Fabrication of porous Au nanowires on a mirror featuring ultrahigh-density nanogaps via plasma-assisted nanotransfer printing for enhanced SERS

Although porous metal nanostructures with densely distributed nanogaps offer exceptional potential to significantly enhance surface-enhanced Raman scattering (SERS) signals, fabrication of ultrahigh-density nanogaps that increase the density and intensity of hotspots remains a critical challenge. In this study, we fabricate hierarchically engineered porous Au nanostructures (P-Au NSs) with ultradense hotspots on various substrates using a nanotransfer printing (nTP) system. Ultradense P-Au nanowires exhibit superior plasmonic coupling at stacked cross-points, which can be attributed to their increased contact areas arising from porous architecture. In addition, experimental results and numerical simulations confirm the plasma-treated P-Au nanowire on a mirror (pPAN on M) structure produced via an advanced nTP process further enhancing hotspot formation. The SERS performance was evaluated using 4-mercaptobenzoic acid (4-MBA) and thiram with an optimized substrate achieving a Raman enhancement factor of 1.21 × 10 12 and limit of detection for 4-MBA of ∼6.46 × 10 −13 M. These findings underscore the significant potential of the developed P-Au NSs not only for ultrasensitive SERS detection but also for diverse applications in energy storage, catalysis, and optoelectronics.