The Preparation Of Electrochemical Sensors Based On Carbon Materials And Their Performance In Detecting Nitrite In Water

As one of the most promising technologies for detecting nitrite in the environment,electrochemical sensor has many advantages,such as simple operation,rapid analysis,high detection selectivity and sensitivity.However,designing materials with better performance to modify the electrodes and construct a highly efficient electrochemical sensor to achieve accurate detection of nitrite is still an urgent problem to be solved.Carbonaceous materials have excellent properties such as large specific surface area,small size,strong electrical conductivity and good chemical stability,and have received extensive attention in the field of electrocatalytic materials.In this paper,three carbon-based composite materials were prepared,namely bacterial cellulose/graphene oxide(BC-GO),gold-molybdenum sulfide-carbon nanotubes(Au-MoS2-MCNTs)and cobalt sulfide-molybdenum sulfide/nitrogen-doped lignin(CoS2-MoS2/NLG).The morphology and structure of the composites were studied by various characterization methods.The electrochemical activity of the composite modified electrode and the electrocatalytic oxidation performance of nitrite were studied by cyclic voltammetry,amperometric method,differential pulse voltammetry,AC impedance method and other electrochemical methods,the influencing factors and detection range of nitrite were also studied.(1)Bacterial cellulose/graphene oxide(BC-GO)nanocomposites were prepared by an ultrasonic mixing method.The characterization results show that bacterial cellulose is successfully embedded in the graphene oxide layers.The results of electrochemical experiments show that the BC-GO composite modified electrode has good electrochemical activity.The nitrite concentration can be detected in a wide linear range(0.5-4590 ?M).The detection limit and sensitivity are 0.2 ?M and 527.35 ?A ?cm-2,respectively.In addition,the BC-GO nitrite sensor has good anti-interference and stability and can be used for actual sample detection.(2)MoS2-MCNTS composites were prepared by a hydrothermal method.Gold nanoparticles were deposited on the surface of MoS2-MCNTs by electrodeposition to obtain Au-MoS2-MCNTS composites.It has been confirmed by various characterization methods that Au nanoparticles grows on the surface of MoS2-MCNTs.Then Au-MoS2-MCNTs electrochemical sensor was successfully constructed to detect nitrite.The electrochemical experiments results show that the synergistic effect of MCNTs,MoS2 and Au nanoparticles makes the Au-MoS2-MCNTs sensor have good electrocatalytic activity.The sensor shows good electrocatalytic oxidation of nitrite and can be used to detect nitrite in a wide linear range(12-2100 ?M and 2100-6500 ?M),the corresponding sensitivities are 1.734 and 6.735 mA?M-1 cm-2,respectively,and the detection limit is 4.0 ?M.The Au-MoS2-MCNTs electrochemical sensor can also be used for the determination of nitrite in drinking water and river water,and has the advantages of high sensitivity,good selectivity and high accuracy.(3)Nitrogen-doped lignin(NLG)was prepared by TEMPO oxidation followed with a pyrolysis method.The novel binary metal sulfide complex/nitrogen-doped lignin(CoS2-MoS2/NLG)was synthesized by a hydrothermal route.The characterization results confirm that the binary metal sulfide successfully grow on the surface of the nitrogen-doped lignin(NLG)carbon substrate.A simple nitrite electrochemical sensor was constructed with the CoS2-MoS2/NLG composites.The synergistic effect of CoS2 and MoS2 and the combination of NLG carbon substrates further improve the electrochemical activity of the CoS2-MoS2/NLG composite modified electrode,and the nitrite can be detected in a wide linear range(0.5-5160 ?M)with a detection limit of 0.2 ?M.The composite modified electrode has many advantages,such as high sensitivity,excellent selectivity and stability.