Studies of liquid crystal (LC) /Au nanoparticle (NP) composites have been pursued in columnar and in nematic phases of thermotropic LCs. Using LCs forming a columnar phase, we found that different functionalities on the corona of the Au NPs (hydrophobic vs. hydrophilic) display unique effects on the stability and ordering of the columnar LC phase. Doping nematic LCs with non-chiral or chiral Au NPs causes the formation of textures commonly observed for chiral nematic LCs, i.e., the formation of somewhat uniform stripe textures or patterns separated by areas of homeotropic alignment of LC molecules. Two scenarios are proposed. In the first scenario, the Au NPs form topological chain-like defects and the remaining Au NPs reside at the interface inducing vertical alignment of the LC molecules. In the second scenario, chiral Au NPs transfer chirality to the nematic LC host. Further, induced circular dichroism studies proved the second scenario. Using the same chiral Au NP systems, the origin of chirality of Au NPs has also been studied, and a powerful methodology has been proposed to unravel the puzzle of chirality of chiral ligand-protected Au NPs. Further investigations of these texture phenomena led to the discovery of using metal NPs to control the orientation and alignment of LCs. In due course, a dual alignment and electro-optical switching behaviour was found using alkylthiol-capped Au NPs doped into a nematic LC with positive dielectric anisotropy in planar namatic LC cells. This study was also expanded to Ag and CdTe NPs, which showed the same phenomenon, and all investigated NPs significantly reduced the voltage needed to re-orient the LCs in an electric field (threshold voltage). Starting from basic and moving on to more application-oriented research, we finally also initiated structure-property relationship studies of LC/NP composites.

Traditional radiation therapy is limited by the radiotoxic effects on surrounding healthy tissues. This project investigated the use of a gold nanoparticle (AuNP) conjugated to a cell-penetrating peptide (CPP) to increase tumour cell death during radiotherapy by maximizing the cellular import of the gold nanoparticles. ~8300 octaarginine CPPs were coupled per 30 nm AuNP through poly(ethylene glycol) spacers (AuNP-PEG-CPP). The CPPs enhanced the internalization of the AuNPs into three human breast cancer cell lines by a factor >2 as compared to untargeted AuNPs. Cells were treated with AuNP-PEG-CPP for 24 hours, prior to radiotherapy and their long-term proliferation was assessed in clonogenic assays. The increased internalization of AuNPs by the CPPs resulted in greater cell death following exposure to 300 kVp radiotherapy, by a dose enhancement factors between 1.3 and 2.1 depending on the cell line. These findings illustrate the potential of using AuNP-CPPs to enhance radiotherapy in patients.

Traditional radiation therapy is limited by the radiotoxic effects on surrounding healthy tissues. This project investigated the use of a gold nanoparticle (AuNP) conjugated to a cell-penetrating peptide (CPP) to increase tumour cell death during radiotherapy by maximizing the cellular import of the gold nanoparticles. ~8300 octaarginine CPPs were coupled per 30 nm AuNP through poly(ethylene glycol) spacers (AuNP-PEG-CPP). The CPPs enhanced the internalization of the AuNPs into three human breast cancer cell lines by a factor >2 as compared to untargeted AuNPs. Cells were treated with AuNP-PEG-CPP for 24 hours, prior to radiotherapy and their long-term proliferation was assessed in clonogenic assays. The increased internalization of AuNPs by the CPPs resulted in greater cell death following exposure to 300 kVp radiotherapy, by a dose enhancement factors between 1.3 and 2.1 depending on the cell line. These findings illustrate the potential of using AuNP-CPPs to enhance radiotherapy in patients.

