Facile Bacterial Cellulose Nanofibrillation for the Development of a Plasmonic Paper Sensor

In this present work, a plasmonic sensor is developed through an extremely cheap cellulose-based source, widely known as a food product, nata de coco (NDC). Capturing its interesting features, such as innate surface roughness from naturally grown cellulose during its fermentation period, the engineering and modulation of NDC fibril size and properties were attempted through a high-pressure homogenization (HPH) treatment to obtain highly dense nanofibrils. After the transformation into a thin, paper-sheet form through a casting process, the homogenized bacterial cellulose (HBC) resulting from HPH was compared with the normally agitated bacterial cellulose (BC) pulp and decorated with silver nanoparticles (AgNPs) to produce plasmonic papers, for further application as surface-enhanced Raman scattering (SERS) substrate. As demonstrated in the measurement of Rhodamine 6G (R6G) molecule, the plasmonic HBC paper sheet provided more prominent SERS signals than the plasmonic BC due to its high surface roughness and improved textural properties from the nanofibrillation process favoring better adsorption of AgNPs and effective SERS hotspots generation. The plasmonic HBC obtained a 2 order higher estimated SERS enhancement factor over the plasmonic BC with a limit of detection of approximately 92 fM. Results denote that the proposed approach provides a new, green-synthesis route toward the exploration of biodegradable sources integrated into an inexpensive and simple nanostructuring process for the production of flexible, paper-based, plasmonic sensors.