| Semiconductor nanocrystals (quantum dots, QDs) exhibit manyunique optical properties such as high fluorescence intensity，narrowemission line，wide stimulation spectral line，continuously adjustableemission wave length along with particle size， and resistance tophotobleaching, which can be exploited in optoelectronics andbiomedicine. Magnetic nanoparticles show some special magneticproperties corresponding bulk materials including superparamagnetism,lower Curie temperature, and higher susceptibility, which have beenwidely used in magnetic storage media, catalysis, magnetic separation,and biomedicine. Composite nanoparticles such as Fe3O4/Au、Fe3O4/SiO2、CdTe/SiO2unite all the excellent performance of singlenanoparticles, and have got considerable attention in analyticalscience and biomedicine. This study mainly focused on the synthesis offunctional nanoparticles and their application in food safety.1. Water-soluble CdTe quantum dots which show green、 yellow、and red fluorescence, respectively, were prepared in aqueous solutionusing3-mercaptopropionic acid as the stabilizer. The optimum reactiontemperature was105℃for the high quanlity QDs. The results showedthat these quantum dots had good optical properties. In addition, aseries of CdTe@SiO2-NH2composites with diameters ranging from160nm to470nm, were prepared by St?ber method via one-pot reaction.The largest amount of amine on the surface of composite fluorescencemicrospheres was detected when APTS were added30min after silicaparticle growth was initiated. The fluorescence quantum yield ofCdTe@SiO2-NH2particles was equivalent to previous CdTe QDs.Meanwhile, many physical and chemical properties of CdTe@SiO2-NH2particles such as water solubility, monodispersity, colloidal stability,chemical reactivity, and biocompatibility were excellent, which will widen the application of fluorescence labeling based on QDs.2. An improved thermal decomposition method was used todirectly prepare water-soluble Fe3O4magnetic nanoparticles (MNPs)with relative high quality via reductive decomposition of ferricacetylacetonate in the presence of benzyl ether and phenol, in whichinexpensive phenol acted as reducing agent and stabilizer, producedthe semi phenol-benzoquinone coated on the Fe3O4and made theFe3O4MNPs water-soluble and the colloidal solution stable. Bychanging the molar ratio of phenol to Fe(acac)3and the reaction time,the size of Fe3O4MNPs could be varied from19.3±4.4nm to9.7±1.5nm,with the saturation magnetization in the range of51.3-62.9emu/g.3. Fe3O4@Organic Layer@SiO2–NH2microspheres had beensuccessfully prepared by an ingenious system, which consisted ofthermal decomposition approach, reverse micro-emulsion system andsurface modification technique. And then the TEM, XRD, XPS, TG, FT-IR,and VSM were used to characterize the particles. The result showedeach Fe3O4@Organic Layer microsphere had been coated by silicashell about30nm, and the average diameter of the Fe3O4@OrganicLayer@SiO2microspheres was about538nm. The Organic Layer tosome extent had a protective effect on avoiding Fe3O4being oxidizedinto Fe2O3. The magnetization of the magnetic microspheres corecould be easily tuned between28and56emu/g by adjusting theamount of2-mercaptobarbituric acid, and the saturationmagnetization of the Fe3O4@Organic Layer@SiO2microspheres was12.5%less than the magnetic cores. The microspheres possess a hugeapplication potentiality in specificity enriching and separatingbiological samples in vitro.4. Fe3O4@Au core-shell composite nanoparticles were synthesizedby the reduction of Au3+onto the surfaces of oil-soluble Fe3O4particlesin oleyl amine. With the assistance of hexadecyl trimethyl ammonium bromide (CTAB), the as-prepared Fe3O4-Au particles were successfullyconverted into water. The particles exhibited a surface plasmonresonance peak at640nm. By changing the amount of ethyleneglycol、sodium acelate、PEI and reaction temperature, a series ofaqueous Fe3O4-PEI particles with the diameters ranging from223to321nm were prepared via solvothermal reaction. The270nm Fe3O4-PEIpartices were used to conjugate with Au nanoparticles by Au-Ninteraction to obtain the assembled Fe3O4-Au composite particles. Astrong surface plasmon resonance peak of composite particlesemerged at530nm. The Fe3O4/Au composite particles not onlyexhibited excellent magnetic properties, but introduced the opticalproperties and biocompatibility of Au nanoparticles, which makes thecomposite particles become an ideal candidate for biolabeling.5. Based on the above work, a novel immunoassay method wasdeveloped to detect2,4-D in liquid system. In this system,CdTe@SiO2-NH2particles were used as fluorescence probes to label2,4-D-OVA, and the Fe3O4@Organic Layer@SiO2–NH2microsphereswere used to label2,4-D antibody. By an immune-competing reactions,2,4-D could be detected easily and specifically without expensiveinstrument. The detection limit could reach43ng/mL. Meanwhile, thesystem may provide an effective platform for the detection of toxicsubstances retained in food. |
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