Theses and Dissertations

Date of Award

8-2025

Document Type

Thesis

Degree Name

Master of Science in Engineering (MSE)

Department

Mechanical Engineering

First Advisor

Victoria Padilla

Second Advisor

Javier Ortega

Third Advisor

Javier Macossay-Torres

Abstract

Since the development of the first biosensor in 1962, the evolution of commercially available wearable biosensors has been driven by an increasing consumer interest in real-time health tracking. However, challenges related to sensor sensitivity and cost have hindered progress. Deploying a novel approach, the biosensor integrates a blend of Polyaniline (PANi) and Polyethylene Oxide (PEO) along with Nitrogen-doped Graphene Quantum Dots (N-GQDs) to enhance sensitivity and electroactivity, crucial for cortisol detection. To optimize performance, three distinct synthesis methods for N-GQDs; hydrothermal, microwave, and hot plate synthesis were compared employing a bottom-up approach utilizing citric acid (CA) as the primary reactant for graphene production. The efficiency of each synthesis method were evaluated based on sensitivity to cortisol detection. Characterization techniques employed included UV-Vis spectroscopy for n-π* confirmation, Photoluminescent spectroscopy for emission spectrum analysis, and atomic force microscopy (AFM) for size and quantity determination of N-GQDs . The N-GQDs were uniformly dispersed throughout the PEO/PANi film, facilitating even distribution, and enhancing the attachment of antigens and enzymes for cortisol detection. Electrochemical analysis was conducted utilizing cyclic voltammetry (CV), while characterization techniques such as, Fourier-transform infrared spectroscopy (FTIR), Raman spectroscopy, and atomic force microscopy (AFM) were used to assess the structural and chemical properties of the biosensor.

Comments

Copyright 2025 Cesar Sanchez. All Rights Reserved. https://proquest.com/docview/3253956297

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