvated electron scavenging was determined from the decrease of the solvated electron yield after the application of a 5 ps electron pulse. In addition, the reaction rate between these molecules and solvated electrons was directly determined at gas pressures below the gas critical point, which is in agreement with those presented in the literature measured at gas pressures below

Metal nanoparticles can catalyze reactions involving organic free radicals. From the first studies focused on the catalytic reduction of water by free radicals until today, the catalytic oxidation of organic radicals has not received attention. In this work, we present the results on the catalytic activity of gold nanoparticles in the oxidation of 2-propanol to acetone and acetanilide hydroxylation during water radiolysis. A detailed reaction mechanism of α-hydroxyisopropyl radical oxidation is discussed, explaining the increase in acetone formation by ca. 340% in the presence of gold nanoparticles. In the case of acetanilide hydroxylation in the presence of nanoparticles, a strong effect of oxygen in the reaction mechanism was observed: the increase in the oxygen concentration from 0 to 1.22 mM leads to a 40-fold decrease in hydroxylation product formation. This observation is unexpected since, in the absence of gold nanoparticles, oxygen stimulates hydroxylation reactions. We propose that in the presence of both oxygen and nanoparticles, oxygen attaches first to acetanilide OH-adducts, and then nanoparticles catalyze the oxidation of peroxyl type radicals, which does not lead to the formation of hydroxylation products.

The early mechanisms by which ionizing rays damage biological structures by so-called direct effects are largely elusive. In a recent picosecond pulse radiolysis study of concentrated uridine monophosphate solutions [J. Ma, S. A. Denisov, J.-L. Marignier, P. Pernot, A. Adhikary, S. Seki and M. Mostafavi, J. Phys. Chem. Lett., 2018, 9, 5105], unexpected results were found regarding the oxidation of the nucleobase. The signature of the oxidized nucleobase could not be detected 5 ps after the electron pulse, but only the oxidized phosphate, raising intriguing questions about the identity of charge-transfer mechanisms that could explain the absence of U+. We address here this question by means of advanced first-principles atomistic simulations of solvated uridine monophosphate, combining Density Functional Theory (DFT) with polarizable embedding schemes. We contrast three very distinct mechanisms of charge transfer covering the atto-, femto- and pico-second timescales. We first investigate the ionization mechanism and subsequent hole/charge migrations on a timescale of attoseconds to a few femtoseconds under the frozen nuclei approximation. We then consider a nuclear-driven phosphate-to-oxidized-nucleobase electron transfer, showing that it is an uncompetitive reaction channel on the sub-picosecond timescale, despite its high exothermicity and significant electronic coupling. Finally, we show that non-adiabatic charge transfer is enabled by femtosecond nuclear relaxation after ionization. We show that electronic decoherence and the electronic coupling strength are the key parameters that determine the hopping probabilities. Our results provide important insight into the interplay between electronics and nuclear motions in the early stages of the multiscale responses of biological matter subjected to ionizing radiation.

Substitution of the thymidine moiety in DNA by C5-subsituted halogenated thymidine analogs causes significant augmentation of radiation damage in living cells. However, the molecular pathway involved in such radiosensitization process has not been clearly elucidated to date in solution at room temperature. So far, low-energy electron (LEEs; 0–20 eV) under vacuum condition and solvated electrons (e(sol)(−)) in solution are shown to produce the σ-type C5-centered pyrimidine base radical through dissociative electron attachment involving carbon-halogen bond breakage. Formation of this σ-type radical and its subsequent reactions are proposed to cause cellular radiosensitization. Here, we report time-resolved measurements at room temperature showing that a radiation-produced quasi-free electron (e(qf)(−)) in solution promptly breaks the C5-halogen bond in halopyrimidines forming the σ-type C5 radical via an excited transient anion radical. These results demonstrate the importance of ultrafast reactions of e(qf)(−) which are extremely important in Chemistry, Physics, and Biology, including tumor radiochemotherapy.

