Research And Application Of Drug Detection Method Based On Terahertz Spectrum

The vibration transition of molecules in THz band mainly includes the rotation and vibration modes of the whole molecule and the vibration modes between molecules,which represent the material itself and have the characteristics of fingerprint.In addition,THz light wave has the characteristics of low photon energy and strong penetrability,which can be applied in the field of nondestructive testing.This project uses density functional theory(DFT)to simulate the map of five drug molecules in band 0.5-10 THz on the Gaussian09 software,and obtains the vibration mode of five drug molecules in band 0.5-10 THz,which provides reference for explaining the microscopic vibration mechanism of five drug molecules in this band.Fourier transform infrared spectroscopy(FTIR)and THz time domain spectroscopy(THz-TDS)were used to detect five kinds of drug standard.A variety of THz absorption spectrum databases of drugs are established,and a computer identification model is tried to be established to identify and identify the unknown map,so as to explore a new method for the rapid discovery and identification of drugs at customs ports.Main findings include: 1.The density functional theory(DFT)in quantum computational chemistry was used to simulate the single-molecule model of cocaine,ketamine hydrochloride,cannabinol,heroin and morphine in Gaussian09 software.The results showed that there were several characteristic absorption peaks in the range of 0.5-10 THz.The vibration modes of five drug molecules in the range of 0.5-10 THz band were obtained by the visualization function of Gauss View6.0.2.The THz absorption spectra of cocaine,ketamine hydrochloride,cannabinol,heroin and morphine were compared between the Fourier transform infrared spectrometer(FTIR)and THz-TDS systems.The results show that the THz absorption spectra obtained by the two different detection technologies are highly consistent in the same frequency band,but the portable THz-TDS system is more suitable for practical application scenarios such as customs ports.Compared with the simulation results,it is found that the experimental results are roughly consistent with the simulation results,so the simulation results can be used as a reference to explore the attribution of molecular vibration mode.3.A portable THz-TDS system was used to establish a database containing THz absorption spectra of 29 drug standards,which provided data basis for the practical application of THz-TDS system.A recognition model was established by fully connected neural network,and the recognition accuracy of drug mixtures containing more than 70% was 100%.This study provides an effective way for the application of portable THz-TDS system in customs ports and other practical detection scenarios to quickly and efficiently judge whether unknown substances are drugs and what kind of drugs.