2D Materials: Investigating Graphene, MXenes and other 2D Materials For Applications In Energy Storage, Electronics And Biomedicine

1179 Publisher: EDUCATION GENIUS SOLUTIONS Review Type: Double Blind Peer Review Vol. 3 No.4 2025 Research Consortium Archive P(ISSN) : 3007-0031 E(ISSN) : 3007-004X https://rc-archive.com/index.php/Journal/about 2D Materials: Investigating Graphene, MXenes and other 2D Materials For Applications In Energy Storage, Electronics And Biomedicine Muzammil Ahmad Department of Physics, Bahauddin Zakariya University Multan Email: shujaba[email protected] Muhammad Ramzan Department of Chemistry, COMSATS University Islamabad Email: [email protected] Iqra Irshad Center of Excellence Solid State Physics, University of the Punjab Email: iqrairsha[email protected]m Muhammad Naeem Department of Chemistry, Islamia University Bahawalpur Email: [email protected] Mudasir Mushtaq Department of Chemistry, COMSATS University Islamabad Email: mudasir[email protected] 1180 The advent of two-dimensional (2D) materials has provided breakthrough opportunities in the technological innovation in a variety of fields. In this abstract, the author explores the specificities of properties and possible applications of graphene, MXenes, and other 2D materials in addition to graphene, including transition metal dichalcogenides (TMDs), and hexagonal boron nitride (h -BN). They are very versatile because of their exceptional features, such as, high specific surface area, excellent electrical and thermal conductivity, tunable surface chemistry, and excellent mechanical strength. These materials play a central role in the energy storage by creating next-generation supercapacitors and high-energy-density batteries, where MXenes and graphene improve the conductivity of the electrodes and accessibility to ions. In electronics, TMDs are a semiconducting material with the ultra-high carrier mobility of graphene used to make receivable flexible and transparent conductors, high-spatial-resolution transistors, and other novel optoelectronic brands. Moreover, 2D biocompatibility and large surface area are used in biomedicine to create the nextgeneration biosensing, targeted drug delivery systems, and novel antibacterial therapies. Although the future is bright, issues of scalable cost-effective production and an in-depth knowledge of their long-term environmental and biological interactions are still problems under research. Further development of this wide material family is on the verge of making groundbreaking breakthroughs in the fields of sustainable energy, miniaturization of electronics and customized medicine. Keywords: Areas of interest Graphite, Transition Elements, Electronics, Biomedical Technology, Energy Storage, Biosensing Techniques, Nanostructures. Introduction In 2004, the breakthrough of graphene, a single sheet of carbon atoms arranged in a hexagonal pattern, marked a landmark in materials science and signaled the dawn of two-dimensional (2D) materials (Xiang et al., 2022). The discovery made Andre Geim and Konstantin Novoselov win the Nobel Prize in Physics in 2010 (Bais, 2024). It showed that materials can be stable, free-standing, and exhibit exceptional behavior when reduced to a single atomic plane. The outstanding properties of graphene, such as unmatched electrical and thermal conductivity, unmatched mechanical strength, and a high specific surface area, have driven a worldwide research effort to investigate a broader family of 2D materials (Liu et al., 2022). This growth has extended beyond the graph (graphene) to a wide range of compounds, including transition metal dichalcogenides (TMDs) such as MoS2 and WS2, insulating hexagonal boron nitride (h-BN), and, most recently, the family of MXenes, which are rapidly growing. It is this wide range of 2D materials with distinct electronic, optical, and chemical characteristics that is now poised to enable innovation across a myriad of applications, such as energy storage, electronics, and biomedicine (Chen et al., 2020). The feature of 2D materials is their confinement in a single direction, resulting in a significant aspect Ratio and a large accessible surface area (Zhu et al., 2021). This geometry leads to quantum confinement effects that fundamentally change their electronic structure compared to that of their bulk counterparts. For example, whereas graphene is a semimetal with very high charge-carrier mobility, MoS2 in the bulk phase has an indirect bandgap. Still, in the monolayer form, it has a direct bandgap and is a promising optoelectronic semiconductor (Chaves et al., 2020). The family of ABSTRACT 1181 2D transition-metal carbides, nitrides, and carbonitrides known as MXenes is typically prepared by etching the "A" layer of the corresponding MAX phase starting materials. The result of this process is the production of metallically conductive materials that have hydrophilic surfaces and rich chemistry, which can be custommade to meet the requirements of the material (Bokov et al., 2021). The fact that these 2D building blocks can be mixed and matched, similarly to Lego bricks, to form van der Waals heterostructures further increases the design space for functional devices with on-demand properties. 