Three‐Dimensional Hierarchical Nanowire‐Networks with Deep‐Focus Tolerance and Adhesion Robustness for Harsh‐Environment SERS Sensing

ABSTRACT With growing demand for field‐deployable and reliable Surface‐Enhanced Raman Scattering (SERS) applications, a critical yet often overlooked challenge is the stringent requirement for precise laser focusing, which severely limits operation outside controlled laboratory environments. To overcome this focal precision barrier, we present a three‐dimensional (3D) hierarchical Au nanowire‐network (NWNW) engineered as a robust SERS substrate. Its architecture is constructed to provide exceptional deep focus tolerance, exhibiting pronounced 3D optical activity along the z‐direction and angular anisotropy under polarized illumination. This enables the substrate to achieve an ultralow detection limit of 1×10 −12 M for non‐resonant 4‐mercaptopyridine molecules, while maintaining outstanding signal uniformity and repeatability (relative standard deviation, RSD <10%). Moreover, an effective medium model reveals that the synergistic interplay between increased light scattering rates, elevated local density of optical states, and broadened eigenmodes jointly contributes to efficient light harvesting and near‐field enhancement throughout the 3D architecture. Equally importantly, the NWNW's mechanical reinforcement ensures adhesion robustness and consistent SERS performance even when subjected to harsh environments. By solving the focal precision challenge while maintaining robustness, this work demonstrates that the 3D Au NWNW is not only a highly sensitive SERS substrate but also a viable platform for transitioning SERS from controlled laboratory environments toward demanding real‐world applications.