Nanopillar arrays with nanoparticles fabricated by a femtosecond laser pulse train for highly sensitive SERRS

This work presents a novel method for fabricating repeatable, uniform, large-area, highly sensitive, surfaceenhanced resonance Raman scattering (SERRS) substrates combined with silicon nanopillar arrays and silver nanoparticles. The proposed method consists of two steps: (1) induce periodic ripples in deionized water using a linearly polarized femtosecond laser; and (2) generate dense 80-nm-diameter nanopillar arrays with silver nanoparticles in silver nitrate solution with a 90° rotated polarization, femtosecond double-pulse train. As the pulse delay increases from 0 to 1000 fs, the mean size of the silver nanoparticles reduces, and the average number of nanoparticles increases, which, in turn, increases the enhancement factor of SERRS signals up to 1.1 × 10⁹. Furthermore, melamine (down to 125 ppb) was detected by the fabricated SERRS substrates.