Oxidation reactions by radicals constitute a very important class of chemical reactions in solution. Radiation Chemistry methods allow producing, in a controlled way, very reactive oxidizing radicals, such as OH^•, CO₃^•–, NO₃^•, SO₄^•–, and N₃^•. Although the radical cation of water, H₂O^•+, with a very short lifetime (shorter than 1 ps) is the precursor of these radicals in aqueous solutions, its chemistry is usually known to be limited to the reaction of proton transfer by forming OH^• radical. Herein, we stress situations where H₂O^•+ undergoes electron transfer reaction in competition with proton transfer.

Where does the reaction between prehydrated electrons and nucleotides lead to?

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.

The optical limiting effect induced by gold clusters was measured as a function of excitation wavelength. The limiting effect is most efficient below 530 nm, and decreases towards the red. Two different behaviors are seen in the time-resolved signals in the nanosecond and picosecond ranges. These behaviors have different time delays for the amplitude maxima and for the fluence thresholds where nonlinear effects are observed. This suggests that two types of scattering centers are responsible for the optical limitation. The fast mechanism, which reaches a maximum amplitude in less than 1 ns, occurs at relatively high fluence and for short pulses and is assigned to the vaporization of metal particles. It is more pronounced for large clusters where the absorbed light energy is primarily highly confined. The slow mechanism, which develops in a few nanoseconds, is assigned to the energy transfer from the gold particles to the surrounding solvent and to the formation of solvent bubbles. At lower fluence and for smaller size clusters, only the second mechanism is observed in the nanosecond range, because the efficient dissipation of energy from the small clusters to the solvent, which produces bubbles, precludes metal-particle vaporization.

The efficient use of renewable X/γ-rays or accelerated electrons for chemical transformation of CO₂ and water to fuels holds promise for a carbon-neutral economy; however, such processes are challenging to implement and require the assistance of catalysts capable of sensitizing secondary electron scattering and providing active metal sites to bind intermediates. Here we show atomic Cu-Ni dual-metal sites embedded in a metal-organic framework enable efficient and selective CH₃OH production (~98%) over multiple irradiated cycles. The usage of practical electron-beam irradiation (200 keV; 40 kGy min⁻¹) with a cost-effective hydroxyl radical scavenger promotes CH₃OH production rate to 0.27 mmol g⁻¹ min⁻¹. Moreover, time-resolved experiments with calculations reveal the direct generation of CO₂^•‒ radical anions via aqueous electrons attachment occurred on nanosecond timescale, and cascade hydrogenation steps. Our study highlights a radiolytic route to produce CH₃OH with CO₂ feedstock and introduces a desirable atomic structure to improve performance.

Bimetallic Au-Pd and Ag-Pd Clusters Synthesised by γ or Electron Beam Radiolysis and Study of the Reactivity/Structure Relationships in the Selective Hydrogenation of Buta-1,3-Diene — Ag-Pd and Au-Pd (alloyed or core-shell) catalysts were synthesised by radiolytic reduction (gamma rays or electron beam). Selective hydrogenation of buta-1,3-diene was performed with these different nanoparticles deposited on alumina in order to investigate composition and structure effects on catalytic performances. Au-Pd and Ag-Pd nanoparticles exhibit very different catalytic behaviours: whereas only hydrogenation activity is modified on Au-Pd systems without any change in selectivity toward butenes formation, important variations in selectivity into butenes are observed for Ag-Pd nanoparticles deposited on alumina support.