Surface-enhanced Raman scattering (SERS) spectroscopy affords a rapid, highly sensitive, and nondestructive approach for label-free and fingerprint diagnosis of a wide range of chemicals. It is of great significance to develop large-area, uniform, and environmentally friendly SERS substrates for in situ identification of analytes on complex topological surfaces. In this work, we demonstrate a biodegradable flexible SERS film via irreversibly and longitudinally stretching metal deposited biocompatible poly(ε-caprolactone) film. This composite film after stretching shows surprising phenomena: three-dimensional and periodic wave-shaped microribbons array embedded with a high density of nanogaps functioning as hot-spots at an average gap size of 20 nm and nanogrooves array along the stretching direction. The stretched polymer surface plasmon resonance film gives rise to more than 10 times signal enhancement in comparison with that of the unstretched composite film. Furthermore, the SERS signals with high uniformity exhibit good temperature stability. The polymer SPR film with excellent flexibility and transparency can be conformally attached onto arbitrary nonplanar surfaces for in situ detection of various chemicals. Our results pave a new way for next-generation flexible SERS detection means, as well as enabling its huge potentials toward green wearable devices for point-of-care diagnostics.

Self‐cleanable surface‐enhanced Raman scattering (SERS) spectroscopy affords a promising route toward environment‐friendly biosensors for point‐of‐care diagnostics. It is of great importance to develop recyclable SERS substrates driven by a photocatalytic decomposition process, especially in the visible range. In this work, inspired by the hedgehog‐like structures, a broadband visible‐light‐driven photocatalytic SERS platform with the CuO nanowires (NWs)/Cu2O hetero‐nanostructures as the backbone is demonstrated. Via employing the approach of nanosecond laser ablation on Cu sheet coupled with subsequent thermal oxidation, the formed hedgehog‐like, high‐density, and dual‐scale micro/nanostructures not only demonstrate enhanced broadband visible‐light‐absorption capability even extended to the near infrared range but also exhibit boosted interfacial adhesion with favorable stability. Such phenomena imply that the binary oxidized Cu composites decorated with metallic nanoparticles can serve as high‐performance SERS substrates with superior recyclability. Under the visible light illumination, the as‐fabricated ternary Ag/CuO NWs/Cu2O composites can be self‐cleaned by photocatalytic degradation of adsorbates, thus leading to recyclable SERS substrates, which can preserve more than 85% SERS activity after seven cycles' measurement. These results pave a new path to realize reusable SERS substrates in the applications of remote and resource‐limited environments toward next‐generation green biosensors.

Surface enhanced Raman spectroscopy (SERS) has drawn much research interest in the past decades as an efficient technique to detect low-concentration molecules. Among many technologies, which can be used to fabricate SERS substrates, laser ablation is a simple and high-speed method to produce large-area SERS substrates. This work investigates the angular texturing effect by dynamic laser ablation and its influence on SERS signals. By tuning the angle between the Si surface and laser irradiation, the distributions and sizes of laser induced hybrid micro/nano-structures are studied. By decorating with a silver film, plenty of hot spots can be created among these structures for SERS. It is found that when the incident laser angle is 15° at the laser fluence of 16.0 J/cm², the SERS performance is well optimized. This work realizes antisymmetric distribution of nanoparticles deposited on Si surface, which provides a flexible tuning of the hybrid micro/nano-structures' fabrication with high controllability for practical applications.