MoS2-enhanced epoxy-based plasmonic fiber-optic sensor for selective and sensitive detection of methanol

Plasmonic nanostructures have found widespread applications in nanophotonics, photochemistry and optoelectronics, and chemical sensing is one of their most vibrant applications. However, it still remains open to achieve selective detections with plasmonic nanostructures, especially, at room temperature. Polymers have been attractive as vapor sensitive materials as their electrical and optical properties vary with exposure to vapors at room temperature. MoS2, as an emerging 2D material, has facilitated chemical sensing due to its stability, ultrahigh surface-to-volume ratio, and various attractive sites for analyte molecule adsorptions, including sulfur defect, vacancy, and edge sites. The combination of both MoS2 and polymers with plasmonic has great potential to enable high performance gas sensing at room temperature. Here, a selective detection towards methanol vapors is demonstrated using an epoxy as a sensitive polymer material to bond methanol molecules via both hydrogen atoms and the lone electron pairs on the hydroxyl group. Using a MoS2 monolayer coating, improved sensing response and selectivity towards small-size vapors, especially oxygen-functionalized methanol, are observed because of selective filtration effect. In addition, this plasmonic sensor is insensitive to relative humidity variation in the range of 11 %RH to 92 %RH as well as stable over a long-term period of one year, which demonstrates the high potential of the sensor for practical applications. These findings pave the way for a generic strategy to design selective and sensitive gas sensors via the combination of selectivity-enabling polymer, sensitivity-enhancing 2D materials and signal-transducing plasmonic nanostructures.