Biomimetic Diatom Surface-Enhanced Raman Scattering Microcavity Array with Multiscale Structure Synergy Enhancement.

Diatoms are a type of organism with a natural three-dimensional porous sieve chamber structure. Their sieve plates exhibit multi-level porous features and can control the distribution of light fields through micronano structures, generating resonance coupling and local field enhancement effects. Although surface-enhanced Raman scattering (SERS) substrates have achieved ultra-high sensitivity detection, they often encounter problems such as poor signal uniformity and uncontrollable molecular distribution. Inspired by the above-mentioned structural characteristics of diatoms, this paper mimics their three-dimensional porous sieve chamber structure to construct a biomimetic three-dimensional microcavity array SERS substrate. By combining the vertical microcavity structure and array design at the micronano scale, multi-scale collaborative enhancement is achieved. This substrate features a large-area high-order array structure, regular three-dimensional microcavities, and the scalability of functional modification. Through systematic regulation of the microcavity height, both experimental and simulation results reveal a significant cavity height-controlled SERS enhancement behavior, which is attributed to the effective coupling between the microcavity optical resonance and local surface plasmon hotspots. Additionally, the designed microcavity structure induces active enrichment of molecules during the drying of droplets, effectively suppressing the coffee ring effect. The minimum detectable concentration of rhodamine can reach 10-12 M, with good uniformity and repeatability. This biomimetic three-dimensional SERS substrate achieves a unified high sensitivity and uniformity through the collaborative effects at the nano, micro, and macro scales, providing a universal strategy for the structural design of high-performance SERS substrates.