Preparation, Compositing, Properties Of Zinc Based Semiconductors And Their Applications In Biodetections

In recent years, nontoxic zinc based semiconductors, such as ZnO and ZnS, have attracted numerous attentions in biomedical fields owing to their good biocompatibility and unique optical properties. Compared to the luminescence, the resonance Raman scatterings of these zinc based semiconductors possess extremely narrow bandwidth, obvious fingerprint character, and strong anti-interference ability, which are beneficial for biodetections. The resonant Raman scatterings are closely related to the material synthetic method and the crystal quality. Simultaneously, the functionalities of the semiconductors can be expanded or enhanced by compositing. Therefore, the present dissertation carried out relative researches including the preparation of ZnO （ZnS） based materials, control of the morphology or the properties, and biodetections based on the resonance Raman scattering of semiconductors. The details are as following:（1） Series of ZnO micro/nano- structures were prepared through acoustic cavitation or hydrothermal method, and the growth mechanisms were discussed. ZnO nanorods with different length to diameter ratio, tadpole shaped and hollow spherical ZnO particles can be prepared by tuning the concentration of the precursor, the ratio of the reagents, and the kind of solvents. The morphology related micro- photoluminescence of ZnO microrods was used to probe the distributions of the crystal defects and the surface charges. It was found that crystal defects favored the formation of bound excitons, and the electric field of the surface charges resulted in the ionization of these bound excitons. The competition between the two effects determined the final photoluminescence properties of the ZnO microrods.（2） Using one-dimensional ZnO as templates, ZnO/iron oxide heterostructured microrods and nanorod arrays were prepared through mild hydrothermal procedures. The multifunctional properties of these composites were investigated. The results indicated that hexamethylenetetramine, a weak orgnic alkaline, had important influence on the crystal phase of iron oxide in the heterostructures （Fe₃O₄ or Fe₂O₃）. The obtained ZnO/iron oxide heterostructures simultaneously possessed the photoluminescence property, the resonant Raman scattering and the superparamagnetism. Compared to ZnO/Fe₂O₃, the ZnO/Fe₃O₄ composites exhibited lower defects related light emissions and stronger?saturation intensity owing to the component difference and the interface effects.（3） Using the multiphonon resonant Raman scattering of the Fe₃O₄/ZnO/Au nanocomposites as probing signal, fast ultrasensitive biodetection with high specificity and good selectivity was performed under the assistant of an external magnetic field. Owing to the superparamagnetism, the nanocomposite bioprobes were separated rapidly. The influences of the diffusion barriers and the boundary layer effects toward the sensitivity as well as the detection speed were analyzed. As we know, this is the first report on combining the multiphonon Raman signal with the superparamagnetism together to realized ultrasensitive biodetections.（4） Ultrasensitive immunoassays with high specificity and good selectivity in terms of the multiphonon resonant Raman scattering from ZnS nanocrystals were successfully achieved. Direct conjugations of the ZnS nanocrystals with biomolecules were obtained, which greatly simplified the probe synthetic process. The experimental conditions of obtaining the ZnS nanocrystals were optimized by comparative studies of the resonant Raman scattering spectra. It was demonstrated that the multiphonon Raman signal of the ZnS nanocrystals possessed extremely narrow bandwidth, good anti-interference and fingerprint characters. So far, the work of utilizing the Raman signal of ZnS but not the fluorescence to perform biodetections is still absent in the reported literatures.