Nano-confined water within the membrane of self-assembled vesicles
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The hydrophobic metal carbonyl complexes, known as FpR (Fp = (Cp)Fe(PPh3)(CO)(CO−), Cp = cyclopentadiene, R = C3Bithiophene, C6Pyrene, C6Azobenzene or C6), self-assembles into stable colloids in water. The colloids are known as metal carbonyl vesicles (MCsome), whose membrane contains interstitial water within tetrahedral order in hydrogen bonds. This well-structured water is responsible for the structural integrity of MCsome. This role of interstitial water is influenced by a variety of factors, including aging the MCsome, the non-polar R-group within the membrane and the presence of a water miscible organic solvent. In this thesis, we first examined how the colloid preparation (addition of water to THF solution of FpR) is sensitive to the quality of water used, the order of mixing water and THF solution of FpR and the rate of water addition. Following the colloidal preparation, we investigated the effect of temperature on MCsome. A higher temperature induces the swelling of MCsome, while cooling to a lower temperature shrinks the MCsome. This behaviour is found to be related to the interstitial water as its polarity and cohesive energy is affected the temperature. With higher temperatures, the polarity increases and the cohesive energy decreases, while cooling to a lower temperature decreases polarity and increases cohesive energy. This behaviour is explained by the temperature-dependent change in the interstitial water structure and dynamics. The change in the interstitial water structure and dynamics influences the energy dissipation as indicated by the temperature-dependent fluorescence intensity of FpC6Pyrene where increasing temperature decreases the energy dissipation of the interstitial water. Using the knowledge obtained from the investigation, it was found that the cooling temperature of the colloids is important in the reconstruction of the interstitial water. Colder temperatures are found to restructure the interstitial water more quickly unlike cooling to room temperature. Furthermore, the changes in the temperature-dependent interstitial water are reversible when the temperature is below 40 °C since the restructure of the interstitial water is quick. Therefore, FpR MCsome is an ideal assembly model for the study of interstitial water confined with self-assembled nano-spaces, which is highly desirable knowledge for the design of novel colloids and understanding biological systems.
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Audren Marquez (2021). Nano-confined water within the membrane of self-assembled vesicles. UWSpace. http://hdl.handle.net/10012/17603