3D plasmonics SERS sensors.
(A) Measured (solid curves) and simulated (dashed curves) FlexBrite in dry state (blue curves) and wet state (red curves). Both measured and simulated reflection spectra show a dip around 633 nm, the excitation laser wavelength. This indicates the resonance at 633 nm. (B) SERS spectra of FlexBrite with water, biotin and biotin-streptavidin conjugate on the surface of FlexBrite (A and B reproduced from Ref.  with permission from The Royal Society of Chemistry). (C) An array of ZnO-NRs decorated with Ag-NPs (on the NRs side surface) and Ag spheres (on the NRs tops) on Si wafers. There are three kinds of “gaps” between the Ag-NPs to form 3D “hot spots” as indicated as 1st, 2nd, and 3rd schematically. “1st” stands for the gaps between the Ag-NPs located on the side surface of the same NR; “2nd” stands for the gaps between the two Ag-NPs located on the side surface of two neighboring NRs; and “3rd” stands for the gaps between the two large Ag spheres located on the tops of two neighboring NRs. (D) Top: SEM image of the ZnO-NRs after an Ag-sputtering for 135 s; Bottom: SEM image of small Ag-NPs on the side surface of the ZnO-NRs after an Ag-sputtering for 12 min (C and D adapted from Ref.  with permission from John Wiley and Sons).