The present study proposes a new approach for direct CO 2 conversion using primary radicals from water irradiation. In order to ensure reduction of CO 2 into CO 2 •- by all the hydrated electrons, we use formate ions to scavenge simultaneously the parent oxidizing radicals H • and OH • producing the same transient CO 2 •- radicals. Conditions are optimized to obtain the highest conversion yield of CO 2 . The goal is achieved under mild conditions of room temperature, neutral pH and 1 atm of CO 2 pressure. All the available radicals are exploited for selectively converting CO 2 into oxalate that is accompanied by H 2 evolution. Besides, at high CO 2 pressure, CO is also produced via presolvated electron scavenging and the H • radicals with CO 2 •- . The mechanism presented accounts for the results and also sheds light on the data in the literature. The radiolytic approach is a mild and scalable route of direct CO 2 capture at the source in industry and the products, oxalate salt and H 2 , can be easily separated.

The present study proposes a new approach for direct CO

The excess electron in solution is a highly reactive radical involved in various radiation-induced reactions. Its solvation state critically determines the subsequent pathway and rate of transfer. For instance, water plays a dominating role in the electron-induced dealkylation of n-tributyl phosphate in actinide extraction processing. However, the underlying electron solvation processes in such systems are lacking. Herein, we directly observed the solvation dynamics of electrons in H-bonded water and n-tributyl phosphate (TBP) binary solutions with a mole fraction of water (Xw) varying from 0.05 to 0.51 under ambient conditions. Following the evolution of the absorption spectrum of trapped electrons (not fully solvated) with picosecond resolution, we show that electrons statistically distributed would undergo preferential solvation within water molecules extracted in TBP. We determine the time scale of excess electron full solvation from the deconvoluted transient absorption-kinetical data. The process of solvent reorganization accelerates by increasing the water molar fraction, and the rate of this process is 2 orders of magnitude slower compared to bulk water. We assigned the solvation process to hydrogen network reorientation induced by a negative charge of the excess electron that strongly depends on the local water environment. Our findings suggest that water significantly stabilizes the electron in a deeper potential than the pure TBP case. In its new state, the electron is likely to inhibit the dealkylation of extractants in actinide separation.

International audience; The ability of gold nanoparticles (AuNPs) to catalyze reactions involving radicals is poorly studied. However, AuNPs are used in applications where chemical reactions involving transient radicals occur. Herein, we investigate AuNPs’ catalytic effect on 2-propanol oxidation and acetanilide hydroxylation in aqueous solutions under ionizing radiation at room temperature. In both cases, the presence of AuNPs led to selective oxidation of organic radicals, significantly changing the products’ composition and ratio. Based on these observations, we stress how AuNPs’ catalytic activity can affect the correctness of reactive oxygen species concentration determination utilizing organic dyes. We also provide a discussion on the role of AuNPs’ catalytic activity in the radiosensitization effect actively studied for radiotherapy.

Numerous additives are used in the electrolytes of lithium-ion batteries, especially for the formation of an efficient solid electrolyte interphase at the surface of the electrodes. Understanding the degradation processes of these compounds is thus important; they can be seen through radiolysis. In the case of fluoroethylene carbonate (FEC), picosecond pulse radiolysis experiments evidenced the formation of FEC.- . This radical is stabilized in neat FEC, whereas the ring opens to form more stable radical anions when FEC is a solute in other solvents, as confirmed by quantum chemistry calculations. In neat FEC, pre-solvated electrons primarily undergo attachment rather than solvation. On long timescales, the gases produced (H2 , CO, and CO2 ) were quantified. A reaction scheme for both the oxidizing and reducing pathways at stake in irradiated FEC is proposed. This work shows that the nature of the primary species formed in FEC depends on the amount of FEC in the solution.

