Glass Microfluidic SERS Chip Fabricated by Hybrid Femtosecond Processing with Localized Analyte Aggregation Using Laser Performing Extremely Sensitive SensingTuesday (23.06.2020) 10:30 - 10:50 Room 1
Hybrid femtosecond laser processing enabled fabricating three-dimensional microfluidic surface enhanced Raman scattering (SERS) chips for highly sensitive sensing of a tiny amount of substances as shown in Fig. 1 . In this paper, to investigate dependence of laser wavelength on the period of ripple which strongly affects the enhancement factor for SERS, two different wavelengths (525 nm and 1030 nm) of femtosecond laser beams were applied for generating periodic surface nanostructures (nanoripple) on Cu-Ag double metal layers. The metal layers were formed in a closed glass microchannel by selective metallization technique composed of femtosecond laser direct ablation and successive electroless plating. Femtosecond laser direct writing was able to control the morphology of nanoripple on the metal layers by laser parameters such as laser fluence, laser repletion rate and so on, resulting in formation of homogenous high spatial frequency laser induced periodic surface structure (HFSL). Based on our experimental results, we fabricated SERS substrates using homogenous periodic surface structures by two different wavelengths of femtosecond laser on Cu-Ag double layer, which were used for SERS detection of rhodamine6G (R6G) in glass microfluidic chip. The SERS results presented that with narrower groove width of the nanoripple fabricated by 525 nm femtosecond laser, the SERS intensity was more enhanced and the SERS analytical enhancement factor was evaluated to exceed 1 × 108. We used the SERS microfluidic chip for the detection of coumarin (detect limit of coumarin is 10-7 M). Meanwhile, we further developed a novel method to realize extremely sensitive sensing, by which detection limit of aM of R6G achieved. The developed technique was able to locally aggregate the analyte molecules by laser irradiation at the interface between air and solution containing the analytes in microchannel. The aggregation of analytes forced the molecules to enter into the “hot-spots”, specifically inside the metal nanogrooves, which significantly increased the SERS intensity. By this technique, we realized extremely sensitive SERS sensing, and amazingly SERS analytical enhancement factor exceeding 1 × 1012 was achieved.
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