Embedding Raman reporters
within nanosized gaps of metallic
nanoparticles
is an attractive route for surface-enhanced Raman spectroscopy (SERS)
applications, although often this involves complex synthesis procedures
that limit their practical use. Herein, we present the tip-selective
direct growth of silver satellites surrounding gold nanostars (AuNSt@AgSAT),
mediated by a dithiol Raman reporter 1,4-benzenedithiol (BDT). We
propose that BDT is embedded within nanogaps which form between the
AuNSt tips and the satellites, and plays a key role in mediating the
satellite growth. Not only proposing a rationale for the mechanistic
growth of the AuNSt@AgSAT, we also demonstrate an example for its
use for the detection of Hg2+ions in water. The presence
of Hg2+resulted in amalgamation of the AuNSt@AgSAT, which
altered both its structural morphology and Raman enhancement properties.
This provides a basis for the detection where the Raman intensity
of BDT is inversely proportional to the Hg2+concentrations.
As a result, Hg2+could be detected at concentrations as
low as 0.1 ppb. This paper not only provides important mechanistic
insight into the tip-selective direct growth of the anisotropic nanostructure
but also proposes its excellent Raman enhancement capability for bioimaging
as well as biological and chemical sensing applications.