Jean-Louis Marignier

Radiation-induced synthesis of mono- and multi-metallic clusters and nanocolloids

This review is devoted to metal cluster synthesis in solution via radiolytic reduction of ionic precursors under the proper conditions. The size and structure of the final particles are described in relation to the nucleation and growth mechanism of the process with a special interest in oligomers and nanometric-sized particles. The influence of either a polymeric surfactant or a ligand or a support is described. The role of a chemical electron donor in the development of cluster size is explained. Particular attention is paid to the formation of bimetallic clusters and to the synthesis conditions required to obtain either a core-shell or an alloyed structure in relation to a possible intermetal electron transfer.

Absolute calibration for a broad range single shot electron spectrometer

This article gives a detailed description of a single shot electron spectrometer which was used to characterize electron beams produced by laser-plasma interaction. Contrary to conventional electron sources, electron beams from laser-plasma accelerators can produce a broad range of energies. Therefore, diagnosing these electron spectra requires specific attention and experimental development. Here, we provide an absolute calibration of the Lanex Kodak Fine screen on a laser-triggered radio frequency picosecond electron accelerator. The efficiency of scintillating screens irradiated by electron beams has never been investigated so far. This absolute calibration is then compared to charge measurements from an integrating current transformer for quasimonoenergetic electron spectra from laser-plasma interaction.

Irradiation-induced Ag nanocluster nucleation in silicate glasses: Analogy with photography

The synthesis of Ag nanoclusters in soda lime silicate glasses and silica was studied by optical absorption and electron spin resonance experiments under both low (gamma ray) and high (MeV ion) deposited energy density irradiation conditions. Both types of irradiation create electrons and holes whose density and thermal evolution---notably via their interaction with defects---are shown to determine the clustering and growth rates of Ag nanocrystals. We thus establish the influence of redox interactions of defects and silver (poly)ions. The mechanisms are similar to the latent image formation in photography: Irradiation-induced photoelectrons are trapped within the glass matrix, notably on dissolved noble metal ions and defects, which are thus neutralized (reverse oxidation reactions are also shown to exist). Annealing promotes metal atom diffusion, which, in turn, leads to cluster nuclei formation. The cluster density depends not only on the irradiation fluence but also---and primarily---on the density of deposited energy and the redox properties of the glass. Ion irradiation (i.e., large deposited energy density) is far more effective in cluster formation, despite its lower neutralization efficiency (from

Nucleation dynamics of silver aggregates simulation of photographic development processes

{\mathrm{Ag}}^{+}

Size-dependent thermodynamic properties of silver aggregates. Simulation of the photographic development process

to

Ionizing radiation-liquid interactions: A comparative study of polar liquids

{\mathrm{Ag}}^{0}

Picosecond pulse radiolysis of the liquid diethyl carbonate.

) as compared to gamma photon irradiation.

Electron-induced growth mechanism of conducting polymers: a coupled experimental and computational investigation.

Pulse radiolysis was used to observe the earliest steps of coalescence of silver atoms, according to the aggregation number n, in the presence of an electron donor produced by the same pulse, the radical anion SPV-· of the sulfonato-propylviologen, whose electrochemical potential is E0[SPV/SPV-] = -0.41 V/NHE. The growth of silver aggregates and the decay of SPV- were both followed by time-resolved optical spectroscopy. The absorbance of SPV- is first constant for a certain time-delay. Then an SPV- decay correlated with the growth of Agn absorbance is observed. Both variations depend on the relative abundance of the reduced species Ag01 and SPV-. The important feature of the time-delay suggests that a critical size has to be reached by the aggreagate before it is thermodynamically able to accept electrons from SPV-, then to grow by alternate adsorption of Ag+ ions and electron scavenging. The successive pseudo-first order components of the SPV- decay are interpreted as electron transfer processes from SPV- towards the silver particles which play the role of initiating, autocatalytic growth centers. Electron micrographs of the final aggregates indicate substantial size changes when the reduction is mostly achieved by the donor SPV- acting as a developer. A simulation model was derived including coalescence reactions between atoms and aggregates, and autocatalytic electron transfer processes beyond a critical aggregation number nc. It is concluded that nc = 4 when SPV- is the donor, and hence that the electrochemical potential of the critical silver aggregate is E0[Ag+5/Ag5] ≈ -0.41 V. On the basis of these data, and others taken from the literature, the size-dependence of the electrochemical potential is discussed and compared with that of the ionization potential in the gas phase. A tentative extrapolation of the present interpretation to the mechanism of photographic development processes is also proposed.

Oxidation of Bromide Ions by Hydroxyl Radicals: Spectral Characterization of the Intermediate BrOH•–

Pulse radiolysis and time-resolved optical spectroscopy were used to observe the earliest steps of silver aggregation in the presence of an electron donor whose electrochemical potential is close to those of usual photographic developers. A critical size has to be reached by the silver aggregate before it is thermodynamically able to accept electrons from the donor, then to grow by an autocatalytic process with alternate adsorption of Ag+ ions and electron scavenging. From a computer simulation the critical aggregation numbernc is found to be 4 and hence the electrochemical potential of the critical aggregate is ≈−0.4 V/NHE. The size-dependence of the electrochemical potential in an aqueous solution is discussed and compared with that of the ionization potential in the gas phase. A tentative extrapolation of the present interpretation to the mechanism of the photographic development is proposed.

Electrolytes Ageing in Lithium‐ion Batteries: A Mechanistic Study from Picosecond to Long Timescales

Abstract A general survey of the behavior under irradiation of liquids with a wide variety of properties is given here. It permits us to check the validity of models or radiation-liquid interaction. A main distinction first appears—the ability of the liquid molecules to attach electrons or to merely solvate them. In the last case, the fate of the common species es- is compared. Specific aspects of the partially diffusion-contrlled reactivity of es- and of a cooperative role for cations in electron-radical reactions are emphasized.