Design And Synthesis Of (Poly)ionic Liquids Modified Organic Sensing Probes And Their Performances In Recognition Of Ions

The sensing probes based on organic chromophores or fluorophores have been markedly investigated for the recognition and determination of heavy metal ions owing to their operational simplicity,high sensitivity,and cost-effectiveness.However,most of these sensing probes（e.g.,rhodamine hydrazone derivatives）are strongly hydrophobic and only function in a medium of pure organic solvent or an aqueous solution containing a significant amount of organic co-solvent,which greatly limits their potential applications in ion detections,especially for analyses of biological samples.The combination of organic probe molecules with hydrophilic groups（phosphonates,galactose,etc.）or hydrophilic materials（eg hydrophilic polymers,silica,etc.）can improve the hydrophilicity of the probes,allowing them to be applied in a high proportion of water even pure water system.Nevertheless,most hydrophilic groups or materials reported are not sufficiently hydrophilic or contain non-specific binding sites,which limit the ability of hydrophilicity enhancement and may reduce the detection sensitivity of the probe.In view of the shortcomings of current hydrophilic groups or materials,this thesis proposes the use of（poly）ionic liquids（ILs and PILs）with excellent hydrophilicity and non-specific binding sites as carriers for modifying organic probe molecules,and the（poly）ionic liquids grafted organic molecule probes were synthesized and applied to recognition ions in pure aqueous.On the basis,this thesis chooses hydrophobic"star probe molecules"-Rhodamine derivatives as model probes,and modified with quaternary ammonium,imidazole ILs or PILs,respectively.Thus,a series of（poly）ionic liquids grafted organic molecule probes with high hydrophilicity and excellent sensing performance were developed and used for the detection and adsorption of heavy metal ions,focusing on the ion recognition performance.The main contents are summarized as following:1.In chapter 1,the optical chemosensing,common types of optical sensing probe and（poly）ionic liquids（ILs and PILs）were reviewed.The strategies hydrophilic modification of organic probe molecules and the advantage of ILs and PILs as hydrophilic groups or carriers were highlighted.2.In chapter 2,we designed a novel ionic liquid grafted probe IMI-SARhBH with imidazole-based ionic liquid as the hydrophilic group and applied it to the colorimetric detections and individual identifications of Cu²⁺and Al³⁺in 100%aqueous solutions.Specifically,we intend to integrate highly hydrophilic imidazolium chloride ionic liquid（IMI）with salicylaldehyde rhodamine B hydrazone（SARhBH）signaling unit to form a new water-soluble probe-liquid-grafted salicylaldehyde rhodamine B hydrazone（IMI-SARhBH）.The molecular structure of IMI-SARhBH was identified by ¹H NMR,¹³C NMR,and ESI–MS techniques.The IMI-SARhBH probe exhibited high selectivity for Cu²⁺and Al³⁺in pure aqueous media over other relevant metal ions with very low detection limits(i.e.,Cu²⁺:0.08μmol L^-1;Al³⁺:0.13μmol L^-1).Particularly interestingly,the response time for sensing detections of Cu²⁺and Al³⁺was found to be significantly different,i.e.,less than 1 min for Cu²⁺and more than 5 h for Al³⁺.By systematically investigating the differential recognition behaviors of IMI-SARhBH toward Cu²⁺and Al³⁺and understanding the role of the grafted ionic liquid during the binding events,we established a new and convenient method for individual identifications of Cu²⁺and Al³⁺from Cu²⁺–Al³⁺-coexisted solution.Moreover,an“electrostatic repulsion-induced difference in response time”mechanism was accordingly proposed.3.In chapter 3,we designed a novel PIL grafted organic molecule probe（RhBHSA-co-META）and applied it to the