Study On The Construction And Properties Of Photoresponsive Materials Based On Carboxymethyl Cellulose

Cellulose was the most abundant renewable resource in nature witch had great physiochemical characteristics,such as sustainability,lower toxicity,good biocompatibility and biodegradability,etc.However,it also had inherent shortcomings,such as insoluble in water,poor dimensional stability,low reactivity,poor antibacterial properties,etc.,which limited its processing,utilization and functionalization.How to promote the utilization of cellulose resources and transform it into functional materials with controllable properties was a problem that must be considered.Carboxymethyl cellulose（CMC）,as an important derivative of cellulose,showed the characteristics of good water solubility,higher chemical reaction activity,film-forming properties,and properties of chelate with metal ions.The cluster luminescence properties of carboxymethyl cellulose indicated that it had excellent photoelectron transfer ability and could be transformed into a variety of controllable photoresponsive materials.Compared with other control methods,photoregulation had the advantages of time and space control,non-direct invasion and lower biological toxicity,considered to be the most effective ways to fabricate carboxymethyl cellulose materials.Base on the film forming and cluster luminescence properties of carboxymethyl cellulose,the film with light harvesting and conversion ability was constructed by mixing it with the nanoparticles UCNPs@CDs,with up-down conversion fluorescence and phosphorescence.The presence of UCNPs@CDs enhanced the ability of the composite membrane to capture ultraviolet（UV）and near-infrared（NIR）light,and promoted the composite membrane to convert UV and NIR light into visible light which can be directly absorbed and utilized by chloroplasts.The results of Hill reaction showed that the composite membrane successfully promoted the photosynthesis of chloroplast,and the photosynthetic rate increased about 1.8times.The rationally designed UCNPs@CDs/CMC composite light-harvesting film was able to enhance photosynthesis by Arabidopsis thaliana by～12%.These results indicated that the non-invasive light harvesting film can effectively expand the range of chloroplast sunlight utilization,enhance electron transport efficiency in photosynthesis,and promote plant photosynthesis.Based on the chelating between carboxyl group and metal ions,CMC-Fe crosslinking composite membrane was constructed by crosslinking ferric chloride/citric acid with carboxymethyl cellulose as raw material,and the water resistance of pure CMC membrane was successfully improved.By adjusting the concentration,ratio and time of crosslinking agent,the water resistance of crosslinking membrane could be accurately controlled.Under UV/visible light irradiation,photoelectron transfer between citric acid/CMC and Fe³⁺continues rapidly,resulting Fe³⁺reduced,the cross-linking network of the film collapsed,and CMC film degrades,finally.The reduction of Fe³⁺in the degradation process was determined by 1,10-phenanthroline,the molecular weight of CMC was determined by GPC,and the photodegradation mechanism of CMC-Fe crosslinked film was speculated.The antibacterial activity was tested by growth curve method.The membrane showed antibacterial activity to E.coli and S.aureus.Based on the photoelectron transfer properties between carboxymethyl cellulose and metal ions and the photoinduced redox reaction of Fe³⁺/Fe²⁺,a CMC-Fe cross-linked hydrogel with three-dimensional network structure was constructed as a photo-fenton catalyst.A homogeneous photofenton catalytic system was constructed by using catalyst and H₂O₂ to degrade organic pollutants in wastewater.Taking Rhodamine B（Rh B）as the target pollutant,the degradation regularity and kinetics of Rh B under different p H,H₂O₂,catalyst and light intensity were systematically studied.The degradation ability of the catalyst for different dyes was tested,and the extensibility of the catalyst was evaluated.The reactive species were determined by radical quenching experiment,and the mechanism of dye oxidation degradation by photo-fenton system was speculated based on the literature.On the basis of these studies,we attempted to initiate Fe³⁺/Fe²⁺redox reactions by NIR light in the crosslinking network through rare earth upconversion nanoparticles assisted photochemistry.The feasibility of NIR photoinduced Reduction of Fe³⁺was measured by UV-vis absorption and fluorescence spectra.Then,a photodetachable adhesive was designed by CMC-Fe and UCNPs to achieve near-infrared（NIR）light-detached topological adhesion between wet materials（hydrogel）.The photodetachable topological adhesive CMC-Fe,consisting of carboxymethyl cellulose and Fe³⁺that can be ptotodecomposed by UV light.The UCNPs can harvest NIR light and convert it into UV light,triggering the decomposition of the Cell-Fe and inducing the detachment.This NIR-detached topological adhesion is also feasible in deep tissue because of the ability of NIR light to penetrate tissue.