Bionic 3D periodic nanostructures by Ag nano-islands deposited on cicada wings for rapid SERS detection

Abstract

Recently, flexible and wearable sensors are extensively developed in advanced coating materials, especially in label-free and culture-free rapid detection. Surface-enhanced Raman scattering (SERS) detection is the one of the “fingerprinting” and rapid sensing technology, which combined with noble metal nanoparticle arrays and Raman spectroscopy. The bionic 3D regular structures can induce the multiple reflection of the laser in 3D structures to increase SERS intensity. In this study, we used the natural organism wings (cicada wings, CW) as the substrate. Homogenous nano-columnar structures with the size of 69–72 nm were observed on the CW by scanning electron microscope. Ag nano-island arrays were further deposited on the CW by thermal evaporation. The interparticle spacing of the Ag nano-columnar would decrease with increasing the deposited thickness, which could produce a very strong 3D hot-spots effect for enhancing Raman signals. The results show that the optimal SERS signals were found at 100 nm deposited thickness of Ag nano-islands on the CW nanostructure. The limit of detection (LOD) is lower than 10−9 M and the related standard deviation (RSD%) is about 13.7%, showing the high sensitivity and reproducibility of SERS signal for small molecules detection. Particularly, SERS intensity of CW-Ag-100 nm would increase ~1.7 times while bending inner angle achieves 15o, displaying its flexible characterization.