colorimetric detection of Cu²⁺in pure aqueous solution,and further the pre-formed P（RhBHSA-co-META）–Cu²⁺complex demonstrated to be competent for colorimetric determination of CN^-.Specifically,the synthesis of polymerizable salicylaldehyde rhodamine B hydrazine（RhBHSA）involves three steps using the low-cost rhodamine B（RhB）as the starting reagent.Next,the copolymerization reaction of RhBHSA with ionic liquid monomer META was conducted to synthesize P（RhBHSA-co-META）.The structure of RhBHSA was identified by ¹H NMR,¹³C NMR,and ESI–MS analyses,and the structure of P（RhBHSA-co-META）was identified by GPC,FT-IR,and UV-Vis analyses.In significant contrast to previously reported hydrophilic copolymer probes,only a low molar ratio of META to RhBHSA（i.e.,1:1）was used.The resulting P（RhBHSA-co-META）was found to be favorably and instantaneously dissolved in pure water.Moreover,upon the addition of Cu²⁺,the color of the P（RhBHSAco-META）solution would significantly change from colorless to pink within 3 s,indicating ultrafast response rate.And the detection method toward Cu²⁺was accordingly established,giving a LOD value of 0.15μmol L^-1.Excellent selectivity was also verified in the presence of other competitive metal ions.Furthermore,the pre-formed P（RhBHSA-co-META）–Cu²⁺complex was also verified to be highly efficient for colorimetric determination of CN^-,exhibiting high sensitivity and selectivity.4.In chapter 4,we designed a CL-PIL grafted organic molecule probe P（RhBHSA-BVD）and demonstrating its usefulness for recognition,quantitation,and selective removal of heavy metal ion in pure aqueous solutions.Specifically,P（RhBHSA-BVD）was synthesized through the crosslinking polymerization of the polymerizable salicylaldehyde rhodamine B hydrazone（RhBHSA）and the ion liquid crosslinking agent BVD.Both molecules were identified by FT-IR,¹H NMR,¹³C NMR,and ESI–MS analyses,and the structure of P（RhBHSA-BVD）was identified by SEM,TG,and FT-IR analyses.As expected,the resulting hybrid material exhibited a good dispersibility in pure water.More importantly,the P（RhBHSA–BVD）showed high specificity and selectivity in response to Cu²⁺,and these results could be easily monitored by naked eye.The detection method toward Cu²⁺was accordingly established,giving a LOD value of 0.15μmol L^-1.Moreover,the P（RhBHSA–BVD）could serve as an efficient adsorbent for Cu²⁺removal,which exhibiting high selectivity,satisfactory adsorption capacity(19.03 mg g^-1),and excellent reusability.Based on these results,P（RhBHSA–BVD）could be applied for qualitative/quantitative analysis and selective removal of Cu²⁺.5.In chapter 5,we designed a novel zwitterionic PIL grafted organic molecule probe P（RhBHSA-co-SPE）and applied it to the colorimetric detection of Al³⁺in pure aqueous solution,and further the pre-formed P（RhBHSA-co-SPE）–Al³⁺complex demonstrated to be competent for colorimetric determination of pyrophosphate（PPi）.Specifically,P（RhBHSA-co-SPE）was synthesized through the copolymerization reaction of the polymerizable salicylaldehyde rhodamine B hydrazone（RhBHSA）and the zwitterions ionic liquid monomer SPE.The structure of P（RhBHSA-co-SPE）was identified by FT-IR and UV-Vis analyses.In significant contrast to previously reported hydrophilic copolymer chemosensors,only a low molar ratio of SPE to RhBHSA（i.e.,1:1）was used in our synthesis.The resulting P（RhBHSA-co-SPE）was found to be favorably and instantaneously dissolved in pure water.More importantly,the P（RhBHSA-co-SPE）showed high specificity and selectivity in response to Al³⁺.The detection method toward Al³⁺was accordingly established,giving a LOD value of2.5×10^-8 mol L^-1.Furthermore,the pre-formed P（RhBHSA-co-SPE）–Al³⁺complex was also verified to be highly efficient for colorimetric determination of pyrophosphate（PPi）exhibiting high sensitivity and selectivity.