Freestanding and Permeable Nanoporous Gold Membranes for Surface-Enhanced Raman Scattering

Roman M Wyss; Markus Parzefall; Karl-Philipp Schlichting; Cynthia M Gruber; Sebastian Busschaert; Carin Rae Lightner; Emanuel Lörtscher; Lukas Novotny; Sebastian Heeg

doi:10.1021/acsami.2c02608

Freestanding and Permeable Nanoporous Gold Membranes for Surface-Enhanced Raman Scattering

ACS Appl Mater Interfaces. 2022 Apr 13;14(14):16558-16567. doi: 10.1021/acsami.2c02608. Epub 2022 Mar 30.

Authors

Roman M Wyss¹, Markus Parzefall², Karl-Philipp Schlichting³, Cynthia M Gruber², Sebastian Busschaert², Carin Rae Lightner⁴, Emanuel Lörtscher⁵, Lukas Novotny², Sebastian Heeg^{2

6}

Affiliations

¹ Soft Materials Department of Materials, ETH Zürich, Zürich CH-8093, Switzerland.
² Photonics Laboratory, ETH Zürich, Zürich CH-8093, Switzerland.
³ Laboratory of Thermodynamics in Emerging Technologies Department of Mechanical and Process Engineering, ETH Zürich, Zürich CH-8092, Switzerland.
⁴ Optical Materials Engineering Laboratory, Department of Mechanical and Process Engineering, ETH Zürich, Zürich CH-8092, Switzerland.
⁵ IBM Research, Zurich, Rüschlikon CH-8803, Switzerland.
⁶ Department of Physics, Humboldt Universität zu Berlin, 12489Berlin, Germany.

PMID: 35353489
DOI: 10.1021/acsami.2c02608

Abstract

Surface-enhanced Raman spectroscopy (SERS) demands reliable, high-enhancement substrates in order to be used in different fields of application. Here we introduce freestanding porous gold membranes (PAuM) as easy-to-produce, scalable, mechanically stable, and effective SERS substrates. We fabricate large-scale sub-30 nm thick PAuM that form freestanding membranes with varying morphologies depending on the nominal gold thickness. These PAuM are mechanically stable for pressures up to more than 3 bar and exhibit surface-enhanced Raman scattering with local enhancement factors from 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 10⁶ W cm^-2, and may find use as a building block in SERS-based sensing applications.

Keywords: Raman scattering; SERS; graphene; nanoscale mass transport; plasmonic nanopore; porous gold membrane; suspended membrane.