Graphene-based meta-sensor for multi-dimensional analysis of prochloraz trace-level detection at terahertz frequencies

The terahertz (THz) meta-sensor has demonstrated significant potential for detecting pesticide residues by enhancing the interaction between THz waves and analyte molecules. In this Letter, we propose a graphene-based toroidal resonance meta-sensor (Gra-TRMS) for trace-level detection of prochloraz along with a corresponding multi-dimensional sensing performance analysis method. Benefiting from the initial Fermi level of chemical vapor deposition (CVD) graphene being slightly offset from the Dirac point, the proposed Gra-TRMS enables highly sensitive detection of prochloraz concentrations ranging from 0 pg/mL to 400 pg/mL. This is achieved by leveraging the variations in toroidal dipole response intensity induced by subtle external stimuli that shift the Fermi level towards the Dirac point. To comprehensively analyze the sensing performance, we combined the transmission peak amplitude (TPA), maximum wavelet coefficient (MWC), and effective transmission area (ETA) to construct a three-dimensional Transmission Correlation Coefficient Triangular Cone (TCCTC), which increased with the prochloraz concentration, providing a clear and intuitive representation of multi-dimensional sensing. The proposed Gra-TRMS with its multi-scale feature analysis opens an exciting prospect for the applications of THz meta-sensor in trace-level sensing detection.