Electrophoretic preconcentration on plasmonic nanopillar arrays for highly intense surface-enhanced Raman scattering

Highly intense surface-enhanced Raman scattering (SERS) is featured as label-free non-destructive detection of biochemical molecules at extremely low concentration. Localized surface plasmon resonance (LSPR) enhances SERS signals by amplifying both the excitation and scattering process. However, aligning molecules near the hotspots of SERS substrate is still challenging to reach stable preconcentration and confinement of free electrons without inhibition of LSPR. This work presents electrophoretic preconcentration on plasmonic nanopillar arrays for highly intense surface-enhanced Raman scattering. The device includes silver nanoislands coated glass nanopillar arrays (GNA) on a transparent electrode and a cavity between top and bottom electrodes. The results show the enhancement of SERS signals over two orders of magnitudes. This enhancement enables SERS measurement of low Raman active biochemical molecules like neurotransmitters. Moreover, selective SERS measurement between oppositely charged molecules was demonstrated. The combination of strong LSPR metal nanostructure and electrophoretic preconcentration suggests not only enhancement of SERS signals even for low Raman active molecules but also active control of molecules for selective SERS detection of oppositely charged molecules.