Facile fabrication of SERS-active substrates based on discarded silver compact disks

► SERS-active substrates based on discarded Ag compact disks (CDs) were fabricated. ► The Ag layer on CDs used as SERS substrate exhibited a good SERS activity. ► The Ag CDs roughened by electrochemical method improved its SERS activity greatly. ► A sandwich structure was fabricated to further improve the SERS activity.