Controlling Morphology and Composition of Bimetallic Ag@Au Nanoplates (NPTs) via AMP‐Mediated Synthesis for Enhanced Plasmonic Performance in Paper‐Based SERS Substrates

ABSTRACT The controlled synthesis of bimetallic nanostructures with preserved morphology and tuneable plasmonic properties remains a challenge in nanomaterials science. Here we take advantage of two complementary Adenosine Monophosphate (AMP)‐mediated functions: i) shape‐controlled Ag nanoplate formation and ii) stabilization of Au(I) species, to synthesize Ag@Au nanoplates (NPTs) with corrugated gold shells formed through kinetically moderated deposition of ex situ generated Au(I)–AMP complexes, minimizing destructive galvanic replacement and silver core dissolution. This enables precise gold layer thickening (up to ∼14 nm) while retaining the anisotropic geometry. Structural characterization confirms progressive shell growth and substantial core retention, supporting a morphology‐preserving growth mechanism. The methodology enables direct growth of NPTs on paper substrates, creating flexible, reliable, and cost‐effective plasmonically active platforms for sensing. The resulting paper‐based Ag@Au NPTs exhibit tuneable surface plasmon resonances and serve as robust substrates for surface‐enhanced Raman spectroscopy (SERS). Functionalization with 4‐mercaptobenzoic acid (4‐MBA) allows ratiometric SERS pH sensing, with reproducible responses in buffer and preliminary evaluation in pH‐adjusted urine samples. The interplay of morphological control, optical tunability, and direct integration on paper substrate underscores the potential of AMP‐mediated synthesis for fabrication of stable, high‐performance bimetallic nanostructures for advanced sensing and plasmonic applications.