| With the rapid development of modern agriculture,increasing pesticides has been used to ensure the quality of agricultural products,and the corresponding problems of pesticide residue detection is urgently needed.Traditional pesticide residue detection methods often require professional operations and lots of time.In contrast,terahertz spectroscopy has the characteristics of easy operation,short time-consuming,low cost and non-destructive,which has great potential in pesticide residue detection.In this paper,terahertz frequency domain spectroscopy is used to detect trichlorfon in soil and water.Besides,metamaterial is used to enhance the ability of sensing.The main work of this paper as follows:(1)The study on the terahertz absorption peak of the trichlorfon.The terahertz frequency domain spectroscopy system was used to obtain the terahertz absorption spectra of the trichlorfon.Three unique characteristic absorption peaks were found.The theoretical vibrational frequency of trichlorfon molecule was obtained by the density functional theory,and the source of the three characteristic absorption peaks was explained.The accuracy of the experimental data was verified.(2)The study on the detection of trichlorfon in soil and water.The spectra of trichlorfon with different concentrations in soil and water were collected by terahertz frequency domain spectroscopy system.The partial least squares regression was used to establish the model,and the accuracy of the model was judged by correcting the root mean square error,predicted root mean square error,and cross validated root mean square error.Quantitative analysis and residue prediction of trichlorfon in soil and water were realized,and it is proved that terahertz frequency domain spectroscopy detection technology combined with chemometric methods can realize the detection of pesticide residues in soil and water.(3)The study on the enhanced detection of trichlorfon based on the metamaterial.The metamaterial consisted of a period array of two concentric double split ring resonators was designed.The Fano resonances were demonstrated by breaking the symmetry(position asymmetry and gaps asymmetry).The performance of tunability and sensing in Fano resonances were both studied in detail.Fano resonances with different asymmetry deviations are calculated for performance optimization.The Fano resonances with the highest Fo M were used for the detection of analyte at different refractive indices,and the Fano resonance performing the best was further applied in the detection of the analyte at different thicknesses.By adding the analyte trichlorfon on the metamaterial,the enhancement effect of the designed metamaterial structure on the detection of trichlorfon was studied.The results show that the tunned Fano resonances have shown great potential in the detection of pesticide residue,providing a method for designing efficient modulators and sensors. |
