Fluorescence Sensing Of Electrosynthesized Fused-ring Aromatic Polymers In Water/Alcohol Solution

The last three decades have witnessed a dramatic expansion in the field ofconjugated polymers （CPs） as a consequence of their fascinating physical/chemicalproperties and application to fluorescent sensors. In comparison to small moleculefluorescent sensors, CPs based fluorescent sensors as modern sensory systems notonly benefit signal amplification, simplicity of use, easy fabrication into devices, andcombination of different outputs, but also improve the simplicity, selectivity, andsensitivity of ions or/and biological species detection due to "molecular wire effect".Recently, water/alcohol （environmentally friendly solvents） soluble fluorescent CPshave been widely used as optical sensing platforms for highly selective and sensitivedetection of different species, especially biologically active species such as organism,tissue, cell, and biomacromolecules （DNA, RNA, protein, and enzyme） andfluorescent imaging in vivo and at the cellular level. The commonly employedreactions for the synthesis of CPs are known as palladium-catalyzed couplingreactions （Suzuki, Heck, and Sonogashira）, Wessling reaction, topopolymerizationreaction, and FeCl3oxidative polymerization. As a useful and widely appliedtechnique, electrosynthesis of CPs is still far from mature, and there is little researchfocused on this filed. So it is very necessary to further explore and investigateelectrosynthesized CPs for fluorescent chemosensors. This dissertation is comprisedof the following four parts:1. Water-soluble poly（9-aminofuorene）（P9AF） was facilely synthesized by thedirect electropolymerization of commercially available monomer9-aminofuorene inboron trifuoride diethyl etherate （BFEE）, and its preliminary application as afuorescent chemosensor for the highly selective and sensitive detection of Fe³⁺andinorganic phosphates （Pi） in an organic buffer2-[4-（2-hydroxyethyl）-1-piperazinyl]ethanesulfonic acid （HEPES）（pH7.0） wasinvestigated. On binding to Fe³⁺, exceptional fuorescence quenching of P9AFoccurred. P9AF-Fe³⁺complex exhibited high sensitivity and rapid response to Pi withturn-on fuorescence. The working mechanism was proposed and confrmed by transmission electron microscopy. The determination of Fe³⁺in real samples and theinteraction of P9AF with Fe³⁺and Pi in living cells were investigated with satisfyingresults.2. P9AF was facilely electrosynthesized in BFEE as an efficient fluorescentsensing material for the detection of AcO^-in HEPES （pH7.4） buffer. On binding toAcO^-, fluorescence quenching of P9AF was demonstrated by an approximately80%reduction in the fluorescence intensity, while no obvious fluorescence change couldbe observed in the presence of other common anions. A diversity of carboxylatescould be recognized at different levels by P9AF. Substituent groups in carboxylatesaffected the intermolecular interaction between carboxylates and P9AF. These couldbe explained by a possible mechanism that hydrogen-bonding were the main way ofintermolecular interactions between P9AF and carboxylates, which was furtherconfirmed by absorption spectra monitoring and density functional calculations.3. Water-soluble fluorescent poly（9-fuorenecarboxylic acid）（PFCA） wasfacilely electrosynthesized in BFEE, and its preliminary application as a fuorescentchemosensor for the highly selective and sensitive detection of Fe³⁺in ethanol.Different compounds existing in agricultural crops and environments such ascommon metal ions, anions, natural amino acids, carbohydrates, and organic acidswere used to examine the selectivity of the as-fabricated sensor, and no obviousfluorescence change could be observed in these interferents and their mixtures. Apossible mechanism was proposed that the coordination of PFCA and Fe³⁺enhancedthe aggregation of polymer chains, which led to a significant quenching of PFCAemission, and this was further confirmed by absorption spectra monitoring andtransmission electron microscopy.4. Ethanol-soluble fluorescent polybenzanthrone （PBA） was facilelyelectrosynthesized in the binary solvent system containing of acetonitrile and BFEE."On-off" type fluorescent sensor based on this polymer for highly selective, sensitive,and practical detection of Pd²⁺was designed. Different compounds existing inagricultural crops and environments such as common metal ions, anions, naturalamino acids, carbohydrates, and organic acids were used to examine the selectivity ofthe as-fabricated sensor, and no obvious fluorescence change could be observed in these interferents and their mixtures. A possible mechanism was proposed that thecoordination of PBA and Pd²⁺enhance the aggregation of polymer chains, which ledto a significant quenching of PBA emission, and this was further confirmed byabsorption spectra monitoring and transmission electron microscopy. The Pd²⁺inagricultural crops and environment samples was determined facilely and efficientlyby using PBA-based fluorescent sensor.