1. Ph.D Theses
Permanent URI for this collectionhttps://idr.nitk.ac.in/handle/1/11
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Item Perovskite Alkaline Earth Titanates Based Nanomaterials as Photocatalysts(National Institute of Technology Karnataka, Surathkal, 2023) B, Harsha; Bhat, D. KrishnaThe research thesis entitled ‘Perovskite alkaline earth titanates based nanomaterials as photocatalysts’ deals with the synthesis, characterization and photocatalytic studies of some doped perovskite alkaline earth titanates and porous graphene-perovskite alkaline earth titanate nanocomposites. The present study reports the successful synthesis of seven different series of novel perovskite alkaline earth titanate-based materials namely, Rh-doped SrTiO3, V-doped SrTiO3, porous graphene-SrTiO3 nanocomposite (PGST), Rh-doped BaTiO3, porous graphene-BaTiO3 nanocomposite (PGBT), V-doped CaTiO3 and porous graphene-CaTiO3 nanocomposite (PGCT) using facile solvothermal/hydrothermal method. All the synthesized materials were carefully characterized for their elemental composition, structural, morphological, and optical properties by employing appropriate techniques such as XRD, FESEM, EDS, TEM, HRTEM, Raman Spectroscopy, XPS, BET, DRS, and PL spectroscopy. Thereafter, each material was investigated for its catalytic efficiency towards the degradation of methylene blue dye under visible light irradiation. The synthesized materials exhibited enhanced photocatalytic efficiency which could be attributed to the efficient visible light harvesting capacity and reduced rate of recombination of photoinduced charges.Item Theoretical Study of Functionalized Two-Dimensional Materials towards their Application in Supercapacitors(National Institute of Technology Karnataka, Surathkal, 2021) T, Sruthi.; Tarafder, Kartick.This thesis investigates possible roots to enhance the quantum capacitance(CQ) of two-dimensional materials based electrodes for supercapacitor applications through density functional theory(DFT) calculations. In this work, various two-dimensional materials such as graphene, molybdenum disulfide(MoS2), and hexagonal boron nitride(h- BN) have been considered, subsequently, chemical functionalization of these systems has been performed to manifest the high quantum capacitance. The quantum capacitance of functionalized systems was estimated from the precise electronic band structures of the system obtained by using DFT calculations. It has been observed that ad-atom functionalization of graphene can significantly enhance the quantum capacitance of the system. Therefore, in the first stage, the quantum capacitance of ad-atom doped graphene with a varying doping concentration has been systematically studied. The effect of temperature on quantum capacitance has also been investigated. The temperature-dependent study of CQ for functionalized graphene shows that the CQ remains very high in a broad range of temperatures close to room temperature. In the second stage, the graphene functionalization has been done by doping with different aliphatic and aromatic molecules and their radicals. Our theoretical investigation reveals that aromatic and aliphatic radicals introduce localized density of states near the Fermi level of the functionalized systems, due to a charge localization which in turn significantly enhances the quantum capacitance of the system. The effects of atomic dislocation on graphene during functionalization has also been incorporated in our investigation. In the third stage, we have carried out our investigation in other two-dimensional materials such as MoS2 and h-BN. Attempts have been made to enhance the quantum capacitance of these systems by introducing defects as well as performing chemical fictionalizations. The detailed study in this thesis suggests an efficient way to produce functionalized materials using two-dimensional materials that could be very suitable electrode materials of highly efficient supercapacitors.Item Carbon Nanocomposite Materials for Non-Enzymatic Electrochemical Glucose Sensing(National Institute of Technology Karnataka, Surathkal, 2017) Prasad J, Raghavendra; B, Ramachandra BhatUnique and Extraordinary electrical and mechanical properties of carbon nanotubes (CNTs) and their composites have stimulated extensive research activities across the world since their discovery by Sumio Iijima in 1991. The range of application of CNTs is indeed wide as it ranges from nano-electronics, with quantum wire interconnects and field emission devices to composites, chemical sensors and biosensors. However, because of low production capacity and high production costs at present, their applications cannot be extended until large-scale production is achieved. In present research work titled “Carbon nanocomposite materials for nonenzymatic electrochemical