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Small particles of gold (< 100 nm) have attracted great interest among researchers due to the unique combination of their physicochemical properties. Among various research areas catalysis and bio-nanotechnology represent the largest areas of growth for gold nanoparticle research. Catalysts play a crucial role in the life of the modern society. More than 85 % of all chemical processes are catalytic, and this number is increasing every year. There is a constant demand to develop more efficient and durable catalysts in order to address increasing energy demands and environmental requirements. The first part of the thesis is focused on the study of catalytic activity of supported gold and mixed-metal catalysts, derived from atomically precise phosphine-stabilised gold and mixed-metal clusters in the liquid-phase oxidation of cyclohexene and one-pot synthesis of imines. Various characterisation techniques (TEM, diffuse-reflectance UV-vis, XPS, etc.) as well as kinetic studies were used in order to establish the optimal structure of gold catalysts. The effect of catalytic support, nature of hetero-metal atom for mixed metal-systems and type of catalyst pre-treatment were also examined. Gold nanoparticles are actively studied in various biomedical applications as they are offering new approaches to the detection and treatment of life-threatening diseases, such as cancer. The second part of this work discusses our preliminary investigations of biological activity of gold nanoparticles, stabilised with cancer-targeting molecules. In particular, the cytotoxicity of gold nanoparticles was studied using 11 different cancer and normal cell types. Gold uptake and particle localisation inside the cells were also investigated.

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We plan to form and characterize surface-attached catenane gold nanoparticles. The proposed catenane self-assembles when a pi-electron-rich bis(thiol)hydroquinone derivative (hereby referred to as the dithiol) threads through a pi-electron-deficient inorganic molecular square forming a charge-transfer complex in solution and then attaches itself to a particle via two gold-sulfur covalent bonds.In preparation of this goal, an inorganic molecular square had to be synthesized. We synthesized, recrystallized, and characterized a cationic, tetranuclear, Pd(II)-based macrocyclic square according to the procedures published by Stang2.Then various methods of synthesis and derivatization of gold nanoparticles were investigated. Using a two-phase method published in the literature, dodecanethiolderivatized nanoparticles were synthesized,8 and attachment of the dodecanethiol was confirmed by NMR, IR, and UV/Vis spectroscopy. After the confirmation of the model compound, the reaction scheme was scaled-down for the derivatization of the nanoparticle with the dithiol alone which will be one of the components that will form the proposed catenane.Upon the derivatization of the nanoparticle with the dithiol, there was great difficulty in dissolving the nanoparticles in any polar or non-polar solvent. This led us to believe that nanoparticles are cross-linking with each other and therefore not dissolving. However, the attachment of the dithiol to the nanoparticle was confirmed by infrared spectroscopy. To solve the cross-linking problem an exchange reaction was conducted between the dodecanethiol-derivatized gold nanoparticles and the dithiol in a modified procedure from the literature.18 Although a successful exchange was confirmed by infrared spectroscopy, the dithiol-derivatized gold nanoparticles were still not soluble in any suitable solvent. / Department of Chemistry

Studies of liquid crystal (LC) /Au nanoparticle (NP) composites have been pursued in columnar and in nematic phases of thermotropic LCs. Using LCs forming a columnar phase, we found that different functionalities on the corona of the Au NPs (hydrophobic vs. hydrophilic) display unique effects on the stability and ordering of the columnar LC phase. Doping nematic LCs with non-chiral or chiral Au NPs causes the formation of textures commonly observed for chiral nematic LCs, i.e., the formation of somewhat uniform stripe textures or patterns separated by areas of homeotropic alignment of LC molecules. Two scenarios are proposed. In the first scenario, the Au NPs form topological chain-like defects and the remaining Au NPs reside at the interface inducing vertical alignment of the LC molecules. In the second scenario, chiral Au NPs transfer chirality to the nematic LC host. Further, induced circular dichroism studies proved the second scenario. Using the same chiral Au NP systems, the origin of chirality of Au NPs has also been studied, and a powerful methodology has been proposed to unravel the puzzle of chirality of chiral ligand-protected Au NPs. Further investigations of these texture phenomena led to the discovery of using metal NPs to control the orientation and alignment of LCs. In due course, a dual alignment and electro-optical switching behaviour was found using alkylthiol-capped Au NPs doped into a nematic LC with positive dielectric anisotropy in planar namatic LC cells. This study was also expanded to Ag and CdTe NPs, which showed the same phenomenon, and all investigated NPs significantly reduced the voltage needed to re-orient the LCs in an electric field (threshold voltage). Starting from basic and moving on to more application-oriented research, we finally also initiated structure-property relationship studies of LC/NP composites.

No description available.