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

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 equivalent to Si-O-Si equivalent to (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 degrees 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 degrees 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 similar to 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.