Preparation Of Mo-based Nanocomposite And Its Application In Electrochemical Detection Of Nitrite

It is well known that nitrites are widely present in food,drinking water and environmental systems.However,excessive nitrite is not only harmful to the environment,but also to human health.The common detection methods of nitrite include chromatography,spectrophotometry,electrochemical method,chemiluminescence method and atomic absorption spectrometry.Among them,the electrochemical method is widely used because of its high sensitivity,fast speed and low cost.Due to the fact that the bare electrode and the flat electrode are easily damaged by the electroactive substances,the electrodes modified with different nanomaterials have been rapidly developed and applied to the detection of nitrite.Molybdenum material is characterized by its large specific surface area,small size,strong electrical conductivity and high chemical stability,and then through the composite metal semiconductor materials to improve the electrochemical catalytic performance,so as to establish a better performance of electrochemical sensor.In this paper,three kinds of nanocomposites based on molybdenum compounds were prepared,namely,spherical molybdenum trioxide-zinc oxide(MoO3-ZnO),molybdenum disulfide-nickel sulfide(MoS2-NiS)and flower-like zinc sulfide-molybdenum disulfide(ZnS-MoS2).The morphology and structure of the composites were analyzed by scanning electron microscopy(SEM),X-ray photoelectron spectroscopy(XPS),X-ray diffraction(XRD)and transmission electron microscopy(TEM).Then,electrochemical methods such as cyclic voltammetry,amperometric method,differential pulse voltammetry and AC impedance were used to test the nitrite detection performance of the sensor constructed in this paper,and the influence of different experimental parameters on the detection was studied.Finally,the detection effect of the nitrite sensor constructed in this paper on actual samples was explored.(1)Spherical MoO3-ZnO composite was prepared by hydrothermal synthesis and calcination,and characterized by SEM,XRD and TEM.It was proved that MoO3-ZnO was successfully embedded on the surface of zinc oxide.The electrochemical activity of the composite and the detection performance of the nitrite sensor constructed were studied by electrochemical experiments.The results show that the synergistic effect of MoO3 and ZnO greatly enhances the electrocatalytic performance of the composite.After the optimum experimental parameters were determined,the linear range of the sensor for nitrite detection was 0.05?6.0 mM,the correlation coefficient was 0.998,the sensitivity was 0.330 A·(mol·L-1)-1·cm-2,and the detection limit(S/N=3)was 0.016 mM.The electrochemical sensor constructed by this complex has good selectivity,stability and reproducibility in the detection of nitrite ions,and the actual sample detection results are good.(2)MoS2-NiS nanocomposite with heterogeneous structure was prepared by one-step hydrothermal synthesis.The results showed that the composite was successfully prepared by TEM and XRD.Then the nitrite detection performance of the electrochemical sensor constructed by the composite material was studied by cyclic voltammetry.The experimental results show that the electrocatalytic performance of MoS2-NiS is significantly higher than that of monomer MoS2 and NiS.By potentiostatic method,the response current and nitrite concentration of this sensor were linear in the range of 0.9?1210.0 ?M,the correlation coefficient was 0.999,the sensitivity was 0.281 A·(mol·L-1)-1·cm-2,and the detection limit(S/N=3)was 0.25 ?M.In addition,the nitrite sensor assembled by the composite material has excellent selectivity,stability and repeatability,which can be applied to the analysis of actual samples.(3)The flower-like ZnS-MoS2 composite was prepared by ultrasound-assisted synthesis and hydrothermal synthesis.The composite was characterized by SEM,XRD and TEM,and it was proved that MoS2 was successfully grown on the surface of ZnS.Then the electrochemical properties of the composite were studied by cyclic voltammetry and amperometry.The experimental results show that the electrochemical activity of the composite is better than that of monomer material.The nitrite sensor constructed by this compound has a good linear relationship in the range of 2.44?252.63 ?M and 252.63?2225.0?M,and the correlation coefficients are 0.999.The sensitivity was 17.729 A·(mol·L-1)-1,cm-2 and 0.115 A·(mol·L-1)-1·cm-2,respectively,and the detection limit(S/N=3)was 0.78 ?M.The results showed good selectivity,stability and reproducibility,which could effectively analyze the concentration of nitrous acid ions in the river water.