Thesis (M.Sc.) - Cairo University - National Institute of Laser Enhanced Sciences - Department of Laser Systems

The complexation of metallic silver nanoparticles (NPs) with fluorescein derivative laser dyes (p-aminophenol fluorescein, p-anisidine fluorescein and p-methyl aniline fluorescein ) have significant effect on optical properties of the laser dye, the fluorescence intensity, lifetime, photostability and the fluorescence efficiency . Which the [Ag : dye] complex has energy transfer effect from scattering energy of metallic Ag NPs to laser dyes spectra depending on the distance between them. This arises from interactions with surface plasmons resonance (SPR) in the metal nanoparticles. The size of prepared Ag NPs was determined expermentally by TEM and UV-Vis absorption spectroscopy techniques. Mie theory was also used to confirm the size of Ag NPs theoretically. Enhancement as well as quenching of fluorescence intensity has been observed and studied . It was found that fluorescence intensity can be tuned by adding various amounts of silver nanoparticles to the three dyes, when metal nanoparticles are located at certain distance (preferable for MEF phenomena) , enhancement in fluorescence is observed. This effect has been explained by coupling of surface plasmon resonance from metal nanoparticles with fluorophore, resulting in the increase of excitation and emission rate of the fluorophore in the localized electromagnetic field. Emission enhancement factors were calculated for all samples

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