Regulating Anderson Localization in Flexible Order‐in‐Disorder Metasurfaces for Robust SERS

ABSTRACT Surface‐enhanced Raman spectroscopy (SERS) has achieved extensive applications through carefully engineered plasmonic metasurfaces. Disordered plasmonic metasurfaces are widely used for SERS applications due to their simple fabrication and low cost. However, their poor spatial uniformity usually causes severe signal fluctuations, degrading the repeatability and robustness of SERS measurements. We propose an order‐in‐disorder metasurface to address this challenge. The design relies on regulating the degree of disorder by introducing a controlled level of ordered features, facilitating the orderly manipulation of photonic Anderson localization. As a representative proof‐of‐concept example, we fabricate a flexible plasmonic nanoflower‐like metasurface by a cost‐effective process and each nanoflower contains randomly distributed nanosheets. Compared with the traditional disordered metasurface, it shows competitive SERS signal intensities while dramatically reducing the relative standard deviation (RSD). In detecting trace pesticide residues on fruit surfaces, this metasurface exhibits a low RSD. The enhanced robustness stems from the strong electromagnetic coupling between short‐range disordered states of Anderson localization and long‐range ordered plasmonic polaritons. The disordered states provide great near‐field enhancement, while the ordered mode manipulates hotspot uniformity. This scheme supports the development of a low‐cost, high‐repeatability, versatile SERS metasurface, and will inspire more practical agriculture and supply chain applications.