Construction And Application Of Electrochemical Sensor Based On Single-layer Tungsten Disulfide-carboxylated Multi-walled Carbon Nanotubes

Objective:P-nitroaniline（PNA）is an aniline compound and is widely used in industrial fields,mainly as an intermediate for azo dyes,pesticides and veterinary drugs.However,the mother liquor and washing wastewater in the PNA production process are directly discharged into river water bodies,causing serious pollution to the water environment.Therefore,it is particularly important to establish a method for rapid detection of PNA.Electrochemical analysis methods have received extensive attention in the field of analysis due to their sensitivity,efficiency,and speed.This study aims to use the electrochemical properties of single-layer tungsten disulfide（WS₂）and multi-walled carbon nanotubes（MWCNTs）to construct WS₂/CMWCNTs composite materials for the detection of PNA,and the established method can be applied to the detection of actual samples of PNA.It provides a quick and sensitive method for detecting PNA in water.Methods:（1）The glassy carbon electrode was polished,cleaned,dried,and other pretreatments.The multi-walled carbon nanotubes were modified by the mixed acid method,and then WS₂ and CMWCNTs were mixed by ultrasound to prepare WS₂/CMWCNTs composite material,And then use a pipette to drip the prepared composite material on the glassy carbon electrode and let it dry naturally,which was recorded as WS₂/CMWCNTs/GCE.（2）Using scanning electron microscopy,cyclic voltammetry and electrochemistry Impedance spectroscopy,etc.to characterize the modified material,observe its morphology and study its electrochemical performance.（3）Using a three-electrode system,using WS₂/CMWCNTs/GCE as the working electrode,saturated calomel electrode（SCE）as the reference electrode,platinum electrode（Pt）as the counter electrode,use cyclic voltammetry to detect PNA,with a scan rate of 100m V·s^-1,a starting potential of-1.1V,and a termination potential of0.4V as the measurement parameters,to explore the electrochemical behavior of PNA on WS₂/CMWCNTs/GCE.Establish an electrochemical analysis method for rapid determination of PNA by optimizing experimental conditions such as the amount of modifiers,the selection of supporting electrolyte,the p H of phosphate buffer（PBS）and the scanning rate.（4）And through a series of method performance indicators such as linear range,detection limit,repeatability,stability and interference experiments,it was verified the method,which was applied to the detection of actual wastewater samples.Result:（1）The carboxylated carbon nanotubes prepared by the mixed acid method are combined with a single layer of tungsten disulfide through ultrasound,and the suspension made is not only uniform but also dispersible.（2）After analyzing the characterization results of the modified electrode,the scanning electron microscope results showed that the single-layer tungsten disulfide morphology was flake-like,the acidified multi-walled carbon nanotubes were oxidized relatively uniformly,and the WS₂/CMWCNTs composite film could be well combined together;the cyclic voltammetry curve shows that compared with the bare electrode,the peak current of the WS₂/CMWCNTs composite film is increased by 100μA,indicating that the redox capacity is greatly enhanced;The resistance values of GCE,WS₂/GCE,CMWCNTs/GCE and WS₂/CMWCNTs/GCE are calculated by electrochemical impedance spectroscopy fitting,which are respectively 628?,251?,11?,4?,and the resistance decreases in turn,which also indicates the modified The composite material WS₂/CMWCNTs/GCE can effectively reduce the resistance and accelerate the electron transfer rate,which is also consistent with the CV results.（3）The cyclic voltammetry curve shows that in the PBS of p H 7.0,PNA has an obvious reduction peak at-0.7V,and it is irreversible.The optimal experimental conditions were discussed as follows:the dosage of modifier is 4μL,the supporting electrolyte is phosphate buffered saline（PBS）,the p H of the supporting electrolyte is 7 and the best scanning rate is 100m V·s^-1.（4）After optimization of the conditions,the peak current value and the PNA concentration are linear in the range of 0～500μmol·L^-1,the correlation coefficient is0.9961,the detection limit（3s/k）is 0.63μmol·L^-1,the electrode The repeatability and reproducibility results show that the RSD of both are less than 5%.The interference experiment results show that the coexisting organics and common ions and isomers interfere.The WS₂/CMWCNTs composite membrane has a strong selectivity to nitroaniline.The constructed modified electrode was used to detect wastewater.The recovery rate of standard addition was 92.8%～102.7%,and the relative standard deviation（n=6）was less than 5%.Conclusion:（1）By introducing carboxyl groups on the surface of multi-walled carbon nanotubes,it can not only maintain its original good properties,but also improve the binding ability to ions,and the multi-walled carbon nanotubes introduced with carboxyl groups can be a single-layer tungsten disulfide supporting carriers and more binding sites are provided,and the modified materials are characterized by a series of methods.The results show that the constructed electrochemical sensor is relatively successful.（2）Using the constructed WS₂/CMWCNTs/GCE electrochemical sensor to detect the actual sample,the results show that the electrochemical sensor has a significant catalytic effect on the reduction characteristics of PNA.The method is further confirmed by linear range,detection limit,repeatability and interference experiments.The established new method is used to determine the p-nitroaniline in wastewater,and the results are satisfactory.It shows that the sensor has stable performance,good reproducibility,and strong anti-interference ability,which can provide new methods and ideas for the rapid detection of p-nitroaniline.