Interfial Functionalization And Sensing Of Carbon Nitride Semiconductors

Graphite carbon nitride（g-CN）has good chemical stability,thermal stability,unique chemical and electronic structure.In recent years,g-CN has been extensively applied and developed in many fields,such as energy/environment catalysis,photoelectric conversion,sensing and so on,because of its low cost,good stability and nonmentalic feature and unique electronic band structures.In order to improve the activities and understand the structure and properties relationship of carbon nitride materials,various functionalization strategies for g-CN have been extensively explored and studied,including regulation of micro/nano structure and preparation of composite functional materials.However,these functionalization strategies take little concern for the thermal polymerization processes during g-CN preparation,which has huge and significant impacts on the structure and properties of the final g-CN products.Secondly,because most of the functionalization strategies are mainly focused on how to improve the photocatalytic performance of g-CN,there are few studies on how to optimize the optical properties of g-CN and to improve the dispersion stability of g-CN nanosheet to solve the basic challenges in the field of sensing applications.This thesis mainly includes the two following parts:1.Bulk CN was often prepared by calcining dicyandiamide at high temperature.By altering different thermal polymerization processes,different bulk CN were prepared,and the effects of thermal polymerization rate and holding time on the structure and properities of carbon nitride materials were investigated.The experiment results show obviously that the effect of the change of thermal polymerization rate on the photoelectric properties of g-CN material is significant.The g-CN material prepared under rapid thermal polymerization exibits a better photoelectrical conversion and photocatalysis performance because of its larger surface area,better crystallization and higher efficiency of photoelectron/hole separation.Compared to the traditional bulk CN,the efficiency of hydrogen production is increased by 3 times.These results reveal that regulating thermal polymerization knetics could become an effective and powerful way to improve the photochemical properties of g-CN.The method is simple and holds great potential in realistic applications.2.The carbon nitride nanosheets（CNNS）obtained by liquid-state exfoliation are combined with polymers with polyhydroxyl functional groups,and the CNNS is successfully dispersed into polymer matrix.The composite can not only retain the fluorescence of the CNNS,but also overcomes the shortcomings of the dispersion instability of the CNNS and the limited application areas resulting from the aqueous solution system.At the same time,the sensing system based on g-CN fluorescence signal for polycyclic aromatic hydrocarbons is constructed,and the rapid and sensitive detection of several kinds of polycyclic aromatic hydrocarbons（PAHs）mixtures is achieved.The linear range reaches 0.5-100 ng mL^-1,the correlation coefficient is 0.992,and the detection limit reaches 0.225 ng mL^-1.Compared with the traditional methods of detecting PAHs,the sensing system constructed by us has many advantages,such as portabilty,short detection time,simple detection steps and good sensitivity.The method expands the application of the optical properties of g-CN in the sensing field and would open up a new world of g-CN applications by dispersing CNNS into polymers and other novel substrates.