Preparation And Application Of Myclobutanil Molecularly Imprinted Polymer And Its Photonic Crystal Sensor

Triazole pesticides is one of fungicides commonly used in tobacco cultivation.Its excessive dosage will lead to pesticide residue,which will harm human health and affect Chinese tobacco export trade.Therefore,the regulation of pesticide residues in tobacco is particularly important,and it is necessary to establish rapid and efficient trace detection techniques for triazoles in tobacco leaves.In the paper,a rapid and visual detection of Myclobutanil(MDT)in tobacco leaves was developed into a molecularly imprinted photonic crystal hydrogel(MIPH)sensor.Firstly,the molecularly imprinted solid-phase extraction(MISPE)removed complex matrices from samples,then the pre-processed samples were detected by the photonic crystal sensor,with which target molecules were recognized by MIPH through converting chemical signals into optical signals.In this way,MDT could be qualitatively detected by human naked eyes or semi-quanti ficationally detected with the help of UV-vis.The main research contents are as follows:(1)Self-assembly process of MDT molecularly imprinted prepolymerization systemMDT molecularly imprinted prepolymerization system was designed based on the density functional theory(DFT).The optimal functional monomer was 2-(trifluoromethyl)acrylic acid(TFMAA),and the ratio of myclobutanil was 1:4,the best solvent was toluene,and the prepolymerization temperature was 35?.The infrared spectrum of the MDT-TFMAA complex was estimated and its binding sites were confirmed,which were very similar to the actual polymer.The accuracy of the prediction was verified for MDT-TFMAA complex structure.The above results could guide the preparation of myclobutanil molecular imprinting polymers(MDT-MIPs),which was beneficial to improve MDT-MIPs'selection recognition and sensitivity.(2)Preparation and Properties of MDT-MIPsBased on simulation results,MDT-MIPs were prepared by bulk polymerization with MDT as template,TFMAA as functional monomer,and toluene as porogen.The average particle size was 134.26nm,the pore volume was 2.45m L/g,the surface area was 143.26m²/g and the porosity reached 78.27%.The MDT-MIPs got its maximum adsorption amount in 90 minutes,and the actual adsorption amount could reach 95.16%of the theoretical adsorption amount.Five kinds of triazole fungicides could be identified,and the imprinting factor range was 2.31-1.92.The relative standard deviation of the elution-adsorption for 5 cycles was 0.41-1.64%,which indicated a good reusability of the nano-material.MISPE was prepared using MDT-MIPs as the adsorbent for sample pretreatment.UPLC-MS/MS was used for quantitative analysis.The results showed that the average recovery rate was 77.86?118.30%in the standard concentration range of 0.1-1?g/g,and the relative standard deviation was 1.90?10.60%,which met the requirements for the detection of triazole fungicides in tobacco leaves.(3)Preparation of SiO₂ photonic crystal hydrogelBy optimizing reaction conditions,such as rotation speed,reaction temperature and time,dosages of alcohol,ammonia and Tetraethoxysilane(TEOS),the good monodispersity and uniform SiO₂ microspheres was prepared in 5 hours.The growth conditions of SiO₂photonic crystal were also optimized,and thin photonic crystal films with high regular arrangement were obtained.(4)Preparation and Application of MDT Molecularly Imprinted Photonic Crystal Hydrogel(MDT-MIPH)SensorThe MDT-MIPH sensor was prepared by a thermal polymerization method.The sensor had good specific recognition,repeatability and stability.Based on the concept that the matrix interference of tobacco leaf could be obviously avoided by MISPE pretreatment and MISPE could quickly detect MDT in tobacco leaf samples,combining MDT-MIPH and MISPE for the detection of MDT bactericide in tobacco leaves.When the MDT-MIPH was immersed in tobacco leaf extracts of three concentrations,the diffraction peaks were red-shifted,and the offset increased with increasing concentration,which showed that the sensor identified MDT with specificity.Because of the red-shifted MDT could be qualitatively detected by human naked eyes or semi-quantificationally detected with the help of UV-vis.