Fig. 2.

Preparation and characterization of the SERS-active substrate. (A, B) TEM images of the Au NPs with low and high magnification. (C) Dimensional distribution map of the Au NPs. (D) SERS spectra of the SERS nanotags on gold nanosphere and on silicon wafer. (E–H) SEM images of SERS-active substrate assembled by 1–4 layers Au NPs. (I–L) Cross-sectional SEM images of SERS-active substrate assembled by 1–4 layers Au NPs. (For interpretation of the references to color in this figure legend, the reader is referred to the Web version of this article.)