glucose sensing”, the principal objective is to synthesize bulk scale CNTs and explore the possible application to design efficient, improved and economical non-enzymatic glucose sensor. The work describes eco-friendly synthesis of CNTs and its metal oxide composites (NiO-MWCNT, CuO-MWCNT and Co3O4) using metal formates as an eco-friendly precursor by low temperature thermal reduction method using chemical vapour deposition. The surface and structural morphology were studied by FESEM, TEM, whereas, elemental composition was determined by XRD and Raman spectroscopy. Using these materials the modified glassy carbon electrodes were fabricated to investigate the electro-catalytic properties towards the direct glucose oxidation. The electrochemical properties were characterised by cyclic voltammetry and chronoamperometry techniques in NaOH electrolyte. The sensor parameters like sensitivity, selectivity, stability, reproducibility, response time, limit of detection (LOD) and linear concentration range was investigated for the fabricated electrodes and results obtained were compared with the ones reported in literature. It is notable that the composite materials show significantly enhanced catalytic performance towards direct glucose oxidation due to the synergistic effect of carbon nanomaterials and metal oxide. This composite martials also shows properties like high surface area, fast electron movement, biocompatible and antifouling properties, etc. making these material as promising candidate for the fabrication of non-enzymatic glucose sensors.Item Preparation, characterization and applications of graphene and its composites(National Institute of Technology Karnataka, Surathkal, 2018) M, Sreejesh; Nagaraja, H. S.The preparation, characterization and applications of graphene and its composites are investigated in this thesis. Solar exfoliation, a relatively simple and viable method, is used for the production of the reduced graphene oxide. The prepared graphene oxide is tested for applications in supercapacitors and electrochemical sensor for hydrogen peroxide, which is an important chemical species in the biological systems. Later on, vanadium oxide –graphene composite has been prepared and characterized. The prepared composite has been used as sensor for dopamine detection at nanomolar range, a neurotransmitter which can be vital in finding the irregularities related to Alzheimer’s detection. A better performance in terms of lower detection limit (0.07 µM) and sensitivity (25.02 µA mM-1 cm-2) is reported. Also, Lithium ion batteries are fabricated using the prepared composites and the composite offers a good capacitance of around 200 Fg-1. The fifth chapter describes the preparation of zinc oxide - graphene composites. The electrochemical sensor fabricated using zinc oxide - graphene oxide composite was found to be sensitive towards glucose, which is important in the control of diabetes mellitus. Also, supercapacitors electrodes were fabricated and tested using above composites reveals promising performance with hghest specific capacitance of 635 Fg-1.Item Graphene - Metal Tungstate Nanocomposites for Catalytic Applications(National Institute of Technology Karnataka, Surathkal, 2018) Sadiq M, Mohamed Jaffer; Bhat, D. KrishnaThe research thesis entitled ‘Graphene - Metal Tungstate Nanocomposites for Catalytic Applications’ deals with the synthesis, characterization and studies on catalytic properties of some graphene - metal tungstate nanocomposites. The work describes successful synthesis of five different kinds of novel graphene-metal tungstate based nanocomposites namely, NRGO/ZnWO4/Fe3O4, NRGO/NiWO4/ZnO, NRGO/CoWO4/Fe2O3, NRGO/FeWO4/Fe3O4 and NRGO/BaWO4/g-C3N4 using facile microwave irradiation method. All the synthesized nanocomposites were carefully characterized for their elemental composition, structural, morphological and optical properties by employing appropriate techniques such as, XRD, SEM, FESEM, TEM, HRTEM, BET, XPS, DRS, Raman, FTIR, UVVis and PL spectroscopies. Thereafter, each nanocomposite was investigated for its catalytic efficiency towards, (i) The photodegradation of methylene blue dye under the visible light irradiation, (ii) The reduction of 4-Nitrophenol to 4-Aminophenol by sodium borohydride in aqueous media and (iii) The electrocatalytic hydrogen evolution reaction in alkaline media. The synthesized nanocomposites exhibit high catalytic activity due to the synergistic effects of the components of the nanocomposite materials. The reusability of the catalysts in all the above processes is also good. Therefore, the observed results suggest that these novel graphene - transition metal tungstate based ternary nanocomposites are potential candidates as multifunctional catalysts in the field of clean energy and environmental applications.