الفهرس 
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Abstract
Semiconductor- Plasmonic hybrid nanocomposite which combine the extraordinary properties of quantum dots such as tunable band gap, strong absorption and emission properties , narrow band with long exciton lifetime and the localized electric field due to the surface Plasmon resonance of the metallic part attract our attention. from the physics point of view, it is interesting to understand the nature of the Plasmonic-exciton coupling and how this could affect the collective optical properties and exciton dynamics of such systems. from the technological point of view, these coupled composites have so many possible applications in photovoltaic, photo-catalysis and other optoelectronic devices applications. Therefore, we prepared hybrid Plasmonic-Semiconductor nanocomposite such as tetra-pods of gold as a core and arms of CdSe Nanocrystals and match stick of silver as a head and wire of CdTe. The size and the shape of the obtained nanoparticles have been characterized via High Resolution Transmission Electron Microscope (HR-TEM), the chemical and structural compositions have been evaluated using X- Ray diffraction (XRD) and Energy Dispersive X-Ray spectroscopy (EDX). Our finding indicates that, a remarkable enhancement in the optical absorptivity was obtained, upon the presence of plasmonic part close to the semiconducting part. However, a dramatic quenching in the fluorescence intensity was monitored. This contrast in the photophysical properties is attributed to the fast charge carriers (i.e. electron) transfer from the conduction band (CB) in the semiconducting part to the Fermilevel (EF) of the metallic part. Because of the unusual properties of graphene i.e. (planar structure, high surface area, high electron mobility, high electrical conductivity and high mechanical properties), we prepared the same materials in the presence of reduced graphene oxide (RGO) Interestingly, the presence of reduced graphene oxide reduce the growth rate of the particles and enhance all the optical properties such as absorption cross section, molar absorptivity, quantum yield and full width at half maximum (FWHM). Remarkable enhancement of the quantum efficiency has been observed for the particles prepared in presence of graphene (4.5 to 12 fold intensity in the emission intensity). This might be due to the rate of the electron transfer from graphene to the metal is faster than that from semiconductor to the metal. The plasmonic nanomaterials such as (Au and Ag) nanoparticles showed a good catalytic activity in comparison to the Plasmonic / semiconductor hybrid nanocomposite. Silver nanoparticles loaded on reduced graphene oxide showed a photodegredation percent (96%), that is due to dual effect of localized thermal effect from the surface Plasmon band and the high thermal stability of reduced graphene oxide while in case of using gold nanoparticles loaded on reduced graphene oxide it shows (81%) due to the formation of J- aggregate complex between the gold nanoshell and the organic dye which need much energy to separate the dye and start the photodegredation. These novel Graphene/Plasmonic /Semiconductor hybrid nanocomposite show a dual function, i.e. charge separation within the metal/graphene and enhance the emission properties within the semiconductor.