Transparent and flexible surface-enhanced
Raman scattering (SERS)
substrates have attracted much interest for the detection of probe
molecules on the curved surfaces of real samples, but a facile route
to fabricate such substrates is still lacking. Herein, we present
a rationally designed, high-performance flexible SERS substrate fabricated
using a simple drop and peel-off technique for the ultrasensitive
detection of pesticides. The proposed SERS substrate consists of a
polymethyl methacrylate (PMMA) film anchored with plasmonic silver
nanoparticles (Ag NPs), which are photoreduced using chemically patterned
ferroelectric templates. The photoreduced Ag NPs extracted onto the
PMMA film offer strong electromagnetic enhancement and produce intensive
hotspots for the effective enhancement of the Raman signal. They provide
superior SERS performance for the detection of parathion (PT) and
fenitrothion (FNT) at trace-level concentrations of 10–9 M and 10–10 M with excellent enhancement factors
in the order of 108 and 109, respectively. Moreover,
the Ag NP/PMMA SERS substrate has good spot-to-spot uniformity and
batch-to-batch reproducibility with the reservation of high detection
sensitivity even after the mechanical deformation of bending and torsion
up to 50 cycles. The multiplex detection ability is also investigated
for the simultaneous detection of PT and FNT. To ensure the practical
feasibility, the in-situ, real-time detection of PT and FNT on the
curved surfaces of tomato and lemon using a fiber-coupled Raman probe
is performed with limits of detection of 4.24 × 10–8 M and 2.74 × 10–9 M. The proposed Ag NP/PMMA
flexible SERS substrate possesses unique features, such as easy fabrication
through a simple, economical, rapid process, and facilitates straightforward
implementation of in-situ SERS detection on curved fruit/vegetable
surfaces.
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