Towards high quality triangular silver nanoprisms: improved synthesis, six-tip based hot spots and ultra-high local surface plasmon resonance sensitivity

Abstract

The great application potential of triangular silver nanoprisms (TSNPRs, also referred to as triangular silver nanoplates) is hampered by the lack of methods to produce well-defined tips with high monodispersity, with easily removable ligands. In this work, a simple one-step plasmon-mediated method was developed to prepare monodisperse high-quality TSNPRs. In this approach, the sole surface capping agent was the easily removable trisodium citrate. Differing from common strategies using complex polymers, OH⁻ ions were used to improve the monodispersity of silver seeds, as well as to control the growth process through inhibiting the oxidation of silver nanoparticles. Using these monodisperse high-quality TSNPRs as building blocks, self-assembled TSNPRs consisting of six-tip based “hot spots” were realized for the first time as demonstrated in a high enhancement (∼10⁷) of surface-enhanced Raman scattering (SERS). From the plasmon band shift versus the refractive index, ultra-high local surface plasmon resonance sensitivity (413 nm RIU⁻¹ or 1.24 eV RIU⁻¹, figure of merit (FOM) = 4.59) was reached at ∼630 nm, making these materials promising for chemical/biological sensing applications.