Carbon based nanomaterials and perovskite oxide based interfaces for sensing and energy applications

Abstract

Nanotechnology offers transformative pathways for addressing environmental and energy challenges, and this thesis explores two distinct yet complementary approaches: biomass-derived carbon dots (CDs) for sensing and remediation, and perovskite oxide heterostructure interfaces for photovoltaic applications. Fluorescent CDs were synthesized through sustainable hydrothermal methods using plant-based precursors such as Typha angustata and Kalanchoe pinnata. Nitrogen and sulfur co-doped CDs (N,S-CDs) exhibited strong fluorescence, excellent water solubility, and stability, enabling highly sensitive detection of Hg²and#8314; and cysteine with detection limits of 3.1 nM and 8 nM, respectively, while nanocomposites (SCNFsatCDs) derived from hemp cellulose demonstrated dual functionality for detecting and adsorbing UOand#8322;²and#8314; ions, achieving a detection limit of 1.6 nM, an adsorption capacity of 196.07 mg gand#8315;¹, and outstanding recyclability, thus showing significant promise for wastewater treatment. The second part of the work focuses on LaVOand#8323;/KTaOand#8323; (001) oxide heterostructures fabricated by pulsed laser deposition, where a two-dimensional electron gas (2DEG) at the interface exhibited intriguing photoresponse behavior. Under illumination, the interface showed enhanced conductivity (photoconductivity) and generated a photovoltaic effect upon gate voltage application, with the polarity of the photocurrent tunable by reversing the gate bias. This unique gate-dependent control over the photovoltaic response establishes these heterostructures as promising candidates for multifunctional optoelectronic devices capable of integrating energy harvesting and detection. Overall, this thesis presents an eco-friendly, cost-effective, and innovative approach that combines green nanomaterials for pollutant sensing with advanced oxide interfaces for energy applications, offering sustainable solutions for clean water and renewable energy technologies. newline