Preparation And Functionalization Of G-C₃N₄ Nanosheets And Their Application In Fluoresence Sensing

Two-dimensional(2D)g-C3N4 nanosheets have attracted extensive attentions because of their good photocatalytic activities and biocompatibilities.Here,2D g-C3N4 nanosheets is prepared by a one-step microwave-assisted intercalation strategy.By the same method,also prepare metal oxide or metal sulfide decorated g-C3N4 nanosheets by adding the corresponding metal precursors and sulfur sources.The applications of these 2D hybrid nanosheets in sensing and photocatalytic degradation is studied.In the first chapter,a review of g-C3N4 is given briefly,including the special structures,property,preparation and modification methods,as well as their applications in photocatalysis,electrocatalysis,sensing,disinfection,and drug loading.In the second chapter,a novel microwave-assisted intercalation approach was developed to prepare 2D g-C3N4 nanosheets by exfoliating bulk g-C3N4.The resulted g-C3N4 nanosheets is about 6-18 C-N layers.The proposed method not only reduces the exfoliation time significantly,but also improves the water-solubility and photoelectrical property of g-C3N4.The g-C3N4 nanosheets present the bandgap luminescence behavior.Compared to bulk g-C3N4,the g-C3N4 nanosheets modified electrode exhibits excellent stability,low electrochemical impedance and high photocurrents,providing potential applications in constructing sensitive electrochemical and photoelectrochemical sensors.In the third chapter,the microwave-assisted intercalation approach was developed to synthesis 2D heterostructure,i.e.ZnO/g-C3N4,CdS/g-C3N4,and MoS2/g-C3N4 nanosheets by adding the metal precursors and sulfur sources.The nanocomposites are studied in the following two aspects:(a)2D ZnO/g-C3N4 nanosheets with tunable dual emission and ultrasensitive and selective fluorescence response to Hg2+ ions.The fluorescence of ZnO/g-C3N4 shows a wide linear region and low detection limit in response to the Hg2+.There was a good linear relationship between the ratiometric fluorescence intensity and Hg2+concentration in the range of 5.O0×10-8～1.0×10-4 g/L and 100×10-4 g/L～1.1×10-2 g/L,with the detection limit of 1.0×10-9g/L-1.(b)Compared to bulk g-C3N4,the as-formed CdS/g-C3N4 hybrids exhibit a broader absorption in the visible-light region,and thus show an obviously enhanced photocatalytical activity.The CdS/g-C3N4 nanosheets can photodegradate 80%of AO7 within 10 min under visible light irradiation.