1. Ph.D Theses
Permanent URI for this collectionhttps://idr.nitk.ac.in/handle/1/11
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Item Even D- Carbon Nanostructures for Sensing and Energy Applications(National Institute of Technology Karnataka, Surathkal, 2020) Mishra, Praveen.; Bhat, B Ramachandra.The thesis titled “Even-D Carbon Nanostructures for Sensing and Energy Applications” encompass the work on Even-D carbon nanostructures, particularly graphene and graphene quantum dots for the prospective use as materials for sensors and photovoltaic devices. A new route to obtain the quantum dot by bombarding the graphene oxide (GO) sheets with the swift heavy ions is discussed. The graphene quantum dots (GQD) in their native state were found to be highly useful in determining the metal cations like Ca2+, Cu2+, and Co2+. The determination of Ca2+ ions in the water was quantitatively possible in the presence of interfering ions such as Al3+, Na+, and K+. However, the detection of transition metals with GQD remains only qualitatively feasible, because transition metals non-selectively quench the PL of GQD. The amine functionalized GQD (NH2-GQD) made the quantitative determination of glucose possible via aggregation induced photoluminescence enhancement with an accuracy of 98%. The NH2-GQD-GO composite proved to be an active material for the electrochemical determination of oxalic acid within 0.5 mM to 55 mM and a limit of detection of 50 μM. The NH2-GQD were also demonstrated to be an excellent cosensitizer for the hybrid quantum dot solar cell when used in conjunction with anthocyanin dye. The photosensitizer combination improved the photon conversion efficiency by ~50%. Significant raise in other parameters was also observed. The work presented in this thesis demonstrates the utilization of the excited electron resulted by the electromagnetic irradiation on the GQD. It is evident that the energy emitted by the electron returning to the ground state is utilized for photoluminescent detection of various analytes. The extraction of excited electron through electrochemical means resulted in making GQD based electrochemical sensors and co-sensitizers in the photovoltaic devices.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.