Preparation, Modification And Composite Spinning Of Sodium Alginate-based Carbonized Polymer Dots

Carbonized polymer dots(CPDs)are arising as a new type of fluorescent materials.It has large variety of raw materials with low price,among which sodium alginate has its unique advantages.As a natural linear polysaccharide,sodium alginate has excellent properties such as rich source,renewability,biodegradability and good biocompatibility.The abundant hydroxyl and carboxyl groups on the molecular chain of sodium alginate are potential sub-fluorophores and are easy to be chemically modified.Based on the above research background,this paper is committed to using sodium alginate as raw material to prepare environmental-friendly CPDs and apply them to the preparation of alginate textile and nano-fibers.Here,a new type of CPDs was synthesized by hydrothermal treatment of glutaraldehyde and sodium alginate,which was named SG-CPDs.According to the cross-linking enhanced emission effect(CEE),the fluorescence of SG-CPDs was significantly enhanced upon the cross-linking of sodium alginate with glutaraldehyde.The formation process of SG-CPDs at different reaction temperatures was discussed.In addition,it was found that SG-CPDs had stable fluorescence properties in weak acidic/alkaline and metal ions environments.The toxicity of the SG-CPDs in vitro was tested.Based on its non-toxic properties,sodium alginate films with anti-ultraviolet aging properties were prepared by using CPDs as additives.Polyethyleneimine(PEI)was then modified on the surface of SG-CPDs by stirring at room temperature to obtain PEI-CDs.The method greatly improved the fluorescence efficiency of the CPDs and solved the problem of low quantum efficiency of SG-CPDs.The structure and fluorescence properties of PEI-CDs were characterized by transmission electron microscopy(TEM),infrared spectroscopy(FT-IR)and ultraviolet spectrophotometer(UV-vis),and the possible fluorescence enhancement mechanism was discussed.It was confirmed that the modified carbon dots had higher quantum efficiency and acid and alkali resistance.In addition,based on the excellent properties of PEI-CDs,the fluorescent composite alginate textile/ nano-fibers were successfully prepared by adding the carbon dots into sodium alginate wet spinning solution and electrospinning solution.The morphology,fluorescence properties,rheological properties and mechanical properties were characterized and tested.The results show that the fluorescent fibers obtained by wet-spinning have good fluorescence adhesion and heat resistance.The nanofibers obtained by electrospinning have uniform thickness and no bead phenomenon without surfactant.