Freestanding and permeable nanoporous gold membranes for surface-enhanced Raman scattering

Surface-enhanced Raman spectroscopy (SERS) demands reliable, high enhancement substrates in order to be used in dierent elds of application. Here we introduce free- standing porous gold membranes (PAuM) as easy-to-produce, scalable, mechanically stable, and eective SERS substrates. We fabricate large-scale sub-30nm thick PAuM, that form freestanding membranes with varying morphologies depending on the nom- inal gold thickness. These PAuM are mechanically stable for pressures up to > 3 bar, and exhibit surface-enhanced Raman scattering with local enhancement factors of 104 to 105, which we demonstrate by wavelength-dependent and spatially resolved Raman measurements using graphene as a local Raman probe. Numerical simulations reveal that the enhancement arises from individual, nanoscale pores in the membrane acting as optical slot antennas. Our PAuM are mechanically stable, provide robust SERS enhancement for excitation power densities up to 106Wcm􀀀2, and may nd use as a building block in SERS based sensing applications.