Properties and Applications of Metal Cholate Hydrogels

Abstract

This thesis presents a detailed study on the unusual properties of silver cholate, applications of lanthanide cholate gels, enhanced luminescence of lanthanides by water, and the mechanism of formation of these gels. Chapter 2 discusses unusual properties of silver cholate hydrogel. This gel has hydrophobic pockets which hydrophobicity is similar to that of degassed cyclohexane, which has not been seen in any other supramolecular system. Additionally, unlike other known metal cholate hydrogels, silver cholate hydrogel showed a thermo and mechano responsive nature. Chapter 3 has addressed the mechanism of metal cholate hydrogelation using a variety of techniques. The morphology of the aggregates changed substantially during the sol (spherical particles) to gel transition (fibres), by entanglement and not by dendritic growth. The growth was found to go through a nucleation–elongation model with instantaneous nucleation and 1D interface controlled growth. A simple protocol rapidly detect naproxen and propranolol using TbCh gel has been discussed in Chapter 4. The system was easy to prepare and use, showed very low LOD, could be used to detect the drugs from unprocessed blood, and could differentiate these drugs from their closely related analogues. Chapter 5 presents an unexpected role of water in enhancing the luminescence of Eu(III) in EuCh gel. We showed that this was due to the sensitization of the lanthanide emission by hydrophobic partitioning of pyrene on the hydrogel fibres which brought it in close proximity to the lanthanide ion. Finally, chapter 6 deals with the design of two white light emitting lanthanide–based systems prepared from commercially available materials. While most of the other reported white light emitting materials require complex synthesis or harsh procedures, our systems were prepared by simply mixing aqueous solutions of the components and sonicating for 1– 3 minutes, without any other processing.