The Synthesis,Characterization And Application Of Multifunctional Graphitic Carbon Nitride Nanomaterials

Objective:Graphitic carbon nitride(g-C₃N₄),as a novel fluorescence nanomaterial,has been doped,modified or combined with other nanomaterials to form the different types of g-C₃N₄nanomaterials.They have attracted wide attention in the analytical detection and biomedicine due to excellent luminescence properties,great light stability,high fluorescence quantum yield,low toxicity and good biocompatibility.The g-C₃N₄ nanomaterials were used as fluorescence probes to detect silver ions in environmental water samples and dopamine in biological samples.The prepared g-C₃N₄ nanomaterials as fluorescence probes have broadened the application of detecting substance.PBCN was synthesized via the assembling different nanomaterials and g-C₃N₄.Under the irradiation of 808 nm laser,the PBCN could overcome the lack of photodynamic therapy or photothermal therapy to improve the combination therapy effect of PTT/PDT in cancer.Methods:Sulfur-doped graphitic carbon nitride nanosheets(S-g-C₃N₄ nanosheets),3-aminophenylboronic acid modified graphitic carbon nitride quantum dots(3-APBA-CNQDs)and prussian blue nanoparticle and graphitic carbon nitride nanosheets(PBCN)were synthesized.The morphology,surface functional groups,element composition and optical properties of the above g-C₃N₄ nanocomposites were characterized by TEM,XRD,FT-IR,XPS,FL and Uv-vis.The fluorescence probe was constructed to detect Ag⁺,based on the phenomenon that the fluorescence of S-g-C₃N₄nanosheets was effectively quenched by Ag⁺.We choosed hepatocarcinoma cell(Hep G2)as a cell model to verify the feasibility of S-g-C₃N₄ nanosheets for detecting Ag⁺in cells.The fluorescence of 3-APBA-CNQDs was gradually quenched with the increase of dopamine(DA)concentration.Based on the phenomenon,a fluorescence probe for detecting DA was designed.The imaging results of breast cancer cells(MCF)and the detection ability of DA,incubated with 3-APBA-CNQDS,were observed by laser confocal microscopy.Under 808 nm laser irradiation,the photothermal properties and ROS generation capacity of PBCN were investigated by using thermocouple and DPBF probe,respectively.The photothermal/photodynamic(PTT/PDT)nanocomposite was constructed to realize the collaborative treatment of cnacer.The toxicity of PBCN in MCF cells were evaluated by MTT assay.The cellular imaging ability of PBCN was verified by laser confocal microscopy.AM-PI staining was selected to study the PTT/PDT synergistic effect of PBCN in MCF cells.Results:The characterization results of S-g-C₃N₄ nanosheets,3-APBA-CNQDs and PBCNconfirmed that the above nanocomposites were prepared successfully.The good linear response of S-g-C₃N₄ nanosheets to Ag⁺was in the range of 0.01-3.04?M with a detection limit of 0.28 n M.The fluorescence probe has been successfully applied to detect Ag⁺with the recovery range of 98.73%-110.00%in real water samples.It was observed that S-g-C₃N₄nanosheets fluorescence were quenched Ag⁺through the confocal laser.The linear range of3-APBA-CNQDs as a fluorescent probe for detecting of DA was 0.1-51?M with a detection limit of 22.08 n M.The spiked recovery for DA ranged from 96.0%to 110.0%in blood and urine samples.3-APBA-CNQDs was applied intracellular imaging due to the advantages of good biocompatibility and low toxicity.It can been shown that bright blue and green fluorescence in MCF and PC12 cells at the excitation wavelengths of 405 nm and 488 nm,respectively.Among them,fluorescence quenching of PC12 cells stimulated by high salt concentration was observed.The PBCN with NIR absorption was used in imaging and synergistic therapy of cancer cell.The photothermal conversion efficiency of PBCN was60.1%.When DPBF probe was added into PBCN solution,the UV absorption decreased at the excitation wavelength of 425 nm.The survival rate of cells incubated with different concentrations of PBCN was 76%-19%.The incubated cells images showed red fluorescence in the cytoplasm at an excitation wavelength of 640 nm.Under 808 nm laser irradiation,MCF cells were labeled with DCFH-DA probe,and the CLSM images also appeared bright green at 488 nm excitation wavelength.After being labeled with AM-PI,the PTT/PDT group images also appeared a large amount of red fluorescence in MCF cells with PBCN.However,there were both green fluorescence and red fluorescence in PTT or PDT groups.These results indicated that nanomaterials with PTT/PDT synergistic effect are beneficial to treat cancer cells.Conclusion:The fluorescence probe was constructed to detect Ag⁺,based on the phenomenon that the fluorescence of S-g-C₃N₄nanosheets was effectively quenched by Ag⁺.The fluorescent probe has been successfully applied to detect Ag⁺in water samples.According to the ultraviolet spectrum,fluorescence lifetime and temperature change,it was preliminarily judged that the interaction between S-g-C₃N₄nanosheets and Ag⁺was mainly static quenching.S-g-C₃N₄ nanosheets with low toxicity and good biocompatibility were used to detect Ag⁺in cells,obtaining the satisfactory results.Based on the phenomenon that 3-APBA-CNQDs can specifically recognize DA,the fluorescence probe was applied to detect rapid and sensitive detecting DA in blood and urine samples with satisfactory results.At the same time,3-APBA-CNQDS showed strong imaging ability in MCF and PC12 cells.And visual detection of DA in PC12 cells was realized through fluorescence“bright-dark”change.PBCN had good photothermal response and photodynamic effect due to its absorption in the near infrared region.MTT assay showed that PBCN revealed obvious cytotoxicity under laser irradiation.The fluorescence imaging experiment showed that PBCN has excellent intracellular imaging capability.A large number of cancer cells apoptosised under the irradiation.The results indicated that the PTT/PDT synergistic treatment effect of PBCN could overcome the deficiency of single therapy and improve the therapeutic effect on cancer cells.