Principles of Structure-Function Relationships Applicable To Sensing Materials ─ Explosives and Bio-Diagnosis

Functions of nanomaterials can be strongly dependent on their structures. Therefore, the knowledge of structure-function relationship can provide important information for designing functional materials. This dissertation aims to gain fundamental knowledge through structural analysis of nano-sensing materials for explosives and bio-diagnosis in order to enhance the sensitivity. The main project of my research involved the investigation into the fluorescence and quenching mechanisms of pyrene with a series of organic salts and/or polystyrene of a variety of architectures as well as the function of explosive detection. The major findings of this dissertation includes: (1) the formation of pyrene excimers can be enhanced by high solvent vapor pressure annealing with the polystyrene (2) tetrabutylammonium cation (TBA+) can effectively suppress the fluorescence but hexafluorophosphate anion (PF6 -) with TBA+can counteract this effect at high solvent vapor pressure driven by temperature. This process is reasoned by dynamic quenching, (3) Polystyrene can effectively lower LUMO (lowest unoccupied molecular orbit) level of pyrene, thus facilitating the detection of the nitro-aromatic explosives. This process is presumably accomplished through radiationless energy transfer from polystyrene emission to pyrene absorption resulting in the efficient photoinduced electron transfer (PET) to explosives, (4) the diffusion coefficients of 2,4-DNT (dinitrotoluene) through pyrene/polystyrene films was evaluated and film thickness is found to be a key parameter affecting the diffusion of 2,4-DNT. The second project mainly focused on constructing potential nanotemplates for biocompatible sensing and diagnosis by using the complexes made of phospholipid/gold nanoparticles and phospholipid/polymer. The 2-nm surface-modified gold nanoparticles can be incorporated in the phospholipid bilayers. Such template can be further developed into theranostic carriers for medical imaging or hyperthermia treatment. In addition, I have shown that lipid vesicles can interact with a triblock copolymer forming clusters of vesicles – this template can also be used as sensitive biosensors