三维石墨烯/氧化铜纳米酶在草甘膦检测中的应用

Three-Dimensional Graphene/Copper Oxide Nanocomposites Nanozymes for Colorimetric Sensing of Glyphosate

作为应用广泛的有机磷除草剂之一,大量使用的草甘膦会对动物和水生植物造成不良影响。因此,快速简便的检测草甘膦对环境监测工作十分重要。本文以三维石墨烯为基底,采用水热法制备了具有过氧化物酶活性的三维石墨烯/氧化铜复合材料。三维石墨烯与氧化铜纳米颗粒间的协同作用使三维石墨烯/氧化铜复合材料具有较高的过氧化物酶催化活性。研究发现,当少量草甘膦加入三维石墨烯/氧化铜复合材料复合材料-TMB-H_(2)O_(2)体系时,可以显著抑制三维石墨烯/氧化铜复合材料的过氧化物酶催化活性。基于草甘膦对三维石墨烯/氧化铜复合材料的过氧化物酶催化活性的显著抑制作用,建立了草甘膦的比色检测方法。该方法草甘膦检测的线性范围为0.05~5μmol·L^(-1)和5~300μmol·L^(-1),检出限为0.02μmol·L^(-1),低于中国对饮用水中草甘膦的限定值(4.14μmol·L^(-1))。方法线性范围宽、检出限低,可用于草甘膦的低成本常规快速分析。

Glyphosate,a post-emergence,non-selective organophosphorus herbicide with excellent weed control performance and low toxicity to mammals,is widely used throughout the world.Due to the high solubility,leaching characteristics and long half-life,the abuse of glyphosate has resulted in high residues in various environmental systems,posing a threat to human health.Recent researches showed that glyphosate had disadvantages of genotoxicity,carcinogenicity,and potential endocrine disruption,and has been included in the"priority pollutant"list made by China and the USA.The conventional methods for glyphosate detection are high-performance liquid chromatography and gas chromatography-mass spectrometry.However,derivatization procedures must be carried out to improve the sensitivity of glyphosate detection.Therefore,it is urgent to develop a simple,low-cost,rapid,and sensitive method for glyphosate determination.In this study,three-dimensional graphene/copper oxide(3D GF/CuO)nanocomposites with peroxidase activity were prepared by hydrothermal method.3D GF/CuO nanocomposites were characterized by scanning electron microscope(SEM),X-ray diffraction(XRD),energy disperse spectroscopy(EDS),and Fourier transform infrared spectra(FT-IR).The results showed that the surface of the 3D GF was uniformly and densely covered with flower-like CuO nanoparticles(CuO NPs).CuO NPs possessed a microscopic three-dimensional structure,and the crystal structure of CuO NPs belonged to the monoclinic system.3D GF/CuO nanocomposites was composed of C,O and Cu without other impurities.The peroxidase-like catalytic activity of the as-prepared 3D GF/CuO nanocomposites was investigated.The measurements were performed by monitoring the absorbance change of 3,3′,5,5′-tetramethylbenzidine(TMB)at 652 nm using the ultraviolet-visible spectrophotometer.The results showed that the as-prepared 3D GF/CuO nanocomposites had a peroxidase catalytic activity similar to horseradish peroxidase.Control experiments showed that the pure CuO NPs exhibited inferior peroxidase-like activity than 3D GF/CuO nanocomposites and 3D GF had no peroxidase-like activity.The higher peroxidase-like catalytic activity of 3D GF/CuO composites was attributed to the synergy between 3D GF and CuO NPs.Previous studies showed that glyphosate contained carboxyl and phosphonyl functional groups.Hence,a strong metal affinity binding force existed between glyphosate and Cu ions.Therefore,the glyphosate would be adsorbed on the surface of 3D GF/CuO nanocomposites owing to the metal affinity binding force between glyphosate and Cu ions in 3D GF/CuO-H_(2)O_(2)-TMB system.This could lead to a drastic loss of active sites and result in a substantial drop of the catalytic activity of 3D GF/CuO nanocomposites.Accordingly,when glyphosate was introduced into 3D GF/CuO-H_(2)O_(2)-TMB system,the color reaction of TMB was weakened.Therefore,the concentration of glyphosate could be determined indirectly by measuring the absorbance change of TMB in the system.In order to obtain best sensitivity and linear range,the effect of H_(2)O_(2)concentration on the determination of glyphosate was further studied.Consequently,the method exhibited high detection sensitivity with the H_(2)O_(2)concentration of 40 mmol·L^(-1).Based on the peroxidase-like catalytic activity of the as-prepared 3D GF/CuO nanocomposites,a new colorimetric detection for glyphosate was developed.The linear range was from 0.05 to 5μmol·L^(-1)and 5 to 300μmol·L^(-1)with detection limit of 0.02μmol·L^(-1).Under±5%relative error,it was found that 10-fold Na^(+),Mg^(2+),Ca^(2+),NH_(4)^(+),Cl^(−),NO_(3)^(−),CO_(3)^(2−)had no significant effect on the detection of glyphosate.The catalytic activity could be maintained at 95%after 10 cycles,indicating the high stability of as-prepared 3D GF/CuO nanocomposites.Overall,the developed rapid and simple 3D GF/CuO nanocomposites based visual detection method,with good selectivity and high stability,was suitable for routine analysis of glyphosate.