Anchored Plasmonic Nanoparticle Structures by In Situ Ultrafast Laser Reduction for Ultrasensitive and Highly Stable SERS

Surface-enhanced Raman spectroscopy (SERS) is widely used in the ultrasensitive detection of chemicals in environmental and biological fields. In this work, anchored plasmonic nanoparticle (NP) structures on various substrates are fabricated by ultrafast laser-induced multiphoton reduction, and the bonding strength between the plasmonic NP and substrate is enhanced by plasmonic effect-enhanced interfacial energy deposition. Anchored Ag NPs with a diameter of 20.68 ± 8.68 nm and a gap of < 5 nm are achieved by precise energy modulation. The prepared substrates show ultralow detection limits (10⁻¹⁴ M for crystalline violet and 10⁻¹² M for thiabendazole) with high stability, which can retain 78.1% and 65.9% of the initial Raman intensity even after 100-day ambient aging and 10⁵ bending cycles. The uniformity of the Raman intensity and substrate reproducibility has relative standard deviations of 4.29% in the 100 × 100 μm² range and 7.95% for 25 substrates. In addition, direct nanofabrication on fresh biological substrates (e.g., apples, plant leaves) with minimal thermal damage can also be allowed. The mechanical stability test shows that the Raman signal after water flow impinging for 120 min is still 56.9% of the initial state. This in situ ultrafast laser synthesis provides a substrate-independent approach to fabricate a robust SERS platform for environmental, biomedical, and food safety applications.