International audience; Imogolite nanotubes are potentially promising co-photocatalysts because they are predicted to have curvature-induced, efficient electron-hole pair separation. This prediction has however not yet been experimentally proven. Here, we investigated the behavior upon irradiation of these inorganic nanotubes as a function of their water content to understand the fate of the generated electrons and holes. Two types of aluminosilicate nanotubes were studied: one was hydrophilic on its external and internal surfaces (IMO-OH) and the other had a hydrophobic internal cavity due to Si-CH$_3$ bonds (IMO-CH$_3$), with the external surface remaining hydrophilic. Picosecond pulse radiolysis experiments demonstrated that the electrons are efficiently driven outward. For imogolite samples with very few external water molecules (around 1% of the total mass), quasi-free electrons were formed. They were able to attach to a water molecule, generating a water radical anion, which ultimately led to dihydrogen. When more external water molecules were present, solvated electrons, precursors of dihydrogen, were formed. In contrast, holes moved towards the internal surface of the tubes. They mainly led to the formation of dihydrogen and of methane in irradiated IMO-CH$_3$. The attachment of the quasi-free electron to water was a very efficient process and accounted for the high dihydrogen production at low relative humidity values. When the water content increased, 2 electron solvation dominated over attachment to water molecules. Electron solvation led to dihydrogen production, albeit to a lesser extent than quasi-free electrons. Our experiments demonstrated the spontaneous curvature-induced charge separation in these inorganic nanotubes, making them very interesting potential co-photocatalysts.

International audience; Numerous additives are used in electrolytes of lithium-ion batteries, especially for the formation of efficient solid electrolyteinterphase at the surface of the electrodes. It is, therefore, necessary to elucidate the degradation processes of these compoundssince it directly affects the lifetime of the battery. These mechanisms can be obtained through radiolysis. In this work, weinvestigated the degradation mechanisms induced by irradiation in fluoroethylene carbonate (FEC), a cyclic carbonate, whichis an additive commonly used in lithium-ion batteries. The first reaction steps were studied by pulse radiolysis. At longtimescales, the radiolytic yields of produced gases (H$_2$, CO, and CO$_2$) were quantified. Pulse radiolysis experimentsevidenced the formation of the FEC$^{●-}$ radical anion, characterized by an absorption band centered ca. 430 nm. The radicalanion is not detected when FEC is solubilized in other solvents: ethanol, diethylcarbonate, etc. This radical is indeed stabilizedin neat FEC, whereas the ring opens to form more stable radical anions when FEC is a solute in other solvents, as confirmedby calculations. A multi-species deconvolution of the spectrum measured in pure FEC revealed a small absorption bandcentered around 560 nm, attributed to the solvated electron, decaying in ca. 100 ps. In neat FEC, excess electrons primarilyundergo attachment compared to solvation. Together with gas chromatography coupled to mass spectrometry measurements,all these observations have allowed us to propose a reaction scheme for both the oxidizing and reducing pathways at stake inirradiated FEC. This work gives clues for the reaction mechanisms undergone by FEC present in electrolytes of lithium-ionbatteries and evidences that the nature of the primary species formed in FEC depends on the amount of FEC in the solution

International audience; Nucleation and growth of crystallites are induced by the shockwave of a single laser nanosecond pulse in highly supersaturated solutions of potassium nitrate (saltpeter). The kinetics of the turbidity resulting from the light scattering by the growing crystals is observed by time-resolved optical spectroscopy. With an optical path of 10 mm, we first focused on the early part of the growth under various conditions, but it is limited by the detection system to a few percent of the total growth. Remarkably, in this domain and for all supersaturated concentrations studied, the turbidity increases proportionally with time. This zero-order process with an accretion rate constant (k = 4.7 × 107 L mol–1 s–1) implies that the nuclei and growing crystals’ concentration remain constant. This concentration is determined from the final diameter of crystals that are observed to have a bipyramidal shape by transmission electron microscopy (TEM). Moreover, the number of accretion sites per crystal must be constant in this time range and they are identified as the apexes. In complement, the kinetics detected with shorter optical paths permits us to observe larger parts of the total growth (up to 35% with 1 mm of optical path). In this case, after the linear part, the turbidity increase is markedly accelerated, indicating that the number of accretion sites per crystal increases rapidly with the crystal size and that the edges and facet sites also fix the molecules. The complete analysis by a homogeneous kinetics model of the signals obtained under various conditions concludes to an anisotropic growth of the crystals with another accretion rate constant (k′ = 100 L mol–1 s–1) that is much lower on these edges and facet sites than on the apexes. However, this contribution becomes predominant only when the crystals develop to a larger size.

