Eco-sustainable and flexible SERS platform based on waste cellulose decorated by Ag nanoparticles

This paper presents an innovative and environmentally friendly technology for the fabrication of low-cost SERS (Surface-Enhanced Raman Spectroscopy) sensors based on flexible substrates made of cellulose fibers reclaimed from waste. The substrates are decorated with nanostructured silver (Ag) thin films produced by pulsed laser deposition (PLD). In this process, the deposition conditions (laser fluence, gas pressure, target-substrate distance, deposition time, etc.) were optimized to enhance the SERS response. Different types of paper with different textures were tested, as it was also observed that the paper roughness significantly influences SERS efficiency. The samples were characterized using UV–Vis absorption spectroscopy, SEM microscopy, and surface profilometry to evaluate both the paper and the deposited films' morphologies. The SERS activity was assessed by detecting Rhodamine 6G in aqueous solutions drop-casted on the sensors, with concentrations ranging from 10⁻² M to 10⁻¹⁰ M. Measurements were carried out using a handheld instrument equipped with dual excitation laser lines centered at 785 nm and 833 nm. The observed lower detection limit of 10⁻¹⁰ M was achieved across all paper types tested. These results demonstrate the potential of integrating smart, eco-friendly materials in the fabrication of chemical sensors for sustainable advancement in environmental monitoring and safety. The materials not only exhibit excellent sensing capabilities but also minimize ecological footprints through renewable sourcing and eco-friendly production processes. While the deposition protocol is well-established for other substrates, this study marks the first exploration of its use on biomass-derived substrates.