Assisted laser ablation: Silver/gold nanostructures coated with silica

The synthesis processes of metallic nanoparticles have seen a growing interest in recent years, mainly by the potential applications of the phenomenon of localized surface plasmon resonance associated with metallic nanoparticles. This paper shows a fast method to synthesize silver, gold and silver/gold alloy nanoparticles coated with a porous silica shell by the assisted laser ablation method in three steps. The method involves a redox chemical reaction where the reducing agent is supplied in nanometric form by laser ablation. In the first step, a silicon target immersed in water is ablated for several minutes. Later, AgNO₃ and HAuCl₄ aliquots are added to the solution. The redox reaction between the silver and gold ions and products resulting from ablation process can produce silver, gold or silver/gold alloy nanoparticles coated with a porous silica shell. The influence of the laser pulse energy, ablation time, Ag^? and Au^3? concentration, as well as the Ag^? /Au^3? ratio, on optical and structural properties of the nanostructures was investigated. This work represents a step forward in the study of reaction mechanisms that take place during the synthesis of nanoscale materials by the assisted laser ablation technique.