| Quantum dot (QD) is a portion of matter (e.g. semiconductor) whose excitions are confined in all threespatial dimensions. Due to its unique structure, QDs have a series of eminently novel properties. Forexample, the emission spectra of QDs tenability, high photo stability, broad excitation and narrow emissionspectra, large Stokes shift, good biocompatibility, long fluorescent life and so on. Therefore QDs have avery broad application prospects in nonlinear optical, magnetic media, catalysis, medicine, functionalmaterials, etc. In particular, the fluorescent label prepared by coupling with QDs and biological moleculesis fabricated for biomarker or bio-imaging. All these studies promote the development of QDs further.However, a typically synthesized QDs are hydrophobic and poor biocompatibility. It is requires that wemust modify or functionalize the surface of QDs, and make it water-soluble for coupling easily with avariety of biomolecules. On the other hand, the methods that functionalize QDs include: modifying thegroup on the surface of QDs and/or coating a modified layer over the surface of QDs. But it may be verychallenging owing to the poor aqueous-phase transport of these QDs, drastic PL dropping during emulsionpolymerization and so on, which urge us to study the methods and process of QDs functionalized. In thispaper, with the aim of synthesizing nanometer high fluorescent composite microspheres, we developed aminiemulsion polymerization process to obtain carboxyl functionalized fluorescent CdSe/ZnSQDs-polystyrene composite microspheres. And initially explored the application performance ofwater-soluble nanocrystals in the bio-detection, as well as in the field of the preparation of composite films.The following researches were conducted and the main results and conclusions are as follows:1. We obtained carboxyl functionalized fluorescent CdSe/ZnS QDs-polystyrene composite microspheresby introducing carboxyl group (AA) in miniemulsion polymerization process. The as-prepared carboxylfunctionalized fluorescent microspheres were high fluorescent and extremely stable in variousphysiological conditions (different NaCl concentration, different pH value, different temperature and PBSbuffer solution) and showed improved fluorescent stability compared with traditional mercapto compoundsand amphiphilic polymers modified aqueous QDs. Moreover, we also demonstrated that the water-solublecomposite fluorescent microspheres could be successfully applied to detect alpha-fetal protein (AFP)antigen in vitro. Our strategy was based on a biosensor system (lateral flow immunoassays system, LFIA), in which fluorescent microspheres were used as fluorescence labels. The detection limit of AFP detectionreached0.1ng/mL, which was200times higher than commercial colloidal gold labeled LFIA strips andsimilar level of enzyme-linked immunosorbent assay (ELISA) kit for AFP detection..2. On the basis of chapter Ⅱ, we prepared red, green and blue light emission CdSe/ZnSQDs-polystyrene fluorescent composite microspheres without introducing acrylic acid (AA). At the sametime, we have synthesized poly-acrylic acid copolymer emulsion (PAA) with a low molecular weight, andmixed with as-prepared QDs-polystyrene composite microspheres to obtain transparent compositefluorescent films. The emission colors of composite films were very obvious under UV irradiation due tothe high QY of QDs-polystyrene composite microspheres. At some extend, the PL intensity of thecomposite films increased nearly linearly with increasing concentration of QDs. Then we systematicstudied the photoluminescence properties and the resistance to UV light in dark enviroment of compositefilms. Furthermore, we have acquired white light emitting QDs-polystyrene composite fluorescent films bymixing red, green and blue QDs-polystyrene composite microspheres in appropriate ratio. |
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