Single-Molecule Cholesterol Sensing by Integrating Silver Nanowire Propagating Plasmons and Graphene Oxide π‑Plasmons on a Photonic Crystal-Coupled Emission Platform

The escalating concern about ohmic losses in metal-dependent plasmonics demands more effective material fabrication for the development of biosensing frameworks. The omnidirectionality and low signal collection efficiency of a conventional fluorescence-based detection platform make it challenging to realize better sensitivity for real-time point-of-care diagnostics. In an attempt to address these demands, recently a photonic crystal-coupled emission (PCCE) platform has been demonstrated to outperform the well-established surface plasmon-coupled emission platform for biophysicochemical sensing applications. The effects of the different numbers of bilayers (BLs) of a one-dimensional photonic crystal (1DPhC) on the electric field intensity of Bloch surface waves and internal optical modes (IOMs) are extensively studied in this work to improve the performance of the PCCE platform rationally. Specifically, the 1DPhC with 10 BLs presented 55-fold PCCE enhancements because of the strong field confinement by the IOMs and small losses. In addition, the critical role of nanoengineering graphene oxide π-plasmon and silver nanowires on the PCCE platform has been explored to yield an unprecedented >1300-fold increase in fluorescence intensity. The amplified PCCE enhancements obtained with the first experimental evidence of the synergism among dielectric plasmons (1DPhC), graphene oxide plasmons, and metal plasmons (from silver nanowires) have been utilized to sense cholesterol at the single-molecule limit of detection. The photoplasmonic sensor presented here exhibits potential utility in academia and industry and provides a perspective for combining materials at nanoregimes for the desired applications.