基于银纳米粒子的局域表面等离子体共振效应提高草甘膦基于茚三酮间接检测的灵敏度

Improved Sensitivity of Localized Surface Plasmon Resonance Using Silver Nanoparticles for Indirect Glyphosate Detection Based on Ninhydrin Reaction

常规的农药残留检测一般存在前处理操作复杂,耗时较长,方法不够灵敏等问题。根据氨基与茚三酮显色原理和局域表面等离子体共振(LSPR)增强光吸收原理,利用紫外-可见吸收光谱对水样品中草甘膦含量进行定量分析,并利用密度泛函理论进一步分析了显色的类似罗曼紫产物的光吸收增强机理。草甘膦与茚三酮在钼酸钠催化下反应生成类似罗曼紫产物;该物质在紫外–可见吸收光谱570 nm处有最大吸收峰,当其吸附在银纳米粒子(Ag NPs)表面上时,最大吸收峰蓝移至568 nm处,同时吸收强度显著提高;本研究中检出限为2.0174×10^(-11) mol·L^(-1),显著低于文献中约6.5×10^(-7) mol·L^(-1)的检出限。Gaussian 09软件计算得出,类似罗曼紫产物经由茚三酮的C O基团垂直吸附在Ag NPs表面,静电势表明茚三酮的C O基团优先与Ag稳定相互作用并形成Ag—O键,C O基团和C—N基团构成了π键共轭系统;连接草甘膦和茚三酮之间的C—N键是类似罗曼紫产物的生色团。因此,茚三酮衍生法可用于间接检测水样品中草甘膦,银纳米粒子LSPR效应增强了光吸收强度,比常规方法具有更高的灵敏度。

Conventional pesticide residue detection still suffers from numerous steps,is long time-consuming,and insufficient delicacy.According to ninhydrin colouring and the principle of localized surface plasmon resonance(LSPR)enhancing absorption,glyphosate in water samples can be detected by ultraviolet-visible spectroscopy(UV-Vis).Furthermore,density functional theory is used to analyze the enhancement mechanism of absorption of purple color dye(PD)products.The PD product displays a maximum absorption of around 570 nm when glyphosate reacts with ninhydrin is detected by UV-Vis.There are slight shifts from 570 nm in the UV-Vis spectrum to 568 nm with a stronger peak when the PD product is absorbed on Ag NPs,and the limit of detection at 2.0174×10^(-11) mol·L^(-1),which is much lower than 6.5×10^(-7) mol·L^(-1) limit of detection reported.Gaussian 09 software carried out that the PD product would attach to Ag NPs via an Ag—O bond through ninhydrin’s C O group vertically.MEP mapping provides C O group interaction with Ag NPs stable,C O group coupled C—N comprise a largeπ-conjugated system in their plane.The color of the C—N group is blue,which suggests that C—N coupled with the C O group are the chromophore in the PD product.Thus,an indirect detection method derived from ninhydrin can be used for glyphosate detection in water samples.The LSPR effect of Ag NPs enhances the absorption intensity with higher sensitivity than the conventional method.