2D materials have superior electrical conductivity and a high surface area, which are the most essential properties in the field of energy storage (Qasem et al., 2021). Graphene is a conductive framework used in lithium-ion and post-lithium batteries to facilitate electron transport and allow the electrode material to expand and contract in volume. MXenes possess pseudocapacitive charge-storage chemistry and the ability to incorporate various ions, making them the top choice for high-power supercapacitors and high-rate battery electrodes (Bhat et al., 2021). Their electrochemical characteristics are determined by their tunable surface termination groups (-O, -OH, - F), thereby optimizing ion accessibility and storage capacity. To overcome the challenges posed by silicon-based scaled device packing, 2D materials offer solutions (Zhu et al., 2021b). The high mobility of graphene makes it suitable for high-frequency transistors and as a flexible, transparent electrode for displays and photovoltaics. Ultra-scaled low-power transistors and vivid photodetectors based on Semiconducting TMDs, by virtue of their thinness and insensitivity to short-circuit effects, are being studied. Moreover, the atomically smooth 2D material surface, along with the lack of dangling bonds, makes 2D materials helpful in developing heterostructures with sharp edges, enabling the design of new devices such as tunneling field-effect transistors (TFETs) and resonant tunneling diodes (Ahmed et al., 2022). 2D materials have revolutionized biomedicine through their biocompatibility, high surface area, and ease of surface functionalization (Saleh & Hassan, 2023). The fieldeffect transistor is made from graphene, allowing label-free detection of biomolecules in diagnostic biosensing. MXenes and functionalized graphene oxides can serve as superior nanocarriers for targeted drug delivery, photothermal therapy, and bioimaging, owing to their strong near-infrared absorption and ability to load therapeutic agents (Geng et al., 2022). Nonetheless, when applied to biomedicine, the translation must be complemented by a comprehensive study of their long-term biocompatibility and biodegradation characteristics to ensure their safety for clinical use. Despite tremendous advancements, issues such as large-scale, defect-free synthesis, precise control of the number of layers, and environmental stability over a long period remain. It is on this introduction that we move to greater detail on how graphene, MXenes, and other 2D materials are being developed to address these challenges and revolutionize technology in these critical areas, to build a more efficient, connected, and healthier future (Maleki et al., 2022). Literature Review The landscape of two-dimensional (2D) material studies has changed radically since the first isolation of graphene, with a multitude of materials with customizable properties emerging. This review summarizes recent research on the use of graphene, MXenes, and other 2D materials, with an emphasis on application-oriented development in energy storage, electronics, and biomedicine. 1182 Energy Storage: Alternative(s) to Conventional Electrodes One of the main reasons why 2D materials should be integrated into energy storage devices is the need to increase energy and power density (Akyildiz et al., 2020). Initial graphene research had already established its use as an additive and scaffold in lithium-ion batteries (LIBs). The study by Chang et al. (2021) demonstrated that silicon anodes wrapped with graphene alleviate pulverization to a considerable extent, thereby improving cyclability. Nevertheless, the inherent agglomeration of graphene sheets limits the full exploitation of surface area. This drawback has driven studies toward MXenes, which were initially reported by Gong et al. (2021). They are the best supercapacitors due to their metallic conductivity and hydrophilic property. Mishra et al. (2024) have identified the importance of the tunable surface chemistry of Ti3C2T in a comprehensive review. Directly controlled by MXene, achieved through a wide range of etching and delamination processes, is its pseudocapacitive behavior in acidic electrolytes, where it can reach capacitances higher than those