Plasmonic Effects and Optical Properties of Core-Shell Nanoparticles
| dc.contributor.advisor | Belyaneh Mesfin | |
| dc.contributor.advisor | Teshome Senbeta | |
| dc.contributor.author | Garoma Dhaba | |
| dc.date.accessioned | 2025-08-31T23:17:08Z | |
| dc.date.available | 2025-08-31T23:17:08Z | |
| dc.date.issued | 2023-05 | |
| dc.description.abstract | The applications in the real world require specific sizes, shapes, compositions, and structures. Hence, this dissertation is devoted to the theoretical and numerical investigations of the effects of size, shape, surface plasmons, and host medium on the optical properties of core-shell nanocomposites (NCs). Under the quasi-static approximation, we employed Laplace’s equation and the Drude-Lorentz model for electric potential distributions and dielectric functions, respectively. Then we calculated the local field enhancement factor (LFEF), polarizability, absorption, scattering, and extinction cross sections for spherical, cylindrical, prolate, and oblate core-shell NCs. The study reveals that when the core radius of spherical CdSe@Ag decreases, the resonance peaks of LFEF increase and are red shifted in the inner interface and blue-shifted in the outer interface of the shell. However, whether the shell radius is kept constant or decreased, increasing the core size produces a lower LFEF, showing that the core size is a crucial parameter to change the LFEF of nanoshells. Furthermore, an increase in the size of the core results in an increased resonance peaks of LFEF only in the presence of the spacer (ZnSe) between the core (CdSe) and the shell (Ag), demonstrating that the number of layers and the size of the spacer of core-shell NCs can affect the optical characteristics. When the metal shell thickness increases at a constant core radius, an enhancement in the local field factor is observed due to plasmonic effects. In addition, out of the four different shapes of CdSe@Au core-shell NCs studied, the LFEF, absorption, and extinction cross sections of the spherical and cylindrical structures possess two peaks, whereas oblate and prolate spheroids show three observable peaks. Moreover, the spherical and cylindrical core-shell NCs show higher peaks of LFEF and extinction cross sections, respectively. For the same composition, the differences in shapes of core-shell NCs determine the intensity, the number, and the positions of peaks of the LFEF and optical cross sections. The study also indicated that in different shapes of core-shell NCs, the change in the dielectric function of the embedding medium produces LFEF and extinction cross sections of different properties. Our analysis reveals that increasing the magnitude of the permittivity of the embedding medium greatly enhances the LFEF of nanoshells, than does increasing the metallic shell thickness. The possibility of obtaining adjustable LFEF by varying the sizes of the components of the core-shell NCs makes them attractive for applications in nonlinear optics, photocatalysis, and optoelectronics. Furthermore, shape dependent optical properties might be promising for applications in optical detection and bio-sensing. Especially, gold coated core-shell spheroids have good potential uses in multi-channel sensing. | |
| dc.identifier.uri | https://etd.aau.edu.et/handle/123456789/7271 | |
| dc.language.iso | en_US | |
| dc.publisher | Addis Ababa University | |
| dc.subject | Plasmonic Effects | |
| dc.subject | Optical Properties | |
| dc.subject | Core-Shell Nanoparticles | |
| dc.title | Plasmonic Effects and Optical Properties of Core-Shell Nanoparticles | |
| dc.type | Thesis |