الفهرس 
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Abstract
The increasing need to control the optical and thermal properties
of the nanoparticles has demanded the creation of nanocomposites
as metal/semiconductor core/shell to provide multifunctional
properties that is more advantageous than the limited singlecomponent
counterparts. In this work we have developed a
method to synthesis metal/semiconductor Ag/CdSe core/shell
hybrid nanocomposite. Seeds of silver nanoparticles were
prepared by reduction of silver acetylacetonate (organometallic
complex) using alkyl amine. Different shell thicknesses have been
grown, directly on the Ag core, by organometallic pyrolysis
method. Through controlling the reaction temperature and time
we were able to tune the CdSe shell thicknesses.
Later we have synthesized Ag/CdSe core/shell nanocomposite
having the same Ag core size (to have the same plasmonic
frequency) and different shell thicknesses.
The UV-VIS spectra for Ag/CdSe core/shell samples have shown
a compound structure of the plasmonic peak of the Ag core and
the 1st transition (1Se-1S3/2) for the CdSe shell. The peaks of the
CdSe 1st exciton red shifted from 517 nm to 406 nm due to the
increase in the shell thickness. There was also the CdSe 2nd peak
transitions (1Se-2S1/2) and (1Pe-1P3/2), which have a wide width
and weak amplitude. A 2nd derivative analysis of the UV-VIS
Chapter 5 Conclusions
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spectra have shown that the peak of the Ag has red shifted from
416 nm to 424 nm. This small red shift could be explain in terms
of the CdSe shell loading on the Ag core.
To calculate the shell thickness we used the polynomial fitting
functions and the effective mass approximation model with
parameters appropriate for CdSe to determine the shell thickness.
The values of the shell thickness varied from 2.51 nm to 4.77 nm.
The HRTEM images have shown that these value are in good
agreement with the experimental ones.
A Photoacoustic spectra was also carried out for the same
samples, that have shown a compound spectra for the Ag
plasmonic peak and CdSe 1st exciton peak. The CdSe 2nd exciton
was not clearly observed in these spectra. Observation of the Ag
plasmonic and the CdSe 1st exciton peak in both the PA and the
UV-VIS spectra, have shown these results are in good agreement.
Furthermore, the compound structure spectra in the UV-VIS and
PA spectra is a strong evidence of the weak interaction between
plasmon field of the Ag and the exciton dipole of the CdSe.
Photoluminance was carried out for Ag/CdSe samples, using 488
nm as excitation wavelength. The PL have shown different peaks
of the CdSe shell that varied from 525 nm to 614 nm.
A Raman spectra was carried out, using 488 nm as excitation
wavelength, for the Ag/CdSe samples of different CdSe shell
thicknesses which were carefully weight adjusted to have the