Paper-Based Substrate for a Surface-Enhanced Raman Spectroscopy Biosensing Platform—A Silver/Chitosan Nanocomposite Approach

Paper is a popular platform material in all areas of sensor research due to its porosity, large surface area, and biodegradability, to name but a few. Many paper-based nanocomposites have been reported in the last decade as novel substrates for surface-enhanced Raman spectroscopy (SERS). However, there are still limiting factors, like the low density of hot spots or loss of wettabil-ity. Herein, we designed a process to fabricate a silver–chitosan nanocomposite layer on paper celluloses by a layer-by-layer method and pH-triggered chitosan assembly. Under microscopic obser-vation, the resulting material showed a nanoporous structure, and silver nanoparticles were an-chored evenly over the nanocomposite layer. In SERS measurement, the detection limit of 4-amino-thiophenol was 5.13 ppb. Furthermore, its mechanical property and a strategy toward further bio-sensing approaches were investigated.