Silver Nanoparticles as Low-Emissivity Coating Materials

Abstract

The application potential of silver (Ag) nanoparticles as low-emissivity (low-e) coating materials has been discussed. Ag nanoparticles with an average diameter of about 50 nm were prepared via a wet-chemical method and applied on the surface of glass by spin coating. The as-prepared Ag nanoparticle films showed a typical surface emissivity of about 0.793, compared to about 0.837 of the plain glass substrate. After a mild heat treatment at 200 °C, the annealed Ag nanoparticle films showed a substantially reduced surface emissivity value as low as 0.015. The corresponding structural evolution of Ag nanoparticle films during the heat treatment and its effect on the surface emissivity were discussed by means of scanning electron microscopy. The results indicated that forming an interconnected, porous network of Ag nanoparticles is essential for achieving the low-e effect for this material. By applying such low-e coatings, the heat loss through a double-glazed window can be reduced by about 35% (U-value reduction from 2.75 to 1.78 W (m2K)−1). This work may inspire further efforts to address the energy efficiency issues in the building sector by taking the advantage of nanomaterials and nanotechnology.