| Graphene quantum dots?GQDs?are graphene sheets smaller than 20 nm,which present unique optical and electronic properties due to their quantum confinement and edge effects.Recently,GQDs as a typical carbon nanomaterials have received considerable attention because of its attractive prospects in fluorescent probe,photocatalysis,biomedical imaging,electrochemical detection,drug transport and sensor etc.In this thesis,we introduced the preparations method,mechanism and potential applications of GQDs in detail.The GQDs and GQDs-metal oxide composites were prepared via hydrothermal method,the gas sensing properties of GQDs-metal oxide composites were studied emphatically.We prepared GQDs-ZnFe2O4 composites,GQDs-ZnO composites and GQDs-MoO3 composites via hydrothermal method.The morphology of the composites was observed by SEM,TEM and HRTEM,the as-prepared were characterized by XRD,TG-DSC,FT-IR,Raman,XPS and N2 adsorbtion-desorption,respectively.The effect of GQDs content on the gas-sensing responses and the gas-sensing selectivity of the GQDs-metal oxide composites was investigated.The gas sensitivity test results showed that the addition of GQDs reduced the optimum operating temperature while while increasing its sensitivity to one or more gases.For example,the responses of the sensor based on GQDs-ZnFe2O4?S-15?composite to 1000 ppm acetone reached 13.31 at room temperature,and the lowest concentration of acetone could be detected was 5 ppm.Responses based on GQDs-ZnO?S-10?showed higher sensitivity and better stability than that based on pure ZnO at room temperature,and the highest sensitivity was 642,this sensor could detect acetic acid with the concentration of as low as 1 ppm.The sensor based on GQDs-MoO3?S-6?showed highest sensing performance and selectivity to trimethylamine at 230?.The highest sensitivity reached 74.08 towards 1000 ppm trimethylamine which was 13.9 times than that of pure MoO3,and the lowest detectable trimethylamine concentration was1 ppm... |
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