Surface plasmon resonance evaluation of colloidal silver aerogel filters

Aerogels containing silver nanoparticles were fabricated for gas catalysis applications. By applying the concept of an average or effective dielectric constant to the heterogeneous interlayer surrounding each particle, we extend the technique of immersion spectroscopy to heterogeneous or porous media. Specifically, we extend the predominant effective medium theories for the determination of the average fractional composition of each component in this inhomogeneous layer. Hence, the surface area of metal available for catalytic gas reaction is determined. The technique is satisfactory for statistically random metal particle distributions but needs modification for aggregated systems. (C) 1998 Elsevier Science B.V. All rights reserved.