A Novel 2D Hybrid Nanomaterials For Selectively Detection Of NO₂ And SO₂

The detection of hazardous gases in the atmosphere where humen lived has been a hot research field.In general,the commercial sensing material used for gas sensor device is metal oxide semiconductor which is usually operate under high temperature.The work condition raised the running cost for gas sensors so that a certain extent limits the popularization and development of gas detection.Simultaneously,it is difficult to detect the low concentration gas in the environment owing to the high detection limit.As a hot candidate for electronics,energy and sensing technologies,the graphene have a unique structure and properties.Although,the absence of a direct band gap seriously limited the application in such areas.In recent years,as a new type of free metal semiconductor material,graphite carbon nitride(g-C3N4)has a suitable band gap and become the focus of the field of photocatalysis.Therefore,the g-C3N4 have great application potential in electrical gas sensor.The g-C3N4/GO composite paper chip was fabricated through the charge attraction between protonated g-C3N4 and graphene oxide which contain the carboxy group.The hybrids was characterized through SEM,TEM,XRD,PL and UV-vis.The result of characterization show that g-C3N4/rGO composite possessed van der Waals heterostructures and a large surface which advantageous to electron hole separation.The pyridine is a structure that have a absroption to electrophilic gas.The g-C3N4/rGO hybrids had a photocurrent under visible(?420 nm)and UV(365 nm)irradiation which proved the composite has obvious semiconductor photoelectric properties.A novel 2D van der Waals stacking hybrid was achieved to selectively detect both to NO2 and SO2 gas with high sensitivity at room temperature.Without light irradiation,the 2D sensor also showed good selectivity for NO2 against SO2,Cl2,NH3,toluene,ethyl acetate and hexane,which exhibited a p-type semiconducting behavior with low detection limit of 0.1 ppm N02.The response and restoring time is 138 s and 318 s,respectively.The hybrid materials could sensor to 20-800 ppm SO2 under visible light.However,the 2D sensor showed n-type semiconducting behavior which could detect a SO2 concentration as low as 2 ppm under UV light irradiation.The mechanism of g-C3N4/rGO composite paper chip sensor to low concentration gas was discussed with following aspects.1)The pyridine N that originate from g-C3N4 is propitious to absorption NO2 and SO2 gas.2)The p-n junction between g-C3N4 and rGO sheets could promote the transmission of electrons and holes.3)The paper substrate may contribute to the enhanced sensitivity of the g-C3N4/rGO sensor,because the cellulose network provides a highly porous structure to support the lamellar-like g-C3N4/rGO nanostructure.Furthermore,the p-type 2D sensor convert to n-type semiconductor under light irradiation.The electrons between SO2 molecules and g-C3N4/rGO nanosheets would be easy owning to the photelectrons,thus achieve the detection of low concentration of SO2.