Construction Of Sulfide Non-covalent Fluorescence Sensing Platform And Research On Its Sensing Performance

Traditionally,S2-is a highly corrosive pollutant.Once dissolved in water,it is easy to be hydrolyzed and produce more toxic HS-and H2S.Low concentration of H2S can cause irritation effect to mucous membranes,respiratory and central nervous system.Exposure to high concentration of H2S in a short time can cause dizziness,palpitation,convulsion,coma or even death.Recent scientific studies have found that H2S is the third gas messenger molecule after CO and NO,which plays an important role in modulation of blood pressure,regulation of cell growth,protection of myocardium and suppression of oxidative stress.Abnormal endogenous H2S level is also associated with many human diseases,such as Alzheimer’s disease,Down’s syndrome,hypertension and liver cirrhosis.Therefore,it is of great importance to achieve real-time,rapid and sensitive detection of sulfide in aqueous solution and physiological conditions for the purpose of public safety,medical health and environmental monitoring.Among many developed methods for sulfide detection in water phase,fluorescence method has attracted wide attention due to its high sensitivity,good selectivity,simple operation and little damage to biological samples.At present,fluorescent sensors for sulfide are mainly divided into two types:displacement sensors and reactive ones.The displacement sensors have to interact with metal ions to form metal complexes before detecting sulfide ions.Thus,they suffer some drawbacks,such as,ease to get interference from other metal ions,poor selectivity and not suitable for the analysis in complex samples.Compared with the displacement sensors,the reactive type sensors have many advantages:(1)Less interference from metal ions and avoiding fluorescence quenching effect;(2)High selectivity endowed by the specific,reactive recognition sites;(3)Possibility of colorimetric responses due to the structural change of the probe.Considering that the ratiometric fluorescent probes have self-calibration function but are heavily dependent on organic synthesis,this dissertation proposed to develop ratiometric sensors based on non-covalent strategy for highly sensitive and selective detection of sulfide in aqueous solutions and real samples.In the first project,coumarin derivative(HCCA)and pyronine derivative(PyP)were chosen as recognization sites and signal output groups to construct a ratiometric sensing platform for selective detection of S2-in aqueous solutions based on non-covalent strategy.HCCA is found to provide fluorescent turn-on response to sulfide anion and PyP provides fluorescent turn-off response to hydrogen sulfide.Thus,the simply non-covalent mixing of the two compounds realized the construction of binary selective fluorescent sensing platform for sulfide anion in water phase.The optimized sensor system displays high sensitivity with a detection limit of 37 nM,and the detection process can be visualized through obvious color change from orange to blue under the illumination of 254 nm UV light or from red to colorless under room light.In addition,the non-covalent sensor platform can realize quantitative detection of sulfide anion in 10%urine,much interestingly,in which the selectivity is improved.To the best of our knowledge,the commercially available 7-hydroxy coumarin is the first time presented as a fluorescent sulfide anion sensor,and the HCCA-PyP combination provides a new,simple and efficient method for the detection of sulfide anion.In the second project,pyrene and pyronine were chosen as energy D-A pair to construct a non-covalent FRET sensing platform via the co-assembly strategy of surfactant aggregates to achieve ratiometric sensing of H2S.Based on the spectral regulation effect of the anionic surfactant SDS,cationic surfactant DTAB and neutral surfactant TX-100 aggregates on pyrene derivative Py-TOA-Py and pyronine derivative PyP,the FRET processes between these two probes in different surfactant aggregates were studied.In SDS micelle aqueous solution,FRET efficiency is the highest and the spectral change or visualization phenomenon is the most obvious.Combination with quantitative calculation of relevant parameters during FRET process,time-resolved emission spectroscopy and dynamic light scattering analysis,the influence from two factors(e.g.,the electrostatic interaction between surfactant and probes and aggregation state of surfactant)on the FRET process was explored.On this basis,we then studied the sensing behavior of FRET system regulated by SDS aggregates toward H2S.Its sensitivity is very low with the fluorescence change of PyP.Considering that the negative charges on the surface of SDS assemblies prevent the combination of H2S and PyP,cationic surfactant CTAB was introduced.The FRET system regulated by SDS/CTAB can realize the ratiometric sensing of H2S in aqueous solution,and the visualization phenomenon is obvious.The future plan is to test the selectivity of the system of Py-TOA-Py/SDS/CTAB/PyP to H2S,the sensing mechanism,and the sensing behaviors in human serum and urine.