Surface‐enhanced Raman scattering of cytosine and its derivatives in silver sol

Surface‐enhanced Raman scattering of cytosine, cytidine, 2′‐deoxycytidine, and cytidine 5′‐monophosphate (5′‐rCMP) in silver sol was investigated. Cytosine seemed to adsorb on the silver surface as the neutral form. With cytosine and 5′‐rCMP, their orientations with respect to the surface changed from a horizontal to a perpendicular position as the surface concentration increased. Similar reorientation was induced for 5′‐rCMP by an increase in phosphoric acid concentration. Adsorption of the cytosine moiety on the surface seemed to occur through the π system of the ring in the horizontal position and through the lone pair of electrons on the N‐3 atom in the perpendicular position.