We investigate the oxidation of silver cyanide AgI(CN)2- in water by the OH radical in order to compare this complex with the free cation Ag+ and to measure the influence of the ligands. High-level ab initio calculations of the model species AgII(CN)2· enable the calibration of molecular simulations and the prediction of the oxidized species: AgII(CN)2(H2O)2· and its absorption spectrum, with an intense band at 292 nm and a weaker one at 390 nm. Pulse radiolysis measurements of the oxidation of AgI(CN)2- by the OH radical in water yields a transient species with a broad, intense band at 290 nm and a weaker band at 410 nm at short times after the pulse and a blue shift of the spectrum at longer times. The prediction of the simulations, that the oxidized complex AgII(CN)2(H2O)2· is formed, is confirmed by thermochemistry. Our calculations also suggest that the formation of the OH-adduct is possible only in very basic solution and that the blue shift observed at long times after the pulse is due to disproportionation of the oxidized complex. We also perform molecular simulations of the oxidation of free Ag+ cations by the OH radical. The results are compared to that of the literature and to the results obtained with the AgI(CN)2- complex.

The development of ultra-intense electron pulse for applications needs to be accompanied by the implementation of a practical dosimetry system. In this study four different systems were investigated as dosimeters for low doses with a very high-dose-rate source. First, the effects of ultra-short pulses were investigated for the yields of the Fricke dosimeter based on acidic solutions of ferrous sulfate; it was established that the yields were not significantly affected by the high dose rates, so the Fricke dosimeter system was used as a reference. Then, aqueous solutions of three compounds as fluorescence chemical dosimeters were utilized, each operated at a different solution pH: terephthalic acid - basic, trimesic acid - acidic, and coumarin-3- carboxylic acid (C3CA) - neutral. Fluorescence chemical dosimeters offer an attractive alternative to chemical dosimeters based on optical absorption for measuring biologically relevant low doses because of their higher sensitivity. The effects of very intense dose rate (TGy/s) from pulses of fast electrons generated by a picosecond linear accelerator on the chemical yields of fluorescence chemical dosimeters were investigated at low peak doses (

We investigate the oxidation of silver cyanide

Gold nanoparticles are known to cause a radiosensitizing effect, which is a promising way to improve radiation therapy. However, the radiosensitization mechanism is not yet fully understood. It is currently assumed that gold nanoparticles can influence various physical, chemical, and biological processes. Pulse radiolysis is a powerful tool that can examine one of the proposed effects of gold nanoparticles, such as increased free radical production. In this work, we shed light on the consequence of ionizing radiation interaction with gold nanoparticles by direct measurements of solvated electrons using the pulse radiolysis technique. We found that at a therapeutically relevant gold concentration (&lt, 3 mM atomic gold, &lt, 600 &mu, g &times, cm&minus, 3), the presence of gold nanoparticles in solution does not induce higher primary radicals&rsquo, formation. This result indicates that energy absorption by gold nanoparticles and related effects such as higher ionization of surrounding media and &bull, OH radicals overproduction are not the reason for the radiosensitizing effect reported in the literature.

