Flexible silver nanoislands-decorated cigarette inner liner paper as an efficient SERS substrate for on-site monitoring of pesticide residues

Paper-based surface-enhanced Raman scattering (SERS) substrates have garnered considerable attention as eco-friendly, sensitive platforms for trace-level pesticide residue detection. Nevertheless, the development of paper-based SERS substrates that can simultaneously meet the requirements of scalable fabrication, high sensitivity, and excellent reproducibility remains a critical challenge. Herein, a flexible paper-based SERS substrate was fabricated by employing cigarette inner liner paper (CILP) as a supporting matrix, on which silver nanoislands (Ag NIs) were uniformly deposited via a facile, scalable magnetron sputtering approach. The water-absorbent surface of CILP possesses a hydrophilic porous structure that can efficiently enrich analytes and form spatially distributed SERS hotspots after decoration with Ag NIs. Meanwhile, the waterproof back layer of CILP effectively inhibits liquid penetration and prolongs the residence time of analyte solutions on the absorbent surface. After optimizing the sputtering time, the as-prepared Ag NIs@CILP substrate achieved favorable detection performance for rhodamine 6G with a detection sensitivity down to 10 −8  M, together with good uniformity (relative standard deviation, RSD = 3.44%) and reliable reproducibility (RSD = 4.63%). When integrated with a portable Raman spectrometer, this SERS substrate enabled the trace detection of malachite green in spiked lake water (10 −6  M) and thiram on spiked apple peels (10 −7  M). These results validate that the developed paper-based SERS substrate holds great potential for rapid on-site monitoring of pesticide residues in aquatic environments and on fruit surfaces.