Surface-enhanced Raman scattering (SERS) has received considerable attention as a noninvasive
optical sensing technique with ultrahigh sensitivity. While numerous types of metallic particles
have been actively investigated as SERS substrates, the development of new SERS agents with
high sensitivity and their reliable characterization are still required. Here we report the
preparation and characterization of flower-shaped silver (Ag) nanoparticles that exhibit highsensitivity single-particle SERS performance. Ag nanoflowers (NFs) with bud sizes in the range
220–620 nm were synthesized by the wet synthesis method. The densely packed nanoscale
petals with thicknesses in the range 9–22 nm exhibit a large number of hot spots that
significantly enhance their plasmonic activity. A single Ag NF particle (530–620 nm) can detect
as little as 10−11 M 4-mercaptobenzoic acid, and thus provides a sensitivity three orders of SERS
magnitude greater than that of a spherical Ag nanoparticle. The analytical enhancement factors
for single Ag NF particles were found to be as high as 8.0 × 109
, providing unprecedented high
SERS detectivity at the single particle level. Here we present an unambiguous and systematic
assessment of the SERS performances of the Ag NFs and demonstrate that they provide highly
sensitive sensing platforms by single SERS particle.