Design And Synthesis Of Fluorescent Probes With Large Conjugated Structure And Their Response To Heavy Metals (Hg²⁺、Au³⁺、Pd⁰)

Heavy metal Hg²⁺is widely present in water and easily enriched in soil.Au³⁺and Pd⁰ frequently occur in various water,and have high immune toxicity.Fluorescent detection technology has the advantages of simplicity,portability,low cost,high sensitivity,high selectivity,and non-destructive imaging,etc.Large conjugated fluorophores can effectively expand the delocalized electron range of fluorescent probes,increase light absorption efficiency,generate two-photon absorption capacity,and improve fluorescence performance,which is conducive to the detection of heavy metals.Therefore,this thesis designed and prepared new fluorescent probes DH(Dicoumarin probe for Hg²⁺),DA(Dicoumarin probe for Au³⁺),and HLAP（Hydroxyl linked-anthocyanin probe for Pd⁰）using large conjugated fluorophores 3-hydroxydicoumarin and hydroxy-linked anthocyanins,for the detection of Hg²⁺,Au³⁺,and Pd⁰,respectively.The detection properties of the fluorescent probes for target metal ions were studied,and their detection mechanisms were elucidated,the detection abilities of actual environmental samples were investigated and compared with similar probes.The main contents are as follows:1.A fluorescent probe DH for the detection of Hg²⁺in water and soil was designed and synthesized using 3-hydroxybiscoumarin as the fluorescent group and phthalate as the recognition group.Using desulfurization and hydrolysis reactions with Hg²⁺to block the photoinduced electron transfer（PET）process,DH produced yellow fluorescence off-on and changed the colorimetric from colorless to light yellow,forming a colorimetric fluorescence dual mode detection system.It had a good linearity in PBS buffer,with a detection limit as low as 85.25 n M,and the detection precision was 0.7112%.In environmental water samples,the linearity of Hg²⁺titration was good,and the detection recovery rate was 104.7%～108.6%.A rapid detection method for available Hg²⁺in soil had been developed.Through simple pretreatments such as hand shaking and filtration,the detection recovery reached 85.83%,and the detection limit was 34.48 mg/kg,which could be used for in-situ rapid detection of heavily contaminated soil with Hg²⁺.2.A fluorescence probe DA was designed and synthesized using 3-hydroxybiscoumarin as the fluorescent group and dimethylaminothiocarbamate as the recognition group for the detection of Au³⁺in water and cells.DA exhibited a yellow fluorescence off-on of Au³⁺in PBS buffer,with excellent quantitative linearity,wide detection range,detection limit as low as 27.60 n M,and detection precision of 1.650%,with excellent selectivity and competitiveness.The quantum yield of the probe was 25times higher than before the reaction,and the two-photon absorption cross section reaches 82.4 GM,and the DA had lower background fluorescence and higher stability than DH.In environmental water samples,the detection linearity of Au³⁺was excellent,and the detection recovery rate was 95.16%～99.63%.Considered the biological toxicity of Au³⁺,the cytotoxicity of DA was discussed and the fluorescence imaging ability for exogenous Au³⁺in cells was verified.3.The fluorescent probe HLAP was designed and synthesized using hydroxy-linked anthocyanins as the fluorescent group and allyl carbonate as the recognition group.The red fluorescence off-on was generated through the Tsuji-Trust reaction catalyzed by Pd⁰ and PET blocking.The probe exhibited high selectivity for Pd⁰ and could distinguish between other valence palladium states,with a detection limit as low as 0.1577μM,and a detection precision of 4.970%in acetone:water（1:1）.Hydroxy-linked anthocyanins have higher quantum yields（56.93%）and two-photon absorption cross sections（381 GM）than 3-hydroxydicoumarins.Excellent linear detection of Pd⁰was achieved in environmental water samples,and the detection recovery rate was93.33%～103.8%.In addition to high solubility and long wave emission,HLAP could accurately image exogenous Pd⁰ in cells.Compared with similar probes,the three large conjugated fluorescent probes had excellent comprehensive fluorescence detection properties,which improve the fluorescence detection capabilities of Hg²⁺,Au³⁺and Pd⁰,respectively.It provides the efficient and convenient fluorescent probes for heavy metal detection in environmental research,and provides the certain theoretical reference for exploring the new probes.