Browsing by Subject "Thin films, Multilayered."

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Open Access
Preparation and characterization of ultra thin films containing silver-copper nanoalloys using layer-by-layer deposition technique for antibacterial applications
(2012) Camcı, Merve Taner
The main objective of this master thesis is to explore the preparation, characterization and antibacterial applications of Layer-by-Layer (LbL) assembled ultra thin films containing AgCu nanoalloys. Within this purpose, first part of the research mainly focused on the preparation of Ag nanoparticles and AgCu nanoalloys in order to prevent the oxidation of copper to copper oxide and the formation of polyelectrolyte-AgCu nanoalloy films by Layerby-Layer assembly. Accordingly, Ag nanoparticles and AgCu nanoalloys were synthesized by the chemical reduction of silver and copper salts in aqueous solution with the help of strong reducing agents sodium borohydride or hydrazine hydrate in the presence of complexing agent and stabilizer, then ultra thin polyelectrolyte layers containing pre-prepared AgCu nanoalloys were constructed by Layer-by-Layer deposition technique in different combinations. Also the stability of these nano sized binary alloys in solution phase were prolonged in the presence of third metal zinc as a sacrificial anode. In the second part of the study, characterization of LbL assembled ultra thin polyelectrolyte and metal nanoparticle thin films using Optical (UV-visible) and X-ray Photoelectron Spectroscopy (XPS) was studied. In order to get further information on the optical response of single and bimetallic nanoparticles, Ag nanoparticle and AgCu nanoalloy incorporated ultra thin polyelectrolyte films were investigated by optical spectroscopy. In addition the LbL films were analyzed by Static XPS to extract atomic level chemical information due to elemental and chemical state analysis. In order to get further understanding at the molecular level, samples were analyzed under external bias application by Dynamic XPS and it was shown that Ag and Cu respond in the same way to applying external electrical stimuli when both are in the same environment as a result of alloy formation, as reflected by the same shifts in Ag3d and Cu2p binding energy positions. Lastly, in the third part of the study detailed antibacterial analysis of synthesized monometallic and multimetallic nanoparticle solutions and the organized ultra thin polyelectrolyte layers containing Ag and AgCu nanoclusters against Escherichia coli strain was performed. These approaches enabled us to show the better antibacterial behavior of AgCu nanoalloys as a result of successful synthesis of AgCu nanoalloy without any copper oxide formation as the end product.
Open Access
Preparation and characterization of ultra-thin films containing Au and Ag nanoparticles using layer-by-layer deposition technique
(2009) Cönger, Can Pınar
The main objective of this thesis is to investigate the layer-by-layer deposited polyelectrolyte and polyelectrolyte/metal nanoparticle films by using X-ray Photoelectron (XPS) and Optical Spectroscopy (UV-Vis). Within this purpose, in the first part of the study, layer-by-layer deposited single and oppositely charged bilayered films are investigated by XPS. To extract additional information in the molecular level, the samples are analyzed while applying an external voltage bias. It is shown that applying external electrical stimuli to a single polyelectrolyte layer coated Si/SiO2 system responds to the change in the polarity by molecular rearrangements, evidenced by the changes only in the intensity of the corresponding –N + (1s) peak. In the second part of the study, metal nanoparticle (Au and/or Ag) incorporated polyelectrolyte films are investigated by optical spectroscopy. Within this frame, multilayer gold and silver nanaoparticle/polyelectrolyte films are prepared both separately and in bimetallic form. In order to get further understanding about the optical responses of single type of metal nanoparticle incorporated systems, several experimental approaches are followed. These approaches also enable us to control and manipulate the optical properties of these compact structures. The last part focuses on incorporation of metallic ions into layer-by-layer assembled polyelectrolyte matrices through ion-exchange method. It is shown that metal ions can be incorporated and subsequently reduced within this polymer matrix by UV or X-ray irradiation and can also form nanoparticles.