Visual detection of organic monomolecular films by interference colors

This is the authors' abstract. We don't add key points for this paper.

Thin (<10-nm) adsorbed organic films are visible to the unaided eye, if the substrate is first covered with a dielectric film giving a strong interference color, a so-called sensitive color. It is found that a single low-index dielectric film on an absorbing substrate gives optimal sensitivity. A detection limit in the subnanometer range is predicted and confirmed by experiments. Two practical designs using silicon and glass substrates are discussed. These slides can be produced by industrial methods and have proved to give good visualization of monomolecular protein films, e.g., antigen–antibody layers. They have a detection limit of 0.7 nm or 100 ng of protein/cm2 surface.