Large-area sensors using Cd(Zn)O plasmonic nanoparticles for surface-enhanced infrared absorption

Surface-enhanced infrared absorption (SEIRA) spectroscopy holds significant promise for chemical detection as it enables direct identification of distinct vibrational fingerprints of molecules. Traditionally, SEIRA has been exploited through the use of tailored metallic nanoantennas, which are burdened by high losses in the mid infrared and costly nanofabrication techniques. In this work, we introduce an alternative, simpler approach using self-assembled Cd(Zn)O nanoparticles as a SEIRA platform. We demonstrate enhancements of the vibrational absorption of several molecular bonds in polymethyl methacrylate and vanillin up to a factor of 4.3. Such enhancements scale linearly with the surface density of nanoparticles, which can be controlled through the growth conditions. Thanks to the tunability of our platform, we report extended sensing capabilities to high energies in the mid-IR, reaching as high as 3,800 cm^-1. All in all, we present a proof of concept for large-area, simple preparation, ready-to-sense surfaces that has the potential to be scaled up to become a prominent technology for mid-IR molecule sensing.