Coarsening of Ag nanoparticles in SiO2–PEO hybrid film matrix by UV light

Abstract

Ag nanoparticle incorporated inorganic–organic hybrid silica films were prepared from sols derived from tetraethyl orthosilicate–3-(glycidoxypropyl)-trimethoxysilane–silver nitrate following a sol–gel dip-coating method. Hydrolysis–condensation of alkoxy groups and polymerization of epoxy groups formed Si–O–Si (SiO₂) and polyethylene oxide (PEO) networks respectively. A nominal composition of the film of 2.3 equivalent mol% Ag–74.4 mol% SiO₂–23.3 mol% PEO was maintained. The precipitation of Ag nanoparticles was observed when the film was cured at 60–90 °C. UV treatment (5.3–31.8 J cm⁻²) causes coarsening of the Ag nanoparticles inside the hybrid SiO₂–PEO film matrix. A single surface plasmon (SP) band due to Ag nanoparticles has been observed at 419 nm when the film was cured at 90 °C and UV treated with an energy of 5.3 J cm⁻². This SP band is gradually divided into three peaks upon increasing the UV treatment energy up to 31.8 J cm⁻². TEM study confirms the coarsening of small Ag nanoparticles of 3–4 nm in size, leading to the formation of spheroidal, elongated and fractal type small aggregates of Ag nanoparticles of size range ∼19–53 nm. The splitting of the Ag–SP band is found to be consistent with the shape of the Ag nanoparticles as observed by TEM.