Synthesis and single-particle surface-enhanced Raman scattering study of plasmonic tripod nanoframes with Y-shaped hot-zone.

Herein, plasmonic metal tripod nanoframes with 3-fold symmetry were synthesized in a high yield (ca. 83 %), and their electric field distribution and single-particle surface-enhanced Raman scattering (SERS) were studied. We realized such complex frame morphology by synthesizing analogous tripod nanoframes through multiple transformations, starting from Au nanoprisms. The precise control of the Au growth pattern led to uniform tripod nanoframes embedded with circle or line-shape hotspots. The linear-shaped nanogaps ("Y"-shaped hot-zone) of the frame structures can strongly and efficiently confine the electric field, allowing for strong SERS signals. Coupled with a high synthetic yield of the targeted frame structure, strong and uniform SERS signals were obtained inside the nanoframe gaps. Remarkably, quite reproducible SERS signals were obtained with these structures - the SERS enhancement factors of an average value 7.9 ×10^7 with a distribution of enhancement factors from 2.2 ×10^7 to 2.2 ×10^8 for 45 measured individual particles.