Surface-enhanced Raman activity and stability study of silver films prepared by reduction of Ag+ ions in N,N-dimethylformamide.

A new SERS-active silver film prepared by directly depositing silver nanoparticles on glass is reported. The spontaneous reduction of Ag+ ions in N,N-dimethylformamide (DMF) (in the absence of a protecting agent) leads to the deposition of silver nanoparticles on clean glass surfaces in contact with the solution. The observed optical micrographs and AFM images show that the arrangement of the nanoparticles is inhomogeneous and the particles appear to be closely packed. These films are shown to be excellent substrates for SERS measurements, demonstrating significant enhancement, good stability, and trace detection capability. The SERS enhancement of the silver films with different deposition times was compared and found that the 8-h film gives the largest enhancement ability with an enhancement factor estimated at about 10(9). It is also found that the silver films stored for 80 days in air show no significant degradation in their sensitivity.