Gold-coated nanoripples produced by UV-Femtosecond lasers for surface enhanced Raman spectroscopy

[Display omitted] •Demonstrated a simple, easy-to-prepare, and large-active-area UV-fs-laser processing technique for SERS applications on various materials.•Explored the nanoripple evolution on Si by UV-fs lasers and confirmed processing windows for nanoripple formation as functions of hatching distance and laser fluence.•Correlated the SERS enhancement factors and Au-coated UV-fs-laser-induced nanoripple patterns.•SERS enhancement factors up to 2.4 × 107 were achieved for Rhodamine 6G molecules.•Three other materials, stainless steel, glass, and polystyrene, were also investigated for nanoripple formation and SERS measurements. Femtosecond (fs) lasers have been recognized as a powerful tool for micro/nanofabrication, due to their advantages of high flexibility, high repeatability, and minimal introduction of heat. Many studies have been made to employ fs laser processing in fabrication of nanostructures on substrates for surface-enhanced Raman spectroscopy (SERS). However, there have been few reports of ultraviolet (UV)-fs-laser-induced nanoripples for SERS experiments. In this study, we developed simple, easy-to-prepare, and large-active-area SERS substrates using UV-fs laser irradiation. Nanoripples induced in open air by the UV-fs laser on Silicon (Si) substrates with gold coatings were used as SERS-active substrates. Nanoripple evolution by the UV-fs laser was explored to establish the processing windows for nanoripple formation as functions of laser fluence and hatching distances. Moreover, SERS enhancement factors (EFs) were correlated with the laser induced nanoripple patterns. SERS EFs up to 2.4 × 107 were achieved for Rhodamine 6G (R6G) molecules on the laser-textured Si substrates with Au coatings of 34 nm thick. The average period of nanoripples for the highest SERS EF is 253 nm, fabricated by a laser fluence of 0.48 J/cm2 and a hatching distance of 38 µm. R6G concentration down to 10−9 mol/L was detected on the laser-textured Si substrate. Besides Si substrates, three other materials, stainless steel, glass, and polystyrene, were also investigated for nanoripple formation and SERS measurements. Nanoripple structures were formed on stainless-steel surfaces and the highest SERS EF of 1.5 × 107 was achieved. For glass and polystyrene substrates, no nanoripple structures were found. As a result, the SERS EFs (∼106) of glass and polystyrene are one order of magnitude lower than those of the Si and stainless-steel substrates. The SERS demonstration