Date of Award
8-1-2025
Degree Name
Master of Science
Department
Chemistry
First Advisor
Shamsi, Mohtashim H.
Abstract
The kinetics of charge transfer at modified electrode surfaces must be understood to develop electrochemical biosensing platforms. The charge transfer behavior at indium tin oxide (ITO) electrodes modified with molybdenum disulfide (MoS₂) is investigated in this work for applications employing nucleic acid-based biosensing. Two-dimensional (2D) MoS₂ nanoparticles are a suitable choice for electrochemical sensing due to their exceptional electrical properties, strong biomolecular adsorption ability, and large surface area. We investigate the charge transport and electrostatic interactions at the MoS₂/ITO interface using [Ru(NH₃)₆]³⁺/²⁺ as a redox probe. We investigate the charge transport and electrostatic interactions at the MoS₂/ITO interface. To further understand biomolecular interactions and their consequences on the electrical double layer, we investigate the adsorption of DNA (ss-DNA, ds-DNA) and locked nucleic acids LNA, ss-LNA, and ds-LNA onto MoS₂ with and without monovalent and divalent ions. Chronocoulometry measures surface charge fluctuations and distinguishes between double-layer capacitance (Qdl) and adsorbed charge (Qads) using the Cottrell and Anson equations, while cyclic voltammetry gives information on electron transport kinetics. The insertion of monovalent and divalent ions permits charge screening, which permits the calculation of charge transfer kinetics at the probe because MoS₂ has an intrinsic negative charge, and DNA and LNA have negatively charged phosphate backbones. Additionally, atomic force microscopy (AFM) is used to investigate charge fluctuations on the MoS₂ surface. Better electrochemical sensing technologies for environmental monitoring and disease diagnosis are made possible by the findings of this work, which significantly contribute to the development of label-free, MoS₂-based biosensors.
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