基于CdTe@SiO纳米粒子和金纳米粒子体系荧光能量转移的开光模式检测三聚氰胺

1、Effcient Fluorescence Energy Transfer System between CdTe-Doped Silica Nanoparticles and Gold Nanoparticles for Turn-On Fluorescence Detection of MelamineFeng Gao,* Qingqing Ye, Peng Cui, and Lu Zhang INTRODUCTION In recent years, a number of analytical methods have been developed for the determinat

2、ion of melamine.l liquid/gas chromatographyl mass spectrometry,l liquid/gas chromatography coupled with mass spectrometryl enzyme-linked immunosorbent assay(ELISA),l surface-enhanced Raman spectrometry,l electrochemical methods,l molecularly imprinted techniques l optical methods such as chemilumine

3、scence, colorimetric detection and fluorimetric methods Fluorimetric methods, offer many advantages such as High sensitivity, Simple instruments, Easy operation, The ability to measure multiple fluorescence properties. More especially, the fluorescence-based methods relying on fluorescence energy tr

4、ansfer (FET) techniques, which could occur when the emission spectrum of the donor and the absorption spectrum of the acceptor are appreciably overlapped to an extent. INTRODUCTION AuNPs：high extinction coefficientsact as efficient acceptors for most fluorophores CdTe QDs：tunable, narrow, and symmet

5、ric emission spectra and broad excitation spectraemployed as donors in FET systems SiNPs： can efficiently reduce the outer environmental interference with fluorophores use silica as the shell and fluorophores as the core INTRODUCTION Schematic Illustration of the Principle of “Turn- On” Fluorescence

6、 Detection of Melamine Based on Enhanced FET between CdTeSiO2 and Au NPs in Aqueous Solutiona INTRODUCTION MATERIALS AND METHODS Instrumentation. Materials. Synthesis of AuNPs. Preparation of CdTe-Doped Silica Nanoparticles (CdTeSiO2). Procedures for the Determination of Melamine. Instrumentation. L

7、S-55 fluorescence spectrophotometer (PerkinElmer Co.) UV-3010 spectrophotometer (Hitachi, Japan). Scanning electron microscopy (SEM) (Hitachi, Japan) Hitachi H-600 transmission electron microscopy (TEM) (Tokyo, Japan). pHS-3c pH meter (Shanghai, China).Materials. uChloroauric acid tetrahydrate (HAuC

8、l4H2O) Aladdin-Reagent Co. uTrisodium citrate Sinopharm Chemical Reagent Co., Ltd. (Shanghai, China).uTetraethylorthosilicate (TEOS) and ammonia solution (25%, w/w) Sigma. uTe powder (60 mesh, 99.999%) Alfa Aesar. uNaBH4, CdCl22.5H2O, and glutathione (reduced) Shanghai No. 3 Chemical Co. (Shanghai,

9、China).u Melamine Aldrich (United States). u The buffer solutions 0.01 M KH2PO4Na2HPO4. All other reagents were of at least analytical grade and used without any further purification. Doubly deionized water was used throughout.Synthesis of AuNPs.99.0 mL of triplex distilled water +1.0 mL of 1% (v/v)

10、 HAuCl4 solution vigorous stirringoil bathreflux for 20 mincooled to room temperature+5.0 mL of 1% (v/v) trisodium citrate solutionThe color of the solution changed from pale yellow to deep redAuNPs.Preparation of CdTe QDs100 mL of water stirring +0.057 g of CdCl22.5H2O + 0.192 g of GSHpH=8.3l.0 M N

11、aOHbubbling N2 for 30 min+200 L of 0.30M oxygen-free NaHTe solutionheated to 100 C oil bath for 4.5 hglutathione-capped CdTe QDsPreparation of CdTe-Doped Silica Nanoparticles (CdTeSiO2). 20 mL of ethanol + 0.5 mL of CdTe solution + 0.25 mL of TEOS +0.50 mL of 25% (m/m) NH3H2O stirringcentrifuging wa

12、shingUltrasonicationCdTeSiO2Procedures for the Determination of Melamine. 5.0 mL of raw milk or 5.0 mg of milk powder was placed into a 10 mL centrifuge tube, 1.5 mL of 2.0 M trichloroacetic acid was added Mixed with a vortex for 2 min to deposit protein in the sample matrix. The mixture was then ce

