7 Radiation chemistry

Abstract

We try in this review to survey advances in all the aspects of Radiation Chemistry (the effects of high energy or ionizing radiation), both basic and applied, made during the period 1995^1999, after the last report issued at the end of 1994. 1 Classically, two main classes of studies are relevant. The ¢rst one includes the primary phenomena induced by the interaction of high-energy radiation with a chemical system. The way the energy is spatially deposited is indeed highly nonhomogeneous and depends on the type of radiation considered. Mutual reactions between the primary species produced also depend on their initial spatial distribution, and therefore on the energy absorption pattern. The kinetic aspects derive directly from the initial events following radiation absorption and thus, when observed at times as short as possible, give useful information on the early energy distribution for each of the radiation types, X-and g-photons, electrons and heavy particles, and, on the in£uence of their intensity and energy per particle.The second class of studies utilizes the background knowledge of radiation chemistry to generate and then to observe the fate of chemical transient species known to be involved in very important chemical or biochemical processes. Numerous data, such as the nature of reaction products, the absolute rate constants, the sequence of elementary reactions constituting a mechanism, and the thermodynamic and spectroscopic properties of short-lived species have been attained. This kind of study of transients and reaction mechanisms, which can be approached only by pulse techniques (essentially pulse radiolysis or laser photolysis, each with its speci¢c advantages), constitutes the new ¢eld of fast to ultrafast chemistry. It concerns extended domains of physical, organic, inorganic, and bio-chemistry. Moreover, the understanding of mechanisms is quite helpful in suggesting new ways of synthesis or degradation induced by irradiation and is now extensively used in developing various speci¢c processes in applied chemistry. The number of studies on the chemical mechanisms and in applied radiation chemistry constitutes an increased fraction of the total publications in radiation chemistry, which we estimate to be around 4000 over the period considered (almost constant compared to the preceding 5-year

Radiolysis of silver ion solutions in ethylene glycol: solvated electron and radical scavenging yields

“…Although the chemical effects of ionizing radiation on matter have been extensively studied for decades in the steady state and the pulse regimes (Tabata et al, 1991;Belloni et al, 2000;Jonah and Rao, 2001), the complexity of these effects is so great that a detailed mechanism has only been worked out for one systemwater. The yields of primary transient radicals and the formation paths of molecular products have not been completely evaluated for other systems.…”

Influence of Photon and Electrical Energy in the Nucleation of Silver Nanoparticles Synthesis

“…Although the energy input varies, the nucleation step is relatively slow due to chemical transitions to form a metallic cluster in the reacting solvent. The hydroxyl radicals from the radiolysis of water rapidly react with enzyme and silver nitrate to excite the state of aromatic residues [47,48]. A significant advantage of this method is to reduce chemical species in the solution and reaction rate.…”

X-ray-induced reduction of Au ions in an aqueous solution in the presence of support materials andin situtime-resolved XANES measurements

“…However, the process of radiation-induced reduction of metal ions in an aqueous solution in the presence of support materials is not clear. In particular, studies focusing on the behaviour of irradiated metal ions have not been reported, although in the field of radiation chemistry there are many reports that focus on radiation-induced active species such as the hydrated electron, hydrogen radical and hydroxyl radical (Belloni et al, 1998(Belloni et al, , 2000Belloni, 2006). Table 1 shows a list of previously reports on X-ray-induced reduction and in situ measurements.…”