Comparison of three methods to improve adherence of thin gold films to glass substrates and their effect on the SERS response

Vapor-deposited Ag and Au films exhibit high surface-enhanced Raman scatter ing (SERS) sensitivity. With thin metal films, SERS spectra can be obtained by using a "backside" configuration in which the laser light is focused th rough the substrate onto the metal film/liquid (or gas) interface. Use of t he "backside" configuration is particularly advantageous for obtaining SERS spectra of aqueous samples. Because excitation occurs only at the metal/fi lm/liquid interface, both attenuation of the signal by water and fluorescen ce interference are minimized. However, noble metals, such as Ag and Au, do not adhere well to glass substrates, and significant exposure to water dam ages the films. In this paper, three methods of adhering Au to glass and th eir effect on the SERS response are examined. The methods include the use o f a buffer metal between the SERS-active metal film and the glass substrate ; the use of (3-mercaptopropyl)trimethoxysilane (MCTMS); and the use of org anometallic paints. Of the methods examined, the best film adherence and SE RS response was obtained by using MCTMS to bind the metal film to a chemica lly etched glass slide.