This book gives a progress report on the many and original contributions of radiation chemistry to the fundamental knowledge of the vast domain of chemical reactions and its applications. Radiation chemistry techniques indeed make it possible to elucidate detailed physicochemical mechanisms in inorganic and organic chemistry (including in space) and in biochemistry. Moreover, this comprehension is applied in materials science to precisely control syntheses by radiation, such as radiopolymerisation, radiografting, speci?c treatment of surfaces (textiles, paintings, inks, etc.), synthesis of complex nanomaterials, degradation of environmental pollutants and radioresistance of materials for nuclear reactors. In life sciences, the study of the effects of radiation on biomacromolecules (DNA, proteins, lipids) not only permits the comprehension of normal or pathological biological mechanisms, but also the improvement of our health. In particular, many advances in cancer radiotherapy, in the radioprotection of nuclear workers and the general population, as well as in the treatment of diseases and the radiosterilization of drugs, could be obtained thanks to this research. Abundantly illustrated and written in English by top international specialists who have taken care to render the subjects accessible, this work will greatly interest those curious about a scienti?c ?eld that is new to them and students attracted by the original and multidisciplinary aspects of the ?eld. At a time when radiation chemistry research is experiencing spectacular development in numerous countries, this book will attract many newcomers to the field.

Invited for the cover of this issue are the groups of Roman Dembinski, Mehran Mostafavi, and Amitava Adhikary at the Polish Academy of Sciences, Université Paris-Saclay, and Oakland University. The image depicts a doughnut as a way of illustrating the hole transfer process. Read the full text of the article at 10.1002/chem.202000247.

Damage to DNA via dissociative electron attachment has been well-studied in both the gas and condensed phases; however, understanding this process in bulk solution at a fundamental level is still a challenge. Here, we use a picosecond pulse of a high energy electron beam to generate electrons in liquid diethylene glycol and observe the electron attachment dynamics to ribothymidine at different stages of electron relaxation. Our transient spectroscopic results reveal that the quasi-free electron with energy near the conduction band effectively attaches to ribothymidine leading to a new absorbing species that is characterized in the UV-visible region. This species exhibits a nearly concentration-independent decay with a time constant of ~350 ps. From time-resolved studies under different conditions, combined with data analysis and theoretical calculations, we assign this intermediate to an excited anion radical that undergoes N1-C1′ glycosidic bond dissociation rather than relaxation to its ground state., Radiation-induced low-energy electrons in solution are implicated in DNA damage, but their relaxation dynamics are not well understood. Here the authors observe how quasi-free electrons dissociate glycosidic bonds via an excited nucleoside anion radical, whereas solvated electrons reside on the nucleoside as a relatively stable anion radical.

The ultradivided matter is used for long in various applications, for example in colloids, inks and paints, cosmetics, stained glasses, catalysts, photographic emulsions, ... But the progressive need of nanoparticles for various miniaturized devices and the different approaches for the synthesis have suddenly increased. All of the bottom-up synthesis methods from a diluted precursor to metal nanoparticles imply several steps: a reduction reaction of ionic precursors by electron transfer, inducing the nucleation of atoms then the growth of the seeds into particles, more or less inhibited by stabilizers. The final size, shape, structure and dispersity of the particles strongly depend on the thermodynamics and the kinetics of these steps. The interaction of high energy radiation with the solvent provides, quantitatively and homogeneously distributed in the bulk, strong electron donors (solvated electrons, reducing radicals) which reduce metal ions as precursors into atoms. The radiation chemistry, on one hand in the steady state regime with an accurate knowledge of the yields of all the radiolytic products, and on the other hand in the pulse regime giving access to time-resolved data, constitutes a unique tool to elucidate the detailed mechanisms and to provide the keys of really controlling these processes in view of various applications.

