Construction Of Novel Ratiometric Fluorescence Sensing System And Its Application In The Detection Of Dopamine And Metal Ions

The pollution of heavy metal ions in the environment seriously threatens the human health.At the same time,concentrations of some neurotransmitters in biological fluids,such as dopamine,will have effect on human health.Recent years,many methods have been reported to detect heavy metal ions and dopamine.Fluorescence methods,as one of simple and sensitive methods,has been widely applied.Compared with the single emission fluorescent probe,the ratiometric fluorescent probe has obvious advantages in detecting the target through measure the ratio of multiple fluorescent signals.For example,the built-in correction function is used to eliminate the interference of external environment and improve the sensitivity of detection.The simultaneous detection of double targets is realized through triple emission modes.In addition,the ratiometric fluorescence probe enriches the color variation range of the probe to a certain extent.Combining it with smart phone for visual analysis not only greatly saves the analysis cost,but also facilitates the operation.Therefore,based on several common fluorescent nano materials,this paper constructs double emission ratiometric fluorescence sensing systems to detect dopamine(DA)and Cu2+ combining with smart phones,and realizes the simultaneous detection of Hg2+ and CO2+ by constructing a triple emission ratiometric fluorescence sensor.The specific contents of the paper are as follows:1.In this study,a rapid,selective and sensitive method was developed to detect dopamine(DA)based on inner filtration effect(IFE)between ratiometric fluorescence sensor and gold nanoparticles(AuNPs).The ratiometric fluorescence sensor was prepared by simple physical mixing green quantum dots(G-QDs)/red quantum dots(RQDs).DA could induce AuNPs aggregate via hydrogen-bonding interactions,and further changed the the absorption spectrum of gold nanoparticles to overlap with a certain emission spectrum of ratiometric fluorescence sensor.Due to the IFE,the dispersive AuNPs could quench the fluorescence of G-QDs,While the clustered AuNPs could quench the fluorescence of R-QDs.With the addition of DA,the color of ratiometric fluorescence changed from orange red to green.To simplify the detection process,a smartphone was employed to detecting DA in human urine by measuring RGB value of fluorescence color changes with a detection limit of 86 nM.This developed method has the advantages of simple operation,low cost and easy prevalence,thus provides a great promise for rapid detection of biomarker in biological samples.2.A smartphone-assisted fluorescence color sensing system for rapid,convenient,and on-site detection of copper ions was developed.The ratiometric fluorescence sensor was fabricated by using silica-coated blue-light-emitting carbon dots and surfacegrafted red-light-emitting cadmium-telluride quantum dots.After exposure to Cu2+in 20 s,the red fluorescence was quenched obviously,while the blue fluorescence remained unchanged,and the sensor color changes continuously from red to blue under the ultraviolet lamp.The concentration(50-1200 nM)of copper ions could be measured by the fluorescence spectrum(excitation at 360 nm,dual-emission at 441 and 640 nm)with a detection limit of 7.7 nM.The fluorescence colors were converted to digital RGB values to calculate the concentration of copper ions by a smartphone with a detection limit of 9.6 nM.The method was applied to detecting copper ions spiked in real samples with recovery from 97.9 to 108.0%and RSD from 3.8 to 8.9%.Thus,this convenient and practical fluorescence color sensing system presents a new strategy for rapid,sensitive,and on-site determination of copper ions in environmental or biological samples.3.A ternary emission ratiometric fluorescence sensor was developed for simultaneous detection of mercury(Hg2+)and cobalt ions(Co2+).The triple emission ratiometric fluorescence is composed of blue-emission CDs@SiO2,green-emission GSH-AuNCs and red-emission CEW-AuNCs.The system displayed a maximal emission wavelength at 437 nm,485 nm and 613 nm.CDs@SiO2 as the photostable internal standard is insensitive to Co2+ and Hg2+.GSH-AuNCs was quenched by Co2+,CEW-AuNCs was quenched by Hg2+ and did not interfere with each other.Thereupon,the ratiometric fluorescence intensity 1485/1437 of the ternary emission linearly varied within 0-50 μM Co2+ with a sensitive detection limit of 50 nM.The detection limit of.Hg2+ by fluorescence spectrometer analysis can be as low as 150 nM,the ratiometric fluorescence intensity I613/I437 linearly varied within 0-50 μM Hg2+.Meanwhile,the ternary emission ratiometric fluorescence sensor had high selectivity and high disturbance rejection ability.Moreover,the satisfactory recoveries of 101.7～103.2%and 100.2～105.2%in determining Co2+ and Hg2+ in water samples.The ternary emission ratiometric fluorescence sensor can relize simultaneous detection of two metal ions and provide a new method for fluorescence analysis of targets.