THz metasensors based on grating-patterned GaN/SrTiO3 heterostructures for Sudan I trace detection.

Food safety is crucial, and excessive food additives may cause cancer. In this paper, four novel semiconductor-ultrasurface sensors are proposed to significantly improve the sensitivity and realize the trace detection of Sudan red I. The experimental results show that the GaN-based hypersurface sensor has a low limit of detection (LOD) of 12.5 fg/mL for Sudan I, with a sensitivity far exceeding that of the conventional structure. The grating-patterned gallium nitride enhances the terahertz wave interaction with the analyte through a localized electric field, and its transmission spectrum develops from a single amplitude change to an amplitude-frequency bi-dimensional change, with a maximum frequency shift up to 297.54 GHz. further, the strontium titanate/gallium nitride heterostructure results in a maximum ΔT% = 12.91%. This study realizes the highly sensitive detection of Sudan I and provides a new method for the application of terahertz technology in food safety.