Ag-modified silicon nanowires substrate for ultrasensitive surface-enhanced raman spectroscopy

We report a unique substrate for surface-enhanced raman spectroscopy (SERS) based on silver nanoparticles-embedded silicon nanowires (SiNWs). The SiNWs were prepared by thermal evaporation of SiO powder via oxide-assisted growth, oxide removed with HF, and then used to reduce silver ions to form a highly decorated Ag-embedded surface. Such modified SiNWs substrates yielded ultrahigh SERS sensitivity, which could detect 25 mu l of 1x10(-16)M Rhodamine 6G, 1x10(-16)M crystal violet, and 1x10(-14)M nicotine in methanol solutions. An Ag-modified SiNW strand could also enable SERS detection of 25 mu l of 1x10(-8) mg/ml calf thymus DNA. The possible mechanisms for the ultrahigh SERS sensitivity were discussed.