Exploring Of Luminescence Properties Of Novel Natural Compounds

Aggregation-induced emission(AIE)materials have received increasing attention due to their excellent sensitivity,good selectivity,and high quantum yield.Most of the traditional AIE materials are prepared by organic synthesis.Although these artificial luminescent materials have the advantages of diversity and color adjustment,their practical application is limited due to the disadvantages of complex organic synthesis,high cost and high toxicity.Furthermore,considering that biomedical research is usually performed in aqueous solutions,thus,developing low-toxic,low-cost and green AIE materials is a key issue in the pharmaceutical industry.Therefore,it is of great significance to find new biocompatible,water-soluble and biodegradable AIE materials for biomedical research.This thesis mainly studies the photophysical process of traditional aromatic molecules from natural products,thermosensitive nanohydrogels with reversible AIE and non-traditional non-aromatic molecules,and AIE Schiff base compounds with antibacterial properties and endow them with antibacterial properties.Based on the above research,we have achieved the following research results:1.The riboflavin(Rf,namely vitamin B2)was found to be a natural active AIE molecule with excited-state proton transfer(ESPT)process,which is widely existed in the food from both plants and animals.The AIE material palmatine(PA),which is a natural product,is a total alkaloid extracted from the stems and roots of plants Fibraurea recisa Pierre.The fluorescence properties were analyzed by fluorescence spectroscopy and UV-Vis absorption spectroscopy,indicating that they are a new type of AIE molecule.In addition,Rf and PA have good biocompatibility and low toxicity,thus,they have potential application values in bioimaging.2.Based on photophysical properties studies of non-traditional natural products derived from inulin(IUL),xanthan gum(Xag)and Oat-?-glucan(Oat-?-Glu).The clustering-triggered emission(CTE)mechanism and room temperature phosphorescence(RTP)properties of IUL,Xag,Oat-?-Glu were discovered.In addition,IUL,Xag,Oat-?-Glu have potential applications in biosensors and multicolor cell imaging.Moreover,IUL can also be applied to anti-counterfeiting detection.3.The AIE properties and CTE mechanisms and RTP phenomena based on natural silk fibroin(SF)and tilapia skin collagen(Tsc)were explored.The electrons communicate through space due to the aggregation of peptide backbone and side chain groups,and the rigidity of the conformation due to aggregation is also responsible for the bright blue emission.Additionally,SF and Tsc can be used as multicolor bioimaging and biosensors.Therefore,SF and Tsc are novel CTE biomaterials with various application values.4.AIE-active assembly of HA-Cys-PN/BBR reversible nanohydrogels was prepared by RAFT polymerization.By encapsulating the guest drug of BBR in the HA-Cys-PN hydrophobic domain,the fluorescence intensity can be easily turned,which provides a simple method to construct luminescent nanohydrogels in aqueous media.HA-Cys-PN/BBR is a fluorescent probe that can sense intracellular temperature through slight changes of fluorescence.In addition,HA-Cys-PN/BBR also has the antibacterial properties.Therefore,HA-Cys-PN/BBR has excellent application value in temperature biosensors and broad spectrum antibacterial property.5.In this work,we designed and synthesized an AIE fluorescent material based on the Schiff base compounds of chitosan(Cs)and salicylaldehyde(SA).Cs-SA emits weak light in dilute aqueous solution and bright light in concentrated solution and solid,exhibiting obvious AIE performance.In addition,Cs-SA can also be used as a biosensor to detect Fe³⁺,Cu²⁺and can quantitatively detect Gram-positive and Gram-negative bacteria.Moreover,Cs-SA has good resistance to photobleaching.In addition,Cs-SA shown more excellent antibacterial properties in inhibiting E coli and S aureus.Therefore,Cs-SA is expected to be a novel AIE Schiff base compound with multiple applications.