Reactivity of quasi-free electrons toward N3- and its impact on H2 formation mechanism in water radiolysis.

Picosecond pulse radiolysis measurements were employed to assess the effectiveness of N3- in scavenging quasi-free electrons in aqueous solutions. The absorption spectra of hydrated electrons were recorded within a 100 ps timeframe across four distinct solutions with N3- concentrations of 0.5, 1, 2, and 5 M in water. The results revealed a concentration-dependent shift in the maximum absorption spectra of fully solvated electrons. Notably, at 5 M concentration, the maximum absorption occurred at 670 nm, in contrast to 715 nm observed for water. Intriguingly, the formation yield of hydrated electrons within the initial 5 ps electron pulse remained unaffected, showing that, even at a concentration of 5 M, N3- does not effectively scavenge quasi-free electrons. This is in disagreement with conclusions from stochastic models found in the literature. This observation has an important impact on understanding the mechanism of H2 formation in water radiolysis, which we discuss briefly here.

Observation of Nanoconfinement Effect on the Kinetics of Hydrated Electron in the Nanoscale Water Pools of Water-AOT-Cyclohexane Microemulsions by Picosecond Pulse Radiolysis.

The decay kinetics of the hydrated electron (eaq-) in aerosol OT (AOT)-based ternary microemulsions with pool sizes ranging from 0.34 to 4.85 nm were studied using picosecond pulse radiolysis coupled with transient absorption UV-vis spectroscopy. Electron transfer from oil to water and the subsequent solvation occurred within a time resolution of 7 ps. The decay kinetics of eaq- were accurately modeled using a double-exponential decay model, revealing the occurrence of two types of reactions, i.e., the recombination reaction at the water-oil interface and the radical-radical reactions in the water pools. The apparent lifetimes of both types of decays decreased significantly as the size of water pools decreased, indicating the influence of nanoconfinement effects. Moreover, the importance of the water-oil interface increased with decreasing water content, regardless of the presence or absence of NO3- as an electron scavenger in the water pools. Our findings provide a comprehensive understanding on the kinetics of the radiation reaction in AOT-based microemulsions.

Reactivity of presolvated and solvated electrons with CO2 in water up to 118 bar at 298 and 308 K.

The reactivity of electrons in the CO2-water system was evaluated through picosecond electron pulse radiolysis at different gas pressures (ranging from 1 to 118 bar) and temperatures (25 and 35 °C) coupled with UV-vis transient spectroscopy. A custom-made spectroscopic cell was utilized for these experiments, which allowed for regulation of temperature and pressure. The scavenging of electrons was measured directly at gas pressures even in the supercritical state, and the results showed a non-monotonic dependence of electron reactivity with CO2 concentration, in agreement with the changing molar concentration of CO2 in water under varying pressure.