Novel low-cost periodic and flexible SERS substrate fabrication via soft lithography and glancing angle deposition technique.

A highly periodic, low cost, scalable and flexible SERS substrate fabricated via soft lithography and glancing angle deposition (GLAD) technique is reported. The present approach relies on utilizing periodic data writing tracks of a used Blu-ray disk as a template to replicate intrinsic periodic pattern over polydimethylsiloxane (PDMS) films followed by the growth of ordered arrays of silver (Ag) nanostructures via GLAD technique. The resulting periodic array of Ag nanostructures with ~ 270 nm spacing, generates dense electromagnetic (EM) hotspots resulting in EM field enhancement thereby surface-enhanced Raman scattering (SERS) through localized surface plasmon resonance (LSPR) effect. Thiram was used as an analyte to determine the sensitivity of the fabricated SERS substrate. The statistically calculated value of limit of detection (LOD) for thiram is 1.99 × 10–17 M. The analytical enhancement factor for the most intense Raman band of thiram is 1.2 × 109. The number of molecules based enhancement factor for the prominent vibrational band (1513 cm-1) of rhodamine 6G (R6G) is 1.054 × 107. These substrates exhibited excellent reproducibility (RSD ~ 7.26%), repeatability (RSD ~ 5.85%) and long-term stability (90% signal retention under 30 days vacuum storage). The good mechanical strength of the substrate is supported by the signal retention of 90.31% under tensile strain of 26% and 58.7% of signal retention after one complete cycle of bending and releasing to original state. Thus, the fabricated substrate demonstrates a strong potential as an efficient ‘paste-and-peel’ SERS platform for analyte detection on topologically curved surfaces.