The Synthesis And Performanceresearch Of Fluorescent Probes Based On ?-diketone For Thorium Ions

Thorium,one of the most common radioactive metal elements distributed on the earth with variety of forms,is widely utilized in modern industry such as medical,agriculture,aerospace industry,nuclear industry.However,it has toxicity and radioactivity which would increase the risk of developing cancer of the lung,bone or pancreas even gene mutation if prolonged exposure to an environment containing thorium.According to the guidelines for drinking water quality 4th ed of the World Health Organization,the total radioactive level of thorium should lower than or equal to 0.1 Bq/L in drinking-water.As is known to all,trace thorium ions can enrich in individuals over many years through bioaccumulation and lead to many other diseases.Accordingly,the detection of trace thorium ions is particularly important,especially for living body.Many scientists have focused their interests on developing various convenient methods for the determination of thorium such as solid-phase extraction,ion-imprinted polymer,fluorescence spectrophotometric methods,electrochemistry.As we know,the main harm of thorium toxicity and radioactivity are internal exposure.There are many literatures related to thorium detection have been reported,but none for living cell imaging.Due to its advantages of rapidity,high selectivity,good sensitivity and low cost,fluorescent spectrophotometric methods were widely used in detecting metal ions in living cell and environment such as Al3+,Cu2+,Fe3+,Zn2+,Hg2+.Although a few fluorescent probe for Th4+ ions have been reported,there still exist some limitations,such as interference from other metal ions(especially UO22+,Lanthanide and actinide)and higher detection limits.In addition,Th4+ dissolves easily in water and the environment of living organisms is aqueous,but only few reported fluorescent probe for thorium operated well in aqueous solution.Thus,developing efficient fluorescent chemosensors with good solubility for Th4+ remains necessary.Recently,?-diketone ligands,as one of the most widely used ligands in coordination chemistry,which possess carbonyl groups capable of strong coordinating ability with metal ions.2-hydroxy-1-naphthaldehyde have ability to act as an acceptor in the excited-state intramolecular proton transfer(ESIPT)process / photoinduced electron transfer(PET)process and the sensors based on 2-hydroxy-1-naphthaldehyde after complexing with analyte had the characteristics of long fluorescence lifetime,high fluorescence quantum yield and extremely sharp emission bands.Inspired by this finding,we herein present a novel fluorescent sensor containing ?-diketone and 2-hydroxy-1-naphthaldehyde group for Th4+ ion.The probe possessed high selectivity and sensitivity,could be well applied to detect Th4+ ion in living cells and imaging.Therefore,this work have the potential value in the field of medical treatment and biological research.1.A fluorescent sensor Hn based on ?-diketone N1',N3'-bis((3-hydroxynaphthalen-2-yl)methylene)malonohydrazide for thorium ions was designed and investigated.The fluorescent sensor showed high selectivity in the present of other metal ions even UO22+.The binding mode of the sensor Hn with Th4+ was found to be 1:1 with association constant of 2.46×104 M-1 in CH3OH:H2O(v/v=2:8,p H=7.2)solution.There was linear relationship between the fluorescence intensity of Hn-Th4+ and concentration of Th4+ covering a range of 0.06?mol·L-1-1.0?mol·L-1 and the detection limit was 0.0344?mol·L-1.At the same time,the interaction mechanism between the sensor Hn and Th4+ was investigated by DFT calculations,the coordination mode and sites were confirmed from more than one optimization mathematical models for Hn-Th4+,and the fluorescent mechanism of Hn and Hn-Th4+ was discussed.Most importantly,this fluorescent sensor showed slight cytotoxicity and good cell-permeability,and was successfully utilized for the fluorescence imaging of Th4+ in living cells.2.A fluorescent probe Hc based on ?-diketone was synthesized.The fluorescence intensity was discussed after Hc reacting with Th4+ ions in CH3OH:H2O:H2O(v/v,5:5,p H = 7.5)solution.Experimental results showed that the linear relationship between the fluorescence intensity of Hn-Th4+ and concentration of Th4+ covering a range of 6?mol·L-1-14?mol·L-1(R2 = 0.96722)and the detection limit was 1.9928 ?mol·L-1.And the most appropriate time between probe Hc and Th4+ was 5 min after the probe Hc responding Th4+ ions.