Evaluating the role of coinage metal films in the detection of mercury vapor by surface plasmon resonance spectroscopy

We have studied the adsorption of mercury vapor to gold and silver surfaces by surface plasmon resonance spectroscopy. Three types of metal films were studied including 50 nm Au, 50 nm Ag, and Au-coated silver films (15 nm Au/35 nm Ag). The sensitivity of each substrate for Hg detection was determined by quantitative X-ray photoelectron spectroscopy measurements and objectively compared. An important finding is that there exists an angle for each film where the reflectivity change is directly proportional to Hg coverage. Theoretical surface plasmon resonance curves were calculated and qualitatively predict the observed trends. The Au-coated Ag film offers greater chemical stability than a pure Ag film and slightly higher sensitivity than a pure Au film.