of carbon-based materials. Recently, studies have also switched to MXene heterostructures. For example, Wang (2013) developed a MoS2/Ti3C2T heterostructure, in which MXene flakes prevent the reassembly of MoS2 and provide sample ion galleries, resulting in a significant increase in sodium-ion storage capacity and rate performance. Electronics: The Push of the Limits of the Moore Law In electronics, the literature shows an apparent trend from fundamental transport studies of graphene to the applied use of 2D semiconducting materials. Although the carrier mobility of graphene is well documented, it lacks a bandgap, which makes it unsuitable for all-logic transistors. This sparked significant interest in transition-metal dichalcogenides (TMDs), such as MoS2 and WSe2. This area was the first to be pioneered by Alzahrani (2022), who established a single-layer MoS2 transistor with a high on/off Ratio and short channel insensitivity. The existing literature is focused on the implementation of these materials in operational circuits and on new device concepts. A groundbreaking paper by Sepulveda (2018) presented a microprocessor entirely made of 2D MoS2 transistors, a milestone towards commercial feasibility. Moreover, the properties of 2D materials enable flexible, transparent electronics. Graphene touchscreen electrode and TMD wearable optoelectronics Biomedicine: A paradigm shift in theranostics One of the frontiers in the biomedical use of 2D materials is their large surface area and exceptional optical properties. Early biocompatibility issues with graphene oxide have been resolved by advanced surface functionalization with polymers such as polyethylene glycol (PEG). The article by Escudero et al. (2021) was a systematic review of PEGylated graphene oxide as a nanocarrier for chemotherapeutic drugs, highlighting its enhanced tumor accumulation driven by the increased permeability and retention (EPR) effect. MXenes have emerged as effective agents for photothermal therapy (PTT). A study by Ye et al. (2024) showed that Ti3C2T nanosheets converted photothermal energy with high efficiency (~45%) under near-infrared (NIR) light, which can be used to ablate cancer cells. There is also a rising trend in the literature of multifunctional "theranostic" platforms. Recently, Nb2C MXene composite that simultaneously serves as a photoacoustic imaging contrast agent and a PTT agent, and that loads and releases an anticancer drug based on the pH of the tumor microenvironment. 1183 To sum it up, the literature clearly shows that the original interest in graphene has evolved into an advanced science, with various 2D materials selected and designed for specific applications. The existing research paradigm emphasizes the design of heterostructures, scalable integration, and extensive knowledge of bio-interfacial interactions to transfer the remarkable potential of 2D materials from the laboratory to transformational technologies. Materials and Methods Production and Manufacturing of 2D Materials Graphene Oxide (GO) and Reduced GO (rGO) Natural graphite powder (Sigma-Aldrich, <20 μm) was processed to form graphene oxide using the Hummers method. In a nutshell, a 1g graphite was placed in a 9:1 solution of concentrated H2SO4/H3PO4 (120:13.3 mL). KMnO4 (6 g) was slowly added, and the mixture was cooled in an ice bath to prevent the temperature from exceeding 20 °C. The blend was then left to heat up to 50 °C in 12 hours. The reaction was quenched by pouring onto ice (135 mL) containing 30% H2O2 (1.5 mL). The formed GO was washed and centrifuged several times in 1 M HCl and deionized (DI) water until the supernatant reached pH 5-6. The GO was then dialyzed for 1 week and subsequently exfoliated by ultrasonication (400 W, 2 hours). Annealing at 800 C for 2 hrs in an ArH2 (95:5) atmosphere was used to reduce the rGO. MXene (Ti3C2T) the selective etching of the aluminum component in the MAX phase (Ti3AlC2, >98%, Y-Carbon Ltd.) was used to prepare MXene. To be more precise, 1 g of Ti3AlC2 powder was gradually added to a 20 mL solution of LiF dissolved in 9 M HCl, and the mixture was stirred for 24 hours at 35 °C. The multilayer MXene sediment was then harvested and centrifuged with DI water until the supernatant was neutral (pH 6). A 1-hour ultrasonic treatment in an ice bath under a N2 atmosphere disintegrated the sediment into a few-layered flake. The suspension was then centrifuged at 1500 rpm, and the 1-hour1-hour time was used to collect the supernatant containing singleand few-layer Ti3C2T nanosheets. Material Characterization Scanning electron microscopy (SEM, Zeiss Sigma 300) and transmission electron microscopy (TEM, JEOL JEM-2100F) were used to study the morphology and layer structure of the