Beyond Graphene: What Other 2D Materials Are Researchers Exploring?

Graphene transformed how scientists engineer matter at the nanoscale, proving that isolating a single atomic layer of carbon can unlock extraordinary mechanical strength, thermal transport and carrier mobility. Yet, despite its remarkable properties, graphene is not the only material shaping the future of nanotechnology.

Pristine graphene is a zero-bandgap semimetal, characterized by Dirac cones whose conduction and valence bands meet at the K-points of its Brillouin zone. This electronic structure enables high carrier mobility but also makes it difficult to switch the material completely OFF, limiting its direct application in conventional digital logic transistors.

Rather than being a limitation of nanotechnology, this has encouraged researchers to explore a much broader library of two-dimensional (2D) materials. These atomically thin structures exhibit strong in-plane bonding and, in many layered materials, weak out-of-plane van der Waals interactions. Their distinctive electronic, optical, mechanical and chemical properties create opportunities for engineering functionalities that are difficult to achieve in conventional bulk materials.

Here are seven important material families expanding the possibilities of nanotechnology beyond graphene.

1. Transition Metal Dichalcogenides (TMDs): Engineering the Electronic Bandgap

Transition metal dichalcogenides (TMDs) are among the most extensively investigated alternatives to graphene. They generally have the chemical formula MX₂, where M represents a transition metal, such as molybdenum or tungsten, and X represents a chalcogen, such as sulfur, selenium or tellurium. Common examples include molybdenum disulfide (MoS₂), tungsten disulfide (WS₂) and molybdenum diselenide (MoSe₂).

Unlike graphene, several TMDs possess intrinsic electronic bandgaps, making them suitable candidates for semiconductor applications. A particularly important example is MoS₂. In its semiconducting 2H-derived structure, bulk MoS₂ has an indirect bandgap, whereas its monolayer form exhibits a direct bandgap of approximately 1.8–1.9 eV. This transition significantly influences its optical response and makes monolayer MoS₂ valuable for investigating nanoscale transistors, photodetectors and optoelectronic devices.

However, crystal structure matters. MoS₂ can also exist in a metallic 1T phase, characterized by octahedral coordination rather than the trigonal-prismatic coordination of the semiconducting 2H phase. This difference in atomic arrangement changes its electronic properties and can be exploited in applications such as electrocatalysis and electrical contacts. Controlling phase composition, defects and layer thickness remains a major research challenge.

2. Hexagonal Boron Nitride (h-BN): The Atomic-Scale Insulator

While many 2D materials are investigated for their ability to conduct or switch electrical current, advanced electronic devices also require reliable insulating materials. Hexagonal boron nitride (h-BN), sometimes called white graphene because of its similar honeycomb lattice, provides an important solution.

It consists of alternating boron and nitrogen atoms arranged in a hexagonal structure. The polar B–N bonds produce a wide electronic bandgap of approximately 6 eV, making h-BN an excellent electrical insulator. It also exhibits high thermal stability, chemical resistance and an atomically smooth surface. In electronic device fabrication, h-BN serves as an insulating and encapsulation layer. Unlike conventional silicon dioxide (SiO₂) substrates, whose surface imperfections, hydroxyl groups and charge traps can introduce scattering and degrade carrier mobility, the basal plane of h-BN is free of dangling bonds and generally has a low density of surface charge traps. Consequently, it can provide a cleaner interface for graphene and other 2D semiconductors, helping preserve their intrinsic electronic properties. Its role in van der Waals heterostructures is equally important, where it can separate, protect and electrically isolate different atomically thin layers. Achieving large-area, defect-controlled h-BN growth and integrating it into existing semiconductor manufacturing processes remain important challenges.

3. MXenes: Conductive 2D Materials with Tunable Surface Chemistry

MXenes have emerged as an important family of 2D transition-metal carbides, nitrides and carbonitrides. Their high electrical conductivity, hydrophilic character and chemically tunable surfaces distinguish them from many other atomically thin materials. Their general chemical formula is Mₙ₊₁XₙTₓ, where M represents an early transition metal, X represents carbon and/or nitrogen, and Tₓ represents surface termination groups such as –O, –OH and –F. A widely studied example is Ti₃C₂Tₓ.

