Surface enhanced Raman spectroscopy and fluorescence based on black silver

We demonstrate surface plasmon-induced enhancements in optical imaging and spectroscopy on silver coated silicon nanocones which we call black silver substrate. The black silver substrate with dense and homogeneous nanocone forest structure is fabricated on wafer level with a mass producible nanomanufacturing method. The black silver substrate is able to efficiently trap and convert incident photons into localized plasmons in a broad wavelength range, which permits the enhancement in optical absorption from UV to NIR range by 12 times, the visible fluorescence enhancement of ∼30 times and the NIR Raman scattering enhancement factor up to ∼10⁸. We show a considerable potential of the black silver substrate in high sensitivity and broadband optical sensing and imaging of chemical and biological molecules.