Design And Performance Analysis Of THz Metamaterial Device For Pesticide Residue Detection

Controlling pesticide residues in agricultural products has become an important livelihood issue related to people's lives and health.How to quickly,effectively and highly sensitively detect pesticide residues in agricultural products is an important research topic to ensure life,health and food safety.The existing detection techniques and methods have disadvantages such as cumbersome detection steps,long detection time,and low detection accuracy.Terahertz spectroscopy has unique advantages in the field of substance identification because of its penetrability,security,and unique fingerprint peaks.In this paper,numerical research and experimental research are combined to study the design of terahertz metamaterial devices,and analyze its performance and sensing mechanism.On this basis,researches on the detection of pesticide residues based on metamaterial sensors have been carried out.The main research contents and conclusions are as follows:(1)Numerical simulation study of metamaterial sensor design.The numerical modeling process of metamaterial structures is introduced,and the influence of metamaterial structure parameters on the modulation performance of terahertz waves is explored.The results show that the addition of external trace substances will cause the change of the dielectric environment of the metamaterial surface;the local electric field enhancement caused by the metasurface can pass the change of the resonance peak(including the change of the resonance peak frequency and the quality factor),and the external dielectric Respond to changes in the environment,thereby significantly improving the detection sensitivity of the target.(2)Experimental study on the sensitivity of metamaterial sensor for detection of chlorothalonil.A metamaterial sensor for the detection of chlorothalonil pesticide was designed and prepared,and the performance of the sensor was studied experimentally.The results show that with the increase of the concentration of chlorothalonil,the resonance peak of the sensor is red-shifted;compared with the detection method that only uses the characteristic fingerprint,the sensitivity is increased by 10~6 times,and the minimum detection limit can reach 1 mg/L.(3)Experimental study on influencing factors of sensitivity of metamaterial sensor for pesticide residue detection.Two metamaterial sensors are designed to detect three pesticides using the sensors to study the influence of metamaterial structure,detection object,and detection object volume on sensitivity.The results show that for low-concentration analytes,the degree of matching between the characteristic peaks of the detected substance and the characteristic peaks of the metamaterial structure has a decisive influence on the detection sensitivity;for high-concentration analytes,the sensitivity of the metamaterial structure itself has an important influence on the detection sensitivity.When detecting a solution,the larger the volume of the dropped solution,the greater the value of the frequency shift,and the higher the detection sensitivity.The higher the dielectric constant value of the detection object itself,the lower the detection sensitivity.