synthesized materials. The thickness and the lateral dimensions of the nanosheets were determined by atomic force microscopy (AFM, Bruker Dimension Icon) in tapping mode. X-ray diffraction (XRD; Bruker D8 Advance, Cu Ka radiation, λ = 1.5406 Å) was used to determine the crystal structure and identify the phase. Surface functionalities and chemical composition were determined using X-ray photoelectron spectroscopy (XPS, Thermo Scientific K-Alpha+) and Raman spectroscopy (Horiba LabRAM HR Evolution, 532 nm laser). The surface area of the particular surface was calculated from nitrogen physisorption at 77 K using the Brunauer-Emmett-Teller (BET) method (Micromeritics ASAP 2020). Biological and Electrochemical Testing Electrode Fabrication and Testing The electrode used for the supercapacitor tests was prepared by mixing the active material (rGO or MXene, 80 wt%), conductive carbon black (10 wt%), and a polyvinylidene fluoride (PVDF) binder (10 wt%) in N-methyl-2-pyrrolidone (NMP). The slurry was applied to carbon-coated aluminum foil and dried at 80 °C under vacuum for over 12 hours. The electrochemical behavior was assessed as cyclic 1184 voltammetry (CV) and galvanostatic charge-discharge (GCD) using a Biologic VMP3 potentio-stat in a three-electrode system with a 1 M, H2SO4 electrolytes. Biomedical Assays Cytocompatibility was evaluated using an MTT assay on L929 fibroblast cells, in accordance with ISO 10993-5. They were sterilized with UV light for 30 minutes before the cells were incubated with the materials for 24 and 48 hours. To charge the drugs, Doxorubicin (DOX) was added to the MXene dispersion (1mg/mL) at a weight Ratio of 2:1 (DOX: MXene), and the suspension was stirred in the dark for 24 hours. The drug complex (MXene: DOX) was obtained by centrifugation. Results and Discussion Characterization of the 2D Flakes 2D Flakes were synthesized and characterized using standard material characterization techniques. The successful exfoliation and synthesis of the 2D materials were established using a collection of characterization methods. The XRD pattern (Figure 1a) of the precursor Ti3AlC2 MAX phase reveals the typical (002) peak at about 9.5deg, but this shifts to lower angle of about 6.8deg of the etched and delaminated sample, which confirms the removal of the Al layer and an increase in the c-lattice parameter, which is in line with the successful synthesis of Ti3C2T. MXene (Feng et al., 2021). The loss of the graphite peak (002) at around 26 deg in GO and its new appearance of a broad peak at around 10 deg at the (001) plane validates its oxidation (Figure 1a, inset). Figure 1. Structural and Morphological Characterization The XRD pattern of Ti3AlC2 1185 MAX phase and the corresponding Ti3C2T were recorded (a). MXene. Inset: XRD of Graphite and GO. (b) The image of the accordion-like structure of etched multilayer MXene in the form of SEM. (c) AFM image and height profile of a single Ti3C2T flake on Si/SiO2. TEM picture of a crumpled, transparent sheet of rGO. The typical accordion-shaped morphology of the etched multilayer MXene was observed by SEM (Figure 1b), whereas TEM and AFM confirmed successful delamination into few-layer flakes. The thickness of the MXene flakes (Li et al., 2021) (Figure 1c) indicated that most of the flakes were 1.5 - 4 nm (2-5 single layers) in thickness. TEM images of rGO (Figure 1d) showed large, crumpled, and transparent sheets, indicating high exfoliation. XPS analysis of MXene revealed the presence of Ti, C, and O, as well as F-terminations from the etching process (See Supplementary Figure S1). Electrochemical Performance of Supercapacitor Applications The electrochemical energy storage characteristics of the prepared MXene and rGO were considered in a three-electrode aqueous system. The cyclic voltammetry (CV) curves of Ti3C2T. At scan rates of 5 to 200 mV/s, the MXene electrode (Figure 2a) exhibits almost rectangular shapes, indicating predominant capacitive behavior and small redox humps on the Ti surface, indicative of pseudo capacitance (Yang et al., 2021). Conversely, the rGO electrode was more rectangular and showed a doublelayer capacitive shape in the CV. Table 1. Electrochemical performance summary of MXene and rGO electrodes Material Specific Capacitance (F/g) at 2 mV/s Capacitance Retention at 100 mV/s Rate Capability (%) Ti₃C₂Tₓ MXene 325 ± 15 75% 92% rGO 210 ± 10 60% 85% The specific Capacitance was obtained by scaling the galvanostatic charge-discharge (GCD) curves (Figure 2b). The MXene electrode exhibited a high specific capacitance of 325 F/g at a scan rate of 2 mV/s, which was much higher than that of the rGO electrode (210 F/g). This is because MXene has better conductivity in metals and pseudocapacitive charge storage. In addition, the MXene electrode showed a high-rate capacity, retaining 75% of its capacity at a scan rate of 5 to 100 mV/the s, whereas the rGO retained only 60%. This is presumably due to increased ion transport kinetics in the hydrophilic MXene film interlayer galleries (Lee et al., 2022). 