Molecular Fluorescent Probes For Ions Detection And Cellular Imaging

Chapter 1:This chapter explained the concept and development of fluorometry.The composition of fluorescent probe and the effects of the fluorescence properties are introduced in brief.Furthermore,the principles of fluorescence sensors for ion recognition and the latest research progress in recent years are reviewed.Chapter 2:A facile Schiff-base ligand 8-hydroxyjulolidine-pyridyl hydrazone?L1?as the fluorescent probe was synthesized and characterized.L1 was selective toward Al³⁺ions with a visible color change from pale-to-yellow and fluorescence enhancement at 480?nm.L1 forms complex with Al³⁺in 1:1 ratio as supported by Job's plot analysis and ESI-MS.The binding mode was further confirmed by ¹H NMR titrations.The detection limit was calculated to be 8.22×10^-8?M for Al³⁺.Furthermore,the practical applicability of L1 has been examined in living cells.These merits of L1,i.e.,requiring facile one-step synthesis and displaying high sensitivity make L1 a promising candidate as a chemosensor for Al³⁺ion.Chapter 3:Anefficientfluoresceinbasedprobe,fluorescein-monoaldehyde-?2-pyridyl?hydrazone?L2?,for the dual sensing of Al³⁺and Cu²⁺has been synthesized and characterized.L2 was highly selective toward these two ions with different fluorescence signals and binding modes in two different media.In EtOH-H₂O?3:2,v/v;pH=4.0?,L2 selectively binds Al³⁺to form a 1:1 ligand/metal complex,giving rise to a visible pale pink-to-yellow color change and fluorescence enhancement at 440 nm,while in CH₃CN-H₂O?2:3,v/v;pH=7.2;1M KCl?,L2 and Cu²⁺form a 1:2 ratio complex,resulting in a color change from pink to orange-yellow and a significant fluorescence enhancement at 520 nm.The binding modes were confirmed by fluorescence,absorption,IR,ESI-MS and ¹H NMR titrations.The detection limits were calculated to be 7.32×10^-88 M and 1.47×10^-88 M for Al³⁺and Cu²⁺,respectively.Cell imaging studies demonstrate that this sensor is capable of sensing Al³⁺and Cu²⁺in living cells.Chapter 4:2-?1-Amino-2-anthraquinonyliminomethyl?phenol?L3?was facilely prepared as a spectroscopic probe by one step condensation between1,2-diaminoanthraquinone and salicylaldehyde.The complexation of Cu²⁺ions with L3 through 1:1 chelation resulted in a rapid pink-to-blue color change and significant quenching of the fluorescence at 604 nm in THF-H₂O?1:1,v/v;pH=7.4?.The subsequent addition of S^2-to this solution regenerated the initial spectrum of L3 as a result of L3 being released from the L3-Cu²⁺complex through a displacement mechanism,which makes L3 a dual-channel sensor for the naked eye detection of Cu²⁺and S^2-ions.The system has high selectivity toward Cu²⁺and S^2-ions even in the presence of other commonly coexisting ions and the detection limits were found to be 8.95×10^-88 M and1.36×10^-77 M,respectively.Applicability of L3 to detect Cu²⁺ions and S^2-ions in tap water has been demonstrated.Paper strips were fabricated for the detection of Cu²⁺and S^2-by the colorimetric method.Furthermore,L3 has been successfully applied for cell imaging studies.Chapter 5:A novel probe 3-benzyl-2-?N-ethylcarbazole-3-vinyl?-benzothiazolium bromide?L4?was synthesized and utilized for the specific detection of cyanide ions in DMSO-H₂O?3:2,v/v;pH=7.4?.This probe displays fast response through visible colorimetric and fluorogenic changes toward CN^-,allowing for ratiometric sensing of cyanide in aqueous media.The ratiometric response is due to the breaking of the extensive?-conjugation and the intramolecular charge transfer?ICT?by the nucleophilic conjugation addition of cyanide to L4,which is ascertained by NMR and ESI-MS analysis as well as density functional theory?DFT?calculations.The detection limit of CN^-?3.39×10^-77 M?is well below the limit recommended in the World Health Organization?WHO?guidelines for drinking water.Moreover,fluorescence co-localization studies demonstrate that L4 is a specific mitochondria-targeted fluorescent probe.Chapter 6:Summary and outlook.All the works in this dissertation are summarized.According to the research status and the development trend of fluorescence probes,the directions of the future research in this area are introduced.