The Preparation Of NiGa₂O₄ Nanomaterials And Gas Sensing Properties Research

NiGa₂O₄ is widely used in photocatalysis,photoluminescence and gas sensors due to its unique physical and chemical properties.In this paper,NiGa₂O₄ was prepared by four methods and its gas-sensing properties were discussed.In chapter two,the precursor of NiGa₂O₄ nanomaterials were prepared by co-precipitation method,then the precursor were calcined at 400,500,600 and 700℃ for 6 h in air.The precursor of NiGa₂O₄ nanomaterials was characterizated by TG-DSC.It was found that the sensor based on NiGa₂O₄ nanomaterial calcined at 600℃ exhibited good response and good selectivity to trimethylamine vapor and ethanol vapor at room temperature and 413 ℃,respectively.The NiGa₂O₄nanomaterial calcined at 600℃ were characterized by XRD,SEM,N₂ adsorption-desorption,FTIR,XPS and UV-Vis.The results showed that the sensor based on NiGa₂O₄ nanomaterial calcined at600℃ showed best response to trimethylamine and ethanol at room temperature（43）and 413 ℃（43）,respectively.The detection limits were all 10 ppm.The responses of the sensor based on NiGa₂O₄nanomaterial calcined at 600℃ to 10 ppm trimethylamine and 10 ppm ethanol were 1.6 and 1.2,respectively.In chapter three,Graphene-NiGa₂O₄（G-NiGa₂O₄）composites with different graphene content（0,0.1,0.5,1,2 and 3 wt%）were successfully prepared by hydrothermal method at 180°C for 8 h.The G-Ni Ga₂O₄ composites were characterized by XRD,SEM,BET adsorption-desorption,TG-DSC,Raman,FTIR and UV-Vis absorption spectrum,respectively.The gas sensing properties of as-prepared composite materials were investigated.The results showed that the sensor based on 2 wt%Graphene-Ni Ga₂O₄ composite showed best response to trimethylamine vapor in all sensors investigated in this paper.The response of the sensor base on 2 wt%G-Ni Ga₂O₄ composites to 1000ppm trimethylamine vapor at the room temperature is as high as 100.67,and the response time and recovery time were 320 s and 6 s,respectively.Furthermore,the detection limit could reach to 0.01ppm and the response to 0.01 ppm was 1.4 at room temperature,the response time and recovery time for 0.01 ppm were 1.5 s and 2 s,respectively.In chapter four,the precursor of NiGa₂O₄ nanomaterials were prepared by electrospinning method,the precursor were calcined at 500,600,700 and 800℃ in air,then the NiGa₂O₄nanomaterials were obtained.The precursor of NiGa₂O₄ nanomaterials was characterizated by TG-DSC.The as-prepared samples were characterized by XRD,SEM,N₂ adsorption-desorption,FTIR,XPS and UV-Vis DRS,respectively.The gas-sensing properties of NiGa₂O₄ nanomaterials were investigated.It was found that the sensor based on NiGa₂O₄ nanomaterial（600℃,2 h）exhibited good response and good selectivity to trimethylamine vapor at room temperature.When operating at room temperature,the responses of the sensor based on NiGa₂O₄ nanomaterial（600℃,2 h）to 1000 ppm trimethylamine reached 19,the response time and the recovery time for 1000 ppm trimethylamine was 14 s and 2 s.The detection limits for trimethylamine was 1 ppm,The response time and the recovery time for 1 ppm trimethylamine was 1s and 1 s.In chapter five,the precursor of NiGa₂O₄ nanomaterials were prepared by sol-gel method,the precursor were calcined at 700℃ for 2 h in air,then the NiGa₂O₄ nanomaterials were obtained.The sensing properties of NiGa₂O₄ nanomaterials by different complexing agent（TEA,citric acid and glycine）were discussed.The precursor was analyzed by TG-DSC.The as-prepared samples were characterized by XRD,SEM,N₂ adsorption-desorption,FTIR,XPS and UV-Vis DRS,respectively.The results showed that the sensors based on NiGa₂O₄ nanomaterials（TEA,citric acid and glycine）exhibited good response and good selectivity to ethanol vapor at 270℃,among them,the the sensors based on NiGa₂O₄ nanomaterials（TEA）showed the most response（63）.The response time for 1000 ppm ethanol were 55,27 and 2 s,respectively,The response time for 1000 ppm ethanol were55,27 and 2 s,respectively,and the recovery time for 1000 ppm ethanol were 10,9 and 20 s,respectively.The detection limits for ethanol were 0.5,100 and 0.1 ppm.