High-sensitivity identification of aflatoxin B1 and B2 using terahertz time-domain spectroscopy and metamaterial-based terahertz biosensor

Aflatoxin B1 and B2 are extremely toxic to humans and commonly found in agricultural and food products. Thus, rapid and accurate detection and identification of these substances is essential to prevent human and animal health problems due to their consumption. Here, we present a metamaterial-based terahertz biosensor that has the potential for high-sensitivity, quantitative identification of aflatoxin B1 and B2 in extremely small amounts. By combining with conventional terahertz time-domain spectroscopy and the Maxwell-Garnett effective medium theory, we directly obtained accurate information of the refractive index, absorption coefficient, and dielectric function of these aflatoxins, which are essential parameters to understand their physical properties for their identification. Furthermore, the resonant frequency of the proposed biosensor was in a frequency range wherein the largest difference between the two aflatoxins was observed. In addition, the sensing of aflatoxin B1 and B2 was demonstrated as a function of content, thickness and dielectric constant by the THz biosensor and finite-element simulation. Consequently, a qualitative and quantitative identification of trace aflatoxin B1 and B2 without label was achieved.