Functional Materials Of Fluorescence And Adsorption On The Basis Of Polysaccharide

Functional materials are materials that have a variety of different functions and uses.With the deepening of science and technology in various fields,new functional materials are rapidly emerging to meet a wide range of application needs.Fluorescence and adsorption separation are two important application directions of functional materials and play an irreplaceable role in the fields of biomedicine and energy environment.In the face of the increasing consumption of non-renewable resources,renewable resources such as cellulose and chitin show great application prospects.Their research,development and utilization have become hot topic.They are rich in reserves,chemically inert,safe,non-toxic,biocompatible and biodegradable.They are ideal raw materials for the construction of fluorescent biological functional materials and adsorption separation materials.In this work,cellulose and chitin were used as raw materials to construct novel fluorescent functional materials through hydrothermal carbonization as well as blended with fluorescent materials,and separation functional materials through in-situ synthesis,respectively.At the same time,The structures and properties of these materials were characterized by using scanning electron microscope(SEM),transmission electron microscope(TEM),infrared spectroscopy(FT-IR),X-ray diffraction(XRD),X-ray photoelectron spectroscopy(XPS),thermogravimetric analysis(TGA),solid-state nuclear magnetic resonance spectroscopy(13C NMR),ultraviolet-visible spectroscopy(UV),photoluminescent spectroscopy(PL),N2 adsorption,and mechanical properties tests,and their application prospects in the field of bioimaging and separation adsorption were evaluated.The main innovations of this work include as follow:(1)based on rapid synthesis of carbon dots through acid-catalyzed,realized the rapid synthesis of carbon dots under mild conditions,and target imaging of cancer cells by modification carbon dots with DNA aptamers;(2)through hydrothermal method with acid catalysis,uses chitin as raw material to construct carbon dots with high fluorescent quantum yield;(3)based on hydrogen bonding of rare earth-doped phosphor and cellulose,to construct hydrogel with long afterglow,and apply in vivo digestive tract imaging of living mice;(4)based on nanofibers structure of chitin microspheres,zeolitic imidazolate frameworks(ZIF-67)was in situ synthesized on the surface of chitin microspheres to construct composite microspheres of ZIF-67 and chitin with multi-scale pore structure;(5)pores were fabricated in chitin microspheres through multi-emulsion method,and MIL-101 was successfully loaded in the pores of chitin microspheres.The as prepared composite microspheres have adsorption function to benzene vapor.The main research contents and conclusions of this paper include five parts as follow:Biocompatible carbon dots(ACDs)were synthesized via hydrothermal method from amino acids as raw materials using hydrochloric acid as a catalyst under mild conditions.Hydrochloric acid may promote the formation of carbon cores by accelerating the carbonization process,shortening the synthesis time from 10 h to 2 h.ACDs are semispherical nanoparticles with an average particle size of 3.8 nm and have rich-NH2 group on the surface.ACDs were successfully functionalized by MUC-1 mucin DNA aptamer,giving them the ability to recognize MCF-7 cells specifically.ACDs display bright blue fluorescence under excitation,and their emission wavelength does not shift with the change of excitation.The fluorescence of the ACDs after binding to DNA aptamers is basically unchanged.Cellular experiments show that DNA-ACDs can be used for targeted imaging of MCF-7 cells and are expected to provide valuable new method for the diagnosis and treatment of cancer.The hydrothermal method with hydrochloric acid was used to crush and carbonize chitin as a carbon source,and a one-step synthesis of carbon dots with high fluorescence quantum yield(reached 30%)was achieved.The resulting carbon dots(CCDs)have an average particle size of 3.1 nm.They mainly comsist of highly crystalline carbon cores and have possible amorphous carbon layers and surface functional groups.The carbon cores are doped with N and O atoms.CCDs are amorphous structure with good dispersibility in water.Their aqueous solution can emit strong blue fluorescence under UV excitation and is responsive to Fe3+ and Cu2+.The fluorescence properties of CCDs are consistent under the biological pH range and are suitable for application of bioimaging.The CCDs obtained from chitin are biocompatible materials that can be used as potential replacements for fluorescent dyes in bioimaging.The cellulose-PP composite hydrogel(CPH)was successfully constructed by cross-linking via epichlorohydrin of a cellulose solution,which rare earth-doped phosphor(PP)dispersed homogeneously.CPH has a good appearance and processing properties,and PP is uniformly dispersed and fixed in the cellulose hydrogel network.The strong physical interaction between PP and cellulose enables them good compatiblility,and also gives the hydrogel good mechanical properties and light transmission.The original crystal structure and properties of PP are not changed in the composite hydrogel,resulting in strong fluorescence emission and long afterglow characteristics of CPH under UV excitation.The PP particles are entrapped and fixed in the pore walls of the macroporous structure of the network,which improves the dispersibility of PP in water and have advantages in biological applications.CPH has stable fluorescence and low toxicity.It is suitable for in vivo imaging.Its long afterglow which have high resolution and a large depth of detection can be detected both subcutaneously and in stomach.ZIF-67/CM composite microspheres were successfully constructed by in-situ synthesis of one of zeolitic imidazolate frameworks contains Co(ZIF-67)on the surface of chitin microsphere(CM).The loading of ZIF-67 was about 20%.ZIF-67 binds to the surface of CM through physical interactions such as hydrogen bonding.ZIF-67 can not be washed off from the surface of CM after repeated cleaning with various solvents.Part of the ZIF-67 crystals encapsulating chitin nanofibers to form special structure,which further increase the stability of the composite microspheres.The interior of the CM also shows a uniform nanofibrous structure,but almost no nanocrystals were observed.ZIF-67/CM has good thermal stability and can maintain stable under 250 ?.ZIF-67/CM possesses a large number of micropores and mesopores and was multi scale pore structure materials.Porous chitin microspheres(PCM)were successfully constructed by the emulsion template method.The PCM presents uniform nanofiber structure on the surface as well as uniform porous structure inside.These pores with average diameter of 2.4 ?m areseparated from each other and both have nanofibrous structure pore wall.By storing sufficient ions and organic ligands and providing space for the formation of MOF through the porous structure,MIL-101 with particle size between 20 to 100 nm was successfully grown onto the pore wall inside the PCM.The structure of the PCM is basically unchanged after loading of MIL-101,and almost no nanoparticle adheres to the outer surface of PCM.MIL-101 is immobilized on the surface of the nano fiber structure of PCM through physical interactions such as hydrogen bonding.MIL-101/PCM has good thermal stability and is multi scale pore structure materials for mesopores and micropores coexist.It has good adsorption effect on benzene vapor and has potential applications in gas separation and adsorption.This thesis used the groups of cellulose and chitin to create a series of fluorescent and separation functional materials based on cellulose and chitin successfully.These results provide new ideas and new methods for designing functional materials such as chitin-based carbon dots,cellulose-rare earth phosphor composite hydrogels,and chitin-MOF composite microspheres.These results of basic research have obvious innovation and academic value,and are consistent with the strategy of sustainable development.Therefore,this paper has important scientific significance and application prospects.