Preparation And Analytical Applications Of Doped Graphite Carbon Nitride And GQDs

Carbon nanomaterials,as a new type of nanomaterials,have been broadly used in many fields such as analytical testing,device equipment and energy catalysis.This paper studies the preparation and their sensing applications of graphite carbon nitride and GQDs.Preparation of doped graphite carbon nitride,and explore its synergy effect with Hg²⁺ to coordinate porphyrin and Co²⁺,and used it for highly sensitive detection of heavy metals Hg²⁺ in environmental samples.To prepare the GQDs with good fluorescence properties and combine it with rare earth ions erbium or praseodymium to form complex probe and use this probe to detect thrombin in biological samples based on the change of it's fluorescence.Besides,building the GQDs-PHBA fluorescent probes for selective detection of GSH based on the principle of glutathione?GSH?solution can make the absorption peak of p-hydroxy benzaldehyde?PHBA?moved.The main details are as following:1.Using melamine,boric acid and molybdenum sulfide as raw material to synthesis of boron and sulfur co-doped graphite carbon nitride?abbreviated to CNBS?through the way of high temperature thermal polymerization.Then we discussed its structures and fluorescence properties through the electron microscopy,FT-IR,XRD,XPS and fluorescence characterization methods.The study found that the negatively charged CNBS and Hg²⁺ have a good co-acceleration effect on the combination of porphyrin?TMPyP?and Co²⁺.Using electron microscope,Zeta potential and inner filter effect to explore the cooperative catalysis mechanism of CNBS and Hg²⁺ on the combination of porphyrin and Co²⁺.That is,CNBS interacts with Hg²⁺ to form complex,and then attaches to the porphyrin ring through electrostatic and ?-? stacking cooperative interactions to form a ‘SAT' complex rapidly and then deforms the ring paving the way for Co²⁺ coming,and finally,quenching the fluorescence of porphyrin.Based on this principle,it can be used for Hg²⁺detection with the detection limit as low as 0.37 nM.2.Building a method for thrombin detection based on the fluorescent probe of GQDs/Er³⁺.Rare earth ions Er³⁺ could assemble on the surface of GQDs and cause the PL quenching of GQDs because Er³⁺ ions can coordinate to the carboxylate groups on the surface of GQDs,after the introduction of thrombin,oxygen and nitrogen-donor atoms in thrombin can coordinate to Er³⁺ ions and thus compete with the carboxylate groups on the GQDs surface,resulting in the divorcement and restoration of GQDs.The fluorescent recovery degree was positively correlated with the concentration of thrombin,thus can realize high sensitive detection of thrombin with the detection limit as low as 0.049 nM.Using electron microscopy,light scattering and other means to confirm the mechanism of thrombin detection.This nanosensor needs no further surface functionalization of GQDs or employment of thrombin aptamers,only use of the fluorescence of GQDs to sense trace amounts of thrombin.To further verify the the universality of the complexes probe of rare earth ions and GQDs for thrombin detection.We investigate the thrombin detection of the probe of rare earth ion Pr³⁺ and GQDs.The study found that the probe of GQDs/Pr³⁺ complex divorced and restored the fluorescence of GQDs that can be used for thrombin sensing once adding thrombin.The detection range is from 0.1 to 25 nM with a detection limit as low as 0.06 nM.And it also proved that the universality of the complexes probe of rare earth ions and GQDs,it also provides a new thought for the sensing of thrombin in complex samples.3.Based on the principle of glutathione?GSH?solution can make the absorption peak of p-hydroxy benzaldehyde?PHBA?moved,we build the GQDs-PHBA fluorescent probes for selective detection of GSH.When hydroxy benzaldehyde?PHBA?was added into GQDs solution,the absorption peak at 330 nm of PHBA will absorb the excitation light source of GQDs,which lead to inner filter effect causing the fluorescence of GQDs quenching.After injecting glutathione,the absorption peak of PHBA wil blue shift and avoid the inner filter effect,that makes the fluoresce of GQDs recovery.Based on this principle,it can realize the specific detection of GSH without the interference of Cys and Hcy.