Synthesis and characterization of silver-ceria nano-composites

This project investigated the impact of concentration of silver and ceria in the silver-ceria nanocomposites on the energy bandgap and the intensity and full width-half maximum (FWHM) of the fluorescence spectrum. Silver and ceria nanoparticles and various concentration of silver-ceria nanocomposites were synthesized. The synthesis technique used was chemical precipitation. The analysis of the fluorescence emission spectra of the silver-ceria nanocomposites indicated that ceria was present in the form of CeO2 there is almost no presence of Ce2O3. The silver-ceria nanocomposites exhibited fluorescence quenching when compared to the fluorescence obtained from the silver nanoparticles and ceria nanoparticles. The fluorescence peak wavelength for all samples was found to be around 520 nm. The FWHM of the fluorescence signal in all samples was also similar, in the range of 22 to 27 nm. Analysis of the ultraviolet-visible absorption spectra of the samples containing silver nanopartciles was performed to determine the parameters associated with its surface plasmon resonance (SPR). The SPR peak wavelength of silver nanoparticles was recorded to be around 430 nm. The SPR peak wavelength is found to strongly dependent on the optical refractive index of the solvent as well as the solute. In the case of silver-ceria nanocomposites, the refractive index of solvent (water) is ~1.3 and that of the solute (ceria) is ~4.84. The FWMH of the SPR spectra broadened significantly in the silver-ceria nano-composites compared to the FWHM of the SPR spectrum of silver, indicating that the size distribution of the silver nanoparticles in the silver-ceria nano-composites were very large.. By fitting the absorption spectra collected on the ceria and silver-ceria nanoparticles using Tauc’s model, it was determined that the energy bandgap of ceria nanoparticles was indirect in all of the samples.