Ag colloid-ethanethiol films: spacer-modified substrates for surface-enhanced resonance Raman scattering spectroscopy of chromophoric molecules

interfacial Ag colloid-ethanethiol films were prepared by vigorous shaking of a two-phase system consisting of an aqueous Ag colloid and a solution of ethanethiol in dichloromethane. Surface-enhanced Raman scattering (SERS) s pectra of the glass-deposited films confirm modification of Ag colloidal pa rticles by the chemisorbed thiol, The deposited films were then used as sub strates for adsorption of hydrophobic, water insoluble species: free-base 5 , 10, 15, 20-tetraphenylporphine (H2TPP) and beta-carotene from their dichl oromethane solutions. Good quality surface-enhanced resonance Raman scatter ing (SERRS) spectra of chemically unperturbed H2TPP and beta-carotene obtai ned from the Ag colloid-ethanethiol-adsorbate films indicate that Ag colloi d-ethanethiol films can be employed as spacer-modified substrates for SERRS of water insoluble chromophoric species. However, further testing of the f ilms by adsorption of azodyes methyl yellow and methyl red shows that the s pacer efficiency of ethanethiol may be limited by the size and/or by the ch emical nature of the adsorbate. (C) 1999 Elsevier Science B.V. All rights r eserved.