Preparation Of Novel Fluorescent Nanomaterials And Application In Bio-environmental Analysis

The present work is concerned with novel fluorescent nanomaterial,such as quantum dots,metal nanoclusters and fluorescent carbon dots,and various fluorescent metal nanoclusters,carbon dots and ratiometric fluorescent nanocomposites were prepared.Their structures,stability and optical properties were studied.Several fluorescent sensors were developed for the detection of small biomolecules,heavy metal ions and enzymes.The interaction mechanism between fluorescent nanomaterial and target analytes was discussed,achieving sensitive and selective sensing platforms for the detection of target analytes in real samples.The main works are summarized as follows.(1)A sensitive,simple and cost-effective fluorescent method for the detection of arginine has been developed based on the inner filter effect(IFE)of citrate-stabilized gold nanoparticles(AuNPs)on the fluorescence of thioglycolic acid-capped CdTe quantum dots(QDs).When citrate-stabilized AuNPs were mixed with thioglycolic acid-capped CdTe QDs,the fluorescence of CdTe QDs was significantly quenched by AuNPs via the IFE.With the presence of arginine,arginine could induce the aggregation and corresponding absorption spectra change of AuNPs,which then IFE-decreased fluorescence could gradually recover with increasing amounts of arginine,achieving fluorescence"turn on" sensing for arginine.The detection mechanism is clearly illustrated and various experimental conditions were also optimized.Under the optimum conditions,a decent linear relationship was obtained in the range from 16 to 121 ?g L-1 and the limit of detection was 5.6?g L-1.And satisfactory results were achieved in arginine analysis using arginine injection,compound amino acid injection,even blood plasma as samples.(2)A novel approach for simple and sensitive determination of alkaline phosphatase(ALP)is developed on the basis of an inner filter effect of p-nitrophenylphosphate(PNPP)on the fluorescence of gold nanoclusters(AuNCs).AuNCs with a high quantum yield of 12%were synthesized by one-pot strategy and were directly applied as fluorescent substance.When AuNCs were mixed with PNPP,the fluorescence of the AuNCs was remarkably quenched or was decreased via the inner filter effect since the absorption spectrum of PNPP overlaps well with the excitation spectrum of the AuNCs.While in the presence of ALP,PNPP was catalytically hydrolyzed into p-nitrophenol,which has different absorption characteristics from those of PNPP,resulting in the recovery of the AuNCs fluorescence.Thus,a novel "turn-on" fluorescent sensor for detecting ALP was established with a detection limit as low as 0.002 U/L.The turn-on fluorescent sensor exhibits many merits such as high sensitivity,excellent selectivity,and high signal output because of the low background signals.In addition,the developed sensing method was successfully applied to investigate ALP inhibitors and ALP determination in serum samples.A good linear relationship was obtained in the range from 0.02 to 50 U/L,and satisfactory recoveries at four spiking levels of ALP ranged from 95%to 106%with precision below 5%.(3)A novel ratiometric fluorescent sensor,based on carbon dots(CDs)and gold nanoclusters(AuNCs),is developed for highly sensitive and selective visual colorimetric detection of Cu2+ and alkaline phosphatase(ALP).The ratiometric fluorescent sensor was synthesized by covalently linking 11-mercaptoundecanoic acid(11-MUA)stabilized AuNCs to the surface of amino functionalized CDs/SiO2 nanoparticles.The red fluorescence of the AuNCs can be quenched by Cu2+ owing to coordination between Cu2+ and 11-MUA;however,the blue emission of the CDs was insensitive to Cu2+ owing to the protective silica shell.The quenching of the AuNCs fluorescence returned when PPi was added because of the higher affinity between Cu2+ and PPi than that between Cu2+ and 11-MUA.In the presence of ALP,PPi was catalytically hydrolyzed into phosphate(Pi),which showed a much weaker affinity for Cu2+.Thus,Cu2+ were released,and the fluorescence of the AuNCs was quenched once more.Based on this principle,Cu2+ and ALP could be simultaneously detected.The developed ratnometric fluorescent sensor could detect Cu2+ over a range from 0.025 to 4?M with a detection limit of 0.013 ?M,and ALP over a range from 0.12 U/L to 15 U/L with a detection limit of 0.05 U/L.The present method was successfully applied to detection of Cu2+ and ALP in real water samples and in human serum samples,respectively.