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

TL;DR

This study investigates how irradiation induces silver nanocluster formation in silicate glasses, revealing mechanisms similar to photographic latent image formation, influenced by defect interactions, redox chemistry, and energy deposition.

Contribution

It demonstrates the role of irradiation type and energy density in controlling Ag nanocluster nucleation, linking defect chemistry and redox interactions to clustering mechanisms.

Findings

Ion irradiation is more effective than gamma irradiation in inducing nanoclusters.

Cluster density depends on energy deposition and redox properties of the glass.

Mechanisms resemble latent image formation in photography.

Abstract

The synthesis of Ag nanoclusters in sodalime silicate glasses and silica was studied by optical absorption (OA) and electron spin resonance (ESR) 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 Ag+ to Ag0) as compared to gamma photon irradiation.