Grating-like SERS substrate with tunable gaps based on nanorough Ag nanoislands/moth wing scale arrays for quantitative detection of cypermethrin

Considering the complexity and high-consumption of the existing approaches to fabricate three-dimensional (3D) regular substrate templates, the scales of the moth wings with evenly-distributed nanoarrays were discovered to provide an ideal bioscaffold for metal silver (Ag) to decorate on to fabricate a flexible, highly-ordered, low-cost and large-scale Ag nanoislands/moth wing (Ag/MW) SERS-active substrate. The grating-like substrate with the optimal morphology of rough and hierarchical Ag nanoislands exhibited high enhancement factor (EF, ~4.16 × 105), low detection limit (10−10 M) to 4-aminothiophenol (4-ATP), outstanding signal uniformity (the relative standard deviations were less than 15%) and superior identification performance in the quantitative detection of pesticide cypermethrin. The three-dimensional finite-difference time-domain (3D-FDTD) method simulated the spatial distribution of the electric field intensity in the substrates with different morphologies, showing a potential strong enhancement of Raman signals in sub-10 nm gaps between two adjacent Ag nanoislands of different layers. These prominent SERS properties of novel Ag/MW SERS-active substrates suggest their potential value in rapid on-side biological and chemical sensing. Meanwhile, the highly-ordered nanoarrays of moth wings provide a new idea for the preparation of regular biomimetic nanomaterials.