Hybrid Metasurfaces Based on Laser-Structured Substrates and Plasmonic Nanoparticles for the Enhancement of Adenosine Nucleotide Raman Spectra

Plasmonic cavity metasurfaces based on metal laser-induced periodic surface structures (LIPSSs) and non-spherical metal nanoparticles (NPs) were shown to provide the highly sensitive detection and imaging of biomolecules at room temperature without their special labelling. We studied the enhancement of Raman scattering of 5’-deoxyadenosine monophosphate (dAMP) deposited on two types of fabricated cavity metasurfaces: 1) Ag LIPSSs and Ag triangular nanoprisms, 2) crystalline Si LIPSSs and a pre-deposited thin gold film modified during laser treatment. Both types of the metasurfaces contain metal or metal-semiconductor substrates processed with femtosecond laser radiation in a single step. An enhancement of more than 100 times for some Raman peaks of dAMP at Ag nanoprisms/Ag LIPSSs was achieved. In the case of Au NPs/Si LIPSS metasurface a slight increase of Raman spectrum of dAMP was revealed. This effect additionally emphasizes the crucial role of the near-field coupling of the localized surface plasmon modes of Ag nanoprisms and the propagating surface plasmon polaritons of Ag surfaces and consequent formation of collective plasmonic gap modes of the entire plasmonic cavity that determine the appearance of hot spots at such metasurfaces.