The Studies On Optical Properties Of The Heterostructured ZnO/Au And Resonant Raman Scattering For Protein Detection

Zinc oxide is aⅡ-Ⅵwide band-gap(3.3eV) semiconductor with wurtzite crystal structure.Due to the large exciton binding energy of 60meV,it is regarded as one of the most promising materials for fabricating efficient ultraviolet(UV) and blue light emitting devices.But the materials have some defects themselves, metal-semiconducting material can remedy defects of semiconducting material by the properties of metals.They would get excellent properties and provide base of the future application in devices.Otherwise,ZnO has also been widely focused in many fields such as medicine,solar energy cell,food,cosmetics and so on.In this thesis,ZnO nanomaterials were chosen as the subject of investigation, which was focused on the synthesis and characterization of water-soluble ZnO/Au nanocomposites.ZnO/Au nanocomposites were used for detecting unknown protein molecule base on Resonant Raman Scattering.The details are as follows:(1) The ZnO/Au nanocomposites were successful prepared by reduction reaction. The size distribution and morphology of the ZnO/Au nanocomposites were characterized by the TEM.The UV-vis absorption spectra of ZnO/Au nanocomposites exhibited well-defined exciton band of ZnO quantum dots (QDs) in the ultraviolet region(250-400 nm).The plasmon absorption band of Au nanocrystals was observed in the visible region(400-700 nm).Combined with optical spectra and structure analysis,the electron transfer between ZnO and Au may be thought.The photoluminescence of ZnO/Au nanocomposites showed the effect of Au on ZnO nanocomposites.Furthermore,the resonance Raman scattering of the ZnO/Au nanocomposites was observed with excitation of 325 nm light from He—Cd laser.The amount of Au coating on the surface of ZnO is important for obtaining different intensity of enhanced Raman scattering.(2) The biocompatible ZnO/Au nanocomposites were studied by changing the the amount of Au on ZnO nanoparticles.Au layer on ZnO surface has great effect on the ZnO in aqueous solution due to the interaction between ligand on Au and water molecule.(3) A probe for the target protein was constructed by binding the ZnO/Au nanoparticles to secondary protein by eletrostatic interaction.The detection of proteins was achieved by an antibody-based sandwich assay.A first antibody,which could be specifically recognized by target protein,was attached to a solid silicon surface.The ZnO/Au protein probe could specifically recognize and bind to the complex of the target protein and first antibody.This method on the resonant Raman scattering signal of ZnO nanoparticles showed good selectivity and sensitivity for the target protein.(4) Different morphology of ZnO/Au nanocomposites was obtained by changing the salt concentration of solution.We also study on the optical properties of these nanocomposites.