Babar, Zaheer Ud Din (2024) Fabrication of MXene-Based Electrochemical Transducers: Synthesis, Characterization, and Performance Evaluation. [Tesi di dottorato]

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Abstract

The growing demand for smart, fast, and flexible multitasking devices has driven researchers to explore innovative materials. Among these, two-dimensional (2D) materials, such as MXenes (Mn+1XnTx) have emerged as particularly promising candidates. Since their discovery in 2011, MXenes have demonstrated significant potential in various fields, including energy storage and sensing. Their ease of processing, metal-like conductivity, large surface area, and tunable properties make them particularly suitable for transducer research, offering enhanced signal-to-noise ratios and improved sensitivity. Most studies on Ti3C2Tx MXenes have focused on complex composites or electrode modifications, often using drop-casting methods on glassy carbon electrodes (GCE). The bulk nature of these collectors restricts their use in point-of-care (POC) devices, and reliance on complex composites obscures the intrinsic properties of MXene, such as conductivity, resulting in an incomplete understanding of their electrochemical sensing mechanisms. Pristine Ti3C2Tx MXene offers untapped potential for novel sensor development, which remains underexplored. Addressing these challenges requires the development of straightforward, cost-effective, and scalable fabrication techniques for MXene-integrated electrochemical transducers. Recent studies on vacuum-filtered films of nanomaterials (e.g., graphene) and their deposition on flexible substrates (plastic/paper) have demonstrated promise in flexible-sensing applications. However, research on MXene films for electroanalytical applications is still limited. Therefore, this doctoral dissertation focuses on creating pristine MXene electrodes using standardized fabrication methods such as vacuum filtration, to fully explore their fundamental properties. The primary objective of this dissertation was to synthesize high-quality, reproducible Ti3C2Tx MXene and develop a simple, lab-feasible approach to fabricating MXene-based screen-printed electrodes (MSPEs). Chapter 1 presents an overview of the topic, briefly introducing the experimental activities undertaken and explaining the thesis structure. Chapter 2 provides a comprehensive background on MXenes and their role in sensing applications. It discusses conventional transducers and examines how nanomaterials, particularly MXenes, enhances transducer performance. By analyzing current trends and challenges in MXene transducer development, this chapter identifies knowledge gaps and sets the objectives of this PhD research. Chapter 3 details the synthesis process of Ti3C2Tx MXene, focusing on the two-stage etching and delamination methods to ensure consistent production of high-quality MXene nanosheets. The synthesized MXene was characterized through XRD, SEM, TEM, and XPS, confirming its structural and chemical properties. Chapter 4 introduces a novel wax-assisted templating and stamp transfer method for fabricating MXene electrodes on flexible substrates. This chapter documents the process step-by-step, including the tools, equipment, and design configurations, to support efficient production. The morphology and electrical properties of the stamp electrodes are analyzed, with detailed illustrations and schematics to help in understanding the procedure. In Chapter 5, the electrochemical performance of the fabricated MSPEs is evaluated using a 5mM solution of Hexaammineruthenium (III) chloride [Ru (NH3)6] Cl3 in 0.1M potassium chloride (KCl) as a redox probe. The influence of electrode shape, concentration, and filtrate volume on the performance is assessed, alongside a reproducibility analysis. Results show that the wax-templated method yields MXene electrodes with reproducible electrochemical responses across different electrode batches, validating this method as a viable manufacturing technique. In conclusion, this dissertation addresses the key challenges in the fabrication of pristine MXene and MXene-integrated devices, presenting a straightforward and scalable approach for developing high-performance electrochemical sensors. These findings have the potential to significantly impact current practices in MXene-based sensor research and device fabrication.

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