Preparation Of Modified G-C₃N₄ Nanosheets And Its Photoelectric Sensing And Photocatalytic Properties

Since Liu and Cohen discovered carbon nitrides,they have been deeply studied.In recent ten years,graphite phase carbon nitride(g-C₃N₄)has developed rapidly.Carbon nitride has excellent chemical stability,ultra-high hardness,low density and biocompatibility;Therefore,g-C₃N₄ has become one of the most promising materials for photocatalysis,surface modification,light-emitting devices and so on.Due to its suitable energy band structure(?2.7e V)and high thermal and chemical stability,it has become an attractive material in photocatalytic research.However,the performance of g-C₃N₄ synthesized directly is not ideal,and it needs to be modified to improve the photocatalytic performance of the material.Recent studies have found that g-C₃N₄ has great potential in the field of sensing because of its superior properties;However,it has some electrochemical disadvantages,such as relatively poor conductivity,which greatly limits its application in sensing applications.This paper focuses on the preparation of g-C₃N₄ nanosheets and the application of modified g-c3n4 in the field of photocatalysis and temperature sensing.1.Firstly,the effects of different sintering temperatures on the morphology of g-C₃N₄nanosheets were studied.Bulk g-C₃N₄ was prepared by thermal polycondensation at different temperatures,and g-C₃N₄ nano sheets were obtained by ultrasonic water stripping method.It can be seen from XRD and FTIR that the increase of sintering temperature did not cause the change of g-C₃N₄ material structure.Through SEM,we can see that when the temperature is between 550?570?,the nanosheets are dispersed and uniform.Further analysis by TEM shows that g-C₃N₄ presents nano sheet structure.Therefore,it can be concluded that the sintering temperature of 550?570?is conducive to obtain g-C₃N₄ nanosheets.2.The preparation,photocatalytic and photoelectric properties of modified g-C₃N₄nanosheets were studied.In this study,g-C₃N₄ was synthesized by simple thermal polymerization,and g-C₃N₄ was protonated by hydrochloric acid and nitric acid.The test results show that due to the strong chemical stripping and etching effect,g-C₃N₄ is stripped into nano flakes with rich in-plane nitrogen vacancies,and the specific surface area is improved.The electrochemical test results show that the modification improves the faster electron hole separation rate and stronger photoelectric conversion ability of g-C₃N₄.Finally,by simulating the catalytic degradation of Rhodamine B solution(Rh B)under sunlight,it was found that protonated g-C₃N₄ showed higher photocatalytic activity than untreated g-C₃N₄,HCN>NCN>g-C₃N₄.The photocatalytic mechanism was studied.The active material for photocatalytic degradation of RHB was mainly O₂^-.3?The application of protonated g-C₃N₄ in temperature sensing is studied.Firstly,g-C₃N₄ material was prepared by thermal polycondensation and protonated with different concentrations of sulfuric acid.The results show that the crystal structure of g-C₃N₄ remains unchanged after protonation,but its particle size decreases.For all samples,the luminescence intensity varying with temperature is linear with temperature.However,SCN-1 protonated with 20 vol%sulfuric acid showed the maximum temperature range(-153?127?)of linear temperature dependent behavior,The results show that after certain protonation treatment,the temperature sensing performance of g-C₃N₄ has been significantly improved,and the temperature sensing performance of S_R and low temperature has been improved.It shows that protonated g-C₃N₄ is a low-cost non-contact temperature sensor material suitable for a wide temperature range.