Recent advances in the functionalization of cellulose substrates for SERS sensors with improved performance

Raman spectroscopy is a versatile method to investigate the chemical properties of matter. Thanks to extensive technical developments that lead to analytical devices with high sensitivity and ease of use, it currently finds application in both research and industry. Surface Enhanced Raman Spectroscopy (SERS) in particular, overcomes the low sensitivity of traditional Raman and allows to measure very low concentrations of analyte, even down to single molecule detection. This is obtained through the functionalization of the surface with metal nanoparticles, that generate a strong localized surface plasmon resonance when irradiated at a suitable wavelength, greatly increasing the sensitivity of the devices. Nevertheless, the production of substrates with high sensitivity and reproducibility that avoid high costs, are flexible to adapt to samples with irregular surfaces, and are possibly regenerable and reusable, still remains a challenge. Due to its unique mechanical characteristics, its biodegradability and its low SERS response, cellulose in its various forms represents an ideal substrate for developing SERS sensors with the characteristics mentioned above. This review summarizes 21 studies from 2020 to 2025, that describe cellulose based SERS sensors with remarkable high enhancement factor up to 10 11 . We focused on the functionalization with both metal and non-metal nanostructures, including metal oxides and innovative materials as metal-organic frameworks. This work aims to emphasize how, through the appropriate pre-treatment of the substrate material, it is possible to obtain a better and more homogeneous plasmonic surface, with metal nanoparticles, to improve the sensitivity and the performance of the device.