Tracing pictogram-level chlorothalonil pesticide based on terahertz metal–graphene hybrid metasensors

A metal–graphene hybrid metasensor in the terahertz (THz) regime has been proposed and experimentally demonstrated for the detection of pictogram-level chlorothalonil solution. Due to Fermi level of graphene tuned by the drip-dried pesticide at different concentrations, the reflective THz intensity could be modulated both in temporal and spectral domain. Furthermore, the designed metamaterial structure support the excitation of toroidal dipole mode at the resonant frequency. These characteristics enable a detection limit down to 100 pg mL−1. Hence, metal–graphene​ hybrid metamaterial in conjunction with the toroidal dipole resonance paves new way toward developing ultrasensitive THz sensors, which is promising for various applications in environmental monitoring and food safety.