MXenes are commonly synthesized by selectively removing the A-layer from layered precursor compounds known as MAX phases. In these precursors, M represents an early transition metal, A typically represents an A-group element such as aluminum, silicon or gallium, and X represents carbon and/or nitrogen. For example, Ti₃C₂Tₓ can be produced from Ti₃AlC₂ by selectively etching its aluminum layers while retaining the titanium-carbon framework. Conventional synthesis routes often use hydrofluoric acid (HF), while alternative fluoride-based etchants, including LiF/HCl systems, are also widely investigated. The etching process introduces surface termination groups that strongly influence the resulting material’s properties.

Their combination of electrical conductivity and accessible surface sites makes MXenes valuable for energy storage research. In batteries and supercapacitors, their layered structures facilitate ion transport and provide electrochemically active surfaces. They are also being investigated for electromagnetic interference shielding, gas sensing, biosensing and membrane-based separation.

Despite these advantages, oxidation, surface termination variability and difficulties in achieving reproducible large-scale production remain significant barriers. Developing more stable compositions and safer, scalable synthesis methods is an important direction for MXene research.

4. Black Phosphorus and Phosphorene: A Direct Bandgap Across Different Thicknesses

Black phosphorus is a layered allotrope of phosphorus that can be exfoliated into atomically thin sheets known as phosphorene. Unlike the relatively flat honeycomb structures of graphene and h-BN, phosphorene has a puckered atomic arrangement that produces distinctive electronic and optical properties.

One of its most important characteristics is its thickness-dependent direct bandgap. Unlike MoS₂, whose direct-bandgap behavior emerges in the monolayer limit, black phosphorus retains a direct bandgap from its bulk form down to the monolayer. Its bandgap increases from approximately 0.3 eV in bulk black phosphorus to around 2.0 eV in the monolayer, although exact values depend on the measurement and calculation method. This broad tunable range allows phosphorene to interact with light across infrared and visible spectral regions, making it particularly relevant to broadband photodetectors, optical modulators and other optoelectronic devices. Its anisotropic structure also produces direction-dependent electrical and optical responses, providing another parameter for device engineering.

However, black phosphorus is highly sensitive to oxygen, moisture and light under ambient conditions. Oxidative degradation can alter its surface chemistry and electronic performance. Researchers are therefore investigating encapsulation, surface passivation and protective coatings to improve its stability and enable reliable device integration.

5. Borophene, Silicene and Other 2D Elemental Materials

The exploration of 2D materials has extended beyond carbon and phosphorus to other elements. This family includes borophene, silicene, germanene and antimonene, which are often discussed as elemental 2D materials or Xenes. Borophene consists of atomically thin boron structures and exhibits considerable structural diversity. Unlike graphene’s stable planar honeycomb lattice, borophene can adopt different atomic arrangements depending on growth conditions and substrate interactions. Its distinctive electronic properties and predicted mechanical characteristics have generated research interest in energy storage, catalysis and nanoscale electronics. However, its structural stability and substrate-dependent behavior complicate large-scale fabrication and practical integration.

Silicene, a two-dimensional form of silicon, is another material being investigated because of its potential relevance to silicon-based electronics. It has a buckled honeycomb structure and exhibits theoretically interesting electronic properties. Unlike graphene, silicene is not readily obtained through conventional mechanical exfoliation of a stable layered bulk crystal. Instead, it is generally produced through epitaxial growth on suitable substrates, including silver (Ag(111)) and zirconium diboride (ZrB₂).

A major challenge is the interaction between silicene and its supporting substrate. Strong substrate-induced hybridization can substantially alter its electronic band structure, making it difficult to preserve its intrinsic properties. Transferring silicene onto insulating substrates without disrupting its atomic structure remains a significant obstacle. These materials demonstrate how changing atomic composition and arrangement can produce entirely different electronic structures and functional properties.

