Research On Detection Of Malachite Green By Carbon-based Electrochemical Sensor

Malachite green is a commonly used dye in industry,and it was also used in aquaculture as an efficient bactericide in the last century.However,it has been found that malachite green can cause some health problems,such as carcinogenesis and human defects.Many countries and organizations list it as a banned substance for food,especially for aquaculture.However,malachite green is still illegally used in edible fish breeding industry because it’s cheap and efficient.Therefore,it is necessary to detect malachite green content in aquatic products efficiently,economically and quickly to reduce food safety risks.Among all kinds of analytical methods,electrochemistry provides a simple and robust analytical method,which is simpler,faster,more sensitive and more efficient than the traditional analytical technology relying on large instruments.And the rapid development of nanomaterials has also promoted the research of electrochemical detection of pollutants.This paper mainly focuses on the application of different nanomaterials in the electrochemical detection of malachite green.Discusses the treatment and synthesis of carbon-based nanomaterials,and analyzes and looks forward to the development prospect of electrochemical sensors.The experiment of this paper includes two parts.The first part is to select conductive carbon black with high conductivity,prepare two kinds of carbon black by hydrophilic treatment,and then test the sensing performance of the two kinds of carbon black to malachite green;In the second part,we synthesized high-content nitrogen-doped carbon nanosheets and tested their sensing performance:1.Two kinds of conductive carbon blacks of different brands were selected as sensor materials.Super conductive carbon Ketjen Black（KB）from Japan Lion King Co.,Ltd.Super P carbon black（SPB）from France IMERYS Co.,Ltd.And two kinds of hydrophilic carbon blacks were prepared by hydrophilic treatment,namely hydrophilic Ketjen Black（HKB）and hydrophilic Super P carbon black（HSPB）.Then,the physical and chemical properties of the two carbon black materials were characterized,including the surface morphology characteristics determined by field emission scanning electron microscope（FESEM）,the chemical structure and functional groups of the two carbon blacks analyzed by Fourier Transform Infrared Spectroscopy（FT-IR）,the electrochemical properties of these materials were analyzed by cyclic voltammetry（CV）,differential pulse voltammetry（DPV）and electrochemical impedance spectroscopy（EIS）,and the electrical sensor performance of the materials was determined.The results show that some oxygen elements and oxygen-containing groups exist in carbon black before hydrophilic treatment,and they exist in the form of-OH and C=O.Among the two kinds of carbon black,KB has the best conductivity and the best electrochemical sensing performance for malachite green,and pH,enrichment time and material loading have obvious effects on the response of DPV.The most suitable test conditions are:pH 7.0,enrichment time of 60min and loading volume of 6μL.Under the optimum conditions,the linear range of malachite green detection is 1～10μmol/L,and the detection limit is 57.18 nmol/L.The experimental test of tap water recovery by adding standard has no significant effect on the determination accuracy,and the sensor can be used for the determination of tap water.And it has good selectivity for Cl^-、SO₄^2-、Ca²⁺、Mg²⁺.2.Conductive polyaniline（PANI）and Urea（U）were mixed as precursors,and high-content nitrogen-doped carbon nanosheets were obtained by one-step method in nitrogen atmosphere,in which the addition of polyaniline improved the conductivity to some extent.In this part,we studied the influence of polyaniline content in the precursor on the final result.In addition,we studied the physical and chemical properties of the materials,and used FESEM to characterize the morphology,and FT-IR to analyze the chemical structure and composition.In order to measure the electrochemical sensing performance of materials,the electrochemical methods of DPV,CV and EIS are used.The analysis results show that the existence of polyaniline changes the properties and structure of the material,which can effectively improve the conductivity of the material,but when the content of polyaniline in the current flooding body is too high,the conductivity becomes worse.The best precursor composition is 20 g urea and 1.00 g polyaniline,and the most suitable test conditions are as follows:pH 6.5,accumulation time 60 min,loading volume 2μL.Under the optimum conditions,the linear range of malachite green detection is 1～10μmol/L,and the detection limit is 13.2 nmol/L.The recovery experiment of tap water shows that there is no significant influence on the determination accuracy,and the sensor can be used for the determination of tap water.It has good selectivity for Cl^-、SO₄^2-、Ca²⁺、Mg²⁺,sunset yellow and methyl orange.3.PCN/G composites were prepared by solvent-mediated self-assembly of carbon nitride nanosheets and graphene.The chemical structure,electrical conductivity and detection ability of the composites were analyzed by FT-IR,CV,EIS and DPV,and the selectivity of the materials to malachite green was studied.The results are consistent with the expectation.The addition of graphene can increase the conductivity of the material,and carbon nitride nanosheets show good affinity for malachite green.Among them,the best material is PCN/G-3,a self-assembled material made of carbon nitride and graphene in a ratio of 1:2.The most suitable test conditions are as follows:buffer pH=6.0,enrichment time 30 min,loading volume 2μL.Under this condition,the linear range of malachite green detection is 2～10μmol/L,and the detection limit is 61.5 nmol/L.Through practical samples and interference research,the sensor can provide simple,portable,fast and accurate detection,and also has certain anti-interference ability for metal salts such as sodium chloride and sunset yellow,so it can be used as a sensor for electrochemical detection of malachite green,and is expected to become a detection scheme for malachite green in water.To sum up,the above three kinds of materials can be used for the detection of malachite green,but from the perspective of sensitivity and selectivity,nitrogen-doped carbon nanosheets have better performance as sensors and are more suitable for the detection of low content of malachite green;the commercial conductive carbon black material is cheaper and easier to obtain,which has more application value for high content situations;self-assembled materials have a large space for improvement in sensing performance.