Design And Synthesis Of Near Infrared-Responsive Conjugated Oligomers And Application Research Based On Their Photothermal Properties

In recent years,near-infrared light-responsive materials have been widely developed as a relatively safe and effective photothermal reagent due to the deep tissue penetration ability and low damage to tissues of near-infrared light.The conjugated oligomer feature with well-defined structure,good solubility,light stability,narrow band gap,and good light-to-heat conversion capacity.Therefore,the preparation of conjugated oligomers with controllable polymerization degree and its application in photothermal materials are significant in further theoretical and application investigation.In this work,we take advantage of the photothermal properties of conjugated oligomers and the good biocompatibility of their nanoparticles to design a variety of nanomaterials with light-to-heat conversion capabilities.Application of dynamic regulation of CO₂adsorption and desorption,targeted antibacterial and the use of natural phase change materials to regulate the optical properties of conjugated molecules were performed.The main research contents include:1.A conjugated polymer(PDPP),a conjugated oligomer(ODPP)and a dimer(2DPP)were prepared and characterized by using pyrrolopyrrole dione as building blocks.Conjugated oligomers of ODPP contain four DPP units.Compared with the dimers(2DPP),the absorption spectrum is red-shifted and stronger photothermal effect can be observed.Compared to DPP based polymers(PDPP),conjugated oligomers not only have strong light-to-heat conversion ability,but also overcomes the disadvantages of poor batchability and poor solubility in polymer synthesis.After calculation,ODPP exhibit excellent light-to-heat conversion ability,and the light-to-heat conversion efficiency under NIR light irradiation is 45.1%.2.ODPP and amphiphilic molecule DSPE-PEG₂₀₀₀-MAL are assembled together to prepare water-soluble nanoparticles(ODPP NPs)with uniform particle size.Firstly,polyethyleneimine(PEI)molecules are modified on the surface of ODPP NPs,which can capture CO₂in a reversible manner.Under the irradiation of near-infrared light at 808 nm,the temperature of the medium surrounding NPs rises rapidly,so that the near-infrared light can dynamically control the adsorption and desorption of CO₂.Secondly,aptamer-functionalized nanoparticles AF-ODPP NPs were obtained by modifying the surface of ODPP NPs with a nucleic acid aptamer that can specifically recognize S.aureus,and the antibacterial properties of the nanoparticle were studied.We found that in a mixed solution of E.coli and S.aureus,aptamer-modified nanoparticles can selectively capture S.aureus,and exhibit the ability to selectively recognize and kill aureus under near-infrared light.Finally,using a natural phase change material with different components as a matrix,ODPP,PMNT and amphiphilic molecules can assemble into nanoparticles to obtain nanoparticles with both fluorescence and photothermal effects.Using fatty acids as the matrix of nanoparticles not only broadens the absorption spectrum of ODPP to the infrared region and enhances the light-to-heat conversion ability,but also can adjust the aggregation state of conjugated molecules through the phase change of nanoparticles by near-infrared light,thereby regulating their optical characteristics.This intelligent nanoparticle system are potential in further application of the fields of biomedical imaging,photothermal treatment of tumors and other fields.