Quasi Optical Cavity of Hierarchical ZnO Nanosheets@Ag Nanoravines with Synergy of Near- and Far-Field Effects for In Situ Raman Detection.

The vertically interlaced hierarchical structure (HS) of ZnO nanosheets (NSs)@Ag nanoravines (NRs) as a quasi optical cavity (QOC) for Raman enhancement has been studied experimentally and theoretically in this work. A novel synergism of near and far-field effects of Ag NRs is facilitated by the multiple oscillation of light inside the ZnO QOC, providing wide distributions of "hot spots" in a large space. The "spatial hot spots" in the HS bring reliable signal collection in in situ Raman detection. Without any specific materials and methods adopted, this HS provides researchers a new way to adjust the light in the fields of Raman enhancement.