International audience; NMR measurements show that diethyl carbonate (DEC, a solvent with a low dielectric constant) solutions of LiClO4 contain (LiClO4)n oligomers. The reduction of these species by solvated electrons and pre-solvated electrons is followed by picosecond pulse radiolysis measurements. The data analysis shows that several anions absorbing in the NIR and visible range are formed after the 7 ps electron pulse. In contrast with THF solutions of LiClO4, the anionic monomer (LiClO4)- is not observed in DEC solutions. This is due to the fact that DEC is a non-polar solvent favoring the clustering of the monomers in the non-irradiated solution as shown by NMR results, and also due to the instability of the anionic monomer. The absorption spectra of the anionic dimer (LiClO4)2-, trimer (LiClO4)3- and tetramer (LiClO4)4- are clearly observed in NIR and in visible ranges. Compared to the results obtained for the same system in THF, and in agreement with simulated absorption spectra, the experimental results show that the absorption bands are shifted to the blue when n increases. The kinetics recorded for the molar LiClO4 solution indicate that the solute is only under the form of oligomers (LiClO4)n with a large n value and that the reduced species absorb weakly in the visible. Lastly, and contrarily to what is known for well separated ions in polar solvents, it is shown that the (LiClO4)n- anions are not stable with respect to self-reduction, leading to the decomposition of perchlorate anions. In this reaction the perchlorate anion ClO4- is reduced by the Li atom into a chlorate anion ClO3-. This is proved by the presence of ClO3- and of chlorinated species detected by mass spectrometry measurements in irradiated DEC solutions containing LiClO4.

La chimie sous rayonnement, developpee sous la direction de Michel Magat a Orsay, apres d’excellents resultats sur les proprietes des nanoparticules metalliques obtenus vers la fin du siecle passe, recoit une nouvelle impulsion grâce au projet de construction de la plateforme de recherche ELYSE, qui est basee sur le seul accelerateur d’electrons dedie a la radiolyse d’impulsion picoseconde en Europe. Cette plateforme a acquis une visibilite internationale en ouvrant de nouvelles thematiques jadis inaccessibles et en attirant de nombreux chercheurs etrangers.

The directionality of the hole-transfer processes between DNA backbone and base was investigated by using phosphorodithioate [P(S- )=S] components. ESR spectroscopy in homogeneous frozen aqueous solutions and pulse radiolysis in aqueous solution at ambient temperature confirmed initial formation of G.+ -P(S- )=S. The ionization potential of G-P(S- )=S was calculated to be slightly lower than that of guanine in 5'-dGMP. Subsequent thermally activated hole transfer from G.+ to P(S- )=S led to dithiyl radical (P-2S. ) formation on the μs timescale. In parallel, ESR spectroscopy, pulse radiolysis, and density functional theory (DFT) calculations confirmed P-2S. formation in an abasic phosphorodithioate model compound. ESR investigations at low temperatures and higher G-P(S- )=S concentrations showed a bimolecular conversion of P-2S. to the σ2 -σ*1 -bonded dimer anion radical [-P-2S - . 2S-P-]- [ΔG (150 K, DFT)=-7.2 kcal mol-1 ]. However, [-P-2S - . 2S-P-]- formation was not observed by pulse radiolysis [ΔG° (298 K, DFT)=-1.4 kcal mol-1 ]. Neither P-2S. nor [-P-2S - . 2S-P-]- oxidized guanine base; only base-to-backbone hole transfer occurs in phosphorodithioate.

This paper discusses the quality and performance of currently available PbWO$_4$ crystals of relevance to high-resolution electromagnetic calorimetry, e.g. detectors for the Neutral Particle Spectrometer at Jefferson Lab or those planned for the Electron-Ion Collider. Since the construction of the Compact Muon Solenoid (CMS) at the Large Hadron Collider (LHC) and early PANDA (The antiProton ANnihilations at DArmstadt) electromagnetic calorimeter (ECAL) the worldwide availability of high quality PbWO$_4$ production has changed dramatically. We report on our studies of crystal samples from SICCAS/China and CRYTUR/Czech Republic that were produced between 2014 and 2019., Comment: 20 pages, 30 figures