13、ntrifugated at 3500 g for 5 min. The obtained supernatants were transferred into another centrifuge tube Adjusted to pH 7.0 with a small amount of 5 M NaOH Filtered with a 0.22 m filter. Prior to use, the real samples were treated with trichloroacetic acidto remove proteins. 10 L of CdTeSiO2 (40 mg

14、mL1) + 7.0 mL of AuNPs (4.0 nM) +various amounts of melamine solutiondiluted to the mark with pH 6.50 buffer solutionstirringreacted for 30 min at room temperatureProcedures for the Determination of Melamine. The fluorescence intensities of the mixture solutions were measured at 561 nm with an excit

15、ation at 380 nm. RESULTS AND DISCUSSIONvMorphological and Spectral Characterizations ofAuNPs, CdTe QDs, and CdTeSiO2. vFluorescence Quenching Effect of AuNPs on CdTeSiO2vFluorescence “Turn-On” Assay of Melamine. vOptimization of Experimental Conditions for the Detection of Melamine.vDetection of Mel

16、amine.vEffect of Potential Interfering Substances. vAnalysis of Melamine in Real Samples.Morphological and Spectral Characterizationsof AuNPsTypical TEM images of AuNPs(a)Absorption spectrum of AuNPs(A)Morphological and Spectral Characterizationsof CdTe QDsTypical TEM images of CdTe QDs (b)Fluoresce

17、nce spectra of CdTe QDs (curve a, black line)Morphological and Spectral Characterizations of CdTeSiO2Typical TEM images of CdTe-doped silica nanoparticles (d) and SEM image of CdTe-doped silica nanoparticles (c).Fluorescence spectra of CdTe SiO2 nanoparticles (curve b, red line)Morphological and Spe

18、ctral Characterizationsof CdTeSiO2To compare the photostability of CdTeSiO2 with that of free CdTe, the photobleaching experiments were carried out by investigating the variation of fluorescence intensity over a long period of continuous intensive excitation of 500 s with a 150 W xenon lamp.spectrof

19、luorometer of CdTeSiO2 (curve a, black line) and CdTe QDs (curve b, red line)(A) Fluorescence spectra of CdTeSiO2 in the presence of various concentrations of AuNPs in 0.01 M phosphate buffer (pH 6.50). Fluorescence Quenching Effect of AuNPs on CdTeSiO2Stern-Volmerequation:I0/I = Ksv Q + 1I0/I = 2.4

20、3AuNPs (nM) + 1 (R = 0.9958)Fluorescence Quenching Effect of AuNPs on CdTeSiO2(B) Stern-Volmer plot of CdTeSiO2 nanoparticles quenched by AuNPs.The fluorescence quenching of fluorophores by AuNPs is dominated by different mechanisms such as the inner filter effect ,photoinduced electron transfer and

21、 FET including fluorescence resonance energy transfer (FRET) and surface energy transfer (SET)The fluorescence quench of CdTeSiO2 is more likely through energy transfer rather than electron transfer processes. Fluorescence spectra of (a) 0.04 mg/mL CdTeSiO2, (b)a + 0.01 M melamine,(c) a + 0.25 M mel

22、amine, (d) a + 2.8nM Au NPs, (e) a + 2.8 nM Au NPs + 0.01 M melamine, (f) a + 2.8 nMAu NPs + 0.25 M melamine in 0.01 M phosphate buffer (pH 6.50).Fluorescence “Turn-On” Assay of Melamine. Optimization of Experimental Conditions for the Detection of Melamine parametersmedia pH incubation time AuNPs c

23、oncentrationDetection of Melamine.(A) Fluorescence spectra of the CdTeSiO2-AuNPs system in the presence of different concentrations of melamine in 0.01 M phosphate buffer (pH 6.50).Inset: the enhanced fluorescence intensities as a function of the concentration of melamine(I I0)/I0 = 0.023 +0.0024c (

24、c: nM) R=0.9979Detection of Melamine.(B) Fluorescence spectra of the CdTe-AuNPs system in the presence of different concentrations of melamine. Inset: the enhanced fluorescence intensities as a function of the concentration of melamine (I I0)/I0 = 0.018 +0.0016c (c: nM) R=0.9867Effect of Potential Interfering Substances. potential interfering substancescommon