| Biofluorescence imaging can visually detect biomolecules,cells,tissues and organs in a three-dimensional range in real time.It can track various physiological processes of organisms and help us understand the relationship between biomolecules and their structures and functions.Near-infrared imaging has the advantages of high temporal and spatial resolution,small damage to biological tissues,strong penetrating power,high sensitivity,and low background fluorescence interference.However,the disadvantages of current fluorophores include relatively low fluorescence quantum yields and shorter emission wavelengths,especially in the second near-infrared window（1000-1700 nm,NIR-II）.In the in vivo application of near-infrared fluorescent materials,issues such as biocompatibility,fluorescence quantum efficiency,and adjustability of excitation and emission wavelengths in the near-infrared region should be considered.Therefore,organic polymer materials are ideal for constructing NIR fluorescent probes.Dione pyrrolopyrrole（DPP）has the advantages of good planarity,strong electron affinity,high electron mobility,easy purification,easy structure modification and high molar absorption coefficient.It is an excellent photosensitizer and photothermal reagent,and It is regarded as one of the ideal choices for designing and synthesizing high-efficiency organic photovoltaic materials.Therefore,in this thesis,using DPP as the acceptor,two D-A type conjugated polymers were designed and synthesized,and they were studied.Optical properties and applications in the second region of the near-infrared.（1）The D-A type conjugated polymer PBDT-DPP was synthesized by using 2,6-dibromo-4,8-bis（5-（2-ethylhexyl）thiophen-2-yl）benzo[1,2-b:4,5-b’]dithiophene as the donor,DPP as the acceptor.The introduction of branches on the donor can reduce the interaction between molecules and water molecules.In addition,it can also reduce the fluorescence quenching caused by aggregation of polymer molecules,thereby increasing the quantum yield.After a series of characterization,the absorption peak and emission peak of PBDT-DPP are 757 nm and 938 nm,respectively,and the quantum yield is 0.46%.Under the irradiation of 660 nm laser,the maximum temperature of 100μg/m L PBDT-DPP can reach 60℃,and it has good photostability and can be used for photothermal treatment of tumors.In addition,PBDT-DPP can achieve liver and kidney enrichment in nude mice,and has good imaging effects.（2）Using 3,4-ethylenedioxythiophene（EDOT）as electron donor and DPP as acceptor,EDOT-DPP polymer was obtained through coupling reaction.EDOT can provide stronger electron donating ability,enhance the hole-electron transport ability,and reduce the molecular band gap,which has important reference value for the design and synthesis of NIR II fluorescent materials.The absorption peak and emission peak of the fluorescent molecule are 897 nm and 1107 nm,respectively.The maximum temperature of a 100μg/m L semiconducting polymer nanoparticle（SPN）aqueous solution under the irradiation of the laser(660 nm,1W·cm-1)can reach 60℃.Compared with the previously reported P-DPP（500μg/m L,52℃）,it has a better photothermal effect and realizes the photothermal therapy（PTT）of tumors in nude mice.By injecting into the tail vein of nude mice,and finally achieving enrichment in the liver and kidneys through blood circulation,nude mice have no adverse reactions,indicating that SPN has good biocompatibility and has good application prospects in bioimaging and photothermal therapy. |
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