Preparation Of Caobon-based Nanocomposite Materials And Its Electrochemical Detection Of Nitrite

Nitrite is an inorganic compound with various industrial and medicinal applications.It is widely used as preservative in food,and nitrite finds application as an antidote for cyanide and hydrogen sulfide poisoning.People are exposed to nitrite through water,air and soil.Nitrite has been declared as classified hazardous species due to its toxicity to human.At present,Analytical techniques like spectrophotometry,chromatography,capillary electrophoresis and chemiluminescence etc were used for sensing of nitrite.These methods mostly have some disadvantages such as high cost,long time and large error.In comparison,electrochemical method has the advantages of high detection sensitivity,fast analysis speed and strong anti-interference ability.However,constructing a high performance electrochemical sensor and searching for suitable materials to modify the electrodes in sensing nitrite are urgent problems to be faced.Carbon materials have wide application in electrocatalysis due to excellent physicochemical propertyIn this paper,three carbon-based nanocomposite materials were prepared,named as tin disulfide/tin oxide @carbon spheres(SnS2/SnO2@CSs),zinc oxide/zinc@pitaya-derived biochar(ZnO/Zn@PBC)and ZIF-67/bacterial cellulose(ZIF-67/BC).The morphology,size and elementary composition were studied by various characterization techniques,such as SEM,XPS etc.Electrocatalysis and its mechanism in sensing nitrite were studied by cyclic voltammetry,AC impedance method,amperometric method and other electrochemical techniques,the detection effect under different factors were also explored.The accuracy was tested in actual samples(1)The carbon spheres and the composite precursors were synthesized by two-step hydrothermal method,and then the SnS2/SnO2@CSs nanocomposites were synthesized by high temperature annealing.The characterization results show that tin disulfide and tin oxide are successfully loaded on the surface of the carbon spheres.The electrochemical experiments show that the electrochemical activity of the nanocomposite materials is better than that of the monomer.The amperometric response results indicated the SnS2/SnO2@CSs modified GC electrode could be used to determine nitrite concentration in wide linear ranges of 0.25?262 ?M and 262?1278?M,and the sensitivities are 419 and 232 mA M-1 cm-1 respectively,the detection limit is 2.45?M.In addition,SnS2/SnO2@CSs has high sensitivity and low detection limit and can be used for tap water or lake water detection.(2)Zinc oxide/zinc@pitaya-derived biochar(ZnO/Zn@PBC)were synthesized by carbonization at high temperature after pretreatment of pitaya peel and impregnation in zn-ion aqueous solution.Many characterization results show that ZnO and Zn nanoparticle grow on the surface of biochar.The results of electrochemical experiments show that the synergistic effect of ZnO/Zn and PBC can improve the electrocatalytic oxidation ability of the composites.The sensor can be used to detect nitrite in wide linear range of 0.01?5.0mM,the sensitivities and the detection limit are 147 mA M-1 cm-1 and 3.12 ?M,respectively.The ZnO/Zn@PBC electrochemical sensor has excellent selectivity and stability and can be used for actual sample dection.(3)The freeze-dried bacterial cellulose was impregnated with zinc nitrate and 2-methylimidazole,aged for 24 hours and then carbonized at high temperature to synthesize ZIF-67/BC composites,and a non-enzymatic nitrite electrochemical sensor was successfully constructed.The characterization results confirm that ZIF-67 has polyhedral structure,which is embedded in bacterial cellulose.The synergistic effect of the ZIF-67 and BC further improved the electrochemical activity.ZIF-67/BC modified GC electrode could be used to determine nitrite concentration in wide linear ranges of 0.5?100 ?M and 100?1300?M,and the sensitivities are 180 and 970 mA M-1 cm-1 respectively,the detection limit is 1.34 ?M.The nitrite sensor constructed by the composite material has strong anti-interference ability,high detection accuracy and good repeatability.