| Since the discovery of carbon dots fluorescent nanomaterials,the excellent photoluminescence properties,good fluorescence stability,low toxicity,low cost and easy preparation are widely used in many fields such as biosensor,cell imaging,ion detection,photocatalysis,drug carrier and so on.Chitosan,a natural macromolecule amino polysaccharide structure,has the advantages of non-toxic,easy to film,easy to molecular modification,and has been applied to the synthesis of polymer carbon dotss.But the pure chitosan polymer carbon dots has low quantum yield,short fluorescence life,less active sites and poor selection,which affects its application effect.So it is of great significance to prepare the carbon dots of chitosan polymer with high quantum yield and enlarge its application range.In this paper,two kinds of chitosan-based carbon dots P(CS-g-CA)Ds and P(CS+CA)Ds were synthesized by grafting and doped citric acid,and compared with pure chitosan polymer carbon dots P(CS)Ds.Through FT-IR,UVspectra,fluorescence spectra,X-ray diffraction,thermogravimetric analysis,fluorescence stability and other methods of the polymer carbon dots structure characterization and performance test,and the polymer carbon dots quantum yield and fluorescence life test,the results show that grafted chitosan polymer carbon dots P(CS-g-CA)Ds The fluorescence lifetime and quantum yield of PDs and doped polymer carbon dots P(CS+CA)Ds are higher than those of pure chitosan polymer,which shows that the doping and grafting of citric acid can effectively improve the fluorescence life and quantum yield of the carbon dots.In this paper,the synthesis of polymer carbon dots P(CS-g-CA)Ds with high quantum yield was applied to rice paper,and the antioxidative properties of rice paper were tested,and the results showed that the P(CS-g-CA)Ds had good antioxidant property,and the P(CS-g-CA)Ds was studied by ultraviolet accelerated aging test.Anti-ultraviolet aging properties of rice paper by PDS the attenuation total reflectance FT-IR spectra of paper were tested,and the carbonyl index and vinyl index on the paper surface were calculated,and the results showed that the carbonyl index and vinyl index increased by 0.24%and 0.29%respectively after the aging 48h,after the polymer carbon dots P(CS-g-CA)Ds was added to rice paper Aging 48h.the carbonyl index increased by 0.16%,the vinyl index increased by 0.1%.According to the conclusion that the greater the oxidation degree of carbonyl index and ethylene index,the fluorescence polymer carbon dots has the effect of ultraviolet aging.The P(CS-g-CA)Ds is used for a variety of ion detection,the fluorescence emission spectra are tested,and the Al3+,Cd2+,Hg2+ and Pb2+ ions have fluorescence quenching effect on the polymer carbon dots,especially Pd2+ has strong fluorescence quenching effect,pd2+ In the 0-100?m,the pd2+ limit of the polymer carbon dots is 1.48nM/L.The quenching mechanism of polymer carbon dots to pd2+ was studied by testing the change of fluorescence spectral intensity of pd2+ at different temperature,ultraviolet spectra of pd2+ and polymer carbon,and fluorescence lifetime change,and the results showed that with the increase of temperature pd2+ The quenching constants and binding constants of the polymer carbon dotss are increased,which proves that the quenching mechanism is static quenching,and the fluorescence lifetime and ultraviolet spectra show that the quenching mechanism of pd2+ and P(CS-g-CA)Ds is static quenching.The polymer carbon dots P(CS-g-CA)Ds was added to Carboxymethyl Cellulose(CMC)and Hydroxyethyl Cellulose(HEC)to make the light film material.The newly synthesized light conversion film makes the ultraviolet light harmful to plants in the 200-300nm into the 450nm blue ray which is beneficial to plant growth,and its efficiency and transparency are higher and it is not easy to be oxidized by light bleaching.It is indicated that P(CS-g-CA)Ds can be applied as a light conversion agent. |
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