Plasmonic Nanoarrays as SERS Substrates: Advances, Challenges, and Perspectives.

ConspectusSurface-enhanced Raman scattering (SERS) provides a powerful spectroscopic approach for molecular identification and interfacial analysis by combining chemical specificity with ultrahigh sensitivity. While chemically synthesized nanoparticles have enabled broad use of SERS, increasing attention is being paid to how structural uniformity, aggregation behavior, and surface chemistry influence signal reproducibility, reliability, and mechanistic interpretation. In this context, plasmonic nanoarrays fabricated by template-assisted physical deposition offer a complementary and increasingly important SERS platform.This Account summarizes recent advances in SERS using nanoarrays fabricated by template-assisted evaporation. In these approaches, nanoscale geometry and hotspot distributions are predefined by the template and realized through directional deposition. These template-defined architectures enable reproducible electromagnetic enhancement, polarization-controlled excitation, and stable plasmonic responses. Moreover, physical deposition yields clean, ligand-free metal surfaces, providing a well-defined interface for probing plasmon-molecule interactions and interfacial chemical processes. Using anodic aluminum oxide (AAO) lithography as a representative platform, we illustrate how precise control over template thickness enables angle-resolved deposition and structural programmability, allowing the fabrication of dimers, trimers, and compositionally heterogeneous architectures with nanometer-scale gaps. These capabilities support advanced SERS functionalities, including efficient hotspot activation for enhanced sensitivity, selective molecular trapping, and access to interfacial processes on nonplasmonic or weakly plasmonic materials. Furthermore, integration with transparent substrates and soft supports enables liquid-phase SERS configurations and flexible sensing platforms. These liquid-phase SERS configurations improve signal stability and measurement reliability for real-time, in situ measurements, while mitigating aggregation-related issues commonly encountered in conventional SERS. Beyond molecular detection, nanoarray-based SERS provides a controlled experimental framework for mechanistic studies in plasmonic chemistry. The combination of chemically clean surfaces with nonaggregating and structurally stable architectures enables plasmon-driven interfacial processes to be examined under well-defined and reproducible conditions, and facilitates in situ, real-time tracking of reaction dynamics in liquid-phase SERS measurements. This well-controlled environment serves as a reliable physical model for investigating interfacial reaction mechanisms, allowing direct identification of key reaction intermediates and offering an effective route to resolving long-standing mechanistic debates in plasmonic chemistry.Overall, this Account underscores the value of template-fabricated plasmonic nanoarrays as a versatile SERS platform that connects sensitive detection with mechanistic insight. Looking ahead, continued advances in template engineering and deposition strategies are expected to further expand their role in well-controlled studies of light-matter interactions and interfacial physics and chemistry.