Sensitive detection of chlorpyrifos pesticide using an all-dielectric broadband terahertz metamaterial absorber

Metamaterial absorbers consisting of metal, metal-dielectric, or dielectric materials display properties that make them feasible for use as signal enhancement tools to quantitatively detect traces amounts of samples. We propose an all-dielectric broadband terahertz absorber on a highly-doped silicon-based sensing chip. This semiconductor metamaterial absorber exhibits an experimental absorption of similar to 99 % at 1.33 THz and a broad bandwidth (absorption of >= 90 %) that covers 600 GHz of the center frequency. The measurement agreed well with the simulations and calculations and the wide tuning ability of the absorber was verified by optical excitation. Furthermore, we demonstrated that this metamaterial absorber, as a highly stable THz sensor to temperature, humidity and time, shows promise in detecting trace pesticides. Regression coefficients between chlorpyrifos concentrations (0.1, 1, 10, 50 and 100 mgL(-1) ) and the corresponding spectral peak intensities and the frequency shifts near 0.93 THz were 0.9943 and 0.9750, respectively. The detection limit of chlorpyrifos reached a level of 0.1 mgL(-1), and the frequency response of the absorber to 10 mgL(-1) chlorpyrifos solution was 4.6 GHz. These results indicate that the combination of THz spectroscopy and metamaterials can be used in the detection of chemical and biological materials with high sensitivity and stability, providing a new strategy for future applications in the fields of food and agriculture.