Synthesis And Properties Investigation Of Water-soluble And Difunctional Fluorescence Probe

In recent years,fluorescence detection method has been widely applied in the field of environment detection and bioimaging due to its ease of operation,high sensitivity and real-time rapid analysis.Among them,water-soluble and multifunctional fluorescent probes,which can high selectively detect two or more analytes,has attracted increasing attention.In this paper,three novel water-soluble and difunctional fluorescent probes have been designed and prepared for highly sensitive and selective detection for Cu²⁺ and S^2-,pH and water content in tetrahydrofuran（THF）,hypochlorite（ClO^-）and temperature,respectively.The main contents and the results of this paper are as following:Firstly,based on fluorescence resonance energy transfer（FRET）,we have successfully synthesized a kind of water-soluble and difunctional fluorescent polymer probe（PF）via a facile one-pot method by covalent linking fluorescein isothiocyanate（FITC）with branched-polyethylenimine（b-PEI）.PF could selectively coordinate with Cu²⁺ to form PF-Cu²⁺ complex,resulting in fluorescence quenching through FRET mechanism.Furthermore,the in situ generated PF-Cu²⁺ complex can be used to selectively detect S^2-based on the displacement approach,resulting in an off-on type sensing.In addition,PF was successfully used to high sensitively detect Cu²⁺ and S^2-in human serum and tap water samples.Secondly,we successfully prepared a kind of red fluorescence carbon quantum dots（R-Cdots）with p-phenylenediamine through hydrothermal method.The fluorescence intensity of R-Cdots aqueous solution at 610 nm increases gradually with the increasing of pH from 2.0 to 9.0,and there is a good linear relationship between fluorescence intensity change（I/I0）at 610 nm and pH（5.0⁹.0）,implying that as-prepared R-Cdots can sensitively sense pH in complex biological sample.In addition,R-Cdots strongly present dependence of solvent polarity,its fluorescence emission wavelength displays red shift（⁸0 nm）with the increasing of polarity of solvent.With the increasing of water content in THF,the fluorescence emission wavelength displays red shift and decline of corresponding fluorescence intensity（from blue to red）,and the detection limit is as low as 0.04%（volume fraction）,indicating that R-Cdots can be used to sensitively detect water content of THF.Finally,a water-soluble and dual-responsive silica nanoparticle-based ratiometric fluorescent sensor（DRFS）has been developed by covalently linking rhodamine B isothiocyanate（RBITC）to the surface of fluorescent silica nanoparticle（FSNP）.When ClOadded into the DRFS system,the fluorescence intensity of FSNP（445 nm）decreased,while the fluorescence intensity of RBITC（576 nm）remained almost unchanged,can realize the highly selective and ratiometric detection of ClO^-.The as-prepared DRFS can not only determine ClO^-in human serum,but also image exogenous/endogenous ClO^-in living cells.Moreover,the as-prepared DRFS can also be used as a temperature sensor.With the increasing of temperature,the fluorescence intensity of RBITC（576 nm）decreased,while the fluorescence intensity of FSNP（445 nm）remained almost unchanged,and there is a good linear relationship between fluorescence intensity ratios（I576/I445）and temperatures ranging from 20 to 60 ?C,suggesting that DRFS can be severed as a good candidate for monitoring temperature changes in biological systems.