5275
Safaa Saeid Mohamed Ali
THE POLYMERS ASSISTED GROWTH OF MONODISPERSED NANOPARTICLES: CONTROLLED SYNTHESIS AND SPECTROSCOPIC CHARACTERIZATION
POLYMERS, NANOPARTICLES, Au, NANOPARTICLES, agnano porticpes, core@shell, popyoop method
This thesis is regarding the science around an interdisciplinary methodology to nanoparticles. Investigations on the amalgamation of Ag furthermore Au@Ag core@shell nanoparticles utilizing polyol system are exhibited. Understanding also controlling those transform parameters for nanoparticles development throughout fabrication are the keys towards great creation of materials with customized properties. Those association between the procedure parameters, structure also physical properties about nanoparticles has been inspected. In this work, we have developed a novel self-seeding route for fabrication of metallic nanocomposites of gold (core) and silver (shell) (Au@Ag core@shell). Herein, polyvinylpyrrolidone (PVP) is used as both reducing and stabilizing agent. The surface plasmon resonance (SPR) of Au@Ag core@shell can be tuned by controlling the thickness of the Ag shell. The different growth stages of the Au@Ag core@shell has been traced by in situ UV– vis absorption spectra. Transmission electron microscopy (TEM), High-angle annular dark field (HAADF) imaging and the energydispersive X-ray spectroscopy (EDS) elemental mapping which, were performed using Scanning Transmission Electron Microscope (STEM), X-ray diffraction (XRD), dynamic light scattering (DLS), zeta analyzer and Fourier transform infrared (FTIR) spectroscopy, are used for the characterization of the prepared samples. The as-synthesized Au@Ag Core@shell colloids exhibited good catalytic activity for the degradation of 4- nitrophenol.The obtained results show that, a series of Au@Ag core@shell has been successfully prepared via new self-seeding pathway with the aid of PVP chains. The PVP chains are found to induce the reduction of primary Ag nanoparticles which in turn undergo a galvanic replacement reaction with Au3+ ions to form the core. Increasing the amount of Ag+ ions results in (1)thickening of the shell, (2) the SPR peak of Au core is progressively blue-shifted until it totally transformed to welldefined silver SPR peak. This synthetic pathway is eco-friendly, easy to perform and provide fine control to the structure of the prepared core@shell nanocomposites. The prepared Au@Ag core@shell exhibits catalytic activity toward degradation of 4-NP.
2016
Ph.d
Al-Azhar
Science