Abstract

Thin (<10 nm) dielectric layers of biological origin are visible to the unaided eye, on a reflecting substrate, if the substrate is first covered with a dielectric film which gives a strong interference color. Simple and sensitive immunoassays can be based on such reflection phenomena. Slides previously used for this purpose consist of a metal substrate with a dielectric layer on top. Systems used are barium steareate on chromium [1,2], tantalum oxide on tantalum [3], and indium oxide on a gold-indium alloy [4]. A similarly functioning system with a semi-transparent metal layer, on top of a dielectric layer on a metal, has also been described [5]. However, there is no systematic study of the phenomenon. Likewise, there is no system proposed which promises high sensitivity together with simple production and good biochemical properties.

© 1984 Optical Society of America