Synthesis Of Graphite-like Carbon Nitride-based Functional Materials And Their Application In Organic Pollutant Degradation,disinfection And Ion Detection

With the rapid development of industry of economy,the problem of environmental pollution has become increasingly prominent,especially the water pollution has become the focus of attention,such as refractory organic pollutants,heavy metal,pathogenic microorganisms and other water pollutants have posed a serious threat to food safety and human health.Therefore,how to quickly and efficiently remove pollutants from water,as well as detect hazardous substances in food,have become important research goals.Photocatalytic technology and the fluorescence properties of semiconductor materials provide a green and efficient solution.Among them,graphite-like carbon nitride?g-C₃N₄?is not only popular in the field of photocatalysis,but also can be used as a fluorescent probe for the detection of food hazards due to its visible light response,non-metallic,good stability and low cost.In this paper,g-C₃N₄ is used as the main material,and its photocatalytic activity and fluorescence sensing performance are significantly improved by means of morphology control,element doping and heterojunction construction,so as to realize the high-efficiency detection,effective control and removal of food hazards by g-C₃N₄-based functional materials.The specific research contents are as follows.1.Perylene diimide?PDI?/oxygen-doped g-C₃N₄ nanosheets?O-CN?organic heterojunction photocatalyst was prepared by an in-situ electrostatic assembling.And the morphological structure and photoelectric properties of PDI/O-CN were systematically studied by various techniques.The phenol degradation rate and evolved oxygen amount in 2 h of PDI/O-CN-40%were 3.63 and 1.84 times as high as those of O-CN respectively and96.6%of Staphylococcus aureus was inactivated in 3 h.The cycllic degradation experiment shows that the composite has good recycling ability.Finally,the mechanism of enhanced photocatalytic activity of PDI/O-CN organic heterojunction was clarified:self-assembled PDI could broaden the visible response range of O-CN;?-?interaction between them could lead to the electron delocalization effect to facilitate the electron migration;the interlaced band structures of O-CN and self-assembled PDI could also result in a built-in electric field to accelerate the interfacial charge separation;and a large amount of active species could be generated in PDI/O-CN heterojunction.The construction of PDI/O-CN heterojunction provides a new idea for the design of supramolecular semiconductor/g-C₃N₄ heterojunction system.2.5,10,15,20-tetra?4-carboxyphenyl?porphyrin?TCPP?/O-CN organic heterojunction composite was prepared by an in-situ electrostatic assembling,which further revealed the mechanism of enhanced photocatalytic performance of supramolecular semiconductor/g-C₃N₄ heterojunction system.SA-TCPP could broaden the visible response range of O-CN;the strong?-?interaction between them promotes the electron migration;and the interlaced band structures of O-CN and SA-TCPP could result in a built-in electric field to accelerate the interfacial charge separation;and more active species could be generated in TCPP/O-CN composites.Therefore,TCPP/O-CN exhibited enhanced visible photocatalytic compared with O-CN.The the degradation rate constant of bisphenol A was about 3.69 times as high as that of O-CN under visible light,and the degradation efficiency of 2,4-DCP was 1.75 and 1.23times of that of O-CN and SA-TCPP,respectively.3.Porous g-C₃N₄ nanosheet?PCNS?photocatalyst was prepared by a template-free approach,and the fluorescence properties of g-C₃N₄ based functional materials were studied.Compared with bulk g-C₃N₄,the dispersibility,solubility and fluorescence quantum yield of PCNS were greatly improved.Subsequently,a fluorescence“on-off-on”sensing method based PCNS was designed for detecting Cr?VI?and SO₃^2-.Due to the inner filter effect,Cr?VI?can effectively quench the fluorescence of PCNS solution.The detection linear range of Cr?VI?is from 0.625?mol/L to 300?mol/L with a limit of detection?LOD?of 0.112?mol/L.Then,the redox reaction between Cr?VI?and SO₃^2-can restore the fluorescence of PCNS and realize the detection of SO₃^2-.And the detection linear range of SO₃^2-is from 2?mol/L to 100?mol/L with an LOD of 0.303?mol/L.The proposed fluorescence detection method has high selectivity for Cr?VI?and SO₃^2-and can be applied to detect Cr?VI?in water and SO₃^2-in sugar.