International audience; Concentrated nitric acid solutions subjected to radiation produce radicals of extreme importance in the reprocessing of spent nuclear fuel. Knowledge of the different rate constants of the reactions involved in this chemistry is needed to improve the efficiency of the process and to define safe operating practices. Pulse radiolysis measurements are performed to find the rate constant of the reaction between NO3˙ radicals and U(IV) in highly concentrated nitrate solution. The optimal stabilization conditions toward thermal oxidation are defined for the considered solutions at room temperature and at 45 °C by adding anti-nitrous agents such as hydrazinium nitrate (HN) and hydroxyl ammonium nitrate (HAN). The decay of the NO3˙ radical is monitored and its reaction rates with HN, HAN and U(IV) are found to be 1.3 × 105, 1.5 × 107 and 1.6 × 106 M−1 s−1 at room temperature. The latter value is more than 10 times lower than the one currently used in numerical codes for simulation of the long-term radiolytic degradation associated with the reprocessing and storage of spent nuclear waste. At 45 °C, conditions similar to the reprocessing of spent fuel, the values of the rate constants of NO3˙ radical toward HN, HAN and U(IV) increase and are found to be 2.6 × 105, 2.9 × 107 and 9.3 × 106 M−1 s−1.

International audience; The step-by-step mechanism of the citrate oxidation, of the silver ion reduction into atoms, and of the nucleation of nanoparticles by the Turkevich method are deduced from the gamma-and pulse radiolysis yields of dicarboxy acetone (DCA), H$_2$ and CO$_2$ and of silver ion reduction. Our results demonstrate that the stronger reductant is not citrate (Cit) but the oxidized radical Cit(-H)$^ \bullet$. The formation yields of DCA and CO$_2$ confirm the decarboxylation process during the Cit(-H)$^ \bullet$ oxidation. In pulse radiolysis of solutions of sodium citrate and silver perchlorate, the transient spectra and the kinetics are observed from 20 ps to 800 ms. In particular, the successive H abstraction from citrate by OH$^ \bullet$ radicals, then the one-electron transfer from the citrate radicals Cit(-H)$^ \bullet$ to silver ions initiating the simultaneous nucleation and growth of the reduced silver oligomers are observed. The knowledge of the nuclearity-dependent kinetics and thermodynamics of silver atoms, oligomers and nanoparticles in solution is used to bracket the standard reduction potentials of the first ($\geq$0.4 VNHE) and the second one-electron transfers from citrate ($\geq$1.2 VNHE). During the Turkevich synthesis, the Cit(-H)$^ \bullet$ radical was shown to be released in the bulk solution from the citrate oxidation by Ag$^+$ adsorbed on the walls (Figure 1), or directly by the trivalent Au$^{III}$ ions present in the bulk, respectively. Then the strong Cit(-H)$^ \bullet$ reductant alone is able, as in radiolysis, to overcome the thermodynamic barrier of the very negative potential for the reduction of the free monovalent ions into atoms that is required to initiate the nucleation and growth (Figure1). The reduction potentials values of citrate and Cit(-H)$^ \bullet$ also explain part of the antioxidant properties of citrate.

The detailed mechanism of the reaction between SCN

Oxidation by the ultra-short lived radical cation of water, H2O˙+, can potentially take place at the interface of water and numerous heterogeneous systems involved in radiation therapy, energy and environmental industries. The oxidation processes induced by H2O˙+ can be mimicked in highly concentrated solutions where the nearest neighbors of H2O˙+ may be molecules other than water. The reactivity of H2O˙+ and D2O˙+ is probed in hydrogenated and deuterated sulfuric acid solutions of various concentrations. The oxidized solute, sulfate radical, is observed at 7 ps and remarkably higher yields are found in deuterated solutions. The isotopic effects reveal the competition between two ultrafast reactions: proton transfer toward H2O (D2O) and electron transfer from HSO4− to H2O˙+ (D2O˙+). Density functional theory simulations decipher the electron transfer mechanism: it proceeds via sub-femtosecond charge migration and is not affected by isotopic substitution. This work definitively demonstrates why direct oxidation triggered by H2O˙+ can be competitive with proton transfer.