Label-free and direct protein detection on 3D plasmonic nanovoid structures using surface-enhanced Raman scattering

•SERS on 3D structures can detect proteins at low concentrations without labels.•Concentrations as low as 0.05 μg mL−1 could be detected for 6 different proteins.•The SERS signal is background free and independent of the protein charge.

In this paper we use surface-enhanced Raman spectroscopy (SERS) on 3D metallic structures for label-free detection and characterization of proteins of interest at low concentrations. The substrates are prepared via nanopatterning with latex nano/microparticles and Cr and Ag sputtering, yielding stable, tunable, and mechanically flexible plasmonic structures. The nanovoids generate a SERS signal of the proteins of interest that is background free and independent of the protein charge. Concentrations as low as 0.05 μg mL−1 could be detected for 4 different proteins. The proteins also exhibit significantly different SERS spectra on these substrates, which is an important feature for future label-free direct detection schemes.

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