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Abstract

This thesis investigates biosensing and gas sensing devices using two-dimensional (2D) materials, such as molybdenum disulfide (MoS₂) and indium selenide (In₂Se₃). These materials offer high surface-to-volume ratios, tunable electronic properties, and simple fabrication processes, enabling the development of highly sensitive, label-free sensors for healthcare and environmental monitoring.

The research explores four distinct sensor platforms, each focusing on the detection of specific biomarkers associated with various diseases. First, an asymmetric MoS₂ diode-based biosensor functionalized with tumor necrosis factor-α (TNF-α) binding aptamers is introduced, achieving a detection limit of 10 fM. This sensor leverages changes in surface energy to alter current-voltage rectification behavior, offering a promising tool for point-of-care diagnostics. Second, a self-powered MoS₂-based sensor is developed for volatile organic compound (VOC) detection. Using an asymmetric contact geometry, the sensor generates an internal electric field, enabling self-powering under UV light. It demonstrates high responsivity (60%) and fast response times (10 seconds) to acetone concentrations as low as 200 ppm, making it ideal for portable VOC monitoring.

Third, a novel semiconductor-liquid heterostructure sensor is presented for detecting glial fibrillary acidic protein (GFAP), a biomarker associated with neurological disorders. Utilizing the negative differential resistance (NDR) effect and antibody-GFAP interactions, the sensor achieves a detection limit of 1 fM, showcasing its potential for rapid, label-free neurological diagnostics. Finally, a flexible VOC sensor based on α-In₂Se₃ flakes is explored. Operating at room temperature, it detects lung cancer biomarkers such as 2-butanone and 1-propanol with limits as low as 176 ppb, rapid response/recovery times (3 and 15 seconds), and over 80% performance retention on flexible substrates, highlighting its suitability for wearable applications.

Through these developments, this thesis contributes to advancing the field of biosensing by demonstrating the versatility and transformative potential of 2D materials in creating next-generation diagnostic and monitoring tools for healthcare and environmental applications.

Keywords: 2D Materials; Biosensors; Gas Sensors; Biomarkers; VOCs