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Exploring Charge Storage Mechanism in MXene as Supercapacitor Electrode: A First-Principles Approach
The exfoliation of layered transition metal carbides/nitrides, MXenes (Mn+1Xn), from its 3D precursor MAX is remarkable event in the history of 2D materials. Ti3C2 , the first discovered MXene, caught everyone’s attention due to its excellent charge storage capacity as a supercapacitor electrode. It has been the most explored MXene in this 2D subfamily. 70% of the MXene research is on this compound only. Baring Ti3C2 , various other transition metal-based MXenes have been synthesized to date. This 2D subfamily exhibits diversity in structure and composition. MXene is enormously famous due to its performance as an energy storage device. The high electrical conductivity, hydrophilicity, surface redox activity, and mechanical stiffness make it a potential alternative to Graphene as an electrode in energy storage devices like batteries and supercapacitors. Experimental evidence suggests that diversity in structure, composition, and surface passivations affect the supercapacitive property of MXenes. However, there are a few scattered attempts to explore these aspects for varieties of systems to understand the mechanisms of charge storage in MXene-based supercapacitors. This thesis provides a systematic study on understanding structural and compositional effects on the electrochemical performances of MXene-based supercapacitors. Our investigations start with exploring the capacities of M 2 C and M 3 C 2 MXenes as supercapacitor electrodes. We consciously choose various 3d and 4d transition metals as M elements. We show the significance of quantum capacitance on energy storage performance. We also explain the effect of surface passivation on MXene capacitances. Further, we provide a comparative study of substitution and doping in enhancing the storage capacity of MXenes. An explanation of the influence of doping sites on the redox capacitance of Ti 3 C 2 is given. Next, we attempt the route of surface engineering to improve the energy storage capacities of MXenes. To this end, we construct Janus MM’C MXene and study their electrochemical performances. In the course of this study, we find that much superior capacities are obtained if one of the components of Janus is a magnetic element. We extend the study by considering solid solutions of one of these systems and investigating the effect of chemical and magnetic disorders on its supercapacitive performance.
Utilization of Steel Industry LD-slag for Environmental Applications
Steel slag is an industrial byproduct of the steel-making process. It is created in enormous amounts during steel production using electric arc furnaces. LD-slag, also known as LD (Linz-Donawitz) converter slag, is a byproduct of steelmaking in a basic oxygen furnace. This kind of slag is typically created during the steelmaking process from iron ore. The LD-slag comprised several hazardous metallic oxides therefore, dumping such waste may cause several detrimental effects on the environment. The global output of LD-Slag is around 47 MT per year. As a result, there is a strong case to be made for making extensive use of LD-slag, either through conversion into useable material or recycling as process material. Taking all these above issues into consideration, the main objectives of this work are divided into four sections. The first section deals with wastewater treatment by different zeolites derived from LD-slag of the steel industry. The second section deals with the preparation of zeolites A and X and their physico-chemical study.
Application of Modified Smooth Exterior Scaling Method to Study Auger and Shape Resonances in Different Atomic and Molecular Systems
This thesis focuses on the application of modified smooth exterior scaling (MSES) as an efficient method to impose outgoing boundary conditions in e-atom and e-molecule scattering resonances. This is the first time that the MSES method has been applied to calculate energies and widths of Auger and shape resonances in three-dimensional many-body electron systems. MSES converts the divergent resonance wave functions into square integrable ones thereby making the study of temporary bound states (resonance states) amenable to bound state electronic structure methods. The main objective of this thesis is to formulate the MSES method in bivariational SCF and electron propagator methods.
N- and O- Donor Ligands for Fluorometric and Colorimetric Detection of Metal Ions
This Thesis contains five chapters. Chapter 1 is the introduction which describes the contribution of metals in our daily lives and their adverse effects on human beings when exposed to excess amounts along with a brief elaboration of different detection techniques. Some recent developments in devising fluorescent and colorimetric probes are also discussed. In Chapter 2 the 2,4,5-tris(2-pyridyl)imidazole (L1H) molecule has been evaluated as a probe for dual sensing of Hg2+ and Cu2+ ions in EtOH/HEPES buffer medium (5 mM, pH = 7.34, 1:1, v/v). Probe L1H shows a good sensitive and selective turn off response in the presence of both Hg2+ and Cu2+ ions, which is comprehensible under long UV light. Its sensitivity was evaluated in different pH medium and in presence of other metal ions. Paper strip experiments and in-vitro cell imaging was done to know the sensitivity of the probe towards the metal ions in different environment. Chapter 3 describes the probe 2,6-di(2-pyridyl)-1,5-dihydroimidazo[4,5-f]benzimidazole (L2H2) and its sensing application towards metal ions. This probe could detect Zn2+ and Cd2+ ions in three different aqueous systems viz., water, DMSO/HEPES buffer (1:1, pH = 7.34, rt), and DMSO/water (1:1, rt). In water a “turn-on” response was observed for both metal ions, whereas in the latter two solvent systems, a ratiometric change in fluorescence maximum was observed. The detection limit of this probe was as low as 0.3 μM and 0.62 μM (in water) for Zn2+ and Cd2+ ions, respectively. In Chapter 4 synthesis and evaluation of a novel probe N'-(pyren-1-ylmethylene)benzo[d]imidazo[2,1-b]thiazole-2-carbohydrazide (L3H) as metal ion sensor was explored. It was found to be able to nanomolar detection of Pd2+ and Ni2+ ions by colorimetric change. This probe was also able to detect the presence of Pd2+ ions in drug samples and APIs without any major interference. LOD values were calculated to be 46.1 to 93.9 nM (4.9 to 6.0 ppb) for PdCl2 and 10.6 to 19.6 nM (1.1 to 2.1 ppb) for Pd(PPh3)2Cl2 and 9.301 nM for NiCl2 solutions. It also showed extremely good recovery of Pd2+ in presence of all the drug molecules. In Chapter 5 another novel ligand L4H based on 2,7-dichlorofluorescein was synthesized and evaluated for sensing applications. It was found to be able to detect Co2+ and Cu2+ ions differentially by different colouration of the solution in presence of these two metal ions. In situ Cu-complex of the ligand was utilised for quantification of amino acids like BSA and HSA proteins. Its differential selectivity paved the for molecular logic gate application.
Designing Innovative Smart City : User-Centric Framework and Inclusive Strategy
The trend of Smart Cities has fascinated the ambitions of citizens and Governments worldwide. This race has led to the development of huge infrastructures embedded with Hi-tech services for the comfort of city dwellers. In many places, it was observed that the technology was adopted blindly without analyzing the prevailing conditions of the area or the requirements of the population. It resulted in the development of hi-tech ghost towns around the globe. After the completion of such hi-tech townships, policy makers face difficulty attracting occupants. It raises the question of whether to consider such hi-tech projects successful, where technology and environmental realms have attained a level of sanctity but failed to include a human scale.