Silver-doped sol-gel film as a surface-enhanced Raman scattering substrate for detection of uranyl and neptunyl ions.

A surface-enhanced Raman scattering (SERS) substrate containing silver particles was prepared by an acid-catalyzed sol−gel method. Silver nitrate was first doped into the sol−gel film followed by chemical reduction of the silver ions with sodium borohydride to produce silver particles. This silver-doped sol−gel substrate exhibits strong enhancement of Raman scattering from adsorbed uranyl ions with a detection limit of 8.5 × 10-8 M, which is comparable to existing methods of uranyl detection such as spectrophotometry, fluorometry, and a SERS method based on ligand-modified solution silver colloids. However, in the present method, no preconcentration steps, chromogens, or complexing ligands are needed. Compared with the SERS method using Ag colloidal sols, the silver-doped sol−gel film has the advantage that the silver particles trapped in the sol−gel matrix are much more stable than Ag colloids in liquid media. Furthermore, porous silica sol−gel materials are known to have affinities toward many inorganic...