| Nitrite is one of the intermediate product of the nitrogen cycle,widely exists in soil,natural water and food which are closely related to life.Nitrite entered human body by the food chain can not only combine with hemoglobin or low iron oxide red protein generated methemoglobin which can cause anoxia,it also can react with different amine in the gastric juice to produce carcinogenic nitrosamines resulting the canceration of digestive organs.In addition,a lot kinds of nitrogen in the air pollutants can converted to nitrite.Therefore,simple and rapid quantitative analysis of nitrite is of great importance.Methods to detect nitrite in wastewater at present are mainly the N-(1-naphthyl)-amine light method,uv spectrophotometry,oscillographic polarography,ion chromatography and electrocatalytic method.Among them,the electrocatalytic method is accurate,simple,low cost,etc.The pollution hazard,treatment and detection methods of nitrite in waste water have been studied in our work.The as-prepared composite materials Fe3O4-MoS2?TOSC-MoS2 and PANI-MoS2 both show excellent electrocatalytic activity for nitrite and can be used to determine nitrite concentration in different linear ranges.This method is simple and accurate and has strong practical significance.The main results of our work are as follows:(1)Fe3O4-MoS2,TOSC(TEMPO oxidized straw cellulose)-MoS2 and PANI-MoS2 nanocomposite materials were prepared and the three materials were characterized,respectively.High-resolution transmission electron microscopy(HRTEM)results show the Fe3O4 nanospheres disperse well on the MoS2 nanoflake.The presence of characteristic of Fe-O and Mo-O vibrations in the Fe3O4/MoS2 FT-IR spectra indicate the Fe3O4 has been composited with MoS2 successfully.High resolution of O 1s spectrum shows the presence of three types of oxygen including lattice oxygen,hydroxyl groups and S-OH.Scanning electron microscopy(SEM)and transmission electron microscopy(TEM)images show the TOSC as a carbon nanotube-like structure and edged MoS2 grows on the TOSC substrate.Fourier transform infrared spectroscopy(FT-IR)and X-ray diffraction(XRD)analysis confirm that TOSC and MoS2 have successfully composited.Fourier transform infrared spectroscopy(FT-IR)and X-ray diffraction(XRD)results indicated that the PANI and MoS2 had been successfully composited.(2)A Fe3O4/MoS2 nanostructure was obtained by a facile hydrothermal method.The Fe3O4/MoS2 nanostructure modified glassy carbon electrode(GCE)has the best electrochemical activity when compared with bare,Fe3O4 or MoS2 modified GCE.The amperometric response result indicates the Fe3O4/MoS2 modified GCE can be used to determine nitrite concentration in a wide linear range of 1.0-2630?M(R2=0.998)with a detection limit of 0.5?M.(3)A TEMPO oxidized straw cellulose/molybdenum sulfide(TOSC-MoS2)composite has been synthesized via a hydrothermal method.The TOSC-MoS2 modified glassy carbon electrode(GCE)is used as a simple and non-enzymatic electochemical sensor.Cyclic Voltammetry(CV)result shows TOSC-MoS2 has excellent electrocatalytic activity for the oxidation of nitrite.The amperometric response result indicates the TOSC-MoS2 modified GCE can be used to determine nitrite concentration in a wide linear range of 6.0-3140 and 3140-4200 ?M with a detection limit of 2.0?M.The proposed sensor has good anti-interference property.(4)A polyaniline/molybdenum sulfide(PANI-MoS2)nanocomposite was synthesized via a hydrothermal method and in situ polymerization,respectively.CV result showed the PANI-0.1gMoS2 modified glassy carbon electrode(GCE)exhibited excellent electrochemical activity in a o.1M PBS compared to the MoS2,PANI and other PANI-MoS2 composites modified GCE.CV result also confirmed nitrite could be oxidized by the PANI-0.1gMoS2 in a pH 5.0 PBS.The amperometric response result indicated the PANI-0.1gMoS2 modified GCE could be used to determine nitrite concentration in a wide linear range of 4.0 and 4834 ?M with a detection limit of 1.5 ?M. |
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