Mesoporous Silica-loaded Ce6 Photocatalytic Degradation Of Ethylene For Fruit Preservation And Preservation

Ethylene,a plant hormone,is the main cause of post-harvest spoilage of fruits and vegetables.In order to reduce its post-harvest loss,the effective removal of ethylene is very important.Currently,many strategies have been developed,such as various ethylene scavengers/inhibitors containing catalysts and some emerging technologies,to extend the shelf life of harvested fruits and vegetables.Among them,ethylene scavengers and inhibitors are of particular concern because they can promote the in-situ oxidation of ethylene without causing further pollution.At the same time,the method of packaging ethylene scavengers（such as zeolite,titanium dioxide and transition metal）in a small bag has been applied and widely reported.However,the materials or films that add ethylene scavengers and ethylene in-situ oxidizers in food packaging are rarely studied.As mesoporous silica nanoparticles are the most controllable nanomaterials with high specific area and multiple pores,they can be well applied to the adsorption and removal of ethylene.Therefore,the main content of this study is to use efficient ethylene catalyst combined with mesoporous silica nanoparticles,and then use sodium alginate hydrogel film to prepare composite nanomaterials for postharvest preservation of fruits and vegetables.In this study,a series of mesoporous silica based composite nanomaterials were designed and synthesized.The main research contents are as follows:（1）Mesoporous silica nanoparticles with sizes ranging from 100-200nm were synthesized using a conventional hydrothermal method,and Ce6,a photosensitizer material with catalytic effect,was encapsulated into the pores of the nanoparticles to construct a Ce6@Si O₂ composite nanomaterial system that can adsorb and degrade ethylene under visible light conditions.By using UV-Vis,FT-IR,SEM and other characterization means,it was shown that the nanoparticle mesoporous silica with good porous structure and high specific surface area can adsorb ethylene efficiently.Meanwhile,due to the photosensitizer Ce6loaded in the mesopores,a large amount of reactive oxygen species is generated under visible light irradiation to catalyze the degradation of ethylene,and it was demonstrated by ethylene degradation experiments that it effectively degrades 30 ppm of ethylene within 8 hours.This was also well confirmed by tomato preservation experiments,where the color change of tomatoes in the experimental group with and without composite material was significantly less than that of the control group.This would be useful to demonstrate its ability to extend the shelf life of fruits by degrading ethylene during storage.The results of this series of experiments indicate that the nanocomposites prepared in this study have very good application prospects.（2）Since Ce6@Si O₂ composite nanomaterials are in powder form which is very inconvenient in practical packaging applications,by coating them on the surface of sodium alginate hydrogel film,the overall surface area of the material is largely increased and the efficiency of degrading ethylene is also effectively improved,which also solves the practical packaging and application problems of composite nanomaterials.Based on this,we constructed SA/Ce6@Si O₂nanomaterials.The actual degradation ability of the material was investigated by experimentally measuring the concentration of ethylene in Tedlar gas sampling bags and the change of its humidity to effectively degrade 30 ppm of ethylene within 6 hours.Bacteria inhibition experiments demonstrated the excellent antimicrobial effect of the nanocomposite itself with a sterilization capacity of 98%,making it effective in preventing bacterial infection during the preservation of fruits and vegetables.In the final fruit experiment,the color change and surface spoilage of tomatoes stored with and without the composite nanomaterials were observed to demonstrate their practical application,and the results showed that the studied mesoporous silica-based composite nanomaterials have excellent preservation effects and are expected to be used in actual commercial preservation systems.