Establishment Of High Sensitive Fluorescence Sensing System And Its Application In Environmental Analysis

With the development of society and the progress of scientific and technological,environmental problems are becoming increasingly prominent.It is of great importance to carry out effective detection and monitoring of environmental pollutants that cause environmental problems.The diversity of environmental pollutants,the existence of complex forms and the presence of pollutants in the presence of traceability require environmental detection methods more sensitive and reliable.Fluorescence sensing technology is widely used in the field of environmental science with its good sensitivity and selectivity.The goal and requirement of constructing a fluorescence sensing detection system is high sensitivity,selectivity and stability.In order to reduce the background interference,improve the signal-to-noise ratio and improve the sensitivity of fluorescence detection,the detection methods based on fluorescence probe and fluorescence sensor detection platform were studied in this dissertation.The main contents of this dissertation are as follows:(1)In Chapter 2:Based on the long-life fluorescence characteristics of terbium ternary complexes,the properties of nanoparticles(GNPs)on the fluorescence quenching of terbium complexes and the specific catalytic properties of Pb2+ for 17E DNAzyme,a label-free time-gated fluorescence method for Pbro detection was designed.Its signal can be measured in a time-gated manner which could eliminate most of the unspecific fluorescent background.It is well known that unfolded single stranded DNA(ssDNA)could be adsorbed on GNPs while double-stranded DNA could not.The cleavage of the substrate by the 17E DNAzyme in the presence of Pb2+ causes the release of ssDNA from the 17E-17S duplex to be absorbed onto GNPs,preventing the aggregation of GNPs and then leading to a fluorescence decrease of terbiumternary complex.By means of this method,the authors have successfully detected Pb2+ over a range of 10 nM to 2500 nM with a detection limit of 1.7 nM and R2 = 0.9889.The sensor also exhibited good selectivity.The method provided a simple,cost-effective,rapid and sensitive measurement tool for Pb2+detection.(2)In Chapter 3:Based on the long-life fluorescence characteristics of terbium ternary complexes,the properties of nanoparticles(GNPs)on the fluorescence quenching of terbium complexes and the lead(?)-driven DNA molecular device,a label-free time-gated fluorescence method for Pb2+ detection in environmental water bodies was designed.By means of this method,the authors have successfully detected Pb2+ over a range of 0.5 nM to 20 nM with a detection limit of 0.24 nM and R = 0.9977.The method is simple,rapid,with good sensitivity and selectivity.Using this method,the actual samples were measured and the results were satisfactory.The method could be used for the detection of low concentration Pb2+ in actual water bodies such as environmental water and tap water.(3)Chapter 4:Based on the selective adsorption of ssDNA and the separation and enrichment of magnetic graphene oxide(MGO),the fluorescence quenching properties of MGO and the lead(?)-driven DNA molecular device,a fluorescence method for Pb2+ detection in environmental water bodies was designed.The magnetic graphene synthesized by this experiment has the advantages of graphene oxide and magnetic Fe3O4,which is highly effective for quenching the fluorescent carrier and selectively adsorbing ssDNA,and beneficial to the enrichment and separation of the detection object.Using this method,the authors have successfully detected Pb2+ over a range of 0.5 nM to 25 nM with a detection limit of 1.1 nM and R=0.9988.The experimental results showed that the method had good sensitivity and excellent selectivity to common metal ions.The actual samples were measured and the results were satisfactory.(4)Chapter 5:This chapter described a fluorescent ratiometric sensor for water content determination in organic solvents.Two different compounds,4-N,N-dimethylamino-4-methylacryloylamino chalcone(DMC)and 5,10,15,20-tetra-(4-methylacryloylaminophenyl)porphyrin Zinc(TMAPPZn),were synthesized as indicators for fluorescence ratiometric water sensing.DMC is a fluorescence indicator with charge donor parts and acceptor parts and sensitive to solvent polarity and water content.The fluorescence intensity of TMAPPZn is insensitive to the water content lower than 10%(v/v)water content and employed as the reference indicator.The use of TMAPPZn as a reference indicator resulted in a more stable signal due to minimizing the effects of fluctuations of light intensity,fluorophore bleaching,background signal,and so forth.DMC and TMAPPZn were photo-copolymerized on the silanized glass surface to prevent leakage of the fluorescence indicators.Three organic solutions(ethanol,acetone,and tetrahydrofuran)were used to verify the performances of the proposed sensor,and the sensor exhibited a good linearity in the range 0-10%(v/v)water content with detection limits of 0.0097%,0.011%,and 0.017%for ethanol,acetone,and tetrahydrofuran,respectively.The ratiometric sensor was characteristic of satisfactory reproducibility,reversibility,short response time.The sensing membrane was found to have a lifetime of two month.We carried out preliminary spiking experiments on the actual samples,and the spiked recoveries were of 99.2-102.0%.(5)Chapter 6:Two different compounds,2-allyl-6-((2-aminoethyl)amino)-1H-benzo[de]isoquinoline-1,3(2H)-dione(AAEAN)and 5,10,15,20-tetra-(4-methylacryloylaminophenyl)porphyrin Zinc(TMAPPZn),were synthesized as fluorescent indicators for the fabrication of a fluorescence ratiometric pH sensor,and were covalently bonded to silanized slides.The fluorescent ratiometric sensor effectively eliminated the interference caused by the change of equipment conditions and the external environment,and improves the accuracy of the numerical measurement of fluorescence.By means of this method,the authors have successfully detected pH over a range of 5.50 to 9.50.The covalent immobilization of the fluorescent carrier is effective in preventing the loss of sensitive substances,resulting in a stable sensor with a lifetime of up to one month.The sensor exhibited good sensitivity,selectivity,reproducibility,and the response time is less than 90s.Using the proposed sensor,we conducted a controlled experiment on the actual sample and the results were satisfactory.(6)Chapter 7:This chapter described an internal reference fluorescent sensor for pH determination.The fluorescent carrier contained two pH-dependent fluorophores,2-allyl-6-((2-aminoethyl)amino)-1H-benzo[de]isoquinoline-1,3(2H)-dione(AAEAN)and meso-5,10,15,20-tetra-(4-aminophenyl)porphyrin(TAPP),that were derived from naphthalimide derivatives and porphyrin derivatives respectively.The two fluorophores acted as reference fluorophores for each other.The fluorescent carrier was copoly-merized on the silanized glass surface for an internal reference pH sensor.The sensor showed satisfactory selectivity,reproducibility as well as sufficient stability and fast response time.It covered a broad dynamic range of pH value 1.00-9.50.The sensor provided an alternative concept to apply the fluorescence carrier with two fluorophores for the development of internal reference sensors covering a broad range of pH value.Using the proposed sensor,we conducted a controlled experiment with the actual sample and the results were satisfactory.The synthesis of one fluorescent carrier with two properly selected fluorophores paved the way to construct a series of internal reference sensors.