Soft-materials with SOMs and Surfactants as a Model System to Study Elementary Phenomenon to their Application in Catalysis

Sen, Rakesh (2023) Soft-materials with SOMs and Surfactants as a Model System to Study Elementary Phenomenon to their Application in Catalysis. PhD thesis, Indian Institute of Science Education and Research Kolkata.

Text (PhD thesis of Rakesh Sen (17RS033)) 17RS033.pdf - Submitted Version Restricted to Repository staff only Download (69MB)

Abstract

This thesis investigates soft materials in the context of phase transitions, an elementary phenomenon which is the manifestation of perturbations in inter-particle interactions between constituting building blocks induced by employing external stimuli. It also analyzes the possibility of applying these systems in the development of model platforms to explore their applications in site-specific sustainable catalysis and in understanding the dynamics of fundamental forces in the origin of matter in this universe in the context of space-time symmetry breaking, which is also one of the crucial aspects of phase transitions. In our earlier endeavours, we had developed a simple and cost-effective method known as Micro-Bubble Lithography (MBL) to pattern soft materials into ‘lab-on-a-chip’ platforms using phase transitions of oxometalate entities from soft colloidal phase to crystalline phase in thermooptical tweezer set-ups and used this technology to fabricate disease-detecting bio-chips, conducting materials and in the development of site-specific micro-reactors as proof of concept. In the current study, we notched a level up by exploring selectivity in organic reactions on these micro-catalytic platforms. Here, we have taken an oxometalate, TBA₆[PV₃W₉O₄₀], as the main catalytic component together with Multi-walled carbon nanotubes (MWCNT) and Polypyrrole (PPy) as the supporting instruments in a pre-catalyst precursor cocktail to fabricate micro-catalytic trails where we have observed selective oxidation of anilines to nitroarenes with high conversion (83%) and selectivity (95%). Further, on these micro-catalytic platforms, we have achieved synergistic silencing of sitedirecting electronic effects of functional groups already present in aromatic systems by suitable interface engineering to create an oxo interface as preferable docking sites for incumbent substrate molecules, which is evident from the unusually similar percentage conversions and nitro-selectivity from the substrate scope. Next, we have explored the possibility of using these micro-catalytic trails as microelectrodes in electrochemical reactions. We have patterned ZIF-67 trails and used these trail assemblies in electrocatalytic water oxidation reactions where we have achieved an overpotential of ~800 mV (without iR compensation) for oxygen evolution reaction. Further, this dissertation also investigates the possibility of using these soft matter systems to model elementary phenomena. Here, we have taken a surfactant molecule cetyltrimethylammonium bromide (CTAB) as charge responsive model system and induced a phase transition by perturbing its space-time symmetry by applying an external electrical field in an electrochemical workstation which can be approximated to the classical electroweak forces operational in the creation of matter according to the standard model. The subsequent phenomenological model extracts temporal and spatio-temporal information regarding this phase transition, which shows the whole phenomenon is an out-of-equilibrium process and, at the same time, establishes this soft matter system as a model simulator to understand the origin of matter by representing an asymptotic explosion just the way matter is created or being created in the expanding universe. These endeavours will surely help us to understand the soft matter systems in terms of their tuneable functionalities, which can be achieved by modulating the chemical natures of the building blocks and the interactions employed amongst them and the nature of external stimuli which can churn up significant response factors which is a crucial feature of these materials. Venturing into this domain also promises a wide range of applications in the soft matter domain.

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