6. Two-Dimensional Metal-Organic Frameworks (2D MOFs): Designing Porous Nanostructures

Two-dimensional metal-organic frameworks (2D MOFs) represent another developing category of nanomaterials. They consist of metal-containing nodes connected by organic ligands, forming extended network structures with tunable chemical compositions and porous architectures. Their structural versatility allows researchers to modify pore dimensions, metal centers and organic linkers to control interactions with specific molecules and ions. These characteristics make 2D MOFs relevant to gas adsorption, molecular separation, heterogeneous catalysis and chemical sensing.

Unlike dense inorganic 2D crystals, their porous structures can provide accessible sites for molecular interactions. Certain compositions are also being investigated for electrochemical energy storage and electronic applications. However, their electrical conductivity can vary considerably depending on the metal nodes, organic linkers and degree of electronic coupling within the framework. The primary research challenge is balancing high porosity and accessible surface area with sufficient electrical conductivity, structural stability and scalable synthesis.

7. Beyond Individual Materials: The Rise of 2D Heterostructures

The future of 2D materials research is not limited to discovering new individual materials. Researchers are increasingly combining different atomically thin materials to create structures known as van der Waals heterostructures. These structures are formed by stacking different 2D materials, allowing complementary properties to be integrated within a single architecture. For example, graphene can provide electrical conductivity, h-BN can function as an insulating layer, and MoS₂ can provide semiconducting functionality.

The resulting interfaces can exhibit electronic and optical behavior that differs from that of the individual components. Furthermore, the relative rotational alignment between stacked layers can generate moiré patterns, which modify electronic band structures and can produce unusual quantum phenomena.

These engineered systems are being investigated for advanced transistors, optoelectronics, quantum devices and other next-generation electronic architectures. Precise control over layer alignment, interface cleanliness and large-area fabrication remains essential for translating laboratory demonstrations into practical devices.

The Challenges Behind the Technology

Despite their remarkable properties, 2D materials face several challenges before widespread industrial adoption becomes practical. Producing high-quality materials at laboratory scale is one achievement; manufacturing them consistently over large areas is another. Techniques such as mechanical exfoliation, liquid-phase exfoliation, chemical vapor deposition and chemical synthesis offer different advantages, but controlling layer thickness, crystal quality, defect density and production yield remains challenging.

Environmental stability is another major consideration. Materials such as black phosphorus and certain MXenes can undergo degradation under ambient conditions, affecting their long-term performance. Similarly, defects, grain boundaries, surface contamination and variations in chemical composition can influence electrical, optical and mechanical properties.

Characterization is equally important. Techniques such as atomic force microscopy (AFM), transmission electron microscopy (TEM), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) help researchers evaluate thickness, morphology, crystallinity, chemical composition and structural quality. A combination of complementary techniques is often necessary because no single characterization method can establish every property required for reliable material assessment.

For industrial applications, researchers must also consider manufacturing costs, reproducibility, device integration, environmental impact and long-term reliability. Moving from promising laboratory demonstrations to commercially viable technologies will require addressing these interconnected challenges.

Conclusion: A New Era of Materials Beyond Graphene

Graphene opened an important chapter in nanotechnology, but the evolution of 2D materials demonstrates that the possibilities of atomic-scale engineering extend far beyond a single material. TMDs offer semiconducting properties, h-BN provides an atomically thin insulating platform, MXenes bring conductive and chemically tunable surfaces, while phosphorene and other elemental materials introduce distinctive electronic and optical behavior. Meanwhile, 2D MOFs and van der Waals heterostructures are expanding the possibilities for designing materials with application-specific functionalities.

The real significance of these developments lies in the ability to select, combine and engineer materials according to the requirements of a particular technology. From next-generation electronics and energy storage to sensors, catalysis and environmental applications, 2D materials are creating new opportunities across multiple areas of science and engineering.

The future of nanotechnology may not be defined by finding a single material that does everything, but by understanding how different materials can work together to achieve what individual materials cannot.

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