In this thesis I am presenting a detailed study to optimize the deposition of magnetic molecules and gold nanoparticles in atomically flat surfaces by self-assembling them from solution. Epitaxially grown and atomically flat gold surface on mica is used as substrate for this study. These surfaces have roughness of the order one tenth of a nanometer and are perfect to image molecules and nanoparticles in the 1-10 nanometers range. The purpose of these studies is to find the suitable parameters and conditions necessary to deposit a monolayer of nano-substance on chips containing gold nanowires which will eventually be used to form single electron transistors by electromigration breaking of the nanowire. Maximization of the covered surface area is crucial to optimize the yield of finding a molecule/nanoparticle near the gap formed in the nanowire after electromigration breaking. Coverage of the surface by molecules/nanoparticles mainly depends on the deposition time and concentration of the solution used for the self-assembly. Deposition of the samples under study was done for different solution concentrations and deposition times until a self-assembly monolayer covering most of the surface area is obtained. Imaging of the surfaces after deposition was done by tapping-mode AFM. Analysis of the AFM images was performed and deposition parameters (i.e. coverage or molecule/particle size distribution) were obtained. The subjects of this investigation were a molecular polyoxometalate, a single-molecule magnet and functionalized gold nanoparticles. The obtained results agree with the structure of each of the studied systems. Using the optimized deposition parameters found in this investigation, single-electron transport measurements have been carried out. Preliminary results indicate the right choice of the deposition parameters.

The increase in antibacterial resistance has placed the issue of microbial multi-drug resistance on a global stage (Gurunathan, 2019). This issue poses a threat to human and animal health as well as to the environment (Aslam et al., 2018). It affects not only the efficacy of treatment but also how those treatments are conducted (Friedman, Temkin, & Carmeli, 2016). As a result of this ongoing threat, new treatments that have potent effects on bacteria are necessary. One scientific response to this issue has been the development of multifunctional nanoparticles (NPs)(H. Wang et al., 2018). NPs have the ability to be utilized by its varying modes of action and compatibility with other forms of treatments (Alavi & Rai, 2019). This advantage, when successful, would allow for the lowering of dosage and frequency of treatments required to achieve bacteria-killing (Alavi & Rai, 2019). Despite a plethora of proposed designs for the improvement of antibacterial treatment, questions remain concerning the mode of action of these new agents. The aim of this study is to develop a protocol facilitating the identification of modes of action of newly formulated antibacterial agents. Our hypothesis is that different modes of action will have distinct effects on the morphology and composition of the cells. To test this, we characterized the structural, physical and molecular changes of a model system, E. coli., before and after treatments using antibiotics with known modes of action. We selected two bactericidal antibiotics: colistin which is a membrane disrupting antibiotic, and streptomycin which is a protein inhibiting antibiotic (Santo-Domingo, Chareyron, Broenimann, Lassueur, & Wiederkehr, 2017; Sun et al., 2019; Thummeepak, Kitti, Kunthalert, & Sitthisak, 2016). We discuss the protocol development and the significant differences observed in the bacterial responses as well as the limitations of the envisioned approach. We conclude by providing a perspective of the impact our findings are expected to have on evaluating new engineers NP treatments.

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