Research On Novel Spectral Probes For Fe³⁺with Excellent Comprehensive Performance

Fe3+exists in natural environment widely and plays an important role in ecological balance,so the real time detection of Fe3+is awfully significant.Spectral probes stand out from many detection methods of Fe3+due to their advantages such as simple operation,great selectivity,high sensitivity and non-destructive.However,spectral probes for Fe3+ with excellent comprehensive performance were extremely rare.Therefore,a small molecular fluorescent probe and four hyperbranched colorimetric and fluorescent polymeric probes for Fe3+ were designed and synthesized using 1,8-naphthalimide and rhodamine as chromophore and fluorophore.The structure of these probes was characterized and their performance as Fe3+probes was carefully studied by UV-vis absorption and fluorescence spectra.The details include:(1)Turn-on small molecular fluorescent probe for Fe3+(PPBN):A novel 1,8-naphthalimide derivative PPBN was synthesized by 1,8-naphthalimide and 1-(2-pyridyl)pIperazine serving as reporter and receptor,respectively.The structure of PPBN was characterized by H NMR,13C NMR,FT-IR spectra and elemental analysis.In DMF/H2O(75/25,v/v),Fe3+ caused a 15.8-fold fluorescence enhancement.The fluorescence intensity of PPBN at 530 nm showed good linear relationship with the concentration of Fe3+in the range of 60-140 ?M and the detection limit to Fe3+was 8.1×10-8 mol/L.PPBN could be used to detect Fe3+in a pH range of 5.5-7.3 without apparent interferences from other common metal cations.The response of PPBN to Fe3+was reversible.PPBN bound Fe3+by a 1:1 mode with a bonding constant of 4.41×103 M-1.The N atoms of pyridine and piperazine in PPBN chelated with Fe3+resulting in the fluorescence enhancement and this sensing mechanism was supported by FT-IR spectra.(2)Turn-on hyperbranched colorimetric and fluorescent polymeric probes for Fe3+(PGMN(2-5)):Four hyperbranched polymeric spectral probes PGMN2,PGMN3,PGMN4 and PGMN5,for short PGMN(2-5),were synthesized by rhodamine B,polyethylene polyamine,methacrylate monomer and chain transfer.According to the structure characterization data from 1H NMR and GPC,it was estimated that each of PGMN(2-5)contained about 4-5 rhodamine units,which was consistent with the design idea of achieving low fluorophore-content polymers.In CH3CN/H2O(75/25,v/v),PGMN(2-5)could monitor Fe3+ with high selectivity and sensitivity,reflected in appearing new absorption peaks around 558 nm in the UV-vis absorption spectra,distinct red shift of maximal fluorescence wavelength from 545 nm to 578 nm,obvious 33-35 folds enhancement in fluorescence intensity and 8.3-12.8 times increasement of fluorescence quantum yield.The absorbance around 558 nm and the fluorescence intensity around 578 nm showed linear relationship with the concentration of Fe3+in the range of 40-200 ?M and the detection limits were micromole level.The process of PGMN(2-5)detecting Fe3+was reversible and free from disturbing of other common metal cations.PGMN(2-5)could be used in the pH range of 5.0-7.5 and they could be applied in detecting Fe3+ in environment water samples.