基于磁性Fe3 O4／Ag的表面增强拉曼光谱检测农药丙线磷

摘要

The magnetic Fe3 O4/Ag composite materials were synthesized by reducing AgNO3 with sodium citrate in the presence of Fe3 O4 which were prepared by co-precipitation firstly .The enrichment and extraction of ethoprophos assembled on Fe3 O4/Ag were achieved with the applied magnetic field .The different concentrations of ethoprophos adsorbed on Fe3 O4/Ag were analyzed by SERS and it was showed that the trace analysis of ethoprophos had been established ,while the enhancement factor of probe molecules on Fe3O4/Ag was 1.48 × 105 .The structure and morphology of Fe3O4/Ag were characterized by UV-Vis ,EDX and TEM .Compared with Ag ,the UV-Vis absorption peak of Fe3O4/Ag shifted from 417 to 369 nm ,and the UV-Vis of Fe3O4 al-most had no characteristic absorption peak in this region .At the same time ,it was showed that the surface properties of Fe3 O4/Ag changed with Raman enhancement effect during the aggregation process of Ag around the surface of Fe3 O4 .Further EDX im-ages of micro area element analysis suggested that the chemical composition of products were Ag ,Fe and O while the Cu peak was from the copper mesh .In addition ,TEM images indicated that the average particle size of Fe3 O4 was between 30 and 60 nm with shape tended to be spherical .And the silver nanoparticles were attached to the Fe3 O4 particles and agglomeration occured . Density functional theory calculations which can be applied to qualitative judgment of molecule was carried out to obtain the mo-lecular optimization structure and theoretical Raman spectra .It was found that the stabilized SERS signals were detected under the saturated adsorption equilibrium after 15 min .Finally ,Raman response of ethoprophos was achieved with lower than 2 × 10-8 mol・L -1 ,indicatint that the established method had reached the requirements of ethoprophos residues detection and could be used for analysis of sulfur-containing organophosphorus pesticide .%以共沉淀法合成Fe3 O4纳米颗粒，再通过柠檬酸三钠还原 AgNO3制备 Fe3 O4／Ag磁性复合材料。Fe3 O4／A g能够与溶液中的丙线磷形成吸附，通过磁性收集达到萃取富集的效果。测定吸附于Fe3 O4／A g表面的痕量丙线磷所产生的表面增强拉曼光谱（SERS），其检测过程的拉曼增强因子为1.48×105，极大地提高了检测灵敏度，建立了磁性Fe3 O4／Ag萃取富集与SERS分析农药丙线磷的方法。采用紫外可见吸收光谱、能谱及透射电子显微镜对制备的材料进行了分析及形貌与结构的表征。并对丙线磷模型分子进行结构优化的密度泛函理论计算，得到了理论拉曼光谱和谱峰归属，以用于丙线磷的判断。结果表明，SERS峰强在富集15 min后基本趋于稳定，其丙线磷浓度低至2×10－8 mol・L －1仍有明显响应，可以满足丙线磷农残检测的要求。其方法可推广至含硫有机磷农药残留的分析。