| Nitrite is extensively used as food additive and corrosion inhibitor due to the effect of color-preserving and corrosion prevention.However,it can promote the irreversible oxidization of hemoglobin to methemoglobin,thereby reducing the oxygen transport capability of blood.In addition,it can react with amines and leads to the generation of carcinogenic N-nitrosamines in stomach,which causes cancer and hypertension.Therefore,it is very necessary to measure and control the content of nitrite.In recent years,numerous techniques,including spectrophotometry,catalytic spectrophotometry,fluorescence analysis,chromatography and electrochemical methods,have been developed to determine nitrite.Among these methods,electrochemical method is widely used owing to the specific advantages such as high sensitivity,fast response and low cost.However,the electrochemical properties of nitrite based on on bare glass carbon electrodes are still limited due to their high over potentials and poor sensitivity.Hence,in order to improve the electrochemical performances,great attentions have been attracted on modified different nanomaterials on electrodes.In this thesis,graphene?rGO?,as a base material,modified with molybdenum disulfide?MoS2?,carbon nanotubes?CNTs?and metal oxide to synthesize graphene composite materials.XRD,SEM,TEM,EDS and XPS were introduced to characterize the microtopography and elementary compositions.Meanwhile,nitrite electrochemical sensors were fabricated by modifying graphene composite materials on glassy carbon electrode to explore the electrochemical responses towards nitrite.The measured results are summarized as follows:?1?The Mo S2/rGO heterostructures were synthesized by a modified hydrothermal method,and the characterization analysis shows that the introduction of rGO inhibits the aggregation of MoS2 layer and promots electron transport in electrochemical reaction.The electrochemical test results indicated that the nitrite electrochemical sensor based on MoS2/rGO/GCE shows good electrochemical performance,the sensitivity of the nitrite electrochemical sensor can reach to 0.46?A·?M-1·cm-2 in 0.2–4800?M with a detection limit of 0.17?M,and the sensor performs good selectivity,repeatability and practicability.?2?Fe2O3 nanoparticles were synthesized by hydrothermal method,and then the Fe2O3-Mo S2/rGO nanostructure was successfully synthesized by Fe2O3doped with MoS2/rGO,and the result shows that the Fe2O3 nanoparticles are evenly dispersed on the surface of Mo S2.According to the results of electrochemical tests,the Fe2O3-MoS2/rGO composite material as an electrode modified material,has strong ability of electric catalytic oxidation for nitrite.For the nitrite electrochemical sensor based on Fe2O3-MoS2/rGO/GCE,the linear detection range can be up to 1-9830?M,the detection limit is as low as0.2?M?S/N=3?,and it shows a great selectivity and an excellent ability of anti-interference.?3?The Co3O4-CNTs/rGO composites were synthesized by one-step annealing process using CNTs/GO composites as the support material for the cobalt-centered metal-organic framework ZIF-67.First,the mass ratio of graphene oxide to carbon nanotubes was changed to study the catalytic properties of CNTs/rGO to nitrite.It was found that the best catalytic effect was achieved when the mass ratio of CNTs to GO was 1:1.Then the mass percentage of Co3O4 was controlled to study the catalytic performance to nitrite,and it was found that when the mass percentage of Co3O4 was 53.3 wt%,the Co3O4-CNTs/rGO/GCE sensor exhibited excellent electrocatalytic performance for nitrite.The current response can be divided into two linear intervals:one from 0.1?M to 8 mM in lower range,the sensitivity is 0.408?A·?M-1·cm-2 with a detection limit of 0.016?M;and the other from 8 mM to 56 mM in higher range,the sensitivity is 0.153?A·?M-1·cm-2.At the same time,the Co3O4-CNTs/rGO/GCE sensor also has good selectivity and strong anti-interference ability,and can effectively detect actual samples. |
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