Study On Construction Of Novel Photo/Electrochemical Sensors Based On Nanomaterials For Detection Of Heavy Metal Ions And Pesticide Residues In Food

In recent years,with the rapid development of our country’s food industry,food safety issues have gradually emerged.Compared with traditional detection methods,photo/electrochemical sensors have shown great application prospects in the field of food safety detection due to its advantages of miniaturization,simple operation,high sensitivity as well as fast response.At the same time,nanomaterials with excellent and unique properties have played an important role in many fields such as biomedicine,mechanical industry,sensing and so on.The combination between nanomaterials and photo/electrochemical sensors can improve the detection performance of the sensors.To construct photo/electrochemical sensors with high sensitivity for detection of heavy metal ions and pesticide residues,a series of research works had been carried out based on the development of sensing materials and the construction of sensitive signal sensing strategy as follows:1.Construction of a novel electrochemical sensor based on furfural/reduced graphene oxide nanocomposite for detection of heavy metal ionsThe preparation of furfural/reduced graphene oxide nanocomposite（FF/RGO）was performed through a one-step high-pressure assisted hydrothermal treatment,which was recommended as a green,convenient,and efficient way.RGO not only served as the skeleton for furfural loading but also improved the conductivity of the composites.FF/RGO with large specific surface area and abundant oxygen-containing functional groups could provide more binding sites for the efficient adsorption of heavy metal ions due to the interaction between hydrophilic groups（-COOH,-OH and-CHO）and metal cations.Under optimal conditions,the developed sensor showed identifiable electrochemical response toward the heavy metal ions(Cd²⁺,Pb²⁺,Cu²⁺and Hg²⁺)separately and simultaneously.The detection limits for the simultaneous detection of the four heavy metal ions were 2 ng/m L,12 ng/m L,3 ng/m L and 20 ng/m L,respectively.In addition,the method was successfully used for the detection of heavy metal ions in cabbage and river water samples with good recoveries of 93.3%-106.0%,and the results exhibited satisfactory agreement with atomic absorption spectrometry.2.Construction of a novel photoelectrochemical sensor based on polythiophene derivative film for detection of chlorpyrifosThe functional monomer 2,5-Di-thiophen-2-yl-thiazolo[5,4-d]thiazole（S₂TTz）was synthesized,and then polythiophene derivative film with excellent photoelectrochemical property was successfully designed on the surface of glassy carbon electrode through electropolymerization.The related characterizations such as Scanning electron microscopy,H NMR spectroscopy and Ultraviolet-visible spectrum were utilized to verify the morphology and structure of PS₂TTz film,and the influence of electropolymerization parameters（scan rate and scan cycle）and the applied potential in photoelectrochemical reaction on the photoelectric properties of the synthesized polymer were studied.For the phenomenon that the photocurrent of PS₂TTz/GCE decreased with the addition of chlorpyrifos,X-ray photoelectron spectroscopy and Electrochemical impedance spectroscopy were employed to explore the possible mechanism during the sensing process,which confirmed that the interaction between chlorpyrifos and PS₂TTz would hinder the electron transfer on the electrode surface.Therefore,a signal-attenuated photoelectrochemistry sensing platform for chlorpyrifos detection was developed.Under the optimal conditions,the developed method displayed a linear range from 1.0μg/L to218.92μg/L and the detection limit was 0.36μg/L.In addition,satisfactory recoveries（100.33%-110.40%）were also obtained in the detection of actual cabbage samples.3.Construction of a photocatalytic-assisted electrochemical sensor based on nitrogen-doped carbon materials for detection of chlorpyrifosThe nitrogen-doped carbon material（M-NCM）with photocatalytic performance was synthesized by direct pyrolysis method of starch,melamine,nickel sulfate and manganese sulfate.The introduction of Ni and Mn had remarkable effect on improving the specific surface area and topography of M-NCM.Based on the competitive capture of hole（h⁺）on the valence band of M-NCM between methanol and chlorpyrifos,a photocatalytic-assisted electrochemical sensor for indirect quantitative detection of chlorpyrifos was constructed with the help of platinum nanoparticles.Under optimal conditions,the response current of Pt NPs/GCE toward methanol was found to be proportional to the chlorpyrifos concentration.The developed sensor displayed a linear range from 1μg/L to200μg/L and the detection limit was 0.62μg/L.In addition,the higher recoveries of chlorpyrifos were obtained in the vegetable samples.