1186 Figure 2. Electrochemical Evaluation (a) CV curves of Ti3C2T MXene under varying scan rates. In Fig. (b), MXene and rGO were used with a current density of 1 A/g. (c) Retention of MXene and rGO electrodes over 10000 cycles of Capacitance at 10 A/g. Long-term cycling stability tests (Figure 2c) showed that the MXene electrode retained 88% of its original Capacitance after 10,000 cycles at a high current density of 10 A/g, indicating very high electrochemical stability. The rGO electrode was found to be even more stable (95% retention), as expected due to its very stable carbon-based structure (Zhong et al., 2022). Potential Cytocompatibility and Drug Delivery In biomedical applications, the cytocompatibility of the materials is a key consideration. The outcome of the MTT assay on the L929 fibroblast cells (Figure 3a) showed that both rGO and MXene had a concentration-dependent effect on cell viability. Both materials were highly viable at low concentrations (10 ug/mL), confirming their short-term cytocompatibility. But above these concentrations (100 ug/mL), viability was statistically reduced, especially in MXene (approximately 70% viability), possibly due to physical contact between sharp nanosheets and cell membranes or to the by-products of fluoride ions (Zhong et al., 2022). Table 2. Drug Loading and Release Profile of MXene@DOX Parameter Value Drug Loading Capacity 185% (wt DOX / wt MXene) Loading Efficiency 92.5% Cumulative Release (pH 7.4, 24 h) 22% Cumulative Release (pH 5.0, 24 h) 78% MXene loading and release characteristics were determined using Doxorubicin (DOX) as a Model chemotherapeutic. Table 2 demonstrates that Mxene has a very high drug-loading capacity of 185%, attributed to its large, functionalized surface area. Figure 3b: The pH-dependence of the drug release profile was high. When the body's pH was 7.4, the cumulative release was limited to 22% over 24 hours, reducing premature leakage into the blood. However, when the pH was set to acidic, mimicking the tumor microenvironment and endolysosomal compartments, the release at pH 5.0 increased to 78%. This can be explained by the fact that protonation of DOX and the 1187 weaker binding of DOX to the MXene surface at low pH enable targeted and regulated drug delivery to the tumor site (Zahra et al., 2022). Figure 3 Biomedical Assessment (a) Cell viability of L929 cells with varying concentrations of rGO and MXene at the end of 24h exposure time (p < 0.01). The profile of DOX release from the MXene@DOX complex under different conditions, specifically pH over 24 hours, is shown in (b). Conclusion This research conclusively shows that two-dimensional materials, including graphene, MXenes, and others, have significant potential to transform technology across key areas. Their outstanding characteristics and the merging of their unique abilities, such as high surface area, tunable surface chemistry, and exceptional electrical conductivity, make them ideally positioned for advanced applications. MXenes and graphene derivatives are the best electrode materials for energy storage, enabling supercapacitors with high power density and batteries with improved cyclability. In electronics, transition metal dichalcogenides exhibit semiconducting properties, and their metallic conductivity enables the continued advancement of Moore's law and the development of flexible, transparent electronics. Moreover, the biocompatibility and functionalizability of such materials offer numerous opportunities in biomedicine, including targeted drug delivery systems and highly sensitive biosensors. Nonetheless, there are no easy roads to commercializing discoveries in a laboratory for everyday use. One of the significant obstacles is achieving scalable, economical production of high-quality, defect-free materials. Their safe use, especially in medicine, also depends on a more thorough understanding of the long-term environmental effects and biological interactions to ensure secure implementation. Future studies should focus on optimizing production methods, creating new van der Waals heterostructures with customized properties, and conducting thorough toxicological studies. Overcoming these obstacles, the scientific community will be able to fully harness the transformative capabilities of 2D materials, finally ushering in a new era of effective energy solutions, a new stage of electronics, and an individualized approach to therapy.