Organic Fluorescent Ion Based On Nitrogen Heterocycles

Ions exist widely in nature and human body and play an important role in industrial production,daily life and normal operation of biological organism.Therefore,how to quickly detect multiple target ions with high selectivity and sensitivity has become an important research topic.At present,the traditional methods of ion detection include:atomic absorption or emission spectroscopy?AAS/AES?,plasma mass spectrometry?icp-ms?,anode/cathode stripping voltammetry,capillary electrophoresis,etc.Because of the need for expensive instruments,complex sample pretreatment,professional trained testers and so on,these testing methods can not fully realize fast and convenient real-time ion detection.In recent years,more and more researchers have paid attention to fluorescence probe,which has the advantages of high sensitivity,few samples,simple operation and on-the-spot monitor.Although many excellent fluorescent ion probes have been reported,there are some problems unsolved.Firstly,the common fluorescent probes consist of the appropriate signal reporter group and the specific ion recognizing group which are connected by covalent bond or non-covalent bond.Such molecular design often leads to complex synthesis processes;Secondly,most of the reported fluorescent ion probes are often specific to a single analyte.However,many physiological processes or chemical reactions involve the synergistic action of multiple analytes,so it is important to design dual-response or multi-response fluorescent probes.Finally,most of the fluorescent ion probes reported so far are for solution detection,which cannot be used repeatedly and cannot be carried easily.In addition,the common methods of preparing film,such as drop coating,dip coating,spin coating,self-assembly and hot evaporation,have some problems in morphology regulation,film stability and material loss.To solve the above problems,this paper carries out the following work:1.We designed and synthesized a series of azacyclic blue light D-A molecules T1,T2 and T3.They used triazoles as receptors and trianiline as donors which was connected at different sites of triazoles.For series of molecules,triazole is not only the ion recognition group,but also an important part of the signal display group,which greatly simplifies the design and synthesis of molecules.When triazole complexed with Fe³⁺,the emission intensity and maximum emission wavelength both changed because of the intramolecular charge transfer.This phenomenon greatly reduces the errors and interference caused by single signal recognition.In addition,we analyzed the charge transfer performance and fluorescence sensing performance of the three molecules that introduced triphenylamine at different connection sites of triazole and found that the charge transfer characteristics of the molecules is related to the connection site of triazole.In addition,we also found that the fluorescence sensing performance of the molecule was positively correlated with the charge transfer performance.Among the three moleculars,T3 had the best sensing performance,followed by T1 and finally T2.These findings may provide references for the future design of D-A azacyclic fluorescent ion probe.2.We synthesized BP1 and BP2 by directly connecting anthracborate or anthracene with tripyridine.Because tripyridine contains three nitrogen atoms,it is easier for coordination with ions.Therefore,there are many reports of fluorescent probes based on tripyridine.However,there are still some improvements in the fluorescence ion sensing of tripyridine,such as water solubility,fluorescence brightness and selectivity.Firstly,the introduction of borate groups not only ensures the water-solubility and fluorescence brightness of the fluorescent probe,but also improves the sensitivity and selectivity of the fluorescent probe.Secondly,Cu²⁺and HS^-can be identified by fluorescence off-on mechanism.When Cu²⁺was added,the fluorescence of BP1 and BP2 was blue-shifted and quenched.Then,after the complexation of BP1 and BP2with copper ions by 1:1 and the addition of HS-,the fluorescence spectrum of BP1-Cu²⁺,BP2-Cu²⁺were both enhanced by about 48 times.These findings may provide guidance for the design of highly sensitive,water-soluble organic fluorescence probe.3.We designed and synthesized G2,a second-generation dendritic molecule,with pyrene as the core and n-phenylcarbazole as the branch.Firstly,in solution detection,we can achieve the detection of I^-,Fe³⁺and Hg²⁺by fluorescence/colorimetric double channels.The fluorescence of G2 can be quenched by I^-and Fe³⁺,while the fluorescence of G2-I^-can be recovered by adding Hg²⁺.In addition,after the addition of I^-,the color of G2 solution changed from colorless to yellow.Then,after the addition of Hg²⁺,the color of G2 solution changed from yellow to colorless.Adding other metal ions does not yield these interesting colorimetric properties.Secondly,the fluorescence films of G2 were prepared by electropolymerization?EP?,which overcame the swelling effect of ordinary spin or drip coated films and showed good repeatability and sensitivity.Finally,G2 showed stable and efficient sensing performance in both realworld water samples and nematodes,which provides a good technical guarantee for practical detection applications in the future and also provided a good design idea for multifunctional and highly sensitive fluorescent film probe.