Sodium-ion batteries (SIBs) are rechargeable batteries analogous to lithium-ion batteries but use sodium ions (Na+) as the charge carriers. They are considered a promising alternative for lithium-ion batteries (LIBs) in renewable large-scale energy storage applications due to their similar electrochemical mechanisms and abundant sodium resources. Two-dimensional (2D) materials, with atomic or molecular thickness and large lateral lengths, have emerged as important functional materials due to their unique structures and excellent properties. These 2D nanosheets have been highly studied as sodium-ion battery anodes. They have large interlayer spacing, which can effectively buffer the big volume expansion and prevent electrode collapse during the charge-discharge process. Different strategies such as preparing composites, heterostructures, expanded structures, and chemical functionalization can greatly improve cycling stability and lead to high reversible capacity. In this dissertation, state-of-the-art SIB based on 2D material electrodes will be presented. In particular, Tin-based 2D materials and laser-scribed graphene anodes are discussed. Different strategies involving engineering both synthesis methods, intrinsic properties of materials, and device architecture are used to optimize the battery performance.

Recently, laser scribed graphene (LSG) technology has shown great potential for the development of a plethora of sensing platforms due to its high sensitivity, 3D porous structure, and flexibility. Molecularly imprinted polymers (MIPs) have shown high potential as recognition elements for many applications such as biosensing. Hence, we report in this thesis a novel biosensing platform that utilizes nanostructured gold to enhance the performance of LSG sensors coupled with a biomimetic MIP biosensor. To the best of our knowledge, this is the first report of a nanostructured gold modified MIP based LSG biosensor to detect HER-2, which is an important breast cancer biomarker. HER-2 positive breast cancer is more aggressive and does not respond to the same treatment as standard breast cancer. As such, a simple and accurate sensing approach is highly needed for early detection of this type of cancer biomarkers. The LSG sensor platform was fabricated by irradiation of polyimide substrates using a CO2 laser under optimized conditions. Nanostructured gold was electrodeposited onto LSG to enhance its sensitivity and active surface area. Deposition parameters such as deposition voltage, deposition time, and gold chloride (HAuCl4) concentration were optimized to yield complete nanostructured gold coverage and enhanced electrical conductivity of LSG-Au electrodes. A deposition voltage of -0.9 V at 50 mM HAuCl4 for 4 minutes proved to be the optimal condition for gold deposition to yield a 150% peak current enhancement. To fabricate our MIP biosensor, 3,4- ethylenedioxythiophene (EDOT) was chosen from several functional monomers to form PEDOT due to its high conductivity and synergy with nanostructured gold. Electropolymerization of EDOT is performed after adsorbing 0.4mg/mL of HER-2 on the LSG-Au electrode for 20 min. The efficiency of LSG-Au-MIP was optimized by choosing an appropriate extraction agent and HER-2 concentration to be adsorbed on gold. The developed sensing strategy could differentiate between three rebinding concentrations of 10 ng/mL, 100ng/mL, and 200 ng/mL, which is sufficient to determine the HER-2 status of breast cancer since the clinical cut-off is 30.5ng/mL. The developed sensing strategy showed a high degree of novelty and could be useful for the non-invasive detection of cancer biomarkers.

Electrochemical sensing platforms including nanostructured materials have attracted increasing attention for diagnostic applications in recent decades. People in resource-limited places, particularly in low- and middle-income countries, continue to face problems finding high-quality medical treatment and technologies. This thesis aims to create affordable electrochemical-based point of care (PoC) diagnostic systems using laser-scribed graphene (LSG) material as the sensing platform. The use of LSG sensors for diagnostic purposes has been gaining attention. Compared to established methods for graphene synthesis, laser scribing provides many advantages, such as cost-effectiveness, fast electron mobility, mask-free production, green synthesis, good electrical conductivity, porosity, mechanical stability, and large surface area. Surface enhancement techniques hold great importance for sensitive and selective electrochemical performance. The first part of this dissertation includes the LSG fabrication and the possible nanoparticle deposition effect on LSG surfaces, particularly gold and silver nanoparticles. The electrodeposition technique was chosen to enhance the electrocatalytic activity with high surface coverage, higher sensitivity, and ease of surface modification. We also focused on possible surface activation techniques on LSG electrodes to achieve an enhancement in surface area through electrochemical strategies. In the second part of this dissertation, we focus on surface functionalization methods for the development of self-diagnostic devices. Namely, the LSG surface was engineered by recognition units such as antibodies, enzymes, and aptamers, as well as molecular imprinting as a non-biological approach. As a readout system, a custom-made potentiostat called KAUSTat was developed. The suggested devices have the potential to replace costly health care instrumentation with simple and practical miniaturized smart systems when combined with smartphone applications via Bluetooth connection.