Design,Synthesis And Properties Of Sulfonate Spiropyran Fluorescent Molecular Switches

Fluorescent molecular switches are widely used in fields such as anti-counterfeiting and encryption,optical information storage,sensor display,super-resolution fluorescence imaging,etc,due to their characteristics that they can change the fluorescent state under external stimuli.As a typical molecular switch,spiropyran have been extensively studied by researchers.However,traditional spiropyrans show"turn-on"mode fluorescence before and after stimulation,and the fluorescence color contrast is not obvious;on the other hand,traditional light control spiropyran use higher-energy ultraviolet light as the excitation light source.,and there are few reports on the use of visible light instead of ultraviolet light to control the negative photochromic spiropyran fluorescent molecular switch.Therefore,in this work,we hope to use different fluorophores to connect with sulfonic spiropyran with negative photochromic properties through chemical linkages to construct new types of fluorescent molecular switch.Stimulus response properties dominated by visible light control are investigated,and their practical applications are further explored.The main contents are as follows:In the second chapter,we constructed a new type of fluorescent molecular switch STS by covalently linking two sulfonic spiropyran molecules with the AIE fluorescent group tetraphenylethylene.The stimulus response properties of solution phase,solid powder,and polymer film state are studied.The molecular switch can not only respond to acid-base stimuli,but also can realize molecular ring closure through visible light control in solution.At the same time,the molecular switch incorporated PVP composite film exhibits emission change from orange-red to blue upon visible light trigger,and the reversible emission switch can be realized through heat treatment with good repeatability.Utilizing these properties,we further explored the application of the two-color molecular dye in the field of fluorescence information display and encryption.In terms of information encryption,the information has a high security level and specific and sequential stimuli were needed to decrypt,and the real information will be locked by illegal decryption.In the third chapter,we demonstrated a novel fluorescent molecular switch by single bond linking sulfonate spiropyran with a fluorophore pyrene.Compared with the fluorescent molecular switch substituted by TPE in second chapter,the fluorescent molecular switch not only realized the reversible conversion between red/blue emission in the film state,but also further realized the"turn-on"mode fluorescence in solution.Based on the above properties,its practical application was further explored.（1）The isomerization of MCSO₃HPy in solution can chelate specifically with Fe³⁺,which shows its application in the field of quantitative detection of Fe³⁺with a detection limit of 0.3μM.（2）two-color fluorescence conversion in the solid state was further used to demonstrate its use in fluorescence information display and anti-counterfeiting;（3）MCSO₃HPy was coated in amphiphilic polymer PSMA to prepare nanoparticles as biological fluorescence probe,and its two-color fluorescence imaging of cells was studied.