SERS Enhancement of Porphyrin-Type Molecules on Metal-Free Cellulose-Based Substrates

The detection of analytes using spectroscopy methods, such as surface-enhanced Raman spectroscopy (SERS), is crucial in the fields of medical diagnostics, forensics, security, and environmental monitoring. In recent years, a lot of focus has been directed toward organic polymer material-based SERS platforms due to their lower cost, controllable synthesis and fabrication, structural versatility, as well as biocompatibility and biodegradability. Here, we report that cellulose nanofiber-based substrates can be used as a metal-free SERS platform for the detection of porphyrin-type molecules. We report SERS signal enhancement for five different porphyrin molecules with exceptional 2 orders of magnitude peak intensity enhancement observed resulting in a detection limit of 10-5 M. We show that the cellulose-based platform is more suitable for porphyrin molecule detection than traditionally used semiconductor materials like graphene oxide. The observed enhancement is attributed to the disturbed growth of self-assembled structures on the cellulose nanofibers and the generation of disordered 3D clusters of porphyrin molecules.