Controllable fabrication of silver-deposited polyurethane acrylate nanopillar array film as a flexible surface-enhanced Raman scattering (SERS) substrate with high sensitivity and reproducibility

A controllable method for fabricating flexible surface-enhanced Raman scattering (SERS) substrates is demonstrated by depositing silver onto a flexible nanopillar array film. The flexible nanopillar array film was cost-effectively prepared by replicating an anodic aluminum oxide (AAO) template with UV-curable polyurethane acrylate (PUA) over a large area. Then, the deposition of silver was done by an Ar-assisted thermal evaporation. In the deposition process, the partial pressure of Ar was optimized because it has a significant influence on the SERS intensity through the microstructural changes of silver deposited on PUA nanopillars. In addition, the increase in the nanopillar diameter and height enhanced the SERS intensity obtained at 785-nm excitation because of the increased number of hot spots. However, the agglomeration of Ag-deposited nanopillars, which is caused by high aspect ratios, negatively affected the SERS performance in terms of intensity and standard deviation. The optimized Ag-deposited nanopillar array film with nanopillar diameters and heights of 80 nm and 200 nm exhibited excellent SERS sensitivity and signal reproducibility with stable mechanical flexibility. For application in food and biomedical analysis, it was used for detecting saccharin and peptide and showed a good linear relationship between the SERS intensity and concentration. These findings demonstrate the suitability of our method for the controllable fabrication and optimization of flexible SERS substrates with high sensitivity and reproducibility. Graphical abstract