Preparation And Performance Study Of Novel FRET-mediated Photoswitchable Fluorescent Polymer Nanoparticles

There is a broad application potential of photoswitchable fluorescent polymer nanoparticles in the fields of optical anti-counterfeiting and information encryption,data storage,and ultra-high-resolution biological imaging,etc.Compared with traditional photoswitchable fluorescent organic small molecule-based systems,photoswitchable fluorescent polymer nanoparticles are preferred by scientists because of the following advantages:(1)high brightness and good photostability;(2)excellent biocompatibility when applied in complex biological systems;(3)strong functional modification.Based on this,in this thesis,two different photoswitchable fluorescence systems were constructed based on the principle of Fluorescence Resonance Energy Transfer(FRET).Their photoswitching performance was systematically studied,and were applied in biological imaging,information encryption,storage and other fields.The specific research contents are as follows:(1)By introducing two of the excited-state intramolecular proton transfer(ESIPT)fluorescent dyes: 4-methylphenol-benzothiazole(HBT)and 4-methylanilinyl-benzothiazole(ABT),and photochromic 2-(3’,3’-dimethyl-6-nitrospiro[benzopyran-2,2’-indoline]-1’-yl)octyl-methacrylate(SP8MA)into PMMA nanoparticles,a series of novel photoswitchable multicolor fluorescent polymeric nanoparticles based on FRET were synthesized via one-step miniemulsion polymerization method.Under the alternating irradiation of 365 nm ultraviolet light and 525 nm visible light,the polymer nanoparticles exhibit multicolor(blue,green,cyanine,red),switchable,tunable,and distinguishable fluorescence through selective FRET occurred between donor-acceptor.The emission signals demonstrate their application potential in the fields of information encryption and anti-counterfeiting,erasable fluorescent patterns,etc.,and are expected to play an important role in information security and data storage.(2)Based on the mechanism of FRET,the molecule with photochromic property,4,4’-((perfluorocyclopent-1-ene-1,2-diyl)bis(5-methyl-thiophene-4,2-diyl))bis(methylene)diacrylate(DTEDA),and red fluorescent dye with excellent quantum yield,5,6,12,13-tetra(4-(tert-butylphenoxy)-3,4,9,10-perylene tetracarboxylic anhydride(4-B-PDI),were incorporated into polymer nanoparticles.Meanwhile,the fluorescence quantum yield of 4-B-PDI in the polymer nanoparticles were optimized by changing the ratio of the polar monomer methyl methacrylate and the flexible monomer butyl acrylate in the matrix.Under the alternating irradiation of 254 nm ultraviolet light and 525 nm visible light,the fluorescence of the nanoparticles exhibits reversible switching between red and quenching due to the selective occurrence of FRET,and has excellent optical switching cycle performance,thermal stability,long-term stability and photostability.It demonstrates the broad application prospects in the fields of rewriteable patterns,and biological imaging.