Terahertz sensing of chlorpyrifos-methyl using metamaterials

•Signal enhancing method for terahertz detection.•Terahertz metamaterials based sensing technology.•Sensitivity of chlorpyrifos-methyl can reach to 0.204 mg L−1.•A new and sensitive method for terahertz pesticide detection.•Great potential for future quick and robust terahertz detection.

By squeezing electromagnetic energy into small volumes near a metal-dielectric interface, plasmonics provide many routes to enhance and manipulate light-matter interactions, which presents new strategies for signal enhancing technologies. As an extension of the ideas of plasmonics to the terahertz (THz) range, metamaterials have shown great potential in sensing applications. In this study, terahertz time-domain spectroscopy (THz-TDS) combined with metamaterials was used to detect chlorpyrifos-methyl (CM), which is one type of the broad-spectrum organophosphorus pesticides. The results demonstrate that sensitivity is greatly improved using THz metamaterials, with the limit of detection (LOD) of CM reaching 0.204 mg L−1, which is lower than the World Health Organization's provisional guideline limit for CM in vegetables (1 mg L−1). The results indicated that THz spectroscopy combined with metamaterials could be a valuable method for highly sensitive THz applications, presenting a new strategy for food quality and safety control in the future.