In
recent years, anisotropic nanostructures have emerged as one
of the representative surface-enhanced Raman scattering (SERS) substrates
due to their outstanding characteristics, including unique morphology
and tunable localized surface plasmon resonance (LSPR) properties.
Herein, a spinous WO3 nanourchin (NU) array composited
with anisotropic Au@Ag nanorods (NRs) as a SERS substrate with high
sensitivity and reproducibility was fabricated using a layer-by-layer
assembly method. In particular, the WO3 NU array with a
large specific surface area was selected as a supporting platform
for Au@Ag NR deposition to promote the formation of three-dimensional
(3D) high-density hot spots. Subsequently, we not only demonstrate
that the permeability of the 3D template vastly affects the SERS performance
of the 3D composite substrate but also suggest that management of
the distribution of metal nanoparticles is a novel strategy for enhancing
the activity of the composite substrate. In addition, the SERS performance
of the composite substrate was optimized by adjusting the length of
Au@Ag NRs, and the highest SERS sensitivity was obtained with an enhancement
factor of up to 1.7 × 109. Benefiting from the effective
interfacial self-assembly approach, the as-prepared 3D SERS substrate
exhibits excellent repeatability with a signal intensity deviation
as low as 6.73%. More importantly, the dense hot spots and Raman enhancement
mechanism of the WO3/Au@Ag NR substrate were also verified
by the finite-difference time-domain simulation results of the electromagnetic
field distributions. The WO3/Au@Ag NR composite substrate
was applied to identify malachite green and crystal violet molecules
with a limit of detection as low as 10–10 M. As
a result, this WO3/Au@Ag NR substrate is expected to be
an efficient SERS platform for reliable and sensitive chemical analysis
in environmental monitoring.