Flexible, foldable and transparent SERS film with high sensitivity and signal homogeneity via silver ion exchange and in-situ reduction

The adhesion between metal plasma and substrate was the key of surface-enhanced Raman scattering (SERS) technology. The preparation of ideal SERS substrate with multiple advantages such as high sensitivity and good signal reproducibility was still the focus of research. A flexible foldable and transparent fluorinated polyimide/ silver NPs (FPI@Ag) SERS film was fabricated by the ion exchange and in-situ reduction method in this work. The effects of KOH hydrolysis time, AgNO3 ion exchange time and concentration, the type and concentration of reducing agents on the SERS performance of the FPI@Ag film were systematically discussed. As a result, the hydrolysis time of KOH affected the thickness of the metallic silver layer, the concentration of AgNO3 affected the size and spacing of Ag NPs, and the Raman signal of was remarkably enhanced when borane dimethylamine complex (DMAB) was used as reducing agent. When the detection limit of 4-Aminothiophenol was as low as 1 x 10-11 mol center dot L-1, the obvious Raman characteristic peak still appeared. The enhancement factor (EF) was up to 9.4 x 107. The linear quantification range was achieved in the range from 10- 3-10- 11 mol center dot L-1, R2 = 0.9987. In addition, we also performed multi-cycle bending and torsion test on the FPI@Ag film, and obtained stable Raman signals. The prepared FPI@Ag film can be attached to the surface of uneven samples, which can be used for on -site Raman detection and analysis.