Herbicide/pesticide sensing with metamaterial absorber in THz regime

Abstract

Terahertz (THz) technology has been attracted great interest in many research areas over the years, especially THz plasmonics for sensing applications since intra- and inter-molecular vibrations are within the THz range. The sensitivity of free-space THz detection can be boosted up by use of metamaterials (MM), which are artificial structures in subwavelength scale of the incident light. These artificial materials present high electric field enhancement and high sensitivity to the change in their surroundings. In this article, residual herbicides/pesticides have been investigated both theoretically and experimentally with a polarization-insensitive THz metamaterial absorber (MMA) composed of dielectric-metal disk antennas. Our THz MMA can detect as small as 5 ppM of commonly used herbicide/pesticide, namely paraquat and glyphosate. The results show that sensitivity is greatly improved by using THz MMA, with the limit of detection (LOD) of these herbicides/pesticides reaching to 5 ppM. These results indicate that THz MMA platform could be a valuable method for highly sensitive THz applications in food quality and safety control. We believe, our sensor platform based on general c-mos technology fabrication could be a potential detection tool for herbicides/ pesticides residues in agriculture and food products.