Intramolecular charge transfer and proton transfer in heterogeneous environments
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The thesis is formulated into 7 chapters along with summery. Chapter 1 is the introduction describing important aspects of fluorescence such as intramolecular charge transfer (ICT) and proton transfer (ESIPT), factors effecting ICT and ESIPT, nanoparticle-fluorophore interaction motivating for the present research works planned. Chapter 2 is about materials, methodologies and instrumentations such as UV, steady state and time resolved spectrophotometer, FESEM, TEM etc. Chapter 3 describes the interactions of the silver nanoparticles with 2-(4΄-N,N-dimethylaminophenyl)benzimidazole and its nitrogen substituted analogues. These fluorophores are well efficient in stabilizing the nanoparticles. These interactions led to the formation of TICT state from the nitrogenous analogues in aprotic solvent for the first time. Complexation with β- cyclodextrin strengthen the TICT emission. Chapter 4 elaborates the extraction of same set of ICT fluorophores as in chapter 3 from nanoparticle composite by micelles of different ionic character. Silver nanoparticles in water were prepared by reducing silver nitrate salt using simple borohydride reduction method without any other common stabilizing agent. The hydroxyl ion present in solution acted as stabilizer at specific pH of 10. All three fluorophores interact with silver nanoparticles prepared in water through the ring nitrogen with static quenching. The fluorescence of the fluorophores can be recovered by addition of surfactant. The micelles were found to be well efficient to extract the fluorophores from the nanoparticles surface into their hydrophobic cavities. It seems that the CTAB has stronger interaction with the nanoparticles than TX-100. Interaction of nanoparticles with the same set of fluorophores present inside the BSA pocket is explained in chapter 5. Addition of silver nanoparticles to these systems lead to some conformational changes in the tertiary structure of the protein leading to exposure of the fluorophores.
Supervisor: G Krishnamoorthy